Effects of Knee Osteoarthritis on Compensatory Mechanisms Post-Spinal Deformity Correction

We investigated the relationship among regional alignments, the chronological sequence of compensatory mechanism changes, restoration of sagittal malalignment, and the effect of knee osteoarthritis on resolution of compensatory mechanisms and clinical outcomes in deformity correction surgery.

We reviewed medical records and images of 75 patients with adult spinal deformity (ASD) undergoing thoracolumbar fusion, with a minimum of 2 years of postoperative follow-up. Data collection focused on changes in various spinal and lower extremity alignments, including global angle, pelvic shift, knee angles (KA), and ankle angles (AA). We conducted propensity-matched comparisons to elucidate the impact of (OA) on resolution of compensatory mechanisms between the knee osteoarthritis (KOA) group and the non-knee osteoarthritis (NKOA) group based on the Kellgren-Lawrence Grading (KLG). Additionally, the study assessed patient-reported outcome measures.

A significant linear correlation was observed between the change in T1 pelvic angle (Δ TPA) and the changes in various spinal and lower extremity parameters during follow-ups. Statistically significant correlation coefficients for thoracic kyphosis, sacro-femoral angle (SFA), and AA, initially not observed, were observed during the final follow-up. The KOA group exhibited limited restorative changes in compensatory spinal and lower extremities (KA: 1.1 ± 5.5 vs 7.1 ± 9.3, p=0.015). Clinical outcomes showed improvement in both groups, with the NKOA group demonstrating more significant progress in SF-36 (p<0.05).

Restoring sagittal alignment leads to the disappearance of compensatory mechanisms in a temporal pattern, with lower extremity improvements continuing for years. Severe knee OA over KLG 3 impedes this restoration and results in poorer clinical outcomes.