Thursday, November 3, 2011

Infection and shoulder arthroplasty - November JBJS

The November Journal of Bone and Joint Surgery contains an interesting article by Jawa et al on the use of cement spacers in the treatment of infection after shoulder joint replacement. Infection was resolved in most of these cases, although eight of the the 28 patients had complications. Sixteen had a second stage arthroplasty (ten reverse shoulder arthroplasties, three hemiarthroplasties, two total shoulder arthroplasties, and one resection arthroplasty.) These results were not compared to those having other management approaches, such as a single stage revision.

What I found particularly interesting were the laboratory results before surgery and the culture and lab results from surgery. These are reproduced below:

Before surgery, the white blood-cell count was elevated in only one (4%) of the twenty-eight patients, the erythrocyte sedimentation rate was elevated in sixteen (70%) of twenty-three patients, and the C-reactive protein level was elevated in fifteen (79%) of nineteen patients.
Positive culture results were found for twenty-four (86%) of the twenty-eight shoulders. Propionibacterium acnes was identified on culture of specimens from fifteen (54%) of the twenty-eight shoulders, and coagulase-negative Staphylococcus was identified on culture of specimens from thirteen shoulders (46%); a combination of both of these organism grew on culture of specimens from nine shoulders. Peptostreptococcus was identified on culture of specimens from three shoulders (11%); in all three cases, Propionibacterium acnes and coagulase-negative Staphylococcus also were identified on culture. Staphylococcus aureus was identified on culture of specimens from two shoulders (7%); in one of these two cases methicillin-resistant Staphylococcus aureus (MRSA) was identified. Corynebacterium was identified on culture of specimens from two shoulders (7%), and Serratia was identified on culture of specimens from one shoulder (4%). The cultures were routinely held for two weeks.
On histological examination, eighteen of twenty-one specimens showed signs of acute or acute and chronic inflammation.

These results point to the difficulty of the diagnosis and management of infections after shoulder arthroplasty, a diagnosis that needs to be always considered when the clinical course deviates from the expected. It also points to the potential for shoulder replacements to become infected with organisms that normally inhabit the skin, such as P. Acnes and S. Epidermidis.


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