Relevant factors in the diagnosis of concomitant osteomyelitis in pediatric hip septic arthritis. A series of 41 cases treated by hip arthroscopy

Introduction Septic arthritis of the hip can appear isolated or concomitant with pelvic osteomyelitis. Delay in the diagnosis of a concomitant osteomyelitis increases the number of required surgeries and of possible complications. Purpose This study aims to establish relevant factors in the diagnosis of concomitant osteomyelitis in cases with septic arthritis of the hip among paediatric patients. Methods The data were collected between 2005 and 2020. 41 pediatric patients with suspicion of septic arthritis of the hip joint, treated arthroscopically, were included. The following diagnostic test parameters were collected: ultrasound, MRI, X-Rays, blood samples, temperature, and incapacity to bear weight. The data were analysed with the sensitive analysis method using descriptive statistic. Results 41 patients were analyzed, with an average age of 6.04 y (7 months to 14 years), of which ten patients (24.39%) presented concomitant osteomyelitis. 6 out of ten patients needed secondary surgery. Regarding age, concomitant osteomyelitis was most common in the age group 4–14 years old. Average number of days of clinical symptoms before admission was 6.2 days. 36/41 cases showed CRP values higher than 2 mg/dl. 9/10 cases with concomitant osteomyelitis showed a CRP > 2 mg/dl, with an average value of 8.9 mg/dl. 22/41 patients underwent an MRI, of which nine cases presented a concomitant osteomyelitis. The probability of a child to have septic arthritis of the hip with adjacent osteomyelitis was analysed through a score based on four factors: impossibility to bear weight and/or hip pain in children in the non-walking age category, CRP > 2 mg/dl, age older than > 4 y, symptoms longer than 4 days. Conclusions Children at the age of walking, with incapacity to bear weight, presenting symptoms longer than 4 days and a CRP > 2 mg/dl, should receive an MRI before surgery to exclude adjacent osteomyelitis. Level of evidence IV.