Friday, April 1, 2016

Propionibacterium acnes Prosthetic Shoulder Infections - more questions than answers

Characteristics and Treatment Outcomes of Propionibacterium acnes Prosthetic Shoulder Infections in Adults

These authors report a retrospective analysis of what they identified as 24 P. acnes shoulder prosthetic joint infections. Patients presented with joint pain and diminished function. Erythrocyte sedimentation rate and C-reactive protein elevations occurred in 47% and 44%, respectively.

They report that 67% of cases treated with antibiotics only had a "favorable clinical outcome" comparable to other patients that had surgical and antibiotic treatment.

Comment: While there may be a role for antibiotic treatment of Propionibacterium prosthetic infections, it is not defined by this study.

Essentially they present a series of six cases identified on chart review that had joint pain and stiffness diagnosed 6.5, 7.4, 55.4, 2.8, 114.8, and 27.4 months after their index procedure by a single positive culture for Propi (presumably a joint aspirate) who were placed on antibiotics for 196, 1540, 232, 770, 126 and 189 days without surgical treatment. Of those six cases, four were reported to have a 'favorable clinical outcome' defined from chart notes: "The final clinical outcome was determined as per the clinical status at the last recorded clinical visit. An outcome was defined as favorable if there was a recorded improvement in pain symptoms and functional performance relative to a patient’s preintervention clinical status."

They also present some cases of painful stiff shoulders managed with surgery and antibiotics, but the groups cannot be considered comparable.

These authors have access to a large number of cases of failed shoulder arthroplasty. Hopefully in the future they will be able to provide us with some evidence-based guidelines regarding the approach to the painful, stiff arthroplasty.  Which patients should have joint aspirates? How is the result of a joint aspirate used along with clinical and laboratory evidence to determine the appropriateness of antibiotic therapy without surgery? Which antibiotics are used and for how long? How can clinical improvement be rigorously defined? How can the effect of antibiotics be distinguished from the effects of time and other factors? If antibiotic treatment fails, does it compromise the surgeon's ability to recover the offending organisms at the time of a revision procedure?


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