Simulated wrist fractures displace in well molded casts and splints under fall simulation forces: A cadaveric study

Distal radius fractures are commonly treated with cast/splint immobilization, but variations exist in activity restrictions.

Fractures of the distal radius/ulna were created in cadaveric forearms. A force was applied through the long axis of the forearm simulating a ground-level fall. Each sample underwent testing in a short-arm well-molded fiberglass cast and a commercial fracture splint. Initial and final position lateral radiographs at 0 N and 400 N of force and dynamic fluoroscopy were taken for calculation of the primary outcome, change in volar tilt. Secondary outcomes were change in radial height and inclination, with comparison of these parameters between cast and splint testing. Statistical analysis employed paired t-tests.

Ten adult cadaveric forearms (6 female, mean age 58.5 ± 17.4 years, BMI 25.7 ± 5.9) were included. Mean overall change in volar tilt, radial height, and radial inclination was 13.3°, 6.3 mm, and 0.5°, respectively. Alignment was similar pre-and-post testing between casted and splinted specimens across all forces. Change in dorsal angulation of fractures from 0 to 400 N of force was comparable when casted and splinted (13.3 ± 9.2° vs 13.2 ± 8.7°, P = 0.945). Fracture displacement reached >10° of dorsal tilt in both groups at 29.2% and 40.8% of idealized adult (70 kg) and adolescent (50 kg) body weights, respectively.

Mean change in volar tilt suggests immobilized fractures in cast or splint may displace with ground-level fall mechanisms. Fracture displacement was similar between short-arm casts and wrist splints. Clinical practice guidelines should be developed for patients with cast-immobilized healing fractures.