Osteoarthritis and spontaneous fusion of facet joints after percutaneous instrumentation in thoracolumbar fractures.

PURPOSE: This retrospective study determined the rate of osteoarthritis and spontaneous facet joint fusion and analyzed risk factors related to patient characteristics, fracture type or surgical technique on pre- and postoperative CT after percutaneous instrumentation in thoracolumbar fractures.

METHODS: 1050 facet joints adjacent to screws in 148 patients (15-85 years) with thoracolumbar fractures were analyzed with an average time between CTs of 12.3 months. Screw diameters, lengths and cement augmentation were recorded. Facet joint violation by screw trajectory and by insertion depth was classified in three grades. Pre- and postoperative osteoarthritis was graded as absent, minor or severe and postoperative facet joint fusion as absent, partial or complete.

RESULTS: The facet violation rate was moderate in 15.4% and severe in 0.6% according to screw trajectory, and 11.0 and 0.6%, respectively, according to insertion depth. Osteoarthritis was preoperatively rated moderate in 9.6% and severe in 1.2%. A progression was evidenced in 79 facet joints (7.5%). Screw cement augmentation was the main predictive factor (p < 0.0001). Partial fusion was evidenced in 2.6% and complete fusion in 1% of facet joints. Risk factors were: BMI (p = 0.0002), age (p = 0.0013), preoperative osteoarthritis (p = 0.0005), time between 2 CTs (p = 0.0001), B-type fractures (p = 0.0005), concomitant anterior fusion (p = 0.0034).

CONCLUSIONS: Occurrence or worsening of osteoarthritis was mainly observed in elderly patients with cement-augmented screws and spontaneous facet fusion in elderly patients with high BMI and preoperative osteoarthritis, or in anteriorly fused B-type injuries. Thus, percutaneous instrumentation can safely be removed after fracture consolidation in younger patients while preserving facet joints.