Where as back pain is a very common complaint in adults, it is relatively rare in children. However, it is much more likely to be the result of a serious pathologic lesion. Relatively minor complaints and findings may be associated with major problems. A recent study from a large English children's hospital revealed that only two percent of all referrals were for back pain but that over fifty percent of these had an identifiable serious spinal problem.

Back pain in children requires a very careful evaluation. A thorough medical history should include mode of onset, nature, duration, and seventy of the pain, inquiry as to neurologic changes, especially as regards bowel and bladder function, gait, and foot deformities, and finally a review of systems looking for other clues.

The physical exam must include a screening exam of posture, movement with position change, swelling or restricted joint motion, as well as a specific exam of the back, including point tenderness, spasm, restricted motion, scoliosis or kyphosis, and the presence of any skin lesions. Finally, a complete neurological exam is essential. Initial x-ray evaluation would include anteroposterior and lateral views of the area involved. Further studies would be carried out if indicated by the previous workup. A CBC, sedimentation rate and urinalysis should be part of the original screening tests.

The differential diagnosis includes developmental abnormalities, mechanical derangements, inflammatory processes, neoplastic diseases, and conversion reactions (see Table 1). It is very important to rule out serious pathologic conditions before making the diagnosis of strain, sprain, or functional disorder, the latter often being the result of exclusion.

Mechanical Derangements
1. Poor Posture. Postural abnormalities rarely cause pain in children. The treating physician would be wise to rule out other spinal problems before attributing the discomfort to a postural deviation.

2. Muscle Strain. Most children participate in multiple physical activities and sports. Their muscles have great resiliency and they rarely experience post exercise soreness. Occasionally, an "overuse syndrome" will occur with excessive muscular exertion, usually related to sports. This diagnosis is made on the basis of the history and exclusion of other spinal pathology. This cause is most common in sedentary children who have recently increased their activity level.

3. Herniated Nucleus Pulposus. This condition is rarely seen under the age of ten. The incidence is not known but one to two percent of disc excisions are performed on those under sixteen years of age. The presentation is unusual with two-thirds complaining of back pain and only one-third with sciatica. The physical exam usually reveals muscle spasm, decreased lumbar lordosis, limited forward flexion, scoliosis, and positive straight leg raising. Motor weakness, hypoesthesia, and diminished or absent deep tendon reflexes may occur. The definitive diagnosis is made by imaging techniques such as C.T. scanning, MRI, or myelography. Early treatment would be bed rest followed by disc excision if the symptoms worsen or do not regress over a three to six week time period.

4. Acute Fracture Of The Pars. Some children will present with severe low back pain following major trauma or severe exertional activity. An oblique x-ray of the lumbar spine will reveal spondylolysis (a defect in the pars interarticularis) - usually on one side. A bone scan should be carried out to determine if this is an acute event rather than a long standing developmental disorder. If so, the treatment would be cast treatment or bracing until the fracture heals.

Developmental Disorders
1. Spondylolysis/Spondylolisthesis. Spondylolysis and spondylolisthesis (a forward slip of one vertebra on another) are fairly common causes of back pain in children. They have not been reported at birth but are seen in four or five year olds and in five percent of the adult population. The etiology appears to be a stress fracture of the pars in those with some genetic predisposition. Most children with this problem present at age ten or older and there is a higher incidence in those engaged in gymnastics, dance, or football. The presenting complaint is low back pain aggravated by activity and relieved by rest. The physical exam may be benign. Suspicious findings would include a palpable step-off in the lower lumbar area and marked hamstring tightness flattening the lumbar spine and limiting forward flexion. A lateral x-ray showing a slip or an oblique x-ray showing a pars defect is definitive. Treatment consists of an exercise program to strengthen abdominals and gluteals and diminished physical activity initially, followed by a brace or cast if indicated. If symptoms are severe and persistent, especially in the presence of a significant or progressive slip, posterior spinal fusion is indicated.

2. Scheuermann's Kyphosis. Scheuermann's disease is a fixed and abnormal kyphosis of the spine caused by vertebral wedging. It most often occurs in the thoracic area. The etiology is unknown. The major presenting complaint is poor posture and it is frequently accompanied by a dull, aching, fatigue type pain over the deformity which is worse with activity and relieved by rest. The physical exam shows an increased thoracic kyphosis and lumbar lordosis with an actual angulation seen over the thoracic area when the patient forward bends and is viewed from the side. When standing, the head and neck are often thrust forward(Fig. 1-A). This condition is differentiated from postural round back by the lack of correction of the kyphosis when the back is extended. The lateral x-ray is definitive if it shows anterior wedging of five degrees or more over three adjacent vertebrae and a kyphosis of more than fifty-five degrees. Treatment for pain is back exercise and diminished activity. Severe deformity is managed with a Milwaukee brace and/or spinal fusion (Fig. 1-B).

3. Idiopathic Scoliosis. Idiopathic scoliosis is not a cause of back pain in children.

Inflammatory Processes
1. Disc Space Calcification. This process usually results from a nonspecific inflammatory reaction. The average age of onset is seven years and it is more common in males. Pain, spasm, and local tenderness are the presenting symptoms. Elevated temperature, sedimentation rate and WBC often occur. Calcification in the disc space is seen on x-ray within two weeks of the onset of symptoms. This is a self limiting condition which resolves with rest and immobilization.

