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Background: Implanting hardware into surgical sites increases the rate of infection associated with these sites. Without novel efforts to reduce this rate of infection, we can expect to see an incr...

BACKGROUND: Expandable devices for transforaminal or posterior lumbar interbody fusion (TLIF and PLIF, respectively) may enable greater restoration of disc height, foraminal height, and stability within the interbody space than static spacers. Medial-lateral expansion may also increase stability and resistance to subsidence. This study evaluates the clinical and radiographic outcomes from early experience with a bidirectional expandable device. METHODS: This was a retrospective analysis of a continuous series of patients across 3 sites who had previously undergone TLIF or PLIF surgery with a bidirectional expandable interbody fusion device (FlareHawk, Integrity Implants, Inc) at 1 or 2 contiguous levels between L2 and S1. Outcomes included the Oswestry Disability Index (ODI), a visual analog scale (VAS) for back pain or leg pain, radiographic fusion by 1 year of follow-up, subsidence, device migration, and adverse events (AE). RESULTS: There were 58 eligible patients with radiographs for 1-year fusion assessments and 45 patients with ODI, VAS back pain, or VAS leg pain data at baseline and a mean follow-up of 4.5 months. The ODI, VAS back pain, and VAS leg pain scores improved significantly from baseline to final follow-up, with mean improvements of 14.6 ± 19.1, 3.4 ± 2.6, and 3.9 ± 3.4 points (P < .001 for each), respectively. In addition, 58% of patients achieved clinically significant improvements in ODI, 76% in VAS back pain, and 71% in VAS leg pain. By 1 year, 96.6% of patients and 97.4% of levels were considered fused. There were zero cases of device subsidence and 1 case of device migration (1.7%). There were zero device-related AEs, 1 intraoperative dural tear, and 3 subsequent surgical interventions. CONCLUSIONS: The fusion rate, improvements in patient-reported outcomes, and the AEs observed are consistent with those of other devices. The bidirectional expansion mechanism may provide other important clinical value, but further studies will be required to elucidate the unique advantages. LEVEL OF EVIDENCE: 4.

Background A number of minimally invasive sacroiliac (SI) joint fusion solutions for placing implants exist, with reduced post-operative pain and improved outcomes compared to open procedures. The objective of this study was to compare two MIS SI joint fusion approaches that place implants directly across the joint by comparing the ilium and sacrum bone characteristics and SI joint separation along the implant trajectories. Methods Nine cadaveric specimens (n = 9) were CT scanned and the left and right ilium and sacrum were segmented. The bone density, bone volume fraction, and SI joint gap distance were calculated along lateral and posterolateral trajectories and compared using analysis of variance between the two orientations. Results Iliac bone density, indicated by the mean Hounsfield Unit, was significantly greater for each lateral trajectory compared to posterolateral. The volume of cortical bone in the ilium was greater for the middle lateral trajectory compared to all others and for the top and bottom lateral trajectories compared to both posterolateral trajectories. Cortical density was greater in the ilium for all lateral trajectories compared to posterolateral. The bone fraction was significantly greater in all lateral trajectories compared to posterolateral in the ilium. No differences in cortical volume, cortical density, or cancellous density were found between trajectories in the sacrum. The ilium was significantly greater in density compared with the sacrum when compared irrespective of trajectory (p < 0.001). The posterolateral trajectories had a significantly larger SI joint gap than the lateral trajectories (p < 0.001). Conclusion Use of the lateral approach for minimally invasive SI fusion allows the implant to interact with bone across a significantly smaller joint space. This interaction with increased cortical bone volume and density may afford better fixation with a lower risk of pull-out or implant loosening when compared to the posterolateral approach.

Background: Effective triage - directing patients with low back pain to appropriate treatment or correct referral - is fundamental to quality care. Without guidelines, a physician's initial decision may lead to unnecessary investigation, unneeded intervention or unwarranted consultation.Methods: To compare the functional outcomes of patients triaged by a classification based on clinical presentation with those of patients selected at the clinicians’ discretion, an insurance-owned hospital network employed forty-seven specially-trained physical therapists, working within participating primary care practices, to classify low back pain patients into specific Patterns of Pain. Between October 2017 and April 2019, the primary care physicians used this classification, derived entirely from the patient's history and physical examination, to direct subsequent treatment for 260 consecutive low back pain patients. Patients with systemic symptoms, recent substantial trauma or non-mechanical diagnoses indicative of spinal infections or possible malignancy were excluded. Functional outcome measures were spinal imaging, opioid use, length of treatment and number of visits, back-related unplanned care, frequency of spinal surgery and back-related episode cost. These were compared with a control group of 256 propensity-matched patients and, for assessing the financial impact, with a historic cohort of 111 previously treated, non-classified patients.Results: Spinal imaging: study group 24.5%; controls 42.2% (P< .001). Narcotic use: study group 4.6%; controls 13.3% (P< .001). Treatment length: study group 62.2 days; controls 74.5 days (P=.10). Treatment visits: study group 1528 visits; controls 2,046 visits (P=.003). Unplanned care: study group 1.9%; controls 12.8% (P< .001). Spine surgery: study group 15.4%; controls 26.2% (P=.005). Episode cost: study group $1453; controls $2334 (P=.005).Conclusions: A well-defined clinically-based triage system produced meaningful reductions in imaging, opioid use, treatment duration, unplanned interventions, surgery and cost of care.

