Wisniewski, Steve J.

BackgroundUltrasound (US)‐guided hip joint injections are commonly performed for patients with suspected or known intra‐articular hip pain. Lidocaine is a well‐established local anesthetic used prior to hip joint injections, but it is often associated with discomfort during infiltration. Bacteriostatic saline is an alternative local anesthetic that has been shown to be less painful during infiltration for superficial injections.ObjectiveTo compare infiltrative pain and anesthetic efficacy of bacteriostatic saline (0.9% benzyl alcohol) with a standard local anesthetic (buffered 1% lidocaine) used for local anesthesia prior to US‐guided intra‐articular hip corticosteroid injections.DesignDouble‐blinded, randomized controlled trial.SettingTertiary care medical center.ParticipantsSixty eight patients age 18‐80 (mean 54.8) years referred for US‐guided intra‐articular hip corticosteroid injections.InterventionPatients were randomized to receive a US‐guided hip joint corticosteroid injection using either bacteriostatic saline or buffered 1% lidocaine for preinjection local anesthesia.Main Outcome MeasuresVisual Analog Scale (VAS) for pain (0‐100) during local anesthetic infiltration as well as during the intra‐articular injection. Adverse events were also recorded.ResultsThere were no significant differences between bacteriostatic saline and buffered lidocaine with respect to pain during local anesthetic infiltration or during the subsequent intra‐articular injection. Pain VAS during local anesthetic infiltration was 13.2 (95% confidence interval [CI] 7.8, 18.5) in the bacteriostatic saline group and 14.0 (95% CI 9.4, 18.5) in the buffered 1% lidocaine group (P = .82). Furthermore, pain VAS during the intra‐articular injection was 20.7 (95% CI 14.1, 27.3) in the bacteriostatic saline group and 15.7 (95% CI 10.9, 20.3) in the buffered 1% lidocaine group (P = .57). No adverse events occurred.ConclusionsBacteriostatic saline is a safe and comparably effective alternative to buffered 1% lidocaine for local anesthesia before US‐guided hip joint injections and may be considered for subcutaneous/periarticular anesthesia during similar musculoskeletal procedures.

A 16‐year‐old high school football player presented with 4 months of anterior knee pain and small, mobile, prepatellar “lumps” after falling onto an opponent's cleat. He reported knee pain primarily during knee flexion and direct pressure during squatting and kneeling. Knee radiographs were unremarkable. Ultrasonography revealed multiple, freely mobile, subcutaneous nodules of variable size and echogenicity in the prepatellar region. Analysis of magnetic resonance imaging suggested possible fat necrosis but was nondiagnostic. The patient opted for surgical exploration, at which time multiple, opalescent subcutaneous nodules were removed. Pathology was consistent with encapsulated fat necrosis. After surgery, his symptoms resolved, and he returned to sports without restrictions.

ObjectivesTo 1) describe and validate an ultrasound‐guided ischial bursa injection technique in an unembalmed cadaveric model and 2) to compare the distance between the ischial tuberosity and the sciatic nerve in a hip neutral versus 90° flexed hip position in asymptomatic volunteers.DesignThe first part was a single‐blind prospective study. The second part was a prospective cohort study.SettingAn academic institution procedural skills laboratory and outpatient clinic.ParticipantsThe first part of the study involved 1 cadaveric specimen. The second part of the study involved 20 asymptomatic subjects. The mean age of the subjects was 28 years, and the mean (standard deviation) body mass index was 23.2 ± 2.8 kg/m2 (minimum, 18.3 kg/m2; maximum, 29.5 kg/m2).MethodsIn the first part of the study, a single operator completed bilateral ultrasound‐guided ischial bursa injections in an unembalmed cadaveric specimen by using diluted colored latex. In the second part of the study, ultrasound was used in 20 asymptomatic volunteer subjects (10 men and 10 women) to measure the distance from the lateral edge of the ischial tuberosity to the sciatic nerve.Main Outcome MeasurementsThe injections were graded for accuracy as follows: accurate (all injectate contained within the ischial bursa), accurate with overflow (injectate within the ischial bursa but also located in adjacent structures other than the needle track), or inaccurate (injectate not within the ischial bursa). The second part of the study measured the distance from the ischial tuberosity to the sciatic nerve with subjects in 2 different positions (prone and side lying with the tested hip flexed to 90°).ResultsPostinjection cadaveric dissections revealed that both ultrasound‐guided injections accurately placed liquid latex within the ischial bursae. There was no evidence of injury to surrounding neurovascular structures. Among asymptomatic volunteers, the average distance between the ischial tuberosity and the sciatic nerve increased from 28.4 mm (range, 20.5‐38.9 mm) in the neutral position to 41.9 mm (range, 30.9‐66.0 mm) with the hip flexed to 90° (average change, 13.5 mm away from the ischial tuberosity; P = .0001).ConclusionsUltrasound‐guided ischial bursa injections are technically feasible. Flexing the hip to 90° increases the distance between the ischial tuberosity and the sciatic nerve in asymptomatic volunteers, thus potentially resulting in a safer needle trajectory when ischial bursa injections are clinically indicated. Further investigation in clinical settings is warranted to validate these findings.