Summary
This laboratory study provides insight into the pathophysiology of ramp lesions frequently associated with ACL injury. In order to restore anatomy, it is mandatory to reestablish meniscotibial ligament continuity in ramp repairs
Abstract
Background
Some authors have suggested the semimembranosus tendon is involved in the pathophysiology of ramp lesions. This led us to conduct a gross and microscopic analysis of the posterior horn of medial meniscus and structures inserted on it.
Hypothesis
(1) The semimembranosus tendon has a tendinous branch inserting into the posterior horn of medial meniscus and (2) the meniscotibial ligament is inserted on the posteroinferior edge of the medial meniscus.
Study Design: Descriptive laboratory study, level 4
Methods
Fourteen fresh knees were dissected. From each cadaver donor, a stable anatomical specimen was harvested en bloc, including the medial femoral condyle, medial tibial plateau, whole medial meniscus, cruciate ligaments, joint capsule, and distal insertion of the semimembranosus tendon. The harvested blocks were cut along the sagittal plane to isolate the distal insertion of the semimembranosus on the posterior joint capsule and the posterior horn of medial meniscus in a single slice. Histological slides were made from these samples and analyzed under a microscope.
Results
In all knees, gross examination found a direct branch of the semimembranosus and a tendinous capsular branch ending behind the posterior horn of medial meniscus. This capsular branch protrudes over the joint capsule, over the meniscotibial ligament below and the meniscocapsular ligament above, but never ends directly in the meniscal tissue. The capsular branch is 14.3 ± 4.4 mm long. The direct tendon inserts 11 ± 2.8 mm below the articular surface of the tibial plateau. The meniscotibial ligament inserts on the posteroinferior edge of the medial meniscus, and the meniscocapsular ligament insertion is on its posterosuperior edge. Highly vascularized adipose tissue was found, delimited by the posterior horn of medial meniscus, meniscotibial ligament, meniscocapsular ligament and capsular branch of the semimembranosus tendon.
Conclusion
In all knees, our study found a capsular branch of the semimembranosus tendon inserted behind the medial meniscus. The meniscotibial ligament is inserted on the posteroinferior edge of the medial meniscus. Histological analysis of this area revealed that this ligament inserts differently than previously described in the literature.