Asian Spine Journal最新文献

Study design: Single-center retrospective observational study.

Purpose: This study aimed to analyze the associated anomalies, neurological manifestations, cord signal changes, surgical outcomes, and complications of congenital atlantoaxial instability (cAAI). Additionally, we summarized the evolving treatment options and provided technical notes relevant to anatomical variations encountered, outlining a stepwise approach for diagnosis/management.

Overview of literature: AAI is predominantly congenital (approximately 73%) and often associated with various bony and vascular anomalies. These anatomical variations complicate the restoration of craniovertebral junction (CVJ) alignment and increase the risk of progressive myelopathy. Standard treatment involves reduction with or without release, followed by instrumentation. However, the optimal correction angle, extent of fixation, implant choice, surgical approach, and role of foramen magnum decompression have remained controversial.

Methods: This single-center retrospective study from a tertiary care center analyzed data collected over 8 years (2015-2023). Patients with congenital AAI were included, whereas those with traumatic, inflammatory, or infective etiologies were excluded. Of 103 AAI patients evaluated, 25 (24.27%) had congenital etiology and 78 had acquired pathology. The primary outcome variables included radiological parameters (C1-C2 angle, posterior occipitocervical angle, atlantodens interval, space available for cord, and clivocanal angle) and clinical parameters assessing neurology and function.

Results: Vascular (36%) and bony (92%) anomalies were frequent, with the most common being occipitoatlantal assimilation (68%). Moreover, 84% of the patients had cord signal intensity changes. An anomalous course and hypoplastic vertebral artery were observed in 16% of the patients each, while 7/25 patients (28%) had irreducible dislocations requiring anterior release. The average C1-C2 angle (C1C2A) correction was 20.6° (standard deviation [SD]=12.24; 95% confidence interval [CI], 15.812-25.408), whereas the average postoperative C1C2A was 22.36° (SD=5.68; CI, 20.133-24.587; p<0.05, paired t -test).

Conclusions: cAAI poses additional challenges over other forms of AAI given its corresponding abnormal bony and vascular anatomy. Thorough planning and anatomical restoration are essential for satisfactory outcomes.

Study design: A comparative cross-sectional study using histological, biochemical, and molecular analyses of ligamentum flavum (LF).

Purpose: To investigate whether LF hypertrophy in hemodialysis (HD) patients is associated with β2-microglobulin (B2M) amyloid and advanced glycation end-product (AGE) deposition, along with the receptor for AGE (RAGE)-related inflammatory activation.

Overview of literature: Lumbar spinal canal stenosis (LSCS) is common in HD patients. Although B2M amyloid is a hallmark of dialysisrelated amyloidosis, the role of the AGE-RAGE axis in LF pathology remains unclear.

Methods: LF tissues from 33 patients with LSCS (HD, n=16; non-HD, n=17) were analyzed. Amyloid deposition was evaluated using direct fast scarlet (DFS) staining and B2M immunohistochemistry. Pentosidine and carboxymethyl-lysine (CML) levels were quantified by high-performance liquid chromatography in subsets (n=6 per group). Expression of RAGE-related inflammatory genes was measured using quantitative reverse transcription-polymerase chain reaction. Comparisons were made between the HD and non-HD groups, paired comparisons of DFS-stained areas on the dorsal and ventral sides of LF were performed within the HD group.

Results: B2M amyloid deposition was observed exclusively in LF of HD group and predoninated dorsally (29.7%±8.6% vs. 11.9%±6.9%, p=0.001). Pentosidine levels were significantly higher in HD group than in non-HD group (28.5±10.6 μg/g vs. 16.1±4.2 μg/g, p=0.009), whereas CML levels didn't differ. On the dorsal side of LF, all examined RAGE-related inflammatory genes except toll-like receptor 4 was significantly upregulated in HD group; ventral expression showed no group differences. Immunohistochemical analysis demonstrated localized expression of RAGE, high-mobility group box 1, and nuclear factor-kappa B surrounding amyloid deposits.

Conclusions: LF in HD patients exhibits B2M amyloid and AGE accumulation with upregulation of RAGE-related inflammatory genes and proteins, especially on the dorsal side. LF hypertrophy in dialysis-related LSCS appears to represent an inflammatory-amyloid phenotype, indicating the AGE-B2M-RAGE pathway as a potential therapeutic target.

Study design: Systematic review and meta-analysis.

Purpose: To investigate the efficacy and safety of intradiscal mesenchymal stem cell (MSC) injection for patients with degenerative disc disease (DDD).

