Rotational Stability of One Versus Two Intramedullary Screws for Proximal Phalanx Fractures: A Biomechanical Study

Area of Science:

• Orthopedic surgery
• Biomechanics
• Hand surgery

Background:

• Intramedullary screws are increasingly used for proximal phalanx (P1) fractures.
• Single- and double-screw configurations are common fixation methods.

Purpose of the Study:

• To assess the biomechanical rotational stability of antegrade one- versus two-screw constructs.
• To evaluate fixation of simulated transverse mid-diaphyseal P1 fractures.

Main Methods:

• Matched pairs of fresh-frozen cadaver upper extremities were used.
• Transverse mid-diaphyseal osteotomies were created in P1s.
• One- and two-screw antegrade fixation constructs were applied and tested for rotational stability using a material testing system.

Main Results:

• Nine matched pairs of simulated P1 fractures were tested.
• No statistically significant difference in mean torque was found between one- and two-screw constructs to produce 15 degrees of malrotation (0.16 Nm vs. 0.26 Nm).

Conclusions:

• Properly fitted antegrade one- and two-screw constructs exhibit similar biomechanical rotational stability for transverse mid-diaphyseal P1 fractures.
• There is no biomechanical advantage to using a two-screw construct over a one-screw construct for rotational stability in P1 fracture fixation.