The histology of free microvascular muscle flaps in 19 patients was studied prospectively. Biopsies were taken during operation, and after 2 and 6 weeks, as well as 3, 6, and 9 months, postoperatively, fixed and stained using the van Gieson method. Fiber diameters were analyzed morphometrically and fiber types defined immunohistochemically using myosin fast antibody. During the nine-month follow-up period, mean muscle fiber diameter decreased significantly (P < 0.01), type-1 fibers atrophied significantly (P < 0.05) compared to type-2 fibers, and the percentage of type-2 fibers increased from a mean of 56% intraoperatively to 73% at 9 months. Fatty change and fibrosis were already present 2 weeks after operation and increased with the duration of follow-up. The decrease in muscle fiber diameter 9 months after free flap transfer correlated with clinical factors such as the delay of reconstructive surgery, recipient site, postoperative infection, and postoperative immobilization. The present results confirm that type-specific atrophy related to denervation appears and indicates that clinical events other than denervation influence the muscle atrophy seen in human free muscle flaps. These findings focus attention on the role of muscle regeneration, reinnervation, and revascularization taking place after free flap transfer.

The two-stage operation for reanimation of long-standing facial paralysis by cross-facial nerve grafting and later free microneurovascular muscle transfer has been the treatment of choice for nearly 25 years. However, the functional outcome may be unpredictable. We therefore need to know more about the factors that influence the final result. We have recorded the long-term results of microneurovascular surgery in facial paralysis, and evaluated which factors influenced the functional outcome. Twenty-seven of 40 patients aged 7 to 65 years (mean 40) operated on at Helsinki University Hospital between 1986 and 2000 were available for interview and video recording. The gracilis, latissimus dorsi, and serratus anterior muscles were used for microneurovascular transfer in 11, 10, and 6 cases, respectively. The outcome of microneurovascular muscle transfer was graded on House's scale 1 to 6. The mean follow-up period was 8.5 years (range 2 to 15). Sixteen patients (59%) displayed only mild or moderate dysfunction (grades 2 to 3) after reconstruction. In 8 patients (30%) dysfunction was graded as moderately severe, and in 3 (11%) as severe. There was a correlation between final functional outcome and the follow-up time after microneurovascular facial reanimation. The longer the follow-up time after muscle transplantation the poorer the functional result (p = 0.003). Twenty-one patients (78%) considered that their quality of life was better or much better after facial reanimation. Patients' satisfaction correlated with a good functional result.

Reinnervation, muscle regeneration, density of microvessels, and muscle-type specific atrophy were studied 3-4 years after surgery in surgically nonreinnervated free microvascular muscle flaps to 13 patients transplanted to the upper or lower extremities. Routine histology and immunohistochemistry for PGP 9.5 and S-100 (neuronal markers), Ki-67 (cell proliferation), myosin (muscle fiber types), and CD-31 (endothelium) were carried out, and results were analyzed morphometrically. Three to 4 years after surgery, severe atrophy of predominantly slow-type fibers was seen in 9 cases. In 4 cases, muscle-fiber diameter and fiber-type distribution were close to normal. Long intraoperative muscle ischemia and postoperative immobilization were associated with poor muscle bulk in flaps. The density of microvessels in flaps did not differ from control muscles. PGP 9.5 and S-100 immunopositive nerve fibers were detected in 7 patients. Reinnervation was associated with good muscle bulk. In 4 patients, activation of satellite cells was evident. The results suggest that in some cases, spontaneous reinnervation may occur in free muscle flaps, and that several years after microvascular free flap transfer, the muscle still attempts to regenerate.

No abstract