Introduction: Cage subsidence (CS) after posterior or transforaminal lumbar interbody fusion (PLIF or TLIF) is challenging; however, its impact on health-related quality of life (HRQOL) remains unclear. This study aimed to explore the impact of CS occurrence on HRQOL and identify the risk factors in patients following PLIF or TLIF. Methods: A total of 138 patients (mean age, 67 years; follow-up period, 12 months) who underwent single-level PLIF or TLIF were retrospectively analyzed. CS was defined as >1 mm sinking of the intervertebral cage evaluated via computed tomography. The patients were divided into the CS and nonsubsidence (NS) groups. HRQOL was assessed using the Oswestry Disability Index (ODI) scores. Results: Among the 138 patients, 30 (22%) developed CS following PLIF or TLIF. All cases with TLIF surgery (n=25) involved the use of one cage. A significant difference was observed in the use of two cages between the CS and NS groups (20.0% vs. 48.1%; P=0.006). The CS group had lower occupancy rate of autograft soon after the operation than the NS groups (P=0.002), and the occupancy rate of autograft tended to decrease in the CS group compared with the NS group over time. The ODI scores improved in both groups postoperatively; however, the NS group exhibited greater improvements in ODI scores from 4 months postoperatively. The CS group had a significantly lower proportion of patients with intervertebral osseous union at 6 and 12 months postoperatively compared with the NS group (P=0.003 and P<0.001, respectively). Conclusions: The use of two intervertebral cages may enhance initial stability and reduce CS risk after PLIF. Initial intervertebral stability was crucial to preventing CS occurrence, as evidenced by the high occupancy rates of autograft in patients without CS. Surgical factors, including surgical strategy and intraoperative techniques, should be considered to prevent CS occurrence and to improve surgical outcomes and patient satisfaction.

STUDY DESIGN:A retrospective multicenter study. PURPOSE:This study aimed to examine the impact of screw loosening (SL) on health-related quality of life (HRQOL) following posterior lumbar interbody fusion (PLIF). OVERVIEW OF LITERATURE:The rising prevalence of degenerative spinal conditions has led to an increase in lumbar surgeries, including PLIF. SL after PLIF remains challenging; however, its impact on HRQOL remains unclear. METHODS:This study included 138 patients who underwent PLIF, with a mean age of 67 years and a follow-up period of 12 months. At 12 months postoperatively, lumbar computed tomography (CT) was performed to assess SL, and patients were categorized into SL and nonloosening (NL) groups accordingly. A propensity score-matched model was used to adjust for age, sex, and body mass index (BMI). Propensity score matching was performed to compare outcomes between the SL and NL groups. RESULTS:Among the 138 patients, 29 (21%) developed SL following PLIF. Preliminary analysis revealed that the patients in the SL group were older and exhibited decreased femoral neck bone mineral density, preoperative pelvic retroversion, poor whole spine alignment, and lesser improvement in HRQOL compared with the NL group. Using propensity score matching, 22 patients were selected from each group (mean age, 72 years) (C-statistic=0.78). The propensity score-matched analysis demonstrated significant differences in the preoperative pelvic tilt (25.9° vs. 17.8°, p=0.010) between the matched SL and NL groups. Furthermore, the Oswestry Disability Index scores indicated poorer improvements in the matched SL group than in the matched NL group at 9 months postoperatively (p=0.025). CONCLUSIONS:After matching, pre- and postoperative pelvic retroversion were significantly associated with SL. Patients with SL experienced significantly poorer improvement in HRQOL at 9 months postoperatively. Therefore, implementing strategies for preventing SL may enhance early postoperative HRQOL.