Noninvasive ventilator support using bi-level positive airway pressure/continuous positive airway pressure (BiPAP/CPAP) is commonly utilized for chronic medical conditions like sleep apnea and neuromuscular disorders like amyotrophic lateral sclerosis (ALS) that lead to weakness of respiratory muscles. Generic masks come in standard sizes and are often perceived by patients as being uncomfortable, ill-fitting, and leaky. A significant number of patients are unable to tolerate the masks and eventually stop using their devices. The goal of this project is to develop custom-fit masks to increase comfort, decrease air leakage, and thereby improve patient compliance. A single-patient case study of a patient with variant ALS was performed to evaluate the custom-fit masks. His high nose bridge and overbite of lower jaw caused poor fit with generic masks, and he was noncompliant with his machine. Using desktop Stereolithography three-dimensional (3D) printing and magnetic resonance imaging (MRI) data, a generic mask was extended with a rigid interface such that it was complementary to the patient's unique facial contours. Patient or clinicians interactively select a desired mask shape using a newly developed computer program. Subsequently, a compliant silicone layer was applied to the rigid interface. Ten different custom-fit mask designs were made using computer-aided design software. Patient evaluated the comfort, extent of leakage, and satisfaction of each mask via a questionnaire. All custom-fit masks were rated higher than the standard mask except for two. Our results suggest that modifying generic masks with a 3D-printed custom-fit interface is a promising strategy to improve compliance with BiPAP/CPAP machines.

Sacroiliac joint (SIJ) dysfunction and its surgical treatment remain a controversial topic in spine surgery. Determining success after SIJ fusion may be difficult due to preexisting back pain, lumbar fusion (LF), and functional disability. We examine the utility of Oswestry Disability Index (ODI) as a measure of clinical outcomes after minimally invasive SIJ fusion. A retrospective review of 24 patients with at least 12- months follow-up. Patients were divided into two groups based on presence of previous LF. Their post-operative ODI was compared with overall satisfaction, pain reduction, and return to work status. No difference in demographics was found in patients with and without prior LF with 92% of patients reporting lower post-operative pain and 96% being satisfied. Presence of LF did not show any statistically significant differences in pain or satisfaction. However, patient with prior LF reported lower ODI than those without LF at 1-year post-operatively (P=0.015). Postoperative ODI may give a falsely pessimistic impression of outcomes in SIJ fusion patients with prior LF, and its use and limitations should be carefully considered in future studies.

Background Interbody fusion cages with integrated fixation components have become of interest due to their ability to provide enhanced post-operative stability and mitigate device migration. A recently approved anterior lumbar interbody fusion cage with integrated fixation anchors has yet to be compared in vitro to a standard polyetheretherketone cage when used in combination with an interspinous process clamp. Methods Twelve human cadaveric lumbar segments were implanted at L4–L5 with a Solus interbody cage (n = 6) or standard polyetheretherketone cage (n = 6) following Intact testing and discectomy. Each cage was subsequently evaluated in all primary modes of loading after supplementation with the following posterior constructs: interspinous process clamp, bilateral transfacet screws, unilateral transfacet screw with contralateral pedicle screws, and bilateral pedicle screws. Range of motion results were normalized to Intact, and a two-way mixed analysis of variance was utilized to detect statistical differences. Findings The Solus cage in combination with all posterior constructs provided significant fixation compared to Intact in all loading conditions. The polyetheretherketone cage also provided significant fixation when combined with all screw based treatments, however when used with the interspinous process clamp a significant reduction was not observed in lateral bending or axial torsion. Interpretation Interbody cages with integrated fixation components enhance post-operative stability within the intervertebral space, thus affording clinicians the potential to utilize less invasive methods of posterior stabilization when seeking circumferential fusion. Interspinous process clamps, in particular, may reduce peri-operative and post-operative comorbidities compared to screw based constructs. Further study is necessary to corroborate their effectiveness in vivo .

While low back pain is one of the most prevalent, if not the most prevalent reasons for visits to physicians, a majority of patients with low back pain cannot be given a definitive diagnosis. The current standard of care for function assessment of the lumbar spine focuses on uncontrolled patient directed motion which results in increased inter-patient variability and diagnostic misclassifications. The purpose of the current paper is to compare the measurement variability of lumbar spine motion when diagnosed using measurements of intervertebral motion taken from standard flexion extension bending radiographs (FE) between uncontrolled and controlled motion and to assess the rate of diagnostic misclassification errors (false positives and false negatives) in the detection of lumbar instability. 109 patients (57 asymptomatic, 52 symptomatic) were consented in the prospective investigation. The research was designed to compare studies involving FE to controlled motion bending radiographs (CCBR) using the Vertebral Motion Analysis (VMA) within the same patient. Measurement variability was determined by the mean and standard deviation of intervertebral rotation when evaluated by 9 independent observers evaluating each of the 109 patients FE and CCBR. The resulting standard deviation of the intervertebral rotation determinations was used as the measure of variability. Sensitivity (true positive rate) and specificity (true negative rate), were constructed using asymptomatic individuals and symptomatic patients in order to determine true positive (TP) and true negative (TN) appointments. The analysis was compared to known threshold of 25° (IVR) to determine the rates of false negatives (FN) and false positive (FP) rates. Sensitivity and specificity were calculated as TP/(TP/FN) and TN/(FP+TN), respectively. There was statistical greater measurement variability in intervertebral rotation in FE when compared to CCBR (both standing and lying). When comparing measurement variability between FE and CCBR, results indicate between a 26% to 46% decrease in measurement variability under CCBR compared to FE. These findings are consistent across asymptomatic and symptomatic patients. Sensitivity measures were 6.2% (VMA 12.6%, FE 6.4%) greater in the VMA test compared to the FE. Specificity measures were 8.4% (VMA 99.1%, FE 90.7%) greater in the VMA test compared to the FE. The current standard of care for functional testing of the lumbar spine utilizes uncontrolled FE with a manual data evaluation process. Recent developments in using computerized imaging processes has improved, however there remains variability in patient bending due to the self-selected rate and position of the bending. CCBR results in a significant reduction in measurement variability of intervertebral rotation measurements. Reducing measurement variability would be expected to improve the efficacy rates of surgeries indicated for these conditions.

