Introduction: In Japan, cervical total disc replacement (TDR) was approved in 2017. However, because of its short history, no comparative study between cervical TDR and anterior cervical discectomy with fusion (ACDF) has been conducted in the country. Therefore, we examined and compared the surgical outcomes of TDR and ACDF for one-level cervical degenerative diseases.

Methods: In total, 50 patients who had received anterior surgeries for one-level cervical degenerative diseases were investigated. Among them, 25 underwent TDR (Prestige LP; Medtronic), whereas the other 25 patients underwent ACDF. ACDF samples were selected from cases conducted before the approval of TDR (−2017.9) and were retrospectively judged to be indicated for TDR. Before and at 1 year after surgery, clinical and radiological outcomes were evaluated.

Results: No significant differences in terms of patient demographics between the two groups were observed. A longer operative time was observed in the TDR group than in the ACDF group. Postoperatively, no differences in the Japanese Orthopaedic Association score for cervical myelopathy (C-JOA) score, neck pain visual analog scale, C2-7 angle, and C2-7 range of motion (ROM) were determined. TDR tended to show better neck disability index (NDI) scores postoperatively when compared with ACDF. The local angle at operative level was larger in ACDF. In TDR, the local ROMs were maintained postoperatively; however, in ACDF, the local ROM at the operative level was decreased, and the local ROMs at adjacent levels were increased postoperatively. In the TDR group, although heterotopic ossification was observed in 11 patients (44.0%), and anterior bone loss was identified in 14 patients (56.0%), these issues did not affect surgical outcomes.

Conclusions: Conclusively, no differences in terms of C-JOA score and neck pain between patients treated through TDR and ACDF were observed. However, a trend of better NDI scores was identified with TDR. While TDR maintained postoperative ROMs, ACDF showed an increase in the local ROMs at adjacent levels.

Introduction: The purpose of this study was to clarify how many cases surgeons need to experience to pass the learning phase of robotic-assisted spine surgery using the cumulative sum (CUSUM) analysis.

Methods: A retrospective review was conducted on the initial 50 consecutive patients who underwent robotic-assisted pedicle screw placements with open procedures using a spine robotic system (Mazor X Stealth Edition) at a single center from April 2021 to January 2022. There were 19 male and 31 female patients with a mean age of 58.7 (range, 13-86) years. To split the surgeries into the early and late phases using the CUSUM analysis of screw insertion time, we compared the screw insertion time, the robot setting time, the registration time, and the operation time in the early and late phases.

Results: The screw insertion time, the robot setting time, and the registration time declined as the number of surgical cases increased. The operation time did not decline as the number of surgical cases increased. The learning curve for screw insertion time can be separated into two stages based on the CUSUM analysis. The first 23 cases were in the early phase, and the later 27 cases were in the late phase. The mean screw insertion time was reduced from 3.2 min in the first 23 cases to 2.7 min in the subsequent 27 cases. The robot setting time and registration time in the late phase were also significantly shorter than those in the early phase.

Conclusions: The screw insertion time, robot setting time, and registration time decreased with experience. After 23 cases, surgeons passed the learning phase of robotic-assisted spine surgery and became more proficient.

Introduction: The aim of this study was to investigate the association of methicillin-resistant coagulase-negative staphylococci (MRCNS) on preoperative skin and surgical site infections (SSIs) in patients undergoing spinal surgery.

Methods: A total of 507 cases (239 males and 268 females; mean age: 56.1 years) were included in this retrospective study, using prospectively collected data. All patients underwent skin culturing of the surgical site preoperatively. To identify independent risk factors for SSIs as the dependent variable, sequential multivariate logistic regression analyses were conducted. Age, sex, body mass index, presence of rheumatoid arthritis (RA), steroid uses, the American Society of Anesthesiologists Physical Status (ASA-PS) ≥3, MRCNS-positivity on skin bacterial culture, instrumentation, and Japanese Orthopedic Association (JOA) score were used as independent variables.

