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Study Design. Retrospective cohort study. Objective. To investigate the impact of age on the incidence of vascular complications in patients undergoing anterior lumbar approach surgery. Background. Anterior approach lumbar spinal surgery may facilitate the use of intervertebral devices with larger endplate coverage and increased lordosis. Despite the advantages of this approach, risks related to vascular injury in older patients have been described in the literature. Patients and Methods. In total, 751 consecutive patients with degenerative spinal pathology who underwent stand-alone anterior lumbar interbody fusion (ALIF), ALIF combined with posterior fusion and/or instrumentation (360), total disc replacement, or hybrid procedures (ALIF and total disc replacement) were included. Data collected included general patient descriptive data, surgery details, intraoperative vascular injury, and postoperative vascular complications (deep vein thrombosis and/or pulmonary embolism). Rates of vascular complications were compared across age groups. In addition, the mean age of patients was compared between those with versus without vascular complications. Results. Overall mean age was 50.4 years (range: 20--83 yr). The mean estimated blood loss was 91.3 mL (range: 10--2800 mL). A total of 15 patients, 2.0%, had vascular complications. There were 10 cases (1.3%) of intraoperative injury to iliac arteries or iliolumbar veins (mean blood loss was 721 mL, and all were repaired intraoperatively). Postoperatively, 6 patients (0.8%) developed deep vein thrombosis and/or pulmonary embolism (one patient had both). With respect to age, there were no significant differences in rates of intraoperative, postoperative, or combined vascular complication rates across the age group (P > 0.38). In addition, there were no statistically significant differences in the mean ages of patients with versus those without vascular complications (P > 0.17). Conclusion. Overall incidence of vascular complications was 2.0%. No relationship between vascular complications and age was demonstrated. These data suggest that increased age may not necessarily be an absolute contraindication for anterior lumbar approach surgery. [ABSTRACT FROM AUTHOR]

Study Design. Retrospective cohort study. Background. Cervical TDR has gained acceptance as an alternative to anterior cervical discectomy and fusion in appropriately selected patients. There have been concerns over device safety, one measure of which is subsequent surgery related to device problems. Patients and Methods. A consecutive series of 1626 patients undergoing cervical TDR from 2003 to June 2021 were included, consisting of TDRs up to 3 levels and hybrids (TDR and fusion). TDR removal or revision surgeries and reasons for these surgeries, procedures performed, and duration from index procedure were recorded. Data were analyzed to determine the removal/revision rate and factors possibly related to these events. Results. There were 24 removals/revisions (1.48%) in the 1626 patients. Removal was performed in 23 cases (1.41%) and revision in 1 (0.06%). Among removal cases, anterior cervical discectomy and fusion was performed in 18 and TDR was replaced with another TDR in 5. Removals with fusion included 5 cases of osteolysis with/without Cutibacterium acnes, 4 device displacement/migration, 4 posterior spinal pathology, and one for each of the following: metal allergy, approach-related complications, malpositioning, subsidence, and hypermobility. The revision involved TDR repositioning 3 days after index surgery. There were 66 patients for whom a minimum of 10-year followup was confirmed, and none had removal/revision surgery 10 or more years after index surgery. There was no relationship between the occurrence of removal/revision and age, sex, body mass index, or physician experience (learning curve). The removal/revision rate was significantly higher in FDA trials versus postapproval (4.1% vs. 1.3%, P < 0.05). Conclusion. In this large consecutive series of patients, 1.48% of cervical TDRs were removed/revised. The low rate of removals/revisions over a long period of time provides support for the devices' safety. [ABSTRACT FROM AUTHOR]

Purpose: To analyze of the results of spine surgical treatment of athletes with lumbar degenerative disease and development of a surgical strategy based on the preoperative symptoms and radiological changes in the lumbar spine. Methods: For 114 athletes with lumbar degenerative disease were included in the present study. Four independent groups were studied: (1) microsurgical/endoscopic discectomy (n = 35); (2) PRP therapy in facet joints (n = 41); (3) total disc replacement (n = 11); (4) lumbar interbody fusion (n = 27). We evaluated postoperative clinical outcomes and preoperative radiological results. The average postoperative follow-up was 5 (3;6), 3.5 (3;5), 3 (2;4) and 4 (3;5) years, respectively. The analysis included an assessment of clinical outcomes (initial clinical symptoms, chronic pain syndrome level according to the VAS, quality of life according to the SF-36 questionnaire, degree of tolerance to physical activity according to the subjective Borg Rating of Perceived Exertion Scale) and radiological data (Dynamic Slip, Dynamic Segmental Angle, degenerative changes in the facet joint according to the Fujiwara classification and disc according to the Pfirrmann classification; changes in the diffusion coefficient using diffusion-weighted MRI). Results: The median and 25–75% quartiles timing of return to sports were 12.6 (10.2;14.1), 2.8 (2.4;3.7), 9 (6;12), and 14 (9;17) weeks, respectively. We examined the type of surgical treatment utilized, as well as the preoperative clinical symptoms, severity of degenerative changes in the intervertebral disc and facet joint, the timing of return to sports, the level of pain syndrome, the quality of life according to SF-36, and the degree of tolerance to physical activity. We then developed a surgical strategy based on individual preoperative neurological function and lumbar morphological changes. Conclusions: In this retrospective study, we report clinical results of four treatment options of lumbar spine degenerative disease in athletes. The use of developed patient selection criteria for the analyzed surgical techniques is aimed at minimizing return-to-play times. [ABSTRACT FROM AUTHOR]

Purpose: To describe modes of failure of cervical TDR, their related treatment strategies, and to describe a management strategy for the treatment of failed cervical TDR. Methods: This retrospective study was based on a consecutive series of 53 cervical TDR patients who underwent removal or revision surgery. Chart review was conducted to collect general descriptive data, reasons for TDR removal/revision, duration from index implantation to re-operation, and the subsequent procedure performed. Results: Among 53 patients, 36 underwent TDR removal and fusion, 16 underwent TDR removal and replacement with another TDR, and one patient's TDR was revised by repositioning. The mean duration from index surgery to removal/revision was 40.1 months (range: 3 days–222 months). In all cases, removal/revision surgery was completed without complication. The most common reason for removal was severe osteolysis, often involving C. acnes infection, and was primarily associated with one implant type. TDR removal and fusion were performed for subsidence, device migration, treatment of symptoms arising from posterior anatomy (facet joints, etc.), approach-related complications and pain. TDR replacement was feasible for hypermobility, metal allergy, implant locked in kyphosis, and oversized implant use. In one case of TDR malpositioning, the device was successfully revised into appropriate position. Conclusion: After cervical TDR failure, replacing a TDR with another implant can be feasible. Reasons for revision or removal after cervical TDR surgery include biomechanical failure, implant migration, surgeon or technical error, or biological reasons. The type of failure can help the surgeon create a strategy to address these complications. [ABSTRACT FROM AUTHOR]

The motion limitation after cervical discectomy and fusion alters the spine´s kinematics. Unphysiological strains may be the result and possible explanation for adjacent segment degeneration. Alterations to cervical kinematics due to cervical total disc replacement (TDR), especially two-level, are still under investigated. To investigate cervical motion including coupled motions after one-level and two-level TDR in the treated and also the adjacent segments. An in-vitro study using pure moment loading of human donor spines. Seven fresh frozen human cervical spine specimens (C4–T1, median age 46 with range 19–60 years, four female) were included in this study. Specimens were tested in the intact condition first, followed by one-level TDR at C5–6 which was subsequently extended one level further caudal (C5–7). Each specimen was quasistatically loaded with pure moments up to 1.5 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) in a universal spine tester for 3.5 cycles at 1 °/s. During the tests three dimensional motion tracking was performed for each vertebral body individually. From that, the primary and coupled ROM of each spinal level during the third full cycle of motion were evaluated. Nonparametric statistical analysis was performed using a Friedman-test and post hoc correction with Dunn-Bonferroni-tests (p<.05). Ethics approval was obtained in advance. In FE, one-level TDR (C5–6) moderately increased primary FE in all four segments, but only significantly at the cranial adjacent level C4–5. Additional TDR at C6–7 further increased the ROM at the target segment without much influence on the other levels. Increasing implant height at C6–7 partially counteracted the increased FE. Coupled motions were minimal in all test conditions at all levels. In LB, coupled AR was observed in all test conditions at all levels. One-level TDR decreased primary LB at the target segment C5–6 significantly, without much influence on the other levels. Extending TDR to C6–7 decreased ROM in the target segment but without gaining statistical significance. Increasing implant height at C6–7 further decreased primary LB at the target segment, still without significance. Notably, coupled AR was significantly decreased at the cranial adjacent segment C4–5 compared to the intact condition. In AR, coupled LB was observed in all test conditions at the levels C4–5, C5–6, and C6–7, while the transition level to the thoracic spine C7–T1 showed only little coupled LB. Both one-level and two-level TDR showed little influence on primary AR or coupled motions at any level. Only after increasing implant height at C6–7 was the motion of the caudally adjacent level C7–T1 significantly altered. Evaluating primary FE, LB, and AR together with the associated coupled motions revealed widespread influence of cervical TDR not only on the motion of the treated level but also at the adjacent segments. The influence of two-level TDR is more widespread and involves more levels than one-level TDR. The prevention of unphysiological strains due to altered kinematics after cervical fusion, which could possibly explain adjacent segment degeneration, were a driving factor in the development of TDR. These experimental findings suggest cervical TDR influences the whole cervical spine, not only the treated segment. The effect becomes more extensive, involving more levels and motion directions, after two-level than after one-level TDR. [ABSTRACT FROM AUTHOR]

Cervical total disc replacement (TDR) aims to maintain normal cervical kinematics after surgery. This study investigates the relation between shifted location of centre of rotation (COR) and subsequent surgical outcomes after multilevel cervical TDR (MCTDR) and identifies radiological parameter that corresponded to this change of COR after MCTDR. The study included a consecutive 24 patients treated with MCTDR following the diagnosis of multilevel cervical disc herniation or stenosis. Numeric Rating Scale (NRS), range of motion (ROM) at both C2-7 segment and TDR implanted levels, and location of COR at TDR level were evaluated at pre- and post-MCTDR. These parameters were compared between patients who experienced successful and unsuccessful pain relief. The inherent CORs relatively at ventro-cranial coordinates have demonstrated significant migrations to dorso-caudal location, more prominent shifts for the successful group, after MCTDR switch. The unsuccessful group showed markedly reduced C2-7 ROM and reduced angular improvement at C2-7 as well as MCTDR level in comparison with the successful group. Postoperative C2-7 ROM was related to postoperative COR along the X axis. The determinant for clinical success after MCTDR, other than mere preservation of the ROM both at C2-7 and TDR levels, was restoration of COR from ventro-cranial location close to normal coordinates by posterior and inferior shifts. The position of COR along the X axis after MCTDR was important factor to determine maintenance of C2-7 ROM. [ABSTRACT FROM AUTHOR]

