Tip to apex distance in femoral intertrochanteric fractures: a systematic review

Hip fractures are associated with high morbidity, mortality, and cost. Implants used for hip fracture fixation can fail for many reasons including lag screw cut-out. Tip–apex distance (TAD) is indicative of the position and depth of a screw in the femoral head and has been shown to be associated with cut-out failure. We conducted a systematic review of the published literature to quantify the association between TAD and cut-out failure for patients undergoing hip fracture fixation surgery. We performed a search of the Medline, Embase, and Cochrane databases. We performed abstract and full text reviews independently and in duplicate. We used a random effects model to combine, in duplicate, the incidence of cut-out for patients who had TAD <25 mm and TAD >25 mm. We also combined mean TAD values for patients who had cut-out failure and those who did not. Seventeen studies were eligible for this review, four of which were included in combined analysis of dichotomous outcomes and seven in combined analysis of continuous outcomes. Patients with TAD >25 mm had a significantly greater risk of cut-out than patients with TAD <25 mm (RR = 12.71). Patients who experienced implant cut-out had significantly higher TAD scores than those who did not (mean difference = 6.54 mm). Tip–apex distance is an important concept in relation to cut-out failure of hip fracture fixation surgery. Surgeons should understand and apply the concept of TAD to improve outcomes for their patients.