Adductor canal nerve blocks are traditionally used for pain management for procedures of the medial ankle.
These regional anaesthesia blocks numb the saphenous nerve. Doctors noticed that adductor canal block was usually accompanied by numbness of the knee, so this sparked an interest in using this particular block for knee surgery.
Prior to the millenium, it was common in USA orthopaedic clinics to keep knee patients (eg cruciate ligament, knee replacement) in hospital for three days for rehab, continuing their pain relief from the operating room via anaesthetic agent delivered via an indwelling epidural cathether. This reduced the amount of pain medication taken by mouth, keeping patients more alert and co-operative and reducing nausea and other side effects of pain medication.
Pressure from hospital management around the time of the millennium to send patients home early from knee surgery rather than retaining them in hospital for rehabilitation during this time triggered a change in practice to the insertion of a femoral nerve catheter, with discharge after only one day. This allowed full use of the good leg but had the disadvantage of blocking or reducing strength of the quadriceps muscle of the operated leg, a muscle which is essential for proper rehab as it is responsible for straightening the leg, and giving the patient confidence to stand up and to walk. The quadriceps muscle has a peculiar response to pain and seems to shut itself down, initially becoming inhibited (quads inhibition) but later actually decreasing in bulk (quads atrophy), and failure to use the quads in normal movement after surgery can lead to adhesions in the knee which can further hamper rehabilitation.
A couple of years ago, interest turned to using a resident adductor canal catheter instead of a femoral nerve catheter because it does not have this dulling effect on the quadriceps muscle, but it still helps greatly with reducing knee pain. The patient can control the pain via a pump that delivers a fixed amount of long-acting anaesthetic agent per hour to the area. The catheters are very easy to remove once they are no longer needed.
The researchers looked at quadriceps muscle strength and post-surgery pain. The indices used to measure pain were essentially similar with the two blocks.
- http://www.ncbi.nlm.nih.gov/pubmed/24121608 Reg Anesth Pain Med. 2013 Nov-Dec;38(6):526-32. doi: 10.1097/AAP.0000000000000015. Adductor canal block versus femoral nerve block for analgesia after total knee arthroplasty: a randomized, double-blind study. Jæger P1, Zaric D, Fomsgaard JS, Hilsted KL, Bjerregaard J, Gyrn J, Mathiesen O, Larsen TK, Dahl JB.
- http://www.ncbi.nlm.nih.gov/pubmed/25376972 Reg Anesth Pain Med. 2015 Jan-Feb;40(1):3-10. doi: 10.1097/AAP.0000000000000169. Effect of adductor canal block versus femoral nerve block on quadriceps strength, mobilization, and pain after total knee arthroplasty: a randomized, blinded study. Grevstad U1, Mathiesen O, Valentiner LS, Jaeger P, Hilsted KL, Dahl JB.
- Acknowledgement to VuMedi for the video of Adductor Canal Blocks for Major Knee Surgery By Halyard Health Featuring David Harwood, James R Andrews, Bindu Bamrah et al.