Paper 204: Potential risk of damage to the nerve and cartilage making a femoral tunnel through the far anteromedial portal in double-bundle anterior cruciate ligament reconstruction -Cadaveric knee evaluation

Abstract

Recently, double-bundle Anterior cruciate ligament (ACL) reconstruction has been developed through biomechanical and clinical studies. In double-bundle ACL reconstruction, making a femoral tunnel through the far anteromedial portal provides more flexibility for drilling the anatomical femoral attachments of the anteromedial bundle (AMB) and the posterolateral bundle (PLB) of ACL. However, if the direction of drilling for femoral tunnel construction is inappropriate, there are potential risks for damage to the common peroneal nerve and the articular cartilage of the lateral femoral condyle. The purpose of this study was to estimate the potential risks associated with making the femoral tunnel through the far anteromedial portal in double-bundle ACL reconstruction using cadaveric knees. In this study, 10 cadaveric knees (5 cadavers :2 males and 3 females), excluding malalignment of legs and severe osteoarthritis, were used. The average age of the subjects at the time of death, was 72.6 years. We opened the knee joint and identified the anatomical femoral attachments of AMB and PLB. The common peroneal nerve and the articular cartilage of the lateral femoral condyle were exposed on the lateral side of the knee. We drilled the passing pin to the center of the anatomical femoral attachments of AMB and PLB through the far anteromedial portal at three different knee flexion angles: 70°, 90°,110° of knee flexion. We identified the femoral passing point as the femoral tunnel making point, and measured the length of the femoral tunnel, the shortest distance to the common peroneal nerve and the articular cartilage of the lateral femoral condyle, to evaluate the potential risks of damage to the nerve and the cartilage. The lengths of the femoral tunnel were no more than 25 mm in one knee when drilling the AMB and in four when drilling the PMB at a knee flexion angle of 70°. The shortest distances at a flexion angle of 70° to the common peroneal nerve were no more than 10mm in seven AMB cases and in nine PLB cases, and at 90° in one AMB and five PLBs,. On the other hand, the distances were no less than 10mm in all the AMBs and PLBs at a knee flexion angle of 110°. In all AMB and PLB knees at 70°, the shortest distances to the articular cartilage were no more than 10 mm. In particular, the pin directly passed the articular cartilage in all PMBs. The distances were no more than 10mm in two AMBs and all PMBs at 90°,but in only two PLBs at 110°. In our measurements, the shortest distances from the femoral tunnel making point to the common peroneal nerve and the articular cartilage of the lateral femoral condyle were no more than 10mm in a high proportion of the subjects at shallow knee flexion angles. In this study, we proposed that making a femoral tunnel through the far anteromedial portal at shallow knee flexion angles in double-bundle ACL reconstructions may have the potential risk of damage to the nerve and the cartilage.