Object Deep brain stimulation (DBS) of the lateral hypothalamic area (LHA) has been suggested as a potential treatment for intractable obesity. The authors present the 2-year safety results as well as early efficacy and metabolic effects in 3 patients undergoing bilateral LHA DBS in the first study of this approach in humans. Methods Three patients meeting strict criteria for intractable obesity, including failed bariatric surgery, underwent bilateral implantation of LHA DBS electrodes as part of an institutional review board– and FDA-approved pilot study. The primary focus of the study was safety; however, the authors also received approval to collect data on early efficacy including weight change and energy metabolism. Results No serious adverse effects, including detrimental psychological consequences, were observed with continuous LHA DBS after a mean follow-up of 35 months (range 30–39 months). Three-dimensional nonlinear transformation of postoperative imaging superimposed onto brain atlas anatomy was used to confirm and study DBS contact proximity to the LHA. No significant weight loss trends were seen when DBS was programmed using standard settings derived from movement disorder DBS surgery. However, promising weight loss trends have been observed when monopolar DBS stimulation has been applied via specific contacts found to increase the resting metabolic rate measured in a respiratory chamber. Conclusions Deep brain stimulation of the LHA may be applied safely to humans with intractable obesity. Early evidence for some weight loss under metabolically optimized settings provides the first “proof of principle” for this novel antiobesity strategy. A larger follow-up study focused on efficacy along with a more rigorous metabolic analysis is planned to further explore the benefits and therapeutic mechanism behind this investigational therapy.

Background The application of kinematic data acquired during biomechanical testing to specimen-specific, three-dimensional models of the spine has emerged as a useful tool in spine biomechanics research. However, the development of these models is subject to segmentation error because of complex morphology and pathologic changes of the spine. This error has not been previously characterized. Methods Eight cadaveric lumbar spines were prepared and underwent computed tomography (CT) scanning. After disarticulation and soft-tissue removal, 5 individual vertebrae from these specimens were scanned a second time. The CT images of the full lumbar specimens were segmented twice each by 2 operators, and the images of the individual vertebrae with soft tissue removed were segmented as well. The solid models derived from these differing segmentation sessions were registered, and the distribution of distances between nearest neighboring points was calculated to evaluate the accuracy and precision of the segmentation technique. Results Manual segmentation yielded root-mean-square errors below 0.39 mm for accuracy, 0.33 mm for intrauser precision, and 0.35 mm for interuser precision. Furthermore, the 95th percentile of all distances was below 0.75 mm for all analyses of accuracy and precision. Conclusions These findings indicate that such models are highly accurate and that a high level of intrauser and interuser precision can be achieved. The magnitude of the error presented here should inform the design and interpretation of future studies using manual segmentation techniques to derive models of the lumbar spine.

Efficient load-sharing in the spinal column relies on the proper working of the components of the Functional Spinal Unit (FSU). Due to various reasons such as trauma, ageing and diseases, these components or even the entire FSU can get degenerated or injured during a person’s lifetime. Spinal column reconstruction surgerieswere created with the aimto restore the functioning of the diseased or injured spine. Several spinal implants are available today for the surgeon to aid in this process. There are three major categories of these devices: anterior stabilization devices, posterior stabilization devices and motion preservation devices. This review highlights thein vitro researchdone on these devices,over the past five decades, to evaluate their ability to effectively share loads at the operated level of the spinal column. Some conclusions have been drawn based on this research.Dynamic anterior cervical plates are more successful at maintaining load-sharing after graft subsidence and anterior stabilization devices can be used to provide support to posterior stabilization devices during severe anterior column injuries. Motion preservation devices, specifically cervical disc prostheses and facet replacement systems,show great potential in maintaining physiologicalloads in the spinal column. Further clinical investigation of all these implants would help to identify the contributing factors for their success or failure post-surgery. It would also aid in determining the requirements of an ideal spine stabilization device which perfectly mimics the physiological load-sharing properties of the FSU and its components.

The history and rationale of posterior dynamic spinal fusion devices has been derived through the experiences with arthrodesis and devices that serve as adjuncts to such procedures. Dynamic fusion devices provide stabilization through immediate fixation while allowing load sharing. Historically, incorporating these two important concepts in surgical techniques along with the implanted devices facilitates the bone healing process. It stands to reason, spinal fusion techniques that provide immediate stabilization and simultaneously significant graft loading should have the same clinical success seen in other long bone and cervical spine arthrodesis techniques. The load-sharing capability is device-dependent and posterior dynamic constructs theoretically allow dynamic compression of the anterior column higher than that of traditional rigid rod fixation.

