Molecular characterization of ESR1 variants in breast cancer.

PURPOSE: Estrogen receptor 1 (ESR1) mutations and fusions typically arise in patients with hormone receptor-positive breast cancer after aromatase inhibitor therapy, whereby ESR1 is constitutively activated in a ligand-independent manner. These variants can impact treatment response. Herein, we characterize ESR1 variants among molecularly profiled advanced breast cancers. METHODS: DNA next-generation sequencing (592-gene panel) data from 9860 breast cancer samples were retrospectively reviewed. Gene fusions were detected using the ArcherDx fusion assay or whole transcriptome sequencing (n = 344 and n = 4305, respectively). Statistical analyses included Chi-square and Fisher's exact tests. RESULTS: An ESR1 ligand-binding domain (LBD) mutation was detected in 8.6% of tumors evaluated and a pathogenic ESR1 fusion was detected in 1.6%. Most ESR1 LBD mutations/fusions were from estrogen receptor (ER)-positive samples (20.1% and 4.9%, respectively). The most common ESR1 LBD mutations included D538G (3.3%), Y537S (2.3%), and E380Q (1.1%) mutations. Among biopsy sites, ESR1 LBD mutations were most observed in liver metastases. Pathogenic ESR1 fusions were identified in 76 samples (1.6%) with 40 unique fusion partners. Evaluating co-alterations, ESR1 variant (mutation/fusion) samples more frequently expressed androgen receptor (78.0% vs 58.6, P < 0.0001) and less frequently immune checkpoint proteins than ESR1 wild-type (PD-1 20.0% vs 53.4, P < 0.05; immune cell PD-L1 10.0% vs 30.2, P < 0.0001). CONCLUSION: We have described one of the largest series of ESR1 fusions reported. ESR1 LBD mutations were commonly identified in ER-positive disease. Limited data exists regarding the clinical impact of ESR1 fusions, which could be an area for future therapeutic exploration.

Exogenously applied muscle metabolites synergistically evoke sensations of muscle fatigue and pain in human subjects.

NEW FINDINGS: What is the central question of this study? Can physiological concentrations of metabolite combinations evoke sensations of fatigue and pain when injected into skeletal muscle? If so, what sensations are evoked? What is the main finding and its importance? Low concentrations of protons, lactate and ATP evoked sensations related to fatigue. Higher concentrations of these metabolites evoked pain. Single metabolites evoked no sensations. This suggests that the combination of an ASIC receptor and a purinergic P2X receptor is required for signalling fatigue and pain. The results also suggest that two types of sensory neurons encode metabolites; one detects low concentrations of metabolites and signals sensations of fatigue, whereas the other detects higher levels of metabolites and signals ache and hot. The perception of fatigue is common in many disease states; however, the mechanisms of sensory muscle fatigue are not understood. In mice, rats and cats, muscle afferents signal metabolite production in skeletal muscle using a complex of ASIC, P2X and TRPV1 receptors. Endogenous muscle agonists for these receptors are combinations of protons, lactate and ATP. Here we applied physiological concentrations of these agonists to muscle interstitium in human subjects to determine whether this combination could activate sensations and, if so, to determine how the subjects described these sensations. Ten volunteers received infusions (0.2 ml over 30 s) containing protons, lactate and ATP under the fascia of a thumb muscle, abductor pollicis brevis. Infusion of individual metabolites at maximal amounts evoked no fatigue or pain. Metabolite combinations found in resting muscles (pH 7.4 + 300 nm ATP + 1 mm lactate) also evoked no sensation. The infusion of a metabolite combination found in muscle during moderate endurance exercise (pH 7.3 + 400 nm ATP + 5 mm lactate) produced significant fatigue sensations. Infusion of a metabolite combination associated with vigorous exercise (pH 7.2 + 500 nm ATP + 10 mm lactate) produced stronger sensations of fatigue and some ache. Higher levels of metabolites (as found with ischaemic exercise) caused more ache but no additional fatigue sensation. Thus, in a dose-dependent manner, intramuscular infusion of combinations of protons, lactate and ATP leads to fatigue sensation and eventually pain, probably through activation of ASIC, P2X and TRPV1 receptors. This is the first demonstration in humans that metabolites normally produced by exercise act in combination to activate sensory neurons that signal sensations of fatigue and muscle pain.

Continuous femoral nerve block using 0.125% bupivacaine does not prevent early ambulation after total knee arthroplasty.

