Comparing Fixation Stability of Rotationally Unstable Proximal Phalanx Fractures: A Biomechanical Study

Background: Proximal phalanx fractures are common upper extremity injuries; surgical fixation is often recommended for unstable patterns. Intramedullary screw (IMS) fixation has emerged as a minimally invasive technique with potential benefits of earlier motion and reduction of soft tissue disruption compared with traditional methods. However, its resistance to fracture displacement in rotationally unstable fracture patterns requires further investigation. This study compares the biomechanical stability of single IMS, dual crossing IMS, and 2 interfragmentary cortical screw constructs in short oblique proximal phalanx fractures. Methods: Eleven cadaveric hands were used in the study. Sixty-degree oblique extra-articular proximal phalanx fractures were created in middle, index, and ring fingers and then randomly assigned to 1 of 3 constructs: single 3.5-mm IMS, dual crossing 2.5-mm IMS, or two 1.5-mm cortical screws perpendicular to the fracture. The hands underwent a flexion-extension protocol of 2000 cycles at 0.25 Hz, simulating postoperative motion. The fractures’ angular rotation (degrees) and displacement in coronal and sagittal planes (millimeters) were subsequently measured. Statistical analysis was conducted using analysis of variance with P value <.05 defined as statistically significant. Results: There was no significant difference in average angular rotation, or sagittal and coronal displacement across the 3 constructs after simulated early postoperative range of motion. None of the specimen reached clinically significant displacement more than 2 mm. Conclusion: The biomechanical stability of single IMS, dual IMS, and interfragmentary screws does not differ when considering angular rotation or displacement during simulated early postoperative range of motion in short oblique proximal phalanx fractures.