Obturator Nerve Block Research Articles

Femoral versus Multiple Nerve Blocks for Analgesia after Total Knee Arthroplasty.

BackgroundThe PROSPECT (Procedure-Specific Postoperative Pain Management) Group recommended a single injection femoral nerve block in 2008 as a guideline for analgesia after total knee arthroplasty. Other authors have recommended the addition of sciatic and obturator nerve blocks. The lateral femoral cutaneous nerve is also involved in pain syndrome following total knee arthroplasty. We hypothesized that preoperative blocking of all four nerves would offer superior analgesia to femoral nerve block alone.MethodsThis is a prospective, randomized, controlled, and observer-blinded clinical study. A total of 107 patients were randomly assigned to one of three groups: a femoral nerve block group, a multiple nerve block group, and a control group. All patients were treated postoperatively using patient-controlled intravenous analgesia with morphine. Pain intensity at rest, during flexion and extension, and morphine consumption were compared between groups over three days.ResultsA total of 90 patients completed the study protocol. Patients who received multiple nerve blocks experienced superior analgesia and had reduced morphine consumption during the postoperative period compared to the other two groups. Pain intensity during flexion was significantly lower in the “blocks” groups versus the control group. Morphine consumption was significantly higher in the control group.ConclusionsPain relief after total knee arthroplasty immediately after surgery and on the first postoperative day was significantly superior in patients who received multiple blocks preoperatively, with morphine consumption significantly lower during this period. A preoperative femoral nerve block alone produced partial and insufficient analgesia immediately after surgery and on the first postoperative day. (Clinical trial registration number (NIH): NCT01303120)

Obturator nerve block in transurethral resection of bladder tumor: A comparative study by two techniques

Context:Sparing of obturator nerve is a common problem encountered during transurethral resection of bladder tumor (TURBT) under spinal anesthesia.Aims:To evaluate and compare obturator nerve block (ONB) by two different techniques during TURBT.Settings and Design:This is prospective observational study.Subjects and Methods:Forty adult male patients from the American Society of Anesthesiologists Class I–IV planned to undergo TURBT under spinal anesthesia were divided into two groups of twenty each. In one group, ONB was performed with nerve locator. In other group, transvesical nerve block was performed with a cystoscope. The primary endpoints of this study were the occurrence of adductor reflex, ability to resect the tumor, and number of surgical interruptions. A number of transfusions required and bladder perforation were the secondary endpoints.Results:There was statistically significant difference between the groups for resection without adductor jerk, resection with a minimal jerk, and unresectable with high-intensity adductor jerk. Bleeding was observed in both groups and one bladder perforation was encountered.Conclusions:We conclude that ONB, when administered along with spinal anesthesia for TURBT, is extremely safe and effective method of anesthesia to overcome adductor contraction. ONB with nerve locator appears to be more effective method compared to the transvesical nerve block.

Combined Sciatic, Femoral, and Obturator Nerve Blocks for Ankle Surgery in a Patient with Severe Pulmonary Hypertension—A Case Report

We report a patient with severe pulmonary arterial hypertension (PAH) undergoing tibio-talo-calcaneal fusion due to Charcot joint. Despite the advancement in the management of PAH, the risks of anesthesia, surgery, and postoperative morbidity and mortality still remain high. A 46-year-old female was presented with severe PAH and end stage renal disease requiring hemodialysis three times a week. Ultrasound-guided sciatic, femoral, and obturator nerve blocks were performed with 0.5% levobupivacaine 15 ml, 10 ml, and 5 ml, respectively. All the blocks were successful, and the patient underwent uneventful anesthesia and surgery. In addition, the postoperative pain control lasted for 15 h and the patient was discharged on POD 5 without any complications. Therefore, ultrasound-guided sciatic, femoral, and obturator nerve blocks are valuable alternative to the general or neuraxial anesthesia in patients with severe pulmonary hypertension.

Ultrasound-Guided Obturator Nerve Block: A Focused Review on Anatomy and Updated Techniques.

