JOT - 2026-06-01 - Journal Article; Multicenter Study
Initial Patella Vertical Fracture Displacement Is a Predictor of Nonunion and Hardware Failure.
Lashgari AM, Goldstein AR, Monroe GW, Ganta A, Konda S, Egol KA
Topics
Key Takeaway
Initial vertical patellar fracture displacement >26.6 mm predicts nonunion (AUROC 0.818) and >21.7 mm predicts hardware failure (AUROC 0.838), with each millimeter increase raising risk of either complication by ~15%.
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Summary
This multicenter retrospective study evaluated whether initial vertical displacement on preoperative radiographs predicts postoperative complications in 229 patients undergoing ORIF for patellar fractures (AO/OTA 34A-C). Mean displacement was significantly greater in patients who developed nonunion (29.8 vs. 15.1 mm, P<0.001) and hardware failure (30.8 vs. 15.4 mm, P<0.001). Suture-only and screw-with-suture constructs had independently higher nonunion rates (P=0.004 and P=0.005) compared to tension band wiring and plate fixation.
Key Limitation
Median follow-up of 12 months is insufficient to capture the full incidence of nonunion, which by FDA definition requires assessment at 9 months with serial radiographs, meaning complication rates are likely underreported.
Original Abstract
OBJECTIVES
To determine if initial vertical fracture displacement affects postoperative outcomes after operative treatment of patella fractures.
DESIGN
Prognostic retrospective study.
SETTING
Single multisite urban academic institution.
PATIENT SELECTION CRITERIA
Included were patients aged ≥18 years who underwent open reduction internal fixation of a patella fracture (AO/OTA 34A-C) with minimum 6-month follow-up and complete trauma knee x-ray series. Vertical fractures and those without significant vertical displacement (<2 mm) were excluded.
OUTCOME MEASURES AND COMPARISONS
Initial vertical fracture displacement was recorded. Follow-up data included knee range-of-motion and postoperative complications: nonunion, fracture-related infection, hardware failure, suspected fracture-related infection, knee contracture, inferior sleeve displacement, and venous thromboembolism events. Comparisons were made between the initial amount of displacement and postoperative complications.
RESULTS
Two hundred twenty-nine patients with a median follow-up duration of 12 months (Interquartile range: 6-14) were included. The mean age was 61.2 ± 15.1 years, body mass index was 25.4 ± 4.7 kg/m 2 , and 69.0% (n = 158) were female. Orthopaedic Trauma Association fracture classification was 35.4% C1, 32.3% C3, 17.9% C2, and 14.4% A1. Fixation methods included 63.8% tension band wiring, 17.9% suture repair, 13.5% plate and screws, and 4.8% screws with suture. Thirty-three (14.4%) patients sustained complications. The mean displacement was significantly higher in patients who developed complications (21.6 mm ± 15.0 mm vs. 14.8 mm ± 10.1 mm, P = 0.018), particularly for nonunion (29.8 mm ± 13.5 mm vs. 15.1 mm ± 10.6 mm, P < 0.001) and hardware failure (30.8 mm ± 12.0 mm vs. 15.4 mm ± 10.9 mm, P < 0.001). Suture-only and screw-with-suture fixation had higher nonunion rates ( P = 0.004, P = 0.005) than other fixation methods independent of displacement. Initial displacement predicted nonunion and hardware failure (AUROCs = 0.818 and 0.838). Youden Index thresholds of >26.6 mm and >21.7 mm identified patients at increased risk for nonunion and hardware failure. Each millimeter increase in displacement raised nonunion and hardware failure risk by 14.9% (OR = 1.1, P = 0.003) and 14.6% (OR = 1.1, P = 0.003).
CONCLUSIONS
This study supports the future use of initial vertical fracture displacement as a prognostic tool for nonunion and hardware failure after patella open reduction internal fixation. Displacement >2 cm placed patients at high risk for these complications. Nonunion rates were higher in both suture-only and screw-with-suture fixation when compared with other fixation constructs.
LEVEL OF EVIDENCE
Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.