Essential Surgical Techniques
Lateral Unicompartmental Knee Arthroplasty Through a Medial Approach
Surgical Technique
Alexander P. Sah, MD; Richard D. Scott, MD


BACKGROUND: Unicompartmental knee arthroplasty of the medial compartment has excellent long-term clinical outcomes. Arthritis isolated to the lateral compartment is much less common; subsequently, the clinical outcomes of the treatment of that condition are less frequently reported. Most commonly, the lateral compartment is approached through a lateral arthrotomy. The purpose of this study was to determine the midterm results of lateral unicondylar replacement through a medial arthrotomy in patients with primary osteoarthritis or posttraumatic arthritis.

METHODS: From 1991 to 2004, forty-nine lateral unicompartmental knee arthroplasties were performed in forty-five patients by a single surgeon. One patient was excluded from the study because of a severe underlying neurologic condition. Lateral unicompartmental replacement was performed in thirty-eight knees with primary osteoarthritis and in ten knees with posttraumatic arthritis secondary to a tibial plateau fracture. Retrospective chart reviews and radiographic evaluations were performed, and Knee Society scores were determined.

RESULTS: The average Knee Society knee and function scores improved from 39 and 45 points, respectively, preoperatively to 89 and 80 points at an average of 5.2 years postoperatively. Preoperative alignment averaged 10° of valgus, which was corrected to an average of 6.2° of valgus postoperatively. There were no revisions and no notable soft-tissue complications. The mean postoperative knee and function scores were significantly better for patients with primary osteoarthritis (95 and 86 points, respectively) than they were for those with posttraumatic arthritis (74 and 65 points).

CONCLUSIONS: Lateral unicompartmental knee replacement through a medial approach provided durable and reliable short to midterm results. This approach is safe, effective, and extensile, making it a viable alternative to a lateral approach. The outcomes of lateral unicompartmental replacement in patients with posttraumatic arthritis can be expected to be inferior to those in patients with primary osteoarthritis.

LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

ORIGINAL ABSTRACT CITATION: “Lateral Unicompartmental Knee Arthroplasty Through a Medial Approach. Study with an Average Five-Year Follow-up” (2007;89:1948-54).


  • The original scientific article in which the surgical technique was presented was published in JBJS Vol. 89-A, pp. 1948-54, September 2007

  • DISCLOSURE: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. One or more of the authors, or a member of his or her immediate family, received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from a commercial entity (DePuy Inc.). Also, a commercial entity (DePuy Inc.) paid or directed in any one year, or agreed to pay or direct, benefits in excess of $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.

  • A video supplement to this article will be available from the Video Journal of Orthopaedics. A video clip will be available at the JBJS web site, The Video Journal of Orthopaedics can be contacted at (805) 962-3410, web site:

  • The line drawings in this article are the work of Joanne Haderer Müller of Haderer & Müller (biomedart{at}

  • Investigation performed at the Department of Orthopedic Surgery, Brigham and Women's Hospital, Boston, Massachusetts

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