Tibial Post Fracture in a Posterior-Stabilized Knee Prosthesis: A Case Report and Review of the Literature.
César Abraham Ávila Lozano, César Alejandro Jiménez-Aroche, Jacobo Kerbel Sutton et al.
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Case in brief
A 92-year-old man developed acute mechanical knee pain, recurrent clicking, and subjective instability 16 years after a previously well-functioning posterior-stabilized total knee arthroplasty, following a low-energy flexion-rotation movement. Plain radiographs showed no fracture, loosening, or implant failure. Dynamic fluoroscopy reproduced his symptoms and showed abnormal anterior femoral translation during flexion, suggesting cam-post failure. Surgery confirmed a fractured polyethylene tibial post with chronic wear at its base; the metal components were well fixed and not grossly malpositioned. Isolated exchange for a thicker polyethylene insert restored stability. At 4.5 months, mechanical symptoms had resolved and knee stability was preserved.
What made this case unusual
Despite unrevealing conventional radiographs, symptom-reproducing dynamic fluoroscopy demonstrated abnormal femoral translation and raised suspicion of tibial post fracture before surgery.
Diagnostic / clinical pearl
In a symptomatic late posterior-stabilized knee arthroplasty with inconclusive radiographs, dynamic fluoroscopy may reveal abnormal motion suggestive of cam-post failure; operative confirmation is important.
Why it matters
Isolated polyethylene insert exchange was effective in this patient after confirming that component fixation, alignment, and overall stability were preserved.