The clinical outcomes of cementless unicompartmental knee replacement in patients with reduced bone mineral density

Andrew Judge,Christopher A Dodd,James A Kennedy,Hasan R Mohammad,Stephen J Mellon,David W Murray

doi:10.1186/s13018-020-1566-2

Abstract

BackgroundOsteoporosis and osteopenia are conditions characterised by reduced bone mineral density (BMD). There is concern that bone with reduced BMD may not provide sufficient fixation for cementless components which primarily rely on the quality of surrounding bone. The aim of our study was to report the midterm clinical outcomes of patients with reduced BMD undergoing cementless unicompartmental knee replacements (UKR). Our hypothesis was that there would be no difference in outcome between patients with normal bone and those with reduced BMD.MethodsFrom a prospective cohort of 70 patients undergoing cementless UKR surgery, patients were categorised into normal (n = 20), osteopenic (n = 38) and osteoporotic groups (n = 12) based on their central dual-energy X-ray absorptiometry (DEXA) scans according to the World Health Organization criteria. Patients were followed up by independent research physiotherapists and outcome scores; Oxford Knee Score (OKS), Tegner score, American Knee Society Score Functional (AKSS-F) and Objective (AKSS-O) were recorded preoperatively and at a mean of 4 years postoperatively. The prevalence of reoperations, revisions and mortality was also recorded at a mean of 5 years postoperatively.ResultsThere were no significant differences in the midterm postoperative OKS (P = 0.83), Tegner score (P = 0.17) and AKSS-O (P = 0.67). However, the AKSS-F was significantly higher (P = 0.04) in normal (90, IQR 37.5) compared to osteoporotic (65, IQR 35) groups. There were no significant differences (P = 0.82) between normal and osteopenic bone (80, IQR 35). The revision prevalence was 5%, 2.6% and 0% in the normal, osteopenic and osteoporotic groups respectively. The reoperation prevalence was 5%, 7.9% and 0% respectively. There were no deaths in any group related to the implant.ConclusionsWe found that patients with reduced BMD could safely undergo cementless UKR surgery and have similar clinical outcomes to those with normal BMD. However, larger studies with longer follow-up are needed to confirm our findings and ensure that cementless fixation is safe in patients with reduced BMD.

Highlights

Osteoporosis and osteopenia are conditions characterised by reduced bone mineral density (BMD)
Overall results from cohort Seventy medial Oxford unicompartmental knee replacements (UKR) were implanted in 70 patients (60 females and 10 males)
The main finding of the study was that there was no increased revision or reoperation rate or pain following cementless UKR in patients with osteopenia or osteoporosis compared to controls with normal BMD

Summary

Introduction

Osteoporosis and osteopenia are conditions characterised by reduced bone mineral density (BMD). Over 100,000 primary knee replacements are conducted annually in the UK for end-stage osteoarthritis [1] These include total knee replacement (TKR) and unicompartmental knee replacement (UKR), where one compartment is replaced. Osteoporosis and its milder form, osteopenia, are conditions characterised by reduced bone mineral density (BMD) in otherwise normal bones, rendering them more fragile and fracture prone [2]. They are estimated to affect over 200 million people worldwide costing 37 billion euros annually in Europe alone [3, 4]. Current estimates are that approximately 10% of patients undergoing hip or knee replacement surgery have a diagnosis of osteoporosis and up to approximately 30% have evidence of osteopenia [5]

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