The anterior branch of the medial femoral cutaneous nerve innervates the anterior knee: a randomized volunteer trial.

BACKGROUND: The midline skin incision for total knee arthroplasty may be an important generator of chronic neuropathic pain. The incision is innervated by the medial femoral cutaneous nerve (MFCN), the intermediate femoral cutaneous nerves (IFCN) and the infrapatellar branch from the saphenous nerve. The MFCN divides into an anterior (MFCN-A) and a posterior branch (MFCN-P). The primary aim was to compare the areas anesthesized by MFCN-A versus MFCN-P block for coverage of the incision. METHODS: Nineteen healthy volunteers had IFCN and saphenous nerve blocks. The subgroup of volunteers with a non-anesthetized gap between the areas anesthetized by the saphenous and the IFCN blocks was defined as the study group for the primary outcome. Subsequently selective MFCN-A block and MFCN block (MFCN-A + MFCN-P) were performed to investigate the contributions from MFCN-A and MFCN-P to the innervation of the midline incision. All assessments were performed blinded. RESULTS: Ten out of 19 volunteers had a non-anesthetized gap. Nine out of these 10 volunteers had coverage of the non-anesthetized gap after selective anesthesia of the MFCN-A, whereas anesthesia of the MFCN-P did not contribute to coverage of the gap in any of the 10 volunteers. CONCLUSIONS: In half of the cases, a gap of non-anesthetized skin was present on the surgical midline incision after anesthesia of the saphenous nerve and the IFCN. This gap was covered by selective anesthesia of the MFCN-A without contribution from MFCN-P. The selective MFCN-A block may be relevant for diagnosis and interventional management of neuropathic pain due to injury of MFCN-A.

Cutaneous anaesthesia of hip surgery incisions with iliohypogastric and subcostal nerve blockade: A randomised trial.

BACKGROUND: Cutaneous nerve blockade may improve analgesia after hip surgery. Anaesthesia after the lateral femoral cutaneous (LFC) nerve block is too distal for complete coverage of most hip surgery incisions, which requires additional anaesthesia of the adjacent, proximal area. The transversalis fascia plane (TFP) block potentially anaesthetises the iliohypogastric and subcostal nerves. The primary aim of the present study was to investigate, if the TFP block provides cutaneous anaesthesia adjacent to the LFC nerve block. METHODS: Active vs placebo TFP blocks were compared in a paired randomised controlled trial (RCT) in 20 volunteers, who all had bilateral LFC nerve blocks. The day preceding the RCT, the area anaesthetised by a novel selective ultrasound guided subcostal nerve block was identified bilaterally in order to assess the contribution of the subcostal nerve to the area anaesthesia by the TFP block. RESULTS: Anaesthesia of the lateral hip region after TFP block was 80%. The cutaneous anaesthesia after active TFP block was in continuity with the LFC nerve block in 65%. Combined TFP and LFC nerve blockade significantly increased the coverage of hip surgery incisions compared to LFC nerve block alone. The success rate of blocking the subcostal nerve was 50% with the TFP block. CONCLUSION: The TFP block anaesthetises the skin proximal to the LFC nerve block by anaesthetising the iliohypogastric and subcostal nerves. TFP block as a supplement to LFC nerve block improves the coverage of the proximal surgical incisions used for hip surgery.

The Lateral Femoral Cutaneous Nerve: Description of the Sensory Territory and a Novel Ultrasound-Guided Nerve Block Technique.

