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IntroductionSeveral cases of tibial post breakage are reported in the literature. To the best of our knowledge, only three cases of NexGen knee prosthesis (Zimmer, Warsaw, Indiana, USA) tibial post failure have been reported.Case presentationIn November 1999, a 63-year-old Caucasian woman from Italy with a history of symptomatic left knee osteoarthritis underwent a total knee arthroplasty. In March 2008, while rising from a chair, she felt a sudden pain and instability in her left knee. She reported a fracture of the polyethylene post of the tibial insert. No malposition or malalignment of either the femoral or tibial components were identified. The polyethylene tibial insert was studied under light microscopy and scanning electron microscopy. The fracture was also noted to have occurred without any notable polyethylene wear.ConclusionScanning electron microscopy revealed two different damage patterns that could be explained with a two-stage rupture of our patient's polyethylene post. This could have been caused by a non-optimal ligamentous balancing during first implant surgery. Her knee probably developed a varus instability that weakened the post, and then a posterior anterior stress finally broke the polyethylene.

Background: Sever's disease is a common cause of pain in growing kids. Many papers reported in the literature discuss this pathologic condition, but no consensus regarding its etiology has been found among researchers. The aim of the present study was to describe the epidemiologic profile and associated factors of 430 athletic children in a population-based sample of soccer (29.5%), basketball (48.1%), and volleyball (22.3%) players aged 6 to 14 years. Methods: Every athlete was evaluated through physical examination, the Foot Posture Index (FPI), the Oxford Ankle Foot Questionnaire, and a custom-made sports questionnaire. Results: These data show that body mass index, sex, terrain type, sports discipline, and FPI should not be considered as risk factors for calcaneal apophysitis, whereas a significantly higher risk has been found in younger individuals (P < .01), in those with fewer training sessions per week (P = .02), and in those with shorter training sessions (P < .01). Conclusions: The prevalence of Sever's disease in the athletic children evaluated in the present study was higher in younger and less active patients, whereas no differences were registered by sex, FPI, body mass index, terrain type, or sports discipline.