Patient, Implant, and Alignment Factors Associated With Revision of Medial Compartment Unicondylar Arthroplasty

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Abstract

The investigators reviewed 245 fixed-bearing unicondylar arthroplasties that one surgeon performed as treatment of medial compartment osteoarthritis between 1988 and 1997 using a variety of cemented metal-backed tibial components and gamma-irradiated-in-air polyethylene bearings. Multivariate statistical analysis was used to evaluate how the event of revision was influenced by 3 patient factors, 3 implant factors, and 7 factors assessed from preoperative and early postoperative radiographs. Five factors were statistically associated with revision: (younger) patient age, (thinner) tibial component initial thickness, (longer) polyethylene shelf age, (lesser) angular reduction of medial tibial plateau varus, and (more varus) postoperative hip-knee-ankle angle. Besides illustrating deleterious consequences of using gamma-irradiated-in-air polyethylene in medial unicompartmental arthroplasty, our results support reducing varus angulation of the medial tibial plateau and knee at surgery.

Section snippets

Methods

From a population of 295 unicondylar arthroplasties performed by one surgeon (author 5) as a primary reconstructive procedure for medial tibiofemoral compartment osteoarthritis between 1988 and 1997, we reviewed 245 knees that had received a fixed-bearing, metal-backed tibial component and a polyethylene bearing sterilized with gamma radiation in air. Seven designs from 4 manufacturers had been used: Robert Brigham (Johnson and Johnson Orthopaedics, Raynham, Mass) 2, 10, 11, 15, Single

Results

In this single-surgeon series of cemented metal-backed tibial components with gamma-irradiated-in-air polyethylene, 5 factors were significantly associated with revision (each P < .05 per Cox proportional hazards regression, Table 2): (younger) patient age at arthroplasty, (thinner) initial tibial component thickness, (longer) polyethylene insert shelf age, (lesser) operative reduction of the varus angle of the tibial plateau, and (increasing varus of the) postoperative hip-knee-ankle angle.

Discussion

Patient factors examined in our study included age, sex, and weight. In 2001, Robertson et al [3] reported on 12 282 unicondylar arthroplasties that were performed for osteoarthritis between 1988 and 1997 and entered into the Swedish Knee Arthroplasty Registry. Cox proportional hazards regression showed that younger patient age at surgery was statistically associated with revision, whereas patient sex was not. This was also true in our study, which is similar in that it too featured

Acknowledgment

The investigators appreciate the assistance of the manufacturers in tracing product sterilization histories.

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  • Cited by (0)

    Benefits or funds were received in partial or total support of the research material described in this article. Institutional research financial support has been received from Inova Health Systems (Falls Church, Va). Gerard A. Engh and James P. McAuley have received product royalties related to a contemporary unicondylar knee design from DePuy, a Johnson and Johnson Company (Warsaw, Ind).

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