Summary

Osteoarthritic knees with pre-operative recurvatum undergoing total knee arthroplasty with cruciate-retaining and posterior-stabilized implants do not differ in clinical or functional outcomes, nor revision rates.

Abstract

Introduction

Arthritic knees with genu recurvatum or hyperextension > 5° pose unique challenges during Total knee arthroplasty (TKA). No study has compared the outcomes between these two types of implants. The aim was to compare the clinical outcomes, complications, and revision rates between CR and PS implants in patients with pre-operative recurvatum undergoing TKA for osteoarthritis.

Methods

Prospectively collected registry data of primary total knee arthroplasties carried out by 3 specialist Orthopaedic surgeons between 2000 and 2018 were analysed. These surgeons were selected as they were exclusively either PS or CR surgeons. Clinical assessment pre-operatively, at 6-month and 2-year follow-up was performed, with detailed measurements of start and end range of motion. International Knee Society Score (IKSS); Oxford Knee Score (OKS) and Short Form-36 (SF-36) were collected. Fulfilment of patient’s expectations, satisfaction and complications were recorded. Independent t-test was used for comparison of continuous variables, and chi-square test or Fisher's exact test was used for categorical variables. Institutional Review Board approval was obtained under the local ethics committee.

Results

3960 primary TKAs were performed in total by 3 specialist Orthopaedic surgeons between 2000 and 2018, of which 123 knees (3.1%) had pre-operative recurvatum. Only 109 knees had physiological recurvatum (mean -7.3, range -22 to -5), of which 62 underwent cruciate-retaining TKA and 47 underwent posterior-stabilized TKA. None of the patients required hinged arthroplasty. At baseline, there were no statistically significant differences in preoperative BMI, degree of recurvatum, range of motion, IKSS or OKS scores. At 2-year follow up, both groups demonstrated a recurrence of recurvatum (CR: -2.3 vs PS: -2.2, p=.86). There was no significant difference in range of motion (CR: 119.3 vs PS: 123.4; p= .17) International Knee Score functional scores (CR: 73.9 vs PS: 71.9; p = .59), knee scores (CR: 82.6 vs PS: 81.8; p = .76), improvement in oxford scores (CR: 16.3 vs PS: 17.0; p=.71), improvement of SF-36 physical component scores from baseline (CR: 18.6 vs PS: 15.8; p=.292) between groups. Satisfaction scores were not significantly different (CR: 92.3 vs PS: 90.3; p=.77). However, PS patients continued to show greater end range flexion (CR: 116.4 vs PS: 121.9; p=.05) at 2-year follow up review. 1 prosthetic joint infection occurred in each group, and 1 knee in the PS group required manipulation under anaesthesia for post-operative stiffness. There were no significant differences between both groups in complications and revision rates.

Discussion And Conclusion

There are no significant differences between the measured clinical and functional outcomes of posterior-stabilized and cruciate-retaining TKA in genu recurvatum at 6 month and 2-year review post-operatively. Patients in both groups were able to achieve significant correction of their recurvatum at 6 months and were able to maintain significant correction at 2-years. Although there was slight recurrence of recurvatum seen despite an initial restoration, this did not affect functional outcomes nor satisfaction. There were no differences in revision rates. Surgeons should select the type of implant that they are most comfortable and proficient in using, with adequate attention towards correcting the pre-operative recurvatum.