BACKGROUND: Continuous femoral nerve block has been shown to decrease opioid use, improve postoperative pain scores, and decrease length of stay. However, several studies have raised the concern that continuous femoral nerve block may delay patient ambulation and increase the risk of falls during the postoperative period. QUESTIONS/PURPOSES: This study sought to determine whether continuous femoral nerve block with a single-shot sciatic block prevented early ambulation after total knee arthroplasty (TKA) and whether the technique was associated with adverse effects. METHODS: Between January 2011 and January 2013, 77 consecutive patients undergoing primary TKAs at an orthopaedic specialty hospital received a continuous femoral nerve block for perioperative analgesia. The femoral block was placed preoperatively with an initial bolus and 76 (99%) patients received a single-shot sciatic nerve block performed at the same time. Fifty-eight percent (n = 45) received an initial bolus of 0.125% bupivacaine and 42% (n = 32) received 0.25% bupivacaine. All 77 patients received 0.125% bupivacaine infusion postoperatively with the continuous femoral nerve block. All patients were provided a knee immobilizer that was worn while they were out of bed and was used until 24 hours after removal of the block. All patients also used a front-wheeled walker to assist with ambulation. All 77 patients had complete records for assessing the end points of interest in this retrospective case series, including distance ambulated each day and whether in-hospital complications could be attributed to the patients' nerve blocks. RESULTS: Thirty-five patients (45%) ambulated for a mean distance of 19 ± 22 feet on the day of surgery. On postoperative Days 1 and 2, all 77 patients successfully ambulated a mean of 160 ± 112 and 205 ± 123 feet, respectively. Forty-eight patients (62%) had documentation of ascending/descending stairs during their hospital stay. No patient fell during the postoperative period, required return to the operating room, or readmission within 90 days of surgery. One patient experienced a transient foot drop related to the sciatic nerve block, which resolved by postoperative Day 1. CONCLUSIONS: Continuous femoral nerve block with dilute bupivacaine (0.125%) can be successfully used after TKA without preventing early ambulation. By taking active steps to prevent in-hospital falls, including the use of a knee immobilizer for ambulation while the block is in effect, patients can benefit from the analgesia provided by the block and still ambulate early after TKA. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Psychological distress in hip arthroscopy patients affects postoperative pain control.

PURPOSE: To determine whether patients with higher levels of preoperative psychological distress more frequently use a postoperative fascia iliaca nerve block for pain control after hip arthroscopy, and to determine whether a fascia iliaca nerve block is an effective adjunct to multimodal oral and intravenous analgesia after hip arthroscopy. METHODS: One hundred seven patients undergoing hip arthroscopy were prospectively enrolled. Before surgery, patients were administered the Distress Risk Assessment Method questionnaire to quantify their level of preoperative psychological distress. Postoperatively, patients with pain inadequately controlled by multimodal oral and intravenous analgesics could request and receive a fascia iliaca nerve block. Pain scores, opioid consumption, time in the post-anesthesia care unit (PACU), and postoperative complications were recorded for all patients. RESULTS: Patients with normal Distress Risk Assessment Method scores requested fascia iliaca nerve blocks approximately half as frequently (18 of 50 [36%]) as patients in the at-risk category (28 of 47 [60%]) or distressed category (7 of 10 [70%]) (P = .02). Patients with high levels of distress also received 40% more intraoperative opioid than patients with normal scores (P = .04). In the study population as a whole, patients who received a fascia iliaca nerve block (n = 53) had a higher initial visual analog scale (VAS) pain score in the PACU (7.2 ± 0.3 v 5.5 ± 0.4, P = .001) and showed greater improvement in the VAS pain score by PACU discharge (-4.3 ± 0.2 v -2.1 ± 0.3, P ≤ .0001) compared with patients who did not receive a block (n = 54). CONCLUSIONS: Patients with higher levels of preoperative psychological distress more frequently requested a postoperative nerve block to achieve adequate pain control after hip arthroscopy. Patients receiving a block had greater improvement in VAS pain scores compared with patients managed with oral and intravenous analgesics alone. LEVEL OF EVIDENCE: Level IV, case series.

Fascial plane approach to anesthetizing the radial, median, and ulnar nerves: an educational review.

