Incidence and Radiological Risk Factors of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Following Pedicle Screw Instrumentation with Rod Derotation and Direct Vertebral Rotation: A Minimum 5-Year Follow-Up Study

Several studies have reported incidence and risk factors for the development of proximal junctional kyphosis (PJK) in patients with adolescent idiopathic scoliosis (AIS). However, there is little information regarding long-term follow-up after pedicle screw instrumentation (PSI) with rod derotation (RD) and direct vertebral rotation (DVR). Sixty-nine AIS patients who underwent deformity correction using PSI with RD and DVR were retrospectively analyzed in two groups according to the occurrence of PJK, with a minimum five-year follow-up, including a non-PJK group (n = 62) and PJK group (n = 7). Radiological parameters were evaluated at preoperative, postoperative, and last follow-up. Incidence for PJK was 10.1% (7/69 patients), with a mean 9.4-year follow-up period. The thoracolumbar/lumbar curve (TL/L curve) was proportionally higher in the PJK group. The proximal compensatory curve was significantly lower in the PJK group than in the non-PJK group preoperatively (p = 0.027), postoperatively (p = 0.001), and at last follow-up (p = 0.041). The development of PJK was associated with the TL/L curve pattern, lower preoperative proximal compensatory curve, and over-correction of the proximal curve for PSI with RD and DVR. Therefore, careful evaluation of compensatory curves as well as of the main curve is important to prevent the development of PJK in the treatment of AIS.

Can Proximal Junctional Kyphosis After Surgery for Adult Spinal Deformity Be Predicted by Preoperative Dynamic Sagittal Alignment Change With 3D Gait Analysis? A Case–control Study

PurposeTo investigate whether preoperative dynamic spinal alignment that worsened during gait as detected by three-dimensional (3D) gait analysis can be a predictive factor for proximal junctional kyphosis (PJK) after corrective surgery for adult spinal deformity (ASD) with a minimum 1-year follow-up.MethodWe included 27 patients with ASD who underwent 3D gait analysis before corrective surgery and had >1-year follow-up. Dynamic spinal alignment parameters were obtained using a Nexus motion capture system (Vicon, Oxford, UK) with reflective markers. Spinal alignment was assessed in each region and pelvic alignment was assessed with surface markers. Patients were asked to walk for as long as possible around an oval walkway. We obtained the averaged dynamic parameters in the final lap and compared them between patients with PJK(+) and those with PJK(–).ResultsPJK occurred in 7 patients (26%). Preoperative angle between the thoracic spine and the pelvis was larger in patients with PJK(+) than in those with PJK(–) (32.3 ± 8.1 vs 18.7 ± 13.5, P = 0.020) with sufficient sample size. Multiple logistic regression analysis identified the angle between the thoracic spine and pelvis as an independent risk for PJK.ConclusionPreoperative thoracic kyphosis exacerbated by gait as determined in 3D gait analysis is a preoperative independent risk factor of PJK in patients undergoing ASD corrective surgery.

Health insurance policy on surgical treatment of adult spinal deformity

Background: Recent burgeoning research on adult spinal deformity (ASD) has unveiled the benefits of surgical treatment and how to gain the benefits although these have only been around for 10 years.Current Concepts: During the last decade, the significance of pelvic incidence in the global spinal sagittal alignment and introductions of the Scoliosis Research Society-Schwab classification for ASD have been the guidelines of surgical treatment for ASD and the milestones for promising surgical results. However, one of the unsolved problems for the surgical treatment of ASD is the proximal junctional kyphosis, for which multifactorial causative factors have been suggested. Recent studies have focused on dynamic natures in patients with ASD during daily activities, which might be a clue for both prevention of proximal junctional kyphosis and a better level of surgical results. Even though a recent remarkable advancement for surgical treatment for ASD is present, the national guideline for reimbursement is still following the surgical indication for lumbar degenerative kyphosis published in 1988.Discussion and Conclusion: A significant gap exists between the national reimbursement guideline and generally held surgical indication for ASD surgery. Consequently, this huge gap raises trouble in both patients and surgeons. The patients with ASD cannot take an appropriate surgery for ASD, while the spine surgeons experience unreasonable adjustment of the cost by the Health Insurance Review and Assessment Service.

The standing T1–L1 pelvic angle: a useful radiographic predictor of proximal junctional kyphosis in adult spinal deformity

OBJECTIVE Proximal junctional kyphosis (PJK), which can worsen a patient’s quality of life, is a common complication following the surgical treatment of adult spinal deformity (ASD). Although various radiographic parameters have been proposed to predict the occurrence of PJK, the optimal method has not been established. The present study aimed to investigate the usefulness of the T1–L1 pelvic angle in the standing position (standing TLPA) for predicting the occurrence of PJK. METHODS The authors retrospectively extracted data for patients with ASD who underwent minimum 5-level fusion to the pelvis with upper instrumented vertebra between T8 and L1. In the present study, PJK was defined as ≥ 10° progression of the proximal junctional angle or reoperation due to progressive kyphosis during 1 year of follow-up. The following parameters were analyzed on whole-spine standing radiographs: the T1–pelvic angle, conventional thoracic kyphosis (TK; T4–12), whole-thoracic TK (T1–12), and the standing TLPA (defined as the angle formed by lines extending from the center of T1 and L1 to the femoral head axis). A logistic regression analysis and a receiver operating characteristic curve analysis were performed. RESULTS A total of 50 patients with ASD were enrolled (84% female; mean age 74.4 years). PJK occurred in 19 (38%) patients. Preoperatively, the PJK group showed significantly greater T1–pelvic angle (49.2° vs 34.4°), conventional TK (26.6° vs 17.6°), and standing-TLPA (30.0° vs 14.9°) values in comparison to the non-PJK group. There was no significant difference in the whole-thoracic TK between the two groups. A multivariate analysis showed that the standing TLPA and whole-thoracic TK were independent predictors of PJK. The standing TLPA had better accuracy than whole-thoracic TK (AUC 0.86 vs 0.64, p = 0.03). The optimal cutoff value of the standing TLPA was 23.0° (sensitivity 0.79, specificity 0.74). Using this cutoff value, the standing TLPA was the best predictor of PJK (OR 8.4, 95% CI 1.8–39, p = 0.007). CONCLUSIONS The preoperative standing TLPA was more closely associated with the occurrence of PJK than other radiographic parameters. These results suggest that this easily measured parameter is useful for the prediction of PJK.