The desirability and applicability of simulating ecosystems.
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Ecology↗
Biomedical subjects
R S Davidson
Publications and source records attributed to R S Davidson.
Effects of punishment intensity on instrumental avoidance behavior.
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Animals↗
Operant stimulus control applied to maze behavior: heat escape conditioning and discrimination reversal in Alligator mississippiensis.
Eight alligators were trained to escape heat by traversing an 8-ft runway containing right or left approaches to a water tank. All subjects were run until they had satisfied three criteria of stable response time, after which the predominant escape path was blocked, requiring discrimination reversal. Seven subjects again met the criteria; three also met them in a second reversal.
Animals↗
Laboratory maintenance and learning of Alligator mississippiensis.
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Animals↗
The surgical management of pulmonary metastasis: current concepts.
Lung metastases have been found in 25-30% of all patients with cancer at autopsy. Those patients satisfying criteria for surgical resection represent a much smaller subgroup. Given the potentially curative nature of pulmonary metastasectomy in the absence of disseminated disease, it has become widely accepted as an important treatment option for a variety of malignancies with metastasis to the lungs. A standardized approach remains unfounded however, given limited numbers of patients, various histologic subtypes and few published studies utilizing randomized prospective methodology.Ultimately, the development of metastasis represents a major determinant of survival for patients with cancer. Pulmonary metastasectomy is an important treatment modality for patients with metastatic pulmonary disease. The indications for pulmonary metastasectomy and the surgeon's role in pulmonary metastatic disease continue to evolve. Future prospective studies and the compilation of comparable data yielding prognostic factors for specific histologies will better define indications for resection.
Humans↗
Perinatal limb ischemia: orthopaedic implications.
Fifteen patients (16 ischemic limbs) who ultimately required amputation for perinatal limb ischemia were treated at The Children's Hospital of Philadelphia and the Shriners Hospital for Crippled Children in Philadelphia between 1980 and 1993. The average birth weight of these patients was 1,870 g, and the average gestational age was 30.8 weeks. Ischemic events occurred at an average postnatal age of 5.4 weeks. The causes of the ischemia included (a) arterial thrombosis as a complication of arterial catheterization (eight patients), (b) thromboembolism resulting from a hypercoagulable state (five patients), (c) intravenous infiltrate (one patient), and (d) in utero arterial thrombosis (one patient). Amputation was required at an average postnatal age of 8.5 weeks. The final patient, with concurrent ischemia involving the right hand and left leg, had complete resolution of the ischemic hand with fibrinolytic therapy alone and required only an amputation of the lower extremity. Eleven of the 15 patients were available for follow-up (two dead, two lost to follow-up), at an average of 4.5 years. Nine of these 11 patients (six lower and three upper extremities) are functioning well in prostheses. The two remaining patients are infants who will be fitted for lower-extremity prostheses when they begin to attempt to walk.
Amputation, Surgical↗
Vascular injuries and their sequelae in pediatric supracondylar humeral fractures: toward a goal of prevention.
Between 1988 and 1994, 128 consecutive children with grade III supracondylar humeral fractures presented for treatment at our hospital. Seventeen had absent or diminished (detected with Doppler but not palpable) radial pulses on initial examination. Fourteen of these 17 children recovered pulse (palpable) after reduction and stabilization of their fractures. The remaining three had persistent absence of radial pulse. Each of these three children was explored immediately and found to have a significant vascular injury requiring repair. Two of the 14 children who had initially regained their pulses had a progressive postoperative deterioration in their circulatory status during the first 24-36 h, including loss of the radial pulse. Both of these children had arteriograms that identified vascular injuries. Both underwent exploration and bypass grafting. One of these two children had been transferred 48 h after injury, resulting in delay of management of his vascular impairment. Despite exploration, vascular repair, and fasciotomy, he ultimately developed Volkmann's ischemic contracture. All five children with significant vascular injuries had absent or diminished radial pulses on presentation. Immediate reduction and fixation followed by careful evaluation and treatment of ischemia were associated with excellent outcome in four of the five children.
