Risk factors of adjacent-segment disease after short-segment fusion in patients with de novo degenerative lumbar scoliosis.

OBJECTIVE: Short-segment fusion (SSF) is an effective surgical option for appropriately selected patients with de novo degenerative lumbar scoliosis (DNDLS). Considering that DNDLS is frequently accompanied by multisegment degeneration and potential instability across the entire lumbar segments, it is inevitable that unhealthy segments remain after SSF, thereby increasing the potential risk of adjacent-segment disease (ASD) occurrence. Therefore, the authors aimed to identify the risk factors for ASD in patients with DNDLS who underwent SSF. METHODS: This retrospective study included 80 patients with DNDLS (Cobb angle > 10°) who underwent SSF (1 or 2 levels) between December 2010 and July 2018 with a minimum follow-up duration of 5 years. The participants were divided into two groups: ASD and non-ASD. ASD was defined as clinical ASD rather than radiographic ASD. Various patient and operative variables were compared between the groups. Global and regional radiographic parameters (preoperatively and postoperatively) were also compared between the two groups using plain radiography and MRI. Consequently, univariate and multivariate analyses were conducted to identify the risk factors for ASD occurrence. The receiver operating characteristic (ROC) curve was used to calculate the cutoff values. RESULTS: The mean ± SD age was 67.7 ± 7.2 years at the time of SSF, and there were 62 women (77.5%) enrolled in the study. Thirty patients (37.5%) were in the ASD group and 50 patients (62.5%) were in the non-ASD group. The mean time from the surgery to ASD diagnosis was 34.9 ± 28.2 months in ASD group. Thirteen patients required revision surgery at a mean time of 8.8 ± 7.0 months after ASD occurrence. Multivariate logistic regression analysis demonstrated that preoperative disc wedging angle (OR 1.806, 95% CI 1.255-2.598, p = 0.001), presence of facet tropism (defined as ≥ 10° difference between the facet joint angles of the right and left sides) (OR 5.534, 95% CI 1.528-20.040, p = 0.009), and foraminal stenosis ≥ grade 2 (OR 5.935, 95% CI 1.253-28.117, p = 0.025) were significant risk factors for ASD development. The cutoff value of the preoperative disc wedging angle was calculated to be 2.5° using the ROC curve. CONCLUSIONS: Preoperative disc wedging angle ≥ 2.5°, presence of facet tropism, and foraminal stenosis ≥ grade 2 were identified as significant risk factors for ASD development after SSF in patients with DNDLS.

Clinical Significance of Lordosis Orientation on Proximal Junctional Kyphosis Development in Long-Segment Fusion Surgery for Adult Spinal Deformity.

OBJECTIVE: We sought to evaluate the clinical impact of lordosis orientation (LO) on proximal junctional kyphosis (PJK) development in adult spinal deformity surgery. METHODS: This study included 152 patients who underwent low thoracic (T9-T12) to pelvis fusion and were followed up for ≥2 years. In the literature, 6 radiographic parameters representing LO were introduced, such as uppermost instrumented vertebra (UIV) slope, UIV inclination, UIV-femoral angle (UIVFA), thoracolumbar tilt, thoracolumbar slope, and lordosis tilt. Various clinical and radiographic factors including 6 LO parameters were investigated using logistic regression analysis to identify risk factors for PJK. RESULTS: The mean age was 69.4 years, and 136 patients were females (89.5%). PJK developed in 65 patients (42.8%). Multivariate logistic regression analysis revealed that only small postoperative pelvic incidence (PI)-lumbar lordosis (LL) (odds ratio [OR] = 0.962, 95% confidence interval: 0.929-0.996, P = 0.030) and large UIVFA (OR = 1.089, 95% confidence interval: 1.028-1.154, P = 0.004) were significant for PJK development. UIVFA showed significantly positive correlation with pelvic tilt (CC = 0.509), thoracic kyphosis (CC = 0.384), and lordosis distribution index (CC = 0.223). UIVFA was also negatively correlated with sagittal vertical axis (CC = -0.371). However, UIVFA did not correlate with LL, PI-LL, or T1 pelvic angle. CONCLUSIONS: LO significantly increases the risk of PJK development in ASD surgery. Multivariate analysis revealed that smaller postoperative PI-LL and greater UIVFA were significant risk factors for PJK. Surgeons should avoid undercorrection and overcorrection to prevent PJK development.

Sarcopenia and Back Muscle Degeneration as Risk Factors for Degenerative Adult Spinal Deformity with Sagittal Imbalance and Degenerative Spinal Disease: A Comparative Study.

