Scaphoid fracture displacement with forearm rotation in a short-arm thumb spica cast.
Three-dimensional motion between the fragments of an experimental scaphoid waist fracture was measured during dynamic forearm pronation and supination in a short-arm thumb spica cast with and without applied tendon loads. Metal markers placed in each fragment were tracked using high-speed biplane radiographic image sequences and stereophotogrammetric analysis. Peak displacements (from the intact state) exceeded 1 mm in all specimens, with the largest movements occurring in the radial direction during pronation (mean: 2.1 mm unloaded, 2.5 mm loaded). Total range of displacement motion between fragments exceeded 3 mm (mean ulnar/radial direction: 3.4 mm unloaded, 4.1 mm loaded). Dorsal/palmar and proximal/distal displacements were minimal except at the extremes of forearm pronation/supination. Rotations between fragments were small (within +/- 6 degrees) and varied considerably across specimens. No significant differences were found between loaded and unloaded trials. Thus, in the absence of long-arm thumb spica casting to limit forearm rotation, significant motion between the fragments of a scaphoid waist fracture is likely.
Kaneshiro
S A
SA
Department of Orthopaedic Surgery, Henry Ford Hospital, Detroit, MI, USA.
Failla
J M
JM
Tashman
S
S
D001696:Biomechanical Phenomena; D002348:Carpal Bones / Q000293:injuries*; D002370:Casts, Surgical; D004867:Equipment Design; D005542:Forearm; D050723:Fractures, Bone / Q000473:pathology* / Q000628:therapy; D006801:Humans; D012399:Rotation