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OBJECTIVE The aim of this study was to investigate time-dependent rates and indications of unplanned reoperation and to evaluate the most common indication depending on the time interval after pedicle subtraction osteotomy (PSO) for correction of thoracolumbar kyphosis in patients with ankylosing spondylitis (AS). METHODS A total of 321 consecutive patients with AS (284 men; mean age 43.8 years) with thoracolumbar kyphosis who underwent PSO were included. Patients who underwent reoperation after the index surgery were divided according to the duration of the follow-up period. RESULTS A total of 51 patients (15.9%) underwent unplanned reoperations. The reoperation groups had greater preoperative and postoperative C7 sagittal vertical axis (SVA), and less lordotic postoperative osteotomy angle (−4.3° ± 18.6° vs −15.0° ± 13.7°, p < 0.001). The perioperative change in SVA was not significantly different between groups (−10.0 ± 7.1 cm vs −10.0 ± 5.1 cm, p = 0.970), while that in the osteotomy angle was significantly different (−22.4° ± 21.3° vs −30.0° ± 11.5°, p = 0.014). Most reoperations (45.1%; 23/51) were performed within 2 weeks of the initial operation. Within 2 weeks, the most common cause of reoperation was neurological deficit in 10 patients, with a cumulative reoperation rate of 3.2%. After 3 years, the most common complications were mechanical complications in 8 patients, accounting for 15.7% (8/51) of patients. Overall, the most common indications for reoperation were mechanical complications (17 patients; 5.3%), followed by neurological deficits (12 patients; 3.7%). CONCLUSIONS PSO may be the most effective surgical procedure for the correction of thoracolumbar kyphosis in patients with AS. However, 51 patients (15.9%) required an unplanned reoperation.

OBJECTIVE The most catastrophic symptom of proximal junctional failure (PJF) following long instrumented fusion surgery for adult spinal deformity (ASD) is neurological deficits. Although previous reports have shown that PJF usually developed during the early postoperative period, some patients showed late neurological deficits. The aim of this study was to report the incidence, characteristics, and surgical outcomes of PJF with late neurological deficits. METHODS Patients surgically treated for ASD at a single institution were retrospectively reviewed. Among them, the patients requiring revision surgery for newly developed neurological deficits at least 6 months after the initial surgery were included. Patient demographic, radiographic, surgical, and clinical data were investigated. Neurological status was assessed using the Frankel grading system. RESULTS PJF with late neurological deficits developed in 18 of 385 patients (4.7%). The mean age at the onset of neurological deficits was 72.0 ± 6.0 years, and the median time from the initial surgery was 4.5 years. The most common pathology of PJF was adjacent disc degeneration and subsequent canal stenosis (11 patients). Five patients showed disc degeneration with aseptic bone destruction. Fractures at the upper instrumented vertebra (UIV), UIV + 1, and UIV + 2 occurred in 2, 3, and 2 patients, respectively. Ossification of the yellow ligament, which had not been found at the first surgery, was identified in 6 patients. Eight patients showed improvement of their neurological deficits and 10 patients showed no improvement by the final follow-up. Perioperative major complications occurred in 8 of 18 patients. CONCLUSIONS The incidence of PJF with late neurological deficits following ASD surgery was 4.7% in this cohort. The patients showed several morphological features. After revision surgery, perioperative complications were common and the prognosis for improved neurological status was not favorable.

OBJECTIVEFew studies have addressed that dynamic sagittal imbalance can develop distal to the spinal fusion and cause sagittal malalignment, unlike proximal junctional kyphosis (PJK) in the proximal portion. The purpose of this study was to investigate risk factors between the 2 different types of postoperative sagittal imbalance after long fusion to the sacrum for the treatment of degenerative sagittal imbalance (DSI).METHODSEighty patients who had undergone surgical correction for DSI were included. Radiographic measurements included spinopelvic parameters on whole-spine plain radiographs and degeneration of paravertebral muscles on MRI. Univariate and multivariate analyses for clinical and radiological factors were conducted for respective risk factors. In subgroup analyses, the 2 different types of postoperative sagittal imbalance were directly compared.RESULTSForty patients (50%) developed postoperative sagittal imbalance; of these patients, 22 (55.0%) developed static proximal kyphosis from PJK, and 18 patients (45.0%) developed dynamic sagittal imbalance without PJK. The independent risk factors in proximal kyphosis were greater postoperative pelvic tilt (HR 1.11) and less change in sacral slope (SS) (HR 1.09), whereas there were more fusion levels (HR 3.11), less change in SS (HR 1.28), and less change in thoracic kyphosis (HR 1.26) in dynamic sagittal imbalance. Directly compared with the proximal kyphosis group, dynamic sagittal imbalance was more commonly found in patients who had less correction of sagittal parameters as well as fatty atrophy of the paravertebral muscles. Clinical outcomes in the dynamic sagittal imbalance group were superior to those in the proximal kyphosis group.CONCLUSIONSOptimal correction of sagittal alignment should be considered in long instrumented fusion for DSI, because insufficient correction might cause one of 2 different types of postoperative sagittal imbalance at different sites of decompression. Dynamic sagittal imbalance compared with proximal kyphosis was significantly associated with less correction of sagittal alignment, in conjunction with more fusion levels and degeneration of the paravertebral muscles.

