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Abstract DNAX-associated protein 12 kD size (DAP12) is a dominant immunoreceptor tyrosine-based activation motif (ITAM)-signaling adaptor that activates costimulatory signals essential for osteoclastogenesis. Although several DAP12-associated receptors (DARs) have been identified in osteoclasts, including triggering receptor expressed on myeloid cells 2 (TREM-2), C-type lectin member 5 A (CLEC5A), and sialic acid-binding Ig-like lectin (Siglec)-15, their precise role in the development of osteoclasts and bone remodeling remain poorly understood. In this study, mice deficient in Trem-2, Clec5a, Siglec-15 were generated. In addition, mice double deficient in these DAR genes and FcεRI gamma chain (FcR)γ, an alternative ITAM adaptor to DAP12, were generated. Bone mass analysis was conducted on all mice. Notably, Siglec-15 deficient mice and Siglec-15/FcRγ double deficient mice exhibited mild and severe osteopetrosis respectively. In contrast, other DAR deficient mice showed normal bone phenotype. Likewise, osteoclasts from Siglec-15 deficient mice failed to form an actin ring, suggesting that Siglec-15 promotes bone resorption principally by modulating the cytoskeletal organization of osteoclasts. Furthermore, biochemical analysis revealed that Sigelc-15 activates macrophage colony-stimulating factor (M-CSF)-induced Ras-associated protein-1 (RAP1)/Ras-related C3 botulinum toxin substrate 1 (Rac1) pathway through formation of a complex with p130CAS and CrkII, leading to cytoskeletal remodeling of osteoclasts. Our data provide genetic and biochemical evidence that Siglec-15 facilitates M-CSF-induced cytoskeletal remodeling of the osteoclasts.

Introduction: Epidemic preventive management during the coronavirus disease 2019 (COVID-19) pandemic may have negatively impacted perioperative outcomes in patients with traumatic spinal cord injury (SCI). However, little is known about the relationship between epidemic preventive management and delirium after traumatic SCI. Here, we clarified the predictors of delirium after SCI surgery. Methods: We retrospectively analyzed 231 patients (mean age, 66 years) who underwent SCI surgery between 2017 and 2021. Patients were categorized into the delirium and non-delirium groups. Preoperative characteristics and laboratory data related to the occurrence of delirium were assessed. During the study period, we continued early surgical intervention. However, early rehabilitation intervention was not performed in the hospital rehabilitation room from May 2020 due to epidemic preventive management, which involved performing rehabilitation on the bed for 8 days postoperatively. Results: Postoperatively, 33 (14.3%) patients experienced delirium. Univariate analysis showed that age (p

Introduction: Pneumonia is one of the leading causes of acute- and chronic-phase mortality in patients with cervical spinal cord injury (CSCI) with quadriplegia. The risk factors for chronic-phase pneumonia recurrence in CSCI are still unknown. This study aimed to investigate the incidence of pneumonia in the chronic phase after injury and to identify its risk factors. Methods: This retrospective clinical observational study included patients with CSCI with American Spinal Injury Association Impairment Scale grades of A or B admitted to our center within 72 h of CSCI injury who started treatment and were available for follow-up for at least 90 days. The patients were assessed for incidences of pneumonia and its associations with clinical characteristics, including risk factors at the time of injury. Patients in whom pneumonia developed within 30 days postadmission and those after 30 days of hospitalization were comparatively examined using univariate and multivariate analyses. Results: Pneumonia occurred in 36% of the 69 enrolled patients throughout the study period and in 20% of all patients after 30 days of hospitalization. Multivariate analysis of risk factors for pneumonia showed that atelectasis (adjusted OR [aOR], 95% confidence interval [CI]: 4.9, 1.2-20.0), enteral feeding (aOR [95% CI]: 13.3 [3.0-58.9]), mechanical ventilation (aOR [95% CI]: 4.0 [1.0-15.0]), and tracheotomy (aOR [95% CI]: 14.6 [2.3-94.6]) within 30 days of admission were significantly associated with the occurrence of pneumonia even after 30 days of hospitalization. Conclusions: The risk factors for developing pneumonia in the chronic phase were atelectasis, enteral feeding, mechanical ventilation, and tracheotomy within 30 days of hospitalization. This study suggests that treatment of atelectasis, long-term respiratory muscle rehabilitation, and training to improve swallowing function are essential to prevent the recurrence of pneumonia after 30 days of hospitalization.

Abstract Patients with ossification of the ligamentum flavum (OLF) in the lumbar spine may be at high risk of developing concomitant ossification of the entire spinal ligament, but the etiology remains unclear. We investigated the propensity for spinal ligament ossification in asymptomatic subjects with lumbar OLF using the data of 595 Japanese individuals receiving medical check-ups, including computed tomography (CT) scanning. The severity of OLF (total number of intervertebral segments with OLF) of the entire spine on CT was quantified using an OLF index. Subjects with OLF were grouped according to this index: localized OLF (n = 138), intermediate OLF (n = 70), and extensive OLF (n = 31). The proportion of subjects with lumbar OLF increased with increasing OLF index (localized 13.7%, intermediate 41.4%, and extensive 70.9%). Multiple regression analysis found that lumbar OLF index was associated with thoracic OLF index, and co-existence of ossification of the posterior longitudinal ligament (OPLL) of the thoracic and lumbar spine. This study showed that subjects with more multilevel lumbar OLF were more likely to develop multilevel thoracic OLF and to have coexisting OPLL. Patients with lumbar OLF may be a distinctive subgroup with a strong tendency to ossification of the entire spinal ligament.