Background/Objectives: PhenoAge utilizes biochemical biomarkers to differentiate mortality risk in persons of the same chronological age. However, the details of the relationship between PhenoAge and lumbar spinal stenosis (LSS) remain unclear. We investigated the association between lumbar spinal stenosis (LSS) and biological age quantified by PhenoAge and PhenoAge acceleration (PhenoAgeAccel), comparing surgically treated patients with age- and BMI-matched controls. Methods: This study included 208 LSS patients who underwent surgery. The patients were categorized into four subgroups based on gender and age (≥70 years) at the time of surgery. Demographic data, blood biomarkers, body composition measurements, and Phenotypic age acceleration (PhenoAgeAccel), which was assessed by calculating the residuals from regressing PhenoAge on chronological age were compared among the groups. We also compared control groups matched for age and body mass index (BMI) for each of the four groups using medical examination data. Results: The mean age was 70.2 ± 9.3 years and the mean PhenoAgeAccel was −5.7 ± 6.5 years in the LSS group. PhenoAgeAccel was significantly lower in the control group (−8.5 ± 3.7 years) than in the LSS group, especially in young male (LSS: −2.9 ± 6.7, Control: −7.0 ± 2.8 years), old male (−4.8 ± 4.4, −6.7 ± 4.0 years), and old female (−6.9 ± 5.9, −10.8 ± 3.2 years) subgroups. In the correlation coefficient between PhenoAgeAccel and BMI, there were weak positive correlations (CC: 0.08–0.31) across all subgroups in the control group, whereas there was a weak negative correlation (CC: −0.29) in the old female subgroup in the LSS group. Conclusions: The impact of LSS on PhenoAgeAccel varied by age and gender, and the adverse effect of LSS could be particularly pronounced in elderly women with low BMIs.

Corrective spine surgery for spinal deformities, such as adolescent idiopathic scoliosis (AIS) and adult spinal deformity (ASD), aims to enhance the quality of life by addressing physical impairments. However, the extent of patient satisfaction after surgery, which includes pain management, functional recovery, and psychological contentment, exhibits considerable variation across different cultural and geographical landscapes. This review describes the influence of cultural and regional disparities on postoperative satisfaction in AIS and ASD surgery with a particular emphasis on the disparities between the US and Japan. This review underscores the intricate relationship between surgical outcomes and patient-reported satisfaction metrics. The investigation reveals significant contrasts in patient satisfaction and clinical results between these 2 countries, attributed to divergent cultural expectations, lifestyle adaptations, and perceptions of bodily image. These distinctions are crucial for healthcare professionals to recognize, as they necessitate a culturally nuanced approach to patient care. This comparative review not only enhances the understanding of patient experiences across cultures but also provides valuable guidance for physicians in customizing their strategies to align with the varied expectations of their patients, thereby improving postoperative satisfaction and overall quality of life. This review emphasizes the necessity of a tailored and culturally sensitive approach to managing spinal deformities, underscoring the need to factor in cultural and regional elements to enhance patient satisfaction and surgical outcomes.

Objectives Our hospital was newly opened in the spring of 2020 in a rural area of Japan, with a remarkably developing aging society and population decline. This study aimed to clarify and evaluate the practice of osteoporosis care in our hospital for three years since its establishment. We report a retrospective review of therapeutic interventions for osteoporosis for patients who underwent surgical treatment for non-vertebral fragility fractures in our hospital. Methods We evaluated the practice of osteoporosis intervention in patients who underwent surgery for proximal humerus fractures (PHFs), distal radius fractures (DRFs), or proximal femoral fractures (PFFs) from April 2020 to the end of March 2023. Results There were 115 surgical cases with non-vertebral fractures (10 patients with PHF, 41 patients with DRF, and 64 with PFF). Among the patients who had received osteoporosis treatment at other hospitals before the injury, only 15 (13.0%) patients had been administered therapeutic intervention for osteoporosis by other clinics or hospitals. Also, 82 (71.3%) patients were newly diagnosed with osteoporosis in our hospital after surgery according to the Japanese osteoporosis guideline. New postoperative osteoporosis interventions were administered to 39 (47.0%) patients, of which the rate was higher than the previous reports in Japan. While there was no significant difference between upper limb fracture and PFF in the percentage per young adult mean of spine areal bone marrow density (aBMD), the femoral neck aBMDs in the upper limb fracture group were significantly higher than in the PFF group. The serum total P1NP levels were significantly lower and the 25(OH)D levels were also greater in the upper limb fracture group than in the PFF group, whereas the serum TRACP-5b levels were not significantly different between the two groups. Two (1.7%) patients were affected with secondary fractures during the study period. Conclusions The rates of therapeutic intervention for osteoporosis of patients with non-vertebral fractures, especially in those with upper limb fractures, in our hospital were considered to be greater than those in the previous reports. However, the intervention rate for patients with PFFs was not much, and there was still room for improvement in our hospital concerning osteoporosis diagnosis and treatment.