This review outlines the anatomy of the obturator nerve and the indications for obturator nerve block (ONB). Ultrasound-guided ONB techniques and unresolved issues regarding these procedures are also discussed. An ONB is performed to prevent thigh adductor jerk during transurethral resection of bladder tumor, provide analgesia for knee surgery, treat hip pain, and improve persistent hip adductor spasticity. Various ultrasound-guided ONB techniques can be used and can be classified according to whether the approach is distal or proximal. In the distal approach, a transducer is placed at the inguinal crease; the anterior and posterior branches of the nerve are then blocked by two injections of local anesthetic directed toward the interfascial planes where each branch lies. The proximal approach comprises a single injection of local anesthetic into the interfascial plane between the pectineus and obturator externus muscles. Several proximal approaches involving different patient and transducer positions are reported. The proximal approach may be superior for reducing the dose of local anesthetic and providing successful blockade of the obturator nerve, including the hip articular branch, when compared with the distal approach. This hypothesis and any differences between the proximal ONB techniques need to be explored in future studies.

Obturator Nerve Block in Transurethral Resection of Bladder Tumor: A Comparison of Ultrasound-guided Technique versus Ultrasound with Nerve Stimulation Technique.

Background:Obturator nerve (ON) stimulation during transurethral resection of lateral and posterolateral bladder wall tumor under spinal anesthesia may lead to obturator reflex, adductor contraction, and leg jerking with complications such as bleeding, bladder perforation, or incomplete tumor resection. Our study was carried out to obtain successful block of ON using ultrasound (US)-guided technique with or without nerve stimulation in patients undergoing transurethral resection of bladder tumor (TURBT) under spinal anesthesia.Aims:The aim of the study was to compare the effectiveness of two different techniques in blocking ON and adductor spasm during TURBT.Settings and Design:Prospective, randomized, double-blind study.Subjects and Methods:Sixty patients with American Society of Anesthesiologists Status II and III scheduled to undergo TURBT for lateral and posterolateral bladder wall tumor were enrolled. Group I (US group, n = 30) patients received 5 ml of bupivacaine 0.5% each at anterior, and posterior division of ON under real-time US visualization and Group II (US-NS group, n = 30) received the same amount of bupivacaine 0.5% for each division using US-guidance with nerve stimulation-assisted technique. Motor block onset time, block success and performance time, ease of performance of block, and complications were measured besides assessing patient and surgeon satisfaction into two groups.Statistical Methods Used:SPSS using two sample independent t-test and Pearson's Chi-square/Fisher's exact test.Results:Motor block onset was significantly faster in Group II (6.67 ± 2.40) than in Group I (12.39 ± 2.55). A success rate of 90% was achieved in Group II as compared to 76.7% in Group I with increased block performance time in Group II (4.47 ± 0.73 min) versus (2.10 ± 0.51 min) in Group I. A better patient and surgeon satisfaction were seen in Group II with combination of US and nerve stimulation technique. No complications were encountered.Conclusion:We conclude that both techniques are safe and easy to perform; however, nerve stimulation as an adjunct to US results in a faster onset of block with a higher success rate.

The Spread of Ultrasound-Guided Injectate From the Adductor Canal to the Genicular Branch of the Posterior Obturator Nerve and the Popliteal Plexus: A Cadaveric Study.

The popliteal nerve plexus contributes to afferent knee-pain conduction. It is mainly formed by genicular branches from the posterior obturator and the tibial nerves, innervating the intra-articular and posterior knee region. A subinguinal obturator nerve block alleviates pain after total knee arthroplasty. Reduced hip adductor motor function could be avoided by a posterior obturator nerve block inside the popliteal fossa.The aim of this study was to evaluate the spread of dye after a distal adductor canal (AC) injection to the popliteal fossa and coloring of the popliteal plexus and the genicular branch of the posterior obturator nerve by dissection. We also assessed the spread of dye into the popliteal fossa after a distal femoral triangle injection. Ten milliliters of dye was injected into the distal part of the AC in 10 cadaver sides and into the distal part of the femoral triangle in 3 sides. Dissection was used to assess the spread of the injectate and coloring of the popliteal plexus and the genicular branch of the posterior obturator nerve, as well as the saphenous and medial vastus nerves. The popliteal plexus and the genicular branch of the posterior obturator nerve were dyed in all 10 dissections after AC injections. No dye spread into the popliteal fossa after femoral triangle injections. Injection of 10 mL of dye into the distal part of the AC spreads into the popliteal fossa and colors the popliteal plexus and the genicular branch of the posterior obturator nerve.

