Peripheral blood markers and intraoperative pathology may be helpful in predicting non-Cutibacterium acnes shoulder periprosthetic joint infections

Abstract

IntroductionThe purposes of this study were (1) to compare the preoperative complete blood count (with differential), c-reactive protein (cRP), erythrocyte sedimentation rate (ESR), and intraoperative pathology (frozen section) results of patients undergoing surgical treatment for shoulder PJI by C. acnes vs. non-C. acnes bacteria, and (2) to estimate sensitivity, specificity, and positive and negative predictive values of these parameters. MethodsBetween 2004 and 2016, 167 consecutive shoulder PJIs were treated surgically. Infected implants included hemiarthroplasty in 39, anatomic TSA in 92, and reverse TSA in 36 shoulders. Shoulders were categorized in one of 4 groups: irrigation and débridement (21), one stage reimplantation (14), two-stage reimplantation (124), and permanent resection (8). Medical records were reviewed to record microorganisms isolated, intraoperative pathology, and preoperative cell count, ESR, and c-RP. Shoulders were further grouped into those that were positive only for C. acnes (37 shoulders) and those that were positive for any other microorganism (130 shoulders). In order to calculate sensitivity, specificity, and predictive values, the same data was collected for a separate group of 700 shoulder arthroplasties that underwent revision surgery for noninfectious reasons during the same time period. ResultsFor the whole group of 167 infected shoulder arthroplasties, values were considered abnormal for leukocyte count in 15%, neutrophil count in 17%, ESR in 42%, cRP in 56% and pathology in 55%. Abnormal values were more common in the non-C. acnes group. The following positive predictive values were obtained: Leukocytes 47% (13% C. acnes, 43% other), ESR 65% (18% C. acnes, 62% other), cRP 70% (29% C. acnes, 66% other), and pathology 73% (30% C. acnes, 63% other). The following negative predictive values were obtained: Leukocytes 79% (94% C. acnes, 93% other), ESR 68% (86% C. acnes, 76% other), cRP 70% (88% C. acnes, 78% other), and pathology 87% (96% C. acnes, 91% other). ConclusionBacteria other than C. acnes were responsible for 75% of the shoulder PJI treated consecutively with surgery at a single institution over a 12-year period. Negative predictive values for cell count, ESR, cRP, and pathology ranged between 70% and 81%, but there were much lower for C. acnes infection. Obtaining these tests in the evaluation of a painful shoulder arthroplasty should not be discontinued, since their positive predictive value for non-C. acnes infections seem reasonable and their negative predictive value is high. Level of evidenceLevel III; Retrospective Comparative Study