Biomechanical assessment of brachioradialis pronatorplasty.

Objectives: Transfer of the brachioradialis muscle, proposed by Özkan et al. can be applied to cases, in which, the biceps rerouting technique is not appropriate for the correction of forearm supination contracture and restoration of active pronation. We have aimed to assess the biomechanical effects of the brachioradialis transfer.

Methods: Pronation strength was acquired in nine fresh-frozen cadaver forearms by applying rerouting of the brachioradialis muscle through interosseous membrane (Group 1) or transferring the same muscle to the distal insertion of extensor carpi ulnaris (ECU) (Group 2). Then, a force of 5 to 35 N was applied to the muscle and the range of forearm rotation and rotation strength were measured. The normalities of the data were analyzed by Shapiro-Wilk test. Comparisons between the groups were made with independent-sample t-test and comparison of the data, obtained from the same group, was carried out with paired-sample t-test and Bonferroni correction.

Results: A maximum of 74° (with a mean of 61°) gain of pronation with rerouting and a maximum of 72° (with a mean of 65°) gain with ECU transfer of brachioradialis muscle were observed. A significant regression was also found in the first group. Regression constant was - 9.59 (p = 0.001, 95%: -13.20; -6.00) for the applied force of 2.06 N (p = 0.001, 95%: 1.90; 2.22). Furthermore, a significant regression was found in the second group. Regression constant was - 9.73 (p = 0.001, 95%: -13.13; -6.34) for the applied force of 1.91 N (p = 0.001, 95%: 1.76; 2.06).

Conclusion: The brachioradialis muscle works as a pronator in full forearm supination. However, when the forearm comes close to the neutral rotation, due to the lateral location of the proximal insertion, the brachioradialis muscle loses this pronator effect. The additional release or lengthening of contracted soft tissues increases the range of pronation.