The effect of limb lengthening on articular cartilage. An experimental study

Limb-length discrepancy is a relatively common problem in children. Limb lengthening has traditionally been indicated for projected or actual length discrepancies exceeding 5 cm. Rapid distraction methods of limb lengthening, introduced by Codivilla and popularized by Wagner, have had unacceptably high complication rates. Gradual incremental distraction methods have resulted in improved bone genesis, yet the problems of soft-tissue contracture and decreased joint range of motion have not been solved. A pilot canine study was undertaken to prove the hypothesis that extended limb lengthening can result in injury to articular cartilage. Seven mature beagles underwent application of a transosseous circular fixator to their right femora and a periosteal-sparing osteotomy of the distal right femora. Distraction to a 30% increase over initial femoral length was performed at a rate of 0.75 mm daily in three increments in six dogs. One dog served as a sham-operated control. Free cage activity was allowed postoperatively. At the conclusion of lengthening, experimental and contralateral knee joints were harvested. They were assessed grossly, decalcified, and sectioned sagittally through the femoral and tibial condylar contact surfaces. All sections were stained with safranin-O and assessed histologically. One dog was eliminated from the study because of pin-site sepsis. The five animals who completed lengthening demonstrated gross cartilage fibrillation. Loss of proteoglycan staining was seen in three animals and frank cartilage necrosis in two. The control limbs and sham-operated limb demonstrated no gross or microscopic abnormalities. These findings confirm direct evidence of cartilage injury during limb lengthening.