Traditional distance "tip-apex" vs. new calcar referenced "tip-apex" - which one is the best peritrochanteric osteosynthesis failure predictor?

INTRODUCTION

In the treatment of trochanteric fractures, the distance between the tip of the screw and the apex of the femoral head or tip-to-apex distance (TAD) was popularized by Baumgaertner about 20 years ago as an important predictor of failure. Recently, a new reference point for determining the apex has been advocated. In this new calcar tip-to-apex (calTAD) the femoral head apex is referenced to the femoral calcar and not the center of the neck. The aim of this study is to evaluate which of these two indexes is better in predicting failure of pertrochanteric fracture fixation.

MATERIALS AND METHODS

We conducted a retrospective study focusing on pertrochanteric fractures operated in our institution between 2010-2013. Radiographic measurement of both indexes was performed. Demographic information, as well as several variables with recognized influence on the rate of failure, were collected. Finally, logistic regression analysis was used to identify variables independently associated with fixation failure.

RESULTS

A total of 463 pertrochanteric fractures were operated during this time period. One hundred and seventy cases were excluded because of early loss of follow-up (n = 143) or inadequate fluroscopic imaging (n = 27) control precluding accurate measurements. Two hundred and ninety-three fractures were included. Traditional TAD and calTAD were significantly different in the failure group: 24.9 vs. 18.0 mm (p < 0.001) and 29.2 vs. 22.6 mm (p < 0.001) respectively. No other registered variable was significantly different. Multivariate analysis confirms traditional TAD (p = 0.003; OR = 1.10) and calTAD (p = 0.002; OR = 1.12) as independent risk factors for failure.

DISCUSSION/CONCLUSION: Both the traditional TAD and the new calTAD have shown to be relevant indexes and independently predictive of the likelihood of failure of pertrochanteric fracture fixation. Interestingly, we found the optimal threshold for the traditional TAD to be lower (<20 mm) than the traditional cutoff (<25 mm). Our study did not confirm calTAD to be superior to the traditional TAD. From the surgical practice point of view, the authors argue that the ideal position of the screw is the central region of the femoral head (minimal traditional TAD). In case of deviation, it must be infero-central in order to maintain a low calTAD thus minimizing the risk of fixation failure.