In contrast to cervical discectomy and fusion, total disc replacement (TDR) aims at preserving the motion at the treated vertebral level. Spinal motion is commonly evaluated with the range of motion (ROM). However, more qualitative information about cervical kinematics before and after TDR is still lacking. The aim of this in vitro study was to investigate the influence of cervical TDR on ROM, instantaneous centers of rotation (ICR) and three-dimensional helical axes. An in vitro study with human spine specimens under pure moment loading was conducted to evaluate the kinematics of the intact cervical spine and compare it to cervical TDR. Six fresh frozen human cervical specimens (C4–5, median age 28 years, range 19–47 years, two female and four male) were biomechanically characterized in the intact state and after implantation of a cervical disc prosthesis (MOVE-C, NGMedical, Germany). To mimic in vivo conditions regarding temperature and humidity, water steam was used to create a warm and humid test environment with 37°C. Each specimen was quasistatically loaded with pure moments up to ±2.5 Nm in flexion/extension (FE), lateral bending (LB) and axial rotation (AR) in a universal spine tester for 3.5 cycles at 1 °/s. For each third cycle of motion the ROM was evaluated and an established method was used to determine the helical axis and COR and to project them into three planar X-rays. Statistical analysis was conducted using a Friedman-test and post hoc correction with Dunn-Bonferroni-tests (p<.05). After TDR, total ROM was increased in FE from 19.1° to 20.1°, decreased in LB from 14.6° to 12.6° and decreased in AR from 17.7° to 15.5°. No statistical differences between the primary ROM in the intact condition and ROM after TDR were detected. Coupled rotation between LB and AR were also maintained. The position and orientation of the helical axes after cervical TDR was in good agreement with the results of the intact specimens in all three motion directions. The ICR in FE and AR before and after TDR closely matched, while in LB the ICR after TDR were more caudal. The intact in vitro kinematics we found also resembled in vivo results of healthy individuals. The results of this in vitro study highlight the potential of artificial cervical disc implants to replicate the quantity as well as the quality of motion of the intact cervical spine. Physiological motion preservation was a driving factor in the development of cervical TDR. Our results demonstrate the potential of cervical TDR to replicate in vivo kinematics in all three motion directions. [ABSTRACT FROM AUTHOR]

The burden of disease regarding lumbar and cervical spine pain is a long-standing, pervasive problem within medicine that has yet to be resolved. Specifically, neck and back pain are associated with chronic pain, disability, and exorbitant health care use worldwide, which have only been exacerbated by the increase in overall life years and chronic disease. Traditionally, patients with significant pain and disability secondary to disease of either the cervical or lumbar spine are treated via fusion or discectomy. Although these interventions have proved curative in the short-term, numerous longitudinal studies evaluating the efficacy of traditional management have reported severe impairment of normal spinal range of motion, as well as postoperative complications, including neurologic injury, radiculopathy, osteolysis, subsidence, and infection, paired with less than desirable reoperation rates. Consequently, there is a call for innovation and improvement in the treatment of lumbar and cervical spine pain, which may be answered by a modern technique known as intervertebral disc arthroplasty, or total disc replacement (TDR). Thus, this review aims to describe the management strategy of TDR and to explore updated considerations for its use in practice, both to help guide clinical decision making. [ABSTRACT FROM AUTHOR]

BACKGROUND: The treatment of cervical spondylosis with total disc replacement can retain the range of motion of the cervical lesion segment and can effectively improve the symptoms of cervical spondylosis with sympathetic symptoms. OBJECTIVE: To investigate the clinical efficacy of total disc replacement for cervical spondylosis with sympathetic symptoms. METHODS: Retrospective analysis was made on 56 patients with cervical spondylosis with obvious sympathetic symptoms such as dizziness and headache who were operated on from December 2018 to December 2021. The sagittal parameters of the cervical spine before, 3 months after surgery and at the last followup were observed and compared, including cervical sympathetic symptom score and Japanese Orthopaedic Association Scores, operation segment angle, C2- C7 Cobb angle, C2-C7 sagittal vertical axis and T1 slope. The correlation between the changes in sympathetic symptoms and Japanese Orthopaedic Association Scores before and after surgery and the changes in cervical sagittal parameters before and after surgery was analyzed. RESULTS AND CONCLUSION: (1) All patients showed improvement in sympathetic symptoms after surgery, and the sympathetic symptom scores and Japanese Orthopaedic Association Scores were significantly improved at 3 months and at the last follow-up compared with those before surgery (P < 0.05), but Japanese Orthopaedic Association Scores did not show significant differences at the last follow-up compared with those at 3 months after surgery (P > 0.05). (2) The cervical sagittal parameters increased at 3 months and at the last follow-up compared with those before surgery, but not at the last follow-up compared with those at 3 months after surgery (P > 0.05). (3) The pre- and post-operative change values of sympathetic symptom scores significantly correlated with the preand post-operative change values of operation segment angle and C2-7 Cobb angle (P < 0.05). (4) The results indicate that total disc replacement has a good effect in the treatment of cervical spondylosis with sympathetic symptoms, which is conducive to restoring the sagittal parameters of the cervical spine and alleviating the sympathetic symptoms of patients. [ABSTRACT FROM AUTHOR]

Anterior cervical discectomy and fusion (ACDF) is the leading surgical treatment for cervical radiculopathy. However, ACDF surgery has been suggested for to accelerate the degeneration of the adjacent cervical discs, which causes so-called adjacent segment disease (ASD). Over the past 2 decades, total disc replacement (TDR)/cervical disc arthroplasty (CDA) has become an increasingly common method for treating degenerative cervical diseases. The rationale is that a synthetic disc prosthesis may preserve motion at the operated level, which is expected to lead to reduced stress on the other cervical levels and thus decrease the risk of developing ASD. However, since the method was first introduced in the early 2000s, the long-term outcome after it is still not completely understood. Our goal was to compare the long-term outcomes of TDR and ACDF procedures. Retrospective case-control study. All patients who underwent TDR due to degenerative cervical disease at Helsinki University Hospital between 2006 and 2012 (38 patients) and matched control patients who underwent ACDF during this period (76 patients) for degenerative disc disease. The primary outcome measure was the rate of reoperations and further cervical surgeries. Secondary outcome measures included neck symptoms (Neck Disability Index, or NDI), health-related quality of life (EQ-5D-3L), satisfaction with the surgery, radiological outcomes, and employment status. The medical records of all patients who underwent TDR due to degenerative cervical disease at Helsinki University Hospital between 2006 and 2012 and those of the matched control patients were analyzed retrospectively. Questionnaires were sent to all available patients at the end of the follow-up (median 14 years) to evaluate their employment status, levels of satisfaction with the surgery, current neck symptoms, and health-related quality of life. Radiological outcomes were evaluated from the cervical plain radiographs, which were taken either at the end of the follow-up as a part of the present study or earlier on for other clinical reasons, but at least 2 years after index surgery. The total rate of reoperations and further cervical surgeries during the follow-up of a median of 14 years was 7/38 (18%) in the TDR group and 6/76 (8%) in the ACDF group (p=.096, ns.). Total disc replacement patients were reoperated earlier, and the 5-year reoperation rate was significantly higher in the TDR group (11% vs 1.3%, p=.026). None of the TDR patients underwent further cervical surgery more than 6 years after index surgery, whereas 5/6 (83%) of the reoperated ACDF patients were reoperated after that time. There were no significant differences in the NDIs between the patient groups. The employment rate and health-related quality of life were slightly higher in the TDR group, but the differences were statistically nonsignificant. TDR was significantly better at maintaining the angular range of motion at the operated level, and the fusion rate was significantly lower among this group. There were no significant differences in the long-term outcomes of ACDF and TDR when measured by reoperation rates, employment status, NDI, EuroQoL, and satisfaction with surgery. Reoperation rate and, on the other hand, employment rate and health-related quality of life, were higher in the TDR group, but the differences were statistically nonsignificant. However, TDR patients were reoperated earlier, and the 5-year reoperation rate was significantly higher in the TDR group. Randomized long-term studies in which these methods are compared are needed to further clarify the differences between them. [ABSTRACT FROM AUTHOR]

Purpose: It is sometimes anticipated that patients with prior spine surgery will have a compromised outcome from future procedures. The purpose of this study was to compare TDR outcomes in patients with prior lumbar spine surgery to those with no previous surgery. Methods: Post hoc analysis was performed on 5-year follow-up data collected prospectively in the multi-centre FDA-regulated trial for the activL® Artificial Disc which involved 376 patients treated for single-level symptomatic disc degeneration. Clinical outcome measures included the Oswestry Disability Index (ODI), visual analog scales (VAS) assessing back and leg pain, SF-36, adverse events, and re-operations. Radiographic outcomes included flexion/extension range of motion (ROM) and translation of the operated segment. Patients were divided into two groups: Prior Lumbar Surgery (PLS, n = 92) and No Prior Lumbar Surgery (NPLS, n = 284). Results: Baseline demographics were similar in the two groups. ODI, VAS, and SF-36 Physical Component Scale scores improved significantly (p < 0.05) from baseline in both groups with improvements maintained through 5-year post-TDR with no significant differences between groups. There were no statistically significant differences in rates of serious device-related events, procedure-related events, or re-operations. While ROM was significantly less prior to TDR surgery in the PLS group, there was no significant difference in ROM at post-operative points. Conclusion: Prior lumbar spine surgery was not associated with compromised outcomes following TDR. These results are in line with reports from earlier studies with shorter follow-up, finding that non-destabilizing prior surgery is not a contra-indication for TDR provided that selection criteria are met. Level of Evidence I: Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding. [ABSTRACT FROM AUTHOR]

Background: Hybrid construction (HC) may be an ideal surgical strategy than noncontinuous total disc replacement (TDR) and noncontinuous anterior cervical discectomy and fusion (ACDF) in the treatment of noncontinuous cervical spondylopathy. However, there is still no consensus on the segmental selection for ACDF or TDR in HC. The study aims to analyse the effects of different segment selection of TDR and ACDF on cervical biomechanical characteristics after HC surgery. Methods: Twelve FEMs of C2–C7 were constructed based on CT images of 12 mild cervical spondylopathy volunteers. Two kinds of HC were introduced in our study: Fusion-arthroplasty group (Group 1), upper-level (C3/4) ACDF, and lower-level TDR (C5/6); Arthroplasty-fusion group (Group 2), upper-level (C3/4) TDR and lower-level ACDF (C5/6). The follow-load technique was simulated by applying an axial initial load of 73.6 N through the motion centre of FEM. A bending moment of 1.0 Nm was applied to the centre of C2 in all FEMs. Statistical analysis was carried out by SPSS 26.0. The significance threshold was 5% (P < 0.05). Results: In the comparison of ROMs between Group 1 and Group 2, the ROM in extension (P = 0.016), and lateral bending (P = 0.038) of C4/5 were significantly higher in Group 1 group. The average intervertebral disc pressures at C2/3 in all directions were significantly higher in Group 1 than those in Group 2 (P < 0.005). The average contact forces in facet joints of C2/3 (P = 0.007) were significantly more than that in Group 2; however, the average contact forces in facet joints of C6/7 (P < 0.001) in Group 1 group were significantly less than that in Group 2. Conclusions: Arthroplasty-fusion is preferred for intervertebral disc degeneration in adjacent upper segments. Fusion-arthroplasty is preferred for patients with lower intervertebral disc degeneration or lower posterior column degeneration. Trial registration: This research was registered in Chinese Clinical Trial Registry (ChiCTR1900020513). [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to investigate reasons and their frequency for why spine surgeons subspecializing in total disc replacement (TDR) performed lumbar fusion rather than TDR.Methods: The study was based on a consecutive series of 515 patients undergoing lumbar TDR or fusion during a 5-year period by three surgeons specializing in TDR. For each fusion patient, the reason for not performing TDR was recorded.Results: TDR was performed in 65.4% (n = 337) of patients and the remaining 34.6% (n = 178) underwent anterior lumbar interbody fusion (ALIF ± posterior instrumentation). Of the 178 fusion patients, the most common reason for fusion was combined factors related to severe degenerative changes (n = 59, 11.5% of the study population). The second most common reason was > Grade 1 spondylolisthesis (n = 32, 6.2%), followed by insurance non-coverage (n = 24, 4.7%), and osteopenia/osteoporosis (n = 13, 2.5%). Fusion patients were significantly older than TDR patients (52.5 vs. 41.6 years; p < 0.01). There was no significant difference with respect to gender (41.2% female vs. 43.8% female, p > 0.05) or the percentage of patients with single-level surgery (61.2% vs. 56.7%, p > 0.05).Conclusion: The most common reason for not performing lumbar TDR was related to anatomic factors that may compromise stability of the operated segment and/or TDR functionality. The older age of fusion patients may be related to these factors. This study found that many patients are appropriate candidates for lumbar TDR. However, even among TDR subspecialists, fusion is preferred when there are factors that cannot be addressed with TDR and/or may compromise implant functionality. [ABSTRACT FROM AUTHOR]