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

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. 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. 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. 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 obturator nerve block during transurethral resection of lateral bladder wall tumors on the presence of detrusor muscle in tumor specimens and recurrence of the disease

We investigated the effect of spinal anesthesia combined with obturator nerve block (ONB) during the transurethral resection of lateral bladder wall tumors (TUR-BT) on the presence of detrusor muscle tissue in tumor specimens and on tumor recurrence. TUR-BT was performed on 96 patients with a lateral bladder wall tumor under spinal anesthesia in our clinic between January 2011 and December 2015. The patients were divided into two groups: 49 patients only received spinal anesthesia and 47 patients received spinal anesthesia combined with ONB. The groups were retrospectively compared in terms of adductor muscle contraction, bladder perforation, complete tumor resection, presence of muscle tissue in the pathology material, and recurrence rate during follow-up. The obturator reflex was significantly observed in the non-ONB group (p < 0.05). In the ONB group, the percentages of complete resection and detrusor muscle tissue were significantly higher (p = 0.003 and p = 0.001, respectively). The postoperative recurrence rate was found to be significantly higher in the non-ONB group than in the ONB group (p = 0.025). Spinal anesthesia combined with ONB during TUR-BT prevent obturator reflex and facilitate complete resection including detrusor muscle tissue, independent from the size or number of tumors, thus reducing the recurrence of the disease.

Dexmedetomidine Added to Local Anesthetic Mixture of Lidocaine and Ropivacaine Enhances Onset and Prolongs Duration of a Popliteal Approach to Sciatic Nerve Blockade

PurposeA literature review of multiple clinical studies on mixing additives to improve pharmacologic limitation of local anesthetics during peripheral nerve blockade revealed inconsistency in success rates and various adverse effects. Animal research on dexmedetomidine as an adjuvant on the other hand has promising results, with evidence of minimum unwanted results. This randomized, double-blinded, contrastable observational study examined the efficacy of adding dexmedetomidine to a mixture of lidocaine plus ropivacaine during popliteal sciatic nerve blockade (PSNB). MethodsSixty patients undergoing varicose saphenous vein resection using ultrasonography-guided PSNB along with femoral and obturator nerve blocks as surgical anesthesia were enrolled. All received standardized femoral and obturator nerve blocks, and the PSNB group was randomized to receive either 0.5 mL (50 µg) of dexmedetomidine (DL group) or 0.5 mL of saline (SL group) together with 2% lidocaine (9.5 mL) plus 0.75% ropovacaine (10 mL). Sensory onset and duration of lateral sural cutaneous nerve, sural nerve, superficial peroneal nerve, deep peroneal nerve, lateral plantar nerve, and medial plantar nerve were recorded. Motor onset and duration of tibial nerve and common peroneal nerve were also examined. FindingsSensory onset of sural nerve, superficial peroneal nerve, lateral plantar nerve, and medial plantar nerve was significantly quicker in the DL group than in the SL group (P < 0.05). Sensory onset of lateral sural cutaneous nerve and deep peroneal nerve was not statistically different between the groups (P > 0.05). Motor onset of tibial nerve and common peroneal nerve was faster in the DL group than in in the SL group (P < 0.05). Duration of both sensory and motor blockade was significantly longer in the DL group than in the SL group (P < 0.05). ImplicationsPerineural dexmedetomidine added to lidocaine and ropivacaine enhanced efficacy of popliteal approach to sciatic nerve blockade with faster onset and longer duration.

Poster 448 Obturator Neuropathy after Lumbar Fusion and Resolution with Ultrasound-Guided Obturator Nerve Block: A Case Report

Poster 448 Obturator Neuropathy after Lumbar Fusion and Resolution with Ultrasound-Guided Obturator Nerve Block: A Case Report

RETRACTED: Detection of large perforating artery by ultrasound prescan before obturator nerve block

