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Retrospective cohort study OBJECTIVE: To investigate the long-term effects of bone cement-augmented instrumentation in multilevel lumbar fusions SUMMARY OF BACKGROUND DATA: Cement-augmented screw is one of the techniques used to reduce early mechanical failure in multilevel lumbar fusion, especially in the elderly. However, there is little information regarding the long-term effects.Fifty one patients who underwent three or more levels of lumbar fusion were divided into two groups according to bone cement-augmented screw fixation involving the upper instrumented vertebra (UIV): 22 patients (cemented group, group I) and 29 patients (non-cemented group, group II). The analysis of radiographic adjacent segment degeneration (ASD) involved patients with lumbosacral fusion showing a similar degree of osteoporosis. Radiologic ASD was defined as more than two UCLA grades of progression at 2 years postoperatively. Other sagittal parameters were analyzed and preoperative MR Pfirrmann grades for adjacent level, probably related to ASD.Even when no significant differences existed in preoperative demographic and radiographic parameters between the two groups, the postoperative kyphotic changes at 3 months were higher in the non-cemented group. In terms of long-term effects, radiologic ASD (20 patients (95.2%) in group I; 15 (53.6%) in group II) was significantly higher in the cemented group. Logistic regression analysis of radiologic ASD including other clinical and radiological parameters, postoperative PI-LL mismatch (OR 5.201, 95% CI 1.123-24.090, p = 0.035) and cement augmentation (OR 20.193, 95% CI 2.195-185.729, p = 0.008) showed a significant correlation with the development of radiologic ASD at postoperative 2 years.Although bone cement-augmented screw implantation can prevent kyphotic deformation at the proximal junction of UIV in early postoperative stages of multi-level lumbar fusion, a discreet selection of patients is required due to possible accelerated degeneration of adjacent segments.

Objective We investigated the characteristics and revision rate of junctional failure after surgical correction for thoracolumbar kyphosis in patients with ankylosing spondylitis. Methods A total of 230 patients had undergone surgical correction for thoracolumbar kyphosis from 2010 to 2019. The state of ankylosis between the uppermost instrumented vertebra (UIV) and UIV+1 and between the lowermost instrumented vertebra (LIV) and LIV−1 was analyzed using a modified Stoke ankylosing spondylitis spine score. Proximal junctional failure (PJF) and distal junctional failure (DJF) were defined as any type of symptomatic junctional failure. Results Of the 230 patients, 23 (10.0%) had developed junctional failure. Of these 23 patients, 16 had had partial ankylosis and 7 had had complete ankylosis. PJF had developed in 10 patients and DJF in 13. The most common type of junctional failure was a junctional fracture, which developed in 12 patients. PJF had developed by UIV fracture in 4 patients, UIV+1 fracture in 1 patient, and UIV+2 in 1 patient. DJF had developed by LIV fracture in 6 patients, metallic failure in 5, and progression of DJF in 2 patients. The average time to the development of PJF and DJF was 13 months and 12.4 months, respectively. All 10 patients with PJF and 7 of 13 patients with DJF (53.8%) had required reoperation. Of the 12 patients with junctional fracture, 11 (91.7%) had undergone reoperation. Conclusions Of the 23 patients with junctional failure, 16 had had immature ossification of the anterior longitudinal ligament. Therefore, to prevent junctional failure, the state of ankylosis seems to be important for selecting the fusion level after osteotomy. Once junctional failure has developed, however, reoperation should be considered owing to the stress concentration at the UIV or LIV.

