Accuracy and awareness of lag screw placement when using the dynamic hip screw for fracture fixation

Introduction: Correct lag screw placement in the femoral head is important to prevent screw cut-out following dynamic hip screw (DHS) fracture fixation. The aim of the study was to determine the accuracy and awareness of lag screw placement when using the DHS for fracture fixation. Patients and methods: A retrospective radiographic review of 238 DHS procedures (mean age 81.1 years; 76% female) performed at one centre was undertaken to determine the proportion of lag screws placed correctly (tip-apex distance (TAD) less than 25 mm and central femoral head lag screw position in both radiographic views). A questionnaire was also distributed to 102 orthopaedic surgeons to assess awareness of correct lag screw placement. Results: Mean TAD for 238 procedures was 17.2 mm with specialist registrars performing 74%. Lag screws were correctly placed in 80% (n = 190) with correct placement independent of surgeon grade (p = 0.418), AO fracture classification (p = 0.306) and contralateral femoral neck-shaft angle (p = 0.748). This remained unchanged when 17 lag screws meeting the recommendations, but with an inferior position on the anteroposterior radiograph, were included as correctly placed. Surgeons correctly defined TAD, stated the recommended TAD and measured TAD correctly in 81%, 81% and 57%, respectively. Correct responses were independent of surgeon grade and number of procedures performed. Conclusions: Although most lag screws were placed correctly, the questionnaire revealed that almost half of surgeons measured TAD incorrectly. Educating surgeons on the concepts related to correct lag screw placement and acquiring technical skills using surgical simulators may reduce the risk of screw cut-out in their practice.