Environmental and human health risk assessment for essential trace elements: considering the role for geoscience.

In environmental and human health protection, the role for geoscience may be expressed by how it enhances certainty in the hazard potential models that support risk assessment. For geochemical hazards, certainty reflects how well geoscience simplifies variability in the element concentrations and in the environmental conditions associated with exposure pathways. Through mineralogy, geoscience establishes natural geochemical background variability in terms of provenance, process, and past, and it links hazard potential to the physical and chemical transformation due to weathering and soil formation. The interpretation of hazard potential may be expressed by how analytical protocol, expressed by grain size and strength of acid decomposition, combines with geological factors, expressed by (1) mineralogy and mineral partitioning and (2) environmental cofactors, including moisture, pH, buffering capacity, and porosity. With this type of knowledge, geoscience enhances the potential to identify covariant relations between hazard indicators and disease, and to resolve potential causal factors.

Variation of soil radon concentrations in southern Ontario.

Radon has been identified as the second leading cause of lung cancer after tobacco smoking. Information on indoor radon concentrations is required to assess the lung cancer burden due to radon exposure. However, radon data in highly populated southern Ontario are very limited. Since radon in soil is believed to be the main source of radon in homes, measurements of soil gas radon concentrations can be used to estimate variations in radon potential of indoor environments. This study reports a transect survey of natural background variation in soil radon levels across southern Ontario. The results indicate that radon risk could be high in some areas of southern Ontario.

Surgical treatment of Scheuermann's disease with segmental compression instrumentation.

Twenty-one patients with Scheuermann's kyphosis had surgery for progressive kyphotic deformity of 50 degrees or greater. There were six adolescents, with a mean age of 15.6 years (range, 13-17 years) and 15 young adults, with a mean age of 25.4 years (range, 18-40 years). All patients had posterior spine arthrodesis with segmental compression instrumentation. Seven patients with rigid kyphosis had combined anterior and posterior spine arthrodesis. One patient died of superior mesenteric artery syndrome. In the group of 13 patients with posterior arthrodesis only, followup was 4.5 years. The mean preoperative thoracic kyphotic curve of 68.5 degrees improved to 40 degrees at latest review, with an average loss of correction of 5.75 degrees. Junctional kyphosis occurred in two patients with a short arthrodesis: one at the cephalad end and one at the caudal end of the fused kyphotic curve. In the second group of seven patients with combined anterior and posterior arthrodesis, followup was 6 years. The mean preoperative thoracic kyphotic curve of 86.3 degrees improved to 46.4 degrees at latest review, with an average loss of correction of 4.4 degrees. Overall, there was no postoperative neurologic deficit and no pseudarthrosis. Thus, posterior arthrodesis and segmental compression instrumentation seems to be effective for correcting and stabilizing kyphotic deformity in Scheuermann's disease. Despite a long operating time, this technique provided significant correction, avoiding the development of any secondary deformity in most patients. Combined anterior and posterior spine arthrodesis is recommended for rigid, more severe kyphotic deformities.

Total hip arthroplasty with cement in patients less than twenty years old. Long-term results.

