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Biomedical subjects

W H Harris

Publications and source records attributed to W H Harris.

At least 271 records · Page 15Linked to original sources
PubMed1986

Greenfield vena caval filter for management of selected cases of venous thromboembolic disease following hip surgery. A report of five cases.

The use of the Greenfield vena caval filter for thromboembolic disease following major hip surgery is an important part of the orthopedist's armamentarium for treatment of complications or contraindications to standard anticoagulation therapy. The authors report five cases in which a Greenfield vena caval filter was employed for treatment of a femoral thrombus or pulmonary embolism in postoperative hip patients who developed bleeding complications from heparin, had a recurrent embolism while on heparin, or who had had a contraindication to anticoagulation therapy.

Aged↗
PubMed1985

Evidence for a contribution by brown adipose tissue to the development of fever in the young rabbit.

This study was undertaken to determine if brown adipose tissue was involved in heat production during fever produced by S. abortus equi (1 micrograms) in unanesthetized rabbits aged 19-26 days. The fever (0.9-1.6 degrees C) occurred after a delay of 20-30 min and was frequently biphasic. Radiolabelled microspheres for measuring tissue blood flow were injected intraventricularly into three groups of animals: rabbits not given pyrogen, rabbits in which the febrile response to pyrogen was developing, and rabbits in which the febrile response had peaked. Blood flow to brown fat deposits and other organs was calculated from the fractional distribution of the microspheres and the recovery of microspheres in a reference arterial blood sample. At the fever peak, blood flow to brown fat was not significantly different (p greater than 0.05) from the control value (0.9 +/- 0.2), but during the rising phase of the fever the flow increased significantly (p less than 0.01) to 2.6 +/- 0.4 mL min-1 g-1. The blood flow to muscles of the forelimbs and hind limbs was also increased significantly (p less than 0.05) during the rising phase of the fever. No significant change in blood flow to other organs or tissues was found during the rising phase of the fever. These results indicate that both nonshivering as well as shivering thermogenesis contribute to heat production during development of fever in the young rabbit. However, nonshivering thermogenesis was not involved in the maintenance of the elevated body temperature after the fever had peaked.

Adipose Tissue, Brown↗
PubMed1985

The relationship between the thermogenic response of brown adipose tissue and age during noradrenaline infusion in the young rabbit.

This work was undertaken to determine if the thermogenic activity of brown fat decreased with age in young rabbits despite the morphological evidence indicating persistence of the brown adipocytes at 4 weeks of age. Data obtained by infusing five doses of noradrenaline and measuring oxygen consumption were used to construct cumulative dose-response curves for five age groups between 3 and 32 days of age. Blood flow to brown fat and other tissues was measured by the microsphere method at 1 and 3 weeks of age. The noradrenaline-induced increase in oxygen consumption when expressed as a percentage of resting oxygen consumption in millilitres per 100 g of body weight decreased (p less than 0.05) with age. However, the absolute noradrenaline-induced increase in metabolic rate (millilitres per minute) increased with age. Total blood flow to brown fat (millilitres per minute) during noradrenaline infusion was unchanged between 1 and 3 weeks of age, but when the blood flow was expressed in millilitres per minute per gram of tissue flow decreased significantly (p less than 0.05) probably because of infiltration of brown fat with white fat. These data suggest that the amount of brown fat and its thermogenic capacity remain relatively constant between 1 and 3 weeks of age, but as a thermogenic organ, brown fat becomes proportionally less effective with age because of the large increase in body mass.

Adipose Tissue, Brown↗
PubMed1985

Prophylaxis of deep-vein thrombosis after total hip replacement. Dextran and external pneumatic compression compared with 1.2 or 0.3 gram of aspirin daily.

The efficacy of three prophylactic regimens against deep venous thrombosis was assessed in 135 patients who were more than thirty-nine years old and had a total hip replacement. The three regimens were 1.2 grams of aspirin daily, 0.3 gram of aspirin daily, and external pneumatic compression of the calf and thigh combined with low-molecular-weight dextran that was given for three days, beginning during the operation. In all patients, detection of fresh thrombi was by the fibrinogen-uptake test, cuff-impedance plethysmography, and venography. New venous thromboses developed in twenty-nine of forty-eight patients receiving 1.2 grams of aspirin and in twenty-six of forty-three receiving 0.3 gram of aspirin, indicating that the lower dose of aspirin had no advantage. Thromboembolic disease developed in only nine of forty-four patients who were on the regimen of external compression and dextran. This combination was significantly better than aspirin in both men and women. Dextran appeared to be associated with excessive bleeding when given in doses of more than 500 milliliters during the operation, but not when given in less than that amount.