Background: Although the surgical release of the sternocleidomastoid muscle (SCM) is required for residual congenital muscular torticollis (CMT), the surgical outcomes between bipolar and unipolar SCM release remained unclear. The purpose of the present study was to assess surgical outcomes after bipolar and unipolar release of SCM in adolescent/adult patients with neglected CMT. Methods: Twenty-one consecutive adolescent/adult patients with neglected CMT who underwent surgical treatment were enrolled. Clinical and radiographic outcomes were evaluated at preoperative and final follow-up. Results: The bipolar release of SCM was performed in 3 patients (B group; males, n = 1, females, n = 2) and the unipolar release of SCM in 18 patients (U group; males, n = 6, females, n = 12). The mean age at surgery was 40.0 ± 17.0 years in Group B, and that was 32.3 ± 13.1 years in Group U (p = 0.47). The mean follow-up period was 16.0 ± 5.7 months in Group B and 10.4 ± 7.6 months in Group U (p = 0.22). Cervicomandibular angle correction rates were comparable at 75.4 ± 2.4% for the B group and 73.1 ± 11.7% for the U group (p = 0.62). There was no significant difference in clinical outcome according to the modified Cheng and Tang score between the two groups (p = 0.89). No major complications arose, although one patient exhibited a transient neurological deficit of the greater auricular nerve, and one patient developed a hematoma in the B group. Conclusions: The unipolar SCM release appeared to be a non-inferiority and less invasive procedure, minimizing surgical scars and avoiding potential auricular nerve damage in adolescent/adult patients with neglected CMT.

Background:Tranexamic acid (TXA) has gained popularity in spinal surgery because of its potential to reduce blood loss. However, concerns regarding its safety and efficacy remain. This systematic review and meta-analysis aimed to evaluate the efficacy of TXA in reducing blood loss and its safety profile in spinal surgeries.Methods:A comprehensive search was conducted in electronic databases for randomized controlled trials and prospective studies evaluating the use of TXA in spinal surgery. The primary outcomes were intraoperative and total estimated blood loss (EBL), and the secondary outcomes included the incidence and types of complications associated with TXA use. Meta-analyses were performed using random-effects models.Results:Thirteen studies involving 1,213 participants were included in the meta-analysis. The use of TXA was associated with significant reductions in both intraoperative (mean difference: -46.56 mL [-73.85, -19.26], p<0.01]) and total EBL (mean difference: -210.17 mL [-284.93, -135.40], p<0.01) while also decreasing the need for blood transfusions (risk ratio: 0.68 [0.51, 0.90], p<0.01). No significant difference was found in the incidence and types of thrombotic complications when TXA was used in spinal surgery. Subgroup analysis showed consistent results in instrumentation and fusion surgery and different doses of TXA.Conclusions:TXA is effective in reducing intraoperative and overall blood loss in spinal surgery without increasing the risk of complications. These findings support the use of TXA to improve patient outcomes. However, caution should be exercised because of the heterogeneity among the included studies. Further research is needed to confirm these findings and explore potential long-term complications.

Artificial intelligence (AI) and machine learning (ML) are rapidly becoming integral components of modern healthcare, offering new avenues for diagnosis, treatment, and outcome prediction. This review explores their current applications and potential future in the field of spinal care. From enhancing imaging techniques to predicting patient outcomes, AI and ML are revolutionizing the way we approach spinal diseases. AI and ML have significantly improved spinal imaging by augmenting detection and classification capabilities, thereby boosting diagnostic accuracy. Predictive models have also been developed to guide treatment plans and foresee patient outcomes, driving a shift towards more personalized care. Looking towards the future, we envision AI and ML further ingraining themselves in spinal care with the development of algorithms capable of deciphering complex spinal pathologies to aid decision making. Despite the promise these technologies hold, their integration into clinical practice is not without challenges. Data quality, integration hurdles, data security, and ethical considerations are some of the key areas that need to be addressed for their successful and responsible implementation. In conclusion, AI and ML represent potent tools for transforming spinal care. Thoughtful and balanced integration of these technologies, guided by ethical considerations, can lead to significant advancements, ushering in an era of more personalized, effective, and efficient healthcare.

