Abstract
PURPOSE: To address a gap in translational research by developing a preclinical sheep model of medial meniscus anterior root (MAR) repair in vivo and to compare probabilities of potential pitfalls and difficulties with humans. METHODS: Preoperative planning and surgical procedures applied to patients were adapted to adult sheep. Eight healthy, skeletally mature, female Merino ewes between 2 and 4 years of age underwent a mini-open medial parapatellar approach to both stifle joints without luxating the patella. Next, the MAR was transected in 16 knees (8 sheep) resulting in a subtype 2A tear according to the LaPrade classification, followed by a transtibial pull-out repair through a 3.2 mm diameter bone tunnel with a reinforced Mason-Allen suture and non-absorbable suture material. Animals were followed until 21 days after surgery. RESULTS: The surgery time per knee ranged between 30 and 50 min (mean, 40.0 ± 7.8 min). The surgical technique was safe without intra- or post-operative complications. Solid repair is most likely if the following surgical principles are respected: (1) Selection of the MAR and the open technique allow for elegant tunnel positioning and less post-operative loading stress due to the normal extension deficit of sheep; (2) careful preparation of the MAR is mandatory; (3) considering the oval shape of the MAR attachment (MARA) results in anatomic tunnel placement; (4) robust suture placement and configuration avoids suture cut out. The probabilities of potential pitfalls and difficulties differ from the human situation. CONCLUSION: A clinically adapted MAR repair model in adult sheep was developed following its complete transection close to the MARA, followed by an open transtibial pull-out repair. The surgical technique was safe without intra- or short-term post-operative complications. This model may be suitable to study the biomechanics and pathophysiology of meniscal root injuries and their repair. LEVEL OF EVIDENCE: Level IV.