Mid-Term Outcomes of Metal-Backed Unicompartmental Knee Arthroplasty Show Superiority to All-Polyethylene Unicompartmental and Total Knee Arthroplasty

• Published in: HSS journal 2017-10, Vol.13 (3), p.232-240
• Main Authors: van der List, Jelle P., Kleeblad, Laura J., Zuiderbaan, Hendrik A., Pearle, Andrew D.
• Format: Article
• Language: English
• Subjects: Anesthesiology; Biomechanics; Imaging; Joint surgery; Medicine; Medicine & Public Health; Original; Original Article; Orthopedics; Polyethylene; Radiology; Rheumatology; Sports Medicine; Studies; Surgical Orthopedics
• ISSN: 1556-3316; 1556-3324
• DOI: 10.1007/s11420-017-9557-5

Background Two commonly used tibial designs for unicompartmental knee arthroplasty (UKA) are all-polyethylene “inlay” and metal-backed “onlay” components. Biomechanical studies showed that the metal baseplate in onlay designs better distributes forces over the tibia but studies failed to show differences in functional outcomes between both designs at mid-term follow-up. Furthermore, no studies have compared both designs with total knee arthroplasty (TKA). Questions/Purposes The goal of this study was to compare outcomes of inlay UKA and onlay UKA at mid-term follow-up and compare these with TKA outcomes. Methods In this retrospective study, 52 patients undergoing inlay medial UKA, 59 patients undergoing onlay medial UKA, and 59 patients undergoing TKA were included. Western Ontario and McMaster Universities Arthritis Index scores were collected preoperatively and at mean 5.1-year follow-up (range 4.0–7.0 years). Results Preoperatively, no differences were observed in patient characteristics or outcome scores. At mid-term follow-up, patients undergoing onlay medial UKA reported significant better functional outcomes than those of inlay medial UKA (92.0 ± 10.4 vs. 82.4 ± 18.7, p = 0.010) and when compared to TKA (92.0 ± 10.4 vs. 79.6 ± 18.5, p