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 mid-term 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
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 mid-term 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.