Cervical disc replacement is an alternative option to an anterior cervical discectomy and fusion for cervical spine degenerative disease. We present the first reported case of a progressively worsening symptomatic spinal cord compression secondary to migration of the nucleus from a Mobi-C total disc replacement. [ABSTRACT FROM AUTHOR]

Introduction: The correlation between cervical alignment and clinical outcome of total disc replacement (TDR) surgery is arguable. We believe that this conflict exists because the parameters that influence the biomechanics of the cervical spine are not well understood, specifically the effect of TDR on different cervical alignments. Methods: A validated osseo-ligamentous model from C2-C7 was used in this study. The C2-C7 Cobb angle of the base model was modified to represent: lordotic (−10°), straight (0°), and kyphotic (+10°) cervical alignment. The TDR surgery was simulated at the C5-C6 segment. The range of motion (ROM), intradiscal pressure, annular stresses, and facet loads were computed for all the models. Results: The ROM results demonstrated kyphotic alignment after TDR surgery to be the most mobile when compared to intact base model (41% higher in flexion–extension, 51% higher in lateral bending, and 27% higher in axial rotation) followed by straight and lordotic alignment, respectively. The annular stresses for the kyphotic alignment when compared to intact base model were higher at the index level (33% higher in flexion–extension and 48% higher in lateral bending) compared to other alignments. The lordotic model demonstrated higher facet contact forces at the index level (75% higher in extension than kyphotic alignment, 51% higher in lateral bending than kyphotic alignment, and 78% higher in axial rotation than kyphotic alignment) when compared among the three alignment models. Conclusion: Preoperative cervical alignment should be an integral part of surgical planning for TDR surgery as different cervical alignments may significantly alter the postsurgical outcomes. [ABSTRACT FROM AUTHOR]

• We present a numerical model of the mechanical behaviour of lumbar spine at healthy and after total disc replacement under low-energy impacts equivalent to physiological loads. • The mechanical behaviour of bone tissue is described using the poroelastic model (accounting for the interstitial biological fluid) within the method of movable cellular automata (discrete elements). • The results obtained with an artificial disc (with keel-type fixation) showed that the use of this type of endoprosthesis in healthy bone tissues allows to reproduce the function of the natural intervertebral disc and does not contribute to the development of neoplastic processes. • In the case of an artificial disc with osteoporosis of bone tissues, there is a zone with increased risk of tissue resorption and development of neoplastic processes in the area near the contact of the implant attachment. This circumstance can be compensated by increasing the loading level. Degenerative diseases of the spine have a negative impact on the quality of life of patients. This study presents the results of numerical modelling of the mechanical behaviour of the lumbar spine with patient-specific conditions at physiological loads. This paper aims to numerically study the influence of degenerative changes in the spine and the presence of an endoprosthesis on the creation of conditions for tissue regeneration. A numerical model of the mechanical behaviour of lumbar spine at healthy and after total disc replacement under low-energy impacts equivalent to physiological loads is presented. The model is based on the movable cellular automaton method (discrete elements), where the mechanical behaviour of bone tissue is described using the Biot poroelasticity accounting for the presence and transfer of interstitial biological fluid. The nutritional pathways of the intervertebral disc in cases of healthy and osteoporotic bone tissues were predicted based on the analysis of the simulation results according to the mechanobiological principles. Simulation of total disc replacement showed that osseointegration of the artificial disc plates occurs only in healthy bone tissue. With total disc replacement in a patient with osteoporosis, there is an area of increased risk of bone resorption in the near-contact area, approximately 1 mm wide, around the fixators. Dynamic loads may improve the osseointegration of the implant in pathological conditions of the bone tissue. The results obtained in the case of healthy spine and osteoporotic bone tissues correspond to the experimental data on biomechanics and possible methods of IVD regeneration from the position of mechanobiological principles. The results obtained with an artificial disc (with keel-type fixation) showed that the use of this type of endoprosthesis in healthy bone tissues allows to reproduce the function of the natural intervertebral disc and does not contribute to the development of neoplastic processes. In the case of an artificial disc with osteoporosis of bone tissues, there is a zone with increased risk of tissue resorption and development of neoplastic processes in the area near the contact of the implant attachment. This circumstance can be compensated by increasing the loading level. [ABSTRACT FROM AUTHOR]

Most ball-in-socket artificial lumbar disc implanted in the spine result in increased hypermobility of the operative level and overloading of the facet joint. A finite element model was established and validated for the lumbar spine (L1-L5). The structure of the Mobidisc prosthesis was modified, resulting in the development of two new intervertebral disc prostheses, Movcore and Mcopro. The prostheses were implanted into the L3/L4 level to simulate total disc replacement, and the biomechanical properties of the lumbar spine model were analyzed after the operation. Following the implantation of the prostheses, the mobility of operative level, peak stress of lumbar spine models, and peak stress of facet joint increased. The performance of mobility was found to be more similar between Movcore and Mobidisc. The mobility and facet joint peak stress of the Mcopro model decreased progressively with an increase in the Young's modulus of the artificial annulus during flexion, extension, and lateral bending. Among all the models, the Mcopro50 model had the mobility closest to the intact model. It showed a 3% decrease in flexion, equal range of motion in extension, a 9% increase in left lateral bending, a 7% increase in right lateral bending, and a 3% decrease in axial rotation. The feasibility of the new intervertebral disc prostheses, Movcore and Mcopro, has been established. The Mcopro prosthesis, which features an artificial annular structure, offers significant advantages in terms of reduced mobility of the operative level and peak stress of facet joint. • Material assignment to skeletal models based on grayscale values of the computed temography image. • Designed two new disc prostheses. • Biomechanical properties of prostheses of different structures. • Influence on prosthesis biomechanics of material properties of artificial annulus structure. [ABSTRACT FROM AUTHOR]

Purpose: Our study aimed to evaluate non-inferiority of ProDisc-C to anterior cervical discectomy and fusion (ACDF) in terms of clinical outcomes and incidence of adjacent segment disease (ASD) at 24-months post-surgery in Asian patients with symptomatic cervical disc disease (SCDD). Methods: This multicentre, prospective, randomized controlled trial was initiated after ethics committee approval at nine centres (China/Hong Kong/Korea/Singapore/Taiwan). Patients with single-level SCDD involving C3-C7-vertebral segments were randomized (2:1) into: group-A treated with ProDisc–C and group-B with ACDF. Assessments were conducted at baseline, 6-weeks, 3/6/12/18/24-months post-surgery and annually thereafter till 84-months. Primary endpoint was overall success at 24-months, defined as composite of: (1) ≥ 20% improvement in neck disability index (NDI); (2) maintained/improved neurologic parameters; (3) no implant removal/revision/re-operation at index level; and (4) no adverse/severe/life-threatening events. Results: Of 120 patients (80ProDisc–C,40ACDF), 76 and 37 were treated as per protocol (PP). Overall success (PP) was 76.5% in group-A and 81.8% in group-B at 24-months (p = 0.12), indicating no clear non-inferiority of ProDisc-C to ACDF. Secondary outcomes improved for both groups with no significant inter-group differences. Occurrence of ASD was higher in group-B with no significant between-group differences. Range of motion (ROM) was sustained with ProDisc–C but lost with ACDF at 24-months. Conclusion: Cervical TDR with ProDisc–C is feasible, safe, and effective for treatment of SCDD in Asians. No clear non-inferiority was demonstrated between ProDisc-C and ACDF. However, patients treated with ProDisc–C demonstrated significant improvement in NDI, neurologic success, pain scores, and 36-item-short-form survey, along with ROM preservation at 24-months. Enrolment difficulties resulted in inability to achieve pre-planned sample size to prove non-inferiority. Future Asian-focused, large-scale studies are needed to establish unbiased efficacy of ProDisc-C to ACDF. [ABSTRACT FROM AUTHOR]

Study Design: Prospective cohort study.Objective: The aim of this article is to compare the mid- to long-term patient-reported outcome measures (PROMs) between single-level total disc arthroplasty (TDA), multi-level TDA, and hybrid constructs (combination of TDA and anterior lumbar interbody fusion [ALIF] across multiple levels) for symptomatic degenerative disc disease (DDD).Summary Of Background Data: The treatment of single-level DDD is well documented using TDA. However, there is still a paucity of published evidence regarding long-term outcomes on multi-level TDA and hybrid constructs for the treatment of multi-level DDD, as well as lack of long-term comparisons regarding treatment of single-level DDD and multi-level DDD.Methods: A total of 950 patients underwent surgery for single-level or multi-level DDD between July 1998 and February 2012 with single-level TDA (n = 211), multi-level TDA (n = 122), or hybrid construct (n = 617). Visual Analog Score for the back (VAS-B) and leg (VAS-L) were recorded, along with the Oswestry Disability Index (ODI) and Roland Morris Disability Questionnaire (RMDQ).Results: All PROMs in all groups showed statistically and clinically significant improvements (P < 0.005) in pain and function that is well above the corresponding minimum clinically important difference (MCID) and exceeds literature thresholds for substantial clinical benefit (SCB). Unadjusted analyses show that there were no statistically significant differences in the change scores between the surgery groups for VAS back and leg pain, and RMDQ up to 8 years' follow-up. Adjusted analyses showed the ODI improvement score for the single group was 2.2 points better (95% confidence interval [CI]: 0.6-3.9, P = 0.009) than in the hybrid group. The RMDQ change score was better in the hybrid group than in the multi-level group by 1.1 points (95% CI: 0.4-1.9, P = 0.003) at 6 months and a further 0.4 point at 2 years (95% CI: 0.1-0.8, P = 0.011).Conclusion: In the setting of meticulous preoperative evaluation in establishing a precision diagnosis, clinically and statistically equivalent results can be achieved when treating symptomatic DDD through single-level TDA, multi-level TDA, and hybrid constructs. These results are sustained at mid- to long-term follow-up.Level of Evidence: 3. [ABSTRACT FROM AUTHOR]

