Diagnosis and treatment of subacute osteomyelitis

Subacute osteomyelitis is well known for diagnostic difficulty because of insidious nonspecific clinical courses and radiographic appearances mimicking various benign and malignant conditions. There are controversies regarding the need for surgical debridement and/or postoperative antibiotic therapy. The purposes of this study are to report our experiences of treating subacute osteomyelitis and compare the results of systemic antibiotic therapy with local gentamicin-polymethylmethacrylate bead implantation after curettage of bone lesions.

Twenty-three patients referred to the orthopedic oncology service but later proven to have subacute osteomyelitis were studied. These patients were randomly assigned to two treatment protocols after surgery. Group I patients received standard parenteral antibiotics for 2 weeks followed by oral antibiotics for 4 weeks (10 patients). Group II patients received local gentamicin-polymethylmethacrylate bead implantation (13 patients). Hospital stay, medical cost, clinical course, and results were compared.

All patients presented with diagnostic difficulties based on radiographic appearances. Penumbra sign on magnetic resonance imaging is helpful in differentiating subacute osteomyelitis from tumors. Hospital stay was significantly shorter (6.2 +/- 0.9 days vs. 16.4 +/- 1.1 days, p < 0.001), and medical cost was reduced (US $793 +/- 87 vs. US $1,268 +/- 98, p < 0.001) for group II patients. Both groups of patients responded well to the treatment regimens without recurrence of infection at a mean of 4.6 years after surgery.

Differential diagnosis between subacute osteomyelitis and neoplasms requires careful clinical and radiographic evaluation. Penumbra sign on magnetic resonance imaging is helpful in differential diagnosis. Surgical debridement and local antibiotic bead implantation shortens hospital stay, reduces medical cost, provides satisfactory results of infection control, and prevents complications of long-term systemic antibiotic use.