Association Between Lower Instrumented Vertebra Selection and Mechanical Complications After Surgical Correction for Kyphotic Deformity Following Osteoporotic Vertebral Fracture

TL;DR

This study finds that the choice of lower instrumented vertebra in surgery for kyphotic deformity after osteoporotic fractures affects the risk of mechanical complications.

Contribution

The study identifies specific patient factors associated with distal junctional failure in short-fixation surgeries for kyphotic deformity.

Findings

Short fixation reduced proximal junctional failure compared to long fixation.

Distal junctional failure occurred only in the short-fixation group and was linked to preoperative malalignment and muscle degeneration.

Short fixation preserved better postoperative lumbar function.

Abstract

Background: Kyphotic deformity following osteoporotic vertebral fracture (KDOVF) often requires corrective surgery to restore sagittal alignment; however, mechanical complications, such as proximal junctional failure (PJF) and distal junctional failure (DJF), remain major concerns. Selection of the lower instrumented vertebra (LIV) plays a critical role in balancing mechanical stability and functional preservation; however, the optimal criteria for LIV selection have not been fully established. Methods: This multicenter retrospective cohort study included 52 patients who underwent corrective surgery for KDOVF, with a minimum 1-year follow-up. The patients were classified into a long-fixation group with pelvic fixation (n = 27) and a short-fixation group with lumbar LIV fixation (n = 25). Mechanical complications, radiographic parameters, patient-reported outcomes, and paraspinal muscle fatty degeneration were compared between groups. Subgroup analysis was performed within the short-fixation group to identify the factors associated with DJF. Results: The incidence of PJF was significantly higher in the long-fixation group than in the short-fixation group (37% vs. 8%, p < 0.01), whereas DJF was observed only in the short-fixation group (24%). Within the short-fixation group, patients who developed DJF demonstrated significantly greater preoperative sagittal malalignment, a lower rate of cement-augmented pedicle screw, and more advanced fatty degeneration of the paraspinal muscles. The short-fixation group also showed better postoperative lumbar function. Conclusions: LIV selection in KDOVF surgery is associated with distinct patterns of junctional mechanical complications. Short fixation may be feasible in carefully selected patients who demonstrate preserved compensatory capacity.

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