Results: Preoperatively, MRCNS was detected from skin culture in 50 (9.9%) cases. The frequency of RA, steroid uses, and ASA-PS ≥3 was significantly higher in MRCNS-positive cases than in MRCNS-negative cases. There were 21 (4.1%) post-spinal surgery SSI cases. Multivariate logistic regression analyses revealed that JOA scores (odds ratio (OR), 0.864; 95% confidence interval (CI), 0.764-0.977) and MRCNS-positivity (OR, 5.060; 95% CI, 1.787-14.323) were significantly associated with SSIs.

Conclusions: Preoperatively, the incidence of MRCNS was 9.9%; it was the most common cause of postoperative SSIs. MRCNS-positivity was the most associated factor for SSIs.

Introduction: Recently, the cases of elderly individuals with spinal cord injuries are increasing in Japan. For individuals with spinal cord injury, regaining the ability to walk independently after an injury is one of the most important aspects of rehabilitation. Nevertheless, instead of age-optimized programs, uniform rehabilitation programs are currently provided to all patients because there is no information available for predicting prognosis based on age at the time of injury. This study aimed to elucidate the effect of age at the time of injury on the walking ability of patients with incomplete cervical spinal cord injury.

Methods: Of the 1,195 patients registered in the Japan single-center study for spinal cord injury database, those hospitalized within 28 days after injury, followed up for >180 days, had a cervical spinal cord injury, and had a lower extremity motor score of ≥42 points were examined. Patients were stratified into three groups according to the age at the time of injury (≤59, 60-69, or ≥70 years). The walking ability scores and independence levels of mobility were compared; these data were evaluated based on indoor mobility (item 12) and outdoor mobility (item 14) in the Spinal Cord Independence Measure III and Walking Index for Spinal Cord Injury II. All comparisons used data at discharge.

Results: The walking ability scores and independence levels of mobility were significantly lower in the group aged ≥70 years than those in the remaining two groups.

Conclusions: In patients with cervical spinal cord injuries with the same limb function, if the age at the time of injury was ≥70 years, the decline in physical function due to aging exerted a substantial effect on walking ability.

Introduction: The number of patients with degenerative cervical myelopathy (DCM) requiring surgical treatment has markedly increased in today's aging society. Such patients often exhibit impaired activities of daily living because of motor dysfunction as well as neuropathic pain (NeP). Although many studies have demonstrated the safety and efficacy of surgical treatment for DCM, residual postoperative NeP has not been well described. Therefore, this study aimed to identify the predictors of postoperative NeP improvement in patients with DCM.

Methods: This retrospective study included 92 outpatients with postoperative chronic NeP (≥3 months) related to DCM. Data were obtained from clinical information, magnetic resonance imaging (MRI) findings, and patient-based questionnaires using the Neuropathic Pain Symptom Inventory (NPSI) and the Brief Scale for Psychiatric Problems in Orthopaedic Patients. Univariate and multivariate analyses were performed for patients with NPSI improvement rates <30% and ≥30% to identify prognostic factors.

Results: Among 92 patients, 61 (66.3%) had residual NeP, with a low improvement rate even after surgery. The independent negative prognostic factors for NeP improvement after surgery were older age at operation (odds ratio (OR): 0.932), longer symptom duration before surgery (OR: 0.589), and higher preoperative NPSI score (OR: 0.932). The cut-off value of symptom duration before surgery for postoperative NeP improvement was 1 year. By contrast, the preoperative Japanese Orthopaedic Association score and MRI findings, including signal intensity change and the degree of spinal cord compression, were not associated with postoperative NeP improvement. Moreover, even in patients with an NPSI improvement rate ≥30%, the NPSI subscores for deep pain and paresthesia/dysesthesia remained high.

Conclusions: Discrepancies between physician- and image-based assessments and patient-based assessments were identified as factors associated with improvement in postoperative NeP. Our findings are important for both spine surgeons and patients to manage patient expectations with respect to recovery during the postoperative course.

Introduction: Although previous studies reported the clinical significance of drains in lumbar surgery, their role in and effects on the clinical outcomes of cervical spine surgery remain unclear. The present study compared the clinical outcomes of cervical laminoplasty (CLP) using a closed suction drain (CSD) and closed nonsuction drain (CNSD).

