Advantages and limitations of mobile-bearing unicompartmental knee arthroplasty: an overview of the literature

ABSTRACT

Introduction

Interest in unicompartmental knee arthroplasty (UKA) has recently grown. Mobile bearing UKA, in which the bearing is not fixed but rather perfectly conforms with femoral and tibial components and moves completely passively between the femoral and tibial implant, has now been used for approximately half a century.

Areas Covered

Alongside the recognized advantages of UKA, the mobile-bearing variant benefits from an extremely low rate of polyethylene wear and tolerable minor malalignment. Revision rates for UKA have been reported to exceed those of total knee arthroplasty, but long-term survival rates and outcomes from mobile-bearing UKA have been found to be satisfactory. In addition to the lateral osteoarthritis and loosening, which are main complications of UKA, bearing dislocation is a specific complication of mobile bearing UKA. Fractures and valgus subsidence are more prevalent than in the cementless UKA. While these continue to be features to be addressed, they have been partially solved.

Expert Opinion

Given the manifold benefits of UKA, its application could be extended to a larger patient population. Successful outcomes rely on careful patient selection and the surgeon’s extensive familiarity with the procedure. Looking ahead, the incorporation of robotic surgery, already a feature of some fixed-bearing UKAs, might shape the future trajectory of mobile-bearing UKA.

KEYWORDS:

• Knee
• surgery
• arthroplasty
• unicompartmental
• mobile-bearing
• outcome
• complication
• robotics

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Article highlights

• Oxford mobile bearing UKA is characterized as fully-congruent and non-constrained articulation aiming for the patient’s pre-disease alignment based on soft-tissue balancing.

• Operative procedures are performed using Microplasty instrumentation for precise bone cuts and an incremental milling system to adjust flexion and extension gaps.

• Although higher revision rates have been reported, with proper patient selection and good surgeon familiarity, the rate of revision can be decreased, and good long-term results have been reported.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewers Disclosure

Peer reviewers on this manuscript have no relevant financial relationships or otherwise to disclose.

Additional information

Funding

^{This paper was not funded.}