Animal Model for Anterior Lumbar Interbody Fusion: A Literature Review.

Lumbar interbody fusion (LIF) is a surgical procedure for treating lumbar spinal stenosis and deformities. It removes a spinal disc and insert a cage or bone graft to promote solid fusion. Extensive research on LIF has been supported by numerous animal studies, which are being developed to enhance fusion rates and reduce the complications associated with the procedure. In particular, the anterior approach is significant in LIF research and regenerative medicine studies concerning intervertebral discs, as it utilizes the disc and the entire vertebral body. Several animal models have been used for anterior LIF (ALIF), each with distinct characteristics. However, a comprehensive review of ALIF models in different animals is currently lacking. Medium-sized and large animals, such as dogs and sheep, have been employed as ALIF models because of their suitable spine size for surgery. Conversely, small animals, such as rats, are rarely employed as ALIF models because of anatomical challenges. However, recent advancements in surgical implants and techniques have gradually allowed rats in ALIF models. Ambitious studies utilizing small animal ALIF models will soon be conducted. This review aims to review the advantages and disadvantages of various animal models, commonly used approaches, and bone fusion rate, to provide valuable insights to researchers studying the spine.

Traction Spurs in the Lumbar Spine: A Historical Overview and Future Perspectives.

Numerous studies have explored the connection between lumbar osteophytes, their pathophysiology, and instability since Macnab's 1971 report on traction spurs as an indicator of lumbar instability. This study provides a narrative historical overview of traction spurs, a classic finding that suggests lumbar instability. It summarizes the causes of anterior lumbar vertebral osteophytes, the relationship between traction spurs and lumbar spinal instability, and the clinical significance of traction spurs. Vertebral osteophytes are grouped into two categories, namely, traction spurs or claw spurs, which represent different stages of the same pathological process. Traction spurs are indicative of instability and occur in the early stage of disc degeneration, characterized by temporary dysfunction or instability. Traction spur formation following fusion surgery can predict union or nonunion, and it serves as an indicator of preoperative and postoperative segmental instability. The relationship between traction spurs and radiographic instability, as well as their association with imaging findings such as CT and MRI, has been clarified. Additionally, finite element analysis and mechanical testing have been used to investigate the significance of traction spurs. However, further research is needed to verify that traction spurs are an accurate indicator of pre- and postoperative lumbar instability.

Thick Skin on the Dorsal Spine in Osteoproliferative Disease: Ossification of the Posterior Longitudinal Ligament and Diffuse Idiopathic Skeletal Hyperostosis.

Background Although the correlation between reduced skin thickness and reduced bone density has been investigated, no study has evaluated skin thickness and osteoproliferative diseases, including ossification of the posterior longitudinal ligament (OPLL) and diffuse idiopathic skeletal hyperostosis (DISH). Methodology This retrospective cohort study consisted of 99 consecutive patients aged ≥60 years treated for spinal surgery at our hospital between January 2022 and March 2023. Skin thickness was measured at the dorsal side of the cervical, thoracic, and lumbar vertebrae on the sagittal cross-section image of whole-spine CT. Based on the median value, skin thickness was categorized into two groups based on a median thickness of 4 mm. Bone mineral density (BMD) was assessed. The sum of the vertebral body and intervertebral bridging osteophytes of the anterior longitudinal and posterior longitudinal ligament were defined as the OALL index and OPLL index. Serum levels of bone metabolism-related markers, such as tartrate-resistant acid phosphatase type 5b, procollagen I N-propeptide, 25-hydroxyvitamin D, and periostin, were measured. To assess the association between skin thickness and imaging findings, we calculated the adjusted odds ratios, adjusting for age, sex, and body mass index (BMI) and using univariate and multivariate logistic regression analyses. Results No significant differences were found in skin thickness in the three dorsal regions of the cervical, thoracic, and lumbar spine (median = 3.3 mm versus 3.5 mm versus 3.4 mm, p = 0.357) and bone metabolism-related markers. Adjusting for age, sex, and BMI, cervical, thoracic, and lumbar skin thicknesses were related to DISH, the OPLL index, and the OPLL and OPLL index, respectively. Conclusions Skin thickness did not correlate with BMD but with the amount of spinal ossification. A correlation was found between skin thickness and vertebral and intervertebral ossification; vertebral osteophytes, OPLL, and DISH may be more common in thicker skin.

Spinal magnetic resonance imaging artifacts in lumboperitoneal shunt surgery using adjustable valve implantation on the paravertebral spinal muscles.

