Ring finger metacarpal fracture iatrogenic rotation using an ulnar gutter splint: A cadaveric study

Cohort cadaveric study.

Ring finger metacarpal fractures are often treated with ulnar gutter orthoses incorporating the ring and small fingers. Iatrogenic pronation of the distal metacarpal fragment may occur from overzealous orthotic "molding", resulting in a crossover deformity of the ring finger over the small finger.

The goal of this cadaveric study is to determine whether including the middle finger in an ulnar gutter orthotic could lessen the chances of iatrogenic ring finger metacarpal fracture rotation.

Transverse ring finger metacarpal shaft fractures were created in 24 cadaver hands. The ring and small fingers were then placed into an intrinsic plus position, simulating the application of an ulnar gutter orthotic. Weights of 2.5, 5, and 10 pounds were applied to the ring and small fingers to simulate iatrogenic-induced fracture pronation. The amount of rotational displacement at the fracture was measured, and the protocol was repeated, including the middle finger in the intrinsic plus position. Mann-Whitney-Wilcoxon test was used for statistical analysis.

There was an increase in distal fragment rotation with increasing weight. Fracture displacement was greater with the 2-finger position than the 3-finger at all weight levels; this reached statistical significance at 10 lbs (2.8 vs 1.8 mm).

Application of an ulnar gutter orthotic including only ring and small fingers can rotate the distal fragment of a ring finger metacarpal shaft fracture such that overlap could occur with the small finger. Including the middle finger in ulnar gutter splints will mitigate against the rotation of the ring finger metacarpal shaft fracture.