Abstract
Introduction
Tip apex distance (TAD) is reported as a predictor for cut outs of lag screws in the treatment of intertrochanteric fractures, and surgeons are adviced to strive for TAD within 20 mm. However the definition of neck axis and the limb position of lateral radiograph are not clearly described in the original literature. We propose the refined TAD by defining these factors. The objective of this study was to analyze the interobserver agreement of this refined TAD.
Materials and Method
X rays of 130 cases of unstable trochanteric fractures were used for the analysis of the refined TAD. In the refined TAD, neck axis was defined as the line between the center of femoral head and midpoint of narrowest part of the femoral neck, and lateral radiograph was taken with hip flexion 90 degrees and abduction 45 degrees. The refined TAD was independently measured by 2 experienced (observer 1,2) and 2 inexperienced (observer 3,4) orthopaedic surgeons who were trained with the new method before the measurement. Intraclass correlation coefficient (ICC [2,4]) was calculated to assess the interobserver agreement.
Result
The mean refined TADs were 18.2:18.4:18.2:18.2 for observer 1:2:3:4. There was a strong correlation among all four observers (ICC 0.998, (95% CI: 0.998, 0.999).
Discussion
Regardless of the clinical experience of observers, the refined TAD is a reliable tool and can be used to develop new TAD recommendations for predicting failure of fixation.
