Adductor Canal Block Versus Femoral Canal Block for Total Knee Arthroplasty

Abstract

D ue to the invasiveness of total knee arthroplasty (TKA), the procedure is often associated with extreme postoperative pain. In fact, 23% of patients cite at home pain as "severe/ extreme" after surgery, whereas 54% of the patients indicate "severe pain at least some of the time." 1 Moreover, it has been suggested that postoperative pain can also interfere with the recovery process, 2 which can put patients at an increased risk for postoperative complications including infections, loosening of the joint, and reflex sympathetic dystrophy. 3 Different techniques can be used preoperatively to complement the effects of general anesthesia, including femoral nerve block (FNB) and adductor canal block (ACB)/saphenous nerve block.Femoral nerve block has traditionally been an efficient method to reduce postoperative pain after TKA. For instance, Chan et al 4 found that FNB decreased pain scores at 24 hours as compared with a sham procedure. Moreover, Jadon et al 5 observed that FNB is a more efficient method of analgesia as compared with IV fentanyl. However, FNB has been found to have postsurgical complications, including severe quadriceps muscle weakness. 6 Certainly, surgical causes such as tourniquet-related weakness or surgical quadriceps dysfunction must also be considered, but femoral nerve blockaderelated weakness can be explained by the anatomy of the nerve targeted in the FNB. The femoral nerve not only comprises sensory branches, but also contains motor branches that innervate muscles of the upper and lower leg. The motor nerve involvement of the FNB is what leads to muscle weakness, which can alter the ability of the patient to ambulate properly and can increase the risk of postoperative falls. As such, ACB is a method of analgesia that has recently sparked tremendous interest in the scientific community due to its potential benefits over FNB; however, this approach itself does not come without controversy.Adductor canal block is thought to be as effective as FNB in reducing postoperative pain. 7 In addition to having similar pain scores reported by patients, ACB has been thought to be associated with better quadriceps strength postoperatively in comparison to FNB. Theoretically, this is intuitive because the saphenous nerve, a component of the adductor canal and the nerve targeted in ACB, is a purely sensory branch of the femoral nerve. Due to the lack of motor impairment with ACB, quadriceps muscle function is preserved. This may ultimately lead to better ambulation after TKA.

Femoral Nerve Block versus Adductor Canal Block for Analgesia after Total Knee Arthroplasty

“…Four of the six meta-analyses showed greater quadriceps muscle strength in ACB recipients on POD 140,42–44), but one study found no between-group difference39). In addition, similar adductor muscle strength was reported in three studies39,43,44).…”

“…All studies included in final analyses in this review showed comparable analgesic efficacy in terms of pain level and opioid consumption between ACB and FNB21–32,39–44). In addition, most studies documented superior quadriceps strength and mobilization ability during the first 24 hours after TKA for ACB compared with FNB22,27,28,30–32,40–44). Moreover, ACB catheters required fewer provider interventions per patient, thus decreasing the workload compared with FNB catheters23).…”

Comprehensive Analysis of Pain Management after Total Knee Arthroplasty

“…A recent meta-analysis reported that ACB remains an attractive alternative to FNB for pain control and motor strength preservation after TKA, but the anatomical location of the adductor canal needs to be better defined to ensure consistency in the type of block performed. It was concluded that they cannot safely suggest that an ACB provides optimal outcomes in comparison to FNB until aforementioned factor is completely understood55). Therefore, it is too early to recommend ACB for pain management after TKA even though it has the potential to replace FNB as a gold standard of pain management after TKA56).…”

Continuous Block at the Proximal End of the Adductor Canal Provides Better Analgesia Compared to that at the Middle of the Canal After Total Knee Arthroplasty: A Randomized, Double-blind, Controlled Trial

“…The AC is a musculoaponeurotic tunnel that runs proximally from the apex of the femoral triangle (FT)/proximal end (entrance opening) of the AC where the medial borders of the sartorius muscle (SM) and adductor longors muscle (ALM) align, to the adductor hiatus distally where the femoral artery (FA) diverges from the SM and becomes deep. 9 The internal landmarks de ned above can be easily identi ed via ultrasound, which has recently been deemed to be a more accurate and reliable method to identify the exact location of the AC. [10][11][12] However, to the best of our knowledge, the ideal continuous ACB location (for analgesia after TKA) of the true AC identi ed with these sonographic landmarks has not been investigated in a clinical setting.…”