The objective of this study was to investigate the incidence and risk factors of rod fractures (RFs) after a single-level lumbar pedicle subtraction osteotomy (PSO) using a side-tightening (ST) pedicle screw system.Fifty-seven consecutive patients who underwent a single-level lumbar PSO for the degenerative sagittal imbalance at a single institution were retrospectively reviewed. All surgeries were performed by a single surgeon using an ST pedicle screw system. Demographic, surgical, and radiographic data were analyzed to investigate the incidence and risk factors for RF.Seven (12.3%) patients showed RF after PSO. Four patients had bilateral RFs, and 3 patients had unilateral RFs. The location of the RF was at the PSO level in 6 of 7 patients. The ratio of adjacent interbody fusion was significantly different between the group with RF and the group without RF (16.7% vs. 74.0%, P = 0.004). The preoperative segmental angle at the PSO vertebra (-6.1° ± 5.5° vs. -1.7° ± 4.6°, P = 0.049) and postsurgical change in lumbar lordosis (48.4° ± 8.8° vs. 37.8° ± 11.9°, P = 0.033) were significantly different between the 2 groups. Risk factor analysis using stepwise logistic regression analysis revealed that the absence of an adjacent interbody cage (odds ratio = 0.011, 95% confidence interval = 0.000-0.390, P = 0.013) was a significant risk factor.The incidence of RF after a single-level lumbar PSO using the ST pedicle screw system was 12.3% in our cohort. The absence of an adjacent interbody cage was a significant risk factor for RF.

To analyze the effects of direct vertebral rotation (DVR) on radiologic outcomes in the treatment of thoracic adolescent idiopathic scoliosis after selective thoracic fusion with pedicle screw instrumentation.Adolescent idiopathic scoliosis patients with single thoracic curves (n = 110) treated by selective thoracic fusion with a minimum of 2 years of follow-up were retrospectively analyzed. The patients were separated into 2 groups: non-DVR (n = 63) and DVR (n = 47).There was a significant difference in fused segments between the non-DVR and DVR groups (P0.001). There was also a significant difference in main thoracic curve postoperatively (P = 0.001) and at the last follow-up (P = 0.006) between the non-DVR and DVR groups. However, there was no significant difference in proximal thoracic and lumbar curves postoperatively (proximal thoracic curve: P = 0.186; lumbar curve: P = 0.155) and at the last follow-up (proximal thoracic curve: P = 0.250; lumbar curve: P = 0.060) between the 2 groups. Significant improvements in the lowest instrumented vertebra tilt and disc angle were noted but then slight deteriorations in such were observed during the follow-up period in the non-DVR group. The prevalence of unsatisfactory results was 20.6% (13 of 63) in the non-DVR group and 19.1% (9 of 47) in the DVR group, with no significant difference (P = 0.522).For correcting single thoracic adolescent idiopathic scoliosis by selective thoracic fusion with pedicle screw instrumentation, the addition of DVR to the surgical procedure showed comparable radiologic outcomes compared with non-DVR procedures.

Background As the prevalence of spinal fusion surgery has increased, reliable and safe bone graft substitutes have been developed in response. Biocompatible osteoconductive polymer (BOP) has been used as a bone graft alternative for spine surgery. We present a case of cervical myelopathy due to extrusion of BOP 23 years after surgery and discuss the pathophysiology in terms of spinal fusion. Case Description A 65-year-old man presented with a 3-month history of cervical myelopathic symptoms. Twenty-three years earlier, the patient had undergone cervical surgery for a C6–7 herniated disc with the use of BOP. Imaging studies of the cervical spine showed cord compression due to extruded BOP at C6–7. He underwent corpectomy of the C7 vertebral body and removal of the BOP for the neural decompression, combined with interbody fusion by use of an iliac bone graft and plate fixation. During the operation, crumbly fibers of the BOP were easily removed. His myelopathic symptoms improved immediately after surgery. Postoperative magnetic resonance imaging also showed successful decompression of the spinal cord. Histologically, a foreign body reaction and bony degeneration were found around the synthetic fibers of the BOP. Conclusions Spine surgeons should recognize the pathophysiology of the BOP used for spine fusion surgery. Although BOP is not currently used for spinal surgery, patients undergoing previous surgery with the BOP can present with related complications. Revision surgery is recommended to remove the unincorporated BOP and achieve solid spine fusion.