An obturator nerve block improves the quality of postoperative analgesia after lower extremity surgery [1]. An ultrasound-guided obturator nerve block is simpler to perform and more reliable than other landmark techniques [2]. We report a case where a large perforating artery was detected by ultrasound prescan before applying the obturator nerve block. A 75-year-old man with bladder cancer was scheduled to undergo transurethral resection of the bladder tumor. After induction of the spinal anesthesia, bilateral obturator nerve blocks were attempted by performing the interfascial approach at the level of the femoral crease. An ultrasound prescan indicated the presence of a large artery near the anterior branch of the right obturator nerve between the adductor longus and the adductor brevis (Figure). By using the ultrasound probe, we detected that it branched out from the right deep artery of the thigh. Therefore, the artery was considered a large perforating artery from the right deep artery of thigh. We could not detect a similar abnormal large performing artery from the left deep artery. We performed bilateral obturator nerve block to avoid the large performing artery from the right deep artery. An unintentional pucture of a large perforating artery puncture during obturator nerve block can cause some complications such as hematoma and local anesthetic intoxication. We recommend that the vasculature be confirmed by an ultrasound prescan prior to performing an obturator nerve block.

Application of nerve stimulator for obturator nerve block in transurethral resection of bladder tumor

Clinical data of 120 patients undergoing transurethral resection of the bladder sidewall tumors (TURBt) were retrospectively analyzed. Before TURBt the obturator nerve was blocked under the guide of the nerve stimulator in 46 cases (block group)and not blocked in 74 cases (unblock group). The incidence of obturator nerve reflex and bladder perforation in block group was significantly lower than that in unblock group(7% vs. 35%, P=0.000 and 0 vs. 19%, P=0.002, respectively). The operation time and the duration of bladder continuous saline irrigation after operation in block group were shorter than those in unblocked group [(32.2±12.5) vs. (43.2±24.5) min, P=0.001 and (8.9±6.4) vs. (13.3±10.8) h, P=0.013, respectively]. The efficiency value of TURBt in block group was better than that in unblock group [(5.8 ±3.9) vs. (9.3 ± 7.0) min/cm2,P=0.001]. The obturator nerve block guided by the nerve stimulator can improve the safety and the efficiency of TURBt. Key words: Urinary bladder neoplasms; Obturator nerve

Arthroscopic medial meniscus trimming or repair under nerve blocks: Which nerves should be blocked?

Background:This study aimed to determine the role of the sciatic and obturator nerve blocks (in addition to femoral block) in providing painless arthroscopic medial meniscus trimming/repair.Materials and Methods:One hundred and twenty patients with medial meniscus tear, who had been scheduled to knee arthroscopy, were planned to be included in this controlled prospective double-blind study. The patients were randomly allocated into three equal groups; FSO, FS, and FO. The femoral, sciatic, and obturator nerves were blocked in FSO groups. The femoral and sciatic nerves were blocked in FS group, while the femoral and obturator nerves were blocked in FO group. Intraoperative pain and its causative surgical maneuver were recorded.Results:All the patients (n = 7, 100%) in FO group had intraoperative pain. The research was terminated in this group but completed in FS and FSO groups (40 patients each). During valgus positioning of the knee for surgical management of the medial meniscus tear, the patients in FS group experienced pain more frequently than those in FSO group (P = 0.005).Conclusion:Adding a sciatic nerve block to the femoral nerve block is important for painless knee arthroscopy. Further adding of an obturator nerve block may be needed when a valgus knee position is required to manage the medial meniscus tear.

Comparative study between general anesthesia and sciatic–femoral–obturator blockade as regards analgesia and incidence of postoperative cognitive dysfunction in elderly patients undergoing unilateral total knee replacement

Objectives The aim of this study was to compare the effect of sevoflurane general anesthesia (GA) and sciatic–femoral–obturator blockade as regards analgesia and incidence of postoperative cognitive dysfunction (POCD) in elderly patients undergoing unilateral total knee replacement. Patients and methods The patients were divided in a randomized manner into two groups: the GA group ( n =40) received maintenance of anesthesia with inhalational sevoflurane, and the peripheral nerve block (PNB) group ( n =40) underwent sciatic nerve block (40 ml), femoral nerve block (20 ml), and obturator nerve block (10 ml) with 0.25% bupivacaine. The following time points were considered: baseline, immediately before induction of anesthesia (T-baseline), immediately after induction of anesthesia (T-induction), at the end of the operation (T-end) and then at 6, 12, 18, and 24 h postoperatively and were represented as T6, T12, T18, and T24, respectively. Results A total of 15 of 40 patients from the GA group developed POCD, whereas six of 38 patients in the PNB group developed POCD at T24. This difference was significant. Moreover, there was a significant decrease in Mini-Mental State Examination score in the GA group after 24 h in comparison with the preoperative value. There was a significantly higher value of Aβ (β-amyloid protein) in the GA group compared with the PNB group 24 h postoperatively. Visual analogue score was significantly lower at T-end, T6, T12, T18, and T24 in the PNB group compared with the GA group. Hemodynamics was significantly lower in the PNB group than in the GA group at T-end, T6, T12, T18, and T24. They were significantly higher in the PNB group than in the GA group at T-induction. Total opioid consumption within 24 h postoperatively and the incidence of nausea were lower in the PNB group compared with the GA group. Induction time was significantly longer in the PNB group than in the GA group. Conclusion The current study demonstrated that PNB with sciatic–femoral–obturator for total knee replacement was accompanied by less POCD, less pain, less nausea, and less opioid consumption within 24 h postoperatively compared with GA with sevoflurane.