Brachial plexus block provides effective anesthesia and analgesia for upper extremity surgery but requires injection of large anesthetic volumes near major vascular structures. Moreover, the extensive motor and sensory loss produced by plexus block often exceeds the neural distribution needed for corresponding surgical procedures.High-resolution ultrasound facilitates selective nerve blocks at nearly every level of the upper extremity. We present fascial plane injection techniques for selective radial, median, and ulnar nerve blocks. These techniques can be used to match sensory distribution with specific surgical procedures. They are performed using low anesthetic volumes and without proximity to nerves or vascular structures. In this article, fresh cadaver dissections with corresponding ultrasound images are used to demonstrate stepwise fascial plane techniques for the radial, median, and ulnar nerves. These techniques are performed using familiar anatomic landmarks.Practical applications of these techniques are demonstrated for commonly performed procedures of the upper extremity. Corresponding injection volumes with duration of postoperative analgesia are presented. Selected injections are described for both surgical anesthesia and postoperative analgesia.Selective fascial plane injections can provide surgical anesthesia and postoperative analgesia in settings that might otherwise require much larger volumes of local anesthetic. These selective nerve blocks can match sensory loss with the anatomic pain distribution in each patient. Reliable techniques for selective nerve blocks of the upper extremity can expand the capabilities for ultrasound-guided regional anesthesia.

The Effect of Anesthesia on Passive Ankle Dorsiflexion.

BACKGROUND: Equinus contractures can commonly be due to contractures of gastrocnemius muscle or combined contractures of the gastrocnemius-soleus Achilles tendon complex. The decision to release part or all of the gastrocnemius-soleus Achilles tendon complex is often assessed intraoperatively while the patient is under anesthesia. It remains unknown whether the administration of general anesthesia affects the measurement of passive ankle dorsiflexion. METHODS: The unaffected, nonoperative limb on 46 foot and ankle patients underwent a Silfverskiold test measuring passive ankle dorsiflexion preoperatively and intraoperatively after administration of general anesthesia using an instrumented force-angular displacement goniometer. To determine clinical significance, we surveyed experienced surgeons to estimate the perceived minimally detectable clinical accuracy for measuring passive ankle dorsiflexion. RESULTS: Forty-six subjects were included with mean age of 42 ± 14.8 years, mean body mass index of 26.2 ± 4.9, and 52% female. The mean change in dorsiflexion values from before anesthesia to after the administration of general anesthesia was 1.9 degrees with 10 lb of pressure with knee extended (E10), 2.3 degrees with 20 lb of pressure with knee extended (E20), 2.8 degrees with 10 lb of pressure with knee flexed (F10), and 2.3 degrees with 20 lb of pressure with knee flexed (F20) (all P < .001). Thirty-three of 45 (73%) surgeons responded to the survey; all thought their minimally detectable clinical accuracy was 5 degrees or greater. CONCLUSION: After the administration of general anesthesia, a small but likely not clinically detectable increase in passive ankle dorsiflexion occurs. The common clinical practice of making intraoperative treatment decisions regarding the presence of a gastrocnemius-soleus driven equinus contractures after general anesthesia without use of paralytic agents appears reasonable given the magnitude of the changes identified in this study.

The Effect of Critical Task Auto-failure Criteria on Medical Evaluation Methods in the Pararescue Schoolhouse.

BACKGROUND: Medical training and evaluation are important for mission readiness in the pararescue career field. Because evaluation methods are not standardized, evaluation methods must align with training objectives. We propose an alternative evaluation method and discuss relevant factors when designing military medical evaluation metrics. METHODS: We compared two evaluation methods, the traditional checklist (TC) method used in the pararescue apprentice course and an alternative weighted checklist (AWC) method like that used at the U.S. Army static line jumpmaster course. The AWC allows up to two minor errors, while critical task errors result in autofailure. We recorded 168 medical scenarios during two Apprentice course classes and retroactively compared the two evaluation methods. RESULTS: Despite the possibility of auto-failure with the AWC, there was no significant difference between the two evaluation methods, and both showed similar overall pass rates (TC=50% pass, AWC=48.8% pass, p=.41). The two evaluation methods yielded the same result for 147 out of 168 scenarios (87.5%). CONCLUSIONS: The AWC method strongly emphasizes critical tasks without significantly increasing failures. It may provide additional benefits by being more closely aligned with our training objectives while providing quantifiable data for a longitudinal review of student performance.

Diaphragm function after interscalene brachial plexus block: a double-blind, randomized comparison of 0.25% and 0.125% bupivacaine.