Adolescent↗
Bone infarction versus infection in sickle cell disease in children.
We reviewed emergency admissions for the complaint of musculoskeletal symptoms for 113 children with sickle cell disease. Over a 2-year period, we accumulated a total of 247 admissions to a major children's hospital. Four osteoarticular infections were identified, resulting in an incidence of 1.6% per admission for musculoskeletal complaints. Admission history, physical findings, laboratory values, and radiographic studies were reviewed. We compared findings in the group with the positive diagnosis of osteoarticular infections with those who were thought to have only vaso-occlusive crisis. Although three of the four patients with infection had plain roentgenogram changes at the time of diagnosis, no statistically significant differences in the two groups could be determined.
Adolescent↗
Orthopaedic manifestations of chronic graft-versus-host disease.
Chronic graft-versus-host disease (GVHD) is a well-recognized complication of allogeneic bone marrow transplantation (BMT). Musculoskeletal manifestations include joint contractures, polymyositis, polyserositis, and fasciitis. We present 14 patients with orthopaedic complications of chronic GVHD. Long-term conservative management of joint contractures with physical therapy and orthotics was generally successful in restoring patients' premorbid functional status. Surgical release of joint contractures yielded poor results and rendered the affected joints unresponsive to further conservative treatment. Surgical intervention in the treatment of joint contractures resulting from chronic GVHD does not appear qualitatively to improve functional status in patients affected with this disease process.
Adolescent↗
Pretreatment bone scan in SCFE: a predictor of ischemia and avascular necrosis.
Sixty-two consecutive patients with 73 slipped capital femoral epiphyses (SCFEs) underwent pretreatment planar technetium bone scan to identify the presence of ischemia of the femoral head. The relationship of pretreatment ischemia and the development of avascular necrosis (AVN) was evaluated after a minimum follow-up of 12 months. All patients were treated with spica casting or pinning across the physis. No forceful manipulation was performed. None of the 63 stable SCFEs demonstrated ischemia by bone scan, and none developed AVN. Of the 10 unstable SCFEs, six demonstrated ischemia by bone scan, and five of the six developed AVN. None of the four unstable SCFEs without ischemia on bone scan developed AVN. Pretreatment bone scan is a sensitive predictor for development of AVN in unstable SCFEs and may provide a method for evaluating interventional treatments for AVN associated with SCFE.
Adolescent↗
Fibrous lesion of the distal femur associated with angular deformity.
Unilateral femoral angulation is uncommon. We describe two children with unilateral progressive distal femoral varus and limb-length discrepancy. These deformities were associated with a fibrous lesion involving the medial aspect of the distal femoral metaphysis. Both patients were 15 to 16 months old. In both, the deformity was progressive, resulting in excisional biopsy and osteotomy. The gross and microscopic appearance of both lesions was similar, and the histology was dense fibrous connective tissue. The patients' femoral alignment was maintained at follow-up of a minimum of 16-36 months. The etiology of these lesions is unknown; they are associated with progressive deformity and appear to respond well to surgical intervention.
Biopsy, Needle↗
Slipped capital femoral epiphysis: an analysis of 80 patients as to pin placement and number.
A retrospective study of 80 patients with chronic slipped capital femoral epiphysis was performed, analyzing the clinical results with regard to pin placement and pin number. Follow-up averaged greater than 2 years, with 86% of the 80 patients obtaining a satisfactory clinical outcome. Serious complications occurred in 10 patients. The severity of complications increased as the number of pins used increased (p less than 0.07). A varus pin position resulting in a more inferior pin placement in the proximal femoral epiphysis was found to be associated with the fewest complications. When the pin tip avoided the superior and anterior quadrants in the proximal femoral epiphysis and was greater than 2.5 mm away from subchondral bone, the complication rate was decreased (p less than 0.003).
Adolescent↗
Complex femur fractures in children: treatment with external fixation.
