How Does Torsional Deformity of the Radial Shaft Influence the Rotation of the Forearm?: A Biomechanical Study

Abstract

OBJECTIVE: The aim of this experimental study was to measure the exact influence of isolated torsional deformities at the middle third of the radial shaft on the rotation of the forearm. DESIGN: Biomechanical study in cadavers. SETTING: Trauma Surgery Research Laboratories at the Medical School of Hannover, Hannover, Germany. INTERVENTION: Fourteen intact and fresh cadaver specimens were fixed in a newly developed apparatus that allowed free pronation and supination. A ring fixator was applied to the radial shaft with K-wires that allowed us to stabilize torsional deformities in steps of 10 degrees. The middle of the radial shaft was osteotomized via a small soft tissue window, leaving the other soft tissues, including the interosseous membrane, intact. MAIN OUTCOME MEASUREMENT: Supination and pronation were measured using a goniometer in a standardized fashion. RESULTS: The mean (standard deviation) supination value before osteotomy of the radius was 71.6 degrees (15.2 degrees), and the mean (standard deviation) pronation value was 64.5 degrees (12.4 degrees). Radial osteotomy caused no significant difference in the range of motion before creation of torsional deformities. Supination torsional deformities >30 degrees showed a significant loss of pronation. In turn, pronation torsional deformities >30 degrees resulted in a significant loss of supination. The amount of mean rotational loss was approximately the same in the respective pronation and supination torsional deformities. CONCLUSION: An axial torsional deformity of the radius of >30 degrees causes a statistically significant loss of forearm rotation in fresh cadavers.