Ultrasound Guided Phenol Block of the Obturator Nerve for Severe Adductor Spasticity: A Pilot Study

Objective: To assess the efficacy of phenol block of the obturator nerve in treating severe adductor spasticity. Design: A prospective pilot study. Setting: Outpatient rehabilitation clinics. Participants: We recruited 5 participants with severe adductor spasticity. Four were persons with multiple sclerosis and one was a person with adult cerebral palsy. All participants were women and had an average age of 60.4 years; four participants had bilateral severe adductor spasticity and one had unilateral severe adductor spasticity. Interventions: A total of 9 phenol blocks of the obturator nerve were performed. Five were performed with ultrasound guidance, followed by localization of the obturator nerve by peripheral nerve stimulator. Four were performed using anatomic landmark and peripheral nerve stimulator for localization. Outcome Measures: The primary outcome measure was the Modified Ashworth Scale score of the hip adductor at 1 month after the obturator nerve block. The secondary outcomes measures include Modified Ashworth Scale (MAS) score of the hip adductors at 6 months, distance between the right and left medial femur condyles in supine with hip extended to neutral, Disability Assessment Scale (DAS) score, Goal Attainment Scale (GAS) score, Spasticity Numeric Rating Scale score and Subjects’ and Physician Global Impression of Changes scores. Results: There was statistically significant decrease in the MAS score at 1-month compared to baseline (2.43 vs. 4; P=0.001). There was no statistically significant difference in the secondary outcomes. There were no reported adverse effects of procedure. Conclusion: This study suggests that phenol block of the obturator nerve is effective in treating severe adductor spasticity. We recommend a larger study with more participants and longer follow up period to allow further assessment of the efficacy of the phenol block of the obturator nerve in treating severe adductor spasticity.

A new ultrasound-guided pubic approach for proximal obturator nerve block: clinical study and cadaver evaluation.

We evaluated an alternative technique for ultrasound-guided proximal level obturator nerve block that might facilitate needle visualisation using in-plane ultrasound guidance. Twenty patients undergoing transurethral bladder tumour resection requiring an obturator nerve block were enrolled into a prospective observational study. With the patient in the lithotomy position, the transducer was placed on the medial thigh along the extended line of the inguinal crease, and aimed cephalad to view a thick fascia between the pectineus and obturator externus muscles that contains the obturator nerve. A stimulating nerve block needle was inserted at the pubic region and advanced in-plane with the transducer in an anterior-to-posterior direction. Eight ml levobupivacaine 0.75% was injected within the fascia. The median (IQR [range]) duration for ultrasound identification of the target and injection were 8.5 (7-12 [5-24]) s and 62 (44.5-78.25 [39-383]) s, respectively. All blocks were successful. A cadaver evaluation demonstrated that the dye injected into the target fascia using our technique travelled retrogradely through the obturator canal, and surrounded the anterior and posterior branches of the obturator nerve both proximally and distally to the obturator canal. We believe that this is a promising new technique for ultrasound-guided proximal level obturator nerve block.

Adductor accessorius - an unusual supernumerary adductor muscle of thigh.

