Exploring Appropriate Positioning of the Spiral Blade in Treatment of Subtrochanteric Fractures of the Femur Using Proximal Femoral Nail Antirotation.

Objectives: Subtrochanteric fractures have anatomic characteristics distinct from intertrochanteric fractures that may affect the positioning of the spiral blade during surgical treatment. Tip-apex distance (TAD) and calcar-referenced tip-apex distance (Cal-TAD) were measured to determine if these measures are reliable indicators to assist in the accurate placement of intramedullary nails and minimize postoperative complications.

Methods: For patients treated with proximal femoral nail antirotation (PFNA) internal fixation between 2016 and 2020, we analyzed the TAD, Cal-TAD, and postoperative complications. Fracture healing was assessed radiographically at 6-week intervals until union. The incidences of axial cut-off, cephalad cut-off, and non-union were also examined. Analysis of variance and Fisher's exact test were performed to evaluate differences in complications between the TAD and Cal-TAD groups.

Results: Data from 104 patients (58 males, 46 females) with a mean age of 56.9 years were analyzed. Fracture healing was observed in 90 (86.5%) patients at an average time of 14.92 ± 1.81 weeks. The healing rate was significantly higher when the TAD and Cal-TAD were controlled within the 20-25 mm range (p < 0.05). Postoperative complications occurred in 14 (13.5%) cases [cephalad cut-off, n = 5 (4.8%); axial cut-off, n = 4 (3.8%); non-union, n = 5 (4.8%)]. Five (4.8%) complications occurred without internal fixation failure. The fracture healing time and incidence of complications differed among groups defined by TAD and Cal-TAD measurements, and were shortest and lowest, respectively, in the 20 mm < TAD/Cal-TAD < 25 mm group.

Conclusions: In our cohort, use of PFNA internal fixation for treatment of unstable femoral subtrochanteric fractures and placement of the spiral blade in the middle or lower 1/3 of the femoral neck did not increase the incidence of complications. Therefore, we propose that the TAD rule of 20-30 mm should not apply to subtrochanteric fractures, and TAD and Cal-TAD should be controlled within the range of 20-25 mm to reduce the incidence of complications.