Background context Surgical instrumentation used for posterior craniocervical instability has evolved from simple wiring techniques to sophisticated implant systems that incorporate multiple means of rigid fixation for the cervical spine. Polyaxial screws and lamina hooks in conjunction with occipital plating and transitional rods for caudal fixation theoretically allow for fixation points at each vertebra along the posterior aspect of the cervical spine. However, the potential for anatomical constraints to prevent intraoperative instrumentation at the desired vertebral level exists. The biomechanical implications of such “skipped segments” have not been well documented. Purpose The purpose of this study was to determine the biomechanical effects of partial three-point fixation versus sequential fixation at all levels of the cervical spine from the occiput to T1. Study design/setting Fresh frozen human cadaveric cervical spines from the occiput (CO) to T1 were prepared and mounted on a spine simulator. Motion was assessed by a three-dimensional optoelectronic motion measurement system. Kinematic data were collected and range of motion (ROM) was analyzed and reported. Methods Eight human noninstrumented intact spines (Treatment 1) were tested for baseline ROM which was subclassified into axial (CO–C2), upper subaxial (C2–C4), lower subaxial (C4–T1), and total (CO–T1) ROM. Flexion extension, lateral bending, and axial torsion testing with an applied ±3 Nm moment was conducted. The same testing protocol was performed after three-point fixation in which screws were placed at the CO, C4, and T1 (Treatment 2), and also after sequential fixation at all levels from CO through T1 (Treatment 3). Fixation was achieved using an occipital plate, 12-mm lateral mass screws for C3 through C6, and 20-mm lateral mass or pedicle screws were used for C1, C2, C7, and T1. Results Intact spine testing (Treatment 1) showed statistically significant larger ROM for all segments and for overall ROM when compared with both Treatment 2 (partial fixation CO, C4, and T1) and Treatment 3 (sequential fixation at all levels from the occiput to T1). When comparing Treatment 2 with Treatment 3, no significant difference in flexion extension ROM was detected between axial, upper subaxial, lower subaxial, and total overall ROM (p > .05). Lateral bending showed statistically significant increased ROM for Treatment 2 constructs compared with Treatment 3 constructs in total overall lateral bend ROM. For axial rotation, there was significantly increased ROM for Treatment 2 at the lower subaxial segment and total overall ROM (p Conclusions There was no statistical difference between the three-point fixation treatment group and the sequential fixation group in flexion extension bending. Lateral bending and axial rotation demonstrated an increase in total overall ROM with partial fixation compared with fixation at all levels. Axial rotation in particular showed increased mobility in the lower cervical spine for the partial fixation group. In the instance where surgeons are not able to apply sequential fixation at diseased levels, especially for the lower subaxial cervical spine, particular attention to limitation of lateral bending and axial rotation by the use of external orthotics must be considered.

Object In this study the authors present the preliminary clinical outcomes of dynamic stabilization with the Dynesys spinal system as part of a multicenter randomized prospective Food and Drug Administration (FDA) investigational device exemption (IDE) clinical trial. Methods This study included 101 patients from six IDE sites (no participants were omitted from the analysis) who underwent dynamic stabilization of the lumbar spine with the Dynesys construct. Patient participation was based on the presence of degenerative spondylolisthesis or retrolisthesis (Grade I), lateral or central spinal stenosis, and their physician's determination that the patient required decompression and instrumented fusion for one or two contiguous spinal levels between L-1 and S-1. Participants were evaluated preoperatively, postoperatively at 3 weeks, and then at 3-, 6-, and 12-month intervals. The 100-mm visual analog scale was used to score both lower-limb and back pain. Patient functioning was evaluated using the Oswestry Disability Index (ODI), and the participants' general health was assessed using the Short Form-12 questionnaire. Overall patient satisfaction was also reported. One hundred one patients (53 women and 48 men) with a mean age of 56.3 years (range 27–79 years) were included. The mean pain and function scores improved significantly from the baseline to 12-month follow-up evaluation, as follows: leg pain improved from 80.3 to 25.5, back pain from 54 to 29.4, and ODI score from 55.6 to 26.3%. Conclusions The early clinical outcomes of treatment with Dynesys are promising, with lessening of pain and disability found at follow-up review. Dynesys may be preferable to fusion for surgical treatment of degenerative spondylolisthesis and stenosis because it decreases back and leg pain while avoiding the relatively greater tissue destruction and the morbidity of donor site problems encountered in fusion. However, long-term follow-up care is still recommended.

Background Pure-moment loading is the test method of choice for spinal implant evaluation. However, the apparatuses and boundary conditions employed by laboratories in performing spine flexibility testing vary. The purpose of this study was to quantify the differences, if they exist, in intervertebral range of motion (ROM) resulting from different pure-moment loading apparatuses used in two laboratories. Methods Twenty-four (laboratory A) and forty-two (laboratory B) intact L1-S1 specimens were loaded using pure moments (±7.5 Nm) in flexion-extension (FE), lateral bending (LB) and axial torsion (AT). At laboratory A, pure moments were applied using a system of cables, pulleys and suspended weights in 1.5 Nm increments. At laboratory B, specimens were loaded in a pneumatic biaxial test frame mounted with counteracting stepper-motor-driven biaxial gimbals. ROM was obtained in both labs using identical optoelectronic systems and compared. Results In FE, total L1-L5 ROM was similar, on average, between the two laboratories (lab A: 37.4° ± 9.1°; lab B: 35.0° ± 8.9°, p=0.289). Larger apparent differences, on average, were noted between labs in AT (lab A: 19.4° ± 7.3°; lab B: 15.7° ± 7.1°, p=0.074), and this finding was significant for combined right and left LB (lab A: 45.5° ± 11.4°; lab B: 35.3° ± 8.5°, p Conclusions To our knowledge, this is the first study comparing ROM of multi-segment lumbar spines between laboratories utilizing different apparatuses. The results of this study show that intervertebral ROM in multi-segment lumbar spine constructs are markedly similar in FE loading. Differences in boundary conditions are likely the source of small and sometimes statistically significant differences between the two techniques in LB and AT ROM. The relative merits of each testing strategy with regard to the physiologic conditions that are to be simulated should be considered in the design of a study including LB and AT modes of loading. An understanding of these differences also serves as important information when comparing study results across different laboratories.

