A Prospective Study of Changes in Muscle Dimensions Following Free‐Muscle Transfer Measured by Ultrasound and CT Scanning

&NA; A retrospective study demonstrated that noninnervated free‐muscle flaps do not lose bulk when evaluated at a mean of 41 months. The purpose of the present study was to evaluate changes in muscle bulk in noninnervated freemuscle transfers prospectively. This study included 22 flaps (17 latissimus dorsi, 4 rectus abdominis, and 1 gracilis). The thickness of the muscle was measured by ultrasonography preoperatively and 2 and 6 weeks and 3, 6, 9, 12, 15, 18, and 23 months postoperatively. The volume of the muscle was measured by computed tomographic (CT) scan preoperatively and 2 and 6 weeks and 3, 6, and 9 months postoperatively. Postoperative data were normalized to the preoperation measurements. The results demonstrated that the thickness of the muscle increased by a mean of 2.4 times (range 0.9 to 3.9) compared with the initial thickness in a 2‐week period (p < 0.05), 2.0 times (range 0.9 to 4.2) in 6 weeks (p < 0.05), 1.7 times (range 0.8 to 4.2) in 3 months (p < 0.05), 1.5 times (range 0.6 to 3) in 6 months (p < 0.05), and 1.2 times (range 0.4 to 2.8) in 9 months (not significant). Thereafter, the mean thickness was the same as the initial thickness. CT scan measurements of the muscles confirmed the ultrasound findings. Our prospective study of free‐muscle flaps found significant swelling that peaks at 2 weeks and extends until 6 months after the operation. This study also demonstrated that ultrasound evaluation of thickness gives the same conclusion as volumetric measurement by CT scanning. (Plast. Reconstr. Surg. 97: 1443, 1996.)