Impact of Adjacent Muscular Anatomical Preservation on Proximal Junctional Kyphosis and Failure

Surgical intervention is a cornerstone of adult spinal deformity (ASD) management. However, there remain burdens from complications including proximal junctional kyphosis (PJK) and failure (PJF). Posterior anatomical preservation at the uppermost instrumented vertebra (UIV) has emerged as an accessible approach to potentially reduce PJK/PJF risk. We assembled an institutional cohort of ASD patients evaluated between 2017-2022 who had spinal fusion performed with a modified subperiosteal dissection at and immediately below the UIV. Through a meta-analysis with a random-effects model, we compared our incidence of PJK/PJF against other prophylactic interventions. Ninety patients were identified, (median age: 64 years, average follow-up: 19 months). A majority had scoliosis and/or spinal stenosis with a median of 8 levels fused (40% revision cases). 6.7% and 3.3% of patients developed PJK and PJF respectively, with the most common clinical correlate being a minor neurologic deficit such as numbness (37.8%). PJK/PJF and non-PJK/PJF patients had similar post-operative complication profiles. Radiographic parameters varied: the PJK/PJF cohort had greater pre-operative pelvic incidence/pelvic tilt and post-operative pelvic incidence-lumbar lordosis mismatch as well as smaller operative correction of the thoracolumbar Cobb angle. In the literature, prophylactic interventions broadly reduced the incidence of PJK/PJF, with a pooled estimate of 19% compared to 36% in patients who did not receive any additional intervention. Preservation of posterior anatomical structures likely has a role in reducing the rate of PJK/PJF. Linking radiographic parameters to PJK/PJF while studying techniques that keep posterior structures intact may be steps toward improving ASD correction outcomes.