Background Pure moment testing is a common method used in cadaveric spine testing. The fundamental basis for the widespread acceptance of applying a pure moment is uniform loading along the column of the spine. To our knowledge, this protocol has not been experimentally verified on a multi–degree of freedom testing apparatus. Given its ubiquitous use in spine biomechanics laboratories, confirmation of this comparative cadaveric test protocol is paramount. Methods Group A specimens (n =13) were used to test the pure moment protocol, by use of 3 constructs that changed the number of involved vertebrae, orientation, and rigidity of the spine construct. Group B specimens (n = 6) were used to determine whether potting orientation, testing order, or degradation affected the range of motion (ROM) by use of 8 constructs. Each group was subjected to 3 cycles of flexion-extension, lateral bending, and axial torsion. The data from the third cycle were used to calculate the ROM for each method. Results Group A testing resulted in significant differences in ROM across the 3 constructs for lateral bending and axial torsion (P < .02) and trended toward a difference for flexion-extension (P = .055). Group B testing showed an increase in ROM across 8 constructs (P < .04) but no significant difference due to the orientation change. Conclusion The increased ROM across constructs observed in both groups indicates that the cause is likely the testing order or degradation of the specimens, with orientation having no observed effect. The data do not invalidate pure moment testing, and its use should persist.

Background context Traditional methods for the evaluation of in vivo spine kinematics introduce significant measurement variability. Digital videofluoroscopic techniques coupled with computer-assisted measurements have been shown to reduce such error, as well as provide detailed information about spinal motion otherwise unobtainable by standard roentgenograms. Studies have evaluated the precision of computer-assisted fluoroscopic measurements; however, a formal clinical evaluation and comparison with manual methods is unavailable. Further, it is essential to establish reliability of novel measurements systems compared with standard techniques. Purpose To determine the repeatability and reproducibility of sagittal lumbar intervertebral measurements using a new system for the evaluation of lumbar spine motion. Study design Reliability evaluation of digitized manual versus computer-assisted measurements of the lumbar spine using motion sequences from a videofluoroscopic technique. Patient sample A total of 205 intervertebral levels from 61 patients were retrospectively evaluated in this study. Outcome measures Coefficient of repeatability (CR), limits of agreement (LOA), intraclass correlation coefficient (ICC; type 3,1), and standard error of measurement. Methods Intervertebral rotations and translations (IVR and IVT) were each measured twice by three physicians using the KineGraph vertebral motion analysis (VMA) system and twice by three different physicians using a digitized manual technique. Each observer evaluated all images independently. Intra- and interobserver statistics were compiled based on the methods of Bland-Altman (CR, LOA) and Shrout-Fleiss (ICC, standard error of measurement). Results The VMA measurements demonstrated substantially more precision compared with the manual technique. Intraobserver measurements were the most reliable, with a CR of 1.53 (manual, 8.28) for IVR, and 2.20 (manual, 11.75) for IVT. The least reliable measurements were interobserver IVR and IVT, with a CR of 2.15 (manual, 9.88) and 3.90 (manual, 12.43), respectively. The ICCs and standard error results followed the same pattern. Conclusions The VMA system markedly reduced variability of lumbar intervertebral measurements compared with a digitized manual analysis. Further, computer-assisted fluoroscopic imaging techniques demonstrate precision within the range of computer-assisted X-ray analysis techniques.

Background While low back pain is one of the most prevalent, if not the most prevalent reasons for visits to physicians, a majority of patients with low back pain cannot be given a definitive diagnosis. While there have been substantial advances in imaging technologies over the past 30 years, relatively little has changed in the methodologies for evaluating functionality of the lumbar spine. The current standard of care for function assessment of the lumbar spine focuses on uncontrolled patient directed motion which results in increased inter-patient variability. Recent advancements in functional lumbar spine testing utilize controlled bending and computerized imaging evaluation. Purpose To compare the measurement variability of lumbar spine motion when diagnosed using measurements of intervertebral motion taken from standard bending flexion/extension radiographs (FE) between uncontrolled and controlled motion. Study Design One-hundred nine patients (57 asymptomatic, 52 symptomatic) were consented in the prospective investigation. The research was designed to compare studies involving FE to controlled motion bending radiographs using the Vertebral Motion Analysis (VMA), (Ortho Kinematics, Inc) within the same patient. Each patient agreed to undergo fluoroscopic still imaging to capture FE data and to undergo cine fluoroscopic imaging to capture VMA data. Outcome Measures Measurement variability was determined by the mean and standard deviation of intervertebral rotation when evaluated by 5 independent observers evaluating each of the 109 patients FE and VMA. The resulting standard deviation of the intervertebral rotation determinations was used as the measure of variability. Methods The VMA measurements for assessing intervertebral motion were characterized by the use of: (1) a handling device that assists patients through a standard arc of lumbar bending in both an upright and recumbent posture (70 degree flexion/extension arcs; 60 degree left/right bending arcs); (2) video fluoroscopy imaging of the lumbar spine during bending (capturing images at 8 frames per second); and (3) image processing software capable of automatic frame-to-frame registration and tracking of vertebral bodies across the sequence of video-fluoroscopic images to derive measurements of intervertebral rotation and translation. The FE data were assessed from voluntary bending by the patient. Results There was statistical greater measurement variability in intervertebral rotation in FE when compared to VMA (both standing and lying). When comparing measurement variability between FE and VMA, results indicate between a 26% to 46% decrease in measurement variability under VMA compared to FE. These findings are consistent across asymptomatic and symptomatic patients. Conclusions The current standard of care for functional testing of the lumbar spine utilizes uncontrolled FE with a manual data evaluation process. Recent developments in using computerized imaging processes has improved, however there remains variability in patient bending due to the self-selected rate and position of the bending. VMA results in a significant reduction in measurement variability of intervertebral rotation measurements.

