Value of Tip-Apex Distance (TAD) in the Fixation of Intertrochanteric Fractures by Dynamic Hip Screw (DHS)

Background: The fixation of ITF by DHS allows the compression of the fracture when the patients bear weight. Placement of lag screw should be central in the head and neck of the femur. This study aimed to emphasize the clinical value of the tip apex distance as a reliable predictor of the cut-out of the lag screw in the fixation of stable ITF. Patients & Methods: This was a retrospective cohort study that included 18 cases, skeletally mature patients with post-traumatic intertrochanteric fractures treated with DHS in the period from January 2016 to December 2016 with follow up of at least six months at Zagazig University Hospital. ITFs were internally fixated with DHS, and by postoperative follow-up, we measured the TAD post-operatively and after 6 months to detect the importance of TAD on the stability of lag screw in the head and neck of the femur and reported cases that developed cut-through of the lag screw. Results: TAD was the main measurement in the study. The rate of implant failure and cut-through was 27.8%. The median of TAD postoperative was 2.05. The median of TAD after 6 months was 2.23. There was a highly significant difference between the median of TAD after 6 months that developed cut-through and median of TAD after 6 months that did not develop cut-through (p-value <0.001). Conclusions: TAD of less than 25mm is safe and more than 25mm may result in the penetration of implant, non-union, cut-through, and other complications. Therefore, TAD is a reliable factor and has great value in DHS operations.