Objective To compare the radiologic union rates between autogenous iliac crest bone graft (ICBG) and local bone graft in 1- to 3-level lumbar fusion. Methods We reviewed 178 consecutive patients who underwent 1- to 3-level lumbar fusion surgery because of lumbar spinal stenosis. Fusion status of the anterior or posterior column was evaluated by plain radiographs obtained at 24 months postoperatively. If at least either the anterior or posterior column was fused, that segment was regarded as having achieved fusion and was termed segment union. The definition of overall union was achieving union of all segments in a single patient. Results For each ICBG group and local bone graft group, fusion rate of the anterior and posterior column, and rate of the segments and overall union at postoperative 2 years were not different between the groups, regardless of surgery level. In the overall union rate according to the fusion level, the ICBG group showed constant overall fusion rate according to the fusion level (i.e., 96.9%, 96.9%, and 93.1% for 1-, 2-, and 3-level fusion), but tended to decrease with increasing level in the local bone graft group (100%, 95.8%, and 85.7% for 1-, 2-, and 3-level fusion, respectively) without statistically significant differences. Conclusions The union rate of 3-level fusion was not inferior to those of 1- or 2-level fusion in both ICBG and local bone graft patients. Local bone graft could be regarded as an adequate option for not only 1- or 2-level lumbar fusion but also 3-level lumbar fusion surgery.

Objective We sought to compare the radiologic outcomes for different distal fusion levels in a rigid curve with major thoracolumbar and lumbar (TL/L) adolescent idiopathic scoliosis (AIS) using rod derotation (RD) with direct vertebral rotation (DVR) after pedicle screw instrumentation (PSI). Methods This study finally enrolled 28 patients who were diagnosed with AIS in rigid curve with major TL/L curves, treated by PSI with RD and DVR and with a minimum 2-year follow-up. Patients were divided into 2 groups, L3 and L4, on the basis of the distal fusion level at the lowest instrumented vertebra (LIV) of L3 or L4. Results There was no significant difference in TL/L curve, thoracic (minor), and compensatory (caudal) curves between the L3 and L4 groups either postoperatively (P = 0.162, 0.426, and 0.762, respectively) or at the last follow-up (P = 0.952, 0.620, and 0.562, respectively). The overall prevalence of unsatisfactory results was 42.9% (12/28 patients). The prevalence of unsatisfactory results was 61.1% (11/18) in the L3 group and 10% (1/10) in the L4 group, which was significantly different (P Conclusions Unsatisfactory results occurred more often in the L3 group than in the L4 group, and unsatisfactory results had significant influence on progression of TL/L and distal compensatory curves. Such progression was closely correlated with deteriorating LIV disk angle in the L3 group. Therefore if the curve is rigid, LIV should be extended to L4 to avoid the adding-on phenomenon in the treatment of major TL/L AIS using RD with DVR after PSI.

Objective To identify clinical and radiographic features of subtypes of acute proximal junctional failures (PJFs) following correction surgery for degenerative sagittal imbalance. Methods The study included 157 patients with mean age 68.0 ± 6.3 years who underwent correction surgery for degenerative sagittal imbalance. Acute PJFs were categorized into 4 subtypes: fracture at uppermost instrumented vertebra (UIV), fracture at vertebra just proximal to UIV (UIV+1), fixation failure at UIV, and junctional subluxation. Demographic, clinical, and radiographic data were analyzed retrospectively. Results There were 18 patients with acute PJFs. PJF group had significantly lower T-score (−3.3 ± 1.1 vs. −1.9 ± 1.5) on bone densitometry and lower body mass index (BMI) (23.0 ± 3.9 kg/m2 vs. 25.6 ± 3.7 kg/m2) than non-PJF group. Radiographic parameters exhibited no significant differences. UIV fracture, UIV+1 fracture, UIV fixation failure, and junctional subluxation were observed in 5, 6, 4, and 3 patients. Fixation failure developed the earliest (median 1.3 months), followed by UIV fracture (1.5 months). UIV fracture occurred earlier than UIV+1 fracture (36 months). Patients with UIV or UIV+1 fracture had significantly lower T-scores than others. Although BMI and T-score were significant risk factors for all PJFs (P = 0.043 and P = 0.021, respectively), different risk factors for each subtype of PJFs were identified on separate risk factor analysis. Conclusions Patients with acute PJFs had lower T-score and BMI. Each subtype of PJFs had different clinical and radiographic features. Although BMI and T-score were associated with all PJFs, each subtype may have different risk factors. Identifying risk factors for each subtype of acute PJFs may help avoid it.

