Computer simulation of forearm rotation in angular deformities: a new therapeutic approach.

A new computer-assisted simulation of forearm rotation based on orthogonal radiographs of the forearm is introduced. A new computer program called STOOPS was developed based on a new kinematic model describing motion of the radius and ulna in regards to forearm rotation. The computer program allows simulation of angular deformities of the forearm and can predict subsequent rotational impairment. To validate the program, the authors compared the actual pronation of 21 patients with angular deformities with the predicted pronation by STOOPS. The mean difference between the simulated and clinically measured pronation was 5.6 degrees (S.D. 9.4 degrees ). There was no statistically significant difference between the measured and simulated values. Using the computer-assisted simulation may help predict impairment of pronation due to angular deformities. If clinical impairment differs from the computed one, other causes such as lesions to the interosseous membrane or the adjacent joints have to be excluded. If values are similar, correction of the angular deformities should result in improvement of forearm pronation.