Blocking screw (pin) technique to achieve an acceptable reduction in intramedullary of subtrochanteric femoral fractures: indications, techniques, and clinical outcomes

Introduction: Subtrochanteric femur fractures treated with intramedullary nails present biomechanical benefits, early weight-bearing, and reduced soft tissue damage, promoting bone union. However, improper reduction due to muscular forces and fragmented proximal bone increases nonunion risk. This study evaluates the efficacy of the blocking screw technique in preventing malalignment during intramedullary nailing. Material and methods: In cases of subtrochanteric femoral fractures where malalignment, such as varus and anterior angulation, was anticipated during intramedullary nailing, proper reduction was ensured using blocking screw technique on the proximal bone fragment from the coronal or sagittal plane. A retrospective analysis was conducted on 25 patients (14 males, 11 females; average age 55.12 years) who were followed up for more than 1 year. The postoperative neck-shaft angle, anterior angulation angle, and limb length discrepancy were compared radiologically with those on the healthy side, and the presence and duration of bone union were measured. The Harris hip score was used for functional evaluation, and complications, including infection, were analyzed. Results: At the final follow-up, primary bone union was achieved in 21/25 patients (84%), with an average bone union time of 21.81 weeks (range, 14–42 weeks). Of the four nonunions, bone union was achieved in three cases through bone grafting and supplemental plating and in the other case through intramedullary exchange, supplemental plating, and bone grafting. The femoral neck-shaft angle and anterior angulation showed no statistically significant differences compared with the healthy side, with averages of − 1.15° and − 1.4°, respectively. The limb length discrepancy was an average of − 2.4 mm. Regarding functional outcomes, the Harris hip score averaged 89.52 points (range 82–94 points). Conclusions: In subtrochanteric femoral fractures, the blocking screw technique effectively prevents malalignment during intramedullary nailing, ensuring not only appropriate reduction but also high bone union rates.