Preoperative Hypokyphosis as a Compensatory Mechanism for Positive Sagittal Balance and Risk Factor for Proximal Junctional Kyphosis. (16th November 2020)

• Record Type: Journal Article
• Authors: Body, Alaina; Krueger, Bryan M; Plummer, Zachary J; Nasser, Rani; Cheng, Joseph S
• Is Part Of: Neurosurgery. Volume 67(2010)Supplement 1
• Publication Date: 2020-11-16
• Subjects: Nervous system -- Surgery -- Periodicals; 617.48005
• DOI: 10.1093/neuros/nyaa447_746
• Languages: English
• ISSNs: 0148-396X

Abstract

Abstract: INTRODUCTION: The utilization of lateral scoliosis films in surgical planning for deformity correction allows surgeons to assess the degree of correction needed in the sagittal plane while accounting for pelvic retroversion, a recognized compensatory mechanism for restoration of sagittal balance. However, proximal junctional kyphosis (PJK) persists as a common complication of thoracolumbar fusion. METHODS: A retrospective review was performed of all thoracolumbar deformity correction cases at a single institution between 2017 and 2019. Twenty-nine patients had satisfactory preoperative and follow-up scoliosis films for measurement of T5/T12 thoracic kyphosis (TK), mobile segment kyphosis, and proximal junctional angle (PJA). Twenty-one of these patients also had adequate scoliosis films in the immediate postoperative period for measurement of these parameters, allowing for analysis of instantaneous preoperative to postoperative changes. RESULTS: Analysis included 29 patients, 14 of whom met radiographic criteria for PJK. We found a statistically significant increase in PJK in patients with less preoperative mobile segment kyphosis (10.5±6.9° vs. 25.5±7.8° in the non-PJK group, P < .001) and a nearly-significant increase in patients with less preoperative T5/12 TK (28.3±13.0° vs. 36.7±14.2°, p = 0.107). Of these 29 patients, 21 were included in analysis of preoperative to postoperative radiographic changes. We found patients who developed PJK had greater changes in mobile segment kyphosis (13.5±5.7° vs. 0.4±3.6°, P < .001) and greater changes in T5/12 TK (10.3±9.9 vs. 1.4±6.1°, P = .035). We found no relationship between PJK and postoperative TK, postoperative mobile segment kyphosis, or UIV. CONCLUSION: These results suggest that patients who develop PJK may be utilizing hypokyphosis as a compensatory mechanism preoperatively to restore sagittal balance. We propose that the addition of flexion-extension thoracic radiographs to surgical planning may allow surgeons to assess thoracic mobility and prevent overcorrection by identifying patients who may be utilizing hypokyphosis as a compensatory mechanism. Furthermore, postoperative analysis of change in mobile segment kyphosis may offer a strong predictor of patients at risk of PJK.