BACKGROUND: Adjustable shunt valves that have been developed for managing hydrocephalus rely on intrinsically magnetic components ; thus, artifacts with these valves on magnetic resonance imaging (MRI) are inevitable. No studies on valve-induced artifacts in lumboperitoneal shunt (LPS) surgery have been published. Therefore, this study aimed to evaluate valve-induced artifacts in LPS. METHODS: We retrospectively reviewed all MRIs obtained between January 2023 and June 2023 in patients with an implanted Codman CERTAS Plus adjustable shunt valve (Integra Life Sciences, Princeton, New Jersey, USA). The valve was placed <1 cm subcutaneously on the paravertebral spinal muscle of the back, with its long axis perpendicular to the body axis. The scans were performed using a Toshiba Medical Systems 1.5 Tesla scanner. The in-plane artifact sizes were assessed as the maximum distance of the artifact from the expected region of the back. RESULTS: All spinal structures or spinal cords can be recognized, even with valve-induced artifacts. The median maximum valve-induced artifact distance on T1-weighted axial imaging was 25.63 mm (mean, 25.98 mm ; range, 22.24-30.94 mm). The median maximum valve-induced artifact distance on T2-weighted axial imaging was 25.56 mm (mean, 26.27 mm ; range, 21.83-29.53 mm). CONCLUSION: LPS surgery with adjustable valve implantation on paravertebral muscles did not cause valve-induced artifacts in the spine and spinal cord. We considered that LPS could simplify the postoperative care of these patients. J. Med. Invest. 71 : 154-157, February, 2024.

A new era in the management of spinal metastasis.

Despite the recent advances in cancer treatment, the incidence of patients with spinal metastases continues to grow along with the total number of cancer patients. Spinal metastases can significantly impair activities of daily living (ADL) and quality of life (QOL), compared with other types of bone metastases, as they are characterized with severe pain and paralysis caused by skeletal-related events. Reduced ADL can also lead to treatment limitations as certain anticancer agents and radiation therapy are not compatible treatments; thus, leading to a shorter life expectancy. Consequently, maintaining ADLs in patients with spinal metastases is paramount, and spine surgeons have an integral role to play in this regard. However, neurosurgeon, orthopedic and spinal surgeons in Japan do not have a proactive treatment approach to spinal metastases, which may prevent them from providing appropriate treatment when needed (clinical inertia). To overcome such endemic inertia, it is essential for 1) spine surgeons to understand and be more actively involved with patients with musculoskeletal disorders (cancer locomo) and cancer patients; 2) the adoption of a multidisciplinary approach (coordination and meetings not only with the attending oncologist but also with spine surgeons, radiologists, rehabilitation specialists, and other professionals) to preemptive treatment such as medication, radiotherapy, and surgical treatment; and 3) the integration of the latest findings associated with minimally invasive spinal treatments that have expanded the indications for treatment of spinal metastases and improved treatment outcomes. This heralds a new era in the management of spinal metastases.

Academic Engagement of Women as Orthopaedic Surgeons at the Annual Meetings of the Japanese Orthopaedic Association From 2012 to 2022.

BACKGROUND: Higher gender diversity correlates with higher patient satisfaction, higher-quality medical education, increased research productivity, and higher revenues. Although the field of Japanese orthopaedic surgery includes the lowest proportion of women and lags in gender diversity, reports on the current gender diversity status in academic activities are scarce. We investigated changes in women's participation in academic activities at the Japanese Orthopaedic Association (JOA) annual meetings over the past 11 years. METHODS: Data on the percentage of women in the JOA membership during 2012-2022 were analyzed to ascertain the proportion of women as first authors of oral and poster presentations, abstract reviewers, invited lecturers, seminar lecturers, general abstract oral chairpersons, symposium chairpersons, and speakers. Regarding the ratio of women among the JOA members during 2012-2022, we relied on data provided by the JOA. Data related to other categories were collected from the abstract book presented at the JOA Annual Meetings between 2012 and 2022. We analyzed the time trend for women's proportions using the Cochran-Armitage trend test. A p-value < 0.05 was considered statistically significant. RESULTS: During 2012-2022, the percentage of female members (4.9-6.7%), poster first authors (2.7-4.3%), abstract reviewers (0-1.5%), general abstract oral chairpersons (0-2.3%), symposium chairpersons (0-3.6%), and symposium speakers (1.6-6.8%) had increased significantly (p < 0.05). Oral first authors (2.2-4.1%), invited lecturers (0-6.8%), or seminar lecturers (0%-6.7%) showed no trend. Women engaged in academic activities at all annual association meetings did not exceed the women's proportion among the association members. CONCLUSION: Although the proportion of women members of the JOA has gradually increased and more women are involved in its annual meetings, the proportion of female presenters, invited speakers, symposiasts, and chairpersons of oral and poster presentations is generally lower than that of women as JOA members. Members should be asked to raise awareness, including more active education of women as physicians in educational institutions and the creation of positive actions to select women as physicians for more important roles (chairpersons, educational speakers, and symposiasts) in the organization of annual meetings.

