To determine the classification scheme for osteoarthritis severity grading that most closely correlates with postoperative clinical outcomes and to identify the positive and negative prognostic factors for medial open-wedge high-tibial osteotomy (OWHTO).
Seventy-nine consecutive patients with primary varus osteoarthritis were treated using OWHTO. Arthritic grading was determined by arthroscopic assessment according to the modified Outerbridge classification and by radiographic classification according to the Kellgren-Lawrence (KL) grading scale on standing anteroposterior (AP) and 45° posteroanterior (PA) flexion weight-bearing radiography. Clinical outcome was assessed using the Oxford Knee Score (OKS), which was evaluated both preoperatively and at the postoperative 2-year follow-up after OWHTO. Multivariate regression analyses were used to explore and quantify the influence of baseline patient demographics, variables related to arthroscopic and radiological grades of arthritis, as well as postoperative alignment changes on the OKS.
At the 2-year follow-up, the mean OKS had improved from 20 ± 4 to 39 ± 5 points (p < 0.001). The average mechanical femorotibial and mechanical medial proximal tibial angle (MPTA) changed from 6.9° ± 3.4° to valgus 2.7° ± 2.8° and from 85.6° ± 2.4° to 92.9° ± 3.7° (all p < 0.001). The osteoarthritis severity grade based on the KL scale was 2.4 ± 0.9 on standing AP radiography, 2.8 ± 0.9 on 45° PA flexion weight-bearing radiography (p = 0.003), and 3.4 ± 0.7 according to the modified Outerbridge classification. In the multivariate analyses, the KL grade on 45° PA flexion weight-bearing radiography (p = 0.01) and postoperative MPTA (p = 0.01) showed significant negative correlations with postoperative OKS at the 2-year follow-up.
IV.
The KL grading system based on 45° PA flexion weight-bearing radiography showed the strongest significant negative correlation with postoperative OKS after the OWHTO procedure using three different common OA classification schemes, which should be considered to determine the surgical indication of HTO. The KL grading system based on 45° PA flexion weight-bearing radiography showed the strongest correlation with high-tibial osteotomy-surgical indications and the counselling of patients with advanced osteoarthritis.