Abstract Obesity and metabolic disturbances are prevalent in ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF); however, the involvement of dyslipidemia (DL) in OPLL/OLF remains uncertain. We investigated the association between dyslipidemia and OPLL/OLF using a dataset of 458 individuals receiving health screening tests, including computed tomography. Subjects were grouped according to the presence or location of OPLL/OLF: controls (no OPLL/OLF, n = 230), OLF (n = 167), cervical OPLL (n = 28), and thoracic OPLL (n = 33). They were also grouped according to the presence of dyslipidemia (DL[+], n = 215; DL[−], n = 243). The proportion of dyslipidemia in the OLF and OPLL groups was 1.6–2.2 times higher than that in the control group. The proportion of OLF and OPLL in the DL(+) group was significantly higher than that in the DL(−) group (OLF, 43% vs. 29%; cervical OPLL, 14.4% vs. 3.2%; thoracic OPLL, 11.1% vs. 3.7%). Multivariate logistic regression analysis showed an association between all ossification types and dyslipidemia. This study demonstrated an association of dyslipidemia with OPLL/OLF; further investigation on the causal relationship between dyslipidemia and ectopic spinal ligament ossification is warranted to develop a therapeutic intervention for OPLL/OLF.

Introduction: Despite perioperative risks in nonagenarian patients who undergo open spine surgery for degeneration disorder or spinal trauma being of great interest, the prevalence of complications in this group remains unclear. This study aims to examine the perioperative complications of open spine surgery in the elderly over 90 years of age. Methods: Preoperative and intraoperative characteristics including the American Society of Anesthesiologists Physical Status (ASA-PS) class, type of surgery, and complications within 30 postoperative days were retrospectively collected from the medical records of nonagenarians who underwent open spine surgery between April 2004 and July 2019 at our spine centers. Results: A total of 48 patients met the inclusion criteria of this study. All belong to ASA-PS class 2 (69%) or 3. Preoperative American Spinal Injury Association Impairment Scale grades in trauma group were grade A in 4 cases, B in 1 case, C in 5 cases, D in 11 cases, and E in 1 case. Major complications (deep surgical site infection, cardiac event, respiratory disorder, gastrointestinal hemorrhage, and renal failure) occurred in 13 cases, and the rate of overall perioperative complications was 45.8%. One patient who underwent cervical stabilization for cervical fracture dislocation died at postoperative 13 days due to respiratory disorder. The rates of major complications and overall perioperative complications were 3.6% and 14.3% in the degenerative group and 45.5% and 81.8% in the trauma group, respectively. Especially in the trauma group, respiratory disorder occurred in 7 cases, delirium in 11 cases, and urinary tract infection in 5 cases. Conclusions: Although the perioperative complication rate reached 81.8% in spinal trauma cases, the complication rate in degenerative disorders was relatively low as 14.3%. Open spine surgery for degenerative disorders can be relatively safe even in nonagenarians, whereas the risks of perioperative complications, including respiratory disorder and delirium, were high in spinal trauma cases.

Ossification of the posterior longitudinal ligament of the spine (OPLL) is an intractable disease leading to severe neurological deficits. Its etiology and pathogenesis are primarily unknown. The relationship between OPLL and comorbidities, especially type 2 diabetes (T2D) and high body mass index (BMI), has been the focus of attention; however, no trait has been proven to have a causal relationship. We conducted a meta-analysis of genome-wide association studies (GWASs) using 22,016 Japanese individuals and identified 14 significant loci, 8 of which were previously unreported. We then conducted a gene-based association analysis and a transcriptome-wide Mendelian randomization approach and identified three candidate genes for each. Partitioning heritability enrichment analyses observed significant enrichment of the polygenic signals in the active enhancers of the connective/bone cell group, especially H3K27ac in chondrogenic differentiation cells, as well as the immune/hematopoietic cell group. Single-cell RNA sequencing of Achilles tendon cells from a mouse Achilles tendon ossification model confirmed the expression of genes in GWAS and post-GWAS analyses in mesenchymal and immune cells. Genetic correlations with 96 complex traits showed positive correlations with T2D and BMI and a negative correlation with cerebral aneurysm. Mendelian randomization analysis demonstrated a significant causal effect of increased BMI and high bone mineral density on OPLL. We evaluated the clinical images in detail and classified OPLL into cervical, thoracic, and the other types. GWAS subanalyses identified subtype-specific signals. A polygenic risk score for BMI demonstrated that the effect of BMI was particularly strong in thoracic OPLL. Our study provides genetic insight into the etiology and pathogenesis of OPLL and is expected to serve as a basis for future treatment development.