BACKGROUND: Interscalene brachial plexus block (ISBPB) provides excellent analgesia after rotator cuff surgery but is associated with diaphragm dysfunction. In this study, ISBPB with 20 mL of 0.125% or 0.25% bupivacaine were compared to assess the effect on diaphragm function, oxygen saturation, pain control, opioid requirements, and patient satisfaction. MATERIALS AND METHODS: In this prospective, randomized, double-blind study, 30 adults undergoing outpatient arthroscopic rotator cuff repair were enrolled to receive ultrasound-guided interscalene brachial plexus catheter placement with 20 mL of 0.125% (n = 15) or 0.25% bupivacaine (n = 15). Diaphragm function and oxygen saturation were assessed before ISBPB placement and on discharge from the postanesthesia care unit. Postoperative pain scores, opioid requirements, and patient satisfaction were compared. RESULTS: Diaphragm function and oxygen saturation were superior in the low concentration group. Absent or paradoxic motion of the diaphragm was present in 78% of the 0.25% group compared with 21% of patients in the 0.125% group (P = .008). Oxygen saturation decreased 4.3% in the 0.25% group compared with a decrease of 2.6% in the 0.125% group (P = .04). Pain scores averaged 1 of 10 in the 0.25% group and 0 of 10 in the 0.125% group (P = .02). Opioid requirements and patient satisfaction were not different between the two groups. CONCLUSIONS: In this randomized, double-blind comparison of ISBPB performed with 20 mL of 0.125% or 0.25% bupivacaine, diaphragm function and oxygen saturation were superior in patients treated with more dilute bupivacaine. Furthermore, there were no clinically significant differences in pain scores, and no statistically significant differences in opioid requirements and patient satisfaction.

Scheduled, Simultaneous Dosing of Pregabalin, Celecoxib, and Acetaminophen Markedly Reduces or Eliminates Opioid Use After ACL Reconstruction Using Allograft or Hamstring Tendon Autograft: A Randomized Clinical Trial.

Background: Opioid analgesics continue to be prescribed after ambulatory surgery despite untoward adverse effects, risk of overdose, and association with substance use disorder. Purpose/Hypothesis: The purpose was to investigate the use of a novel system to provide scheduled and simultaneous dosing of acetaminophen, celecoxib, and pregabalin after anterior cruciate ligament reconstruction (ACLR). It was hypothesized that this system would markedly reduce pain and opioid use compared with existing best practice. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Included were 100 patients scheduled for elective, primary ACLR using allograft or hamstring tendon autograft. Selection criteria included age between 18 and 65 years and weight between 65 and 120 kg. Exclusion criteria were a known allergy to any drug used in the study or the use of opioid analgesics before surgery. Patients in the intervention group received a blister pack with scheduled, simultaneous doses of acetaminophen, celecoxib, and pregabalin; patients were also given oxycodone 5 mg as needed for breakthrough pain. Patients in the control group were prescribed ibuprofen and oxycodone 5 mg/acetaminophen 325 mg as needed for pain. The primary outcome measure was pain. Secondary outcomes were nausea, itching, and daily oxycodone use. Patients were asked to quantify their average pain at rest, nausea, and itching on an 11-point verbal scale (from 0 to 10). These data were recorded for 6 days during daily telephone contacts with patients after hospital discharge. Results: Cumulative results for 6 days showed significantly lower values in the intervention group compared with the control group for pain (median [interquartile range], 28 [14-35] vs 35 [28-41], respectively; P = .009) and oxycodone use (median [interquartile range] number of tablets, 0 [0-2] vs 8 [1.25-16], respectively; P < .001). Based on these data, the upper tolerance limits for the number of oxycodone tablets required by 90% of patients in the intervention and control groups were 8 tablets and 30 tablets, respectively. Cumulative results for nausea and itching were also significantly lower for the intervention group. Most patients in the intervention group used no opioids during recovery. Conclusion: Simultaneous dosing of 3 nonopioid analgesics resulted in reduced postoperative pain and markedly lower opioid use. Registration: NCT04015908 (ClinicalTrials.gov identifier).

Randomized controlled trial of a simplified adductor canal block performed for analgesia following total knee arthroplasty.

