• Jun Wang, Miao Zhang, Yun Xu, XiaoJing Li, CongCong Wang, XiaoPeng Gao, Meng Xu, XiaoPeng Li, Wei Li, YiMin Zhang, GuoWei Wang, and XueJun Cao.
• Department of Joint Surgery, Weifang People's Hospital.
• Medicine (Baltimore). 2020 May 29; 99 (22): e20468.

RationaleAlthough prosthetic loosening caused by poor prosthesis positioning is common after total hip arthroplasty (THA), an inflammation caused by poor prosthesis positioning is rare. We report a case in which a THA-related inflammation was indeed caused by poor prosthesis positioning.Patient ConcernsA 64-year-old woman was admitted to our hospital with a history of persistent hip pain that had started after she had undergone THA 4 years previously. In addition, she complained of swelling of the hip that had begun 2 months ago.DiagnosisHer pain and swelling was initially thought to be caused by an infection, but was eventually diagnosed as inflammation caused by prosthesis loosening, that was in line with finding that her preoperative and intraoperative cultures showed no bacterial or fungal growth. This case posed many questions and difficulties during the diagnostic and treatment stages.InterventionsRoutine diagnosis of periprosthetic suspected infection includes blood test, erythrocyte sedimentation rate, C-reactive protein level, bacterial and fungal cultures, and pathology examinations, which were performed. Finally, this case was eventually diagnosed as inflammation, the prosthesis was removed and antibiotics administered. It was replaced 6 months later.OutcomesExcept for the erythrocyte sedimentation rate and C-reactive protein levels, X rays, routine blood tests, bacterial and fungal cultures (3 times), and other tests were within the normal range. Positive pathological examinations of synovium during and after the operation indicated chronic inflammation and eliminated inflammation in other areas. Postoperative effect of the second-stage THA was good, with the patient highly satisfied after 6 months.LessonsThe operative method and position of a joint prosthesis are extremely important. A poorly positioned prosthesis worsens with wear. Wear particles then lead to long-term localized aseptic inflammation with swelling and fever and eventually to low-virulence infection. Prosthetic loosening may be found even at long-term follow-up evaluations after THA in patients with a poorly positioned prosthesis, eventually leading to the need for revision. We had 2 questions: should early revision be considered when a prosthesis had not been properly positioned? In the absence of any confirmation of infection, should a patient suspected of having a periprosthetic infection be treated as early as possible?

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