Surgical induced models of joint degeneration in the ovine stifle: Magnetic resonance imaging and histological assessment

• sMOAKS is a reliable semi-quantitative MR scale to evaluate and quantify joint degeneration in the ovine knee.
• sMOAKS presents a high correlation with Mankin and OARSI scales in the evaluation of the femoro-tibial articular cartilage.
• ACLt induces the highest degree of degeneration at the expense of an increase presence of osteophytes.
• Articular cartilage and osteophytes were the predominant affected structures. Bone marrow lesions, were poorly identified.
• ACL transection proved to be the intervention that produced the highest amount of degeneration 8 weeks postoperatively.

BackgroundThe purposes of this study were to (1) validate and assess the reliability of a modified magnetic resonance semi-quantitative score (sheep Magnetic Resonance osteoarthritis Knee Score (sMOAKS)) to evaluate joint degeneration in the ovine knee and to (2) investigate whether the transection of the anterior cruciate ligament (ACL), isolated or in combination with meniscal injuries, reproduce the degenerative changes described in the meniscectomized sheep.MethodsTwenty sheep were randomly subjected to one of the following injuries to induce osteoarthritis (OA): ACL transection (ACLt), mid-body transection of the medial meniscus, ACLt combined with complete medial meniscectomy and complete medial meniscectomy. OA assessment was performed eight weeks postoperatively with sMOAKS, Mankin and Osteoarthritis Research Society International (OARSI) histological scores.ResultssMOAKS showed very good to excellent reliability (kappa = 0.61 to 1.0) for the majority of features evaluated. sMOAKS revealed small differences between groups (p < 0.05) being the ACLt group the most affected. We observed a strong positive correlation between the three scales in the evaluation of femoro-tibial articular cartilage (AC) (r = 0.829, r = 0.917, r = 0.879).ConclusionssMOAKS is a reliable semi-quantitative Magnetic Resonance (MR) scale to evaluate and quantify the effect of different OA induction lesions in the ovine knee and presents a high correlation with Mankin and OARSI scales in the evaluation of femoro-tibial AC. Although minor differences were observed between the different surgical procedures for the induction of OA, ACLt proved to be the intervention that produced the highest amount of degeneration eight weeks postoperatively.Level of EvidenceII