Background Context: Cervical total disc arthroplasty (TDA) is an alternative procedure to anterior cervical discectomy and fusion that facilitates neural decompression while both preserving motion of the spinal unit and decreasing the risk for degenerative changes at adjacent segments. However, due to its more recent introduction in clinical practice and low complication rates, the modes by which TDA may fail remain to be described.Purpose: This study sought to identify the modes and frequencies of cervical TDA failure in order to propose a novel classification system.Study Design: Retrospective cohort and systematic review.Patient Sample: Patients who underwent single or two-level TDA for cervical radiculopathy or myelopathy at a single institution and in the literature of medium and large prospective studies.Outcome Measures: Cervical TDA failure, defined as subsequent surgical intervention at the index segment.Methods: This study retrospectively reviewed patients who underwent single or two-level TDA for cervical radiculopathy or myelopathy at a single institution to identify the potential implant failure modes. A systematic review and meta-analysis of prospective data in the literature was then performed to further supplement failure mode identification and to describe the rates at which the various failure types occurred. Statistical analysis included between-group comparisons of Non-Failed and Failed patients and frequencies of each failure type among Failed patients.Results: A retrospective review at our institution of 169 patients (201 levels) identified eight failures, for a failure rate of 4.7%. Additionally, seven patients were revised who had the primary surgery at an outside institution. The systematic review of 3976 patients (4525 levels) identified 165 (4.1%) additional failures. Using this data, six primary failure types were classified, with several subtypes. These include recurrent or persistent index-level stenosis (Type I); migration (Type II) presenting as gross extrusion (A) or endplate failure with subsidence/acute fracture (B); instability (Type III) due to mechanical loosening (A), septic loosening (B), or device fracture (C); device motion loss (Type IV) such as "locking" of the device in kyphosis; implantation error (Type V) due to malposition (A) or improper sizing (B); and wear (Type VI) either without osteolysis (A) or with wear-particle-induced osteolysis (B). Stenosis (Type I) was the most common mode of failure found both through retrospective review and in the literature.Conclusions: Cervical TDA fails through six primary mechanisms. While rates of certain failures requiring subsequent surgical intervention are low, it is possible that these complications may become more prevalent upon further longitudinal observation. Thus, future application and validation of this classification system is warranted to evaluate how failure frequencies change over time and with larger patient samples. [ABSTRACT FROM AUTHOR]

Introduction: Cervical total disc replacement (CTDR) is an alternative to anterior cervical discectomy and fusion for select patients that may preserve range of motion and reduce adjacent segment disease. Various CTDR prostheses are available; however, comparative data are limited. This study aimed to compare the short-term kinematic and radiological parameters of the M6-C, Mobi-C, and the CP-ESP prostheses. Methods: This retrospective cohort study included patients treated with CTDR between March 2005 and October 2020 at a single institution. Patients were included if their follow-up assessment included lateral erect and flexion/extension radiographs. The primary outcome assessed at 3-months postoperatively was range of motion, measured by the difference in functional spinal unit angle between flexion and extension. Results: A total of 131 CTDR levels (120 patients, 46.2 ± 10.1 years, 57% male) were included. Prostheses implanted included the M6-C (n = 52), Mobi-C (n = 54), and CP-ESP (n = 25). Range of motion varied significantly (8.2° ± 4.4° vs. 10.9° ± 4.7° vs. 6.1° ± 2.7°, P < 0.001). On post hoc analysis, the Mobi-C prosthesis demonstrated a significantly greater range of motion than either the M6-C prosthesis (P = 0.003) or CP-ESP (P < 0.001). Conclusion: Although the optimal range of motion for CTDR has not been established, short-term differences in the range of motion may guide the selection of CTDR prosthesis. Further studies with longer follow-up and consideration of clinical outcome measures are necessary. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of our meta-analyses is to find the most appropriate surgical technique treating lumbar degenerative disc disease (DDD). Spinal fusion is the conventional treatment for lumbar DDD. Total disc replacement (TDR) has been developed to avoid negative effects of fusions by preserving functionality. To our knowledge, there is no evaluation comparing meta-analytically the clinical results of three different surgical techniques with same inclusion and exclusion criteria for treating DDD. Methods: The surgical techniques TDR, anterior lumbar interbody fusion (ALIF) and circumferential fusion (CFF) are pairwise meta-analytically compared. Primary outcomes are pain measured by the Visual Analogue Scale (VAS) and function measured by the Oswestry Disability Index (ODI). Secondary outcomes are the mean number of complications per case (MNOC) at surgery and follow-up and the overall MNOC. Results: In our systematic search, we found finally six prospective studies with the minimum follow-up of two years: four randomized controlled trials and two cohort studies. In VAS and ODI, TDR is proved to be superior to ALIF and CCF (p < 0.05), whereat ALIF is more effective than CFF without statistical significance. CFF presents the best result in complications with the lowest overall MNOC (0.1), followed by TDR (1.2) and ALIF (1.5). Conclusion: According to our meta-analyses, we regard TDR to be the most appropriate surgical technique treating DDD, followed by ALIF. Further studies with a longer follow-up are needed using the same methodical approach to strengthen the VAS and ODI results and to explain the discrepant result to complications. [ABSTRACT FROM AUTHOR]

Background Context: Although highlighted in joint arthroplasty studies, long-term outcomes between differing biomaterial composites, such as metal-on-metal (MoM) and metal-on-plastic (MoP) in anterior cervical disc replacement (ACDR) have not been thoroughly investigated.Purpose: The purpose of this study was to evaluate the patient-reported clinical outcomes, overall reoperation rates, complications, and rates of ASD of MoM versus MoP artificial discs in two-level ACDR for the treatment of cervical DDD.Study Design/setting: Meta-analysis and systematic review.Patient Sample: Nine hundred eighty patients (442 MoM, 538 MoP) across seven studies.Outcome Measures: Patient reported clinical outcomes (NDI, VAS-n, VAS-a), overall reoperation rates, complications, and rates of ASD.Methods: A systematic search strategy of three electronic databases (PubMed, CINAHL Plus, and SCOPUS) was conducted utilizing terms related to two-level ACDR. All studies included had a sample size of >10 patients, had a minimum 5-year follow-up, and reported data on adjacent segment disease. Cadaver studies, non-English manuscripts, articles with less than 5-year follow-up and studies in which only single-level ACDR was investigated were excluded. A total of seven studies were included in this analysis. Studies were analyzed for demographic data, clinical outcome scores (NDI, VAS-neck, and VAS-arm), overall reoperation rates, complications, and rates of ASD. A random-effects model of meta-analysis was used for groups that were determined to be heterogenous and a fixed-effects model was utilized for groups that were not. An overlap of 95% confidence intervals suggests no statistically significant difference at the p<.05 level.Results: Seven studies were included with data on 980 patients (442 MoM, 538 MoP). The study population was 52.84% female, with a mean age of 48.01 years, and a mean follow-up of 85.66 months. The mean improvement in NDI was 34.42 (95% CI, 32.49-36.36) and 29.72 (95% CI, 27.15-32.29) for the MoM and MoP groups, respectively. The mean improvement in VAS-neck was 11.20 (95% CI, 10.69-11.70) and 8.78 (95% CI, 7.81-9.74) for the MoM and MoP groups, respectively. The mean improvement in VAS-arm was 10.73 (95% CI, 9.83-11.63) and 8.49 (95% CI, 7.59-9.39) for the MoM and MoP groups, respectively. 3.85% (95% CI, 2.40-6.10) of patients who underwent ACDR with a MoM implant required reoperation compared to 5.33% (95% CI, 3.68-7.65) of patients with a MoP implant. Heterotopic ossification and dysphagia were the most common complications in both groups. The MoM cohort showed a higher incidence of HO (72.62% vs. 21.07%), but a lower incidence of dysphagia (0.96% vs. 16.31%) compared to the MoP cohort. The MoM cohort had a larger proportion of patients with ASD who underwent subsequent surgery at an adjacent level (7.89% MoM versus 1.91% MoP).Conclusions: Our present meta-analysis suggests that the use of MoM artificial discs in two-level ACDR results in superior clinical outcome score improvement, but higher rates of ASD requiring secondary surgery compared to MoP discs after a follow-up period of 5 years or more. [ABSTRACT FROM AUTHOR]

Study Design: Micro-computed tomography- (micro-CT-) based finite element analysis of cadaveric human lumbar vertebrae virtually implanted with total disc arthroplasty (TDA) implants.Objective: 1) Assess the relationship between vertebral porosity and maximum levels of bone-tissue stress following TDA; 2) determine whether the implant's loading mode (axial compression versus sagittal bending) alters the relationship between vertebral porosity and bone-tissue stress.Summary Of Background Data: Implant subsidence may be related to the bone biomechanics in the underlying vertebral body, which are poorly understood. For example, it remains unclear how the stresses that develop in the supporting bone tissue depend on the implant's loading mode or on typical inter-individual variations in vertebral morphology.Methods: Data from micro-CT scans from twelve human lumbar vertebrae (8 male, 4 female; 51-89 years of age; bone volume fraction [BV/TV] = 0.060-0.145) were used to construct high-resolution finite element models (37 μm element edge length) comprising disc-vertebra-implant motion segments. Implants were loaded to 800 N of force in axial compression, flexion-, and extension-induced impingement. For comparison, the same net loads were applied via an intact disc without an implant. Linear regression was used to assess the relationship between BV/TV, loading mode, and the specimen-specific change in stress caused by implantation.Results: The increase in maximum bone-tissue stress caused by implantation depended on loading mode (p < 0.001), increasing more in bending-induced impingement than axial compression (for the same applied force). The change in maximum stress was significantly associated with BV/TV (p = 0.002): higher porosity vertebrae experienced a disproportionate increase in stress compared to lower porosity vertebrae. There was a significant interaction between loading mode and BV/TV (p = 0.002), indicating that loading mode altered the relationship between BV/TV and maximum bone-tissue stress.Conclusion: Typically-sized TDA implants disproportionately increase the bone-tissue stress in more porous vertebrae; this affect is accentuated when the implant impinges in sagittal bending.Level of Evidence: N/A. [ABSTRACT FROM AUTHOR]

To analyze the clinical and biomechanical outcome of professional athletes after lumbar total disk replacement, with a focus on restoration of the functional activity. This nonrandomized retrospective single-center study included 11 professional athletes who underwent lumbar disc replacement surgery using the prosthesis M6-L (Spinal Kinetics, Schaffhausen, Switzerland). The average postoperative follow-up was 3.18 ± 1.14 years. The following outcomes were evaluated: intensity of pain in the lumbar spine and lower limbs, Oswestry Disability Index, Short-Form 36, complications, time of return to previous sports activity, range of movement, degree of lumbar lordosis, degenerative changes of the adjacent levels, and degree of heterotopic ossification. The operated patients reported significant decrease of pain on visual analog scale (P < 0.001) as well as significant improvement of Oswestry Disability Index (P = 0.001) and Short-Form 36 (P < 0.001). For the duration of follow-up, the patients maintained segmental range of motion at L4-L5 (P = 0.04) and L5-S1 (P = 0.03) levels. There was also some statistically insignificant increase of global lumbar lordosis (P = 0.84). We did not identify any significant degeneration of the adjacent intervertebral disks (P > 0.05) or progression of the facet joint degenerative changes at the implantation level and in the adjacent segments (P > 0.05). One patient (9.1%) developed grade I heterotopic ossification 5 years after surgery and in 1 patient (9.1%), a lesion of superior hypogastric plexus was recorded. The average time of return to previous sports activity was 9.72 ± 3.03 weeks. Total lumbar disc replacement using M6-L prosthesis in professional athletes made it possible to achieve statistically significant reduction of pain and facilitated early return to normal sports activities. In our opinion, preservation of movement of the operated lumbar segment can help to reduce the mechanical stress with beneficial impact on the rate of degeneration of the adjacent level. [ABSTRACT FROM AUTHOR]