Study Design: A comparative biomechanical human cadaveric spine study of a dynamic fusion rod and a traditional titanium rod. Objective: The purpose of this study was to measure and compare the biomechanical metrics associated with a dynamic fusion device, Isobar TTL Evolution, and a rigid rod. Summary of Background Data: Dynamic fusion rods may enhance arthrodesis compared with a rigid rod. Wolff’s law implies that bone remodeling and growth may be enhanced through anterior column loading (AL). This is important for dynamic fusion rods because their purpose is to increase AL. Methods: Six fresh-frozen lumbar cadaveric specimens were used. Each untreated specimen (Intact) underwent biomechanical testing. Next, each specimen had a unilateral transforaminal lumbar interbody fusion performed at L3–L4 using a cage with an integrated load cell. Pedicle screws were also placed at this time. Subsequently, the Isobar was implanted and tested, and finally, a rigid rod replaced the Isobar in the same pedicle screw arrangement. Results: In terms of range of motion, the Isobar performed comparably to the rigid rod and there was no statistical difference found between Isobar and rigid rod. There was a significant difference between the intact and rigid rod and also between intact and Isobar conditions in flexion extension. For interpedicular displacement, there was a significant increase in flexion extension (P=0.017) for the Isobar compared with the rigid rod. Isobar showed increased AL under axial compression compared with the rigid rod (P=0.024). Conclusions: Isobar provided comparable stabilization to a rigid rod when using range of motion as the metric, however, AL was increased because of the greater interpedicular displacement of dynamic rod compared with a rigid rod. By increasing interpedicular displacement and AL, it potentially brings clinical benefit to procedures relying on arthrodesis.

Imaging modalities such as X-Ray, computerized tomography (CT), magnetic resonance imaging (MRI), and bone scan have all become essential to the evaluation of bone and soft tissue in patients with back pain. All techniques provide valuable static images of the spine, yet lack the capability of providing detailed information about spinal motion. Dynamic end-range x-rays, the standard in assessment of range of motion and vertebral translation, are taken at the patient’s maximum voluntary bending angle in flexion and extension (FE) and/or lateral bending (LB). The current standard of practice is to measure, with ruler and protractor, the relative change between adjacent vertebrae at each bending extreme. The resulting rotational or translational values are then expressed as the intervertebral angle (IVA) or as a percentage of vertebral body depth, respectively. This method, however, is subject to a high level of patient, imaging site, and observer related variability, in the form of uncontrolled bending angles, disparities in equipment and practices, and manual image analysis. An additional limitation of static imagery is the inability to assess motion in the spine as it traverses between end ranges. This information may expose motion abnormalities that occur mid-range that might otherwise be missed by clinicians. Lastly, motion of the spine may present differently in weighted and un-weighted positions. Effects of muscle activation and gravitational forces are not accounted for by current standards.Copyright © 2012 by ASME

Back pain is the second most common reason for physician visits in the United States, and affects up to 84 percent of patients at some point in their lives (Deyo & Tsui-Wu 1987). For many patients, neck and back pain is often due to injury or spinal instability through trauma, disease or degeneration. This can cause impingement of neural structures resulting in pain, numbness, or weakness. Also, this can be a consequence of changes in the vertebral bodies or degenerative changes in the intervertebral cartilaginous discs. Treatment of such disorders may require surgery if the pain or neurologic symptoms prove to be intractable to conservative treatments such as physical therapy or pain medications.

Study Design. In vitro flexibility testing of the lumbar spine. Objective. The goal of this study was to evaluate a motion-preserving posterior dynamic stabilization (PDS) implant based on newly defined parameters describing interpedicular kinematics. Summary of Background Data. PDS implants have been designed as either motion-preserving or adjunct-to-fusion devices to treat various degenerative spinal pathologies. The ambiguity of design and evaluation goals and the inability of traditional biomechanical parameters to appropriately describe the behavior of PDS devices in vitro have served as the impetus to develop kinematic parameters more specific to this class of device. Methods. Flexibility testing of 6 fresh-frozen human lumbar spines was conducted before and after destabilization of the index level (L4–L5). Testing under the same protocol was repeated after treatment at the index level with a 1-level PDS device, extension of the device to the adjacent inferior level (L5–S1), and treatment with a hybrid construct consisting of the PDS implant at L4–L5 and rigid fixation at L5–S1. The kinematic response was recorded using an optoelectric tracking system and reported in terms of intervertebral range of motion (ROM) and newly developed parameters describing interpedicular motion. Results. Based on ROM and interpedicular kinematics, the devices implanted at L4–L5 provide significant but not differing stabilization in flexion-extension with implantation after a significant destabilization procedure. Interpedicular kinematic results indicate that the 2-level construct contributes to significantly more motion at L5–S1 compared with rigid fixation. This result was not detected when evaluated by the ROM metric. Conclusion. Those involved in the design and evaluation of PDS devices may benefit from evaluation of interpedicular kinematics. Evaluating intervertebral motion from the perspective of the pedicle screw allows for a direct and intuitive translation between in vitro test results and design parameters. Furthermore, these parameters may provide additional clinical insight into the biomechanics of the healthy and pathological spine. The study presented indicates that this approach may be more sensitive in detecting differences in implant motion between PDS devices.