Abstract Positive association between ossification of the posterior longitudinal ligament of the spine (OPLL) and obesity is widely recognized; however, few studies focused on the effects of obesity on treatment of cervical OPLL. The effects of obesity on surgical treatment of cervical OPLL were investigated by a Japanese nationwide, prospective study. Overall, 478 patients with cervical myelopathy due to OPLL were prospectively enrolled. To clarify the effects of obesity on the surgical treatment for cervical OPLL, patients were stratified into two groups, non-obese (

Abstract Background There have been no prior reports of real-time detailed records leading to complete quadriplegia immediately after fracture dislocation in high-energy trauma. Here, we report a case of cervical dislocation in which the deterioration to complete motor paralysis (modified Frankel B1) and complete recovery (Frankel E) could be monitored in real time after reduction in the hyperacute phase. Case presentation A 65-year-old man was involved in a car accident and sustained a dislocation at the C5/6 level (Allen–Ferguson classification: distractive flexion injury stage IV). His paralysis gradually deteriorated from Frankel D to C 2 hours after the injury and from Frankl C to B 5 hours after the injury. His final neurological status immediately before reduction was Frankel B1 (complete motor paralysis with sensation only in the perianal region). Reduction was completed within 6 h and 5 min after injury, and spinal fusion was subsequently performed. The patient exhibited rapid motor recovery immediately after surgery, and was able to walk independently on postoperative day 14. Conclusions This case suggests that there is a mixture of cases in which the spinal cord has not been catastrophically damaged, even if the patient has complete motor paralysis. Prompt reduction has the potential to improve neurological function in such cases.

Abstract This prospective multicenter study, established by the Japanese Ministry of Health, Labour and Welfare and involving 27 institutions, aimed to compare postoperative outcomes between laminoplasty (LM) and posterior fusion (PF) for cervical ossification of the posterior longitudinal ligament (OPLL), in order to address the controversy surrounding the role of instrumented fusion in cases of posterior surgical decompression for OPLL. 478 patients were considered for participation in the study; from among them, 189 (137 and 52 patients with LM and PF, respectively) were included and evaluated using the Japanese Orthopaedic Association (JOA) scores, the JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), and radiographical measurements. Basic demographic and radiographical data were reviewed, and the propensity to choose a surgical procedure was calculated. Preoperatively, there were no significant differences among the participants in terms of patient backgrounds, radiographical measurements (K-line or cervical alignment on X-ray, OPLL occupation ratio on computed tomography, increased signal intensity change on magnetic resonance imaging), or clinical status (JOA score and JOACMEQ) after adjustments. The overall risk of perioperative complications was found to be lower with LM (odds ratio [OR] 0.40, p = 0.006), and the rate of C5 palsy occurrence was significantly lower with LM (OR 0.11, p = 0.0002) than with PF. The range of motion (20.91° ± 1.05° and 9.38° ± 1.24°, p

Introduction: A percutaneous endoscopic transforaminal lumbar interbody fusion (PETLIF) procedure has been previously developed. During postoperative follow-up, in some patients, bone fusion occurred between opened facet joints, despite not having bone grafting in the facet joints. Here, we investigated facet fusion's frequency and tendencies following PETLIF. Methods: A retrospective analysis was conducted on a prospectively collected, nonrandomized series of patients. Forty-two patients (6 males and 36 females, average age: 69.9 years) who underwent single-level PETLIF at our hospital from February 2016 to March 2019 were included in this study. Patients were assessed with lumbar X-ray images and computed tomography (CT) prior to, immediately after, and 1 year after surgery. Results: Pseudarthrosis was not observed in any patients, and facet fusion was observed in 26 of 42 post-PETLIF patients (61.9%) by CT 1 year postoperatively. The average interfacet distance increased from 1.3 mm preoperatively to 4.5 mm postoperatively, and facet fusion was observed under the opened conditions of 3.8 mm at 1 year. Segmental lordotic angle of the fusion segment in the lumbar X-ray images was significantly larger in the facet fusion subgroup prior to surgery, immediately following surgery, and 1 year after surgery compared to the facet non-fusion group (p=0.02, p

Abstract Ossification of the posterior longitudinal ligament (OPLL) of the spine is a disease of unknown etiology occurring frequently in individuals with metabolic disturbances. Obesity has been suggested as a potential risk factor for the severity of OPLL. We aimed to investigate whether non-alcoholic fatty liver disease (NAFLD) is associated with OPLL severity. We assessed the severity of NAFLD by a liver-to-spleen (L/S) ratio on computed tomography (CT) scans of 85 symptomatic OPLL patients at a single institution in Japan. We also assessed the severity of OPLL by CT reconstruction sagittal and axial images. The prevalence of NAFLD in middle-aged patients (age