Overview of literature: DDD is a common cause of chronic low-back pain (CLBP). Studies have shown that MSC therapy may have the potential to reverse the degenerative process. However, the evidence remains inconclusive.

Methods: A comprehensive search of Europe PMC, Cochrane Library, Scopus, and Medline was conducted up to April 30, 2025, using relevant keywords. Randomized controlled trials (RCTs) comparing intradiscal MSC injections with sham/placebo in patients with DDD were included. Random-effects models were used to calculate the odds ratios and mean differences (MDs).

Results: Seven RCTs were included. MSC injection was associated with significantly greater reductions in Visual Analog Scale pain scores (MD, 6.67; 95% confidence interval [CI], -9.31 to -4.02; p<0.00001, I2=29%) and Oswestry Disability Index (ODI) (MD, -4.05%; 95% CI, -5.24 to -2.87; p<0.00001, I2=32%) compared with sham/placebo. The magnitude of improvement increased with longer followup. No significant differences were observed between groups in treatment-emergent adverse events (AEs), serious AEs, treatment discontinuation due to AEs, or mortality.

Conclusions: Intradiscal MSC injection appears to be a safe and effective therapy, offering modest improvements in pain and function for patients with CLBP due to DDD who do not respond to conservative treatments.

Study design: Retrospective observational study.

Purpose: To determine whether preoperative ligamentum flavum (LF) thickness at the cranial adjacent level predicts postoperative LF hypertrophy progression at the same level 1 year after posterior lumbar interbody fusion (PLIF), and whether preoperative LF thickness at L2/3 also predicts this progression.

Overview of literature: Adjacent segment disease (ASD) is a recognized complication of PLIF. LF hypertrophy at adjacent levels contributes to symptomatic ASD; however, it remains unclear whether preoperative LF thickness predicts postoperative hypertrophy progression.

Methods: This retrospective study included 51 patients with lumbar spinal stenosis who underwent PLIF and had preoperative and 1-year postoperative computed tomography scans. LF thickness was measured at the cranial adjacent level and at L2/3. Additional preoperative radiographic and clinical variables were also assessed. Patients were classified into progression and nonprogression groups based on the median change in LF thickness at the adjacent level, and intergroup comparisons were performed. Correlation analysis and linear regression with backward elimination were performed to identify predictors of LF hypertrophy progression. Sensitivity analyses using ridge and least absolute shrinkage and selection operator regression were conducted to confirm robustness.

Results: LF thickness at the cranial adjacent level increased from 3.4 mm preoperatively to 4.0 mm at 1 year (p<0.001). In univariate analysis, preoperative LF thickness at the cranial adjacent level, LF thickness at L2/3, and facet joint degeneration were associated with postoperative LF thickening. In multivariable regression, only LF thickness at L2/3 (coefficient=0.37, p<0.001) and cranial adjacent facet joint degeneration (coefficient=0.32, p=0.030) remained predictors (adjusted R2=0.27). No other preoperative variable showed an association.

Conclusions: Preoperative LF thickness at L2/3 and cranial adjacent facet degeneration predicted postoperative LF hypertrophy progression after PLIF. Both inherent predisposition and mechanical stress may contribute to adjacent-level LF thickening.

Study design: We developed a novel posterior atlantoaxial screw-rod (PASR) fixation system to manage atlantoaxial dislocation (AAD) and compared it with a conventional PASR fixation system. The novel system was designed to simplify the fixation procedure and achieve direct reduction of irreducible AAD without the need for surgical release.

Purpose: To perform a comparative assessment of clinical and radiological outcomes between our novel PASR fixation system and a conventional PASR fixation system.

Overview of literature: The current literature provides limited evidence on the efficacy of this novel PASR fixation system for managing irreducible AAD.

Methods: A novel PASR fixation system was designed to address the limitations of a conventional PASR fixation system, and it included C1 reduction screws, C2 fulcrum screws, and antirotation rods. From June 2016 to June 2021, 39 patients with AAD underwent a single posterior approach. Of these 39 patients, 21 were treated with the conventional PASR fixation system and 18 were treated with the novel PASR fixation system. The imaging and clinical data before and after the surgery were retrospectively analyzed.