BACKGROUND AND OBJECTIVES: Nerve blockade of the lateral femoral cutaneous (LFC) nerve provides some analgesia after hip surgery. However, knowledge is lacking about the extent of the cutaneous area anesthetized by established LFC nerve block techniques, as well as the success rate of anesthetic coverage of various surgical incisions. Nerve block techniques that rely on ultrasonographic identification of the LFC nerve distal to the inguinal ligament can be technically challenging. Furthermore, the branching of the LFC nerve is variable, and it is unknown if proximal LFC nerve branches are anesthetized using the current techniques. The primary aim of this study was to investigate a novel ultrasound-guided LFC nerve block technique based on injection into the fat-filled flat tunnel (FFFT), which is a duplicature of the fascia lata between the sartorius and the tensor fasciae latae muscle, in order to assess the success rate of anesthetizing the proximal LFC nerve branches and covering of the different surgical incisions used for hip surgery. METHODS: First, a cadaveric study was conducted in order to identify an FFFT injection technique that would provide adequate injectate spread to the proximal LFC nerve branches. Second, a clinical study was conducted in a group of 20 healthy volunteers over 2 consecutive days. On trial day 1, successful complete anesthesia of the LFC nerve was defined by performing a suprainguinal fascia iliaca block bilaterally in each subject. On trial day 2, a triple-blind randomized controlled trial compared the effect of the novel ultrasound-guided LFC nerve block technique for bupivacaine versus placebo. The primary end point was the success rate of anesthesia of the proximal cutaneous area innervated by the LFC nerve for the FFFT injection with bupivacaine versus placebo. RESULTS: Adequate spread of injectate to the proximal LFC nerve branches in cadavers was obtained by injecting 10 mL with dynamic needle-tip tracking in the FFFT. Application of this technique in the randomized controlled trial provided anesthesia of the lateral thigh with a success rate of 95% (95% confidence interval, 73.9%-99.8%) for the active side and 0% for placebo (P < 0.001). The proximal branches were anesthetized with a success rate of 68% (95% confidence interval, 43.4%-87.4%) on the active side. The proximal extent of the anesthetized cutaneous area was on average 7.9 cm distal to the greater trochanter. CONCLUSIONS: This novel LFC nerve block technique is easy and quick and reliably produces anesthesia of the lateral thigh. The greater trochanter is rarely included in the area of anesthesia, which reduces the coverage of each specific surgical incision. The success rate of 68% in anesthetizing the proximal nerve branches must be further evaluated by future research.

A Cadaveric Study of Ultrasound-Guided Subpectineal Injectate Spread Around the Obturator Nerve and Its Hip Articular Branches.

BACKGROUND AND OBJECTIVES: The femoral and obturator nerves are assumed to account for the primary nociceptive innervation of the hip joint capsule. The fascia iliaca compartment block and the so-called 3-in-1-block have been used in patients with hip fracture based on a presumption that local anesthetic spreads to anesthetize both the femoral and the obturator nerves. Evidence demonstrates that this presumption is unfounded, and knowledge about the analgesic effect of obturator nerve blockade in hip fracture patients presurgically is thus nonexistent. The objectives of this cadaveric study were to investigate the proximal spread of the injectate resulting from the administration of an ultrasound-guided obturator nerve block and to evaluate the spread around the obturator nerve branches to the hip joint capsule. METHODS: Fifteen milliliters of methylene blue was injected into the interfascial plane between the pectineus and external obturator muscles in 7 adult cadavers. The spread of the injectate into the obturator canal and around the obturator and accessory obturator nerve branches to the hip joint was evaluated by subsequent dissection. RESULTS: The injected dye spread into the obturator canal and colored all obturator branches to the hip joint capsule in all 14 sides. Furthermore, the accessory obturator nerve was present in 3 sides (21%), and the nerve and its branches to the hip joint capsule were colored in all cases. CONCLUSIONS: In cadavers, injection of 15 mL of methylene blue into the interfascial plane between the pectineus and the external obturator muscle effectively spreads proximally to reach the obturator canal, as well as the obturator nerve branches to the hip joint capsule and the accessory obturator nerve.

Effect of hypertonic saline infusion on postoperative cellular immune function: a randomized controlled clinical trial.

BACKGROUND: Previous studies found hypertonicity to affect immune responses in intact laboratory animals and in human blood cell cultures. In this study, the authors investigated the cellular immune response to surgery after preoperative infusion of hypertonic saline in humans. METHODS: Sixty-two women scheduled to undergo abdominal hysterectomy were randomly assigned to single-blinded infusion of 4 ml/kg NaCl, 7.5%; 4 ml/kg NaCl, 0.9%; or 32 ml/kg NaCl, 0.9%, over 20 min. Blood was collected at baseline, during surgery, and 1, 24, and 48 h after surgery for the determination of leukocyte and differential counts, flow cytometric phenotyping of mononuclear cells, and natural killer cell activity against K 562 tumor cells. Phytohemagglutinin-induced lymphocyte proliferation, plasma elastase, and neutrophil chemotaxis were measured at the same time points except during surgery. The authors tested cell-mediated immune function in vivo by delayed-type hypersensitivity reaction in the skin. RESULTS: Surgery induced well-known changes in the cellular immune response, which were unrelated to the tonicity or volume of the infused fluids. CONCLUSION: Infusion of a clinically relevant dose of hypertonic saline did not seem to modify the postoperative cellular immune response after elective abdominal hysterectomy.