Stability of fixation of proximal phalanx unicondylar fractures of the hand: A biomechanical cadaver study

Purpose: To determine the relative stability of various fixation methods for proximal phalanx intra-articular unicondylar fractures during simulated early active motion. Methods: We created proximal phalangeal intra-articular unicondylar fractures in 13 fresh-frozen human cadaveric hands. Using a saw through a dorsal approach, we made an osteotomy beginning in the intercondylar notch and extending proximally at a 45° angle to the radial border of the proximal phalanx. We fixed each of the 4 fingers on each hand with a 1.5-mm headless compression screw, a 1.5-mm lag screw, two 1.1-mm smooth K-wires, or one 1.1-mm smooth K-wire. We rotated the order of constructs randomly for each hand. We simulated active range of motion on a custom-loading device at 0.25 Hz from full finger extension to full flexion for 2,000 cycles and measured displacement by a differential variable reluctance transducer. Results: We found no significant differences in displacement of the fracture site among the 4 methods of fixation. Movement in the control specimen with no osteotomy fixation was significantly higher than with each of the other fixation methods. Conclusions: Biomechanical stability did not differ among the fixation methods for proximal phalanx unicondylar fractures in a flexion-extension active range of motion model. Clinical relevance: Fixation of these fractures with any of the methods tested may provide sufficient stability to withstand postoperative therapy when there is no substantial resistance to active motion.