Study Design: The study examined and compared four artificial cervical disks using validated finite element models. Purpose: To compare and contrast the biomechanical behavior of four artificial cervical disks by determining the external (range of motion) and internal (facet force and intradiscal pressure) responses following cervical disc arthroplasty (CDA) and to elucidate any device design effects on cervical biomechanics. Overview of Literature: Despite CDA’s increasing popularity most studies compare the CDA procedure with anterior cervical discectomy and fusion. There is little comparative evaluation of different artificial disks and, therefore, little understanding of how varying disk designs may influence spinal biomechanics. Methods: A validated C2–T1 finite element model was subjected to flexion-extension. CDAs were simulated at the C5–C6 level with the Secure-C, Mobi-C, Prestige LP, and Prodisc C prosthetic disks. We used a hybrid loading protocol to apply sagittal moments. Normalized motions at the index and adjacent levels, and intradiscal pressures and facet column loads were also obtained. Results: The ranges of motion at the index level increased after CDA. The Mobi-C prosthesis demonstrated the highest amount of flexion, followed by the Secure-C, Prestige LP, and Prodisc C. The Secure-C demonstrated the highest amount of extension, followed by the Mobi-C, Prodisc C, and Prestige LP. The motion decreased at the rostral and caudal adjacent levels. Facet forces increased at the index level and decreased at the rostral and caudal adjacent levels following CDA. Intradiscal pressures decreased at the adjacent levels for the Mobi-C, Secure-C, and Prodisc C. Conversely, the use of the Prestige LP increased intradiscal pressure at both adjacent levels. Conclusions: While all artificial disks were useful in restoring the index level motion, the Secure-C and Mobi-C translating abilities allowed for lower intradiscal pressures at the adjacent segments and may be the driving mechanism for minimizing adjacent segment degenerative arthritic changes. The facet joint integrity should also be considered in the clinical decision-making process for CDA selection. [ABSTRACT FROM AUTHOR]

Objective: We aimed to evaluate reliability, radiological outcomes, and the impacts of anterior cervical hybrid construction on the adjacent segments for the multilevel cervical degenerative disc disease (mCDDD) and spondylotic spinal stenosis (SSS). Methods: A retrospective analysis was performed using data extracted from the medical files of 195 patients (105 males, 90 females; mean age: 47.7 years). From 2008 to 2018, these patients underwent anterior cervical hybrid construction for symptomatic contiguous at least 2-level cervical degenerative disc diseases and cervical spondylosis. Clinical and radiological data including Neck Disability Index (NDI), visual analogue scale (VAS), local cervical degenerative disk disease in adjacent segments on magnetic resonance imaging (MRI) views, and complications were reviewed. Results: The mean clinical and radiological follow-up was 45.2 months (range 24 to 102). Radiculopathy and/or myelopathy were the main clinical problems in all patients. The mean VAS scores of HC for arm pain were 7.4 ± 0.8 preoperatively; 2.8 ± 0.6, 1 month after surgery; 2.3 ± 0.6, 6 months after surgery; 1.8 ± 0.6, 12 month after surgery; and 1.6 ± 0.6, 24 months after surgery. The mean NDI scores (mean ± SD) of HC significantly improved after surgery (on admission, 57.2 ± 5.5%; 1 month after surgery, 27.35 ± 5.3%; 6 month after surgery, 21.43 ± 2.8%; 12 months after surgery, 21.9 ± 2.3%; 24 months after surgery, 20.6 ± 2.6%, p = 0.006). Hoarseness and dysphagia were the most common complications and osteophyte formation was the most frequent radiographic change. Conclusion: Anterior cervical hybrid construction appears to be an acceptable option in the management of multilevel cervical degenerative disc diseases and spondylotic spinal stenosis. [ABSTRACT FROM AUTHOR]

• This is the first reported explant analysis of a Mobi-C cervical disc. • It was shown that migration of the insert occurred, leading to compression of the spinal cord, pain and eventually a revision operation. • While they may provide more normal biomechanics, non-constrained designs, such as the Mobi-C, may also be associated with excessive migration of the insert in vivo. • In common with explanted metal-on-polymer joint replacements, the metal articulating surfaces of the disc became rougher while the polyethylene insert became smoother in vivo. Ex vivo analysis of artificial discs is essential to better understand their ability to replace degenerated intervertebral discs. The Mobi-C differs from some other contemporary disc designs in that it has a mobile polyethylene insert that is sandwiched between superior and inferior cobalt chromium endplates. While some studies claim the Mobi-C to have restored normal cervical spinal biomechanics, others have noted high levels of migration. Our objective was to contribute to this debate by, for the first time, analysing an explanted Mobi-C cervical disc which was removed due to worsening myelopathy at the nano and macro scales. Intraoperatively, the insert was found to have excessively migrated and it compressed the spinal cord. Roughness was measured as 0.016 ± 0.006 μm (Sa) and 0.055 ± 0.020 μm (Sa) for the superior and inferior plates, and 1.210 ± 0.154 μm (Sa) and 0.446 ± 0.083 μm (Sa) for the superior and inferior surfaces of the insert. Compared to unworn surfaces, the roughness increased for the superior and inferior plates and decreased for both surfaces of the insert. However, the only statistically significant change occurred on the articulating surface of the inferior plate (p = 0.04). At the nanoscale, valleys dominated the articulating surfaces. The superior plate had a burnished appearance whereas the inferior plate appeared matt. Impingement was observed on the endplates. The insert was severely damaged, burnished and had scratches. Additionally, subsurface whitening and internal cracking were observed on the insert. [ABSTRACT FROM AUTHOR]

Anterior cervical discectomy and fusion (ACDF) immobilizes surgical segments and can lead to the development of adjacent segment degeneration and adjacent segment disease. Thus, cervical total disc replacement (CTDR) has been developed with the aim to preserve the biomechanics of spine. However, heterotopic ossification (HO), a complication following CTDR, can reduce the segmental range of motion (ROM) and defects the motion-preservation benefit of CTDR. The pathological process of HO in CTDR remains unknown. HO has been suggested to be a self-defense mechanism in response to the non-physiological biomechanics of the cervical spine following CTDR. The current literature review is concerned with the association between the biomechanical factors and HO formation and the clinical significance of HO in CTDR. Endplate coverage, disc height, segmental angle, and center of rotation may be associated with the development of HO. The longer the follow-up, the higher the rate of ROM-limiting HO. Regardless of the loss of motion-preservation benefit of CTDR in patients with HO, CTDR confers patients with a motion-preservation period before the development of ROM-limiting HO. This may delay the development of adjacent segment degeneration compared with ACDF. Future clinical studies should explore the association between HO and changes in biomechanical factors of the cervical spine. [ABSTRACT FROM AUTHOR]

Background: The principles of choosing an appropriate implant height remain controversial in total cervical disc replacement (TDR). By performing an in vitro biomechanical study and exploring the biomechanical impact of implant height on facet joint and motion function, the study aimed to offer valid proposals regarding implant height selection during TDR. Methods: A total of 6 fresh-frozen male cadaveric cervical spines (C2–C7) with 5 mm intervertebral disc height at C5/6 level were enrolled in the study. Specimens with the intact condition and with different height artificial discs were tested. Facet joint pressures and range of motion under each condition were recorded using a specialized machine. Results: The artificial disc heights that were involved in this study were 5 mm, 6 mm, and 7 mm. The range of motion decreased along with the increment of implant height, while facet joint pressure showed an opposite trend. Specimens with a 5 mm implant height could provide a similar range of motion (11.8° vs. 12.2° in flexion-extension, 8.7° vs. 9.0° in rotation, 7.9° vs. 8.2° in lateral bending) and facet joint pressure (27.8 psi vs. 25.2 psi in flexion, 59.7 psi vs. 58.9 psi in extension, 24.0 psi vs. 22.7 psi in rotation, 32.0 psi vs. 28.8 psi in lateral bending) compared with intact specimens. Facet joint pressure of specimens with 6 mm implant height (≥ 1 mm in height) increased during flexion at the C5–6 segment (30.4 psi vs. 25.2 psi, P = 0.076). However, specimens with 7 mm implant height (≥ 2 mm in height) showed a significant reduction in motion (9.5° vs. 12.2° in flexion-extension, P < 0.001) and increment of facet joint pressure at C5–6 segment (44.6 psi vs. 25.2 psi in flexion, 90.3 psi vs. 58.9 psi in extension, P < 0.0001) and adjacent segments. Conclusions: This study suggested that an appropriate artificial disc height can achieve near-normal biomechanical properties and is recommended. We should be very cautious when using artificial discs ≥ 1 mm in height compared to normal. However, implants ≥ 2 mm in height compared to normal significantly increased the facet joint pressure and decreased the range of motion; therefore, it should not be used in clinical practice. [ABSTRACT FROM AUTHOR]

Background: The effectiveness of lumbar total disc replacement (TDR) with different prostheses for sagittal alignment has been reported previously. However, there are only few reports on Activ L TDR and no specific evidence regarding whether sagittal alignment affects the clinical outcomes. Methods: Eighty-seven patients who underwent mono- or bi-segmental lumbar TDR with Activ L were studied. The films of the upright anteroposterior and lateral spine in neutral, flexion, and extension positions were obtained before surgery and at 1 month and 1 and 3 years after surgery. The radiographic parameters such as lumbar lordosis (LL), index level lordosis (IL), pelvic incidence (PI), pelvic tilt (PT), segmental lordosis (SL), and sacral slope (SS) were measured based on the lateral upright radiographs. Clinical outcomes were evaluated using the Oswestry Disability Index (ODI) and visual analog scale (VAS) pre- and post-operatively. Results: Eighty-seven patients with complete radiographic data were available for a 3-year follow-up period. Of these, 66 received a single-level TDR, and 21 received a 2-level TDR. At 1 month, the mean LL was similar to the pre-operative data and then was significantly increased to 45.1° at 3 years. On average, the IL tended to significantly increase, while the mean SL at L–5 was increased from 16.5° pre-operatively to 21.0° at 3 years. The mean SL at L1–2, L2–3, L3–4, and L5–S1; PI; PT; and SS showed no obvious difference after 3 years. In contrast, VAS and ODI scores showed significant improvement after surgery. Conclusions: Activ L TDR showed a favorable effect on sagittal alignment, enhancing the IL while preserving the LL and SS. However, satisfactory clinical results for over a 3-year follow-up were not affected by sagittal alignment. [ABSTRACT FROM AUTHOR]

Background: Meta-analyses on the comparison between fusion and prosthesis in the treatment of cervical radiculopathy mainly analyse studies including mixed patient populations: patients with radiculopathy with and without myelopathy. The outcome for patients with myelopathy is different compared to those without. Furthermore, apart from decompression of the spinal cord, restriction of motion is one of the cornerstones of the surgical treatment of spondylotic myelopathy. From this point of view, the results for arthroplasty might be suboptimal for this category of patients. Comparing clinical outcome in patients exclusively suffering from radiculopathy is therefore a more valid method to compare the true clinical effect of the prosthesis to that of fusion surgery.Aim: The objective of this study was to compare clinical outcome of cervical arthroplasty (ACDA) to the clinical outcome of fusion (ACDF) after anterior cervical discectomy in patients exclusively suffering from radiculopathy, and to evaluate differences with mixed patient populations.Methods: A literature search was completed in PubMed, EMBASE, Web of Science, COCHRANE, CENTRAL and CINAHL using a sensitive search strategy. Studies were selected by predefined selection criteria (i.a.) patients exclusively suffering from cervical radiculopathy), and risk of bias was assessed using a validated Cochrane Checklist adjusted for this purpose. An additional overview of results was added from articles considering a mix of patients suffering from myelopathy with or without radiculopathy.Results: Eight studies were included that exclusively compared intervertebral devices in radiculopathy patients. Additionally, 29 articles concerning patients with myelopathy with or without radiculopathy were studied in a separate results table. All articles showed intermediate to high risk of bias. There was neither a difference in decrease in mean NDI score between the prosthesis (20.6 points) and the fusion (20.3 points) group, nor was there a clinically important difference in neck pain (VAS). Comparing these data to the mixed population data demonstrated comparable mean values, except for the 2-year follow-up NDI values in the prosthesis group: mixed group patients that received a prosthesis reported a mean NDI score of 15.6, indicating better clinical outcome than the radiculopathy patients that received a prosthesis though not reaching clinical importance.Conclusions: ACDF and ACDA are comparably effective in treating cervical radiculopathy due to a herniated disc in radiculopathy patients. Comparing the 8 radiculopathy with the 29 mixed population studies demonstrated that no clinically relevant differences were present in clinical outcome between the two types of patients. These slides can be retrieved under Electronic Supplementary Material. [ABSTRACT FROM AUTHOR]

