Research Article

Elimination of Preoperative Flexion Contracture as a Contraindication for Unicompartmental Knee Arthroplasty

Purcell, Richard L. MD; Cody, John P. MD; Ammeen, Deborah J. BS; Goyal, Nitin MD; Engh, Gerard A. MD

From Anderson Orthopaedic Research Institute, Alexandria, VA.

Correspondence to Ms. Ammeen: [email protected]

Dr. Goyal or an immediate family member serves as a paid consultant to Stryker and Zimmer Biomet. Dr. Engh or an immediate family member has received royalties from Innomed and Smith & Nephew; is a member of a speakers’ bureau or has made paid presentations on behalf of Smith & Nephew and Zimmer Biomet; serves as a paid consultant to Smith & Nephew and Zimmer Biomet; has stock or stock options held in Zimmer Biomet; and has received research or institutional support from DePuy Synthes, Inova Health System, and Smith & Nephew. None of the following authors or any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Purcell, Dr. Cody, and Ms. Ammeen.

Journal of the American Academy of Orthopaedic Surgeons 26(7):p e158-e163, April 1, 2018. | DOI: 10.5435/JAAOS-D-16-00802

Abstract

Introduction:

Unicompartmental knee arthroplasty (UKA) is an effective alternative to total knee arthroplasty (TKA) for the management of unicondylar osteoarthritis. Historical contraindications limit patients’ eligibility for UKA. However, recent reports have suggested that some contraindications may not be absolute. This study evaluates preoperative flexion contracture with regard to UKA.

Methods:

This study was a retrospective review of 53 patients with preoperative flexion contracture between 11° and 20° who underwent fixed-bearing UKA and a matched cohort of 53 patients who underwent cruciate-retaining TKA.

Results:

Preoperatively, the average flexion contracture was 13.8° in the UKA group and 14.1° in the TKA group (P = 0.42). Mean preoperative motion was greater in the patients treated with UKA (106°) than in those treated with TKA (97°; P < 0.001). Postoperatively, patients who underwent UKA had greater motion than patients who underwent TKA had (121° versus 113°; P < 0.01). Residual flexion contracture was greater in the UKA group (4.1°) than in the TKA group (2.1°; P = 0.02). The two groups demonstrated similar improvements in Knee Society clinical scores (P = 0.32). However, patients treated with UKA demonstrated higher Knee Society functional scores, compared with patients treated with TKA (86 versus 75; P = 0.03).

Discussion:

Although residual flexion contracture was worse after UKA, this group had similar clinical improvement, greater postoperative motion, and greater function scores, compared with the matched TKA group. Preoperative flexion contracture >5° may not be an absolute contraindication to UKA.

Conclusion:

The contraindications to UKA regarding flexion contracture may not be as absolute as previously thought. Larger, prospective studies are needed to generalize these findings to a wider population.