Methods: Prospectively recorded surgical data on consecutive patients who underwent CLP at a single institution between 2014 and 2020 and were followed up for at least 1 year were examined. CSD was used prior to January 2018, and CNSD has since been employed. One hundred patients who underwent surgery before and after the change in drain type (the CSD and CNSD groups, respectively) were selected for analysis. Primary outcome measures were the drainage amount, blood count, and fluid collection at the surgical site defined by magnetic resonance images. The Japanese Orthopaedic Association (JOA) score for the cervical spine was also evaluated as a functional outcome.

Results: No significant differences were observed in demographic, baseline clinical, or surgical data between the CSD and CNSD groups. The drainage amount was significantly greater in the CSD group than in the CNSD group (224 vs. 143 mL, P<0.001). Hemoglobin and hematocrit levels were significantly decreased in the CSD group than in the CNSD group. Medium or large fluid collection was significantly more common in the CNSD group than in the CSD group. No significant differences were observed in the number of surgical site infections, the formation of symptomatic hematoma, or JOA scores between the two groups.

Conclusions: The use of CNSD in CLP decreased the drainage amount and maintained the hemoglobin level compared with that of CSD. Although no patients developed symptomatic hematoma, the amount of epidural fluid collected was larger in the CNSD group than in the CSD group.

Introduction: Pedicle screws (PSs) or lateral mass screws (LMSs) are used in posterior cervical spine fixation. The former are more firmly fixed but are associated with the risk of neurovascular injury and should be inserted using intraoperative imaging or navigation, which may prolong the surgical duration and is not feasible in all hospitals. This prospective clinical study aimed to evaluate the outcomes of LMS insertions without fluoroscopic guidance and screw loosening rates at 6 months postoperatively using computed tomography (CT).

Methods: We examined 38 patients who underwent posterior cervical spine fusion using 206 LMSs in the C3-C6 range between January 2018 and July 2021. The direction of screw insertion followed the Magerl method, and we inserted screws as bicortically as possible without intraoperative imaging. The screw position was examined using CT at 1 week postoperatively. Screw insertion angles, bicortical insertion rate, facet violation, and neurovascular injury were evaluated. Screw loosening with unicortical and bicortical screws (US and BS, respectively) was investigated using CT at 6 months postoperatively.

Results: The average LMS length was 14.1 mm. The average axial and sagittal angles were 33.9° and 29.2°, respectively. Among the 206 LMSs inserted, 167 were BS; of these, 94.6% had screw length protrusion of 0-2 mm. Facet violation was observed in 3.4% of all screws but without neurovascular injury. Six months postoperatively, loosening of 25 screws (12.1%) occurred, including 17 (18.3%) USs and 8 (8.39%) BSs. The screw loosening rate was significantly higher in US than for BS (43.6% [17/39] vs. 4.8% [8/167], P<0.01).

Conclusions: Over 80% of LMSs were inserted bicortically without intraoperative imaging. By devising the screw length selection process, we inserted for screw loosening was more common in US and more likely at the fixed end.

Introduction: Cervical spine surgery reduces falls and subsequent femoral fractures. Nonetheless, current evidence on the prevalence of cervical cord compression (CCC) and increased signal intensity (ISI) in patients with femoral fractures is limited. We aimed to determine the prevalence of CCC and ISI and characterize the physical status and imaging findings using cervical spine magnetic resonance imaging (MRI) and brain computed tomography (CT) in patients with femoral fractures.

Methods: This study included 173 patients (140 women, 33 men) with femoral fractures caused by falling, who underwent both cervical spine MRI and brain CT. CCC cases classified as grade 2 (compression of less than one-third of the spinal cord) or higher were investigated. The ISI of the severely affected intervertebral disc level was evaluated using T2-weighted MRI. Hand grip strength and myelopathic signs were also evaluated. Data analysis was performed using the χ² test, Fisher's exact test, and Student's t-test.