Comparison of Gender Diversity Among Spine Surgeons in the Japanese Society for Spine Surgery and Related Research and the Neurospinal Society of Japan: A Descriptive Study Through Secondary Analysis of Aggregated Data.

STUDY DESIGN: This was a descriptive study through secondary analysis of aggregated data. PURPOSE: This study aimed to describe changes in women's membership in the Japanese Society for Spine Surgery and Related Research (JSSR) for orthopedic surgery and the Neurospinal Society of Japan (NSJ) for neurosurgery over the past decade and make predictions for the future. OVERVIEW OF LITERATURE: Although the ratio of women physicians in the field of spine surgery is known to be low worldwide, there is a lack of detailed surveys in Japan. METHODS: We sent emails to the JSSR and NSJ secretariats to verify membership information (gender and age) from 2013 to 2022. Using ordinary least squares, we projected the years it would take for the JSSR and NSJ to achieve a gender diversity ratio of 30%. RESULTS: In 2013, the percentage of women in JSSR and NSJ was 2.3% and 2.7%, respectively. However, after 2018, the percentage of women in NSJ will be higher than in JSSR, rising to 2.7% in JSSR and 4.7% in NSJ by 2022. It would require 101 years for the NSJ and more than 1,000 years for the JSSR to realize 30% gender diversity. CONCLUSIONS: JSSR and NSJ have low percentages of women. Improving gender diversity is an important issue for both societies, and they may collaborate on finding a good solution. Both the JSSR and NSJ societies need to actively address gender diversity and become more attractively represented in society for the next generation of spine surgeons.

Conservative management of spontaneous spinal epidural hematoma: A case report with favorable prognosis.

Sudden spinal epidural hematoma (SSEH) is relatively rare. Sudden pain from the neck to the back and subsequent extremity paralysis necessitate immediate head and cervical magnetic resonance imaging or computed tomography, keeping SSEH in mind. Although surgery is recommended for progressive paralysis, conservative treatment is indicated for mildly symptomatic cases.

Perioperative Cerebrovascular Accidents in Spine Surgery: A Retrospective Descriptive Study and A Systematic Review with Meta-Analysis.

Introduction: Perioperative cerebrovascular accidents (CVAs) related to spine surgery, although rare, can lead to significant disabilities. More studies on spine surgeries are required to identify those at risk of perioperative CVAs. The characteristics and outcomes of patients that experienced CVAs during spine surgery were assessed through a retrospective descriptive study and meta-analysis. Methods: Patients aged ≥18 years who underwent spine surgery under general anesthesia at a hospital between April 2011 and March 2023 were examined. Of the 2,391 initially identified patients, 2,346 were included after excluding 45 who underwent debridement for surgical site infections. Subsequently, a meta-analysis including the present retrospective descriptive study was conducted. Databases such as PubMed and Google Scholar were searched for original peer-reviewed articles written in English. Results: Of the 2,346 patients, 4 (0.17%) (three men, one woman) exhibited perioperative CVAs associated with spine surgery. The CVAs were diverse in nature: one case of cerebral hemorrhage resulting from dural injury during posterior occipitocervical fusion, two cases of cerebral infarctions after lumbar laminectomy and anterior thoracic fusion due to anticoagulant discontinuation, and one case of posterior reversible encephalopathy syndrome following microscopic lumbar discectomy due to gestational hypertension. The subsequent meta-analysis included three studies (n=186,860). It showed several risk factors for perioperative CVAs, including cervical level (pooled odds ratio [OR]=1.33), hypertension (pooled OR=2.27), atrial fibrillation (pooled OR=8.78), history of heart disease (pooled OR=2.47), and diabetes (pooled OR=2.13). Conclusions: It was speculated that the potential risk factors for the four perioperative CVA cases of spine surgery in this retrospective descriptive study were intraoperative dural injury, preoperative anticoagulant discontinuation, and gestational hypertension history. The meta-analysis revealed that cervical spine surgery, hypertension, atrial fibrillation, heart disease, and diabetes increased the CVA risk. This highlights the need for risk assessment, preoperative optimization, and postoperative care to reduce spine surgery-associated perioperative CVAs.