Abstract Some surgical strategies can maintain or restore thoracic kyphosis (TK); however, next-generation surgical schemes for adolescent idiopathic scoliosis (AIS) should consider anatomical corrections. A four-dimensional correction could be actively achieved by curving the rod. Thus, anatomically designed rods have been developed as notch-free, pre-bent rods for easier anatomical reconstruction. This study aimed to compare the initial curve corrections obtained using notch-free rods and manually bent, notched rods for the anatomical reconstruction of thoracic AIS. Two consecutive series of 60 patients who underwent anatomical posterior correction for main thoracic AIS curves were prospectively followed up. After multilevel facetectomy, except for the lowest instrumented segment, either notch-free or notched rods were used. Patient demographic data, radiographic measurements, and sagittal rod angles were analyzed within 1 week after surgery. Patients with notch-free rods had significantly higher postoperative TK than patients with notched rods (P

Abstract Although favourable surgical outcomes for myelopathy caused by cervical ossification of the posterior longitudinal ligament (OPLL) have been reported, factors significantly associated with post-operative neck pain attenuation still remain unclear. The primary aim of the present study was to determine factors significantly associated with post-operative neck pain attenuation in patients with cervical OPLL using a prospective multi-centre registry of surgically treated cervical OPLL. Significant postoperative neck pain reduction (50% reduction of neck pain) was achieved in 31.3% of patients. There was no significant difference in neck pain attenuation between surgical procedures. Statistical analyses with univariate analyses followed by stepwise logistic regression revealed neurological recovery as a factor having a significant positive association with post-operative neck pain attenuation (p = 0.04, odds ratio 5.68 (95% confidence interval: 1.27–22.2)). In conclusion, neurological recovery was an independent factor having a significant positive association with post-operative neck pain attenuation in patients with cervical myelopathy caused by OPLL who underwent cervical spine surgery.

Abstract Background Osteoporotic vertebral compression fractures (VCFs) are commonly observed in elderly people and can be treated by conservatively with minimal risk of complications in most cases. However, utilization of direct oral anticoagulants (DOACs) increases the risks of secondary hematoma even after insignificant trauma. The use of DOACs increased over the past decade because of their approval and recommendation for both stroke prevention in non-valvular atrial fibrillation and treatment of venous thromboembolism. It is well known that DOACs are safer anticoagulants than warfarin in terms of major and nonmajor bleeding; however, we noted an increase in the number of bleeding events associated with DOACs that required medical intervention. This report describes the first case of delayed lumbar plexus palsy due to DOAC-associated psoas hematoma after VCF to draw attention to potential risk of severe complication associated with this type of common and stable trauma. Case presentation An 83-year-old man presented with his left inguinal pain and inability to ambulate after falling from standing position and was prescribed DOACs for chronic atrial fibrillation. Computed tomography angiography revealed a giant psoas hematoma arising from the ruptured segmental artery running around fractured L4 vertebra. Because of motor weakness of his lower limbs and expansion of psoas hematoma revealed by contrast computed tomography on day 8 of his hospital stay, angiography aimed for transcatheter arterial embolization was tried, but could not demonstrate any major active extravasation; therefore spontaneous hemostasis was expected with heparin replacement. On day 23 of his stay, hematoma turned to decrease, but dysarthria and motor weakness due to left side cerebral infarction occurred. His pain improved and bone healing was achieved about 2 months later from his admission, however the paralysis of the left lower limb and aftereffects of cerebral infarction remained after 1 year. Conclusion In patients using DOACs with multiple risk factors, close attention must be taken in vertebral injury even if the fracture itself is a stable-type such as VCF, because segmental artery injury may cause massive psoas hematoma followed by lumbar plexus palsy and other complications.

Introduction Femoral nerve palsy is a rare but serious complication of kidney transplantation. We report a case of femoral nerve palsy following kidney transplantation and conduct a review of the literature on this complication. Case presentation A 35‐year‐old woman with end‐stage kidney disease, underwent kidney transplantation in the right iliac fossa. The day after the transplantation, she could not straighten her right leg. Physical examination revealed a paresis of her right quadriceps muscle. The patient’s sensation of her right thigh was also impaired. We diagnosed her with femoral nerve palsy caused by inappropriate compression from a self‐retaining retractor. Rehabilitation was started immediately. The patient’s motor weakness gradually improved, and the patient became able to walk independently 4 weeks later. However, the patient’s neuropathic pain sustained 6 months after her kidney transplantation. Conclusion The improper use of self‐retaining retractors can lead to femoral nerve palsy in patients undergoing kidney transplantation.

Abstract Background Vertebroplasty with posterior spinal fusion (VP + PSF) is one of the most widely accepted surgical techniques for treating osteoporotic vertebral collapse (OVC). Nevertheless, the effect of the extent of fusion on surgical outcomes remains to be established. This study aimed to evaluate the surgical outcomes of short- versus long-segment VP + PSF for OVC with neurological impairment in thoracolumbar spine. Methods We retrospectively collected data from 133 patients (median age, 77 years; 42 men and 91 women) from 27 university hospitals and their affiliated hospitals. We divided patients into two groups: a short-segment fusion group (S group) with 2- or 3-segment fusion (87 patients) and a long-segment fusion group (L group) with 4- through 6-segment fusion (46 patients). Surgical invasion, clinical outcomes, local kyphosis angle (LKA), and complications were evaluated. Results No significant differences between the two groups were observed in terms of neurological recovery, pain scale scores, and complications. Surgical time was shorter and blood loss was less in the S group, whereas LKA at the final follow-up and correction loss were superior in the L group. Conclusion Although less invasiveness and validity of pain and neurological relief are secured by short-segment VP + PSF, surgeons should be cautious regarding correction loss.

