Acute Osteomyelitis of the Posterior Column of the Acetabulum: About a Case

Introduction: Acute osteomyelitis usually occurs in the metaphysis of the long bones, the lower limb being more commonly affected than the upper limb. Pelvic localization is rare.

Observation: An 11-year-old boy with no remarkable history of illness visited our emergency room complaining from high fever and atromatic right hip pain. The orthopedic examination objectified a limitation of the right hip joint motions especially in extension, the palpation of the groin’s crease was slightly painful without local inflammatory signs nor lymphadenopathies. Blood laboratory tests found an inflammatory syndrome. Hip X-rays did not show any abnormality, the ultrasound of the right hip showed a joint effusion of low abundance measuring 1 mm. Magnetic resonance imaging detected anhypointense signal on T1-weighted sequences and a high intensity signal on T2-weighted on the right acetabulum with contrast enhacement after gadolinium administration. It combines a fat infiltration and a collection of 13x6 mm in the internal obturator muscle. The diagnosis of acute osteomyelitis of the posterior column with soft tissue invasion and reactive arthritis was confirmed. The blood cultures did not isolate a germ and the urinalysis was negative. The child was given antibiotic therapy: amoxicillin clavulanic acid and fusidic acid intravenously for a period of 21 days and then orally for a total duration of 12 weeks. The evolution was marked by a clinical improvement and a negation of the CRP. A 3-month control MRI showed total regression of the soft tissue collections.

Discussion: Pelvic osteomyelitis is rare, patients with pelvic osteomyelitis can present various clinical signs, which gives place to late or erroneous diagnosis. The prognosis of pelvic osteomyelitis is very favorable. The rate of recovery without sequelae is greater than 95%, but decreases with late diagnosis and treatment failure.

Conclusion: Osteomyelitis remains an endemic pathology in Tunisia despite the development of diagnostic’ means and antibiotic therapy. Pelvic osteomyelitis is rare; it poses a diagnostic problem especially with Ewing's sarcoma. Its prognosis is favorable but decreases with a delay of antibiotic administration.