Experimental Study of Failures of the Rigid Spinal Posterior Fixation System Under Compressive Load Conditions: A Cadaver Study.

Background Many studies have been conducted on the biomechanics of the spine to elucidate the fixation properties of spinal fusion surgery and the causes of instrumentation failure. Among these studies, there are some studies on load sharing in the spine and measurement using strain gauges and pressure gauges, but there is a lack of research on axial compressive loads. Methods Axial compressive load tests were performed on human cadaveric injured lumbar vertebrae fixed with pedicle screws (PS). Both the strain generated in the PS rod and the intradiscal pressure were measured. Subsequently, the stress generated in the PS rod and the load sharing of the spine and instrumentation were calculated. Results Even when only compressive load is applied, bending stress of more than 10 times the compression stress was generated in the rod, and the stress tended to concentrate on one rod. Rod deformation becomes kyphotic, in contrast to the lordotic deformation behavior of the lumbar spine. The stress shielding rate was approximately 40%, less than half. Conclusions This study obtained basic data useful for constructing and verifying numerical simulations that are effective for predicting and elucidating the causes of dislodgement and failure of spinal implants.

Insights and preventive approaches of rod erosion in the occipital bone after complex posterior cervical spine surgery for destructive spondyloarthropathy: A case report.

RATIONALE: Complications of rod migration into the occipital bone after upper cervical fusion are very rare. No other cases have been reported, especially when associated with destructive spondyloarthropathy (DSA). The purpose of this case report is to remind clinicians of the risk of rod migration in cervical spine surgery in patients with DSA and to provide information on its causes, countermeasures, and treatment. PATIENT CONCERN: This case report presents the clinical course of a 61-year-old female patient with chronic kidney disease that required hemodialysis. DIAGNOSIS, INTERVENTION, OUTCOMES: The patient was diagnosed DSA involving the cervical spine. Initial treatment involved a halo vest, followed by anterior cervical corpectomy and fusion spanning from C5 to Th1. However, subsequent complications, including C5 fractures, kyphotic cervical alignment, and rod migration into the occipital bone, lead to multistage surgical interventions. This case highlights the challenges in managing DSA, the significance of optimal fixation strategies, and the importance of accounting for potential alignment changes. CONCLUSION: The effective management of occipital bone erosion after posterior cervical spine surgery for destructive spondyloarthropathy necessitates meticulous fixation planning, proactive rod length adjustment, preoperative assessment of the occipital position, and consideration of the compensatory upper cervical range of motion to prevent migration-related issues.

The first case of methotrexate-associated lymphoproliferative disorder in the sacrum: a case report.

Methotrexate (MTX) is a drug used for treating rheumatoid arthritis. Recently, the reported incidence of methotrexate-associated lymphoproliferative disease (MTX-LPD) has increased, especially in Japan. Extranodal involvement is observed in half of MTX-LPD cases. However, only a few spinal lesions have been reported, with none in the sacrum. Additionally, Epstein-Barr virus (EBV) infection has also been implicated in the pathogenesis of MTX-LPD. Herein, we describe the case of a 74-year-old woman with MTX-LPD in the sacral spine who complained of severe back pain and nocturnal pain. Radiographs revealed a tumour on the right wing of the sacrum and a positive EBV immunoglobulin G antibody titre. MTX-LPD was suspected based on imaging findings and a history of MTX administration. A pathological examination was performed on the CT-guided biopsy specimen. The histopathological diagnosis was MTX-LPD, and MTX was discontinued. Three months after MTX administration ended, the tumour tended to shrink, and 1 year later, significant tumour shrinkage was observed. This experience suggests that MTX-LPD can be treated by discontinuing MTX administration. Therefore, early and accurate diagnosis is required, as is avoiding unnecessary treatment such as surgery. MTX-LPD should be considered, especially in spinal origin tumours in EBV-infected patients on MTX.

Clinical and oncologic outcomes of posterior only total en bloc spondylectomy for spinal metastasis involving third lumbar vertebra: A case series.