Introduction: Osteoporotic vertebral fracture (OVF) is the most common osteoporotic fracture, and some patients require surgical intervention to improve their impaired activities of daily living with neurological deficits. However, many previous reports have focused on OVF around the thoracolumbar junction, and the surgical outcomes of lumbar OVF have not been thoroughly discussed. We aimed to investigate the surgical outcomes for lumbar OVF with a neurological deficit. Methods: Patients who underwent fusion surgery for thoracolumbar OVF with a neurological deficit were enrolled at 28 institutions. Clinical information, comorbidities, perioperative complications, Japanese Orthopaedic Association scores, visual analog scale scores, and radiographic parameters were compared between patients with lower lumbar fracture (L3-5) and those with thoracolumbar junction fracture (T10-L2). Each patient with lower lumbar fracture (L group) was matched with to patients with thoracolumbar junction fracture (T group). Results: A total 403 patients (89 males and 314 females, mean age: 73.8 ± 7.8 years, mean follow-up: 3.9 ± 1.7 years) were included in this study. Lower lumbar OVF was frequently found in patients with lower bone mineral density. After matching, mechanical failure was more frequent in the L group (L group: 64%, T group: 39%; p < 0.001). There was no difference between groups in the clinical and radiographical outcomes, although the rates of complication and revision surgery were still high in both groups. Conclusions: The surgical intervention for OVF is effective in patients with myelopathy or radiculopathy regardless of the surgical level, although further study is required to improve clinical and radiographical outcomes. Level of evidence: Level III

Abstract Background The optimal treatment of osteoporosis after reconstruction surgery for osteoporotic vertebral fractures (OVF) remains unclear. In this multicentre retrospective study, we investigated the effects of typically used agents for osteoporosis, namely, bisphosphonates (BP) and teriparatide (TP), on surgical results in patients with osteoporotic vertebral fractures. Methods Retrospectively registered data were collected from 27 universities and affiliated hospitals in Japan. We compared the effects of BP vs TP on postoperative mechanical complication rates, implant-related reoperation rates, and clinical outcomes in patients who underwent posterior instrumented fusion for OVF. Data were analysed according to whether the osteoporosis was primary or glucocorticoid-induced. Results A total of 159 patients who underwent posterior instrumented fusion for OVF were included. The overall mechanical complication rate was significantly lower in the TP group than in the BP group (BP vs TP: 73.1% vs 58.2%, p = 0.045). The screw backout rate was significantly lower and the rates of new vertebral fractures and pseudoarthrosis tended to be lower in the TP group than in the BP group. However, there were no significant differences in lumbar functional scores and visual analogue scale pain scores or in implant-related reoperation rates between the two groups. The incidence of pseudoarthrosis was significantly higher in patients with glucocorticoid-induced osteoporosis (GIOP) than in those with primary osteoporosis; however, the pseudoarthrosis rate was reduced by using TP. The use of TP also tended to reduce the overall mechanical complication rate in both primary osteoporosis and GIOP. Conclusions The overall mechanical complication rate was lower in patients who received TP than in those who received a BP postoperatively, regardless of type of osteoporosis. The incidence of pseudoarthrosis was significantly higher in patients with GIOP, but the use of TP reduced the rate of pseudoarthrosis in GIOP patients. The use of TP was effective to reduce postoperative complications for OVF patients treated with posterior fusion.

Background and Objectives: Although full endoscopic lumbar discectomy with the transforaminal approach (FED-TF) is a minimally invasive spinal surgery for lumbar disc herniation, the lumbosacral levels present anatomical challenges when performing FED-TF surgery due to the presence of the iliac bone. Materials and Methods: In this study, we simulated whether FED-TF surgery could be safely performed on a total of 52 consecutive cases with L5–S1 or L5–L6 disc herniation using fused three-dimensional (3D) images of the lumbar nerve root on magnetic resonance imaging (MRI) created with artificial intelligence and of the lumbosacral spine and iliac on computed tomography (CT) images. Results: Thirteen of the fifty-two cases were deemed operable according to simulated FED-TF surgery without foraminoplasty using the 3D MRI/CT fusion images. All 13 cases underwent FED-TF surgery without neurological complications, and their clinical symptoms significantly improved. Conclusions: Three-dimensional simulation may allow for the assessment from multiple angles of the endoscope entry and path, as well as the insertion angle. FED-TF surgery simulation using 3D MRI/CT fusion images could be useful in determining the indications for full endoscopic surgery for lumbosacral disc herniation.