External fixation was used to treat complex femur fractures in 10 children. These injuries were associated with head trauma, cerebral palsy, epidermolysis bullosa, open wounds, and failed casting. The duration of external fixation averaged 8 weeks, and the mean follow-up was 5 years 8 months. At follow-up, one patient had 2.6 cm of residual shortening, and two had overgrowth. Complications included one refracture. Three children developed superficial pin site drainage. Although most femur fractures can be treated with traction or casting, external fixation may simplify overall care in children with multiple injuries and is effective in controlling unacceptable femoral shortening and angulation.
Child↗
Acute osteomyelitis in children: a review of 116 cases.
We reviewed 116 cases of acute hematogenous osteomyelitis (AHO) (without septic joints) from 1979 to 1985 to establish current patterns of clinical presentation, modes of treatment, and success of therapy. We found that patients present early in the course of their disease, and many have no findings other than local tenderness and an elevated sedimentation rate. Sixty-four of the patients were treated nonoperatively. The average antibiotic treatment time was 2 weeks by intravenous (i.v.) administration followed by additional outpatient oral therapy for periods of up to 4 weeks. This treatment regimen applied specifically to acute osteomyelitis led to no known treatment failures.
Adolescent↗
Failures of pin removal after in situ pinning of slipped capital femoral epiphyses: a comparison of different pin types.
We reviewed 75 pin retrievals after in situ pinning of 35 children with slipped capital femoral epiphysis (SCFE). Four types of pins were used. Ten pins in 8 hips could not be removed because of pin breakage or stripping. Our failure rate was significantly related to pin type and size (p less than 0.039). As compared with the expected values using the chi-square method of analysis, the noncannulated large steel pins and cannulated steel pin groups had fewer failures (p less than 0.001) as compared with the cannulated titanium and noncannulated small steel pin groups. We now avoid using cannulated titanium or noncannulated small pins in treatment of SCFE.
Adolescent↗
Neonatal fractures in myelomeningocele patients.
Neonatal fractures in all neonatal patients entering a spina bifida clinic over a 4-year period were reviewed retrospectively. Of six patients with fractures, all had thoracic or upper lumbar neurologic levels and all had significant contractures. The risk of fracture for patients with these two characteristics was 17%. Awareness of the risk of neonatal fracture and care in the handling of these children is stressed.
Birth Injuries↗
Major lower extremity lawn mower injuries in children.
Between 1983 and 1993, 16 children with 18 lower extremity power lawn mower-related injuries were treated at Children's Hospital of Philadelphia. Eleven of 16 patients (69%) were bystanders or nonoperators. The average age at injury was 4 years 9 months. Length of follow-up averaged 3 years 10 months. There was an average of 4.9 procedures per patient. Fourteen of the 18 limbs injured required eventual amputation (78%). We propose a new classification of lawn mower injuries in children. The most common injury (16 of 18 limbs) was a shredding type injury and was either intercalary or distal. The second was a paucilaceration type (two of 18 limbs). Of the four salvaged limbs, there were two shredding type injuries, and on most recent follow-up are considered to have poor results. The two patients with the paucilaceration type injuries and limb salvage are considered to have excellent results. All patients with a shredding type injury ultimately required amputation or had poor results with the salvaged limb. Limb salvage surgery was associated with prolonged hospitalizations, a higher incidence of surgical problems, a longer treatment course, and more complications than early ablative procedures.
Accident Prevention↗
MRI of focal fibrocartilaginous dysplasia.
Focal fibrocartilaginous dysplasia (FFCD) is an uncommon, benign condition associated with unilateral tibia vara in young children. The clinical, pathologic, plain film, and magnetic resonance imaging (MRI) findings of FFCD were reviewed in two children. MRI findings were virtually identical in both patients and correlated well with the plain film and pathologic findings. We believe that FFCD has a typical MRI appearance. However, FFCD also has characteristic plain film findings, and when these are present, MRI is indicated for only an atypical clinical presentation.
Fibrous Dysplasia, Monostotic↗