Are antibiotic spacers a benign treatment for shoulder infections?

Complications of antibiotic cement spacers used for shoulder infections

These authors performed a retrospective review of one of two types of commercially available antibiotic spacers implanted in 53 patients (60 spacers) between April 2009 and October 2017 as part of a 2-stage treatment plan.

The 39 infected arthroplasties included 15 anatomic total shoulder arthroplasties, 13 hemiarthroplasties, 10 reverse total shoulder arthroplasties (RTSAs), and 1 cup arthroplasty. The nonarthroplasty shoulder infections included 4 after open reduction and internal fixation of proximal humeral fractures, 3 after rotator cuff repair, 1 after an infected Latarjet procedure, as well as 6 primary shoulder infections without previous surgical procedures. The 14 patients with non-arthroplasty infections had a septic joint with articular destruction and humeral head collapse that precluded any other joint-preservation treatment plan.

All patients were followed up from spacer placement to second-stage revision to shoulder arthroplasty. Ten patients retained the spacers and were followed up for a minimum of 1 year.

No complications were associated with implantation of the spacers. However, of the 44 patients (50 spacers) who underwent a second-stage revision after a mean interval of 6 months (range, 2-18 months), 14 patients had 18 complications.

Fourteen complications occurred between implantation and removal.  The most common complication was bone erosion (6 in the glenoid and 2 in the humeral shaft). 

Other complications were fractures of the spacer (n = 4), spacer rotation (n = 3), and humeral fracture (n = 3). 

 Comment: These authors state that the "infection" diagnosis was based on a combination of symptoms, clinical findings, and laboratory tests. For cases of periprosthetic infection, they used the Musculoskeletal Infection Society criteria (Clin Orthop Relat Res (2011) 469:2992–2994):

However, much of the information needed to use the MSIS criteria to classify a shoulder as being "infected" is not available at the time of the revision arthroplasty. Specifically the results of intraopertive cultures are not available in time to be used to determine the need for a spacer.  Thus, the indications for the use of a spacer are not well defined. 

This paper demonstrates that the use of spacers can be complicated by humeral and glenoid bone loss as well as by humeral and glenoid fracture. The authors also point out that achieving stability of the spacer in the canal can be challenging: insufficient fixation can lead to instability, while the use of cement for fixation can lead to difficulties in the removal of the spacer at the second stage. 

In most cases, our practice is to use a single stage revision without the intermediary of a spacer as our initial procedure in the management of a suspected periprosthetic infection (see this link). This procedure allows augmentation of the humeral bone stock and secure humeral component fixation using impaction allografting and minimizes glenoid erosion by using an implant with a smooth metallic surface rather than the more abrasive surface of a cement spacer. We reserve the use of spacers for failed single stage exchanges or when the presence of a particularly virulent organism (such as MRSA or gram negative rod) is suspected.

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