Labeled white blood cell/bone marrow single-photon emission computed tomography with computed tomography fails in diagnosing chronic periprosthetic shoulder joint infection

Background: Shoulder periprosthetic joint infections (PJI) caused by low-virulent bacteria pose a diagnostic challenge. Combined labeled leukocyte (WBC) and technetium 99m sulfur colloid bone marrow imaging (WBC/BM) is considered the radionuclide imaging gold standard for diagnosing lower limb PJI. However, it is laborious and expensive to perform, and documentation on shoulder arthroplasties is lacking. This study investigated WBC/BM single-photon emission computed tomography-computed tomography diagnostic performance in shoulder PJI.

Method: All patients with a failed arthroplasty referred to a highly specialized shoulder department were scheduled for a diagnostic program including a WBC/BM. If an arthroplasty was revised, biopsy specimens were obtained and cultured for 14 days. The diagnostic performance of WBC/BM imaging was determined using biopsy specimens as a reference.

Results: Of the 49 patients who underwent a WBC/BM scan, 29 (59%) were revised. Infection was present in 11 patients, in whom 2 WBC/BM scans were true positive. The WBC/BM scan in 9 patients was false negative. The remaining 18 patients all had a true negative WBC/BM scan. WBC/BM showed a sensitivity 0.18 (95% confidence interval [CI], 0.00-0.41) and specificity 1.00 (95% CI, 1.00-1.00) in detecting shoulder PJI. The positive predictive value was 1.00 (95% CI, 1.00-1.00), and negative predictive value was 0.67 (95% CI, 0.49-0.84). No patients infected with Cutibacterium (formerly Propionibacterium) acnes resulted in a positive WBC/BM, nor had they preoperative or perioperative signs of infection.

Conclusion: A positive WBC/BM was found only in patients with obvious PJI. Hence, the scan added nothing to the preoperative diagnosis. The WBC/BM single-photon emission computed tomography-computed tomography scan cannot be recommended as a screening procedure when evaluating failed shoulder arthroplasties for possible infection.