Elsevier

The Journal of Arthroplasty

Volume 24, Issue 8, December 2009, Pages 1292.e5-1292.e9
The Journal of Arthroplasty

Case Report
Early Nontraumatic Fracture of the Polyethylene Tibial Post in a NexGen LPS-Flex Posterior Stabilized Knee Prosthesis

https://doi.org/10.1016/j.arth.2009.02.013Get rights and content

Abstract

Fracture of a polyethylene tibial post in a knee prosthesis after a total knee arthroplasty (TKA) is an uncommon but severe complication of polyethylene tibial post wear. A fractured tibial post results in an unstable and malfunctioning knee. Revision knee surgery is necessary to restore function of the affected knee. We report a case of a nontraumatic fracture of a tibial polyethylene post that occurred in a 63-year-old man with left-sided hemiparesis 3 years after he had undergone left TKA with a NexGen LPS-Flex total knee prosthesis. To our knowledge, this is the first report of a nontraumatic fracture to the tibial post with anterolateral to posterior breakage after a NexGen LPS-Flex TKA.

Section snippets

Case Report

A 63-year-old man (height, 167 cm; body mass index, 27.8) with a history of cerebral infarction, which resulted in left-sided hemiparesis and circumducting gait at the age of 56 years, presented with left knee instability. Three years before this presentation, he had undergone left TKA with a NexGen LPS-Flex TKA.

The index primary knee arthroplasty had been performed for the treatment of an advanced left arthritic knee. A standard midline incision with midvastus arthrotomy was used to implant a

Discussion

Posterior stabilized total knee prostheses often lead to magnificent clinical results. The cam-and-post mechanism reproduces the physiologic femoral rollback during knee flexion. Moreover, the femoral cam and tibial polyethylene post can act as a mechanical stop to limit posterior displacement of the tibia relative to the femur. However, it has to be noted that the failure of this mechanism always leads to abnormal knee kinematics and instability 1, 2, 3, 4, 5. Anterior and posterior tibial

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  • Catastrophic Failures of the Tibial Post in a Bicruciate Substituting Total Knee Prosthesis

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    Few cases of tibial post breakage in PS TKA have previously been reported. To our knowledge, 5 previous cases have been reported in the NexGen prosthesis (Zimmer, Warsaw, IN) [4,19–24]. Chiu et al. described a case of atraumatic tibial post fracture 3 years after TKA [19].

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    The cam and post mechanism is also a potential source of polyethylene wear and fatigue failure, being a mechanical articulation under stress. Breakage via fatigue failure of this mechanism has been observed (Fig. 1) and reported in multiple PS bearing designs [3, 4]. Dislocation also may occur in PS design knees, usually posteriorly but occasionally anteriorly [5].

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No benefits or funds were received in support of the study.

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