These authors retrospectively reviewed the records of 14 patients who underwent diagnostic
shoulder arthroscopy to evaluate symptoms of shoulder pain or stiffness after a shoulder arthroplasty without an obvious cause. Patients were excluded if they had any traditional symptoms of infection or had a raised serum white cell count or C-reactive protein level prior to diagnostic arthroscopy. Patients were also excluded if available preoperative imaging showed evidence of loosening, periprosthetic fracture, or superior or anterior migration of the humerus or showed any other finding suggestive of the cause of pain.
The mean interval between the joint replacement and arthroscopic evaluation was over five years.
Prophylactic antibiotics were administered at anesthetic induction to diminish the risk of iatrogenic infection. At arthroscopy five synovial tissue samples were taken from different positions within the joint. Each tissue biopsy specimen was taken with a separate, clean arthroscopic punch and was cultured on Columbia Agar with ‘‘Chocolated’’ Horse Blood (incubated in carbon dioxide) and Fastidious Anaerobic Agar with Horse Blood (incubated anaerobically). Extended cultures were interpreted at 15 days. Biopsy findings were considered positive if the same organism was cultured on 3 or more of the 5 samples.
Arthroscopic biopsy specimens returned positive culture results in 3 patients (21%).
Of the patients who went on to definitive revision surgery, none had an unexpected positive microbiological result (defined as 3 positive samples from a further 5 samples) from samples taken at the time of revision surgery.
Of the 5 patients who underwent perioperative joint aspiration, only 2 had aspiration results that correlated with the biopsy results.
Other findings are summarized below
Comment: This study demonstrates the value of pre-revision shoulder arthroscopy in patients with failed arthroplasty for which a diagnosis cannot be made by clinical evaluation.
In contrast to some prior studies, these authors' technique includes harvesting five samples that were submitted for a culturing protocol specific for detecting Cutibacterium (Propionibacterium). It is of interest that the three cases with positive cultures, at least three of the specimens were culture positive. None of the cases had only one or two positive cultures.
These authors found that the findings at arthroscopy were helpful in guiding subsequent treatment of these patients.
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