Intertrochanteric femoral fracture with lateral wall fracture at the lag screw insertion site may cause postoperative anterior wall fracture and lead to deterioration in activities of daily living.

Background: Incomplete reduction and fixation of intertrochanteric femoral fractures significantly affect patients' daily activities. The lateral wall's integrity is pivotal in such fractures. This study examines instability, particularly lateral wall fractures at the lag screw insertion site and postoperative anterior wall fractures.

Methods: Overall, 161 patients with femoral intertrochanteric fractures were included. Three-dimensional computed tomography was conducted preoperatively and 3 weeks postoperatively to determine the postoperative anterior wall fractures incidence. Patient background, operative time, intraoperative blood loss, postoperative telescoping, and daily living activities were compared.

Results: The study recorded 51 cases of lateral wall fractures at the lag screw insertion site and 17 of postoperative fractures of the anterior wall. Postoperative fractures of the anterior wall were found in 3 of 110 and 14 of 51 patients in the group without and with the lag screw insertion site, respectively. The group of postoperative fractures of the anterior wall had significantly lower bone mineral density, longer operative time, and increased intraoperative blood loss. At 4 weeks postoperatively, the group of postoperative fractures of the anterior wall showed increased telescoping and decreased motor component of the functional independence measure (with postoperative fractures of the anterior wall: 28, without postoperative fractures of the anterior wall: 30), and significant reductions were observed in the transfer and locomotion items, indicating lower limb function (with postoperative fractures of the anterior wall group: 11, without postoperative fractures of the anterior wall group: 12).

Conclusions: Postoperative anterior wall fractures occurred in 27.5% cases with lateral wall fractures at the lag screw insertion site. Three-dimensional computed tomography is useful for preoperative evaluation of lateral wall fractures at the lag screw insertion site to assess instability. Postoperative fractures of the anterior wall related reduction in daily living activities needs attention.