BACKGROUND: Many factors affect spinal alignment in adult spinal deformity with sagittal imbalance. However, although the importance of the paravertebral muscle and ligamentum complex in proper spinal alignment is well recognized, little information is available regarding the role of the paravertebral muscles in maintaining sagittal spinal alignment. METHODS: A total of 108 patients who had visited our institution from January 2016 to June 2018 were included in the present study. The patients were categorized as follows: degenerative adult spinal deformity with sagittal imbalance group and degenerative spinal disease group. The appendicular skeletal muscle mass index and handgrip strength of each patient were measured to evaluate for sarcopenia. Computed tomography was used to measure the cross-sectional area (CSA) and fat infiltration rate to evaluate paravertebral muscle morphology. The paravertebral muscle function was assessed by measuring the lumbar flexor strength and lumbar extensor strength using a lumbar isokinetic dynamometer. RESULTS: The degenerative adult spinal deformity with sagittal imbalance group had a lower CSA index and lumbar extensor strength index and higher fat infiltration rate than the degenerative spinal disease group. No statistically significant differences in the appendicular skeletal muscle mass index and handgrip strength were found between the 2 groups. Only the CSA showed a correlation with the radiological parameters, such as pelvic tilt and lumbar lordosis. CONCLUSIONS: Degeneration of the paravertebral muscle is a risk factor for degenerative adult spinal deformity with sagittal imbalance but not for sarcopenia. Thus, spinal sagittal imbalance is affected by isolated paravertebral muscle degeneration rather than by systemic muscle degeneration.

Changes in Gait and Radiographic and Clinical Results of Calcaneal Lengthening Osteotomy in Children with Idiopathic Flexible Flatfoot.

BACKGROUD: In this study, we aimed to analyze kinematic and kinetic changes in gait and to assess radiographic and clinical improvement after calcaneal lengthening osteotomy (CLO) in children with idiopathic symptomatic flexible flatfoot deformities. METHODS: The study group consisted of 22 children (28 feet) with idiopathic symptomatic flexible flatfoot, which was treated by CLO as an index operation. We excluded patients with flatfoot that developed secondary to neuromuscular diseases. There were 18 boys (22 feet) and 4 girls (6 feet). The average age of the patients was 10.8 ± 1.51 years. Surgical results were assessed by radiologic imaging, clinical evaluation, and gait analysis, which were performed before surgery and 1 year after surgery. Medical records were reviewed to check postoperative complications. RESULTS: Talonavicular coverage was recovered to 16.7° from 32.7° (p < 0.01). Lateral talo-first metatarsal angle and calcaneal pitch angle increased by 20.1° and 9.9°, respectively (p < 0.01). Weight-bearing radiographs demonstrated a decrease in the anteroposterior angle and lateral talocalcaneal angle by 6.9° and 10°, respectively (p < 0.01). Hindfoot valgus was corrected to near neutral position after CLO. Kinematic results showed that the ankle valgus angle in the coronal plane was reduced from 35.48° preoperatively to 16.64° postoperatively during gait (p < 0.05). The preoperative out-toeing gait (preoperative foot progression angle, 20.31°) was also normalized to 14.21° postoperatively. The kinetics results showed that the push-off moment (maximum ankle plantar flexion) on the sagittal plane increased from 0.66 Nm/kg preoperatively to 0.83 Nm/kg postoperatively (p < 0.01). The mean Yoo score was 9.2 ± 1.05 postoperatively: satisfactory in 24 cases (86%) and unsatisfactory in 4 cases. Of the 4 unsatisfactory cases, 2 cases were overcorrection and 2 cases were undercorrection, and 3 of them were well managed by wedge foot insoles. CONCLUSIONS: The 3-dimensional deformities of the flexible flatfoot were effectively corrected by CLO, based on the morphological assessment using radiologic imaging. The correction was well maintained during gait at 1 year after the operation.

Sarcopenia and Back Muscle Degeneration as Risk Factors for Back Pain: A Comparative Study.

STUDY DESIGN: Case-control study. PURPOSE: To investigate the independent associations of back pain with sarcopenia and with back muscle degeneration, and to introduce a new risk index for back muscle degeneration. OVERVIEW OF LITERATURE: The Asian Working Group for Sarcopenia recommends diagnosis using handgrip strength, gait speed, and skeletal muscle mass. However, these criteria do not strongly reflect back muscle degeneration. METHODS: Patients who completed a questionnaire on back-pain between October 2016 and October 2017 were enrolled in this study. Appendicular skeletal muscle index (ASMI), cross-sectional area (CSA) index, fatty infiltration (FI) rate of the paraspinal muscles, and lumbar extensor strength index (LESI) were measured and compared between no back-pain and back-pain group. Correlations between LESI and ASMI, CSA index, and FI rate were analyzed. The back-pain group was further divided according to ASMI into sarcopenia and non-sarcopenia subgroups and by our newly developed back muscle degeneration risk index based on correlation coefficients between LESI and CSA index, FI rate. Differences in ASMI, CSA index, FI rate, LESI, and Visual Analog Scale (VAS) score between subgroups were analyzed. RESULTS: The ASMI, CSA index, FI rate, and LESI differed significantly between back-pain and pain-free groups. The LESI demonstrated the strongest correlation with FI rate. There were no significant differences in VAS score and back muscle degeneration index in the back-pain group when divided according to the presence of sarcopenia. However, there was a significant difference in VAS score between back-pain patients when classified according to high and low back muscle degeneration risk index. CONCLUSIONS: We suggest that the degree of back pain is more strongly associated with back muscle degeneration than with sarcopenia. This back muscle degeneration risk index, reflecting both back muscle morphology and function, could be a useful parameter for evaluation of back pain and muscle degeneration.