Aspirin↗
PubMed1985

A method of intraoperative limb length measurement in total hip arthroplasty.

Equalization of leg-length discrepancy during total hip arthroplasty is a major concern to both the patient and surgeon. A stable pelvic reference point must be established during surgery to determine leg-length changes. An accurate method of intraoperative leg-length measurement is presented to improve the surgeon's ability to determine the exact amount of limb lengthening or shortening occurring during total hip arthroplasty.

Anthropometry↗
PubMed1984

Changes in long-bone structural properties during the first 8 weeks of plate implantation.

The midplate structural rigidities of metal- and plastic-plated intact canine femora were experimentally determined after initial plate application and 8 weeks after in vivo implantation. Composite beam theory significantly overestimated the bending rigidities of the metal-plated bones. The rigidities of the plastic-plated bones were nearly identical to that of the isolated bone, as composite beam theory predicted. Plating with either plate increased the intracortical porosity and caused the deposition of periosteal new bone, which was greater with plastic than with metal plates. The increased rigidities provided by the attachment of the metal plates and, hence, the degree of bone strain shielding were variable. Platings for 8 weeks which provided little strain shielding with either metal or plastic plates caused an increase in bone flexural rigidity (measured after plate removal) with respect to the contralateral control. Platings that provided increasing amounts of strain shielding caused a decreasing midplate bone rigidity (measured after plate removal) and increasing bone deposition at the outer screws. These findings suggest that the surgical implantation of any plate (metal or plastic) will provide a net stimulus to bone formation and consequently increased bone structural rigidity, even though intracortical porosity is increased. If the plate significantly reduces the normal loads borne by the bone, however, there is a net stimulus to remove bone, resulting in a loss of midplate structural rigidity within 8 weeks of implantation.

Animals↗
PubMed1984

Stress changes in the femoral head due to porous ingrowth surface replacement arthroplasty.

Finite element stress analyses were conducted of the canine femoral head before and after implantation of various surface replacement-type components. The femoral head was replaced by four implant geometries; (a) shell, (b) shell with peg, (c) shell with rod, and (d) a new epiphyseal replacement design. All implants were modelled to simulate bony ingrowth along the underside of the shell and along the surfaces of the peg and rod. The results indicated that in the normal femur the forces are transferred from the articular surface through the femoral head cancellous bone to the inferior cortical shell of the femoral neck. After shell-type surface replacement, forces were transferred more distally at the rim of the shell and at the end of the peg or rod, thereby reducing the stresses in the proximal head cancellous bone. Computer simulation of bone remodelling due to proximal bone stress reduction was shown to accentuate the abnormality of the stress fields. Surface replacement with a lower modulus material created a less abnormal redistribution of bone stresses. The new epiphyseal replacement design resulted in stress distributions similar to those in the normal femoral head and minimal shear stresses at the implant/bone interface. These findings suggest that the epiphyseal replacement concept may provide better initial mechanical integrity and create a more benign milieu for adaptive bone remodelling than conventional, shell-type surface replacement components.

Acetals↗
PubMed1984

Medial-displacement intertrochanteric osteotomy in the treatment of osteoarthritis of the hip. A long-term follow-up study.

Of seventy-three adults who were treated for osteoarthritis of the hip by medial-displacement intertrochanteric osteotomy done by one of us, sixty-one (with sixty-seven treated hips) could be evaluated twelve to fifteen years after osteotomy or at the time when they had an arthroplasty for recurrent symptoms. Specific criteria based on preoperative data were used prospectively to categorize the hips as to their suitability for medial-displacement osteotomy. In addition, at the conclusion of the study, an osteotomy suitability score (maximum score, 12 points) was assessed retrospectively as a determinant of suitability for medial-displacement osteotomy. Ten years after the osteotomy, thirty-four (51 per cent) of the sixty-seven hips had been treated with a cup arthroplasty or total hip arthroplasty. At the conclusion of the study (between twelve and fifteen years after osteotomy), forty-four (66 per cent) of the sixty-seven hips had had an arthroplasty. Among the sixteen hips that had been considered excellent candidates according to the prospective criteria, 85 per cent had not yet required hip arthroplasty five years after osteotomy and two-thirds had not had an arthroplasty ten years after surgery. Of the thirty hips with a suitability score of 7 points or more, 85 per cent had not required arthroplasty at five years and 67 per cent had not done so at ten years. The numerical scoring therefore appeared to be a more reliable determinant of suitability.

