A prospective study of changes in muscle dimensions following free-muscle transfer measured by ultrasound and CT scanning.

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 free-muscle 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.