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Biomedical subjects

R A Dickson

Publications and source records attributed to R A Dickson.

At least 55 records · Page 3Linked to original sources
PubMed1994

The use of chloral hydrate and sodium amytal during clozapine initiation.

Sedative hypnotics are frequently a necessary adjunctive to neuroleptic treatment. The recently released antipsychotic agent clozapine poses a challenge in this regard since the manufacturer advises caution when using clozapine with patients receiving benzodiazepines. The effectiveness of alternate agents sodium amytal and chloral hydrate when initiating clozapine was evaluated in a group of 15 patients suffering from schizophrenia. These medications were observed to be both safe and effective.

Adult↗
PubMed1992

Growth beyond skeletal maturity.

Serial measurements of standing and sitting height of children show that growth continues beyond the age of skeletal maturity when judged by the fusion of the epiphyses of the hand and wrist. Most of this increase occurs in the sitting height, largely reflecting spinal growth, and may account for the known progression potential of idiopathic scoliosis beyond the attainment of skeletal maturity.

Adolescent↗
PubMed1992

The scientific basis of treatment of idiopathic thoracic scoliosis.

The three-dimensional shape of the scoliotic spine must be understood and in particular the lordotic lateral profile addressed before successful derotation can be achieved. It is important that the thoracic kyphosis be recreated, firstly so that the spine can be untwisted, and secondly to bring the thoracic spine once again behind its axis of rotation thus preventing postoperative buckling with the remainder of growth. Stiffer curves require preliminary anterior multiple discectomy with growth plate excision and reshaping of the apical vertebral bodies. The deformity rapidly collapses into himself and 75% of the total correction occurs spontaneously before the second instrumentation stage. The most rigid curves require that the spinal column be shortened at bone level and Leatherman's two-stage wedge resection is ideal for this purpose. For very young spines posterior fusion is both illogical and harmful and it is essential that the growth of the front of the spine be arrested by multiple discectomy and end-plate excision. Posterior instrumental recreation of the thoracic kyphosis without fusion in a "trolley-like" procedure allows continued posterior spinal growth.

Adolescent↗
PubMed1992

The etiology and pathogenesis of idiopathic scoliosis.

Idiopathic scoliosis is a complex three-dimensional deformity and in the thoracic region the essential lesion lies in the sagittal plane in the form of an area of inappropriate lordosis. The thoracic kyphosis is normally protected from buckling by being behind the axis of spinal column rotation but when the thoracic lordosis develops it brings the apical region anterior to this axis and thus under compression with resultant buckling failure of the spinal column. The condition of idiopathic thoracic scoliosis is the opposite to idiopathic hyperkyphosis (Scheuermann's disease), the latter being rotationally stable and not moving out of the sagittal plane. The two frequently co-exist in the same spine with thoracic hyperkyphosis above an area of lumbar lordo-scoliosis. There is a spectrum of normal lateral profile and flat backs at the one end are in danger of buckling (lordo-scoliosis) while round backs at the other end of the spectrum are in danger of being defined as Scheuermann's disease. There is no requirement for a specific pathological process. Engineers describe only two ways in which a flexible column can fall into mechanically-angular collapse (kyphosis) and column buckling (lordo-scoliosis). A number of factors favour column buckling (Euler's law) and thus the bigger a deformity the more likely it will be to continue progressing and the taller and more slender the column the more likely it will be to fail and this we see in our patients with idiopathic scoliosis. Not only is lordosis the essential lesion but it is also the primary abnormality which can be demonstrated in children before lateral curvature and rotation develop.

Adolescent↗
PubMed1991

Respiratory deficiency in experimental idiopathic scoliosis.

Clinically significant respiratory failure in a group of animals with an experimentally produced structural thoracic scoliosis was identified. A detailed physiologic investigation of their respiratory function showed that their respiratory compromise was associated with the development of a smaller and stiffer chest. Frank respiratory failure, however, was rare and seen only in animals with the most severe spinal deformities when it was also associated with a general failure to thrive. Animals with less severe deformities had little measurable restriction of pulmonary function, did not develop respiratory failure, and grew normally.

Animals↗
PubMed1991

The transverse plane deformity of structural scoliosis.