Results: Among the 173 patients, 83 (48.0%) had CCC, 29 (16.8%) had ISI, and 68 (39.3%) had abnormal brain CT findings. There was no ISI in patients in the non-CCC group. The patients' average age in the CCC group was significantly higher than that in the non-CCC group. There was no significant difference in the proportion of myelopathic sign and abnormal brain CT findings between the CCC and non-CCC groups or between the ISI and non-ISI groups. Bilateral hand grip strength was significantly negatively correlated with the stenosis rate (right, p=0.047; left, p=0.0018).

Conclusions: In conclusion, our study showed that patients with femoral fractures had a high frequency of cervical canal stenosis and intracranial lesions using cervical spine MRI and brain CT.

Introduction: The management of degenerative spine pathology continues to be a significant source of costs to the US healthcare system. Besides surgery, utilization of healthcare resources after spine surgery drives costs. The responsibility of managing costs is gradually shifting to patients and providers. Patient-centered predictors of healthcare utilization after elective spine surgery may identify targets for cost reduction and value creation. Therefore, our study aims to quantify patterns of healthcare utilization and identify risk factors that predict high healthcare utilization after elective spine surgery.

Methods: A total of 623 patients who underwent elective spine surgery at a tertiary academic medical center by one of three fellowship-trained orthopedic spine surgeons between 2013 and 2018 were identified in this retrospective cohort study. Healthcare utilization was quantified including advanced spine imaging, emergency and urgent care visits, hospital readmission, reoperation, PT/OT referrals, opioid prescriptions, epidural steroid injections, and pain management referrals. Patient variables, namely, the Charlson comorbidity index (CCI) and the American Society of Anesthesiologists (ASA) classification system, were assessed as potential predictors for healthcare utilization.

Results: Among all patients, a wide range of health utilization was identified. Age, body mass index, Charlson Comorbidity Index, and American Society of Anesthesiology class were identified as positive predictors of postoperative healthcare utilization including emergency department visits, spine imaging studies, opioid and nerve blocker prescriptions, inpatient rehabilitation, any referrals, and pain management referrals.

Conclusions: Markers of patient health-such as CCI and ASA class-may be used to predict healthcare utilization following elective spine surgery. Identifying at-risk patients and addressing these challenges prior to surgery is an important step to deliver efficient postoperative care.

Level of Evidence: 3

Introduction: Posterior cervical spine approaches have been associated with increased rates of wound complications compared to anterior approaches. While barbed suture wound closure for lumbar spine surgery has been shown to be safe and efficacious, there is no literature regarding its use in posterior cervical spine surgery. In a cohort of patients undergoing elective posterior cervical spine surgery, we sought to compare postoperative complication rates between barbed and traditional interrupted suture closure.

Methods: A retrospective review of demographics, past medical history, and operative and postoperative variables collected from a prospective registry between July 1, 2016, and June 30, 2020 was undertaken. All patients 18 years old and above undergoing elective posterior cervical fusion were included. The primary outcome of interest was wound complications, including surgical site infection (SSI), dehiscence, or hematoma. In addition, numerical rating scale (NRS) neck pain (NP), NRS arm pain (AP), Neck Disability Index (NDI), and operative time were collected. A variety of statistical tests were used to compare the two suture groups.

Results: Of 117 patients undergoing posterior cervical fusion, 89 (76%) were closed with interrupted suture and 28 (24%) with barbed suture. The interrupted cohort were more likely to have >1 comorbidity (p<0.001), diabetes mellitus (p=0.013), and coronary artery disease (p=0.002). No difference in postoperative wound complications between interrupted/barbed sutures was observed after univariate (OR 1.07, 95% CI: 0.27-4.25, p=0.927) and multivariable logistic regression analysis (OR 0.77, 95% CI: 0.15-4.00, p=0.756). Univariate logistic regression revealed no differences in achieving minimal clinically important difference (MCID) NRS-NP (OR 0.73, 95% CI: 0.28-1.88, p=0.508) or NRS-AP (OR 0.68, 95% CI: 0.25-1.90, p=0.464) at 3 months between suture groups. The interrupted suture group was less likely to achieve MCID NDI at 3 months (OR 0.29, 95% CI: 0.11-0.80, p=0.016).

