Monday, August 1, 2016

Propionibacterium - the most common bacterium recovered from failed shoulder arthroplasties. Treatment with a spacer.

Definitive Treatment of Infected Shoulder Arthroplasty With a Cement Spacer.

These authors present 9 patients from a single institution who had an infected shoulder arthroplasty. The culture results show that 6 out of the 9 cases were culture positive for Propionibacterium - interestingly one was P. Granulosum rather than P. Acnes. Of the 9 patients in this study, 6 were men. Mean age was 73±9 years. Of the study patients, 1 had diabetes, 2 presented with Parkinson's disease, and 5 had a history of tobacco use. Average body mass index was 27.9±7 kg/m2.

This report describes management with a cement spacer consisting of gentamicin-impregnated polymethyl methacrylate around an AISI 316L stainless steel core. 

All patients had a minimum of 2 years of follow-up.  After mean follow-up of 4 years, none of the patients had clinical or radiographic evidence of infection. Functional outcomes, as measured by American Shoulder and Elbow Surgeons scores, were good or fair in 89% of patients, and the average American Shoulder and Elbow Surgeons score was 57. A review of recent literature suggested that the current findings were similar to those in studies reporting 1- or 2-stage revision procedures. Although cement spacers are typically used as part of a 2-stage revision procedure, the authors suggest that cement spacers can be used effectively to eradicate infection and allow for acceptable functional recovery and range of motion in patients who have severe medical comorbidities and cannot tolerate additional surgery (see the example below of the use of a spacer to manage the infected hemiarthroplasty in an 87 year old man).

Comment: In spite of intense interest in determining the ideal management of failed shoulder arthroplasties with positive cultures for Propionibacterium, the role of single stage prosthesis exchange (see this link), exchange first with a spacer and then a prosthesis at a second stage (two-stage exchange), or, as presented here, a single stage exchange with a spacer. Because of the propensity of this organism to form a biofilm, it is likely that removal of all colonized implants is an important step. Whether it is better to then insert a spacer or a new implant remains unclear. One of the downsides of a 'permanent' space, as the authors of this article point out, is the possibility of glenoid erosion from articulation with the spacer.