Intradural extramedullary cavernous hemangioma involving the nerve fiber is a rare clinical entity. Here, we report an extremely rare case of cavernous hemangioma that presented as an intradural extramedullary tumor involving the left S2 nerve fiber. A 28-year-old female presented with intractable left leg pain. Her lumbar magnetic resonance image showed an intradural and extramedullary neoplastic lesion at left S1-2 level. Because her symptoms had deteriorated, surgical treatment was performed. The neoplasm was involving the left S2 nerve fiber mimicking a schwannoma. The neoplasm was completely resected, and diagnosis of cavernous hemangioma was confirmed by the histopathological findings. The patient's symptoms improved after surgery, and there is no recurrence at the 1-year follow-up. To the best of our knowledge, this is the most caudal level of intradural extramedullary cavernous hemangioma involving the nerve fiber in the literatures. Complete resection was performed, and clinical outcome was favorable.

Adult spinal deformity (ASD) surgery aims to correct abnormal spinal curvature in adults, leading to improved functionality and reduced pain. However, this surgery is associated with various complications, one of which is proximal junctional failure (PJF). PJF can have a significant impact on a patient’s quality of life, necessitating a comprehensive understanding of its causes and the development of effective management strategies. This review aims to provide an in-depth understanding of PJF in ASD surgery. PJF is a complex complication resulting from a multitude of factors including patient characteristics, surgical techniques, and postoperative management. Age, osteoporosis, overcorrection of sagittal alignment, and poor bone quality are identified as significant risk factors. The clinical implications of PJF are substantial, often requiring revision surgery and causing a considerable decrease in patients’ quality of life. Prevention strategies include careful preoperative planning, appropriate patient selection, and optimization of surgical techniques. Treatment often necessitates a multifaceted approach, including surgical intervention and the management of underlying risk factors. Predictive modeling is an emerging field that may offer a promising avenue for the risk stratification of patients and individualized preventive strategies. A thorough understanding of PJF’s pathogenesis, risk factors, and clinical implications is essential for surgeons involved in ASD surgery. Current preventive measures and treatment strategies aim to mitigate the risk and manage the complications of PJF, but the complication cannot be entirely prevented. Future research should focus on the development of more effective preventive and treatment strategies, and predictive models could be valuable in this pursuit.

Pedicle or lateral mass screws, which are usually used to fix atlantoaxial instability, increase the risk of vertebral artery (VA) injury in patients with bone or arterial anomalies or osteoporotic bone. Here, we report the use of a unilateral C1 posterior arch screw-C2 laminar screw posterior fixation with a contralateral C1 lateral mass screw for VA preservation in a patient with bow hunter's syndrome (BHS). A 65-year-old male presented with recurrent loss of consciousness in the right rotational and backward-bending head positions for 1 year. Cerebral angiography in the same head position showed that the left VA was disrupted at C1/2 and the right VA was hypoplastic. The patient was diagnosed with BHS. C1-2 posterior fixation and iliac bone grafting were performed. The left VA was on the dominant side, and the VA was in a high position; thus, a C1 posterior arch screw was selected for the left side, a C1 lateral mass screw was selected for the right side, and a C2 laminar screw with O-arm navigation and a C-arm was used to prevent arterial injury. Intraoperative findings revealed no VA injury, and postoperative computed tomography showed the screw at the planned site. In a patient with BHS, posterior fixation with a unilateral C1 posterior arch screw-C2 laminar screw prevented VA injury because the screw could be inserted while avoiding the VA.

