Tip apex distance - Is it enough to predict implant failure in trochanteric fractures

Introduction: The tip-apex distance (TAD) is the sum of the distances from the tip of lag screw to apex of the femoral head on both AP and lateral radiographs. A TAD of greater than 25 mm is considered to be an accurate predictor of lag screw cut-out when dynamic hip screws are used to treat intertrochanteric hip fractures. The purpose of this study was to determine the factors affecting the clinical outcomes of trochanteric fractures treated surgically. Materials and Methods: This retrospective study included 124 patients. The TAD values of this cohort were analysed from post-operative radiographs. The fractures were classified according to severity and the post-operative reduction and their affection to cut out rates was determined. These were correlated with functional status and inability to achieve fracture union at a mean follow-up of 12 months. Results: Good reduction was obtained in 28 cases of type 1 fractures while all the fractures which had poor reduction were type 2 fractures. All type 1 fractures united at a mean of 12 months. Overall 14 patients experienced lag screw cut-out, all of which were type 2 fractures. Discussion: The number of cut-outs had direct correlation to the severity of fractures and the TAD. While using dynamic hip screws, surgeons should try to achieve a TAD less than 25 mm to avoid lag screw cut-out. Though TAD plays a vital role in predicting implant failure in trochanteric fractures, quality of bone, fracture pattern, placement of screw etc also influence the outcome