RECOVERY OF MUSCLE TRANSFERS REPLACING THE TOTAL PLANTAR FLEXOR MUSCLE GROUP IN RATS

In rats, combinations of plantar flexor muscles representing similar t o 20, 40, 60, and 80% of the mass of the total plantar flexor group we re transferred orthotopically in the absence of synergistic muscles an d allowed to recover far 120 days. We hypothesized that, compared with their individual control values for structural and functional variabl es, the transfers would display a hierarchical array of deficits, prop ortional to their initial mass and, consequently, inversely proportion al to the relative load on the transfers. Surprisingly, compared with their individual control values, each muscle transfer displayed defici ts of 30-40% in muscle mass, total fiber cross-sectional area, and max imum isometric force, with the exception of the smallest transfer, the plantaris (PLN) muscle, which recovered 100% of its control value for each of these variables. Therefore, except for the PLN transfer, the muscle transfers studied displayed deficits similar in magnitude to th ose reported for muscles transferred in the presence of synergistic mu scles. The greater recovery of the PLN transfer was attributed to the relatively large requirement for force production imposed on this tran sfer due to the average force requirements of the total plantar flexor group.