The S2 alar-iliac screw (S2AIS) is commonly used for long spinal fusion as a rigid distal foundation in spinal deformity surgeries, and it is also used in percutaneous sacropelvic fixation for providing an in-line connection to the proximal spinal constructs without using offset connectors. Although the pelvic shape is different between males and females, reports on S2AIS trajectories according to gender have been scarce in the literature. In this paper, S2AIS trajectories are compared between males and females using pelvic three-dimensional computed tomography (3D-CT) in a normal Japanese population. After resetting the caudal angulation in CT-imaging plane manipulation, the angulation of S2AIS was more lateral in the axial plane and more horizontal in the coronal plane in females. Mean distances from the midline to starting points of S2AIS tended to be shorter in females, whereas mean distances from the midline to the posterior superior iliac spine was significantly longer in females. We also found that there were positive correlations between the patients' height and the maximal lengths of S2AISs, and the patients' height and minimal areas of S2AIS pathways. Our results are useful not only for conventional open spinal surgery, but also for minimally invasive spine surgery.

Background Delayed union or pseudoarthrosis after posterior lumbar interbody fusion (PLIF) is associated with poor outcomes in health-related quality of life. Therefore, it is important to achieve earlier solid fusion for a successful clinical outcome after PLIF. A few authors reported that biomechanical factors may influence spinal fusion rates. The purpose of our retrospective study was to evaluate the independent predictors of delayed osseous union related to intraoperative procedures of PLIF, and to find ways to reduce delayed osseous union. Methods This was a retrospective study of a completed trial. We reviewed 66 elderly patients with osteoporosis after PLIF (all female, mean age 71 years, follow-up period over 6 months). Lumbar computed tomography scans at 2 months postoperatively were examined for the presence of a translucent zone between autograft and endplate (more than 50% of vertebral diameter), and autograft position with bone bridging (anterior, central, or posterior). Osseous union was assessed by using computed tomography 6 months postoperatively. Results Thirty-three patients (50%) showed complete osseous union, while 33 did not. A translucent zone between autograft and endplate two months postoperatively was observed in nine patients (27%) in the union group and in 23 (70%) in the nonunion group (p<0.01). Autograft position with bone bridging two months postoperatively was anterior, central, and posterior in 17 (52%), 30 (91%), and 20 patients (61%) in the union group, and in 12 (36%), 20 (61%), and seven patients (21%) in the nonunion group (p=0.22, p<0.01, and p<0.01), respectively. Multivariate logistic regression analysis showed that the presence of a translucent zone between autograft and endplate (odds ratio, 0.101; 95% confidence interval: 0.026-0.398; p<0.01) and teriparatide administration (odds ratio, 8.810; 95% confidence interval: 2.222-34.936; p<0.01) were independently associated with osseous union after PLIF. Conclusions A translucent zone between autograft and endplate at two months postoperatively independently predicted delayed osseous union within six months after PLIF. Complete osseous union rates were higher in patients with posterior bone bridging two months postoperatively than in those without. These findings apart from preoperative predictors of osseous union might serve as indicators of how intraoperative techniques affects osseous union enhancement.

Introduction In 2018, the first Mobi-CⓇ total disk replacement (TDR) case was performed in Japan. In this study, we examined the preliminary clinical outcome of Mobi-CⓇ for degenerative cervical spine disease. Methods We examined 24 consecutive patients who underwent 1-level TDR after 2018 and followed up for more than 6 months after surgery. The evaluation criteria included age, gender, diagnosis, follow-up period, surgical level, implant size, surgery time, intraoperative bleeding volume, complications, revision surgery, imaging findings, JOA score, and various questionnaires. Results The mean age was 52.7 years, 13 males and 11 females. There were 15 cases of cervical disk herniation and 9 cases of cervical spondylosis. The mean follow-up period was 17.4 months. Surgical levels were C3/4 in 4 cases, C4/5 in 2 cases, C5/6 in 16 cases, and C6/7 in 2 cases. The mean operation time was 138.5 minutes, the amount of intraoperative bleeding was 32.1 ml, and there were no serious intraoperative complications. The range of motion of the affected level increased significantly, from 6.6 degrees preoperatively to 12.2 degrees at final follow-up. No patients required revision surgery at final follow-up, and there were no cases of heterotopic ossification or adjacent segment disease. One patient exhibited radiculopathy due to mild subsidence 1 year after surgery, and 1 had asymptomatic contact of device plates. Preoperative and final JOA scores improved from 11.7 to 15.8 points, and NRS improved from 4.3 to 1.3 points for neck pain and 4.3 to 1.7 points for arm pain. Preoperative and final NDI improved from 39.7% to 14.0%, and EQ-5D improved from 0.602 to 0.801. Conclusions The short-term treatment outcomes of Mobi-CⓇ TDR were generally favorable. Spine surgeons should comply with guidelines when introducing this procedure and strive to adopt this new technology in Japan.

