Incomplete histologic healing and diminished biomechanical strength of meniscus-bone interface after medial meniscus posterior root transosseous repair in a goat model.

ABSTRACT

PURPOSE: To enhance the understanding of histological healing after repairing medial meniscal posterior root tear (MMPRT) at an early stage, utilizing a goat model. METHODS: Eighteen adult goats, totaling thirty-six knee joints, were allocated into three groups (n = 12) Sham group (Sham), Root Tear group (RT), and Root Tear with Transosseous Suture group (RTS). At 12- and 24-week intervals post-surgery, all the knees were harvested for imaging, macroscopic, histological, and biomechanical assessments. RESULTS: The intact root served as a meniscus-bone interface which connected the tibial and the circular fibers of the meniscus, with a bony insertion and a root-meniscus transition. A direct-fibrous-connection displayed at the bony insertion proximal to the synovium in the RTS group, while the remaining regions of the root displayed indirect-fibrous healing. The healing in the RT group was disjointed and reminiscent of scar tissue. The RTS group exhibited a more pronounced coronal extrusion compared to the Sham group (0.42 ± 0.09 vs. 0.19 ± 0.02, P = 0.0012) but was improved relative to that of the RT group (0.49 ± 0.02, P = 0.0028). The failure load and stiffness of the RTS group were notably higher than those of the RT group, with a strength of 42.67% and a stiffness of 83.75% of the intact root. All the samples ruptured at the root-meniscus transitions. CONCLUSION: The incomplete healing may be attributed to the histological factors underlying the low healing rate and persistent MME. Notably, the region attached to the posterior-cruciate-ligament exhibited superior healing compared to other regions of the bony insertion in the repaired group. Conversely, the root-meniscus transition displayed discontinuity, representing a mechanical weakness in the healing process. CLINICAL RELEVANCE Modifications of bone tunnel positioning and suture placement could be undertaken in subsequent studies to particularly enhance the healing of the root-meniscus transition.