Introduction: One important factor in evaluating the safety of an implant is the rate of subsequent surgery and the reasons for surgery, particularly those that are related to possible problems with the implant. The purpose of this study was to determine the overall re-operation rate (including revisions, removals, device-related, procedure-related, adjacent segment, and others) for a large consecutive series of cervical TDR patients beginning with the first case experience, using a single device at a single institution. Methods: Surgery records were reviewed to identify cervical TDR patients and those who underwent subsequent surgery. Cervical TDR cases involving ProDisc-C were identified, beginning with the first case performed in 2003 at a multisite spine specialty centre. Only patients who were at least 2 years post-operative were included, producing a consecutive series of 535 patients. There were 115 hybrids in the series (TDR at one level and fusion at an adjacent segment). Data collected included general demographics and level(s) operated. A surgery log through 12-31-18 was reviewed to identify re-operations occurring in the TDR patients. For each re-operation, the reason, duration from index surgery, and procedure were recorded. The mean duration from the index surgery to the search of the surgery log for re-operations was 78.3 months, range 24 to 181 months. Results: Re-operation occurred in 30 patients (5.6%). These included: 3 TDR removals and revision to anterior discectomy and fusion (1 for migration, 1 for subsidence, and 1 for spondylosis), 1 TDR repositioning, 21 secondary surgeries for adjacent segment degeneration (5 of which were adjacent to fusion levels in hybrid procedures), 1 wound infection, 1 hematoma, and 2 received stimulators for pain control. There were no re- operations for device failure. In cases of re-operation for adjacent segment degeneration, the mean duration between the index surgery and re-operation was 47.3 months. Conclusion: The re-operation rate was 5.6%. No surgeries were performed for device failure. These results support the safety of the TDR device. [ABSTRACT FROM AUTHOR]

Introduction: We investigated a new metric for assessing the quality of motion of the cervical segments over the arc of extension-to-flexion motion after cervical disc arthroplasty (CDA). We quantified: (1) the amount of motion contributed by individual spinal segments to the total cervical spine motion, termed segmental motion fraction, and its variation throughout the arc of extension-to-flexion motion and (2) how cervical disc arthroplasty using two distinct prosthesis designs may influence the segmental motion contributions. Materials and methods: We tested 16 human C3–T1 spine specimens under physiologic loads; first intact, after CDA at C5–C6, and then at C5–C6 and C6–C7. The M6-C (Orthofix, USA) and Mobi-C (Zimmer, USA) disc prostheses were used in eight specimens each. Results and conclusions: The designs of the cervical disc prostheses tested significantly influenced the variation in segmental motion fraction as the spine underwent motion between the endpoints of extension and flexion. While the mean segmental motion contribution to the total cervical motion was not influenced by prosthesis design, the way the motion took place between the extension and flexion endpoints was significantly influenced. The M6-C artificial disc restored physiologic motion quality such that implanted segments continued to function in harmony with other segments of the cervical spine as measured before arthroplasty. Conversely, the Mobi-C prosthesis, while maintaining average motion contributions similar to the pre-implantation values, demonstrated large deviations in motion contribution over the extension-to-flexion arc motion in ten of 16 implanted segments. Such non-physiologic implant kinematics could cause excessive prosthesis wear and motion and stress shielding at adjacent segments. These slides can be retrieved under Electronic Supplementary Material. [ABSTRACT FROM AUTHOR]

Purpose: The purpose was to investigate reasons and their frequency for why total disc replacement (TDR) specialty surgeons performed anterior cervical discectomy and fusion (ACDF) rather than TDR.Methods: A consecutive series of 464 patients undergoing cervical spine surgery during a 5-year period by three TDR specialty surgeons was reviewed. For each ACDF, the reason for not performing TDR was recorded.Results: TDR was performed in 76.7% of patients (n = 356) and ACDF in 23.3% (n = 108). The most common reason for ACDF versus TDR was anatomical (conditions that may not be adequately addressed with TDR and/or may interfere with device function), which occurred in 64 of 464 patients (13.79%). The second most common reason was insurance (denial/lack of coverage n = 17, 3.23%), and deformity/kyphosis not addressable with TDR was noted in 13 (2.80%). Pseudoarthrosis repair led to ACDF in three patients (0.65%), two did not receive TDR due to osteoporosis (0.43%), and in two others (0.43%) ACDF was undertaken due to high risk of heterotopic ossification. There was one case (0.22%) each of: nickel allergy, trauma with posterior element fracture, TDR removal, multiple prior cervical spine surgeries, concern about artifact on future imaging studies, benign osteoblastic bone, and limitation to adequate surgical approach for TDR. ACDF patients' mean age was significantly greater than TDR patients' (55.3 vs. 46.7 years; p < 0.01). TDR group had significantly more single-level procedures than ACDF (60.8% vs. 43.5%; p < 0.05).Conclusion: The most common reason for ACDF versus TDR was anatomy that may compromise segmental stability and/or TDR functionality. Older age and greater number of operated levels may be related to anatomical factors, primarily significant osteophytes and severely degenerated facets. These factors, as well as deformity/kyphosis, are more common in older patients and require multi-level treatment. This study found that many patients are good cervical TDR candidates; however, even among TDR specialists, ACDF may be preferred where it is prudent to not take undue risks. These slides can be retrieved under Electronic Supplementary Material. [ABSTRACT FROM AUTHOR]

• Data from two different in vitro test methods for the same evaluation subjects were compared. It was investigated whether spine simulators with real human cadavers (SSCs) and finite element models (FEMs) provide the same data exemplarily for range of motion (ROM) before and after insertion of motion-retaining devices. • Only fifty-nine percent of SSC meta-analyses show restored ROM after insertion of the device compared to the intact spinal segment. In FEM meta-analyses, ROM is restored in ninety percent. • Ten percent of ROM analyses show significantly different data between SSCs and FEMs. • With regard to the included studies, data generated by SSCs and FEMs cannot be used unrestricted as alternative and complementary data. • Our analysis provides a new approach to compare data from associated test methods. Range-of-motion (ROM) data generated by the in vitro test methods of spine simulators with cadavers (SSCs) and finite element models (FEMs) are used alternatively and complementarily for in vitro evaluations. Our purpose is to compare exemplary segmental ROM data from SSCs and FEMs before and after ball-and-socket total disc replacement (bsTDR) to determine whether the two test methods provide the same data for the same evaluation subjects. We performed 70 meta-analyses (MAs) and 20 additional comparative analyses based on data from 21 SSC studies used for 39 MAs and 16 FEM studies used for 31 MAs. Only fifty-nine percent (n = 23/39) of SSC MAs show a restored ROM after bsTDR, whereas in FEM MAs, the ROM is restored in ninety percent (n = 28/31). Among the analyses comparing data from the same spinal segments, motion directions and bsTDR, SSC and FEM data are significantly different in ten percent (n = 2/20). According to our results, data generated by SSCs and FEMs cannot be used as alternative and complementary data without restriction. The quality of the evaluation methods itself as well as potential technical reasons for the discrepant results were not our evaluation target. Further SSC and FEM data should be compared using the same approach. [ABSTRACT FROM AUTHOR]

Study Design: Meta-analysis.Objective: To evaluate the efficacy and safety of total disc replacement (TDR) and anterior cervical discectomy and fusion for treating cervical degenerative diseases.Summary Of Background Data: Anterior cervical discectomy and fusion (ACDF) has been the traditional gold standard surgery for cervical degenerative diseases.Methods: Clinical databases including PubMed, MEDLINE, Cochrane and Clinical Trials.gov were searched. Review Manager 5.1 software and Stata 11.1 were used to analyze clinical data. Dichotomous pooled results were reported as relative risk (RR) and its 95% confidence interval (CI). Endpoints included clinical success rate, NDI success rate, neurological success rate, incidence of adverse event, reoperation rate and patient satisfaction.Results: Eight clinical trials and fifteen papers with 1440 TDR patients and 1237 ACDF patients were included in this meta-analysis. The TDR group had a higher clinical success rate (RR, 1.26; 95% CI, 1.13-1.41; P < 0.001; I = 79%), NDI success rate (RR, 1.16; 95% CI, 1.06-1.26; P = 0.001; I = 77%), neurological success rate (RR, 1.06; 95% CI, 1.03-1.10; P = 0.0004; I = 58%), and secondary surgery rate p (RR, 1.06; 95% CI, 1.03-1.09; P < 0.001; I = 0%) but lower secondary surgery rate (RR, 0.44; 95% CI, 0.31-0.63; P < 0.00001; I = 43%) compared with the ACDF group. There was no significant difference in the adverse event rate between the TDR group and Athe CDF group (RR, 0.44; 95% CI, 0.31-0.63; P < 0.001; I = 43%).Conclusion: From the meta-analysis, we conclude that the efficacy and safety of TDA are equivalent or superior to ACDF. TDR is associated with a higher overall success rate, NDI success rate, neurological success rate, reoperation rate and satisfaction rate compared with ACDF group. No differences exist in the risk of adverse event between the two groups.Level Of Evidence: 3. [ABSTRACT FROM AUTHOR]

Context: Cervical radiculopathy and myelopathy is one of the most frequent ailments encountered by spine surgeon. Motion‑preserving surgeries in cervical spine is a standard of care due to its certain advantages such as biomechanical anatomical conformity, reduced chances of adjacent segment degeneration, and revision surgeries. While there is abundant data from some centers, data from developing countries are still limited. Aims: The aim was to study the clinico‑radiological outcome of single‑level and hybrid total disc replacement (TDR) with Spineart Baguera®‑C cervical prosthesis for cervical myeloradiculopathy. Settings and Design: Retrospective study. Materials and Methods: Retrospective analysis of the 29 consecutive patient undergoing single level TDR and hybrid fixation (i.e., TDR with anterior cervical discectomy and fusion) with Spineart Baguera®‑C cervical prosthesis for myeloradiculopathy from January 1, 2014 to December 31, 2017, was done. Radiological features and outcome were studied from data collected on Insta‑picture archiving and communication system. Statistical Analysis Used: SAS 9.4 was used for all computations. Results on continuous measurements were presented as mean and standard deviation (min‑max) and results on categorical measurements were presented as numbers (n) and percentages. Results: Twenty‑nine patients were included in the study. The mean age was 43.31 ± 9.04 years with 14 males and 15 females. The most common level of TDR was C5‑C6 (72.41%). The mean follow‑up duration was 3.14 years ± 1.13 years (2–5 years). The mean hospital stay was 4.93 ± 2.12 days. The mean neck disability index (NDI) at admission was 27.24 ± 7.66 which decreased to 6.41 ± 4.29 at final follow‑up. Conclusions: Two‑year data on treatment with Spineart Baguera®‑C cervical prosthesis shows significantly improved NDI, visual analog scale (arm) with maintenance of movement of the prosthesis. [ABSTRACT FROM AUTHOR]