The use of ultrasonic technology for bone removal offers the potential advantages over the use of traditional hand instruments or cutting burrs of more precise bone resection and reduced soft-tissue injury. While the use of modified ultrasonic aspirators has been described for bone removal in spinal surgery, none of these instruments has been systematically examined to evaluate safety and efficacy. Thus, we compared laminectomies using traditional instruments, and traditional instruments with an ultrasonic osteotome, in an ovine model. We used a combination of clinical examination, intra-operative and post-operative neuromonitoring and histological analysis to evaluate safety. The secondary endpoint of efficiency was assessed by examining operative times. No significant difference was found between groups in neurophysiology or the Tarlov clinical rating scale. Histology revealed inflammatory or reparative changes in 6/8 experimental animals and 2/4 control animals with a single section in an experimental animal revealing focal nerve root disruption and mild axonal loss. A single durotomy was noted in both the control and experimental groups. Operative time for the experimental group was significantly shorter than the operative time for the control group.

Bow hunter's stroke is a rare symptomatic vertebrobasilar insufficiency in which vertebral artery (VA) is mechanically occluded during head rotation. Various pathologic conditions have been reported as causes of bow hunter's stroke. However, bow hunter's stroke caused by facet hypertrophy of C1-2 has not been reported. A 71-year-old woman presented with symptoms of vertebrobasilar insufficiency. Spine computed tomography showed massive facet hypertrophy on the left side of C1-2 level. A VA angiogram with her head rotated to the right revealed significant stenosis of left VA. C1-2 posterior fixation and fusion was performed to prevent serious neurologic deficit from vertebrobasilar stroke.

Approximately one million spinal surgeries are performed in the United States each year. The risk of an incidental durotomy (ID) and resultant persistent cerebrospinal fluid (CSF) leakage is a significant concern for surgeons, as this complication has been associated with increased length of hospitalization, worse neurological outcome, and the development of CSF fistulae. Augmentation of standard dural suture repair with the application of fibrin glue has been suggested to reduce the frequency of these complications. This study examined unintended durotomies during lumbar spine surgery in a large surgical patient cohort and the impact of fibrin glue usage as part of the ID repair on the incidence of persistent CSF leakage. A retrospective analysis of 4,835 surgical procedures of the lumbar spine from a single institution over a 10-year period was performed to determine the rate of ID. The 90-day clinical course of these patients was evaluated. Clinical examination, B-2 transferrin assay, and radiographic imaging were utilized to determine the number of persistent CSF leaks after repair with or without fibrin glue. Five hundred forty-seven patients (11.3%) experienced a durotomy during surgery. Of this cohort, fibrin glue was used in the dural repair in 278 patients (50.8%). Logistic models evaluating age, sex, redo surgery, and the use of fibrin glue revealed that prior lumbar spinal surgery was the only univariate predictor of persistent CSF leak, conferring a 2.8-fold increase in risk. A persistent CSF leak, defined as continued drainage of CSF from the operative incision within 90 days of the surgery that required an intervention greater than simple bed rest or over-sewing of the wound, was noted in a total of 64 patients (11.7%). This persistent CSF leak rate was significantly higher (P < 0.001) in patients with prior lumbar surgery (21%) versus those undergoing their first spine surgery (9%). There was no statistical difference in persistent CSF leak between those cases in which fibrin glue was used at the time of surgery and those in which fibrin glue was not used. There were no complications associated with the use of fibrin glue. A history of prior surgery significantly increases the incidence of durotomy during elective lumbar spine surgery. In patients who experienced a durotomy during lumbar spine surgery, the use of fibrin glue for dural repair did not significantly decrease the incidence of a persistent CSF leak.

Anterior cervical plate (ACP) failure is rarely addressed in the literature. In this retrospective, observational, longitudinal, cohort study, the objectives were to (1) identify incidences of in vivo biomechanical failure in commercially available, US Food and Drug Administration-approved ACP systems, (2) describe modes of failure, (3) suggest structural explanations for system failure, and (4) discuss complications and treatment of patients with failed ACP systems. Investigators retrospectively identified patients who underwent anterior cervical procedures followed by use of ACP as a fusion adjunct and showed evidence of ACP failure on plain radiographs. Components of the ACP system that led to failure were identified and examined. A total of 240 patients received ACP supplementation of anterior cervical fusion constructs during the 9.5-y study period. Evidence of ACP failure was noted in 7 patients (3.3%), and an eighth patient was referred for evaluation after ACP failure. Screw-plate interface failure occurred in all 8 cases. The biomechanical method by which the bone screw head was secured into the vertebral body, or against the ACP, the use of hybrid systems, the surgical technique selected, and host factors were used to determine the rate of failure. Concern for esophageal or other tissue injury often necessitated ACP removal. Screw-plate interface failure, which was found to be the most common mode of biomechanical ACP failure, may occur in hybrid constructs and in systems that do not create a rigid interface between the screw head and the ACP. Surgical technique and patient host factors may also influence the rate of biomechanical construct failure.

