Comparative analysis of TAD and CalTAD in predicting lag screw cutout risk in trochanteric fractures treated with intramedullary devices: a retrospective study

Background: Cutout is one of the common cause of mechanical failure after internal fixation of trochanteric fractures using intramedullary devices. Tip apex distance (TAD) and Calcar referenced tip apex distance (CalTAD) are the radiographic parameters to predict the cutout risk. The aim of the study is to compare CalTAD with TAD in predicting the screw cutout risk and also to assesses other parameters responsible for it. Methods: A total of 100 patients were included in this retrospective study. For each patient the following data were recorded. Number of cutouts, AO/OTA classification, quality of the reduction, type of nail, center column diaphyseal angle, type of distal locking, post-operative weight-bearing, TAD, CalTAD values and the position of the screw in the femoral head according to the Cleveland system. Results: The incidence of cutout across the sample was 6%. The median TAD in cutout group was 32.2±6.5 (Mean±SD) while in no cutout group it was 20.7±5.1(p<0.001). Similarly, the median CalTAD in cutout group was 33±5.6 (Mean±SD) while in no cutout group it was 21.1±4.6 (p<0.001). The highest value of sensitivity and specificity showed that the best cut off values of TAD is 30.06 (95% CI: 0.823-1.000, P<0.001) and Cal TAD is 30.93 (95% CI: 0.835-1.000, p<0.001). Conclusions: In order to reduce the incidence of cutout it is advisable to achieve positive cortical reduction, placing the lag screw in centre-centre or centre-inferior in femoral head (Preferably in Cleveland Zone-5) and avoid TAD>30.06 and Cal TAD>30.93.