Pre-operative determination of the optimum graft length for anterior cruciate ligament reconstruction

Abstract

Purpose: Accurate knowledge of the anatomy of the anterior cruciate ligament (ACL) is crucial for successful ACL reconstruction. Incorrect graft lengths and/or tunnel misplacement have to be avoided. If the graft length is incorrect, the patient could risk knee instability, loss of range of motion or failure of graft fixation. The success of ACL reconstruction will be enhanced if the correct length of the graft ligament required, can be predicted in advance. Magnetic resonance imaging (MRI) is currently used for the evaluation of ACL injuries, but is not available to all patients. Apart from examining the morphological properties of the ACL at macroscopic and microscopic levels, this study aimed to determine whether independent factors of an individual can be used to predict native ACL length which could assist in preoperative planning. Methods: Ninety-one adult cadavers were studied. The patellar ligament (PL) length, ACL length, ACL width and the maximum femoral epicondylar width (FECW) were measured. For the radiographic component, 52 patients were sourced to evaluate and compare ACL length, PL length and FECW, measured on both MRI and radiograph. Fresh ligaments were harvested (18 ACLs and 10 PLs) to evaluate the histological composition of the ACL and PL. Results: The morphology of the ACL and PL was determined. The morphology of the ligaments compared well to the descriptions in previous literature. The ligaments proved to be compatible at histological level. The results revealed that FECW was the most reliable predictor of ACL length. Linear regression formulas were developed in order to determine ACL length by measuring maximum FECW. It was also determined that either an MRI or radiograph can be used to assist in pre-operative planning. Conclusion: ACL and PL morphology compared well with the descriptions found in previous studies. It was also found that, contrary to previous studies, the maximum FECW is a more reliable predictor of ACL length than the height of the patient. The results also showed that both radiographs and MRI scans can be used to determine preoperative ACL length. These results could improve the pre-operative planning of ACL reconstruction and minimise the occurrence of graft mismatch.