Introduction: Lumbar interbody fusion is used to treat degenerative lumbar spondylolisthesis with instability. We developed a device that safely expands a percutaneous path through Kambin's triangle and used it via a new technique: percutaneous endoscopic transforaminal lumbar interbody fusion (PETLIF). We report in this study the details and outcomes of this procedure after a one year follow-up. Methods: Twenty-five patients requiring interbody fusion for degenerative spondylolisthesis of the L4 vertebra were enrolled in this study. The procedure involved percutaneous posterior pedicle screw placement to correct spondylolisthesis. After the exterior of the L5 vertebra superior articular protrusion was shaved with a percutaneous endoscopic drill in order to expand the safe zone, the oval sleeve was inserted through Kambin's triangle and was rotated to expand the disk height and create a path toward the vertebral disk. The interbody cage was inserted against the J-shaped nerve retractor, with the exiting nerve root retracted. Indirect decompression of spinal canal stenosis was expected because the vertebral body spondylolisthesis had been corrected and the interbody distance was expanded. Thus, no direct decompression was performed posterolaterally. Results: The mean follow-up period, surgery time, and blood loss were 22.7 months, 125.4 min, and 64.8 mL, respectively. The Japanese Orthopaedic Association score improved from 13.3 to 28.0. The Roland-Morris Disability Questionnaire score improved from 10.3 to 3.3. All items were evaluated both preoperatively and one year postoperatively. Bone fusion was observed one year postoperatively in 22 out of 25 patients. Conclusions: These results demonstrate the feasibility and efficacy of PETLIF for treating degenerative lumbar spondylolisthesis. This minimally invasive procedure is useful and has wide applicability. To obtain safe and favorable results, necessary surgical techniques must be mastered, and surgical equipment, including that for neural monitoring, is required.

Introduction: The prevalence of patients with osteoporosis continues to increase in aging societies, including Japan. The first choice for managing osteoporotic vertebral compression fracture (OVF) is conservative treatment. Failure in conservative treatment for OVF may lead to non-union or vertebral collapse, resulting in neurological deficit and subsequently requiring surgical intervention. This multicenter nationwide study in Japan was conducted to comprehensively understand the outcomes of surgical treatments for OVF non-union. Methods: This multicenter, retrospective study included 403 patients (89 males, 314 females, mean age 73.8 ± 7.8 years, mean follow-up 3.9 ± 1.7 years) with neurological deficit due to vertebral collapse or non-union after OVF at T10-L5 who underwent fusion surgery with a minimum 1-year follow-up. Radiological and clinical outcomes at baseline and at the final follow-up (FU) were evaluated. Results: OVF was present at a thoracolumbar junction such as T12 (124 patients) and L1 (117 patients). A majority of OVF occurred after a minor trauma, such as falling down (55.3%) or lifting objects (8.4%). Short segment fusion, including affected vertebra, was conducted (mean 4.0 ± 2.0 vertebrae) with 256.8 minutes of surgery and 676.1 g of blood loss. A posterior approach was employed in 86.6% of the patients, followed by a combined anterior and posterior (8.7%), and an anterior (4.7%) approach. Perioperative complications and implant failures were observed in 18.1% and 41.2%, respectively. VAS scores of low back pain (74.7 to 30.8 mm) and leg pain (56.8 to 20.7 mm) improved significantly at FU. Preoperatively, 52.6% of the patients were unable to walk and the rate of non-ambulatory patients decreased to 7.5% at FU. Conclusions: This study demonstrated that substantial improvement in activity of daily living (ADL) was achieved by fusion surgery. Although there was a considerable rate of complications, fusion surgery is beneficial for elderly OVF patients with non-union.

Study Design Retrospective case-control study, level 4. Purpose To clarify the risk factors for late subaxial lesion after occipitocervical (O-C) reconstruction. We examined cases requiring fusion-segment-extended (FE) reconstruction in addition to/after O-C reconstruction. Overview of Literature Patients with rheumatoid arthritis (RA) frequently require O-C reconstruction surgery for cranio-cervical lesions. Acceptable outcomes are achieved via indirect decompression using cervical pedicle screws and occipital plate–rod systems. However, late subaxial lesions may develop occasionally following O-C reconstruction. Methods O-C reconstruction using cervical pedicle screws and occipital plate–rod systems was performed between 1994 and 2007 in 113 patients with RA. Occipito-atlanto-axial (O-C2) reconstruction was performed for 89 patients, and occipito-subaxial cervical (O-under C2) reconstruction was performed for 24 patients. We reviewed the cases of patients requiring FE reconstruction (fusion extended group, FEG) and 26 consecutive patients who did not require FE reconstruction after a follow-up of >5 years (non-fusion extended group, NEG) as controls. Results FE reconstructions were performed for nine patients at an average of 45 months (range, 24–180 months) after O-C reconstruction. Of the 89 patients, three (3%) underwent FE reconstruction in cases of O-C2 reconstruction. Of the 24 patients, five (21%) underwent FE reconstruction in cases of O-under C2 reconstruction (p=0.003, Fisher exact test). Age, sex, RA type, and neurological impairment stage were not significantly different between FEG and NEG. O-under C2 reconstruction, larger correction angle (4° per number of unfixed segment), and O-C7 angle change after O-C reconstruction were the risk factors for late subaxial lesions on radiographic assessment. Conclusions Overcorrection of angle at fusion segments requiring O-C7 angle change was a risk factor for late subaxial lesion in patients with RA with fragile bones and joints. Correction should be limited, considering the residual mobility of the cervical unfixed segments.

