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Rehabilitation Practice and Science

Translated Title

以超音波診斷人工膝關節之聚乙烯鬆落體：病例報告

Abstract

Polyethylene is an important component of a knee prosthesis, but wear of this material is one of the most frequent complications following total knee arthroplasty. Diagnosis of polyethylene wear is based mainly on history, physical examination, and plain radiographs. However, even when the damage is severe, plain radiographs may not be so sensitive enough to detect the debris. Musculoskeletal ultrasound is infrequently used to evaluate the operated knee, but it is a sensitive method for evaluating the polyethylene component of a knee prosthesis.We report an 80-year-old woman who had a painful, enlarging, inflamed mass on her left knee. She had undergone bilateral knee arthroplasty 15 years previously. She was initially treated with oral antibiotics, but without improvement. The knee joint was aspirated, but bacterial cultures had no growth. Laboratory data were unremarkable except for slightly elevated CRP and ESR. Plain radiographs were unrevealing. The MRI images showed a large lobulated heterogenous cystic lesion with artifacts caused by the metallic prosthesis. The MRI appearance of this cystic lesion was suggestive of pigmented villonodular synovitis or septic bursitis, but those diagnoses were not consistent with the clinical and laboratory findings. Musculoskeletal sonography showed large fluid accumulation with proliferation of the synovium and hyperemia of the left lateral knee. There was also an 8 × 2 mm hyperechoic linear loose body around the proliferating synovium, leading to a diagnosis of polyethyelene debris. Symptoms improved after debridement together with surgical removal of the mass. The patient reported no further pain and complete freedom of movement. The pathology report confirmed the presence of polyethylene debris surrounded by giant cells and granulation tissue. In this case, MRI and laboratory data failed to generate an accurate preoperative diagnosis, but musculoskeletal ultrasound allowed accurate identification of the loose body. Musculoskeletal ultrasound is therefore recommended as a tool to evaluate polyethylene wear after total knee replacement.

Language

Traditional Chinese

First Page

55

Last Page

61

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