BACKGROUND AND OBJECTIVES: The objective of the study was to determine if injection of local anesthetic into the vastus medialis and sartorius muscles adjacent to the adductor canal produces sensory changes comparable with adductor canal block (ACB). This could result in a technically easier and potentially safer alternative to ACB. METHODS: In this randomized controlled trial, patients received either ACB (n=20) or a simplified adductor canal (SAC) block performed using a new fenestrated nerve block needle (n=20). The time to perform each block as well as the number of attempts to position the needle were evaluated. A non-inferiority test was used to compare pain scores and opioid requirements for the ACB and the SAC block. RESULTS: The SAC block was performed more rapidly, with fewer needle passes, and had a higher success rate than the ACB. Three block failures and two vessel punctures were observed in the ACB group, while none of these events occurred in SAC block patients. Analgesia and opioid consumption for patients treated with the SAC block were not inferior to ACB. CONCLUSION: The SAC block is technically easier to perform and potentially safer than ACB. This procedure can be performed using easily visible ultrasound landmarks and has the potential for use among a wide range of healthcare providers. TRIAL REGISTRATION NUMBER: NCT02786888.

A novel approach for assessing catheter position after ultrasound-guided placement of continuous interscalene block.

The increasing use of ultrasound has allowed anesthesiologists to perform nerve blocks with a high success rate and without nerve stimulation or eliciting a paresthesia. The ability to visualize peripheral nerve catheters using ultrasound is limited. We present a novel method to confirm the position of an interscalene catheter tip using injection of agitated contrast. The described technique is simple and allows timely assessment of catheter tip position.

Indwelling interscalene catheter use in an outpatient setting for shoulder surgery: technique, efficacy, and complications.

Indwelling interscalene catheters are utilized for inpatient postoperative pain control after shoulder surgery. Improved medical equipment and advanced techniques may allow safe and efficacious outpatient use. One hundred and forty-four consecutive indwelling interscalene catheter placements were reviewed to determine adverse events, complications, and efficacy. Real-time ultrasound-guided catheter placement technique is described. Post-anesthesia care unit (PACU) narcotic consumption and last recorded pain score were reviewed to gauge efficacy. The catheter placement technique was 98% successful. There were 14 (9.7%) minor adverse events including inadequate analgesia (8), accidental catheter removal (4) of disconnection (1), and shortness of breath (1). The single complication (0.7%) was a small apical pneumothorax. The average PACU narcotic consumption in intravenous morphine equivalents was 1.7 mg. The average last recorded PACU pain score on a scale of 1 to 10 was 0.6. Catheter placement under real-time ultrasound guidance is accurate. Outpatient use of indwelling interscalene catheters is safe and efficacious.

Evaluation of a new fenestrated needle for ultrasound-guided fascia iliaca block.

STUDY OBJECTIVE: To evaluate a new 20-gauge (G) fenestrated needle designed to be used with ultrasound guidance to deliver local anesthetic into the tissue plane of the fascia iliaca without immediate proximity to the femoral nerve. DESIGN: Prospective study. SETTING: University hospital. PATIENTS: 15 male volunteers. INTERVENTIONS: To determine the onset of motor and sensory block after ultrasound-guided injection of 1% lidocaine and iopamidol, fluoroscopy was performed during and after injection to discover the pattern of local anesthetic distribution. The buckling strength of the new needle was compared using a standard mechanical testing protocol to a conventional 22-G needle (Quincke type). MEASUREMENTS AND MAIN RESULTS: Injection through the fenestrated needle consistently produced sensory block in the anterior, medial, and lateral aspects of the thigh. All subjects were also observed to have loss of motor function in the quadriceps muscle. No subject experienced motor effect in the adductor muscles of the thigh. The fenestrated 20-G needle yielded at significantly larger compressive forces than did the standard 22-G needle (P < 0.001). CONCLUSION: The needle is novel in that it does not require immediate proximity to the femoral nerve or precise placement of the needle tip in the plane of the fascia iliaca. The 20-G fenestrated needle is stronger under compressive force than existing 22-G needles.

Outpatient management of continuous peripheral nerve catheters placed using ultrasound guidance: an experience in 620 patients.

BACKGROUND: Continuous peripheral nerve block (CPNB) is an optimal choice for analgesia after orthopedic procedures, but is not commonly used in outpatients because of concern regarding the possibility of catheter-related complications. In addition, it may be difficult to provide adequate patient access to physicians in this setting. We present 620 outpatients who were treated with CPNB using an established protocol. METHODS: All catheters were placed using direct ultrasound visualization. These patients received extensive oral and written preoperative instruction and were provided continuous telephone access to the anesthesiologist during the postoperative period. All patients were also contacted at home by telephone on the first postoperative day. In addition, each patient was seen and examined by the surgeon within 2 wk of hospital discharge. RESULTS: Of the 620 patients, there were 190 interscalene (brachial plexus), 206 fascia iliaca (femoral nerve), and 224 popliteal fossa (sciatic nerve) catheters. Two patients (0.3%) had complications related to the nerve block. In both of these patients, the symptoms resolved within 6 wk of surgery. Twenty-six patients (4.2%) required postoperative interventions by the anesthesiologist. One patient returned to the hospital for catheter removal. CONCLUSIONS: In this large series of outpatients treated with CPNB, there were surprisingly few interventions requiring an anesthesiologist. Likewise, patients were able to manage and remove their catheters at home without additional follow-up. This suggests that with adequate instruction and telephone access to health care providers, patients are comfortable with managing and removing CPNB catheters at home.

