How does a reduction in the radial bow, in addition to a rotational deformity of the radius, affect the range of motion of the forearm: an anatomical cadaver study.

Background: This study aimed to investigate the anatomical effect of radial rotational deformity and reduced radial bow on the forearm range of motion (ROM) to improve outcomes in severe forearm diaphyseal fractures and malunion. Methods: Twenty upper limbs of 10 fresh-frozen cadavers were amputated at the humerus and distally at the carpometacarpal joint and examined. Soft tissues, except the interosseous membrane, articular capsule, and pronator quadratus muscle, were removed. The deformity was modeled by cutting at the maximal bow of the radial diaphysis and fixing it with an external fixator. Radial deformities of 20° and 40° in pronation and supination were modeled to assess ROM. Thereafter, a model with a reduced radial bow was created, and ROM was evaluated in addition to the rotational deformities of 20° and 40° in pronation and supination. The cadavers were divided into the normal and reduced radial bow models, and the results were evaluated statistically. Results: In both the normal and reduced radial bow models, malunion in the pronation model led to a loss of range of supination, whereas malunion in the supination model resulted in a loss of range of pronation. The reduced radial bow model showed a statistically significant 20% and 19% loss in forearm pronation and supination, respectively ( Conclusion: In addition to radial rotational deformity, a reduction in the radial bow contributes to reduced forearm rotation. Ensuring proper radial bow formation is crucial for achieving a good postoperative ROM when treating radial diaphysis fractures and malunion occurring at the maximum radius bow.