Behavior of tendons during lower-leg lengthening in dogs using the Ilizarov method

Twenty-two dogs were provided with a circular fixator. Lengthening of the r ight lower leg by 2.5 cm was performed on 18 dogs 5 days after tibial osteo tomy using a distraction rate of 0.5 mm, twice per day. Nine dogs with leg lengthening and two dogs of the control group without leg lengthening were sacrificed at the end of the distraction phase of 25 days and the remaining dogs after another 25 days. Post mortem, the tendons of the tibialis anter ior, extensor digitorum longus, peroneus longus, and the Achilles tendon we re taken from the operated-on right side and the left nonoperated-on contro l side and were analyzed histologically. The control group showed no histol ogic changes in the tendons of either side nor in those of the unlengthened left side of the operated-on dogs. Thirty-three tendons (41%) of dogs with leg lengthening were seen to have undergone histomorphological changes. An increase of the peritendinous connective tissue was seen, combined with ch ronic inflammatory cell infiltration in the tendons and/or the epitendinous tissues, edema, tendon fragmentation, necrosis, scarring of the tendons wi th dystrophic calcification and/or ossification, and broadening of the teno synovial sheath. Furthermore, signs of histoneogenesis with growth in the t endons were found. Degenerative changes occurred far more often in the tend ons of the ventral side of the lower leg and a slight pes equinus was regul arly observed in the lengthened extremity. Therefore, pes equinus preventio n and physiotherapy are important in the therapeutic use of lower-leg lengt hening to minimize possible stress-induced damage of the ventral tendons.