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Adolescent girl with back pain

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Q1: What abnormalities are seen on the radiological investigations (see figs 1–3; p 432)?

The plain radiograph shows a right thoracolumbar scoliosis with apex at L2. The bone scan shows intense activity over left side of the second lumbar vertebra. The computed tomogram shows widened left superior articular facet (black arrow) of L2. A lesion with a central nidus and surrounding sclerosis is seen. The inferior articular facet (white arrow) is normal. Radiographs of her pelvis (not shown) confirmed that she was skeletally mature.

Q2: What is the likely diagnosis and how does it usually present?

The diagnosis is osteoid osteoma involving the left superior articular facet of L2 vertebra. Osteoid osteomas are benign bone tumours. The lesion commonly presents between the ages of 10 and 25 years and has a male preponderance.1 The proximal femur is the commonest location followed by tibia and the posterior arch of vertebra.2 Patients with lesions in the spine typically present with painful scoliosis and, less commonly, with varying degrees of radicular leg pain.1 The pain is usually severe, frequently in the night, and is not aggravated by exercise or position. Movements of spine are often painful. Salicylates are usually helpful in relieving the pain. The scoliosis is typically described as C shaped curve. The lesion is usually found at the apex on the concave side of the curve.3 The radiological diagnostic features of osteoid osteoma are described in box 1.

Box 1: Radiological diagnostic features of osteoid osteoma5

  • A sharp round or oval lesion.

  • Less than 2 cm in diameter.

  • A homogeneous dense centre.

  • A peripheral radiolucent zone of 1–2 mm.

Discussion

In children and adolescents complaints of back pain (box 2), especially painful scoliosis, should be taken seriously. Painful scoliosis may signify a tumour or spinal cord anomaly.4 Bone scanning is an excellent screening method for the adolescent with back pain.

Box 2: Differential diagnosis of painful spine in children and adolescents1

  • Congenital: spondylolisthesis.

  • Inflammation: Sheuermann’s disease, rheumatoid arthritis, reactive arthritis.

  • Infection: pyogenic, tuberculosis.

  • Traumatic: fractures, spondylolysis.

  • Disc prolapse.

  • Metabolic: rickets/osteomalacia.

  • Tumours: primary and secondary.

The investigation of a painful spine in children (particularly if pain persists) should begin with blood tests including full blood count, inflammatory markers, and conventional radiographs. If the clinical and radiological features suggest an osteoid osteoma, isotope bone scanning should be the investigation of choice to confirm this. Computed tomography aids in delineating the lesion better and helps in preoperative planning. If the bone scan is negative and the cause of the pain is still unknown, magnetic resonance imaging will help to rule out pathologies such as spinal cord anomalies, adolescent disc prolapse, and tumours.

Scoliosis develops in osteoid osteoma secondary to paraspinal muscle spasm.6 The nidus of osteoid osteoma is richly vascularised and innervated. This is thought to account for the relief with salicylates.2

Even though the natural history of osteoid osteoma may be one of spontaneous remission, the treatment of spinal osteoid osteoma is surgical removal of the nidus by en bloc excision. This is because the time interval before remission may range from two to eight years and the scoliosis can become structural during this period.6

Percutaneous radiofrequency ablation is gaining popularity in the treatment of osteoid osteomas. However, spinal osteoid osteomas should only be treated by radiofrequency ablation if the nidus is located at least 1 cm away from vital structures, in order to prevent neurological complications.7 If the nidus is removed, the patient is usually relieved of pain at once.1,2 Scoliosis usually resolves completely if the excision is undertaken within 18 months of the start of symptoms.4 Complete excision of the lesion results in a cure and recurrence is very unusual.1

Final diagnosis

Osteoid osteoma of superior left facet of second lumbar vertebra.

REFERENCES

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