Septic arthritis and epidural abscess

Case contributed by Liz Silverstone
Diagnosis almost certain

Presentation

Right hip pain for 6 weeks. Steroid injection 3 weeks ago. Lower back pain and bilateral leg pain treated by steroid injection in the lumbar spine a few weeks ago.

Patient Data

Age: 45 years
Gender: Female

Narrow right hip joint, especially superiorly. Much of the subchondral bone plate in the femoral head is ill-defined. Markedly thinned acetabular roof cortex, especially laterally where there is a subchondral “cyst”. Fat pads poorly seen.

Thinned joint cartilage and periarticular bone edema with joint effusion and surrounding soft-tissue inflammation.

Osteonecrosis of the superior femoral head.

Canal stenosis maximal at L3/L4 compressing the cauda equina due to dorsal epidural collection and congenitally narrow canal. The wall of the collection enhances and the collection measures 8mm in depth at L3/L4.

Features of bilateral L3/L4 facet joint septic arthritis and extensive myositis of the paraspinal muscles.

Case Discussion

Infective complications of steroid injection which had been overlooked, necessitating spine and hip surgery and resulting in substantial morbidity and long-term disability.

The rate of chondrolysis depends on the virulence of the organism and, if Staphylococcus aureus is responsible, can occur over 1-2 days. This makes diagnosis by aspiration a matter of urgency. Osteonecrosis can complicate local infection.

Suspect septic arthritis in patients with a history of steroid injection and in patients presenting with monoarticular arthropathy.

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