The knowledge of variant anatomy of medial compartment of thigh is extremely important in surgical procedures requiring obturator nerve block. The nerve block is also recommended for providing additional analgesia following major knee surgeries and for relieving painful adductor muscle spasm. The interfascial injection technique is commonly followed in ultrasound guided obturator nerve block. For this procedure it is imperative to identify the adductor muscles on sonography to inject the anesthetic solution in the intermuscular fascial planes. The presence of an additional muscle can prove useful in myocutaneous flap surgeries for reconstruction especially of perineum. We hereby report a case of such an anomalous supernumerary adductor muscle present between adductor brevis and proximal part of adductor magnus, in an adult Indian male cadaver, recorded during routine dissection in Department of Anatomy, Vardhman Mahavir Medical College and Safdarjung Hospital. The muscle was innervated by the posterior division of obturator nerve. The morphology, embryological basis and clinical aspects are also discussed.

Impact of nerve stimulator-guided obturator nerve block on the short-term outcomes and complications of transurethral resection of bladder tumour: A prospective randomized controlled study.

In this prospective randomized controlled study, we investigated the efficacy of obturator nerve block (ONB) on adductor muscle spasm and related short-term outcomes and complications in patients who underwent transurethral resection of lateral wall-located bladder tumours (TURBT). Between July 2014 and February 2015, 70 patients scheduled to undergo TUR of lateral bladder wall tumours were enrolled in the study. All patients were preoperatively evaluated by cystoscopy and imaging tools and selected according to localized tumours on the lateral bladder wall. Patients were randomly allocated to Group SA (35 patients who underwent only spinal anesthesia) and Group ONB (35 patients who underwent spinal anesthesia combined with ONB by the nerve stimulator). An independent observer, blinded to the approach, evaluated the obturator signs, including adductor muscle contraction, bladder perforation, and completeness of the resection during the TURBT procedure. The differences between groups regarding mean operation time, tumour size, and number were not statistically significant (p > 0.05). Adductor muscle contraction was detected in 40% of patients in Group SA and 11.4% in Group ONB. This difference was statistically significant (p = 0.021). Complete bladder perforation was detected in 2 patients in Group SA, whereas no perforation was observed in Group ONB. There was no case of severe bleeding in both groups. We found that ONB performed after spinal anesthesia was effective in preventing intraoperative complications due to adductor muscle spasm while performing TURBT. Our study limitations include its small sample size, since we only enrolled patients with primary lateral wall-localized bladder tumour. Also, we excluded patients who underwent bipolar TURBT.

Accuracy of Injection Site for Obturator Nerve Block in Cadavers: Blind Injection vs. Ultrasound-guided Injection

To compare the accuracy rates of blind injection with ultrasound-guided injection during obturator nerve block in cadavers.

Efficacy of ultrasound-guided obturator nerve block using proximal interfascial technique

Objective To evaluate the efficacy of ultrasound-guided obturator nerve block using proximal interfascial technique. Methods Seventy ASA physical status Ⅰ or Ⅱ patients of both sexes, aged 43-82 yr, with body mass index of 18.0-30.5 kg/m2, scheduled for elective trans-urethral resection of bladder tumor, were randomly divided into 2 groups(n=35 each)using a random number table: remote interfascial technique group(group R)and proximal interfascial technique group(group P). In group R, interfascial injections at 2 planes, lateral and deep to the adductor brevis muscle, were carried out with 0.375% ropivacaine 7.5 ml to block each obturator nerve branch separately.In group P, 0.375% ropivacaine 15.0 ml was injected under ultrasound guidance at the interfascial plane inferior to the superior pubic ramus(between the pectineus and obturator externus). The strength of thigh adduction was measured before injection(baseline)and at 5, 10, and 15 min after injection.Then combined spinal-epidural anesthesia was performed at L3, 4 interspace.The 50% strength reduction indicated a successful block.The block performance time was recorded.The success rate of block at 15 min after injection was calculated.It was considered clinically effective when obvious muscle twitching interfering with the surgical procedure did not appear.The clinical outcome was assessed, and the effective rate of clinical outcome was calculated. Results Compared with group R, the block performance time was significantly shortened, the success rate of block, strength reduction at 10 and 15 min after injection, and clinical outcome were increased in group P. There were no significant differences in the effective rate of clinical outcome. Conclusion Compared with remote interfascial technique, ultrasound-guided obturator nerve block using proximal interfascial technique provides easier and rapid procedure, higher success rate of block and better clinical outcome of block. Key words: Nerve block; Obturator nerve; Ultrasonography