Differential Diagnosis for the 18-month-old Boy
- Single most likely diagnosis
- Nursemaid's elbow (subluxation of the radial head): This condition is common in young children, typically occurring between 1 and 4 years of age. The mechanism of injury, where the child falls while being pulled by the hand, is classic for this diagnosis. The presentation of the child holding the affected arm still and in pronation, with restricted elbow movement but no significant tenderness, further supports this diagnosis.
- Other Likely diagnoses
- Fracture of the humerus or forearm: Although less common than nursemaid's elbow in this context, fractures could occur from a fall and need to be considered, especially if there's significant swelling, deformity, or point tenderness.
- Elbow dislocation or other elbow injuries: While less common than radial head subluxation, other injuries to the elbow joint could occur from a similar mechanism and should be considered, especially if the child's symptoms or examination findings do not fully align with nursemaid's elbow.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
- Supracondylar fracture of the humerus with vascular compromise: Although this is a more serious injury, it is crucial to identify promptly due to the risk of neurovascular compromise. The absence of significant swelling or deformity does not rule out this condition, and any suspicion warrants immediate further investigation.
- Osteomyelitis or septic arthritis: While these conditions are less likely given the acute onset after a fall, they are critical to diagnose early due to their potential for serious complications. Fever, significant pain, or swelling out of proportion to the injury might suggest these diagnoses.
- Rare diagnoses
- Pathological fracture due to an underlying bone condition (e.g., osteogenesis imperfecta): In children with underlying conditions affecting bone strength, even minor trauma can lead to fractures.
- Brachial plexus injury: Although more commonly associated with birth trauma or significant force to the shoulder, a brachial plexus injury could potentially occur from a fall and should be considered if there are signs of neurological deficit in the arm.