Anesthesia of the anterior femoral cutaneous nerves for total knee arthroplasty incision: randomized volunteer trial

Abstract

Background and objectives For pain relief after total knee arthroplasty (TKA), an injection at the midthigh level may produce analgesia inferior to that of a femoral nerve block as the anterior femoral cutaneous nerves (intermediate femoral cutaneous nerve (IFCN) and medial femoral cutaneous nerve (MFCN)) are not anesthetized. The IFCN can be selectively anesthetized in the subcutaneous tissue above the sartorius muscle and the MFCN by an injection in the proximal part of the femoral triangle (FT). The primary aim was to investigate the area of cutaneous anesthesia in relation to the surgical incision for TKA and anteromedial knee area after intermediate femoral cutaneous nerve blockade (IFCNB) in combination with an injection in the proximal or distal part of the FT (proximal vs distal femoral triangle block (FTB)). Methods The study was carried out as two separate investigations: first, dissection of nine cadaver sides to verify a technique for IFCNB; second, a volunteer study with 40 healthy volunteers. The surgical midline incision for TKA was drawn bilaterally. All volunteers received an active distal FTB combined with a placebo proximal FTB on one side and vice versa on the other side. All volunteers were randomized to an active IFCNB on one side and placebo IFCNB on the contralateral side. Results Identification of IFCN was successful in all cadaver sides. Fifteen out of 20 volunteers had complete anesthesia of the incision line after IFCNB combined with proximal FTB, which was significantly higher compared with proximal FTB alone and with distal FTB+IFCNB. A gap at the anteromedial knee area was present in 2/20 volunteers with proximal FTB compared with 17/20 with distal FTB when all volunteers had active IFCNB. Conclusion Ultrasound-guided blockade of the IFCN and MFCN anesthetize the surgical midline incision and the anteromedial area of the knee relevant for TKA. In contrast, an injection at the midthigh level produces insufficient cutaneous anesthesia not covering the areas of interest. Trial registration number EudraCT: 2018-004986-15.

The analgesic efficacy of anterior femoral cutaneous nerve block in combination with femoral triangle block in total knee arthroplasty: a randomized controlled trial

“…In the AFCNB + FTB group, the needle was carefully advanced periarterially toward the medial side of the SFA and beneath the medial border of the SM, in order to achieve spread to the MCNT branches ( Fig. 1D ) [ 12 ]. Subsequently, patients in both groups were placed in 90° flexion of the knee to perform the IPACK block under sterile conditions with a 20 ml local anesthetic mixture, as described in a previous study [ 21 ].…”

“…The needle was then redirected to pierce the fascia This article is protected by copyright of Korean Journal of Anesthesiology. All rights reserved lata [12], and another 10-mL of anesthetic mixture was slowly injected between the fascia lata and SM until the tip of the needle reached the medial border of the SM to block the branch of MCNT and ensure adequate spread to the ICNT. In the FTB group, 20 mL of normal saline was injected.…”

“…The operator relies on the position of the sartorius muscle (SM) and subsartorial or superficial femoral artery (SFA), which runs down from the apex of the femoral triangle along the adductor canal to the adductor hiatus in an ultrasound image; new terminologies were developed to define each injection point [8][9][10]. The needle-injection point at the position where the SFA lies inferior or medial to the SM in the ultrasound image (femoral triangle block [FTB] or proximal ACB) is the most common [10][11][12]. Analgesia following FTB or proximal ACB is superior to other approaches as the corresponding site is nearer to the apex of the femoral triangle, and can involve other branches of the femoral nerve such as the vastus medialis nerve and infrapatellar branch of the saphenous nerve, and may medial cutaneous nerve of thigh which comprise the majority of nerve supply to the anteromedial knee joint [11,13].…”

“…Further, additional analgesic effect due to the blockade of the lateral femoral cutaneous nerve is minimized, as it mainly innervates the skin in the anterolateral part of the thigh and knee [14]. The cutaneous parts of the anteromedial aspects of the distal part of the thigh and knee are innervated by the anterior division of the sensory branch of the femoral nerve, called the anterior femoral cutaneous nerve (AFCN), which consists of the intermediate and medial cutaneous nerves of the thigh (ICNT and MCNT) [12,15]. The FTB may not completely anesthetize these nerves.…”

Anatomical and Technical Considerations of "Dual Subsartorial Block" (DSB), A Novel Motor-sparing Regional Analgesia Technique for Total Knee Arthroplasty

“…1. The apex of the iliopectineal fossa [12,13] (a proximal subset of FT), where the lateral border of ALM and medial border of STM intersect [Point A in Figure 1].…”