These authors conducted a systematic review of articles reporting 163 1-stage shoulder procedures and 289 2-stage shoulder procedures for periprosthetic infection. A 2-stage revision is one in which an antibiotic spacer is inserted at the first revision followed by subsequent re-revision to a hemiarthroplasty, an anatomic total shoulder or reverse total shoulder.
Cutibacterium acnes was the organism most frequently grown on culture (37%) followed by coagulase-negative Staphylococcus (19%). Notably, infections with these organisms usually do not result in the type of clinical manifestation characteristic of lower extremity periposthetic infections.
"Infection clearance". Patients who underwent another revision after the index 1 or 2-stage
revision, progressed to arthrodesis, or underwent any other procedure beyond the intended 1 or 2-stage revision protocol due to persistent infection were considered by the authors as having failed infection clearance. The overall "infection clearance" rate was reported as 95.6% for 1-stage and 85.2% for 2-stage procedures.
The decision between 1 and 2-stage revisions was based a combination of factors including preoperative identification of the organism, patient age and comorbidities, timing of infection (acute, subacute, chronic), findings on the preoperative clinical examination, the intraoperative soft-tissue/osseous appearance, adequacy of debridement, the patient’s preference and the surgeon’s preference.
Comment: The important question is: when performing a revision arthroplasty, how is a surgeon to determine whether to treat the shoulder as if it is infected? In some cases, the presence of an infection is obvious and in others it is not. Studies of the outcome of treatment for these two groups of patients should be assessed separately. Here's how we apply selection bias to their treatment.
"Obvious" infections. The possibility infection is high in the presence of preoperative and intraoperative findings of fever, chills, erythema, swelling, draining sinus, elevated blood markers of inflammation (white blood cell count, sedimentation rate, C-reactive protein), fluid aspirate cultures that are positive for bacteria, as well as synovitis, osteolysis, purulence, and elevated white cells per high power field on frozen section of deep tissue samples noted at the time of surgery.
In our practice such cases are commonly treated with thorough debridement, Betadine lavage, an antibiotic-containing spacer, topical antibiotics and postoperative antibiotics. The decision to leave the spacer in place or to perform a second stage revision to a hemiarthroplasty, anatomic total shoulder, or reverse total shoulder is based on the clinical response to treatment, the condition of the patient, the condition of the shoulder and the results of a detailed discussion of the possible options.
The outcome of treatment of these obvious infections is straightforward - success is the resolution of the signs and symptoms of infection while failure is persistence or recurrence.
"Stealth" infections. The challenge comes in the management of shoulders being revised without the obvious characteristics of an infection listed above. As pointed out in this review, Cutibacterium is the most common organism grown on tissue and explant cultures obtained at the time of revision arthroplasty, yet in most cases the patients with Cutibacterium periprosthetic infections do not manifest preoperative or intraoperative findings suggesting infection. Cases of Cutibacterium periprosthetic infection characteristically present as pain and stiffness having an onset after a benign "honeymoon" period of postoperative recovery. Aspirates of joint fluid and serum markers are relatively insensitive to the presence of Cutibacterium.
In the revision of cases where the preoperative and intraoperative findings are not strongly suggestive of infection, we usually favor a single stage prosthesis exchange with postoperative antibiotics until the results of intraoperative tissue and explant cultures become available. This covers both bases: (1) a culture positive revision and (2) a culture negative revision without submitting the patient to a potentially unnecessary spacer implantation.
"Infection clearance". Patients who underwent another revision after the index 1 or 2-stage revision, progressed to arthrodesis, or underwent any other procedure beyond the intended 1 or 2-stage revision protocol due to persistent infection were considered by the authors as having failed infection clearance. This definition works well for "obvious" infections. By contrast, determining the outcome of treatment of "stealth" infections is not straightforward. Patients may have persistent problems of pain and stiffness after the revision; determining whether these symptoms are due to persistent infection is at least as difficult as diagnosing a Cutibacterium periprosthetic infection in the first place. The only clear cut indication of failure of management is a revision surgery at which cultures are positive for the same organism isolated from the initial revision. Lack of a revision cannot be used as an indiction of "infection clearance".
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