MATRIX DAMAGE AND CHONDROCYTE VIABILITY FOLLOWING A SINGLE IMPACT LOAD ON ARTICULAR-CARTILAGE

An impact load was applied to full-depth circular samples of articular cartilage in vitro and the effects of impact energy and velocity on m atrix integrity and chondrocyte viability were studied. Following a se vere impact, calculated to correspond to the energy density over the c artilage surface that might be expected in a manjumping off a 1-m-high wall, the tissue was grossly disrupted, It became elliptical, fissure d, and flattened. Cartilage samples remaining attached to the underlyi ng bone showed less damage at similar drop masses and heights. Chondro cyte viability was found to decrease linearly with increasing impact e nergy. Cartilage biopsies maintained in culture for up to 15 days foll owing impact gained mass over the first 3 days which they did not subs equently lose. The gain in mass increased with the severity of impact and was due to an increased hydration of the tissue. Scanning electron microscopy and light microscopy showed fissures penetrating the tissu e but which were never found to pass through the full depth. They were commonly oriented at about 45 degrees to the plane of the surface and gave the appearance of being deflected parallel to the surface on rea ching the transition zone. This produced a ''delaminating'' effect whe re the surface zone was separating from the deep zone. (C) 1995 Academ ic Press, Inc.