Clinical Comparison of Femoral Nerve Versus Adductor Canal Block Following Anterior Ligament Reconstruction

Adequate pain control following anterior cruciate ligament reconstruction (ACL) often requires a regional nerve block. The femoral nerve block (FNB) has been traditionally employed. More recently, ultrasound application to regional nerve blocks allows for the use of alternatives such as the adductor canal block following ACL reconstruction. In 2009, Manickam et al. were the first to describe the ultrasound guided adductor canal technique for the purposes of knee joint analgesia. Unlike other traditional techniques that seek to cause a sensory as well as a motor blockade, the adductor canal block attempts to spare the motor block of the neighboring distributions in an attempt to offer selective analgesia and strength preservation. Chisholm et al demonstrated the adductor canal block provides similar and adequate postoperative analgesia when compared to the FNB, following arthroscopic ACL reconstruction with patellar tendon autograft. Their study focused on analgesia and did not evaluate quadriceps function or impact on rehabilitation. Sharma et al drew the first association between femoral nerve blocks and increased fall risk due to muscle weakness in total knee arthroplasty population. A randomized, blinded study to compare quadriceps strength following adductor canal versus FNB was performed by Kwofie et al. They showed that compared with FNB, adductor canal block results in significant quadriceps motor sparing and significantly preserved balance. These studies focused on acute muscle weakness after regional anesthesia and its relation to safety. Quadriceps function is very important in rehabilitation of ACL reconstruction. Luo et al demonstrated long term deficits related to FNB. They demonstrated that patients treated with FNB after ACL reconstruction had significant isokinetic deficits in knee extension and flexion strength at 6 months when compared with patients who did not receive a nerve block. Patients without a block were 4 times more likely to meet criteria for clearance to return to sports at 6 months. In addition, Krych et al found significantly inferior quadriceps strength and function at 6 months in FNB group. Based on the available literature, we aim to compare femoral nerve versus adductor canal block in regards to pain control and muscle strength in ACL reconstruction patients until return to sport.