Conclusions: Barbed suture closure in posterior cervical spine surgery does not lead to higher rates of postoperative wound complications/SSI compared to traditional interrupted fascial closure.

Introduction: Pyogenic vertebral osteomyelitis (PVO) is an uncommon but life-threatening infectious disease. Diffuse idiopathic skeletal hyperostosis (DISH) is an age-related disorder and sometimes problematic in terms of spinal instability or high mortality, especially in cases of DISH-related fracture. Meanwhile, no reports have focused on the impact of DISH on the clinical outcomes after treatment for PVO. We hypothesized that PVO occurring at DISH-related segments might contribute to poor clinical results or high mortality rates. The purpose of this study was to investigate the impact of DISH on mortality after treatment for PVO in a retrospective cohort study.

Methods: This study involved patients who were hospitalized and treated for PVO at a single institution. DISH-related PVO was defined as PVO within a segment ossified by DISH or PVO at the neighboring intervertebral level of the segment ossified by DISH. Differences in mortality between patients with DISH-related and non-DISH-related PVO were investigated.

Results: This study included 55 patients. DISH-related PVO was observed in 13 patients. The mortality rate was significantly higher in patients with DISH-related PVO than in those with non-DISH-related PVO (62% and 23%, respectively; p=0.016). Propensity score-adjusted analysis showed that DISH-related PVO was an independent risk factor for mortality (adjusted hazard ratio, 2.79; p=0.034). The survival probability was significantly shorter in patients with DISH-related PVO than in those with non-DISH-related PVO (p=0.006). PVO in which the intravertebral body was the center of involvement was significantly more common in DISH-related PVO than in non-DISH-related PVO (38% and 5%, respectively; p=0.006).

Conclusions: DISH-related PVO was associated with a higher mortality rate and shorter life expectancy than non-DISH-related PVO. Similar to advanced age, PVO at the segment ossified by DISH should be recognized as a risk factor for mortality when choosing the optimal treatment strategy.

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.

Introduction: Surgical management of degenerative lumbar spine disorders is effective at improving patient pain, disability, and quality of life; however, obtaining a durable posterolateral fusion after decompression remains a challenge. Interbody fusion technologies are viable means of improving fusion rates in the lumbar spine, specifically various graft materials including autograft, structural allograft, titanium, and polyether ether ketone. This study assesses the effectiveness of Tritanium posterolateral cage in the treatment of degenerative disk disease.

Methods: Nearest-neighbor 1:1 matched control transforaminal lumbar interbody fusion with PEEK vs. Tritanium posterior lumbar (PL) cage interbody fusion patients were identified using propensity scoring from patients that underwent elective surgery for degenerative disk diseases. Line graphs were generated to compare the trajectories of improvement in patient-reported outcomes (PROs) from baseline to 3 and 12 months postoperatively. The nominal data were compared via the χ² test, while the continuous data were compared via Student's t-test.

Results: The two groups had no difference regarding either the 3- or 12-month Euro-Qol-5D (EQ-5D), numeric rating scale (NRS) leg pain, and NRS back pain; however, the Tritanium interbody cage group had better Oswestry Disability Index (ODI) scores compared to the control group of the PEEK interbody cage at both 3 and 12 months (p=0.013 and 0.048).

Conclusions: Our results indicate the Tritanium cage is an effective alternative to the previously used PEEK cage in terms of PROs, surgical safety, and radiological parameters of surgical success. The Tritanium cohort showed better ODI scores, higher fusion rates, lower subsidence, and lower indirect costs associated with surgical management, when compared to the propensity-matched PEEK cohort.

Introduction: Adult spinal fusion surgery improves lumbar alignment and patient satisfaction. Adult spinal deformity surgery improves saggital balance not only lumbar lesion, but also at hip joint coverage. It was expected that hip joint coverage rate was improved and joint stress decreased. However, it was reported that adjacent joint disease at hip joint was induced by adult spinal fusion surgery including sacroiliac joint fixation on an X-ray study. The mechanism is still unclear. We aimed to investigate the association between lumbosacral fusion including sacroiliac joint fixation and contact stress of the hip joint.

