Time-dependent changes in medial meniscus kinematics and attachment strength after anterior root injury and repair in a large animal model

This study investigated joint kinematics and attachment tensile mechanics following resection of the medial meniscus anterior attachment. A secondary objective investigated the repair of the attachment. Yucatan minipigs underwent unilateral surgery for either Injury (en bloc) resection of the anterior attachment of the insertional ligament, (a portion of the cranial medial meniscotibial ligament) or Repair (immediate repair with a suture anchor), with the contralateral knee as Intact control. Evaluation at 6 weeks and 6 months included joint kinematics measured from MRI acquired under knee compression and tensile testing of the attachment. Injury resulted in large levels of meniscus extrusion, despite the development of a fibrovascular scar. At 6 weeks, the meniscus extruded 1.95 mm more than Intact; at 6 months, this extrusion was reduced to 0.77 mm. Under an applied 1x body weight load, the meniscus further extruded and was not different with treatment or time. During attachment tensile testing, elongation was 0.6 mm for Intact, following Injury, elongation was 2.7 mm at 6 weeks and was partially restored to 1.5 mm at 6 months. Despite this, the cartilage wear worsened over time. Repair was inadequate to avoid the extrusion or cartilage wear seen in the injury group at 6 weeks, so it was not continued for the 6-month group. This study demonstrates that while meniscus injury is useful to study cartilage degeneration, a holistic consideration of the role of the meniscus itself, including its changing material properties and its impact on joint mechanics during injury, repair, and rehabilitation, are key factors contributing to overall joint health.