Results: All 39 patients were successfully treated, and there were no vascular or neurological complications. Both groups demonstrated significant improvements in the atlantodental interval (ADI), Japanese Orthopaedic Association (JOA) score, visual analog scale pain score, and Neck Disability Index at the final follow-up. The operative time was shorter, postoperative ADI was better, and JOA score at follow-up was higher in the novel PASR group than in the conventional PASR group. No cases of implant loosening or screw fracture were observed. All patients achieved complete anatomical reduction postoperatively, and there was radiographic evidence of solid bony fusion within 12 months.

Conclusions: A posterior approach with our novel PASR fixation system is safe and effective for the treatment of AAD. Compared with a conventional PASR fixation system, our novel PASR fixation system can simplify the operation and provide a better reduction effect. This novel fixation system is expected to facilitate the procedure of atlantoaxial fixation and achieve reduction of irreducible AAD without release.

Minimally invasive spine surgery (MISS), supported by advancements in endoscopic systems, tubular retractors, lateral access corridors, image-guided navigation, and robotic assistance, has progressively expanded its role in the management of a broad spectrum of spinal disorders. These approaches were developed to limit muscular disruption and soft tissue damage while maintaining clinical and radiographic outcomes comparable to those of conventional open techniques. Current evidence across multiple surgical procedures indicates reductions in intraoperative blood loss, hospitalization duration, postoperative analgesic requirements, and time to functional recovery. Despite these advantages, MISS remains constrained by technical and procedural limitations. Restricted visualization, reduced working space, and dependence on fluoroscopy for navigation contribute to substantial operative complexity and prolonged learning curves. Procedure-specific risks persist, including increased radiation exposure during minimally invasive transforaminal lumbar interbody fusion, limited haptic feedback in endoscopic spine surgery, and neural or retroperitoneal complications during lateral interbody fusion. Although navigation and robotic platforms improve implant accuracy and the surgeon's radiation safety, high acquisition and maintenance costs, workflow integration challenges, and patients' radiation exposure continue to limit their widespread adoption. Future development will require cost-efficient technological refinement, standardized training pathways, and enhanced intraoperative feedback and decision support systems. Integration of artificial intelligence with robotic platforms is anticipated to further optimize surgical precision and workflow efficiency, supporting the continued evolution of MISS.

Study design: Experimental cadaveric anatomical study.

Purpose: This study aims to test the safe zone hypothesis for preventing vertebral artery injury as a notable complication of subaxial cervical spine pedicle screw malpositioning and determine the critical threshold at which screw malposition causes vertebral artery injury.

Overview of literature: The pedicle screw fixation is the strongest biomechanical stabilization approach in the posterior cervical region. Although it is associated with potential complications like vertebral artery injury, these complications are rarer than anticipated. Accordingly, several authors have proposed a "safe zone" within which even a malpositioned screw may displace and not injure the artery.

Methods: Five human cadavers were subjected to transpedicular screw fixation for creating lateral pedicle violation. Pre- and post-procedural anatomical measurements were obtained using computed tomography scans. Postoperatively, vertebral arteries were dissected to assess damage macroscopically and histopathologically.

Results: A significant correlation was observed between the safety margin (the combined distance of the vertebral artery from the lateral and medial walls of the transverse foramen) and the intraforaminal area occupied by screws for causing vertebral artery damage (p <0.001). The critical threshold for causing vertebral artery damage is exceeding this safety margin.

Conclusions: This study experimentally validated the "safe zone" hypothesis, confirming its presence and effectiveness. In cases of screw breach, the decision for revision surgery should be based on the patient's clinical condition and breach status (vessel displaced or injured), rather than the screw position alone. However, if a vertebral artery injury is suspected, acute intervention should be initiated promptly.

Study design: Retrospective cohort study.

Purpose: To determine whether preoperative trunk and lower limb muscle quality predicts achievement of the minimal clinically important difference (MCID) in the 6-minute walk distance (6MWD) after lumbar spinal stenosis (LSS) surgery.

Overview of literature: LSS commonly causes intermittent claudication and reduced walking ability. Previous studies have suggested that muscle quality affects postoperative recovery, but its association with clinically meaningful improvements in the 6MWD remains unclear.

Methods: This retrospective study included 150 patients aged ≥60 years who underwent decompression or fusion surgery for LSS at Okayama Rosai Hospital between April 2021 and April 2023. Preoperative assessments included demographic and surgical factors, Zurich Claudication Questionnaire (ZCQ) scores, visual analog scale scores, the 6MWD, and computed tomography-based muscle quality. The functional cross-sectional areas of the psoas major, erector spinae (ES), multifidus, gluteus maximus, and gluteus medius were quantified in Hounsfield units. Muscle quality was expressed as the low-attenuation muscle area (LAMA) ratio. Patients were classified according to whether they achieved the MCID (80 m) in the postoperative 6MWD. Logistic regression analyses were used to identify predictors of the achievement of the MCID.