Study Design. Multicenter, prospective randomized study. Objective. Evaluate the impact of weekly teriparatide (WT) and bone contact (BC) status of grafted bone in patients recovering from multilevel lumbar interbody fusion (M-LIF). Summary of Background Data. WT has been reported to significantly improve bone fusion following posterior or transforaminal interbody fusion in osteoporosis patients. Methods. Patients older than 50 years and osteoporotic were recruited. We defined the fusion of two or more consecutive intervertebral levels as M-LIF. All patients were instrumented with pedicle, iliac, or S-2 alar iliac screws after transplanting cages and autogenous bone between vertebral bodies. After surgical indication for M-LIF, the subjects were randomly allocated to receive either subcutaneous WT from 1 week to 6 months postoperatively (WT arm, N = 50) or a bisphosphonate (BP; BP arm, N = 54). Blinded radiological evaluations were performed using computed tomography (CT). Evaluation of bone fusion was performed at the intervertebral disc located at the bottom of the fixed range. The degree of bone fusion was calculated as a score from 2 to 6 points, with 2 defined as complete fusion. Bone fusion rate was also compared at 6 months postoperatively based on BC status of the grafted bone on CT immediately after surgery. Results. Mean bone fusion score at 6 months postoperatively was 3.9 points in the WT group and 4.2 points in the BP group. The bone fusion rate at 6 months postoperatively tended to be higher in the WT group (46.8% vs. 32.7% in the BP group). The 6-month postoperative fusion rate of immediately postoperative of BC+ patients was significantly higher than that of BC– patients (47.4% vs. 9.5%). Conclusion. In M-LIF, there were no significant differences in bone fusion score between WT- and BP-treated patients. In contrast, BC status immediately postoperatively had a major impact on 6-month bone fusion. Level of Evidence: 1

Study Design. Retrospective observational study. Objective. The study objectives were to: (1) determine radiographically which spinal malalignment parameters predominantly influence the risk of gastroesophageal reflux disease (GERD); (2) evaluate the outcome of GERD 2 years after surgery for adult spinal deformity (ASD); and (3) clarify key factors that influence the improvement of postoperative GERD in ASD. Summary of Background Data. Spinal deformity is reported to be involved in the pathology of GERD. Our previous study found that approximately 50% of patients treated surgically for ASD had GERD symptoms. However, the postoperative progress of GERD and the key factors that influence the improvement of postoperative GERD are largely unknown. Methods. Ninety-two patients with ASD treated with thoracolumbar corrective surgery and followed up for a minimum of 2 years were enrolled. All patients were asked to complete the Frequency Scale for Symptoms of GERD (FSSG) questionnaire preoperatively and at 1 and 2 years after surgery. GERD was diagnosed by FSSG score more than 8 points. Before, and at 1 and 2 years after surgery, full-length lateral radiographs were taken and radiographic parameters were obtained. Results. Patients were classified into two groups based on GERD symptoms, with 47 (51.1%) in the GERDthorn group. Among parameters assessed, only thoracolumbar kyphosis (TLK) was significantly greater in the GERDthorn group than in the GERD- group. The FSSG score improved significantly 1 year after surgery, but no significant difference was found between groups at 2 years. A significant correction loss of TLK was observed 2 years after surgery. There was a significant highly positive correlation between the FSSG score and TLK at 2 years after surgery. Conclusion. GERD improved with correction of the spinal deformity but significant correction loss of the TLK even within the fusion presumably due to subsidence or proximal junctional kyphosis resulted in a cessation of that improvement over time.

