Eur J Anat, 21 (1): 1-11 (2017)

Anthropometry of the cruciate ligaments of the knee: MRI study of the human four-bar linkage device

Anna Hernaiz Alzamora¹, Juan I. Mediavilla Arza¹, Jaime Usabiaga Zarranz², Fernando Diez Renovales¹

¹Orthopaedic surgeon, Hospital Universitario Basurto, Bilbao, Spain, ²Orthopaedic surgeon, Hospital Universitario Donosti, San Sebastián, Spain

ABSTRACT The knee acts as a functional unit whose stability depends on the equilibrium of its constituents. The set formed by the cruciate ligaments (CL), the femoral condyles and the tibial plateau, could be understood as a functional unit with a central pivot called the four-bar linkage. The union of the insertion sites of both CL reproduces a crossed union device of four three-dimensional bars that mimic the kinematic behaviour of the knee. The relationship between the femoral and tibial insertions of the anterior and posterior cruciate ligaments (ACL and PCL) is a constant value to be determined in the healthy human population. We included 200 magnetic resonance images (MRI) of healthy knees and measured real distances between the insertion points in the tibia and femur of both CL. We processed these data using the Cruliant-ETSIB® program to show the dimensions of each bar in full scale. We determined absolute variables: ACL, PCL, the distance between tibial insertions (TIDI) and the distance between femoral insertions (FEDI). We measured relative variables as well: TIDI/PCL, FEDI/PCL, PCL/ACL, TIDI/FEDI. There is a human proportion in healthy knees defined by the quotient TIDI/FEDI whose value is 1,45. The use of this quotient is proposed as a reference to optimise the location of the tibial and femoral insertions during reconstructive ligament surgery of the CL, as well as to assess the success of the reconstruction.

Keywords: Cruciate ligaments â?? Knee â?? MRI â?? Four bar linkage â?? Insertion