Arthroscopic evaluation of scaphoid waist fracture stability and the role of the radioscaphocapitate ligament.

PURPOSE

The purpose of this article is to arthroscopically evaluate the effect of forearm rotation on scaphoid fracture displacement and the impact of intra-articular ligament sectioning.

TYPE OF STUDY

Controlled laboratory study.

METHODS

Scaphoid fracture stability is studied arthroscopically in 10 cadaveric upper limbs. Displacement of the osteotomized scaphoid with and without forearm rotation is arthroscopically evaluated before and after radioscaphocapitate (RSC) ligament sectioning.

RESULTS

No rotation at the fracture site was identified in full pronation and full supination with the wrist immobilized. With the RSC ligament intact, no immobilization, and the wrist fully pronated, 25% of scaphoid fractures rotated less than 1 mm, 62.5% rotated 1 to 2 mm, and 12.5% rotated more than 2 mm. After sectioning the RSC ligament, the fully pronated wrist resulted in rotation of less than 1 mm in 75% and 1 to 2 mm in 25%. No rotation at the fracture site was seen with supination, with or without immobilization. No difference was found between loaded and unloaded trials.

CONCLUSIONS

Based on this observational data, it appears safe to use a below-elbow thumb spica cast in the treatment of minimally displaced scaphoid waist fractures. Sectioning of the RSC ligament resulted in reduced amount of rotation at the scaphoid waist fracture; thus the RSC ligament may be a deforming force rather than a stabilizing force in scaphoid waist fractures. Arthroscopy may be a valuable tool in the study of the effect of ligament sectioning on fracture stability.