TENOTOMY AND REPAIR OF LATISSIMUS-DORSI MUSCLES IN RATS - IMPLICATIONS FOR TRANSPOSED MUSCLE GRAFTS

The functional properties of latissimus dorsi (LTD) muscles were evalu ated 160 to 180 days after tenotomy and repair, when grafts had stabil ized. Our hypothesis was that, compared with control LTD muscles, LTD grafts would develop less absolute force and power but that the specif ic force and normalized power would not differ. Expressed as a percent age of the value for control LTD muscles, values for grafts were 67% f or muscle mass, 74% for mean single fiber cross-sectional area, 56% fo r maximum absolute isometric tetanic force, 64% for maximum absolute a verage force during shortening, and 70% for maximum absolute power. Co mpared with control LTD muscles, grafts showed no significant differen ces either in the number of fibers in the total muscle cross section o r in the optimum velocity for the development of power. When force and power of grafts were normalized for total fiber cross-sectional area and mass, respectively, only the value for maximum specific force (84% of control value) was significant. The mechanisms responsible for the decrease in specific force after tenotomy and repair are not known. I n contrast to the deficit in maximum specific force, the 30% deficit i n maximum absolute power of grafts compared with control LTD muscles w as explained completely by the 33% smaller muscle mass.