Muscle fibre damage and regeneration resulting from surgical limb distraction

Using an animal model of limb distraction, the extent of muscle fibre damag e and atrophy resulting from distraction at two different rates (1.3 or 3.0 mm day(-1)) was investigated. It was found that at the high rate of distra ction there was a significantly greater loss of range of joint movement and more muscle fibre atrophy and fibre damage than at the low rate. Muscle fi bre damage is usually followed by regeneration. This involves the expressio n of the neonatal form of myosin heavy chain, which can therefore be used a s an indicator of regeneration. It was found that whilst many more fibres s howed evidence of damage at the high compared to the low rate, the number o f fibres expressing neonatal myosin was significantly reduced, indicating t he presence of a population of fibres which was undergoing degeneration wit hout subsequent regeneration. Thus it would appear that beyond a certain ra te of distraction, regeneration may be insufficient to replace contractile material damaged by overstretching. It is suggested that these fibres are r eplaced with connective tissue. This process may contribute to the muscle w eakness and loss of range of joint movement which sometimes accompanies lim b distraction procedures. Copyright (C) 2001 S. Karger AG, Basel.