New insights in anterior cruciate ligament morphology: implications for anterior cruciate ligament reconstruction surgeries

The frequency of injury of anterior cruciate ligament (ACL), the importance of anatomy in surgical repair and potential of the injured ACL to predispose to osteoarthritis necessitates the need for understanding its precise anatomy. Available studies have focussed on tunnel positioning and hence attachment site of the ligament. Few studies which have focussed on morphology reflect ambiguities in size, fibre bundle, number and disposition. Since a near anatomical repair of the ACL is the treatment of choice, the present study was planned to describe the morphology of ACL. Twenty-two ACL (11 right and 11 left) isolated from knee joints of collection of adult embalmed lower limbs were utilised for the study. The ACL morphology and morphometry were studied for footprints and fibre bundles. Three distinct bundles of differing lengths constitute a spiral ACL complex. These bundles are positioned as- intermediate with posteromedial and anterolateral flanking in respective positions. The tibial and femoral footprints are paw-shaped and oval respectively. Tibial footprints are approximately 2.5 times larger in area than the femoral footprints. The unique morphology of ACL vis a vis its spiralization, and its mechanical advantage of in terminal extension and conjunct rotation of knee (which are peculiarly human trait) are discussed. It is recommended to utilize the concept of spiralization and differing bundle length in ACL surgeries to achieve the favourable clinical outcome.