Review Question - QID 216841

This patient has radiolucent lines evident on radiographs concerning for infection. Cultures of the shoulder should be held for 14-21 days to observe for Cutibacterium acnes (C. acnes).

Shoulder PJI are serious complications of shoulder arthroplasty and a major cause for revision within the first 2 years. Diagnosis is multifaceted and involves a high index of suspicion given the indolent nature of the most common organism, C. acnes. Elevated inflammatory markers, radiographic changes around the prosthesis, and aspiration results can all assist with diagnosis, but inflammatory markers are often within normal limits. Treatment generally involves prolonged IV antibiotics and two-stage revision arthroplasty.

Grosso et al. reviewed the sensitivity of frozen section histology in identifying patients with Propionibacterium acnes (now C. acnes) infection during revision TSA and investigated various diagnostic thresholds of acute inflammation that may improve frozen section performance. They report that using current histopathology grading systems, frozen sections were specific but showed low sensitivity with respect to the P. acnes infection. They concluded that a new threshold value of a total of ten or more polymorphonuclear leukocytes (PMNs) in five high-power fields may increase the sensitivity of frozen sections, with minimal impact on specificity.

Padegimas et al. reviewed PJI following shoulder arthroplasty. They reported that hospitalization costs for PJI are comparable to those of primary arthroplasty, however, they are incurred after the original cost of shoulder arthroplasty. They concluded that certain identifiable patient variables correlate with higher PJI rates and risk factor modification may decrease PJI incidence and help contain costs.

Florschütz et al. retrospectively reviewed whether a difference in infection rate existed after primary anatomic TSA (aTSA) and primary reverse TSA (rTSA). They reported no difference in infection rate after primary aTSA and primary rTSA in shoulders that have not undergone previous operative interventions. They concluded that infection is more likely to develop in shoulders undergoing primary rTSA that have had one or more nonarthroplasty operative procedures.

Figure A is the AP radiograph of the right shoulder demonstrating radiolucent lines around the glenoid component of the anatomic total shoulder arthroplasty, concerning for PJI.

Incorrect Answers:
Answer 2: Irrigation and debridement would not be appropriate for a loose glenoid component irrespective of infection
Answers 3-5: Revision surgery may be appropriate but should not be performed prior to allowing for an adequate incubation time for C. acnes, as the mean duration of culture incubation for C. acnes is between 7-21 days.