Sixty-three consecutive total hip arthroplasties were performed with cement in fifty adolescent patients from 1972 through 1980, and the results were determined after a minimum of ten years. A polyethylene cup without a metal backing and a non-modular femoral component with a collar and a fixed neck length were inserted, with use of so-called first-generation cementing techniques, in each hip. Kaplan-Meier survival analysis of all sixty-three hips demonstrated that the probability of failure (defined as revision or symptomatic loosening) increased steadily over time and reached 45 per cent after fifteen years. A number of specific variables were associated with a significantly higher probability of failure: a history of more than one previous procedure involving the hip (p = 0.0002), unilateral arthroplasty (p = 0.006), previous trauma involving the hip (p = 0.01), the absence of other disease that limited function of the ipsilateral lower extremity (p = 0.03), a high postoperative level of activity (involving moderate or strenuous manual labor) (p = 0.03), and a preoperative weight of more than sixty kilograms (p = 0.03). The probability of failure in the patients who had inflammatory arthritis (11 per cent) was significantly lower than that in those who had previous trauma involving the hip (47 per cent) (p = 0.0006). Fifty-two hips (forty patients) were followed for a minimum of ten years or until revision. The mean duration of follow-up for these fifty-two hips was 12.6 years (range, 1.6 to 18.6 years). The result was evaluated clinically and radiographically with use of the Mayo hip-scoring system and was graded as excellent in ten hips (19 per cent), good in sixteen (31 per cent), fair in one (2 per cent), and poor in twenty-five (48 per cent). Most of the poor results were due to symptomatic loosening of the acetabular component. The probability of radiographic loosening after fifteen years was 60 per cent for the acetabular component and 20 per cent for the femoral component. Radiographic evidence of polyethylene wear was associated with probable loosening of the acetabular component (p = 0.03). The findings of the present study suggest that total hip arthroplasty in adolescents should be reserved for carefully selected patients for whom alternative procedures are contraindicated or unacceptable. Fixation of the acetabular component with cement is not recommended in this setting.

Osteochondritis dissecans of the femoral head in children and adolescents: a report of 17 cases.

Osteochondritis dissecans of the femoral capital epiphysis is uncommon and is usually reported as a case report or in association with other diseases. This study reports 17 cases with the primary underlying diagnosis of Legg-Calvé-Perthes disease in seven, idiopathic in six, avascular necrosis following trauma in three, and avascular necrosis with previous infection in one. Twelve cases had long-term follow-up. Two cases in which no surgery was performed were followed for an average of 12.5 years; 10 cases in which surgery was performed were followed for an average of 16.1 years. Excision of the osteochondritis fragment was performed in six cases. It was necessary only to dislocate the hip to excise the lesion in five cases. No morbidity resulted from temporary surgical dislocation. Excision of the osteochondritis dissecans fragment allowed these six patients to return to fairly normal living during the time of follow-up.

Arthrodesis of the cervical spine for fractures and dislocations in children and adolescents. A long-term follow-up study.

Forty-two patients who had had an arthrodesis for instability of the cervical spine resulting from trauma were followed clinically for a minimum of seven years (median, seventeen years and six months). The ages of the patients at the time of the injury ranged from one year and eleven months to fifteen years and eleven months. On the basis of a new post-traumatic neck score, which includes an assessment of pain, mobility, neurological status, and function, thirty-two patients (76 per cent) had an excellent result, six (14 per cent) had a good result, and four (10 per cent) had a fair result. No patient had a poor result. There was no notable deterioration of the clinical result with an increased duration of follow-up. Current radiographs of the cervical spine in flexion and extension were available for thirty-one (74 per cent) of the forty-two patients. There was no change in stability, deformity, or the fusion mass after healing or with an increased duration of follow-up, but there was a significant increase in osteoarthrotic changes in the unfused segments of the cervical spine after an increased duration of follow-up (p = 0.0001). Complications included spontaneous extension of the fusion mass in sixteen patients (38 per cent), mild pain or dysesthesias at the iliac-crest donor site in six patients (14 per cent), superficial infection at a bone-graft donor site in one patient (2 per cent), an incorrect level of arthrodesis in one patient (2 per cent). One patient had instability secondary to juvenile rheumatoid arthritis, which developed after treatment of the original injury, and she needed a reoperation. We concluded that spinal arthrodesis for fractures and dislocations of the cervical spine in children and adolescents can be accomplished safely, with an acceptable clinical outcome, a low rate of complications, and minimum morbidity after long-term follow-up. Pain, neurological status, and function do not change markedly, but mobility may decrease with an increased duration of follow-up. Our patients had a decrease in mobility, associated with an increase in osteoarthrotic changes, as seen on radiographs (p = 0.05).

Acute fractures and dislocations of the cervical spine in children and adolescents.

