Radiological analysis on femoral tunnel positioning between isometric and anatomical reconstructions of the anterior cruciate ligament☆☆☆

OBJECTIVE the aim of this study was to radiologically evaluate the femoral tunnel position in anterior cruciate ligament (ACL) reconstructions using the isometric and anatomical techniques. METHODS a prospective analytical study was conducted on patients undergoing ACL reconstruction by means of the isometric and anatomical techniques, using grafts from the knee flexor tendons or patellar tendon. Twenty-eight patients were recruited during the immediate postoperative period, at the knee surgery outpatient clinic of FCMMG-HUSJ. Radiographs of the operated knee were produced in anteroposterior (AP) view with the patient standing on both feet and in lateral view with 30° of flexion. The lines were traced out and the distances and angles were measured on the lateral radiograph to evaluate the sagittal plane. The distance from the center of the screw to the posterior cortical bone of the lateral condyle was measured and divided by the Blumensaat line. In relation to the height of the screw, the distance from the center of the screw to the joint surface of the lateral condyle of the knee was measured. On the AP radiograph, evaluating the coronal plane, the angle between the anatomical axis of the femur and a line traced at the center of the screw was measured. RESULTS with regard to the p measurement (posteriorization of the interference screw), the tests showed that the p-value (0.4213) was greater than the significance level used (0.05); the null hypothesis was not rejected and it could be stated that there was no statistically significant difference between the anatomical and isometric techniques. With regard to the H measurement (height of the screw in relation to the lower cortical bone of the knee), the p-value observed (0.0006) was less than the significance level used (0.05); the null hypothesis was rejected and it could be stated that there was a statistically significant difference between the anatomical and isometric techniques. It can be concluded that the latter difference occurred because the isometric technique generated greater values for the H measurement than the anatomical technique. With regard to the MED variable (position of the screw on the AP radiograph), the observed p-value (0.000) was less than the significance level (5%); the null hypothesis was rejected and it could be stated with 95% confidence that there was a significant difference between the anatomical and isometric techniques. CONCLUSIONS there were statistically significant differences in the radiological evaluations of the femoral tunnel, both in the sagittal and in the coronal plane, between the ACL reconstruction techniques.