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Step Activity After Surgical Treatment of Ankle Arthritis

Shofer, Jane B. MS1; Ledoux, William R. PhD1,2; Orendurff, Michael S. PhD1,3; Hansen, Sigvard T. MD2; Davitt, James MD4; Anderson, John G. MD5; Bohay, Donald MD5; Coetzee, J. Chris MD6; Houghton, Michael MD7; Norvell, Daniel C. PhD8; Sangeorzan, Bruce J. MD1,2

doi: 10.2106/JBJS.18.00511
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Background: Ambulatory activity is reduced in patients with ankle arthritis. In this study, we measured step activity over time in 2 treatment groups and secondarily compared step activity with results of patient-reported outcome measures (PROMs).

Methods: Patients who were treated with either ankle arthrodesis or ankle arthroplasty wore a step activity monitor preoperatively and at 6, 12, 24, and 36 months postoperatively. Changes from preoperative baseline in total steps per day and per-day metrics of low, medium, and high-activity step counts were measured in both treatment groups. Step activity was compared with each subject’s PROM scores as reported on the Musculoskeletal Function Assessment (MFA) and the Short Form-36 (SF-36) physical function and bodily pain subscales.

Results: Of the 3 activity levels, combined group high-activity step counts showed the greatest increase (mean of 278 steps [95% confidence interval (CI), 150 to 407 steps], a 46% improvement from preoperatively). At 6 months, the mean high-activity step improvement for the arthroplasty group was 194 steps compared with a mean decline of 44 steps for the arthrodesis group (mean 238-step difference [95% CI, −60 to 536 steps]). By 36 months postoperatively, the greater improvement in high-activity steps for the arthroplasty versus the arthrodesis group was no longer present. There were no significant pairwise differences in improvement based on surgical treatment method at any individual follow-up time point. For a within-patient increase of 1,000 total steps, there was a mean change in the MFA, SF-36 physical function, and SF-36 bodily pain scores of −1.8 (95% CI, −2.4 to −1.2), 3.8 (95% CI, 2.8 to 4.8), and 2.8 (95% CI, 1.8 to 3.9), respectively (p < 0.0001 for all associations). There was no evidence that the association differed by study visit, or by study visit and surgical procedure interaction (p > 0.10).

Conclusions: Surgical treatment of ankle arthritis significantly improves ambulatory activity, with greater change occurring at high activity levels. Improvement may occur more quickly following arthroplasty than arthrodesis, but at 3 years, we detected no significant difference between the 2 procedures. Step counts, while associated with PROMs, do not parallel them, and thus may be a useful supplementary measure, particularly in longitudinal studies.

Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

1RR&D Center, VA Puget Sound Health Care System, Seattle, Washington

2Departments of Mechanical Engineering (W.R.L.) and Orthopaedics & Sports Medicine (W.R.L., S.T.H., and B.J.S.), University of Washington, Seattle, Washington

3Motion & Sports Performance Laboratory, Stanford Children’s Health, Palo Alto, California

4Orthopedic + Fracture Specialists, Portland, Oregon

5Orthopaedic Associates of Michigan, Grand Rapids, Michigan

6Twin Cities Orthopedics, Edina, Minnesota

7Orthopaedic & Spine Center of the Rockies, Fort Collins, Colorado

8Spectrum Research, Tacoma, Washington

E-mail address for B.J. Sangeorzan: bsangeor@uw.edu

Disclosure: This project was funded by the U.S. Department of Veterans Affairs (VA), Rehabilitation Research & Development Grant A4153R. Long-term follow-up was supported by VA grants A4843C and A9243C. The VA played no role in the investigation. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work (http://links.lww.com/JBJS/F318).

Written work prepared by employees of the Federal Government as part of their official duties is, under the United States Copyright Act, a ‘work of the United States Government’ for which copyright protection under that Act is not available. As such, copyright protection does not extend to the contributions of employees of the Federal Government prepared as part of their employment.
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