Teaching Case

Pain in the left groin following a normal vaginal delivery.

A 21-year-old lady presented with pain in the pubic symphysis a year after a normal vaginal delivery. X-ray showed expansion and irregular sclerosis of the left pubic bone with some periosteal reaction. MRI and CT scan were done. She had a CT guided biopsy which grew coagulase negative Staphylococcus. She had raised inflammatory markers. She was given antibiotics with resultant response.

Beer first described Osteitis pubis in 1924. It is usually a self limiting, non-infectious process. A variety of causes have been postulated, pregnancy, direct trauma, athlete exertion, urological manipulation and urological and gynaecological surgery. Such patients usually have progressive suprapubic pain radiating to the groin and both legs. A characteristic gait has been described which is due to abdominal muscle spasm. WBC and ESR are usually raised (but can be normal). Osteomyelitis; which is a separate condition; and osteitis pubis have similar clinical and radiological manifestations. Symptoms are suprapubic pain and tenderness. Pain increases on ambulation. Bone destruction is more pronounced with osteomyelitis than with osteitis pubis. Less then 10% of cases of osteomyelitis occur in the pelvis with pubis the least affected. Two cases of osteomyelitis of pubis following normal vaginal delivery have been reported before. In both osteomyelitis and osteitis pubis, x-ray of the pubic bone shows bone rarefaction and erosion. There may be separation of symphysis. MRI is useful in the early stages, demonstrating marrow oedema. The abnormal marrow has a low T1W and a high T2W signal. Additional abnormalities in osteomyelitis are cortical erosion or perforation, periosteal reaction, abscess, sequestrae and sinus tracts. MRI is useful in ruling out active marrow involvement, localising pus collections in chronic osteomyelitis and in separating cellulitis alone from cellulitis with osteomyelitis. Fat saturation and contrast-enhanced sequences are usually used. STIR sequence is particularly useful. Brodie’s abscess is seen better after contrast, sequestrae are low to intermediate on the T1W and T2W and show no enhancement. Burns and Gregory proposed that the diagnosis of osteomyelitis requires the presence of radiological changes and histologic finding of infection of both bone and bone marrow. This may mean blood culture and/or bone aspiration or biopsy. Hoymes reported that Staphylococcus aureus is found in 60% of cases and gram negative bacteria in 40%. For suspected osteomyelitis, treatment with intravenous antibiotics followed by oral antibiotics for an appropriate duration is recommended. Surgery may be required in certain cases.