The femoral nerve block is a regional anesthetic technique used in conjunction with general anesthesia for ACL reconstruction surgery, tibial osteotomies and other more painful complex surgeries involving the knee joint. It is a safe and effective block that provides excellent post-operative pain control for the inside and front of the knee.
During a preoperative phone interview the procedure as well as its risks and benefits will be discussed with you in detail. On arrival to the ASC prep area you will be asked to sign a consent for the procedure.. You will then be attached to the usual monitors: a blood pressure cuff, a light sensor to measure your blood oxygen level will be attached to your finger, and EKG leads will be placed on your chest. You will receive some sedation through your intravenous prior to placement of the block, which both relaxes you and will likely cause you to have little or no recollection of the block placement.
Next, while maintaining modesty, the anesthesiologist will cleanse your groin region on the operative side with an antiseptic solution. He or she will use both anatomical landmarks and an ultrasound machine to find the desired location for the femoral nerve block in the groin region.
Once the best location is found, the anesthesiologist will numb the skin with some local anesthetic. Next he or she will slowly insert a needle the size of a paperclip through the skin. Your anesthesiologist will utilize ultrasound to guide the needle to the proper location near the nerve. In addition to the ultrasound, occasionally, a process called nerve stimulation, will be used to assist verifying the location of the nerve to your thigh and knee. If nerve stimulation is used, a very small amount of electrical current will be put through the needle and you will feel the sensation of involuntary twitches or movements in your upper leg and kneecap. Don't try to stop these movements because they tell us if we are in the right location with the needle. When the location and/or response is optimal the anesthesiologist will inject the long acting Novocain like medicine in multiple small doses which will numb the front of your thigh and knee. This procedure takes only a few minutes to perform.
The block takes approximately 15-20 minutes to work. You will notice upper leg weakness and numbness over your thigh area. Once in the operating room, you will once again be attached to the usual monitors and positioned by the surgeon. You will receive a light general anesthetic in addition to the femoral nerve block as your anesthetic because the femoral nerve block doesn't numb up the back of the knee.
After the surgery and transport to the recovery room, the general anesthesia will begin to wear off. You will have little or no pain in the front of your leg or knee. However you will probably have some discomfort behind your knee. That is expected. You will receive pain medicine in the recovery room, as you need it.
The numbness and weakness from the block usually lasts from 10-24hrs and occasionally greater than 24 hours. As it begins to wear off you should start your pain medicine that was prescribed by the surgeon.