Injection-induced Low-grade Infection of the Shoulder Joint: Preliminary Results

Background: Purulent arthritis of the shoulder has been widely reported. Low-grade post-operative infections of the shoulder have also been observed. Low-grade infections of the shoulder without prior surgery have not been reported in the literature. The purpose of this study is to present our experience of seven patients with low-grade infections of the shoulder without a history of prior surgery.

Methods: We retrospectively reviewed seven patients, mean age of 45 years that originally presented with diffuse shoulder pain, with or without stiffness. None had prior surgery but all had prior injections, average 5.6, into the shoulder. All patients were treated with various arthroscopic procedures. All had harvesting of four tissue probes identifying low-grade infection. Pre/post-operative pain score, pre/post-operative range of motion, intraoperative findings, post-operative Constant score, Subjective Shoulder Value and pre/post operative radiographs were analyzed. Post-operative antibiotic therapy was recorded.

Results: All patients showed synovitis without pus or any other sign of infection. Propionibacterium acnes were identified in five, coagulase-negative Staphylococcus in two, and Staphylococcus saccharolyticus in one shoulder. One patient had a mixed infection (Propionibacterium acnes and coagulase-negative Staphylococcus). Therapy consisted of oral antibiotics for 1-6 months. Four patients had a satisfactory and three an unsatisfactory outcome.

Conclusions: Diffuse shoulder pain with or without stiffness in patients without prior surgical history can be caused by low-grade infection. Treatment using oral antibiotics has unpredictable outcomes. Further studies are necessary to analyze this pathology.

Level Of Evidence: Level IV, retrospective case series, treatment study.