Evaluation of a New Needle Guidance System for Ultrasound: Results of a Prospective, Randomized, Blinded Study.

BACKGROUND AND OBJECTIVES: Accurate needle control during ultrasound (US)-guided nerve blocks may be an elusive goal for the anesthesiologist. Despite modifications to increase echogenicity, needle visibility still requires precise alignment within the transducer beam. In this study, we evaluated a magnetically guided ultrasound (MGU) system that produces a real-time, graphic display of the needle position and trajectory that is independent of the US beam. METHODS: The MGU system was compared with echogenic needles and conventional ultrasound (CU) by anesthesiologists with and without prior experience performing US-guided nerve blocks. Participants were asked to perform tasks to quantify accuracy with respect to needle direction (directional accuracy) and needle tip position (positional accuracy). These evaluations were performed in a porcine tissue model. RESULTS: Regarding directional accuracy, inexperienced subjects were able to contact a target capsule with a single needle pass during both in-plane (IP) and out-of-plane (OOP) approaches using the magnetic guidance system. By contrast, using CU, subjects required redirection 3.8 ± 2.4 (P = 0.02), and 4.5 ± 3.9 (P = 0.04) times, respectively, for IP and OOP approaches. Experienced subjects contacted the target capsule with a single pass for both IP and OOP approaches when using the magnetic guidance system. With CU, experienced subjects were able to contact the target with a single pass using an IP approach but required redirection 3.4 ± 2.8 (P = 0.046) times during OOP approaches. Positional accuracy was also superior for both inexperienced (P = 0.04) and experienced (P = 0.02) users during an OOP approach. CONCLUSIONS: In a tissue model, the MGU system improved control of needle trajectory and needle tip position for both inexperienced and experienced subjects.

Local anesthetic injection deep to the fascia iliaca at the level of the inguinal ligament: the pattern of distribution and effects on the obturator nerve.

STUDY OBJECTIVE: The femoral, lateral femoral cutaneous, and obturator nerves (ONs) can reportedly be blocked using a single-injection deep to the fascia iliaca (FI) at the level of the inguinal ligament. Two commonly used methods (the FI compartment and 3-in-1 blocks) have produced inconsistent results with respect to local anesthetic distribution and effect on the ON. To date, no study of either method has been performed using advanced imaging techniques to document both needle placement and local anesthetic distribution. We report the outcome of a series of 3-in-1 and FI blocks performed using ultrasound to guide needle position and magnetic resonance imaging (MRI) to define local anesthetic distribution. DESIGN: Patients were prospectively studied, and images were interpreted using a randomized and blinded protocol. SETTING: The study was performed in the perioperative area of an academic orthopedic specialty hospital. PATIENTS: Ten patients (ASA 1-2) having anterior cruciate ligament reconstruction received either 3-in-1 or FI compartment blocks for postoperative analgesia using the surface landmarks described for these techniques. INTERVENTIONS: Ultrasound was used to position the injecting needle immediately deep to the FI. Local anesthetic distribution was studied using MRI. MEASUREMENTS: Patients were examined for motor and/or sensory function of the femoral, obturator, and lateral femoral cutaneous nerves. Magnetic resonance imaging was used to document the limits of injectate distribution. MAIN RESULTS: Magnetic resonance imaging showed distribution of injectate over the surface of the iliacus and psoas muscles to the level of the retroperitoneum. No patient showed medial extension of injectate to the ON. At the level of the inguinal ligament, injectate extended laterally toward the anterior superior iliac spine and medially to the femoral vein. All patients had significant weakness with extension of the knee and sensory loss over the anterior, lateral, and medial thigh. No patient demonstrated decreased hip adductor strength. CONCLUSIONS: Ultrasound and MRI show consistent superior extension of local anesthetic to the level of the retroperitoneum for both techniques. There was reliable clinical effect on the femoral and lateral femoral cutaneous nerves. However, none of the injections produced evidence of ON block either at the level of the retroperitoneum or the inguinal ligament.