Hip strengthening exercise dosage is not associated with clinical improvements after total hip arthroplasty – a prospective cohort study (the PHETHAS-1 study)

Purpose Postoperative rehabilitation exercise is commonly prescribed after total hip arthroplasty (THA), but its efficacy compared to no or minimal rehabilitation exercise has been questioned. Preliminary efficacy would be indicated if a dose-response relationship exists between performed exercise dose and degree of postoperative recovery. The objective was to evaluate the preliminary efficacy of home-based rehabilitation using elastic band exercise on performance-based function after THA, based on the association between performed exercise dose and change in performance-based function (gait speed) from 3 (start of intervention) to 10 weeks (end of intervention) after surgery. Methods A pre-registered ([NCT03109821][1]) prospective cohort study was conducted. Following primary THA, patients were prescribed home-based rehabilitation exercise using elastic bands. Performed exercise dose (repetitions/week) was objectively measured using attached sensor technology. Primary outcome was change in gait speed (40m fast-paced walk test). Secondary outcomes included patient-reported hip disability. In the primary analysis, a linear regression model was used. Results Ninety-four patients (39 women) with a median age of 66.5 years performed a median of 339 exercise repetitions/week (1st-3rd quartile: 209-549). Across outcomes, participants significantly improved from 3 to 10-week follow-up. The association between performed exercise dose and change in mean gait speed was 0.01 m/sec [95% CI: -0.01; 0.02] per 100 repetitions. Conclusions We found no indication of preliminary efficacy of home-based rehabilitation exercise using elastic bands, as no significant and clinically relevant associations between performed exercise dose and changes in outcomes were present. Trials comparing postoperative rehabilitation exercise with no exercise early after THA are warranted. ### Competing Interest Statement All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (see supplementary file) and declare: research grants for the submitted work are described in the funding statement; no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work. ### Clinical Trial NCT03109821 ### Funding Statement The PHETHAS-1 study has received grants from: Regional Hospital Central Jutland Research Foundation, The Danish Rheumatism Association, The Association of Danish Physiotherapists, The Aase and Ejnar Danielsen Foundation and The family Kjærsgaard foundation. The PHETHAS-1 study is part of a PhD project, which has also received funding from The Faculty of Health, Aarhus University, The Department of Clinical Medicine, Aarhus University and the Frimodt-Heineke Foundation. The funding sources had no part in the design, conduction or reporting of the trial, thus there is no conflict of interests. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was reported to The Central Denmark Region Committee on Health Research Ethics and was reviewed as non-notifiable (Inquiry 270/2017). The study was approved by the Danish Data Protection Agency (ref. no: 1-16-02-589-15). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The dataset generated and analysed to provide Figure 1, Table 1 and Appendix B, Table B1 (demographics and participant characteristics) cannot be fully anonymized. Hence, public deposition of these data points is not possible due to Denmarks national legislation (Data Protection Act paragraph 10 and Data Disclosure Proclamation Act) which outline that we can only transfer pseudonymized data to the preprint repository after the Data Protection Authorities approval (Data Protection Act, paragraph 10, section 3, nr. 3.). Reviewers and others may obtain access to the data (used in the primary and secondary analyses) by reasonable request, on condition that the Danish Data Protection Agency has approved of the data transfer from the Central Jutland Region to the preprint repository. If others are to gain access to the data, the preprint repository shall ensure that there is an adequate legal basis to share the Central Jutland Regions data and ensure that the data is only being processed for scientific research purposes. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT03109821&atom=%2Fmedrxiv%2Fearly%2F2023%2F07%2F13%2F2023.07.12.23292442.atom