OBJECTIVEThe purpose of this study was to investigate the rate of and the risk factors for surgery-related complications demonstrated on radiography after pedicle subtraction osteotomy (PSO) for thoracolumbar kyphosis in patients with ankylosing spondylitis (AS).METHODSThe authors retrospectively reviewed the medical records of 230 consecutive patients with thoracolumbar kyphosis due to AS who had undergone 1-level PSO at a single institution in the period from 2010 to 2017. The causes of surgery-related complications were divided into two types: surgical/technical failure and mechanical failure.RESULTSThe patients consisted of 20 women and 210 men, with an average age of 43.4 years. The average follow-up period was 39.0 months. The preoperative sagittal vertical axis was 18.5 ± 69.3 cm, which improved to 4.9 ± 4.6 cm after PSO. Of the 77 patients (33.5%) who experienced minor or major surgery-related complications, 56 had complications related to surgical/technical failure (overall incidence 24.3%) and 21 had complications related to mechanical failure (overall incidence 9.1%). Fourteen patients (6.1%) underwent reoperation. However, among the 77 patients with complications, the rate of revision surgery was 18.2%. The most common radiological complications were as follows: sagittal translation in 24 patients, coronal imbalance in 20, under-correction in 8, delayed union in 8, and distal junctional failure and kyphosis in 8. The most common causes of reoperation were coronal imbalance in 4 patients, symptomatic malposition of pedicle screws in 3, and distal junctional failure in 3. Delayed union was statistically correlated with posterior sagittal translation (p = 0.007).CONCLUSIONSPSO can provide acceptable radiographic outcomes for the correction of thoracolumbar kyphosis in patients with AS. However, a high incidence of surgery-related complications related to mechanical failure and surgical technique can develop. Thorough radiographic investigation before and during surgery is needed to determine whether complete ossification occurs along the anterior and posterior longitudinal ligaments of the spine.

OBJECTIVE There have been no reports on the long-term radiographic outcomes of posterior vertebral column resection (PVCR) in patients with congenital scoliosis. The purpose of this study was to evaluate the surgical outcomes and complications after PVCR and its long-term effects on correcting this deformity in children with congenital scoliosis. METHODS The authors retrospectively analyzed the medical records of 45 patients with congenital scoliosis who were younger than 18 years at the time of surgery and who underwent PVCR and fusion with pedicle screw fixation (PSF). The mean age of the patients at the time of surgery was 11.3 years (range 2.4–18.0 years), and the mean length of follow-up was 12.8 years (range 10.1–18.2 years). RESULTS The mean Cobb angle of the main curve was 46.5° before PVCR, 13.7° immediately after PVCR, and 17.6° at the last follow-up. For the compensatory cranial curve, PVCR corrected the preoperative Cobb angle of 21.2° to 9.1° postoperatively and maintained it at 10.9° at the last follow-up. For the compensatory caudal curve, the preoperative Cobb angle of 23.8° improved to 7.7° postoperatively and was 9.8° at the last follow-up. The authors noted 22 complications, and the overall incidence of complications was 48.9%. CONCLUSIONS Posterior vertebral column resection is an effective procedure for managing congenital scoliosis in patients younger than 18 years. Use of PVCR and fusion with PSF for congenital scoliosis achieved rigid fixation and satisfactory deformity correction that was maintained over the long term. However, the authors note that PVCR is a technically demanding procedure and entails risks for major complications and excessive blood loss.

OBJECT This retrospective study was designed to evaluate the clinical outcomes and radiological findings after open lumbar discectomy (OLD) in patients who were followed up for 10 years or longer. METHODS The authors classified 79 patients who had a mean age (± SD) of 53.6 ± 13.6 years (range 30–78 years) into 4 groups according to the length of their follow-up. Patients in Group 1 were followed up for 10–14 years, in Group 2 for 15–19 years, in Group 3 for 20–24 years, and in Group 4 for more than 25 years. In all of these patients, the clinical outcomes were assessed by using patients' self-reported scores on visual analog scales (VASs) measuring back and leg pain and by using scores from the Oswestry Disability Index (ODI). In addition, 10 radiological parameters suggesting degenerative changes or instability at the operated segment were recorded at various time points and used to calculate a numeric radiological finding (NRF) score by rating a presence for each finding of spinal degeneration or instability as 1. RESULTS The authors observed that OLD decreased pain and disability scores in all groups. Numeric radiological findings were highest in Group 4, and a significant correlation was detected between NRFs and VAS scores of back pain (p = 0.039). In this cohort, the reoperation rate was 13.9% during a mean follow-up period of 15.3 years. Clinical outcomes tended to be most favorable in Group 1, representing patients who had OLD most recently, and they tended to deteriorate in the other 3 groups, indicating some worsening of outcomes over time. Degeneration of the spine at the operated level measured with radiographic methods tended to increase over time, but some stabilization was observed. Although spinal degeneration was stable, clinical outcomes deteriorated over time. CONCLUSIONS This cross-sectional assessment of a retrospective cohort indicates that outcomes after OLD deteriorate over time. Increased back pain indicated a worsening of clinical outcomes, and this worsening was correlated with radiological findings of degeneration at the operated segment.

