ISAKOS: 2019 Congress in Cancun, Mexico
ISAKOS

2019 ISAKOS Biennial Congress Paper #198

 

The Influence of Patellofemoral Degenerative Changes on the Outcome of Unicompartmental Knee Replacement

Turlough O'Donnell, MD, FRCSI, FRCS(Orth), FFSEM, Clonskeagh, Dublin IRELAND
University College Dublin School of Medicine, Dublin, Dublin, IRELAND

FDA Status Cleared

Summary

Asymptomatic patellofemoral disease is not a contraindication to UKR for medial compartment osteoarthritis of the knee, and is associated with similar outcomes to unicompartmental knee replacement in those with a normal patellofemoral joint at minimum 6-year follow-up, provided alignment has not been excessively corrected.

Abstract

Introduction

Unicompartmental knee replacement (UKR) is an effective treatment for medial compartment osteoarthritis of the knee. Patellofemoral joint (PFJ) degeneration is considered to be a relative contraindication.

The purpose of this study was to evaluate whether asymptomatic osteoarthritis of the PFJ was associated with inferior outcome when performing UKR for medial compartment osteoarthritis.

Methods

We prospectively collected data on 300 consecutive cases who underwent UKR between July 2010 and June 2013 in our institution.

All operations were performed by a single surgeon, fellowship-trained in knee preservation arthroplasty.

The status of the PF joint was assessed pre-operatively by clinical examination and radiologically with radiographs and MR imaging, and intra-operatively by direct inspection. Patients were divided into two groups, one group with a normal PFJ (Outerbridge changes < 3) (Group 1), and the second group with degenerative changes of the PFJ (Group 2).

The usual demographic information was recorded, and WOMAC and Knee Society Score (KSS) were measured pre-operatively and sequentially thereafter. Hip-Knee-Ankle radiographs and skyline PFJ views were assessed pre-and post-operatively.

Failure was defined as revision of the implant for progression of disease.

Statistical analysis was performed using SPSS.

Results

There were 152 men and 130 women in the study. 18 patients underwent bilateral surgery, giving a total of 300 cases.

There was no significant difference between the 2 groups regarding demographic data at the time of surgery. The average age of the patients at the time of surgery was 63 years (range: 41–87 years). The mean follow-up was 6.5 years (Range: 5-8 years). Data was collected on all patients up to 8 years, and 35 patients were subsequently lost to follow-up through death or other factors. This left a total of 265 patients available for review at final follow-up. There were 171 cases in group 1 and 94 cases in group 2.



There were no significant differences in terms of functional outcome (p>0.1) or range of motion (p>0.1) between the two groups.

The average HKA axis improved from -60 (Range:-100 – 50) to -1.70 (Range:-50 – 70) in group A, and from -5.70 (Range:-90 - 20) to -1.50 (Range: -3.50 – 90) in group B (p>0.1).

There were 3 revisions (1.8%) for progression of disease in group 1, and 2 revisions (2.1%) in group 2 (p>0.1). Only 1 of these, a patient in group 2, was for progression of disease in the PFJ. Of the 5 revisions, 2 were revised to a TKR, 1 underwent revision by way of supplementary patellofemoral arthroplasty, and the remaining 2 underwent supplementary lateral UKR resulting in bicompartmental UKR.

All 5 revision cases had a HKA angle in excessive valgus post-operatively (p<0.01).

Conclusion

Asymptomatic PFJ disease is not a contraindication to UKR for medial compartment osteoarthritis of the knee, and is associated with similar outcomes to UKR in those with a normal PFJ at minimum 6-year follow-up. Excessive valgus malalignment is associated with a higher revision rate in both groups.