Results: Among the 150 patients, 86 (57%) achieved the MCID. Univariate analysis showed that younger age, higher preoperative ZCQ scores, a shorter 6MWD, and lower LAMA ratios of all examined muscles were significantly associated with the achievement of the MCID in postoperative walking ability. In multivariate analysis, younger age (p <0.001), a shorter preoperative 6MWD (p =0.016), and a lower ES LAMA ratio (p <0.001) remained independent predictors. These results indicate that better preoperative ES muscle quality independently contributes to postoperative walking recovery in patients with LSS.

Conclusions: Preoperative younger age, shorter 6MWD, and lower ES LAMA ratio independently predicted meaningful postoperative improvement in walking. Enhancing preoperative ES muscle quality is crucial for postoperative walking recovery in patients with LSS.

Study design: Retrospective observational study.

Purpose: To determine whether objective neurological deficits in lumbar canal stenosis (LCS) correlate with the commonly used radio-logical grading systems.

Overview of literature: LCS is primarily a clinical diagnosis determined based on symptoms of neurological claudication and lower back pain, which is confirmed using radiological evidence. However, the current radiological measures of LCS do not often correlate with the clinical severity of the syndrome, particularly in terms of sensory, motor, and bladder/bowel dysfunction.

Methods: Preoperative clinical and imaging data of 100 consecutive cases of operated LCS were reviewed to determine symptom severity (using the Zurich Claudication Questionnaire [ZCQ]) and neurological dysfunction. Four radiological scores based on axial magnetic resonance imaging-Schizas's, Lee's, Miskin and Mandell's (M&M), and Menon's-were computed for each patient. The association between the severity of neurological dysfunction and radiological classification was assessed.

Results: All patients were graded as having moderate or severe grade LCS based on the ZCQ score. The Schizas score was significantly associated with motor (p=0.029) and sensory (p=0.034) deficits, and the M&M score was significantly associated with only motor deficits (p=0.012). The Lee and Menon's classifications did not show significant associations with any neurological dysfunction (Lee: motor: p=0.258, sensory: p=0.615; Menon's score: motor: p=0.1368, sensory: p=0.668).

Conclusions: Surgical decisions in LCS should not be based on imaging findings, but rather on the clinical severity of symptoms and presence of neurological dysfunction.

Study design: Retrospective study.

Purpose: To assess the revision rate of lateral lumbar interbody fusion (LLIF) with lateral plate fixation (LLIF+LP) and to evaluate the preoperative radiological parameters associated with the need for revision.

Overview of literature: LLIF is a minimally invasive option that provides indirect decompression and favorable fusion rates; however, stand-alone LLIF has been associated with substantial early revision rates. The addition of lateral plate fixation (LLIF+LP) enhances segmental stability, yet the predictors of revision following LLIF+LP remain poorly defined.

Methods: Patients who underwent LLIF+LP were categorized into two groups: non-revision and revision. Central canal stenosis, lateral recess stenosis, foraminal stenosis, facet joint degeneration, endplate Modic changes, ligamentum flavum hypertrophy (>4 mm), and fat infiltration (FI) grade of the lumbar multifidus muscle were evaluated. Clinical efficacy was determined using the Visual Analog Scale (VAS), Oswestry Disability Index (ODI), and Japanese Orthopaedic Association (JOA) scores, assessed both preoperatively and at the final follow-up.

Results: A total of 163 patients were included in the study, consisting of 144 in the non-revision group and 19 in the revision group, yielding an overall revision rate of 11.7% (19/163). Univariate and multivariate logistic regression analyses demonstrated that ligamentum flavum hypertrophy and the FI grade of the lumbar multifidus muscle were significantly associated with the revision rate (p<0.05). No significant differences were observed between the revision and non-revision groups in preoperative or postoperative patient-reported outcomes for VAS back pain, VAS leg pain, ODI, and JOA scores (p>0.05).

Conclusions: LLIF+LP surgery yields favorable outcomes for lumbar degenerative diseases with a low reoperation rate. Preoperative evaluation of ligamentum flavum hypertrophy and the FI grade of the lumbar multifidus muscle may assist in guiding surgical planning, preoperative discussions, and management of patient expectations.