Background Segmental instability of the lumbar spine is a significant cost within the US health care system; however current thresholds for indication of radiographic instability are not well defined. Purpose To determine the performance measurements of sagittal lumbar intervertebral measurements using computerassisted measurements of the lumbar spine using motion sequences from a video-fluoroscopic technique. Study design Sensitivity, specificity, predictive values, prevalence, and test-retest reliability evaluation of digitized manual versus computer-assisted measurements of the lumbar spine. Patient sample A total of 2239 intervertebral levels from 509 symptomatic patients, and 287 intervertebral levels from 73 asymptomatic participants were retrospectively evaluated. Outcome measures Specificity, sensitivity, negative predictive value (NPV), diagnostic accuracy, and prevalence between the two measurement techniques; Measurements of Coefficient of repeatability (CR), limits of agreement (LOA), intraclass correlation coefficient (ICC; type 3,1), and standard error of measurement for both measurement techniques. Methods Asymptomatic individuals and symptomatic patients were all evaluated using both the Vertebral Motion Analysis (VMA) system and fluoroscopic flexion extension static radiographs (FE). The analysis was compared to known thresholds of 15% intervertebral translation (IVT, equivalent to 5.3mm assuming a 35mm vertebral body depth) and 25° intervertebral rotation (IVR). Results The VMA measurements demonstrated greater specificity, % change in sensitivity, NPV, prevalence, and reliability compared with FE for radiographic evidence of instability. Specificity was 99.4% and 99.1% in the VMA compared to 98.3% and 98.2% in the FE for IVR and IVT, respectively. Sensitivity in this study was 41.2% and 44.6% greater in the VMA compared to the FE for IVR and IVT, respectively. NPV was 91% and 88% in the VMA compared to 62% and 66% in the FE for IVR and IVT, respectively. Prevalence was 12.3% and 11.9% for the VMA compared to 6.1% and 5.4% for the FE in IVR and IVT, respectively. Intra-observer IVR and IVT had a CR of 2.49 and 2.62, respectively. Inter-observer IVR and IVT had a CR of 1.99 and 2.81, respectively. Intra-subject (test/retest) CR were 2.49 and 3.11 for IVR and IVT, respectively. Conclusions The VMA system showed greater measurement performance in the detection of radiographic instability compared with FE radiographs.

The application of kinematic data acquired during biomechanical testing to specimen-specific, three-dimensional models of the spine has emerged as a useful tool in spine biomechanics research. However, the development of these models is subject to segmentation error because of complex morphology and pathologic changes of the spine. This error has not been previously characterized.Eight cadaveric lumbar spines were prepared and underwent computed tomography (CT) scanning. After disarticulation and soft-tissue removal, 5 individual vertebrae from these specimens were scanned a second time. The CT images of the full lumbar specimens were segmented twice each by 2 operators, and the images of the individual vertebrae with soft tissue removed were segmented as well. The solid models derived from these differing segmentation sessions were registered, and the distribution of distances between nearest neighboring points was calculated to evaluate the accuracy and precision of the segmentation technique.Manual segmentation yielded root-mean-square errors below 0.39 mm for accuracy, 0.33 mm for intrauser precision, and 0.35 mm for interuser precision. Furthermore, the 95th percentile of all distances was below 0.75 mm for all analyses of accuracy and precision.These findings indicate that such models are highly accurate and that a high level of intrauser and interuser precision can be achieved. The magnitude of the error presented here should inform the design and interpretation of future studies using manual segmentation techniques to derive models of the lumbar spine.

BACKGROUND CONTEXT: Nucleus replacement devices are intended to replace or augment the pathologic intervertebral disc, particularly in the early stages of the degenerative cascade. In order to evaluate the clinical viability of these devices, it is necessary to conduct tests simulating potential failure modes in the physiologic setting in addition to bench-top mechanical device testing and traditional in vitro flexibility evaluation. PURPOSE: To evaluate the compressive failure loads of lumbar functional spinal units (FSU) following augmentation with an injectiable in situ cured hydrogel. STUDY DESIGN/SETTING: In vitro biomechanical study. PATIENT SAMPLE: Twenty-three functional spinal units derived from 12 human lumbar segments. OUTCOME MEASURES: Compressive failure load. METHODS: After screening available specimens for advanced degeneration based on computed tomography scans, 23 lumbar FSU were prepared for testing from 12 full lumbar segments. Each FSU underwent injection with the nucleus augmentation gel and removal of all posterior elements by transection of the pedicles. Eleven FSU were randomly selected to the Annulectomy subgroup and subjected to a circumferential outer annulectomy. Each of the 23 FSU was then subjected to compressive load to failure at a rate of 0.1 mm/sec on a compression load frame (MTS 858 Bionix, Eden Prairie, MN). Specimens were loaded at this constant rate until an increase in load was no longer achieved in spite of further displacement or until axial displacement of 6 mm was reached. The maximum load achieved during testing was defined as the failure load. RESULTS: The average failure load for the specimens in the Annulectomy group was 3761 N (SD 1728, Range [1772, 8156]). The average failure load for the specimens without annulectomy was 4636 N (SD 2142, Range [1557, 9134]). A group-wise t-test was conducted between the two treatment groups, and a significant difference was not detected (p50.29). CONCLUSIONS: Surprisingly a difference in compressive failure load could not be detected between treatment groups in spite of the removal of the entire outer annulus in the Annulectomy group. The predominant mode of failure within the Annulectomy group was extrusion of the native nucleus and/or nucleus augmentation mass through the remaining annulus. Five of the 11 specimens failed in this manner. None of the specimens with a fully intact annulus failed in this mode, but rather, failed by visible fracture of the vertebral body or expulsion of the nuclear mass through the inferior or superior endplate. In order for potential failure modes of nucleus augmentation devices to be fully elucidated, further study investigating device migration and extrusion under various modes of loading must be evaluated. Additionally, further studies investigating the influence of bone density and other degenerative characteristics should be conducted. FDA DEVICE/DRUG STATUS: Hydrogel (Not approved for this indication).

The authors report the case of DYT1-positive primary generalized dystonia refractory to medical management that was successfully treated with continuous deep brain stimulation of the internal segment of the globus pallidus. Prior studies have shown that neuromusculoskeletal deficits can remain permanent if early surgical intervention is not undertaken. The authors report prolonged efficacy and safety over a 10-year period in a 28-year-old man.