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Patterns of Functional Improvement After Revision Knee Arthroplasty

¹ Division of Health Policy, Department of Public Health, Weill Cornell Medical College and Hospital for Special Surgery, 402 67^th Street, New York, NY 10065. E-mail address: hag2008{at}med.cornell.edu
² Division of Health Policy and Management, University of Minnesota School of Public Health, 420 Delaware Street S.E., Mayo Building D-351, Minneapolis, MN 55455
³ Division of Biostatistics, University of Minnesota School of Public Health, 420 Delaware Street S.E., Mayo Mail Code 303, Minneapolis, MN 55455
⁴ Department of Orthopedics, A40, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195
⁵ Division of Orthopaedic Surgery, Department of Surgery, Southern Illinois University School of Medicine, 701 North First Street, P.O. Box 19679, Springfield, IL 62794

^* The principal investigator for the NAKAR Study Group is Khaled J. Saleh, MD, MSc, FRCSC, MHCM, Southern Illinois University School of Medicine. The coinvestigators are Robert Bourne, MD, London Health Sciences Centre, Charles Clark, MD, University of Iowa Hospitals and Clinics, Gerard Engh, MD, Anderson Orthopaedic Research Institute, Terence Gioe, MD, University of Minnesota, Steven Haas, MD, Hospital for Special Surgery, David Heck, MD, Texas Surgical Associates, Richard Iorio, MD, Lahey Clinic, Craig Israelite, MD, University of Pennsylvania, William Healy, MD, Lahey Clinic, Kenneth Krackow, MD, Kaleida/Buffalo General Hospital, Paul Lotke, MD, University of Pennsylvania, Charles Nelson, MD, University of Pennsylvania, William Macaulay, MD, Columbia University, Steve MacDonald, MD, London Health Sciences Centre, William Mihalko, MD, PhD, Campbell Clinic, Michael Mont, MD, Rubin Institute for Advanced Orthopaedics, Cecil Rorabeck, MD, London Health Sciences Centre, Sean Scully, MD, University of Miami, Giles Scuderi, MD, Insall Scott Kelly Institute, Russell Windsor, MD, Hospital for Special Surgery, Mathias Bostrom, MD, Hospital for Special Surgery, Thomas Sculco, MD, Hospital for Special Surgery, Marc Swiontkowski, MD, University of Minnesota, Boris Bershadsky, PhD, Cleveland Clinic Foundation, Robert Kane, MD, University of Minnesota, and Hassan Ghomrawi, PhD, MPH, Weill Cornell Medical College.

Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from the Orthopaedic Research and Education Foundation, American Geriatrics Society, and The Knee Society. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. Commercial entities (Apopharma, Inc.; ARS Arthro, AG; Arthrosurface; BioMimetic; DePuy; DIApedia, LLC; King Pharmaceuticals; MCS; Small Bone Innovations; Stryker; TissueLink; and ReGen Biologics) paid or directed in any one year, or agreed to pay or direct, benefits in excess of $10,000 (all except ReGen Biologics, which provided benefits of less than $10,000) to a research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which one or more of the authors, or a member of his or her immediate family, is affiliated or associated.

Methods: Three hundred and eight patients in need of revision surgery were enrolled into the study, conducted at seventeen centers, and 221 (71.8%) were followed for two years. Short Form-36 (SF-36), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Lower-Extremity Activity Scale (LEAS) scores were collected at baseline and every six months for two years postoperatively. A piecewise general linear mixed model, which models correlation between repeated measures and estimates separate slopes for different follow-up time periods, was employed to examine functional improvement patterns.

Results: Separate regression slopes were estimated for the zero to twelve-month and the twelve to twenty-four-month periods. The slopes for zero to twelve months showed significant improvement in all measures in the first year. The slopes for twelve to twenty-four months showed deterioration in the scores of the WOMAC pain subscale (slope = 0.67 ± 0.21, p < 0.01) and function subscale (slope = 1.66 ± 0.63, p < 0.05), whereas the slopes of the other measures had plateaued. A higher number of comorbidities was consistently the strongest deterrent of functional improvement across measures. The modes of failure of the primary total knee arthroplasty were instrument-specific predictors of outcome (for example, tibial bone lysis affected only the SF-36 physical component score [coefficient = –5.46 ± 1.91, p < 0.01], while malalignment affected both the SF-36 physical component score [coefficient = 5.41 ± 2.35, p < 0.05] and the LEAS score [coefficient = 1.42 ± 0.69, p < 0.05]). Factors related to the surgical technique did not predict outcomes.

Conclusions: The onset of worsening pain and knee-specific function in the second year following revision total knee arthroplasty indicates the need to closely monitor patients, irrespective of the mode of failure of the primary procedure or the surgical technique for the revision. This information may be especially important for patients with multiple comorbidities.

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

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