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An Obturator Nerve Block does not Alleviate Postoperative Pain after Total Hip Arthroplasty: a Randomized Clinical Trial
  1. Niels Dalsgaard Nielsen1,2,3,
  2. Charlotte Runge1,
  3. Louise Clemmesen1,
  4. Jens Børglum4,
  5. Lone Ramer Mikkelsen1,2,
  6. Jens Rolighed Larsen1,2,
  7. Thomas Dahl Nielsen3,
  8. Kjeld Søballe2,5 and
  9. Thomas Fichtner Bendtsen2,3
  1. 1 Elective Surgery Center, Silkeborg Regional Hospital, Silkeborg, Denmark
  2. 2 Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
  3. 3 Department of Anesthesiology, Aarhus University Hospital, Aarhus, Denmark
  4. 4 Department of Anesthesiology and Intensive Care Medicine, Zealand University Hospital, University of Copenhagen, Roskilde, Denmark
  5. 5 Department of Orthopedic Surgery, Aarhus University Hospital, Aarhus, Denmark
  1. Correspondence to Dr Thomas Fichtner Bendtsen, Department of Anesthesiology, Aarhus University Hospital, Aarhus 8200, Denmark; tfb{at}


Background and objectives A substantial group of patients suffer from moderate to severe pain following elective total hip arthroplasty (THA). Due to the complex innervation of the hip, peripheral nerve block techniques can be challenging and are not widely used. Since the obturator nerve innervates both the anteromedial part of the joint capsule as well as intra-articular nociceptors, we hypothesized that an obturator nerve block (ONB) would decrease the opioid consumption after THA.

Methods Sixty-two patients were randomized to receive ONB or placebo (PCB) after primary THA in spinal anesthesia. Primary outcome measure was opioid consumption during the first 12 postoperative hours. Secondary outcome measures included postoperative pain score, nausea score and ability to ambulate.

Results Sixty patients were included in the analysis. Mean (SD) opioid consumption during the first 12 postoperative hours was 39.9 (22.3) mg peroral morphine equivalents (PME) in the ONB group and 40.5 (30.5) mg PME in the PCB group (p=0.93). No difference in level of pain or nausea was found between the groups. Paralysis of the hip adductor muscles in the ONB group reduced the control of the operated lower extremity compared with the PCB group (p=0.026). This did, however, not affect the subjects’ ability to ambulate.

Conclusions A significant reduction in postoperative opioid consumption was not found for active versus PCB ONB after THA.

Trial registration number NCT03064165 and 2017-000068-14.

  • lower extremity
  • pain outcome measurement
  • acute pain

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  • Contributors Conception or design of the work: NDN, CR, LC, JB, LRM, JRL, TDN, KS, TFB. Data collection: NDN, CR, LC. Data analysis and interpretation: NDN, CR, JB, TDN, TFB. Drafting the article: NDN. Critical revision of the article: CR, LC, JB, LRM, JRL, TDN, KS, TFB. Final approval of the version to be published: NDN, CR, LC, JB, LRM, JRL, TDN, KS, TFB.

  • Funding The study was supported by the Toyota Foundation, Director Kurt Bønnelycke and Wife Grethe Bønnelyckes Foundation, and the AP Møller and Chastine Mc-Kinney Møller Foundation.

  • Disclaimer The content is solely the responsibility of the authors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval Ethics Committee of the Central Denmark Region (1-10-72-90-17), Danish Medicines Agency (2017-000068-14), Danish Data Protection Agency (1-16-02-182-17).

  • Provenance and peer review Not commissioned; externally peer reviewed.