Methods: A 40-year-old woman with intact lumbar vertebrae underwent computed tomography. A three-dimensional nonlinear finite element model was constructed from the L4 vertebra to the femoral bone with triangular shell elements (thickness, 2 mm; size, 3 mm) for the cortical bone's outer surface and 2-mm (lumbar spine) or 3-mm (femoral bone) tetrahedral solid elements for the remaining bone. We constructed the following four models: a non-fusion model (NF), a L4-5 fusion model (L5F), a L4-S1 fusion model (S1F), and a L4-S2 alar iliac screw fixation model (S2F). A compressive load of 400 N was applied vertically to the L4 vertebra and a 10-Nm bending moment was additionally applied to the L4 vertebra to stimulate flexion, extension, left lateral bending, and axial rotation. Each model's hip joint's von Mises stress and angular motion were analyzed.

Results: The hip joint's angular motion in NF, L5F, S1F, and S2F gradually increased; the S2F model presented the greatest angular motion.

Conclusions: The average and maximum contact stress of the hip joint was the highest in the S2F model. Thus, lumbosacral fusion surgery with sacroiliac joint fixation placed added stress on the hip joint. We propose that this was a consequence of adjacent joint spinopelvic fixation. Lumbar-to-pelvic fixation increases the angular motion and stress at the hip joint.

Introduction: Triangular working area otherwise known as the Kambin triangle is designated as a safe place to position the instrument during the operation, with minimal risk to exiting nerves. This study aims to improve understanding and increase the safety of various transforaminal intradiscal procedures at L3/L4, L4/L5, and L5/S1 levels.

Methods: A cross-sectional analysis involving 102 MRIs that met the inclusion criteria was obtained and analyzed at the L3/L4, L4/L5, and L5/S1 discs level. For each level, the Kambin triangle was measured. By evaluating those measurements, the viability of this method was determined.

Results: Safe working zone approach angles were consistently getting wider from L3 to S1 levels. It was statistically significant to be wider for the left side for the mean angle of lateral nucleus trajectory at the L4/L5 level and L5/S1. The entry point is at 32, 45, and 55-60 mm from the midline, and the instrument should be directed at 12°, 20°, and 27° medially for the lateral nucleus at L3/L4, L4/L5, and L5/S1, respectively. The center of the nucleus pulposus entry point is at 64, 77, and 85 mm from the midline with a medial inclination of 40°, 47°, and 52°, respectively, for L3/L4, L4/L5, and L5/S1. For the posterior nucleus pulposus, the skin should be pierced 90, 140, and 180 mm from the midline and directed medially at 53°, 61°, and 68°, respectively, for L3/L4, L4/L5, and L5/S1. The posterior annulus fibrosis entry point is 172, 355, and 450 mm with a medial inclination of 69°, 80°, and 84° at L3/L4, L4/L5, and L5/S1, respectively. The sagittal inclination is 3° cephalad at L3/L4, 10° caudally at L4/L5, and 27° caudally at L5/S1.

Conclusions: Preoperative MRI assessment is important to determine the angle of trajectory for the safe entry point for intradiscal procedure via transforaminal approach.

Introduction: Long fusion surgery for adult spinal deformity may restrict activities of daily living due to lumbar stiffness. While the Lumbar Stiffness Disability Index (LSDI) can help assess lumbar stiffness, in Asia the external validity of this questionnaire has not been sufficiently examined. We performed the psychometric evaluation and external validation of the Japanese version of the LSDI (LSDI-J).

Methods: Fifty consecutive patients (14 males and 36 females; mean age 70.6 years) who underwent lumbar fusion surgery at our institution a minimum of one year after surgery and who visited the outpatient clinic between April and May 2019, were surveyed using the LSDI-J. The mean number of fusion levels was 4.4. Cronbach's alpha coefficients were calculated for internal consistency, and the intraclass correlation coefficient (ICC) was calculated to evaluate reliability. External validity was assessed by comparisons with the Oswestry Disability Index (ODI), the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), and the lumbar range of motion (LROM) with LSDI-J scores.