Object The authors undertook this study to investigate the validity of the rationale for posterior dynamic stabilization using the Device for Intervertebral Assisted Motion (DIAM) in the treatment of degenerative lumbar stenosis. Methods A cohort of 31 patients who underwent single-level decompression and DIAM placement for degenerative lumbar stenosis were followed up for at least 2 years and data pertaining to their cases were analyzed prospectively. Of these patients, 7 had retrolisthesis. Preoperative and postoperative plain lumbar radiographs obtained in all patients and CT images obtained in 14 patients were analyzed. Posterior disc heights; range of motion (ROM) of proximal, distal, and implant segments; lordotic angles of implant segments; percentage of retrolisthesis; and cross-sectional area and heights of intervertebral foramina on CT sagittal images were analyzed. Clinical outcomes were evaluated using visual analog scale scores and Oswestry Disability Index scores. Results The mean values for posterior disc height before surgery, at 1 week after surgery, and at the final follow-up visits were 6.4 ± 2.0 mm, 9.7 ± 2.8 mm, and 6.8 ± 2.5 mm, respectively. The mean lordotic angles at the implant levels before surgery, at 1 week after surgery, and at the final follow-up visits were 7.1° ± 3.3°, 4.1° ± 2.7°, and 7.0° ± 3.7°, respectively. No statistically significant difference was found between the preoperative values and values from final follow-up visits for posterior disc height and lordotic angles at implant levels (p = 0.17 and p = 0.10, respectively). There was no statistically significant difference between the preoperative and final follow-up visit values for intervertebral foramen cross-sectional area and heights on CT images. The ROMs of proximal and distal segments also showed no significant decrease (p = 0.98 and p = 0.92, respectively). However, the ROMs of implant segments decreased significantly (p = 0.02). The average 31.4-month improvement for all clinical outcome measures was significant (p < 0.001). Conclusions Based on radiological findings, the DIAM failed to show validity in terms of the rationale of indirect decompression, but it did restrict motion at the instrumented level without significant change in adjacent-segment ROM. The clinical condition of the patients, however, was improved, and improvement was maintained despite progressive loss of posterior disc height after surgery.

ObjectIn this paper the authors' goal was to determine the factors associated with the progression of degenerative lumbar scoliosis (DLS).MethodsTwenty-seven patients (3 men and 24 women; mean age 64.9 years) with more than 10° of lumbar scoliosis at baseline were monitored for a mean period of 10 years. The radiological evaluation included measurement of the scoliosis angle using the Cobb method, the direction of the scoliosis, the relationship between the intercrest line and the L-5 vertebra, lateral listhesis, segmental angle, distance from the center of the sacral line to the apical vertebra, degenerative listhesis anteriorly or posteriorly or both, and lordosis angle. In addition, the lateral osteophyte difference, disc index, and severity of osteoporosis were measured. The pain and disability outcomes were assessed using the visual analog scale and the Oswestry Disability Index (ODI) relative to severity of the angle of scoliosis.ResultsThe mean initial and final scoliosis angles were 14° ± 5.4° and 25° ± 8.5°, respectively. The initial disc index at the L-3 vertebra (Spearman ρ = 0.7, p < 0.001), the sum of the segmental wedging angles above and below the L-3 vertebra (ρ = 0.6, p < 0.001), and the initial disc index at the apical vertebra (ρ = 0.6, p < 0.001) were correlated with the last follow-up angle of the scoliosis. By contrast, there was no statistically significant correlation between the initial segmental angles at L2–3 and L3–4 and the final follow-up scoliosis angle (ρ = 0.2, p = 0.67; and ρ = 0.1, p = 0.22; respectively). When the authors separated the patients into 3 groups according to the sum of the segmental angles above and below L-3 (< 5°, 5° to 10°, and > 10°), they found that 3 (42.9%) of 7, 8 (66.7%) of 12, and 6 (75.0%) of 8 patients in the 3 groups showed increases of greater than 10° in scoliosis angle. The mean distance from the center of the sacral line to the apical vertebra was 36.0 ± 9.7 mm, and the distance correlated with the measurement of the last follow-up angle of the scoliosis (ρ = 0.6, p < 0.001). The mean angle of the scoliosis was significantly greater when the intercrest line passed through the L-5 or L4–5 disc space than when the line passed through the L-4 vertebral body (31.4° ± 7.9° vs 21.8° ± 6.7°, p = 0.01). The ODI correlated with the measurement of the angle of the scoliosis (ρ = 0.6, p < 0.001). Age, sex, osteoporosis, the direction of the scoliosis, listhesis of coronal and sagittal planes, the lateral osteophyte difference, and the vertebral body index did not correlate with curve progression.ConclusionsThe findings of this study demonstrated that the progression of DLS was affected by the relationship between the intercrest line and the L-5 vertebra. When L-5 was deep seated, progression of DLS was found. Asymmetrical change in the disc space above and below the L-3 or apical vertebra may also be an important predictor of curve progression.