2. Disc Space Infection. This problem is usually seen in younger children - average age of six years. The infection is carried to the disc space by the blood supply of the adjacent vertebral body. The diagnosis is difficult and often delayed. These children present with severe or dull low back pain which may be accompanied by hip and abdominal pain. They are listless, irritable and anorexic. They may limp or refuse to walk. There is diminished back motion and tenderness over the involved area. The sedimentation rate is elevated and the WBC most often normal. Blood cultures are usually negative. No x-ray changes are seen early but, eventually, disc space narrowing and end plate irregularity are noted (Fig. 2). The diagnosis is usually based on the physical, the laboratory, and x-ray findings Initial treatment consists of antibiotics plus bed rest or a body cast for six to twelve weeks. If the symptoms do not regress, aspiration, and culture are indicated. Cultures from the aspirate are positive in twenty five percent of cases, usually growing out staph aureus.

3. Vertebral Osteomyelitis. This condition presents in very similar fashion to discitis but in an older patient. Once again there is a complaint of severe or dull low back pain, malaise, and low grade fever. There is localized tenderness over the involved area of the spine with splinting and guarding. Lab tests show an elevated WBC and sedimentation rate. Blood cultures are positive in fifty percent of cases. Early bone scan will be positive and late x-ray changes include vertebral collapse and abscess formation. Early treatment is with bed rest and antibiotics. Surgical exploration may be required for biopsy, drainage, and spine fusion for late, established cases.

4. Rheumatic Disorders. Juvenile rheumatoid arthritis most often affects the cervical spine. However, ankylosing spondylitis often presents with low back pain and stiffness in boys over age eight years. The back is stiff with a loss of lumbar lordosis. Restricted chest expansion is noted. There is often an elevated sedimentation rate and the HLA-B27 is reported to be positive in fifty to ninety percent of cases. Treatment is symptomatic.

5. Iliac Osteomyelitis and Sacro-lliac Joint Infection. These problems often present with gradual onset of dull low back pain, often one sided, with radiation to the buttock and thigh. Physical exam reveals tenderness over the involved area as well as pain with straight leg raising and pelvic compression. The diagnosis is made by aspiration or biopsy and treatment consists of antibiotic therapy and rest.

Neoplastic Disease
1. Vertebral Column. Bone tumors involving the vertebral column are rare in children. Patients usually present with back pain which is worse at night and unaffected by rest or activity. Physical exam often reveals scoliosis and some localized tenderness. The diagnosis is made radiographically. Changes are frequently seen in the spinous processes, transverse processes or the pedicles. Eventually, vertebral collapse may occur. A bone scan will frequently be positive before changes are seen on the plain films. The differential diagnosis is given in Table l. Eosinophilic granulorna is often associated with total collapse of a vertebral body. Osteoid osteoma is characterized by severe night pain relieved by salicylates. Treatment depends upon the specific diagnosis.

2. Spinal Canal. Half of the reported cases of tumors in the spinal canal occur before age four. They are associated with neurologic change in deep tendon reflexes, sphincter tone, and sensation. X-rays may show widening of the spinal canal or erosion of bony structures. CT or MRI scans or myelography are definitive. There is increased protein in the cerebro spinal fluid and cytology may be positive. Treatment is excision if possible. Differential diagnosis is given in Table l.

1. Mechanical Derangement
   A. Poor Posture
   B. Muscle Strain- Overuse Syndrome
   C. Herniated Nucleus Pulposus
   D. Acute fracture - Pars
2. Developmental Abnormality
   A. Spondylolysis/Spondylolisthesis
   B. Scheuermann's Kyphosis
3. Inflammutory Process
   A. Disc Space Calcification
   B. Disc Space Infection
   C. Vertebral Osteomyelitis
   D. Rheumatic Disease
   E. Iliac Osteomyelitis/Sacro-lliac Joint Infection
4. Neoplasm
   A. Vertebral Body
      1. Primary
            a. Eosinophilic Granuloma
            b. Osteoid Osteoma
            c. Osteoblastoma
            d. Aneurysmal Bone Cyst
            e. Giant Cell Tumor
            f. Hemangioma
      2. Metastic
            a. Wilm's Tumor
            b. Neuroblastoma
      3. Spinal Canal
            a. Glioma
            b. Teratoma
            c. Lipoma
            d. Neurofibroma
            e. Ependymoma
   B. Psychogenic

Conversion Reactions
Children sometimes respond to stress with physical symptoms. This is often a diagnosis of exclusion. In such cases, the child will present with negative physical findings and a history suggestive of psychological problems. Psychological or psychiatric consult would be indicated.

Summary
Back pain is an uncommon complaint in children, often caused by serious spinal pathology. Muscle strain and conversion reactions are much less frequent than in adults and these diagnoses should be made with great care after ruling out other diagnosable conditions. In the presence of a normal physical exam, x-ray of the spine, and lab survey, it E permissible to treat back pain conservatively. If the symptoms persist, a bone scan, CT scan, or myelography may be indicated.