To determine the relationship between the dimensions of the distal femoral intercondylar notch (ICN) and the composition and metabolism of the anterior cruciate ligament (ACL) in three dog breeds with different relevant risks to ligament rupture and subsequent osteoarthritis (OA).
ICN measurements were obtained from the femurs of Golden Retrievers (high risk), Labrador Retrievers (high risk) and Greyhounds (low risk). Femoral condyle width and height, ICN height and width indices, and notch shape index were measured using Vernier callipers in all dogs. Intact ACLs were obtained from the same dog breeds for a study of the impinged areas and were analysed for collagen content, collagen cross-links, and sulphated glycosaminoglycan (GAG) content, matrix metalloproteinase (MMP)-2 and the tissue inhibitors of metalloproteinases (TIMPs)-1 and -2.
Femoral condyle width and height and ICN width indices were significantly greater in the low risk compared to the high risk breeds (P<0.01 for all parameters). In contrast, the pro (P=0.003) and active (P=0.007) forms of MMP-2 and sulphated GAGs (P=0.0002) were significantly greater in the impinged areas of the ACLs of the rupture predisposed breeds.
Impingement by the ICN on the ACLs of the high risk breeds may result in increased collagen remodelling and increased sulphated GAG deposition, causing reduced structural integrity of the ligament. Altered ACL composition may predispose the ligament to increased laxity leading to joint degeneration and OA. This may have a comparative implication for pathogenesis of ACL rupture in humans.