STUDY DESIGN This was a retrospective observational study of a cohort of consecutive patients. OBJECTIVE To compare the influence of (1) manual and (2) computer-assisted (CA) rod bending techniques on pedicle screw pull-out resulting in loosening during rod reduction and final tightening. SUMMARY OF BACKGROUND DATA Our recent study showed screw pull-out during rod reduction might be a risk factor for loosening of percutaneous pedicle screws (PPSs) postoperatively, resulting in worse postoperative back pain. We retrospectively analyzed data from 53 consecutive patients who underwent minimally invasive lumbar or thoracic spinal stabilization using intraoperative computed tomography image (CT)-guided navigation with conventional manual rod bending or CA rod bending and were followed up for 1 year. METHOD Screw pull-out length was measured on axial CT images obtained immediately after screw insertion and postoperatively. Loosening of screws and clinical outcome were evaluated radiographically, clinically, and by CT 1 year after surgery. The frequencies of screw pull-out and screw loosening between the 2 rod bending techniques were compared. Lumbar pain-related factors for both groups of patients were determined preoperatively and 1 year after surgery. RESULTS Overall, 360 pedicle screws were placed in the manual group and 124 pedicle screws were placed in the CA group. There was no significant difference in the mean age, sex, bone mineral density, mean stabilized length, or smoking habits of patients between the groups. The diameters, lengths, and trajectory angle (axial and sagittal) of the screws placed were not significantly different between the groups. Screw pull-out rate/length and loosening in the CA group was significantly lower than that in the manual group. Postoperative low back pain improved significantly in the CA group compared with that in the manual group. CONCLUSION CA bending is useful to avoid PPS pull-out during rod reduction and screw loosening postoperatively. CA bending is useful to avoid PPS pull-out during rod reduction and screw loosening postoperatively. This result might have been a factor leading to reduced postoperative back pain in the CA group, however, that future studies are need to investigate this association.

OBJECTIVE Nonunion after posterior lumbar interbody fusion (PLIF) is associated with poor long-term outcomes in terms of health-related quality of life. Biomechanical factors in the fusion segment may influence spinal fusion rates. There are no reports on the relationship between intervertebral union and the absorption of autografts or vertebral endplates. Therefore, the purpose of this retrospective study was to evaluate the risk factors of nonunion after PLIF and identify preventive measures. METHODS The authors analyzed 138 patients who underwent 1-level PLIF between 2016 and 2018 (75 males, 63 females; mean age 67 years; minimum follow-up period 12 months). Lumbar CT images obtained soon after the surgery and at 6 and 12 months of follow-up were examined for the mean total occupancy rate of the autograft, presence of a translucent zone between the autograft and endplate (more than 50% of vertebral diameter), cage subsidence, and screw loosening. Complete intervertebral union was defined as the presence of both upper and lower complete fusion in the center cage regions on coronal and sagittal CT slices at 12 months postoperatively. Patients were classified into either union or nonunion groups. RESULTS Complete union after PLIF was observed in 62 patients (45%), while nonunion was observed in 76 patients (55%). The mean total occupancy rate of the autograft immediately after the surgery was higher in the union group than in the nonunion group (59% vs 53%; p = 0.046). At 12 months postoperatively, the total occupancy rate of the autograft had decreased by 5.4% in the union group and by 11.9% in the nonunion group (p = 0.020). A translucent zone between the autograft and endplate immediately after the surgery was observed in 14 and 38 patients (23% and 50%) in the union and nonunion groups, respectively (p = 0.001). The nonunion group had a significantly higher proportion of cases with cage subsidence and screw loosening at 12 months postoperatively in comparison to the union group (p = 0.010 and p = 0.009, respectively). CONCLUSIONS A lower occupancy rate of the autograft and the presence of a translucent zone between the autograft and endplate immediately after the surgery were associated with nonunion at 12 months after PLIF. It may be important to achieve sufficient contact between the autograft and endplate intraoperatively for osseous union enhancement and to avoid excessive absorption of the autograft. The achievement of complete intervertebral union may decrease the incidence of cage subsidence or screw loosening.