REPAIR AND RECONSTRUCTION OF THE ANTERIOR CRUCIATE LIGAMENT BY THE SANDWICH TECHNIQUE

The effect of complete ensheathment of the repaired or reconstructed a nterior cruciate ligament (ACL) in the infrapatellar fat pad was studi ed in a rabbit model. Four to 16 weeks after repair of a transected AC L or insertion of an autologous tendon graft these tissues were evalua ted by histology and microangiography. Following ACL repair a high inc idence of ligament atrophy was evident in both the ensheathed (43%) an d the nonensheathed control (54%) group. In functional ligaments a sim ilar sequence of remodelling events was evident in both the ensheathed and the non-ensheathed group: infiltration of the transected area by mesenchymal cells, maturation of these cells to fibroblasts, and incre asing organization of newly formed collagen fibres. An initial hyperva scular reaction was followed by a decrease in the number and an increa se in the longitudinal orientation of blood vessels. Despite a similar sequence of remodelling events, however, this process was considerabl y accelerated in repaired ligaments ensheathed with infrapatellar fat pad compared with non-ensheathed controls. At 16 weeks only the enshea thed repaired ACL resembled the normal ACL morphologically, even thoug h it was still hypercellular. The tendon autograft followed a similar course from an initially avascular and acellular tissue towards a stru cture similar to the normal ACL. In the ensheathed ligaments and tendo n grafts vascular and cellular ingrowth as well as subsequent maturati on were again accelerated. This effect may be attributable to improved revascularization and cell repopulation, as well as protection from s ynovial fluid by the surrounding fat pad.