Objectives Osteoporotic spine fractures (OSFs) with delayed neurologic compromises (NCs) have been increasingly reported. Although several studies have addressed that the pathologic mechanism of NC involves nonunion and segmental instability, the risk factors remain unclear. Therefore, the purpose of this study was to assess the radiologic and clinical features of OSFs with delayed NC. Methods Thirty patients with delayed NC (group 1) were matched in a 1-to-1 format with 30 patients without delayed NC (group 2) by age, bone mineral density, body mass index, and medical treatment for osteoporosis. Clinical and radiologic parameters were assessed to determine the risk factors related to delayed NC. Clinical outcomes were also compared between the 2 groups. Results Neurologic compromises were presented as myelopathy in 20 patients and radiculopathy in 10 patients. Initial kyphotic angle (KA) and height loss (HL) were significantly greater in group 1 (21.6 ± 12.9 degrees vs. 10.5 ± 8.6 degrees, P = 0.0001 for KA; 55.8% ± 15.2% vs. 19.9% ± 10.9%, P = 0.0001 for HL). Fracture instability with intravertebral cleft, posterior wall involvement, midportion type of magnetic resonance classification, thoracolumbar level, and aortic calcification were significantly correlated with delayed NC. In multivariate analysis, initial HL (hazard ratio = 1.24; P = 0.012) and midportion-type fracture (hazard ratio = 14.9: P = 0.03) were the independent risk factors related to delayed NC. In addition, clinical outcomes at the last follow-up were significantly better in group 2. Conclusions Initial HL and midportion-type fracture were correlated with delayed NC following OSFs. Moreover, pre-existing stenotic lesions might be associated with delayed NC.

To compare clinical and radiographic outcomes and complications after vertebroplasty (VP) and kyphoplasty (KP) for osteoporotic vertebral fractures with severe collapse.Patients65 years old with single osteoporotic vertebral fracture (T10-L2) with severe collapse (40%) were prospectively enrolled and allocated to either KP or VP. Visual analog scale and Oswestry Disability Index were used for clinical assessment. Vertebral height loss (HL) and segmental kyphotic angle were measured radiographically at preoperative; postoperative; and 1-, 3-, 6-, and 12-month postoperative time points. Procedure-related and postoperative complications were recorded.Forty-six patients (27 with VP, 19 with KP) were enrolled. Visual analog scale and Oswestry Disability Index scores were similar at all time points in the 2 groups. Complication rates were also similar. HL and kyphotic angle were restored significantly in both groups. KP showed a better result in HL (KP group HL 20.5% ± 5.6% vs. VP group HL 29.8% ± 4.6%, P0.001). Progressive vertebral HL was observed, and patients with KP showed a greater collapse in height. At 1-year follow-up, there was no significant difference in vertebral height (KP group HL 29.8% ± 6.3% vs. VP group HL 33.0% ± 5.2%, P = 0.075).KP and VP showed similar improvements in pain and disability during treatment for osteoporotic vertebral fractures. Although vertebral height and segmental kyphotic angle were restored significantly in both groups, progressive vertebral HL was inevitable, especially after KP. This likely resulted from the difference of bone-cement interface as a consequence of balloon tamping in KP. Surgeons must consider the respective features of vertebral augmentations.