INTRODUCTION: A posterior-only total en bloc spondylectomy (TES) of the L3 level was deemed a highly intricate surgical procedure, necessitating the preservation of the L3 nerve root to prevent neurological deterioration. Despite bilateral preservation efforts of the L3 nerve roots, neurological deterioration proved unavoidable. This study aims to present the clinical, neurologic, and oncologic outcomes of spinal metastasis patients who underwent a posterior-only approach TES, encompassing the L3 vertebra. MATERIALS AND METHODS: All patients with L3-involved spinal metastasis undergoing posterior TES between January 2018 and January 2022 were investigated. The primary outcomes considered were the local recurrence rate and manual muscle testing of the lumbar myotome. Secondary outcomes included Frankel neurological status, operative time, blood loss, perioperative and postoperative complications, and Eastern Cooperative Oncology Group score. RESULTS: Five patients with TES involving L3 (three females) met the inclusion criteria. All patients had solitary metastases (three in the lungs, 2 in the breasts). Postoperatively, all patients experienced weakness of the hip flexors, but they were able to ambulate independently 12 months after surgery. One patient exhibited adjacent segment (L2) disease progression and underwent corpectomy 18 months after TES. No local recurrences at the surgical site were detected on magnetic resonance imaging at the 1-year follow-up. CONCLUSION: Posterior-only TES for L3-involved vertebrae yielded excellent results in the local control of metastatic disease. Despite hip flexor weakness, all patients were able to regain independent ambulation after 12 months. TES can offer favorable clinical and oncological outcomes in patients with solitary spinal metastases.

Gender Diversity of the Japanese Society for Spine Surgery and Related Research Annual Meetings from 2013 to 2022.

Introduction: There are no reports that have examined the annual trends of the percentage of women who are members of the Japanese Society for Spine Surgery and Related Research (JSSR) or their roles at annual meetings. Furthermore, the status of gender diversity in the JSSR remains unclear. This study aims to identify gender diversity in the JSSR by quantifying the role of women at annual meetings over the past decade. Methods: We performed a retrospective review to explore gender role in the JSSR annual meeting by examining the meeting programs for 2013-2022. The gender ratios were surveyed each year for the following: (1) first authors of general application abstracts (oral and poster), (2) meeting guest speakers, (3) meeting moderators, and (4) program editors of the abstracts. We also investigated the availability of gender equality symposiums. Results: The percentage of women applying (1.1%-2.1%) and those who were invited as participants [guest speaker (0%-0.9%), moderator (0%-5.8%), and program editor (0%-0.6%)] at the annual JSSR meetings was low, with no significant increase over the past decade. In addition, there has never been a symposium promoting gender equality at the annual JSSR meeting. Conclusions: Our findings suggest that a strong and active role for institutional leaders and senior members to support the scholarly activities of women spine surgeons is important for adopting gender diversity in the JSSR academia. The absence of gender equality symposiums and the few invited women participants at the JSSR annual meeting may be due to a lack of gender diversity awareness among conference organizers or unconscious gender bias. Monitoring the role of women in the JSSR annual meetings may solve the gender diversity problem.

Sagittal-spinopelvic alignment improves in patients with bilateral highly dislocated hip (Crowe type IV) after subtrochanteric shortening total hip arthroplasty: A retrospective radiographic study.

In patients with bilateral highly dislocated hips (HDHs), total hip arthroplasty with subtrochanteric shortening osteotomy (S-THA) is a viable option for achieving adequate reconstruction with restoration of the anatomical hip center. This procedure has the potential to improve sagittal spinopelvic alignment (SSPA). However, reports are scarce owing to the rarity of this disease. The objective of this study is to investigate pre- and post-operative SSPA in patients with HDHs who had undergone S-THA. This retrospective radiographic study included 55 patients (54 females and 1 male; average age, 63.1 ±â€…6.9 years) who underwent S-THA. Lateral spine radiographs in the standing position were obtained pre- and post-operatively. The SSPA included lumbar lordosis (LL), sacral slope (SS), pelvic incidence (PI), and intervertebral disc (ID) angle of L1/2-L5/S. The SSPA pre- and post-S-THA was compared using a paired t test. Pearson correlation coefficient was used to assess the relationships between parameters. The mean pre- and post-operative LL and SS values were 62° and 49° (LL) and 50° and 39° (SS), respectively (P < .001). The ID angle was significantly reduced post-operatively at all levels (P < .001). The correlation coefficients between preoperative LL and SS and postoperative LL and PI were 0.81 and 0.38, respectively (P < .01). The preoperative SSPA of Crowe type IV HDHs revealed excessive pelvic anteversion and lumbar hyperlordosis, with a high correlation between LL and SS, suggesting that these alterations were compensatory changes to maintain body balance. Furthermore, in patients with HDHs and residual spinal flexibility, restoring the original pelvic morphology with S-THA may contribute to improved SSPA.