From the Guidelines
The risk of osteomyelitis in the humerus following a single corticosteroid injection into the right shoulder is very low but not impossible, and given the patient's symptoms and presence of a contralateral psoas abscess, a systemic source of infection is more likely than a direct complication of the injection. In this case, with symptoms appearing 2 months after the injection, it's unlikely that the shoulder injection directly caused the osteomyelitis. More likely, the patient has a systemic source of infection that has seeded both locations. The psoas abscess suggests a hematogenous spread of bacteria that could have affected the humerus independently of the injection. Corticosteroid injections can temporarily suppress local immune function, potentially creating vulnerability to infection, but this effect typically wouldn't last 2 months [ 1 ].
The timing and bilateral nature of the infections point to a bloodborne infection rather than direct inoculation from the injection. The patient should undergo:
- Blood cultures to identify any bacteremia
- Imaging of both sites, with magnetic resonance imaging (MRI) with gadolinium being the imaging modality of choice for detection of early osteomyelitis and associated soft-tissue disease [ 1 ]
- Possibly bone biopsy to identify the causative organism Treatment would typically involve appropriate antibiotics for at least 8 weeks based on culture results [ 1 ], and possibly surgical debridement of infected bone, as surgical debridement and drainage of associated soft-tissue abscesses is the mainstay of therapy and should be performed whenever feasible [ 1 ].
The presence of infections at two distant sites warrants a thorough investigation for underlying conditions that might predispose to infection, such as diabetes, immunosuppression, or intravenous drug use. Monitoring of erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) level may be helpful to guide response to therapy [ 1 ].
From the Research
Osteomyelitis of the Humerus as a Potential Complication
- There are no direct research papers that discuss osteomyelitis of the humerus as a complication of a single corticosteroid injection in the right shoulder.
- However, studies have shown that osteomyelitis can occur as a result of bacterial infections, such as Staphylococcus aureus, which can be introduced through various means, including injections 2, 3, 4, 5, 6.
- The presence of a psoas abscess on the contralateral side may indicate a systemic infection, which could potentially lead to osteomyelitis in other parts of the body, including the humerus 2, 4, 5.
- The onset of symptoms 2 months post-injection could be consistent with a delayed infection, which is a known complication of injections 6.
- It is worth noting that immunocompromised states, such as those induced by corticosteroid therapy, can increase the risk of infections, including osteomyelitis 2, 6.
Risk Factors and Associations
- The studies suggest that risk factors for osteomyelitis and associated infections include immunocompromised states, such as diabetes, alcohol use disorder, and intravenous drug use 2, 4, 5.
- The presence of a psoas abscess, as in the patient's case, can be associated with osteomyelitis and other infections, such as epidural abscess and meningitis 2, 4, 5.
- The use of corticosteroids, such as prednisone, can increase the risk of infections, including osteomyelitis, particularly in immunocompromised patients 6.