Objective Compare the effect of posterior surgical approach (PA) vs direct anterior approach (DAA) on speed of recovery from pain and dysfunction and on intrathecal oxytocin analgesia after total hip arthroplasty (THA).

Study design Nested cohort within a randomized, controlled, double-blind trial

Subjects Individuals aged 31 to 80 years undergoing total hip arthroplasty (THA)

Methods In this secondary analysis of a randomized controlled trial, the association between surgical approach and number of daily steps was assessed, and whether this was modified by receipt of intrathecal oxytocin. Data were collected from accelerometers and daily patient diaries in the first eight weeks postoperatively. Outcomes were analyzed using generalized linear regression models.

Results Ninety patients underwent THA, of which 35 (38.9%) received a PA. Patients were predominantly female (57.8%) with a mean age of 60.6 (standard deviation [SD] 9.3) years. On postoperative day one patients who received a PA with placebo took more steps (mean difference [MD] 53.72, 95% CI: −1717.86, 1825.31) than patients who underwent a DAA. Trajectories were significantly modified by whether they received oxytocin, in which patients who underwent PA with oxytocin took more steps than patients who underwent DAA (p<0.001).

Discussion Further studies are needed to understand mechanisms underlying oxytocin’s interaction with surgical approach and guide considerations for recovery after THA.

The authors have declared no competing interest.

NCT03011307 IND107166

This study was funded by grant R37 GM48085 from the National Institute of General Medical Sciences, NIH, USA

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

IRB of Wake Forest University School of Medicine gave ethical approval for this work

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↵* A complete list of collaborators is included in Supplementary Appendix 1.

Disclosures: The authors have no conflicts of interest to disclose

Funding: This work was supported by grant R37 GM48085 from the National Institute of General Medical Sciences, National Institutes of Health, Bethesda, MD.

Ethics: This study was approved by the Wake Forest Health Sciences IRB on 04/21/2014 (IRB00027272).

Device/Drug Statement: Oxytocin by intrathecal administration is not FDA-approved. This study was performed under Investigational New Drug approval 107,166 from the US Food and Drug Administration for intrathecal administration of oxytocin.

Trial registration: This study was registered at ClinicalTrials.gov on 01/03/2017 (NCT03011307). The first subject was studied on 02/27/2017.

All data produced in the present study are available upon reasonable request to the authors