CLINICAL, MECHANICAL AND HISTOPATHOLOGICAL EVALUATION OF A BIOENGINEERED LONG-TERM BIORESORBABLE SILK FIBROIN GRAFT IN A ONE YEAR GOAT STUDY FOR DEVELOPMENT OF A FUNCTIONAL AUTOLOGOUS ANTERIOR CRUCIATE LIGAMENT

Objectives We hypothesise that a long-term bioresorbable hydrophilic silkworm silk device, the SeriACL(tm) scaffold, can support the development and remodelling of native functional ligament tissue if designed to anticipate the remodelling curve of an ACL graft. This study evaluated the SeriACL scaffold for ACL replacement in a goat model at 3, 6 and 12 months. Methods The ACL of 43 goats was replaced in an arthroscopically assisted procedure. The ACL was excised, a guide pin driven into the femur and 6mm diameter antegrade drilling performed. The tibial tunnel was drilled under direct visualisation. The graft was anchored around a post on the femur, tensioned to 50N and cycled 30x before tibial fixation with a staple and sutures around a post. Animals were clinically, mechanically and histologically evaluated. Results The SeriACL graft did not induce acute inflammation, swelling or initial scar formation as indicated by rapidly declining pain and knee size scores. All animals were weight bearing at 3, 6 and 12 months, with 95% returning to normal gait by 6 months. Lachman showed the majority of knees were clinically stable with a normal range of motion at all times. No gross cartilaginous damage, synovitis or particulate debris in lymph nodes was observed. Collagen development throughout the graft and bone tunnels increased with time. Conversely, inflammation and device mass decreased with time. Fluoroscopy indicated no abnormal bone tunnel findings. Total IgG levels did not increase from pre-surgery levels. AP laxity indicated joint stability at all times. Implant abrasion was observed to varying extents yet mechanical testing revealed tissue development supported increased load bearing over time. Conclusions The SeriACL graft supported autologous development of a mechanically robust, biologically viable ligament which stabilised the goat joint over a 12 month period. Mechanical, clinical and histological results indicated SeriACL graft safety with initial indications of efficacy.