New concepts aid in diagnosis, treatment and management of shoulder infection
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Shoulder surgeons can improve the diagnosis and management of infection in their patients after shoulder arthroplasty by applying a few new strategies, participants in a symposium said.
Eric T. Ricchetti, MD, of the Cleveland Clinic, who discussed evaluation of prosthetic joint infection (PJI) of the shoulder, moderated the symposium at the Musculoskeletal Infection Society Annual Meeting, which was held virtually.
“PJI of the shoulder has been shown to be both a diagnostic and therapeutic challenge due to the low virulence of the commonly cultured organism. [Propionibacterium acnes] P. acnes has been shown to be the most commonly cultured organism in revision arthroplasty and has been recently re-identified as Cutibacterium acnes or C. acnes,” Ricchetti said.
He said the typical diagnostic steps are important in the workup of a patient with pain or stiffness after shoulder arthroplasty and include imaging and checking the serum erythrocyte sedimentation rate and C-reactive protein.
Ricchetti said diagnosis criteria emerged from the 2018 International Consensus Meeting, which created a definite PJI category for overly virulent cases, as well as a scoring system that can be used in cases when the PJI criteria are not met.
However, despite the availability of these criteria and newer diagnostic approaches, should a clear PJI diagnosis not be possible, surgeons should be aware that the best treatment for shoulder PJI may still remain unclear.
“Although a new diagnostic criteria for PJI of the shoulder has been developed, and hopefully will make diagnosis now more clearly made in many situations, the treatment algorithm is still not clearly defined in all settings with regard to shoulder PJI,” Ricchetti said.
Diagnostic arthroscopy to obtain synovial fluid and assess component positioning and rotator cuff status, for example, is a technique that can inform decision-making regarding next steps in a patient’s treatment, he said.
‘Stealth’ infection
C . acnes, which lives in the sebaceous glands under the skin surface, may be hard to detect in a failed shoulder arthroplasty.
“Its presentation is not always obvious,” Jason E. Hsu, MD, of the University of Washington in Seattle, said.
“This has important clinical implications because it allows the bacteria to be shielded from our usual skin preps” and not be penetrated by the antibiotics usually used for shoulder infections, he said.
Therefore, C. acnes, which is a gram-positive rod that can exist in an aerobic environment, can develop biofilms. These are also the cause of “stealth” infections that have delayed onset of pain, stiffness and loose implants, Hsu said.
Better interpretation of cultures, looking for two to six positive cultures, and waiting about to 2 to 3 weeks for culture results may be needed when a C. acnes infection is suspected, according to Hsu.
“Preoperative data can be helpful. We found that male sex [and] positive skin swabs are highly predictive of deep culture positivity,” he said, but noted the use of postoperative antibiotics in patients with C. acnes infection is controversial because it is unclear who should receive these.
Reverse shoulder arthroplasty option
Treatment strategies for PJI of the shoulder were discussed by Grant E. Garrigues, MD, of Midwest Orthopaedics at Rush in Chicago, who said “antibiotics alone don’t work.”
Debridement, antibiotics and implant retention, known as the DAIR procedure, is “reasonably effective,” he said.
In discussing one-stage vs. two-stage exchange arthroplasty, Garrigues said reverse shoulder arthroplasty (RSA) is frequently used as a one-stage option and allows aggressive debridement. However, data supporting this approach should be taken with a “huge grain of salt” because many of the studies in which RSA was used involved lower virulence organisms.
He said some studies have shown that two-stage exchange arthroplasty may provide better infection clearance than one-stage exchange arthroplasty, while other research has linked higher Constant-Murley scores, and thus better function, with one-stage exchange.
Regarding permanent spacers, Garrigues reserves use of these for lower-demand patients.
“There [are] decent data that many patients can do well with this. Especially if the tuberosities are retained, they will have some active external range of motion,” he said.
Garrigues concluded, “The implications of treatment of unexpected positive cultures are unclear.”
Although one-stage and two-stage exchange revisions may have similar infection clearance, one-stage “may have a better range of motion, although it’s not clear. A thorough surgical debridement is critical.”
Explantation is key to reconstruction
Surena Namdari, MD, of Rothman Orthopaedic Institute in Philadelphia, who discussed reconstructive options patients with shoulder PJI, said, “The most important part of the reconstruction is the explantation, the mechanical debridement and the irrigation.”
He encouraged surgeons to avoid leaving behind pieces of a convertible implant that may cause an “infectionitis.”
“Because of this, my current preference is to use implants that are easily revisable — short stem or stemless — and are less designed for convertibility,” said Namdari.
He reviewed his various approaches to address ongoing infection, bone loss, and glenoid and humeral defects, based on size, that are encountered during revision reconstructions.
“My personal approach to this is to use a standard stem, cemented proud for anything less than 5 cm of humeral bone loss. For those patients with poor healing potential who are unlikely to outlive the prosthesis, I’m more inclined to use a megaprosthesis,” he said. “For younger patients with better healing potential and larger bone defects, that will put even great stresses on the implant, I am more inclined to use an alloprosthetic composite.”
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Ricchetti ET, et al. Symposium: New approaches to the diagnosis and management of periprosthetic joint infection (PJI) of the shoulder. Presented at: Musculoskeletal Infection Society Annual Meeting; Aug. 7-8, 2020 (virtual meeting).
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