Complete ACL/MCL deficiency induces variable degrees of instability in sheep with specific kinematic abnormalities correlating with degrees of early osteoarthritis

Abstract

People are not equally disabled by combined anterior cruciate ligament (ACL)/medial collateral ligament (MCL) injuries, nor do they all develop osteoarthritis (OA). Although biological/biomechanical causes are not clear, some association presumably exists between joint instability and OA development. We hypothesized that degree of OA development following standardized complete ACL/ MCL injuries will vary directly with the degree of biomechanical abnormality between individuals. Three groups of sheep were used to test the hypothesis: 17 normal, 9 ACL/MCL transected, and 7 sham animals. Normal joints were assessed morphologically while sham and experimental animals had gait assessment pre-and at 4 and 20 weeks post-surgery, with cartilage and bone changes being mapped and graded at sacrifice at 20 weeks. Sham joints were morphologically normal and had only one minor kinematic change at 20 weeks. Although variable, ACL/MCL deficient animals showed significant kinematic abnormalities in 4/6 degrees of freedom (DOFs), as well as cartilage/bone damage by 20 weeks (p < 0.05). Linear regression analysis revealed that changes in medial-lateral (ML) translation were related to the current level of joint degradation as represented by total gross OA score (p ¼ 0.0044, R 2 ¼ 0.71) in the ACL/MCL transected group. Even identical ACL/MCL injuries result in inter-animal variations in instability and OA, however significant kinematic abnormalities in ML translation do relate to early OA in sheep.

Gait changes of the ACL-deficient knee 3D kinematic assessment

“…This discrepancy could arise from the difference in the time since injury, (the period between the occurrence of injury and the time of kinematic evaluation) ( Table 1). The average time of injury in our study was 5.7 months ± 5.3, compared to Fuentes et al [14] study where the average time of injury was 22 months (from 5 to 78 months). Additionally, in Andriacchi and Durby work [2] where less external rotation in ACLD knees was found, the time of injury was 127 ± 142 months (from 3 to 400 months).…”

Knee joint contact mechanics during downhill gait and its relationship with varus/valgus motion and muscle strength in patients with knee osteoarthritis

“…Frank and colleagues 46 previously reported an association between increased medial/lateral knee joint translations during the mid-stance phase of gait with cartilage and bone damage in unstable sheep knees 20-weeks after anterior cruciate ligament (ACL)/medial collateral ligament transection. Anderst and colleagues 47 also reported that increased velocity of the medial compartment joint contact point in the early stance phase of running is associated with greater medial compartment cartilage damage in unstable canine knees after 2 years.…”

Animal Models of Osteoarthritis: Challenges of Model Selection and Analysis

“…Published methods have included scoring based on apparent lameness (40), measurement of stride length and limb rotation from inked paw prints in rats (48), measurement of dynamic force application using a pressure-sensitive walkway (42,46), and fluoroscopic measurements of hind limb motion (47). In larger animals, gait and functionality measures such as kinematic marker analysis, ground reaction force measurements, and observational gait assessment have been applied to study OA-related changes for conditions including dog hip OA (49), lameness in horses (50), and postsurgical sheep knee OA (51). Of note, all of the commonly used animal models of OA use quadruped animals, with different compensatory gait alterations compared to bipedal humans, and with variable effects on gait according to the affected joint.…”