A mid term comparison of open wedge high tibial osteotomy vs unicompartmental knee arthroplasty for medial compartment osteoarthritis of the knee

Abstract

Background: The choice of surgical treatments for unicompartmental osteoarthritis (OA) of the knee is still somewhat controversial. Midterm results from cases treated using unicompartmental knee arthroplasty (UKA) or open wedge high tibial osteotomy (OWHTO) were evaluated retrospectively.

Methods: Twenty-seven knees of 24 patients with varus deformities underwent OWHTO and 30 knees of 18 patients underwent UKA surgeries for the treatment of medial compartmental osteoarthritis (OA). The KSS score, FTA, range of motion and complications were evaluated before and after surgery.

Results: The preoperative mean KSS scores were 49 points in the OWHTO group and 62 in the UKA group which improved postoperatively to 89 (excellent; 19 knees, good; 8 knees), and 88 (excellent; 25, good; 4, fair; 1), respectively. There was no significant difference between the OWHTO and UKA scores. Seventeen patients in the OWHTO group could sit comfortably in the formal Japanese style after surgery. The preoperative mean FTA values for the OWHTO and UKA groups were 182 degrees and 184, and at follow-up measured 169 and 170, respectively. In the UKA group, the femoral component and the polyethylene insertion in one patient was exchanged at 5 years post-surgery and revision TKAs were performed in 2 cases. In the OWHTO group, one tibial plateau fracture and one subcutaneous tissue infection were noted.

Conclusions: Treatment options should be carefully considered for each OA patient in accordance with their activity levels, grade of advanced OA, age, and range of motion of the knee. OWHTO shows an improved indication for active patients with a good range of motion of the knee.

Figure 1

Compartment Unicompartment-Knee. Image of a titanium implant (Nakashima Propeller Co, Okayama, Japan). The tibial component was implanted first with or without bone cement and then firmly fixed with two screws. The femoral side is designed for surface replacement and is fixed with bone cement.

Figure 2

A revision UKA case involving a 70-year-old man. A. A medial compartmental grade 4 OA prior to UKA, B. Anterior subluxation of the tibia. Rapid wearing of the polyethylene insertion was caused by antero-posterior instability of the knee. Although a partial anterior cruciate ligament tear was observed, UKA was still recommended and performed as the initial surgery. C. A TKA performed two years after UKA.

Figure 3

Japanese sitting style. Although none of the patients included in this study could sit in a Japanese style before OWHTO, 17 of the 24 patients in this group (71%) could sit comfortably in the formal Japanese style after surgery. This is an important outcome that has only been achieved thus far using OWHTO.

Figure 4

70-year-old woman in the OWHTO group. A. Prior to OWHTO, a medial compartmental grade 2 OA was diagnosed. The FTA was 182° and the KSS was 60. B. Two weeks after OWHTO, the FTA was corrected to 170°. C. Two years and 6 months after OWHTO, the FTA was maintained at 170° and there was no correction loss. This patient could subsequently sit with full flexion and the KSS improved to the excellent range.