Results: Cronbach's alpha coefficient was 0.652 overall, and 0.849 after excluding Question 10 due to a low response rate. The ICC was 0.824 overall and 0.851 after excluding Question 10. The correlation with the ODI was 0.684, and the correlation coefficients with each domain of the JOABPEQ ranged from −0.590 to −0.413, indicating moderate correlation. However, LROM and the LSDI-J were not correlated (r=−0.055, P=0.734).

Conclusions: The LSDI-J may not be suitable in Japan because there was no correlation with LROM, the most important factor for external validity. It may be necessary to investigate why the LSDI-J did not apply to the Japanese population in terms of lower limb function. Alternatively, a unique method may be needed to assess lumbar stiffness disability that is more suitable for actual clinical practice in Japan.

Introduction: S2 alar-iliac screw (S2AIS) insertion for lumbosacral fixation is becoming a common procedure for deformity surgeries. However, studies that have reported the anatomy and morphometric features of the pelvis for S2AIS insertion in the Japanese samples are scarce. This study aimed to elucidate the morphometric features of the pelvis regarding S2AIS insertion in the Japanese samples.

Methods: We used 60 computed tomography scans of the pelvis (30 men and 30 women). The entry point for the S2AIS was determined as 1-mm lateral and 1-mm distal to the S1 dorsal sacral foramen. We resliced the plane in which the pelvis was sectioned obliquely from this entry point to the anterior inferior iliac spine in the sagittal plane. We bilaterally placed the shortest and longest virtual S2AISs in this plane using a 4-mm margin. We analyzed the length, angle, and safety of the determined trajectory and compared these measurements according to sex and age.

Results: The median longest and shortest screw lengths were 108.1 and 103.3 mm, respectively. The median longest and shortest distances from the entry point to the sacroiliac joint were 31.2 and 28.2 mm, respectively. The median smallest and largest lateral angulations were 40.7° and 47.3°, respectively. The median angle range was 4.2°. The median caudal angulation was −2.8°. The median shortest and longest distances from the S2AISs to the acetabular roof were 23.5 and 27.4 mm, respectively. The median distance from the S2AISs to the sciatic notch was 23.1 mm. Assuming the insertion of screw with a diameter of 8 mm, S2AIS insertion was difficult in 32 of 120 (27%) screws because the dorsal cortex of the sacrum was damaged.

Conclusions: Screw length and lateral angulation were similar to those in previous studies. Insertion difficulty occurred in 27% of screws.

Introduction: The efficacy of minimally invasive surgeries for thoracolumbar flexion-distraction injuries (FDIs) has been reported, but those surgeries were monosegmental fusion surgeries of two adjacent vertebrae with bone grafts or temporary fixations using percutaneous pedicle screws (PPSs) that were at least bisegmental. Our idea was to fuse the fracture itself, not to fuse the fractured vertebra with an adjacent vertebra or to stabilize the fractured vertebra by bridging rostrally/caudally adjacent intact vertebrae, specifically when the displacement is minimal. This study aimed to present the surgical techniques of reduction and temporary monosegmental fixation of neurologically intact thoracolumbar bony FDIs using multiaxial PPSs, which can minimize the surgical invasiveness and preserve all motion segments, as well as report three cases treated with this procedure.

Technical Note: When the fracture extended from the vertebral body to the spinous process at the same level, screws were placed into the fractured vertebra rostrally to the fracture along the rostral endplate, and the caudally adjacent vertebra was instrumented beyond the fracture line. When the fracture extended from the vertebral body to the spinous process of the rostrally adjacent vertebra, screws were placed into the fractured vertebra caudally to the fracture line, and the rostrally adjacent vertebra was instrumented. The kyphotic deformity was reduced through ligamentotaxis by using MPPSs in the rostral vertebra as rigid joysticks to apply direct buttress leverage to the rostral endplate. Intraoperative blood loss was minimal. The correction of kyphotic deformity and its durability were acceptable, and the segmental range of motion of the two affected vertebrae from flexion to extension was maintained after implant removal.

Conclusions: This surgery can act as the least-invasive option for the management of thoracolumbar bony FDIs to allow early ambulation without external bracing and to preserve all the motion segments.