Late tibial post fracture following mobile-bearing posterior-stabilized total knee arthroplasty: A case report highlighting the role of malalignment and polyethylene wear

Abstract

Tibial post fracture in mobile-bearing posterior-stabilized total knee arthroplasty (MB-PS TKA) is a rare but clinically significant complication associated with knee instability. A 72-year-old female presented with progressive knee pain and instability eight years after primary MB-PS TKA. Radiographic and clinical evaluation demonstrated varus malalignment and excessive posterior tibial slope. Revision TKA was performed, and intraoperative findings confirmed a fractured polyethylene tibial post with localized wear. Excessive posterior tibial slope may lead to anterior tibial translation and increased cam-post impingement, while varus malalignment results in asymmetric load distribution and accelerated polyethylene wear. Although mobile-bearing designs are intended to reduce stress concentration, these advantages may be negated under conditions of malalignment. Patient-related factors such as elevated body mass index and sustained physical activity may further contribute to implant failure. Proper component alignment and patient-specific risk assessment are essential to prevent tibial post fracture in MB-PS TKA. Clinicians should consider polyethylene-related complications in patients presenting with late instability, even in the absence of a clearly defined traumatic event.

Keywords

• total knee arthroplasty
• posterior-stabilized
• mobile bearing polyethylene
• tibial-post fracture
• instability
• misalignment

Ethical Statement

Ethical approval was not required for this individual case report; however, written informed consent was obtained from the patient for the publication of this case and associated images.

Thanks

We would like to thank the translation support we received from the artificial intelligence model ChatGPT and Deep L while preparing this article.

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