A cadaveric morphometric study of the attachments of the anterior cruciate ligament in the South Indian Population

INTRODUCTION: Anterior cruciate ligament (ACL) reconstruction is one of the most common arthroscopic knee surgeries done in the World. As we acquire greater knowledge about the biomechanics of the ACL, it is increasingly apparent that the aim of a successful ACL reconstruction is restoration of the patient’s anatomy. The ACL has, for some time, been described as consisting of two main functional bundles- the Antero- medial (AM) and the postero- lateral (PL). These bundles have been shown to behave differently in the tensioning of their fibres in varying degrees of knee flexion and rotation. This has led to the development of the ‘double bundle’ ACL reconstruction technique, which is entirely dependent upon the anatomical placement of tunnels and differential tensioning for physiological load bearing patterns. The results of the more commonly done ‘isometric’ single bundle ACL reconstruction have also been shown to rely on the placement of the femoral tunnel. As newer, more anatomical techniques evolve, a demand for quantitative anatomical description of the attachments of the ACL and its two bundles in specific populations has arisen. Several papers in the Western population doing so have been published, but as all knees are not the same, regional data is warranted. It is hypothesized that, because knees in a particular population are geometrically similar, measurements to locate the bundle attachments could be correlated with measurements that describe the size of the knee. MATERIALS AND METHODS: 22 preserved cadaveric knees with intact ACLs were dissected. The AM bundle was identified by anterior drawer in full external rotation and marked. The ACL was cut mid- substance and the knee subluxated. The lateral condyle was taken off and after cutting the remaining ACL, the femoral attachment of the ACL was measured with Vernier callipers and digitally photographed with a high resolution digital camera. The distances of the centre of the attachment from standard arthroscopic landmarks were also measured using callipers. The tibial attachment was similarly measured and photographed. The photographs were processed in the software AutoCAD (Autodesk Inc., San Rafael, Cal.) and the exact area of the attachments was calculated, along with the position of their centres along standard measurement grids. Maximum included diameter circles were plotted and the required graft diameter predicted. To test the hypothesis, a Pearson coefficient was applied to the collected data in order to check the correlation of the measurements to the size of the knee. CONCLUSION: We have inferred from this study that the intra- articular landmarks on the tibial plateau are a good initial point for the accurate location and placement of the tibial tunnel for both a single bundle and a double bundle ACL reconstruction. - We have also presented useful data for the location and diameter of tunnel placement for the footprint for the femoral socket for ACL reconstruction. - The use of this data, aided especially by an Arthroscopic Ruler or adjustable guides designed to reference from these landmarks, could be a remarkably useful method of consistently locating the tibial footprint. we encourage the arthroscopic surgeon to have the arthroscopic ruler as an important part of the ACL armamentarium. - The data measuring the location of the footprints with relation to anatomic landmarks may be very useful in the future as baseline references for Computer Navigated ACL Reconstruction in South Indian patients.