Effect of rate of distraction on loss of range of joint movement, muscle stiffness, and intramuscular connective tissue content during surgical limb-lengthening: A study in the rabbit

Surgical lengthening of limbs often results in loss of range of joint movem ent and this has been shown to be associated with an increase in passive te nsion and an increase in collagen content of the muscles. In this study, we have investigated the length/tension properties and the connective tissue component of muscle distracted at three different rates in order to determi ne whether low rates of distraction would enable the connective tissue comp onent, as well as the contractile component (number of serial sarcomeres), to adapt more completely to the increased functional length of the muscle a nd thus lead to improved range of joint movement. It was found that loss of range of movement varied with rate of distraction. At the low rate, there was no change in the passive tension or collagen content compared to muscle s from sham-operated animals, and range of movement was significantly great er than at the other rates. At the medium rate, although the muscles showed good adaptation in terms of serial sarcomere number, passive tension and c ollagen content was increased and range of movement reduced, indicating tha t changes in the connective tissue component are important factors in loss of joint movement. In the case of muscle distracted at a high rate, failure of the muscle fibres to add on sufficient sarcomeres, combined with change s in the connective tissue, resulted in almost total loss of joint movement . (C) 1999 Wiley-Liss, Inc.