Osteofibrous Dysplasia

Osteofibrous dysplasia (Campanacci disease, ossifying fibroma of long bones) is a rare, benign fibro osseous lesion of childhood that almost always arises in the anterior cortex of the tibial shaft, and often in the fibula. It consists of fibrous tissue with immature woven bone trabeculae rimmed by osteoblasts.

It presents in the first decade, usually before 5 years of age (often as anterior or anterolateral bowing of the tibia in a toddler), and sometimes at birth. Boys are slightly more often affected. About 10 to 20% of cases involve the fibula, and the lesion is rarely bilateral. Most lesions stop growing and regress in adolescence, but some persist.

Complications are progressive anterior bowing, tibial pseudarthrosis (about 10 to 25%, after fracture), pathological fracture, limb length difference, recurrence after curettage (up to 50% or more if done in a young child), and a rare association with adamantinoma, which is thought to be a related lesion.

Pathophysiology.

The lesion is a developmental disturbance of bone formation in the anterior tibial cortex. Keratin positive epithelial like cells are found in small numbers in some lesions, and trisomies 7, 8, 12 and 21 are described. The link to adamantinoma (osteofibrous dysplasia like adamantinoma) suggests a spectrum, in which osteofibrous dysplasia is a possible precursor, which is why biopsy is needed when features are atypical.

Painless anterior or anterolateral bowing of the tibia, local swelling, a firm bony lump, and sometimes a limp. Pain suggests a fracture. Leg length difference may occur. Many children come to attention after a minor injury with a fracture through the lesion.

Examine the tibia for bowing, swelling, tenderness, limb length, ankle and knee alignment, and the skin for café-au-lait spots (neurofibromatosis and congenital pseudarthrosis of the tibia).

• Radiographs: an eccentric, well defined, multiloculated lytic lesion (soap bubble or ground glass) in the anterior cortex of the mid-tibial diaphysis, with a rim of sclerosis, thickened cortex and anterior bowing. The medullary cavity is usually spared, and no periosteal reaction or soft tissue mass is present.
• MRI and CT for uncertain or aggressive lesions, to show intracortical location and extension.
• Biopsy when the age is over 10 years, the lesion grows or becomes painful, or imaging is atypical. Histology shows fibrous tissue with woven bone trabeculae rimmed by osteoblasts (zonal pattern, with bone maturing at the periphery). Immunohistochemistry for keratin separates adamantinoma, in which clusters of keratin positive cells are numerous.
• Blood tests are usually normal. Look for signs of neurofibromatosis type 1.

Differential diagnosis.

• Adamantinoma and fibrous dysplasia.
• Congenital pseudarthrosis of the tibia and non-ossifying fibroma.
• Chronic osteomyelitis (Brodie abscess) and physiological tibial bowing.
• Ewing sarcoma and stress fracture.

Treatment is conservative for most children, since lesions regress after puberty, and surgery in young children has a high recurrence rate and risks pseudarthrosis.

Observation. Clinical and radiographic review every 6 months until skeletal maturity. Most lesions stabilise or shrink. No restrictions on activity are needed in the absence of fracture.

Bracing. A clamshell ankle foot orthosis or protective brace for a child with progressive bowing or fracture risk, to protect the tibia until puberty. Bracing reduces fracture and does not correct the lesion.

Fracture. Cast treatment, with protection; most fractures heal. Nonunion or pseudarthrosis needs surgery (intramedullary fixation with bone grafting, or a circular external fixator) in a specialist centre.

Surgery.

• Indications: progressive deformity that is not controlled with a brace, recurrent fracture or pseudarthrosis, persistent growth of the lesion after puberty, or diagnostic uncertainty with features of adamantinoma.
• Delay surgery until age 15 where possible. Corrective osteotomy with fixation, after growth is nearly complete, treats deformity.
• Marginal or wide resection of the involved segment with reconstruction (vascularised fibular graft, allograft or bone transport) is used for progressive or recurrent disease after puberty. Curettage in a young child recurs often and is avoided.
• Any suspicion of adamantinoma needs referral to a sarcoma service, where wide resection is the treatment.

Operative antibiotic prophylaxis. Cefazolin 30 mg/kg to a maximum of 2 g intravenously (2 g in adults; 3 g when weight is 120 kg or over) within 60 minutes before incision as a single dose; with severe penicillin allergy, clindamycin 10 mg/kg (maximum 900 mg) intravenously or vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose.

Analgesia.

• Children: paracetamol 15 mg/kg orally every 4 to 6 hours (maximum 75 mg/kg daily and not exceeding 4 g daily) and ibuprofen 10 mg/kg orally every 6 to 8 hours with food (maximum 40 mg/kg daily and not exceeding 2400 mg daily), for up to 5 days; avoid ibuprofen with kidney impairment, dehydration or active bleeding. Avoid NSAIDs while a fracture or graft is healing.
• Adolescents and adults: paracetamol 1 g orally every 6 hours as needed (maximum 4 g daily; 3 g daily when weight is under 50 kg, with chronic alcohol use or hepatic impairment).

Monitoring. Radiographs every 6 months to skeletal maturity, then once at 1 year after maturity. Deformity, limb length and brace use at each visit. After surgery, radiographs at 6 weeks, 3 months, 6 months and 12 months. Biopsy for lesions that grow after puberty.

Referral and escalation. Refer every suspected osteofibrous dysplasia to paediatric orthopaedics. Urgent referral for fracture, rapid growth, pain, or atypical features suggesting adamantinoma or a malignant lesion.

Special groups.

• Young children: observe, brace and avoid curettage.
• Adolescents and adults with persistent or growing lesions: biopsy for keratin positive cells to exclude adamantinoma.
• Neurofibromatosis type 1: consider congenital pseudarthrosis of the tibia in the differential.
• Pregnancy: avoid NSAIDs in the third trimester.