Volar percutaneous screw fixation of the scaphoid: a cadaveric study.

PURPOSE: To test the efficacy of a previously described technique of angiocatheter-assisted instrument positioning in achieving a central screw position in a cadaveric model for volar percutaneous screw fixation (PSF) of the scaphoid and to quantify the damage to surrounding soft tissue and articular cartilage associated with the procedure.

METHODS: We performed fluoroscopically guided volar PSF of the scaphoid on 10 fresh cadaveric wrists. We then dissected the specimens, analyzed screw position in cross sections of the scaphoid, and described injury to nearby soft tissue structures as well as articular cartilage of the scaphotrapezial joint.

RESULTS: All 10 screws were positioned within the central third of the scaphoid on at least 2 of 3 cross sections, and 8 of 10 screws were positioned within the central third of the proximal pole. Two wrists required a transtrapezial trajectory for satisfactory screw positioning. None of the specimens sustained visible neurovascular damage, and 2 wrists revealed minor tendon damage. Trajectories involving the scaphotrapezial joint violated, on average, 7% of the scaphoid articular cartilage. With a transtrapezial trajectory, 11% of the trapezial cartilage was violated

CONCLUSIONS: Central positioning of the screw is biomechanically superior, and screw position within the central one third of the proximal pole has been associated with faster time to union. Volar PSF achieved satisfactory screw position in the scaphoid. The majority of wrists were amenable to PSF via the scaphotrapezial joint, though a transtrapezial approach was a viable alternative for wrists with restrictive anatomy. Both approaches minimally disrupted the scaphotrapezial joint and surrounding soft tissues.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.