BACKGROUND: At present, there are many surgical methods for the treatment of lumbar disc herniation, and the therapeutic effects have their own advantages. Although there are many meta-analyses to compare the therapeutic effects of the two surgical methods, there is no comparison of the therapeutic effects of several surgical methods. OBJECTIVE: To compare the differences of different surgical methods in the treatment of lumbar disc herniation by network meta-analysis. METHODS: PubMed, Embase, Cochrane Library, Ovid and CNKI were searched, and randomized controlled trials or retrospective studies on different surgical methods for the treatment of lumbar disc herniation were collected. According to the inclusion and exclusion criteria established in advance, the quality of included randomized controlled trials was evaluated, and the data were analyzed by STATA 15.0 software. RESULTS AND CONCLUSION: A total of 42 studies, 5 156 patients and 9 surgical treatments were included. Surgical treatments contain total disc replacement, lumbar disc fusion, standard open discectomy, microendoscopic discectomy, microdiscectomy, percutaneous endoscopic lumbar discectomy, chemonucleolysis, automatic percutaneous lumbar discectomy and percutaneous laser disc decompression. The results of network meta-analysis showed that (from best to worst): (1) There was no significant difference in leg pain relief, and the rank probability was percutaneous laser disc decompression > microendoscopic discectomy > percutaneous endoscopic lumbar discectomy > standard open discectomy > microdiscectomy > lumbar disc fusion > total disc replacement. (2) There was no significant difference in low back pain relief, and the rank probability was total disc replacement > lumbar disc fusion > microendoscopic discectomy > percutaneous endoscopic lumbar discectomy > microdiscectomy > percutaneous laser disc decompression > standard open discectomy. (3) There was no significant difference in Oswestry disability index scores, and the rank probability was microendoscopic discectomy > percutaneous endoscopic lumbar discectomy > standard open discectomy > microdiscectomy > total disc replacement > lumbar disc fusion. (4) There were some statistical differences in the success rate, and the rank probability was total disc replacement > lumbar disc fusion > microendoscopic discectomy > percutaneous endoscopic lumbar discectomy > standard open discectomy > percutaneous laser disc decompression > microdiscectomy > chemonucleolysis > automatic percutaneous lumbar discectomy. (5) There was no significant difference in reoperation rate, and the rank probability was total disc replacement > lumbar disc fusion > microdiscectomy > microendoscopic discectomy > standard open discectomy > percutaneous endoscopic lumbar discectomy > percutaneous laser disc decompression > chemonucleolysis > automatic percutaneous lumbar discectomy. (6) There were some statistical differences in incidence of complications, and the rank probability was percutaneous endoscopic lumbar discectomy > automatic percutaneous lumbar discectomy > standard open discectomy > microdiscectomy > percutaneous laser disc decompression > microendoscopic discectomy > total disc replacement > lumbar disc fusion > chemonucleolysis. Results suggested that microendoscopic discectomy and percutaneous endoscopic lumbar discectomy are effective in all aspects. Disc replacement and lumbar disc fusion are the best in success rate of operation. Chemonucleolysis is poor in success rate of operation, reoperation rate and complications rate. Percutaneous automatic discectomy is poor in success rate of operation and reoperation rate. [ABSTRACT FROM AUTHOR]

Study Design: Comparative study.Objective: The aim of this study was to compare cervical alignment among three-level total disc replacement (TDR), two prosthesis with one cage (2D1C), one prosthesis with two cages (1D2C), and anterior cervical discectomy and fusion (ACDF), then identify the importance of cervical balance of cervical spondylotic myelopathy (CSM).Summary Of Background Data: There were few long-term comparisons on cervical alignment and cervical balance among three-level TDR, 2D1C, 1D2C, and ACDF for CSM.Methods: Twenty-eight patients with TDR, 15 with 2D1C, 36 with 1D2C, and 32 cases with ACDF were included with a mean follow-up of 90.9 ± 8.9 months. C2-C7 cervical lordosis (CL), C2-C7 sagittal vertical axis (SVA), T1 slope (T1S) were measured on x-ray at preoperation, immediate postoperation, and final follow-up, as well as range of motion (ROM), upper/lower adjacent ROM (UROM/LROM), and adjacent segment degeneration (ASD); cervical balance was assessed by T1S minus CL (T1SCL; 20°). Clinical outcomes included neck disability index (NDI) and Japanese Orthopedic Association (JOA) score.Results: NDI and JOA improved (P < 0.01)at postoperation and final-visit with no difference among four groups. ROM decreased mostly in ACDF group, although with a comparable inter-group UROM/LROM and ASD. All groups gained equal CL-improvement at final-visit. SVA and T1S together with their change were of no differences among groups (P > 0.05). There was a correlation among alignment parameters and between CL and ROM. The inter-group capacity of balance maintaining and imbalance correction was comparable (P > 0.05). The change of T1SCL was not correlated to NDI and JOA (P > 0.05).Conclusion: Adjacent segments were seldom affected. Cervical alignment was equivalently rebuilt among TDR, 2D1C, 1D2C, and ACDF. It was not essential to pay excessive attention to balance.Level Of Evidence: 3. [ABSTRACT FROM AUTHOR]

Conventional surgical treatment of multilevel cervical disc disease is based on anterior cervical discectomy and fusion (ACDF). However, fusion alters the biomechanics of the spine, potentially resulting in accelerated adjacent segment degeneration. To improve clinical outcomes, hybrid surgery, combining cervical disc arthroplasty with fusion, has been developed. Cervical total disc replacement (TDR) has been shown to keep the motion of adjacent segment, and a dynamic cervical implant (DCI) was shown to provide cervical dynamic stability under nonfusion. However, curative and unwanted side effects of the new therapy options TDR and DCI for treating multilevel cervical degenerative disc disease are still unknown. This analysis is based on 88 patients treated for multilevel cervical degenerative disc disease with ACDF only (56 patients), DCI hybrid (17 patients), and TDR hybrid (15 patients) between June 2008 and November 2015. The mean follow-up was 19.5 months. Visual analog scale (VAS), Neck Disability Index, and quality-of-life measurements were assessed via questionnaires. The VAS scores decreased significantly in all 3 groups (P < 0.001), but the TDR group showed the greatest reduction in VAS score compared with ACDF and DCI (both P < 0.05). The overall range of motion (ROM) and the segmental ROM at the treated levels showed significant decreases in all 3 groups. Although there was no difference in the overall ROM at final follow-up among the operatively treated groups, the ROM of the treated segment was lowest in the ACDF group (P = 0.002). In terms of heterotopic ossification, patients undergoing TDR showed the best prognosis. These results indicate that both TDR hybrid and DCI hybrid are effective and safe procedures for the treatment of multilevel degenerative disc disease. However, there is no definitive evidence that DCI or TDR arthroplasty lead to better intermediate-term results than ACDF over an average observation time of 19.5 months. [ABSTRACT FROM AUTHOR]

Study Design: Retrospective design/spine clinic and tertiary referral hospital. Purpose: This study investigated the association between shifted location of center of rotation (COR) and subsequent surgical outcomes and identified radiological parameters that corresponded to COR change after multilevel cervical total disc replacement (MCTDR). Overview of Literature: Cervical total disc replacement (TDR) maintains normal cervical kinematics after surgery. However, there is a paucity of literature analyzing the relationship between radiological shifts of COR and subsequent clinical success, especially when it comes to the issue of MCTDR switch. Methods: This study included 24 consecutive patients treated with MCTDR following the diagnosis of multilevel cervical disc herniation or stenosis. Numeric rating scale, range of motion (ROM) at both C2-7 segment and TDR implanted levels, and location of COR at TDR level were evaluated pre- and post-MCTDR. These parameters were compared between patients who experienced successful and unsuccessful pain relief. Results: The inherent CORs relatively at ventrocranial coordinates demonstrated significant migrations to dorsocaudal location, more prominent shifts for the successful group, after MCTDR switch. The unsuccessful group showed markedly reduced C2-7 ROM and reduced angular improvement at C2-7 segment and MCTDR level compared with the successful group. Postoperative C2-7 ROM was related to postoperative COR along the x-axis. Conclusions: Aside from ROM preservation at both C2-7 and TDR levels, COR restoration from ventrocranial location close to normal coordinates by posterior and inferior shifts was marked as a clinical success after MCTDR. The COR position along the x-axis after MCTDR was an important factor to determine maintenance of C2-7 ROM. [ABSTRACT FROM AUTHOR]

Purpose: As yet, there are no studies describing a relationship between radiographic subsidence after lumbar total disc replacement (TDR) and patient symptoms. To investigate if subsidence, in terms of penetrated bone volume or angular rotation over time (ΔPBV and ΔAR), is related to clinical outcome. To assess if subsidence can be predicted by position implant asymmetry (IA) or relative size of the TDR, areal undersizing index (AUI) on direct post-operative radiographs.Methods: Retrospective cohort study consists of 209 consecutive patients with lumbar TDR for degenerative disc disease. A three-dimensional graphical representation of the implant in relation to the bony endplates was created on conventional radiographs. Consequently, the PBV, AR, IA and AUI were calculated, direct post-operative (DPO) and at last follow-up (LFU). For clinical evaluation, patients with substantial pain (VAS ≥ 50) and malfunction (ODI ≥ 40) were considered failures.Results: At a mean follow-up of 16.7 years, 152 patients (73%) were available for analysis. In 32 patients, revision by spinal fusion had been performed. Both ΔAR (4.33° vs. 1.83°, p = 0.019) and ΔPBV (1448.4 mm3 vs. 747.3 mm3, p = 0.003) were significantly higher in the failure-compared to the success-group. Using ROC curves, thresholds for symptomatic subsidence were defined as ΔPBV ≥ 829 mm3 or PBV-LFU ≥ 1223 mm3 [area under the curve (AUC) 0.723, p = 0.003 and 0.724, p = 0.005, respectively]. Associations between symptomatic subsidence and AUI-DPO ≥ 0.50 (AUC 0.750, p = 0.002) and AR-DPO ≥ 3.95° (AUC 0.690, p = 0.022) were found.Conclusion: Subsidence of a TDR is associated with a worse clinical outcome. The occurrence of subsidence is higher in case of incorrect placement or shape mismatch. [ABSTRACT FROM AUTHOR]

Purpose: To report clinical and radiographic outcomes, rate of complications and influence on spinal alignment on long-term follow-up (FU) of patients who underwent lumbar total disc arthroplasty (TDR), bringing some evidence to determine the profile of the most well-suited patients for TDR. Methods: A retrospective review of patients underwent TDR for low back pain from degenerative disc disease (DDD) resistant to conservative treatment was performed. Demographic features, surgical data, clinical and radiographic outcomes, complications and spinopelvic parameters were evaluated. Results: Thirty patients (32 TDR) were included with a mean FU of 164 ± 36.5 months. The clinical outcomes measured by visual analogue scale and Oswestry Disability Index showed a significant improvement between preoperative and 1-year FU (p < 0.01). No significant temporal variance has been identified between 1-year and long-term follow-up (p > 0.05). The surgical revision rate was 10%. The overall rate of complications was 20%. At final follow-up, the mobility of the prosthesis was preserved in 68.75% of the cases, and 73.3% of the patients were globally well aligned. Conclusion: The optimal surgical indication is crucial to achieve excellent clinical and radiological outcomes. According to the literature and to our experience, we underline the importance of a coronal deformity < 15° Cobb angle and a Roussouly type 1 or 2 as the profile of the most well-suited patient for TDR. Our long-term results confirm the existing evidence about efficacy and safety of TDR as a reliable option, in optimal surgery indication, to treat DDD. These slides can be retrieved under Electronic Supplementary Material. [ABSTRACT FROM AUTHOR]