Introduction: Approximately 3% of osteoporotic vertebral fractures develop osteoporotic vertebral collapse (OVC) with neurological deficits, and such patients are recommended to be treated surgically. However, a proximal junctional fracture (PJFr) following surgery for OVC can be a serious concern. Therefore, the aim of this study is to identify the incidence and risk factors of PJFr following fusion surgery for OVC. Methods: This study retrospectively analyzed registry data collected from facilities belonging to the Japan Association of Spine Surgeons with Ambition (JASA) in 2016. We retrospectively analyzed 403 patients who suffered neurological deficits due to OVC below T10 and underwent corrective surgery; only those followed up for 2 years were included. Potential risk factors related to the PJFr and their cut-off values were calculated using multivariate logistic regression analysis and receiver operating characteristic (ROC) analysis. Results: Sixty-three patients (15.6%) suffered PJFr during the follow-up (mean 45.7 months). In multivariate analysis, the grade of osteoporosis (grade 2, 3: adjusted odds ratio (aOR) 2.92; p=0.001) and lower instrumented vertebra (LIV) level (sacrum: aOR 6.75; p=0.003) were independent factors. ROC analysis demonstrated that lumbar bone mineral density (BMD) was a predictive factor (area under curve: 0.72, p=0.035) with optimal cut-off value of 0.61 g/cm2 (sensitivity, 76.5%; specificity, 58.3%), but that of the hip was not (p=0.228). Conclusions: PJFr was found in 16% cases within 4 years after surgery; independent risk factors were severe osteoporosis and extended fusion to the sacrum. The lumbar BMD with cut-off value 0.61 g/cm2 may potentially predict PJFr. Our findings can help surgeons select perioperative adjuvant therapy, as well as a surgical strategy to prevent PJFr following surgery.

Abstract Background To date, there have been little published data on surgical outcomes for patients with PD with thoracolumbar OVF. We conducted a retrospective multicenter study of registry data to investigate the outcomes of fusion surgery for patients with Parkinson’s disease (PD) with osteoporotic vertebral fracture (OVF) in the thoracolumbar junction. Methods Retrospectively registered data were collected from 27 universities and their affiliated hospitals in Japan. In total, 26 patients with PD (mean age, 76 years; 3 men and 23 women) with thoracolumbar OVF who underwent spinal fusion with a minimum of 2 years of follow-up were included (PD group). Surgical invasion, perioperative complications, radiographic sagittal alignment, mechanical failure (MF) related to instrumentation, and clinical outcomes were evaluated. A control group of 296 non-PD patients (non-PD group) matched for age, sex, distribution of surgical procedures, number of fused segments, and follow-up period were used for comparison. Results The PD group showed higher rates of perioperative complications (p

Introduction: Cervical spinal cord injury without bone injury (SCIWOBI) is a common cervical injury in the elderly population and is most likely to occur at the C3/C4 level. Respiratory dysfunction (RD) related to the damage of the spinal respiratory center, which is close to the C4 segment, is one of the greatest obstacles in improving the activities of daily living of patients with severe paralysis. We evaluated the time course of RD and motor function in cervical SCIWOBI to identify effective medical strategies. Methods: We followed 54 patients (49 men, 5 women; mean age: 65 years old) who were treated for SCIWOBI at our medical center from 2011 to 2014. The patients were evaluated within 72 hours of injury and were monitored for at least 12 weeks. All patients began respiratory-muscle training the day after admission regardless of whether they were treated conservatively or surgically. The percent vital capacity (%VC), forced expiratory volume (FEV) in one second/forced vital capacity ratio (FEV 1.0%), and American Spinal Injury Association motor score (MS) were recorded at admission and again at weeks 4 and 12. We calculated the %VC rate of change and the MS improvement rate over the entire period. Results: Fifty patients (92.6%) had restrictive ventilatory impairment at admission. The %VC correlated with the upper- and lower-limb MSs at admission, and the %VC and upper- and lower-limb MSs had improved by weeks 4 and 12 after the injury. The %VC rate of change was significantly correlated with the rate of improvement in lower-limb MS throughout the entire period. Conclusions: Lung capacity decreased in SCIWOBI owing to respiratory-muscle paralysis and upper- and lower-limb motor paralyses. Lung capacity improved as the lower limbs recovered their motor function. Respiratory rehabilitation should be continued for at least 12 weeks after SCIWOBI.

