Erosion and Failure of the Tibial Post after Posterior-stabilized Total Knee Replacement: A Case Report.

INTRODUCTION: Posterior-stabilized (PS) total knee arthroplasty (TKA) prostheses are characterized by an articulation between the polyethylene tibial post and the cam of the femoral component. Tibial post-fractures, traumatic and non-traumatic, are uncommon but catastrophic complications. We report a rare and unusual case of complete atraumatic erosion of the tibial post after PS-TKA.

CASE REPORT: We present a case of atraumatic tibial post-failure (complete erosion) in a 73-year-old female after primary TKA. The patient presented with chronic pain, effusion, and instability both in the coronal and sagittal plane over a period of 1 year. There were no signs of component loosening on plain radiography, no fractures, and revealed medial extension laxity on valgus stress views. During revision surgery, polyethylene insert retrieval revealed a completely eroded tibial post, without any obvious fracture. There was no fractured tibial post lying freely in the joint cavity. The patient was subsequently revised with a hinged component due to gross bi-planar instability.

CONCLUSION: In a post-TKR (PS knee) patient with chronic pain and instability, one should consider tibial post-complications after ruling out infection. Chronic instability can cause progressive erosion of the tibial post, which can fail without an obvious fracture. Revision surgery with constrained implants may be needed to manage such cases.