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Why Do Medial Unicompartmental Knee Arthroplasties Fail Today?
Jelle P van der List1, Hendrik A Zuiderbaan1, Andrew D Pearle1
1Department of Orthopaedic Surgery, Sports Medicine and Shoulder Service, Hospital for Special Surgery, Weill Medical College of Cornell University, New York, New York.
The Journal of Arthroplasty
|January 4, 2016
Summary
Medial unicompartmental knee arthroplasty (UKA) has higher failure rates. Aseptic loosening and osteoarthritis progression are the main failure modes, varying by implant type and time to failure.
Area of Science:
- Orthopedic Surgery
- Biomaterials Science
- Clinical Epidemiology
Background:
- Medial unicompartmental knee arthroplasty (UKA) exhibits higher failure rates compared to total knee arthroplasty.
- Understanding the specific failure modes of medial UKA is crucial for improving patient outcomes and implant longevity.
- Existing individual studies often lack the statistical power to definitively identify prevalent failure mechanisms.
Purpose of the Study:
- To systematically review and identify the primary failure modes of medial unicompartmental knee arthroplasty (UKA).
- To compare failure modes across different study types (cohort vs. registry-based), time intervals (early, midterm, late), and implant designs (fixed-bearing vs. mobile-bearing).
Main Methods:
- A systematic review was conducted, searching PubMed, EMBASE, and Cochrane databases, along with annual registries.
- Studies reporting over 25 failures or detailing early (<5 years), midterm (5-10 years), or late (>10 years) failures were included.
- Data from 37 cohort studies and 2 registry-based studies, encompassing 3967 overall failures, were analyzed.
Main Results:
- Aseptic loosening (36%) and osteoarthritis (OA) progression (20%) were the most frequent failure modes in medial UKA.
- Aseptic loosening was the predominant early failure mode (26%), while OA progression dominated midterm (38%) and late failures (40%).
- Fixed-bearing implants showed higher rates of polyethylene wear (12%) and instability (12%), whereas mobile-bearing implants were associated with more pain (14%) and bearing dislocation (11%).
Conclusions:
- Aseptic loosening and osteoarthritis progression are the principal modes of failure for medial unicompartmental knee arthroplasty.
- Aseptic loosening is a key failure mode in early cases and with mobile-bearing designs, whereas OA progression is more common in later failures and with fixed-bearing implants.
