Image Quiz

Low Back Pain in a Fourteen-Year-Old Boy (continued)

Answer: Osteoid osteoma in the left pars interarticularis, fourth lumbar vertebra.


Fig. 1-A
Fig. 1-B		 For larger view, click on image
Fig. 1-A Preoperative anteroposterior radiograph demonstrating the right lumbar curve. The lesion is on the concave side of the curve, just caudad to the apex. Pelvic obliquity is also noted.
Fig. 1-B Preoperative lateral radiograph demonstrating increased sclerosis in the area of the pars interarticularis of the fourth lumbar vertebra.

Fig. 2		 Fig. 2 Preoperative technetium bone scan showing uptake in the area of the left pars interarticularis of the fourth lumbar vertebra.

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Fig. 3		 Fig. 3 Computed tomographic scan showing a large nidus with surrounding sclerosis in the left pars interarticularis of the fourth lumbar vertebra.

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Because of the pain, markedly decreased motion, and spinal deformity, the patient was managed with an en bloc resection of the left pars interarticularis of the fourth lumbar vertebra. The lesion extended from the base of the left fourth lumbar pedicle to the superior margin of the left fourth lumbar inferior facet (Fig. 4).


Fig. 4		 Fig. 4 Intraoperative radiograph of the specimen, showing that the nidus has been excised.

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Histologic examination showed osteoid lined with plump osteoblasts and vascularized connective tissue, which, along with the size of the lesion, were consistent with the diagnosis of an osteoid osteoma. Postoperatively, the pain resolved and the patient was placed in a thoracolumbar spinal orthosis. At five weeks, the incision was healed, use of the orthosis was discontinued, and a home physical therapy program designed to improve hamstring flexibility was initiated. Twelve weeks after surgery, the trunk alignment had returned to midline. The patient progressed to normal activities with a 10 to 15-lb (4.5 to 6.8-kg) weight-lifting restriction. Seven months postoperatively, radiographs showed minimal residual deformity and the patient was permitted to return to full activities. At the time of the latest follow-up, three years after surgery, the patient was asymptomatic and there was no clinical or radiographic evidence of recurrence of the scoliosis.

Discussion

Jaffe first described osteoid osteoma in 1935. This benign lesion should be sought as the cause of neck or back pain, painful scoliosis, or radicular and referred pain in an extremity in any young patient. There should be a high index of suspicion for osteoid osteoma in a child or adolescent with back pain because pain typically precedes radiographic evidence of a lesion by several months. It is a likely cause of painful scoliosis in a child or adolescent in whom the scoliosis is greater when the patient is in the supine position than when he or she is standing erect. The curve typically progresses rapidly and is rigid, leading to limited spinal motion in all planes (as occurred in our patient). Kirwan et al. noted decreased spinal motion in sixteen (89%) of eighteen patients with an osteoid osteoma or osteoblastoma.

Osteoid osteomas are the most common cause of painful scoliosis in an adolescent. McLeod et al. reported that eleven (42%) of twenty-six patients in whom osteoid osteoma was undiagnosed for at least fifteen months after the onset of symptoms had scoliosis. Ozaki et al. found that two (22%) of nine osteoid osteomas were undiagnosed after two years. Plain radiographs and technetium bone scans are recommended as initial diagnostic modalities. Even if radiographs reveal negative findings, a technetium bone scan has been recommended for the evaluation of patients in whom this lesion is suspected. To our knowledge, a negative technetium bone scan has never been reported for a patient with an osteoid osteoma or osteoblastoma. When osteoid osteoma is diagnosed, surgical excision is recommended because of the risk that the scoliosis will become structural.

Mehta demonstrated that the patient's age at the time of the onset of pain and the duration of symptoms are important factors in determining whether the scoliosis will resolve. With more deformity (including vertebral rotation) and less time to maturity, the curve is less likely to regress. Ransford et al. reported that one (25%) of four skeletally mature patients had progression of scoliosis despite treatment. Similarly, Kirwan et al. reported that four (22%) of eighteen adolescent patients had progression of scoliosis.

During surgery, it is of paramount importance to obtain evidence that the entire nidus has been excised. Various methods can be used to make this determination, including preoperative injection of radioisotope and intraoperative localization with a gamma counter, computed tomographic scanning of the specimen, or Kirschner wire-guided localization as recommended by Lenke et al. One also can use intraoperative radiographs or can simply compare the findings on preoperative radiographs with those on computed tomographic scans. Lesions are not always discrete. Previous investigators have described an osteoid osteoma of the vertebral body that crossed the disc space as well as a posterior element lesion that affected two vertebral levels. Fusion is recommended only if stability is compromised. Wilkinson and Hall reported the case of a patient who had painful sclerotic changes in a pedicle opposite a neural arch abnormality that would lead one to err on the side of fusion in this circumstance. After excision, the pain usually is relieved within hours or days. Incomplete pain relief usually indicates incomplete tumor removal.

Reference

1. Crist BD, Lenke LG, Lewis S. Osteoid osteoma of the lumbar spine: a case report highlighting a novel reconstruction technique. J Bone Joint Surg Am. 2005;87:414-5.