The early diagnosis of low-grade Cutibacterium acnes prosthetic shoulder joint infection is challenging due to the lack of clinical and laboratory signs. Patients present with atypical symptoms such as stiffness or failure to improve shoulder function. The diagnosis is often delayed with impact on long-term outcomes. We present the case of an 82-year-old man with a surgical site erythema occurring 7 weeks after reverse shoulder arthroplasty associated with a light raise of C reactive protein (20 mg/L). At 9 weeks, radiographs revealed a ‘periosteal spur sign’ (humeral calcar) and localised adjacent osteolysis. Open surgery showed morphological signs of infection confirmed by growth of C. acnes in eight cultures. A ‘periosteal spur sign’ is a useful early radiographic indicator of low-grade prosthetic joint infection usually occurring with some delay after clinical symptoms. A high clinical index of suspicion is needed to proceed with biopsies and to initiate combined operative and antibacterial treatment.
- orthopaedic and trauma surgery
- bone and joint infections
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Contributors SB and BD planned and wrote the manuscript. AT and OM reviewed the manuscript and gave advice on antibiotic therapy during the treatment. SB identified and managed the case and is the guarantor.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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