Cutibacterium acnes Infection as a Cause of Nonunion After Ulnar-Shortening Osteotomy.

Ulnar-shortening osteotomy is a reliable solution to treat ulnar impaction syndrome, but it has a significant rate of nonunion as a known complication. Generally nonunion after the procedure is attributed to noninfectious causes. When infections happen, they follow the microbiological trends of nonunions elsewhere in the body. We present a case of ulnar-shortening osteotomy using an oblique-cut osteotomy system that resulted in septic nonunion. At the time of revision surgery, Cutibacterium acnes and Staphylococcus hominis were isolated from the osteotomy site. The patient was successfully treated using intravenous antibiotics and the two-stage Masquelet technique and eventually went on to bony union. As C acnes is rarely encountered in this context, this report highlights the need to consider all possible pathogens in the workup of a potentially septic nonunion. Surgeons should consider bacteria such as C acnes that require prolonged incubation for isolation from cultures, which may not be part of many institutions' usual protocol. [Orthopedics. 2024;47(4):e211-e213.].