Study Design: Retrospective cohort.Objective: Evaluate the safety profile of single- and multilevel cervical artificial disc replacement (ADR) performed in an outpatient setting.Summary Of Background Data: As healthcare costs rise, attempts are made to perform an increasing proportion of spine surgery in ambulatory surgery centers (ASCs). ASCs are more efficient, economically and functionally. Few studies have published on the safety profile of multilevel cervical ADR.Methods: We have performed an analysis of all consecutive cervical ADR surgeries that we performed in an ASC over a 9-month period, including multilevel and revision surgery. The pre-, intra-, and postoperative data recorded included age, sex, body mass index, tobacco use, and diabetes; level and procedure, operating room time, estimated blood loss (EBL), and complications; and discharge site, occurrence of reoperation, hospital admission, or any medical complication or infection over a 90-day period.Results: A total of 147 patients underwent 231 treated levels: 71 single-level, 76 multilevel: 69 two-level, 6 three-level, and 1 four-level. Average age was 50 ± 10 years; 71 women, 76 men. None of the patients had insulin-dependent diabetes, 4 were current smokers, and 16 were former smokers. Average body mass index was 26.8 ± 4.6 (range 18-40). Average total anesthesia time was 88 minutes (range 39-168 min). Average EBL was 15 mL (range 5-100 mL). Approximately 90.3% of patients were discharged directly home, 9.7% to an aftercare facility. In the 90-day postoperative period there were zero deaths and two hospital admissions (1.4%)-one for medical complication (0.7%) and one for a surgical site infection (0.7%).Conclusion: In this consecutive case series we performed 231 ADRs in 147 patients in the outpatient setting, including multilevel and revision procedures, with 2 minor postoperative complications resulting in hospital unplanned admissions within 90 days. We believe that these procedures are safe to perform in an ASC. An efficient surgical team and careful patient selection criteria are critical in making this possible.Level Of Evidence: 3. [ABSTRACT FROM AUTHOR]

Introduction: Dynamic stabilization of the spine has been performed since the 1990s with the double purpose of restoring spinal segmental stability and allowing residual movement at the operated level. When we take into account the different motion-preserving devices and the spinal areas where they are applied, we can identify three categories of spinal implants: anterior cervical, anterior lumbar, and posterior lumbar. However, as in all prosthetic procedures performed in orthopedic surgery, the life span of a joint replacement device is a central topic of discussion, and this is true also for spinal dynamic devices, being revision surgery a complex procedure in specific cases.Materials and Methods: We performed a literature review on the different dynamic spinal implants and the most common causes of failure, providing clinical cases as illustrative options for revision surgery.Results: The review of the literature showed a 11.3% to 22.6% revision rate in posterior lumbar dynamic systems, with a peak of 40.6% in case of adjacent segment disease. In lumbar TDRs, infection and severe dislocations are the most frequent causes of anterior revisions, while posterior pedicle screw fixation could be a suitable option in minimal subsidence or TDR displacement. An algorithm for the planning of revision surgery is proposed.Conclusions: Surgical revision of spinal dynamic implants could be a demanding surgery especially in anterior approaches. Anterior cervical revision remains globally safe, but careful preoperative evaluation of vessels and ureter are suggested to avoid intraoperative complications in the lumbar spine. In posterior revision, a proper sagittal alignment of the spine should be restored. These slides can be retrieved under Electronic Supplementary Material. [ABSTRACT FROM AUTHOR]

Study Design: Case series OBJECTIVE.: The aim of this study was to assess the patient-reported outcome measures (PROMs) and patient satisfaction of multilevel lumbar total disc arthroplasty (TDA) for symptomatic multilevel degenerative disc disease (MLDDD).Summary Of Background Data: TDA has been shown to be safe and effective for the treatment of symptomatic single level degenerative disc disease. There is minimal PROMs data on the mid- to long-term outcomes of multilevel TDA constructs.Methods: Prospectively collected PROMs were analyzed from patients receiving multilevel TDA for symptomatic MLDDD. Data were collected preoperatively and postoperatively at 3, 6, and 12 months, then yearly. PROMs included patient satisfaction, Visual Analog Score back and leg, Oswestry Disability Index, and Roland-Morris Disability Questionnaire.Results: One hundred twenty-two patients (77 men, 45 women) who had preoperative and at least 24-month follow-up data were included. The average age was 42 ± 8.2 years (range 21-61) and mean follow-up 7.8 years (range 2-10). The majority received two-level TDA, except two patients (1.6%) who received three-level TDA. The two- to three-level TDA's were at the levels L3-4, L4-5, and L5-S1, whereas most two levels (n = 110, 90.2%) were at L4-5 and L5-S1; the remainder (n = 10, 8.2%) being at L3-4 and L4-5. Implants used were Charité (DePuy Spine, Raynham, MA) in 119 patients (240 levels) and InMotion (DePuy Spine) in 3 patients (6 levels). Improvement in pain and disability scores were both clinically and statistically significant (P < 0.001), and this improvement was sustained in those patients over the course of their follow-up. Ninety-two percent of patients reported good or excellent satisfaction with treatment at final review.Conclusion: Multilevel TDA constructs for MLDDD demonstrate favorable and sustained clinical outcomes at mid- to long-term follow-up.Level Of Evidence: 4. [ABSTRACT FROM AUTHOR]

Study Design: A prospective, multicenter, randomized, controlled, investigational device exemption (IDE) noninferiority trial.Objective: The aim of this study was to compare the 5-year safety and effectiveness of the activL Artificial Disc with Control Total Disc Replacement (TDR) systems (ProDisc-L or Charité) in the treatment of patients with symptomatic single-level lumbar degenerative disc disease (DDD).Summary Of Background Data: The activL Artificial Disc received Food and Drug Administration approval in 2015 based on 2-year follow-up data.Methods: Eligible patients presented with symptomatic, single-level, lumbar DDD who failed ≥6 months of nonsurgical management. At entry, 324 patients were randomly allocated (2 : 1) to treatment with activL (n = 218) or Control (n = 106, including n = 65 ProDisc-L and n = 41 Charité) TDR. At 5-year follow up, a total of 261 patients (176 activL patients and 85 Control patients) were available for analysis.Results: The primary composite endpoint at 5 years for activL patients was noninferior to Control TDR. Relative to baseline, reductions in back pain severity and improvements in Oswestry Disability Index (ODI) were maintained for both the activL and Control TDR groups through 5 years. The activL group showed significantly better range of motion for flexion-extension rotation, flexion-extension translation, and disc angle, compared with Control TDR. Freedom from a serious adverse event through 5 years was 64% in activL patients, 47% in Control patients (log-rank P = 0.0068). Freedom from index-level and adjacent-level reoperation was high for TDR patients, ranging between 94% and 99%, respectively.Conclusion: Long-term evidence supports lumbar total disc replacement as safe. The next-generation activL Artificial Disc is more effective at preserving range of motion than first-generation lumbar TDRs (ProDisc-L and Charité) and offers a higher safety profile. Other primary and secondary outcomes are similar between disc designs.Level Of Evidence: 2. [ABSTRACT FROM AUTHOR]

Study Design: A modified Delphi method was used to establish consensus. Subject matter experts were invited to participate as the expert panel. Best practice statements were distributed to the panel. Panel members were asked to mark "agree" or "disagree" after a series of statements during several rounds until either consensus could be obtained or the practice method was deemed unable to achieve consensus.Objective: Lumbar total disc replacement (TDR) is acknowledged as an alternative to spinal fusion in appropriately selected patients. There is a lack of unanimity on the appropriate postoperative patient protocols and rehabilitation expectations for the procedure. The long-term viability of Lumbar TDR, further adoption in the community setting and specific patient outcomes are contingent on the existence of appropriate postoperative recovery programs.Summary Of Background Data: Currently there are no established methods for postoperative care following lumbar TDR. Establishing a postoperative clinical pathway algorithm may improve patient outcomes with respect to lumbar TDR.Method: A lumbar TDR expert panel of 22 spine surgeons employed a modified Delphi method to drive consensus on postoperative care following single-level Lumbar TDR. The panel first reviewed literature and guidelines relevant to postoperative care following lumbar TDR. Panel members considered 21 survey questions intended to determine "standard-practice" postoperative care recommendations for patients who have undergone lumbar TDR for the initial recovery phase (0-4 wk) and rehabilitation (4-20 wk). Each panel member participated in a round of anonymous voting followed by a group discussion. Consensus was defined as 80% agreement or higher among the respondents.Results: Consensus was achieved in 11 of the 21 survey questions. There was a high degree of consensus around the key goals for both the initial recovery and rehabilitation phases, ceased use of narcotics for pain management by 4 weeks postoperative, unrestricted walking immediately following surgery, timelines for physical therapy (within 2-4 wk) and return to work based on level of activity (as early as 1 wk postoperative). Lack of agreement included the use of back bracing and timing of postoperative visits. Generally, panel members felt that patient expectations regarding return to function were different following lumbar TDR versus fusion and warrant further study.Conclusion: Surgeon and patient alignment around postoperative expectations may significantly affect the long-term results of lumbar TDR. This surgeon consensus study found agreement for immediate postoperative ambulation, rapid reduction in opioids within the first month, and early return to work. When expectations are appropriately set with patients preoperatively, both provider and patient have shared goals in the return-to-function process.Level Of Evidence: 5. [ABSTRACT FROM AUTHOR]

Most total disc replacements provide excessive mobility and not reproduce spinal kinematics, inducing zygapophyseal joint arthritic changes and chronic back pain. In cadaveric lumbosacral spines, we studied if a new lumbar disc prosthesis kinematics mimics the intact intervertebral disc. In eight cold preserved cadaveric lumbosacral spines, we registered the movement ranges in flexion, extension, right and left lateral bending, and rotation in the intact status, post-discectomy, and after our prosthesis implantation, comparing them for each specimen. Comparing the intact lumbosacral spine with the L 4 -L 5 prosthesis implanted specimens, we saw statistically significant differences in lateral bending and right rotation but not in the full range of rotation. Analyzing segments, we also noticed statistically significant differences at L 4 -L 5 in flexion-extension and rotation. On the other hand, the L 4 -L 5 discectomy, compared to the baseline spine condition, showed a statistically significant mobility increase in flexion, extension, lateral bending, and axial rotation, with an abnormal instantaneous center of rotation, which destabilizes the segment partly due to anterior annulus surgical removal. Disc prosthesis implantation reversed these changes in instantaneous center of rotation, but the prosthesis failed to restore the initial range of motion due to the destabilization of the ligaments in the operated disc. The ADDISC total disc replacement reproduces the intact disc kinematics and Instantaneous Center of Rotation, but the prosthesis fails to restore the initial range of motion due to ligament destabilization. More studies will be necessary to define a technique that restores the damaged ligaments when implanting the prosthesis. • Total disc replacements provide excess mobility, not reproducing instantaneous rotation center. • We created a new design based on the intact disc movement range and instantaneous rotation center. • Our implant reproduces intact disc kinematics and instantaneous rotation center. • This feature should provide less stress on the index and adjacent level zygapophyseal joints. [ABSTRACT FROM AUTHOR]