The Effect of a Nonanatomic Repair of the Meniscal Horn Attachment on Meniscal Tension: A Biomechanical Study

Purpose: The purpose of this biomechanical study was to investigate the potential effect of a nonanatomic repair of the meniscal horn attachment on the resultant circumferential tension in a large animal model and to show that the circumferential tension of the meniscus affects the local stress of the cartilage. Methods: All investigations were done in the medial compartment of porcine knees. First, the anterior horn attachment of the meniscus was mechanically separated from the surrounding tibial bone and fitted with a force transducer (n = 8). The femorotibial joint was loaded in compression at different flexion angles, and the resultant tension at the horn attachment was recorded. The measurements were done with the horn attachment at its anatomic position and repeated with the horn attachment being displaced medially or laterally by 3 mm. In the second part the local deformation of the cartilage under a femorotibial compressive load was measured at different levels of meniscal hoop tension (n = 5). Results: A nonanatomic position of the horn attachment had a significant effect on the resultant tension (P < .01). Placing the horn attachment 3 mm medially decreased the tension at the horn attachment by 49% to 73%, depending on flexion angle and femorotibial load. The opposite placement resulted in a relative increase in the tension by 28% to 68%. Lower levels of meniscal hoop tension caused increased deformation of the cartilage (P < .05), indicating increased local stress. Conclusions: A nonanatomic position of the horn attachment strongly affects conversion of femorotibial loads into circumferential tension. There is a narrow window for a functionally sufficient repair of meniscal root tears. Clinical Relevance: Although clinical inferences are limited because the specimens used were from a different species, there seems to be only a narrow window for a mechanically sufficient repair of root tears.