Why does tension band wiring fail in transverse patellar fractures? Radiographic insights from a 10-years retrospective cohort

Abstract

Background: The aim of this study was to identify the radiographic parameters associated with failure of tension band wiring (TBW) in the treatment of transverse patellar fractures, with the goal of guiding surgical decision-making.

Materials and methods: A total of 76 patients underwent surgical treatment for patellar fractures at Trakya University between January 2013 and December 2022. We retrospectively analyzed 32 patients who met the study's inclusion criteria for transverse fractures (AO Type 34- C1) treated with TBW. Radiographic parameters assessed included patellar width, inter-K-wire distance, K-wire-to-patella ratios, knot configuration, and K-wire length, all evaluated for their potential association with fixation failure. Failure was defined as cerclage wire slippage or breakage. Statistical analyses were conducted using SPSS and Jamovi software. Descriptive statistics, t-tests, chi-square or Fisher's exact tests, logistic regression, and ROC analysis were performed. A p-value < 0.05 was considered significant.

Results: The mean age was 50 years ± 15.8 (range 26-80), with 8 women (25%) and 24 men (75%). Nine patients (28.1%) experienced TBW failure. Notably, single-knot constructs had significantly higher failure rates (66.7% vs. 19.2%; OR = 0.119, 95% CI [0.017-0.843], p = 0.038). Increased K-wire length was associated with failure (p = 0.008; cutoff 69.1 mm, AUC = 0.785). Patella-K-wire length ratio was higher in failures (p = 0.035). Lateral K-wire to articular distance and lateral K-wire to articular distance surface to patella thickness ratio were also significant predictors in slippage group (p = 0.046 and p = 0.031).

Conclusion: The number of knots, K-wire length, and specific radiographic parameters are important predictors of TBW failure. Attention to construct configuration and K-wire placement is crucial to minimize failure risk.

Keywords: Failure; K-wire; Patellar fracture; Radiographic analysis; Risk factors; Tension band wiring.

Fig. 1

Knee AP and lateral X-ray, a) patellar width, b) inter-K-wire distance, c) distance the proximal end of proximal K-wire to tension band wire, d) distance the distal end of proximal K-wire to tension band wire, e) distance of the knot from the corner, f) K-wire length, g) patellar length, x) patellar thickness, y) distance between the K-wire and the articular surface

Fig. 2

Receiver operating characteristic (ROC) curves for predictors of K wire-cerclage wire slippage