Force Recovery Assessment of Functioning Free Muscle Transfers Using Ultrasonography

Purpose To evaluate the usefulness of ultrasonography for measurement of functioning free muscle transfer strength and estimate the capacity and potential of ultrasonography measurement. Methods Twenty-five patients underwent functioning free muscle transfer for brachial plexus injury. The cross-sectional areas (CSAs) of the transferred muscle and the contralateral gracilis (control) were measured using ultrasonography. First, the reliability and reproducibility of the ultrasonography measurements of the muscle CSA was investigated. Next, force recovery was evaluated by calculating the contraction ratio (CR), which was defined as the value equal to the CSA of the transferred muscle under maximum isometric contraction divided by the CSA value in a complete rest position. The CR of the contralateral gracilis was calculated in the same manner. The CR of the transferred muscle and the control were compared statistically. We also analyzed the correlation between the CR of the transferred muscle and other measurements of muscle strength. The follow-up duration was 24 to 87 months after surgery. Results The reliability and reproducibility of the ultrasonography measurements was determined statistically. The CR of the transferred muscle (1.30 ± 0.12) was significantly greater than that of the contralateral gracilis (1.22 ± 0.13). Furthermore, the CR of the transferred muscle showed significant correlations with both manual muscle testing and elbow arc of motion. Conclusions Ultrasonography measurement of transferred muscle can easily indicate the recovery process of rehabilitation in a quantitative and dynamic manner. This study demonstrated that ultrasonography has the capacity to evaluate force recovery objectively. Type of study/level of evidence Therapeutic IV.