Study design: A retrospective study of consecutive surgically managed cases of cervical spinal fractures and diffuse idiopathic skeletal hyperostosis (DISH) at our hospital from October 2006 to April 2016. Summary of background data: Prognostic factors have not been determined for cervical fractures in DISH. Objectives: To assess demographics, surgical techniques, and complications in cervical spinal cord injury with DISH and to evaluate factors affecting neurological prognosis. Methods: Patients’ medical records and radiographs were reviewed and analyzed for demographics, injury characteristics, surgical outcomes, perioperative complications, additional surgeries, and neurological prognosis. Neurological status was assessed by the American Spinal Injury Association (ASIA) grade at admission and discharge. Results: Of 38 patients (mean age 71.9 ± 8.8), 20 had type 1 fractures (through the disc space), 8 had type 2 (through the vertebral body), and 10 had type 3 (through disc and vertebral body). ASIA grades at admission included 14 ASIA-A, 4 ASIA-B, 7 ASIA-C, 8 ASIA-D, and 5 ASIA-E. All patients underwent posterior fusion with an average of 4.5 ± 2.5 instrumented vertebrae (range, 2–7) and six patients required secondary halo-vest fixation. Of 14 ASIA-A patients, 12 developed serious postsurgical pulmonary complications and 4 of these died within 6 months of surgery. Of the 38 patients, 13 improved more than one grade after treatment, 24 did not improve, and 1 deteriorated. In the 18 ASIA-A/B cases (complete motor paralysis), neither fracture type nor injury mechanism (e.g. a ground-level fall or high-energy trauma) correlated with neurological prognosis, but a time of 8 h or less from injury to surgery correlated significantly with an improvement from ASIA A/B to C/D ( p < 0.01, Pearson’s χ 2 test). Conclusion: Patients with complete motor paralysis after a cervical fracture with DISH may recover to partial paralysis if surgically treated within 8 h of injury.

Fourier transform infrared (FTIR) imaging is a powerful tool for the assessment of bone quality; however, it requires the preparation of thin bone sections. Conventional poly(methyl methacrylate) (PMMA) embedding for the preparation of sections takes more than two weeks and causes denaturation of the bone. Development of a quick and easy sample preparation technique without denaturation is needed for accurate clinical evaluation of fresh calcified bone using FTIR imaging. Frozen sectioning allows the quick and easy preparation of thin sections without denaturation, but it requires a substrate with good chemical resistance and improved heat shock resistance. Polypropylene (PP) film afforded both good chemical resistance and greater heat shock resistance, and the 4-μm-thick PP film coated with glue was thin enough for the IR beam to pass through it, while the optical anisotropy of infrared bands overlapping with PO43- band was negligible. The bone quality of femoral thin sections prepared by the conventional PMMA embedding and sectioning procedure (RESIN-S) or the newly developed frozen sectioning procedure (FROZEN-S) was evaluated by FTIR imaging. The mineral-to-matrix ratio and crystallinity in the RESIN-S sections were higher than those in the FROZEN-S sections, whereas the carbonate-to-phosphate ratio in the RESIN-S sections was lower than that in the FROZEN-S sections. In RESIN-S, the increased mineral-to-matrix ratio could be caused by dehydration, and the increased crystallinity and decreased carbonate-to-phosphate ratio might be consequence of dissolution of bone mineral during PMMA embedding. Therefore, the combined use of PP film coated with glue and the frozen sectioning procedure without denaturation appears well suited to the assessment of the bone quality of fresh calcified bone using FTIR imaging.

The incidence of osteoporotic fractures was estimated as nine million worldwide in 2000, with particular occurrence at the proximity of joints rich in cancellous bone. Although most of these fractures spontaneously heal, some fractures progressively collapse during the early post-fracture period. Prediction of bone fragility during progressive collapse following initial fracture is clinically important. However, the mechanism of collapse, especially the gradual loss of the height in the cancellous bone region, is not clearly proved. The strength of cancellous bone after yield stress is difficult to predict since structural and mechanical strength cannot be determined a priori. The purpose of this study was to identify whether the baseline structure and volume of cancellous bone contributed to the change in cancellous bone strength under cyclic loading. A total of fifteen cubic cancellous bone specimens were obtained from two 2-year-old bovines and divided into three groups by collection regions: femoral head, neck, and proximal metaphysis. Structural indices of each 5-mm cubic specimen were determined using micro-computed tomography. Specimens were then subjected to five cycles of uniaxial compressive loading at 0.05 mm/min with initial 20 N loading, 0.3 mm displacement, and then unloading to 0.2 mm with 0.1 mm displacement for five successive cycles. Elastic modulus and yield stress of cancellous bone decreased exponentially during five loading cycles. The decrease ratio of yield stress from baseline to fifth cycle was strongly correlated with bone volume fraction (BV/TV, r = 0.96, p < 0.01) and structural model index (SMI, r = − 0.81, p < 0.01). The decrease ratio of elastic modulus from baseline to fifth cycle was also correlated with BV/TV (r = 0.80, p < 0.01) and SMI (r = − 0.78, p < 0.01). These data indicate that structural deterioration of cancellous bone is associated with bone strength after yield stress. This study suggests that baseline cancellous bone structure estimated from adjacent non-fractured bone contributes to the cancellous bone strength during collapse.