Background

Partial knee arthroplasty (PKA) is now accepted by an increasing number of surgeons as the treatment of choice for severe medial osteoarthritis. PKA can achieve superior functional outcomes with reduced surgical risk compared to total knee arthroplasty (TKA) with revision rates for the best performing fixed-bearing implants approaching those of TKA. Some surgeons exclude elderly patients from PKA, believing that TKA may be more reliable given historical concerns over revision rates. Similarly, many exclude young, active patients despite many studies demonstrating disappointing satisfaction and clinical outcomes following TKA in this age group. As a unit we offer fixed-bearing PKA to all age groups with severe osteoarthritis. This study (part supported by The European Knee Society) prospectively assessed clinical outcomes from a large consecutive series of fixed-bearing medial PKA with broad selection criteria.

Objectives
The aims of the study were to assess clinical outcomes following isolated fixed-bearing partial knee arthroplasty in patients of all arthroplasty ages and to compare results and satisfaction from young (<50yrs) and elderly (>80yrs) patients with those from a more traditional age demographic.

Study Design & Methods
We prospectively studied 240 consecutive, fixed-bearing PKA (Persona Partial Knee, Zimmer Biomet) cases. Broad selection criteria (standard for our unit) included patients with a wide age range including those under 50yrs and over 80yrs. All patients completed pre and postoperative Oxford Knee Score (OKS), KOOS PS, UCLA, Forgotten Joint Score (FJS-12) and patient satisfaction scores at 1 and 2 years. Results from different patient age groups were analysed and compared.

Results

Commencing February 2017, 240 fixed-bearing PKA were performed in 229 consecutive patients. Mean age at time of surgery was 65.8yrs (range 41-89), mean BMI 29.2 (range 20-47). Excellent clinical outcomes were achieved: Mean OKS, KOOS, UCLA and FJS all improved substantially from 24.8, 55.2, 4.8 & 15.2 pre operatively to 43.7, 83, 6.5 & 76.9 at 1 year and 44.8, 84, 6.5 & 82.5 at 2 years. 96.8% were satisfied with their PKA at 2 years. Two patients have required a revision procedure (one tibial loosening and lateral OA respectively) at mean 3 years follow-up.

Satisfaction rates and outcome scores were consistent across all age groups although young (<50yrs) patients demonstrated a significantly larger improvement in their OKS (mean 20.5 pre-op to 44.8 at 2 yrs, p<0.05 - unpaired t-test). Patients aged 80 or over reported the highest FJS-12 (88.1), a significantly greater improvement than all other age groups (p<0.02). Patients in their 70s and 80s achieved only slightly lower UCLA activity (6.0 vs 6.8) than the youngest group.

Conclusions

Excellent functional outcomes are confirmed with fixed-bearing PKA for the treatment of severe medial compartmental arthritis. Patients of all ages demonstrated large improvements in functional scores with no evidence of dissatisfaction in younger patients. High satisfaction and outcome scores in the elderly support PKA as the treatment of choice for these patients. Age should not be a limiting factor when considering offering fixed-bearing partial knee arthroplasty.