• Yasunari Kamiya, Kenichi Mishima, Tetsuji Tanaka, Kenta Sawamura, Masaki Matsushita, and Shiro Imagama.
• Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.
• Medicine (Baltimore). 2023 Feb 17; 102 (7): e33012e33012.

RationalePlentiful vascularity and lack of the physis are thought to render the patella less vulnerable to osteomyelitis. Pseudomonas aeruginosa (PA) is an opportunistic pathogen predominantly affecting immunocompromised hosts. Despite the ubiquitous nature of PA, osteomyelitis of the patella caused by PA has been rarely reported in children.Patient ConcernsA 5-year-old boy who had presented with a prolonged history of the left anterior knee pain following minor trauma was diagnosed with prepatellar bacterial cellulitis and bursitis. Afterward, a focal osteolytic lesion emerged at the ventral surface of the patella despite oral and intravenous antibiotic therapy lasting for weeks. We described clinical presentation as well as medical and surgical management of pediatric patellar osteomyelitis secondary to prepatellar septic bursitis.DiagnosesPseudomonas aeruginosa-associated osteomyelitis of the patella. Magnetic resonance imaging of the left knee showed a focal destructive change of the ventral half of the cartilaginous patella and a suprapatellar joint effusion. Bacterial culture from the bursa revealed Pseudomonas aeruginosa.InterventionsSystemic inflammation, patellar osteochondral destruction, and purulent synovial fluid of the knee were prolonged for 6 weeks despite antibiotics use deemed appropriate and reparative surgical debridement, whereas they were eventually resolved with a 6-week course of intravenous ceftazidime and cessation of continuous intracapsular irrigation.OutcomesHe was clinically asymptomatic at the latest follow-up but exhibited a minor leg length discrepancy <2 cm associated with overgrowth of the affected femur.LessonsThis is a rare case of Pseudomonas osteomyelitis of the patella in a healthy pediatric patient. Uncommon osteochondral sequelae occurred probably because of a protracted arthritis of the affected knee. We would like to emphasize the ineffectiveness of continuous irrigation without antibiotics for Pseudomonas aeruginosa-associated osteomyelitis.Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.

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