Biomechanical measurements of forearm pronosupination with common methods of immobilization

Purpose: To define the pronosupination arc for various types of forearm immobilization. We hypothesized that these methods of immobilization offer control of forearm pronosupination proportional to the loss of elbow motion, and that the Muenster cast may offer the most practical method of limiting forearm motion without eliminating elbow motion. Methods: We enrolled 15 subjects in the study. We took measurements using computerized biometrics with the elbow free of immobilization and in a long-arm cast, a Muenster cast, a removable splint set to 90°elbow flexion, and a splint set to allow elbow flexion permissible by the Muenster cast. We recorded measurements for pronation and supination arcs. Results: We obtained average pronosupination arcs for the unrestricted elbow (189°), long arm cast (11°), Muenster cast (35°), removable splint set to 90°(124°), and splint set to the flexion-extension arc of the Muenster cast (139°). We found statistically significant differences for pronation and supination for all comparisons between immobilization methods, with the exception of the splints compared with each other. The least motion was found in the long-arm cast, whereas the Muenster cast offered the only option allowing minimal pronosupination without strict elbow immobilization. Conclusions: The Muenster cast offers reasonable immobilization of the forearm without fully immobilizing the elbow. The long-arm cast option offers significantly more forearm stability at the cost of any elbow motion. The 2 splints tested do not effectively immobilize the forearm compared with the other modalities tested. Clinical relevance: This study provides good biomechanical support for using a Muenster cast when limiting forearm rotation is desirable.