Sunday, July 6, 2014

Open biopsy in the management of shoulder infections

Management of deep postoperative shoulder infections: is there a role for open biopsy during staged treatment?

These authors assert that the gold standard treatment of infected shoulder arthroplastiess is a 2-stage exchange arthroplasty. They note that reinfection after periprosthetic shoulder infections and periarticular osteomyelitis are reported to be as high as 37%.

They present a report of 18 patients who presented with periprosthetic shoulder infections and osteomyelitis after previous surgery. The deep infection was diagnosed by a combination of clinical signs and various diagnostic methods, including deep draining sinus, purulent drainage from the wound, erythema, abnormal white blood cell, C-reactive protein, erythrocyte sedimentation rate, computed tomography, magnetic resonance imaging, and joint aspiration.

Treatment included irrigation and debridement, removal of implants, antibiotic cement spacer placement, and pathogen-directed antibiotic therapy for 6 weeks. These authors used polymethyl  methacrylate spacers with 1 gram vancomycin and 1.2 grams tobramycin per bag of PMMA. After completion of antibiotics and resolution of clinical symptoms, specimens were obtained from an open biopsy performed in the operating room, followed by revision arthroplasty at a later date if final cultures were without evidence of infection. If evidence of infection persisted, then another course of I&D and antibiotic treatment was performed. 

The most common pathogens isolated were Propionibacterium acnes (44%), Staphylococcus epidermidis (39%), and S aureus (22%). Four patients (22%) had evidence of persistent infection on specimens from open biopsy and required subsequent rounds of I&D before replantation. The infecting pathogen in 75% of patients with persistent infection was P acnes, and 38% of patients with P acnes infection had recurrence.

Comment: This study underlines the fact that Propionibacterium can be a resistant pathogen in shoulder arthroplasty infections. 

The cases reported here are to be distinguished from those revisions for pain, stiffness or loosening in which there was no obvious clinical evidence of infection before or at surgery that went on to grow out Propionibacterium. 
Out of concern that the amount of antibiotic eluting from a spacer is small, our practice is to avoid the use of a spacer and instead, after thorough debridement and irrigation, to insert a humeral hemiarthroplasty with Vancomycin-soaked impaction allograft fixation and then to administer IV Cephtriaxone and Vancomycin for six weeks followed by a year of oral Augmentin as described here. Our primary exchange approach has the potential advantage of minimizing the number of surgical procedures. If - as is rarely the case - there is a clinical suspicion of recurrent infection after the primary exchange, another primary exchange is considered.


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