We reviewed the records of 143 patients, two months to fifteen years old, who were seen at the Mayo Clinic between 1950 and 1991 because of an injury to the cervical spine. There was a clear demarcation between the characteristics of the injury of two age-groups. Children who were less than eleven years old had fewer injuries as a group, were most often injured in falls, tended to have a predominance of ligamentous injuries of the cephalic portion of the cervical spine, and had a high rate of mortality as a consequence of injury to the spinal cord. Children who were eleven through fifteen years old had more injuries as a group, were most often injured during sports and recreational activities, had a higher male-to-female ratio, were more frequently injured in the caudal portion of the cervical spine, and had a pattern of injury similar to that of adults. The age and sex-adjusted incidence was 7.41 per 100,000 population per year.

Giant-cell tumours of the spine.

Between 1955 and 1989 we treated 24 patients (17 women and seven men) with giant-cell tumours of the spine at the Mayo Clinic. Their mean age was 30 years and the mean follow-up time was 12.4 years. Pain was the presenting symptom in all and half had a neurological deficit. The cervical, thoracic, and lumbar spines were equally involved. The tumours recurred in five of the 14 patients treated by one-stage surgery and in five of the ten treated by two-stage surgery. Seven patients received adjuvant radiotherapy, one for the primary lesion and six for recurrent lesions. Surgical management was by curettage or en bloc excision depending on the location and the extent of the tumour. Because of the risk of sarcomatous transformation, radiation therapy should be reserved for patients with incomplete excision or for those with local recurrence.

Treatment of hallux valgus in adolescents by the chevron osteotomy.

Between 1978 and 1984, 20 adolescent patients underwent 35 chevron osteotomies of the first metatarsal for correction of painful hallux valgus. After an average follow-up of 64 months, 85% of the patients expressed overall satisfaction. The cosmetic effect was the most satisfactory result (90%), followed by relief of pain (85%) and lack of limitations in footwear (65%). Radiographic evaluation did not seem to correlate with the final clinical result. The chevron osteotomy is a reasonable operative procedure for correction of hallux valgus in adolescents.

Lumbar radiculopathy after spinal fusion for scoliosis.

In 184 patients with no preoperative neurologic deficit who underwent operation for idiopathic scoliosis, somatosensory evoked potential monitoring was used. Four patients had neurologic deficits postoperatively. Two patients developed mild signs of intraspinal lesions involving upper motor neurons at high lumbar levels that resolved over 3-5 months. These patients and two others developed evidence of unilateral, moderate, lower motor neuron damage that was confirmed on electromyography. No changes in somatosensory evoked potentials occurred in these patients. Lumbar root damage may be difficult to recognize after operation and should be considered in patients with neurologic deficit after scoliosis surgery.

The effects of intraoperative blood salvage and induced hypotension on transfusion requirements during spinal surgical procedures.

Spinal surgical procedures, such as placement of Harrington rods for correction of scoliosis, are associated with considerable perioperative blood loss and, hence, with the risks associated with homologous blood transfusions. To test the hypothesis that intraoperative autologous blood transfusions could decrease the amount of homologous blood needed in such operations, we conducted a two-part study: (1) a retrospective review of 142 patients in whom blood salvage was not used and (2) a prospective review of 28 patients who received autologous transfusions. Intraoperative autologous transfusion reduced the amount of homologous blood required by more than 50% (5.1 versus 2.0 units; P less than 0.001). The total amount of homologous blood required during the hospital stay was also significantly reduced by intraoperative autologous transfusion (6.0 versus 3.4 units; P less than 0.001). Induced hypotension in 81 of the 142 patients who did not receive autologous transfusions did not decrease the homologous blood transfusion requirements from those needed by the normotensive patients. We conclude that intraoperative autologous transfusion significantly reduces the need for homologous blood products in patients who undergo spinal surgical procedures. Induced hypotension, which did not affect transfusion requirements in our study, should be further evaluated in a blinded, prospective study.

Blount disease: a review of the English literature.

