Biomedical subjects
R A Dickson
Publications and source records attributed to R A Dickson.
Surgical treatment of late-onset idiopathic thoracic scoliosis. The Leeds procedure.
Late-onset idiopathic scoliosis is associated with a rib hump in the thoracic region, and surgery is indicated when this deformity becomes unacceptable. Fifty patients with this deformity were treated by the Leeds procedure, which consists of segmental wiring to a kyphotically-contoured square-ended Harrington rod; this procedure not only derotates the spine but restores the natural thoracic kyphosis, thus avoiding subsequent buckling. All patients were followed up for a minimum of two years. Forty-two of these, who had a pre-operative Cobb angle of less than 60 degrees, were treated by one-stage instrumentation and fusion, while the remaining eight with greater curves underwent preliminary anterior multiple discectomy to provide flexibility with shortening. Postoperative loss of correction was not observed and there were no neurological complications.
Vertebral shape in the median sagittal plane in idiopathic thoracic scoliosis. A study of true lateral radiographs in 150 patients.
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The anatomy of spinal deformity: a biomechanical analysis.
The essential lesion in idiopathic scoliosis is a lordosis at the curve apex. For the rotational instability provided by a lordosis to progress, asymmetry must be present in another plane. A biomechanical analysis of spinal shape demonstrates a delicate balance between the median, transverse, and coronal planes. The normal cervical and lumbar lordosis which are inherently rotationally unstable are protected by: a) prismatic shaped vertebral bodies with their bases anterior, b) considerable available intersegmental flexion, and c) powerful posterior soft tissue support. In contrast, the thoracic vertebral bodies are shaped as prisms with their apices anterior. This rotationally unstable configuration is protected by a kyphosis with the axis of spinal rotation situated anteriorly. The thoracic vertebral prisms are asymmetric, their apices lying to the right of the median plane. In the presence of a lordosis the apices of the prisms will be directed toward the right producing a right-sided scoliosis. Any significant degree of left-sided coronal asymmetry can override the influence of the transverse plane and therefore left-sided curves are not uncommon. Thoracic idiopathic scoliosis is located at T8/T9 and the lordosis here is often an upward continuation of the normal lumbar lordosis such that the asymmetric thoracic prisms are no longer protected.
Idiopathic scoliosis: foundation for physiological treatment.
The three-dimensional nature of the idiopathic spinal deformity has been investigated in cadaveric specimens and patients with both idiopathic scoliosis and idiopathic kyphosis (Scheuermann's disease). In both scoliotic and kyphotic deformities the essential lesion lies in the sagittal plane with apical vertebral wedging. In idiopathic scoliosis there is an apical lordosis which being biomechanically unstable rotates to the side to produce a scoliotic deformity as a secondary component. In contradistinction the kyphotic wedging process of Scheuermann's disease is mechanically stable and any associated idiopathic type scoliosis occurs above and below the region of kyphosis. When an asymmetric lordosis is created in the growing New Zealand white rabbit, a progressive lordoscoliosis is readily produced and when the thoracic kyphosis is restored the scoliotic deformity shows evidence of regression and this forms the basis of physiological treatment. In 25 patients with idiopathic thoracic scoliosis the thoracic kyphosis has been restored and this leads to enhanced correction of the deformity in all three planes.
Screening for scoliosis: the problem of arm length.
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Rib penetration of the intervertebral foraminae in neurofibromatosis.
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The experimental basis of idiopathic scoliosis.
Idiopathic scoliosis is a complex three-dimensional deformity of the spine of which the scoliotic deformity and rotation are entirely secondary to an abnormality of shape in the median sagittal plane. In the thoracic region, there is a lordosis where a kyphosis should exist. In a controlled series of animal experiments using the growing New Zealand white rabbit as the model, idiopathic scoliosis can readily be produced if an asymmetric lordosis is created in the lower thoracic spine. Neither pure lordosis nor pure scoliosis produces the progressive idiopathic deformity. In the experimental animal when the normal thoracic kyphosis is reconstituted before maturity, the idiopathic deformity spontaneously improves. This lays the foundation for a more physiologic approach to treatment.
Aetiology of idiopathic spinal deformities.
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Conservative treatment for idiopathic scoliosis.
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Stature and idiopathic scoliosis. A prospective study.
A study of 130 scoliotic children with curves measuring 10 degrees or more has been performed in order to elucidate the importance of stature, growth and development. Girls with adolescent idiopathic curves measuring 15 degrees or more were taller than girls with smaller idiopathic curves and taller than those whose scoliosis was secondary to leg-length inequality (pelvic tilt scoliosis). No differences were observed as regards growth velocity or development. The increased standing height may be genetic but the uncoiling effect of the normal kyphosis to give a flat lateral profile is a more likely cause. The familial trend in idiopathic scoliosis may therefore be explained by the genetically determined shape of the spine in the median (sagittal) plane.
Combined idiopathic kyphosis and scoliosis. An analysis of the lateral spinal curvatures associated with Scheuermann's disease.
A radiological study of 50 patients with thoracic Scheuermann's disease revealed two types of lateral spinal curvature. A total of 43 lateral curves was present in 35 of the patients. Thirteen were apical at the same level as the Scheuermann's kyphosis and were due to vertebral-body wedging in the coronal plane; these curves had a mean Cobb angle of 15 degrees, occurred with equal prevalence in boys and girls and were directed equally to right and left. Thirty curves occurred in regions of compensatory lordosis (mean 5.6 degrees) situated above or, more commonly, below the Scheuermann's kyphosis. These scolioses had a mean Cobb angle of 16 degrees, were more often convex to the right than to the left and were significantly more prevalent in girls than in boys. The presence of these kyphoses and scolioses in the same spine, separated by only a few vertebrae, emphasises the importance of the sagittal plane in idiopathic spinal deformities and strongly suggests that idiopathic scoliosis and Scheuermann's disease share a common pathological process.
Thoracic lordoscoliosis in neurofibromatosis: treatment by a Harrington rod with sublaminar wiring. Report of two cases.
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Three dimensional analysis of right thoracic idiopathic scoliosis.
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Effectiveness of braces in mild idiopathic scoliosis.
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School screening and pelvic tilt scoliosis.
5303 schoolchildren aged 10-14 years were screened for scoliosis in an epidemiological survey. 375 (7.1%) had curves of 5-9 degrees inclusive and of these 138 had scoliosis secondary to a tilt of the pelvis. Radiographic measurements showed that the pelvic tilt was due to pelvic asymmetry, leg length inequality, or both, but bore no relation to the height of the iliac crests. Pelvic asymmetry occurred more commonly in combination with leg length inequality than as an isolated finding. In order to detect idiopathic scoliosis in the thoracolumbar or lumbar region, pelvic tilt scoliosis must be identified and excluded, but this can only be done radiographically.