Are the functional outcomes really inferior following unicondylar knee arthroplasty in patients with partial-thickness cartilage loss?

The effect of Kellgren-Lawrence grade on functional outcome following medial unicompartmental knee arthroplasty in patients with partial thickness cartilage loss

INTRODUCTION

Medial unicompartmental knee arthroplasty (mUKA) is indicated for anteromedial osteoarthritis (AMOA) with medial full thickness cartilage loss (FTCL). Previous studies have reported controversial outcomes in patients with partial thickness cartilage loss (PTCL) who undergo mUKA. However, there is no reliable way to predict which PTCL patients do well. The aim of the present study was to investigate whether Kellgren-Lawrence (KL) grade is associated with clinical outcomes following mUKA patients with PTCL.

MATERIALS AND METHODS

Cartilage loss in the medial compartment was evaluated via MRI and intra-operatively according to the International Cartilage Repair Society (ICRS) classification system. Standing anteroposterior and lateral radiographs were taken to determine the KL grade. The patients, were grouped as having FTCL or PTCL with KL 0-2 and KL 3. The clinical data from the latest follow-up were assessed via the Forgotten Joint Score (FJS-12 score), the Oxford Knee Score (OKS), and the Knee Injury and Osteoarthritis Outcome Score (KOOS). Postoperative complications were also observed and recorded.

RESULTS

We studied 40 knees of 39 patients with PTCL and matched them with 40 knees with FTCL for mUKAs. The groups were similar in terms of age, sex, operative side, BMI and follow-up. The mean OKS (P = 0.014), KOOS pain (P = 0.040), KOOS symptom (P = 0.028), and KOOS sport (P = 0.034) scores were significantly lower in the PTCL group than in the FTCL group. To evaluate the effect of the KL grade, patients were categorized into the following groups: FTCL, PTCL with KL 0-2 and KL 3. The mean OKS (P = 0.044), KOOS symptom (P = 0.047) and KOOS sport (P = 0.045) scores were significantly lower in the PTCL with KL 0-2 group. However, no significant difference was found between the FTCL and PTCL with KL 3 in terms of the FJS-12, OKS and KOOS scores. No patients had any complications requiring reoperation or surgical revision.

CONCLUSIONS

PTCL patients who have KL 3 AMOA are not contraindicated by mUKA when nonoperative treatment for those patients have otherwise failed. However, PTCL patients with KL 0-2 AMOA are not equally suited for treatment with mUKA, and other treatment options should be considered.