A review of the English literature on Blount disease (osteochondrosis deformans tibiae; tibia vara) revealed that two forms of the disease, infantile and adolescent, are recognized. The cause of Blount disease is probably multifactorial. Most recent evidence on the pathogenesis implicates mechanical factors. The diagnosis can be difficult in very young children and must be based on history, physical examination, and radiographic findings. A proximal tibial metaphyseal-diaphyseal angle of greater than 11 degrees should be observed carefully for the development of Blount disease. Both nonoperative and operative treatment has been used successfully.

Congenital annular constricting bands: review of the literature and a case report.

Conditions associated with congenital annular constricting bands include autoamputation, acrosyndactyly of the hands and toes, clubfeet, lymphedema, pseud-arthrosis, and nail deformities. The association of congenital annular constricting bands and angular deformities of long bones is exceedingly rare. Reported is one such case treated with fibrous release and crescentic osteotomy.

Osteoid-osteoma and osteoblastoma of the spine.

Thirty-one patients with osteoid-osteoma and eleven patients with osteoblastoma of the spine were evaluated after operative excision of the tumor. The average duration of symptoms in the seventeen patients whose tumor had been diagnosed by technetium bone-scanning was twelve months, as compared with thirty-five months in the twenty-five patients who had been diagnosed without the aid of bone-scanning. There were no false-negative bone scans. Scoliosis was present in fourteen of eighteen patients with a lumbar lesion, in ten patients with a thoracic lesion, and in two of the twelve patients with a cervical lesion. Twelve of the twenty-six patients with scoliosis had had symptoms for less than fifteen months before diagnosis (Group A), and eleven had had symptoms for more than fifteen months (Group B). The duration of symptoms was unknown in the other three patients. Eleven of the twelve patients in Group A had a decrease in or complete correction of scoliosis after excision of the tumor, whereas ten of the eleven patients in Group B had no decrease in the pre-operative scoliosis.

Myositis ossificans of the upper extremity: a long-term follow-up.

The long-term results of nonoperative treatment of myositis ossificans traumatica have been infrequently reported. We reviewed 83 cases of myositis ossificans seen at the Mayo Clinic from 1950 to 1979 in patients up to 21 years of age. The upper extremity was involved in 31 patients. Follow-up averaged 13 years for 23 of the (74%) patients studied. Football injuries had occurred in 20 of these patients, and the diagnosis was made an average of 3.3 weeks from the time of the initial injury. Observation was the only treatment in 18 of the 31 cases. At follow-up two-thirds of the patients with upper extremity involvement had no problems associated with the disorder, and one-third described some difficulties. Nonoperative treatment remains an accepted management approach for this problem.

The use of computerised tomography in dislocation of the hip and femoral neck anteversion in children.

Computerised tomography is useful in the diagnosis of abnormalities of the hip in children, particularly in assessing the size and shape of the acetabulum, the position and congruity of the femoral head relative to the acetabulum, and the degree of femoral anteversion or retroversion. It is most useful when limited hip movement and previous operations preclude adequate clinical examination and assessment by routine radiographic techniques. It is not recommended for routine use in screening congenital dislocation of the hip or in diagnosis or follow-up of Perthes' disease or slipped capital femoral epiphysis.

Total joint arthroplasty. Applications in children and adolescents.

Sixty total hip arthroplasties were performed in 47 severely disabled children and adolescents. Follow-up was from 1 to 5 years. The complication rate was 22%. Loss of the prosthesis occurred in only one patient, who had had multiple operations. Eighty-five percent of these patients had good to excellent results.

Cup arthroplasties in teen-agers and children.

Review of cup arthroplasties performed prior to 1970 in sixty hips of fity-one consecutive patients less than twenty years old, with follow-up on fifty-three hips, revealed that fifteen (28%) of the cup arthroplasties were followed by other salvage operations, usually total hip arthroplasty. Of the remaining thirty-eight hips, only twenty-four (63%) were rated satisfactory clinically, although most of the patients considered their cup arthroplasty an improvement over their preoperative status. Patients with bilateral hip disease did very poorly, and results were inconsistent in others. The final range of motion was frequently poor. Results were improved in hips in which acetabular reaming was not required.