An examination of the transverse plane aspect of deformed vertebrae from specimens of both human and animal scoliosis identified a consistent pattern of intravertebral deformity. In the animal model, dynamic bone growth studies illustrated bone drift in the opposite direction to the rotation of the scoliosis, suggesting that the bone growth in the transverse plane was attempting to correct rather than produce the deformity. The observed pattern of vertebral deformity can be explained in simple terms because it obeys the standard laws of bone growth and remodeling. This observed growth pattern is consistent only with the production of idiopathic scoliosis by the rotation of a primary lordosis.

Animals↗
PubMed1990

Primary tumors of the axial skeleton. Experience of the Leeds Regional Bone Tumor Registry.

Primary tumors of the axial skeleton are rare and a survey of the Leeds Regional Bone Tumor Registry found them to constitute only 55 of the 1950 cases (2.8%). Chordoma was the most frequent tumor in the cervical and sacral regions as well as the most common diagnosis overall and osteosarcoma ranked second. Pain was the most frequent presenting symptom but over half the patients developed some neurological abnormality. In spite of treatment survival was poor in patients with malignant lesions or neurological involvement. The establishment of Bone Tumor Registries is the only way that sufficient data on large numbers of these rare tumours can be amassed to provide a valuable and otherwise unavailable source of information for research, education and service.

Adolescent↗
PubMed1989

Curve patterns in idiopathic scoliosis. A clinical and radiographic study.

We have developed a simple technique for demonstrating the sagittal profile of each rotated level of a scoliotic spine and used it to determine the patterns of lordosis and kyphosis in each of six clinical types of idiopathic scoliosis. The currently accepted classification of scoliosis is inaccurate and a modification is proposed. The three main types of scoliosis were shown to have sagittal profiles distinctly different from each other and from normal. Single structural curves had short lordotic sections at their apices, limited above and below by kyphosis. Double curves showed longer lordotic sections limited only by one area of kyphosis. Lordosis throughout the thoracic and lumbar spine was associated with triple curve patterns. The biomechanical effects of the abnormal sagittal profiles provide a simple explanation for the genesis and progression of the different types of scoliosis, and the recognition of the pattern of the sagittal abnormalities permits treatment to be designed on a sound anatomical basis for individual cases.

Adolescent↗
PubMed1989

The deformity of idiopathic scoliosis made visible by computer graphics.

We present a method of visualising spinal deformities in three dimensions using conventional radiographs and computer graphics. The shape of the spinal column can be determined from the anteroposterior and lateral radiographs and displayed in any projection. In patients with adolescent idiopathic scoliosis, the fundamental lesion, an abnormal lordosis, can be demonstrated without the need for additional views. The method is applicable to other spinal deformities and may help to elucidate their three-dimensional shape.

Adolescent↗
PubMed1989

The three-dimensional anatomy of the proximal femur in Perthes' disease.

A new method of recording the three-dimensional anatomy of the proximal femur from a single anteroposterior radiograph is described. This technique shows that in Perthes' disease the femoral head and neck are in significant anteversion and true varus. This anatomical configuration may be important in the pathogenesis and treatment of this disorder.

Child↗
PubMed1988

The aetiology of spinal deformities.

There are two types of spinal deformity, lordosis and kyphosis, and they are mutually exclusive at the same site. Lordosis is rotationally unstable and buckles to the side with growth and spinal flexion, producing scoliosis and changes in transverse plane geometry as secondary phenomena. Kyphosis is a uniplanar deformity arising behind the axis of spinal column rotation and it does not buckle. Spinal balance in the sagittal plane is delicate and in the normal child during adolescence both idiopathic scoliosis and idiopathic kyphosis can easily develop. The development and progression of spinal deformities can be explained in biological and mechanical terms. Any condition in which the critical load to the spine is reduced will favour the production and progression of a spinal deformity. Neuromuscular factors in idiopathic scoliosis are additive and not causative.

Adolescent↗
PubMed1987

Experimental structural scoliosis.

Progressive structural scoliosis in growing rabbits has been produced. Tethering the thoracic spine into the form of an asymmetric lordosis produces a slowly progressive structural scoliosis by purely mechanical means. The addition of a contralateral release of the paraspinal muscles leads to a very progressive deformity with early cardiorespiratory failure. This release, however, was performed with an electric soldering iron and subsequent study showed that in those animals with severe progressive deformity there was localised spinal cord damage. We suggest that it is this neural damage and not the muscle release which leads to rapid progression. The clinical implications are important in that neurological dysfunction seems to render the spinal column less able to resist mechanical buckling and may be the crucial factor differentiating severely progressive from more benign curves.

Animals↗