Aged↗
PubMed1984

Detection of pulmonary emboli after total hip replacement using serial C15O2 pulmonary scans.

15-O-labeled carbon dioxide (C15O2) was used for the detection of preoperative and postoperative pulmonary emboli in seventy-three patients, more than forty years old, who had undergone a total hip replacement. When the C15O2 scan was suggestive of pulmonary embolism, it was followed by conventional perfusion and ventilation (V/Q) scans. If these also suggested the presence of embolism, pulmonary angiography was done. Three different prophylactic agents against venous thromboembolic disease had been used in the seventy-three patients. Seventeen (23 per cent) of the seventy-three patients had a positive C15O2 pulmonary scan followed by a positive ventilation-perfusion scan and a positive pulmonary angiogram that showed pulmonary emboli. Fourteen (83 per cent) of these patients with proved pulmonary emboli were asymptomatic. Fifteen additional patients also had a positive C15O2 scan. However, twelve of them had either negative ventilation-perfusion scans or chest radiographs that demonstrated atelectasis, and did not have a pulmonary angiogram. Three patients with a positive C15O2 scan had a negative pulmonary angiogram. Two of them had a ventilation-perfusion scan that was interpreted as showing probable pulmonary emboli, and the remaining patient did not have a ventilation-perfusion scan. Forty-six per cent of the patients with positive C15O2 scans did not have pulmonary emboli. This sensitive and readily repeatable test provides an excellent means of detection of silent emboli, an improved method of evaluating the efficacy of prophylactic agents, and the opportunity to correlate the site, size, and onset of deep-vein thrombosis with pulmonary emboli in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Ultrastructural study of developing rabbit diaphragm.

Diaphragms obtained from forty rabbit fetuses during the last third of gestation and from five rabbits one week old were studied ultrastructurally. Four gestational ages were chosen for the investigation. The diaphragm at 20 days gestation revealed early myogenesis which was characterised by many myogenic cells in the process of mitosis and by fusion of myoblasts to form myotubes. A large number of lipid droplets and a moderate quantity of glycogen were observed in the myotubes. These myotubes contained a few myofibrils peripherally. At 22 days of gestation, the myotubes exhibited a relatively large number of myofibrils and large amounts of glycogen. They also showed sarcolemmal modifications which appeared to be developing motor end plates. Mitosis of the myogenic cells persisted even after fusion. At 25 days of gestation, connective tissue sheaths appeared around the muscle fibres as well as further differentiation of the muscle fibres. At 30 days of gestation, the muscle fibres exhibited nearly complete differentiation, with the formation of myotendinous junctions. At one week post partum, the diaphragm showed full development of its muscle fibres. These morphological observations suggest a very rapid functional differentiation of the rabbit diaphragm during the last third of gestation.

Animals↗
PubMed1984

Comparative fatigue behavior of different bone cements.

Tensile and fatigue studies were performed on four different preparations of acrylic bone cement: (1) surgical Simplex-P inserted into molds in the dough stage, (2) Zimmer Low Viscosity Cement (LVC) inserted in the liquid phase, (3) an experimental cement inserted in the dough phase, and (4) the same experimental cement inserted in the liquid phase. The void characteristics of the cements appeared to dictate their mechanical performance. While tests revealed no difference in the tensile strengths of the four cement preparations, small but statistically significant differences in mean fatigue life were observed. The experimental cement used in the dough stage exhibited superior fatigue characteristics when compared with Simplex and LVC. LVC had the poorest mechanical properties of the four cement groups. Since the specimen preparation procedures can markedly influence the cement void characteristics and, consequently, the mechanical properties, general statements about different cement types are offered with considerable reservations.

Bone Cements↗
PubMed1984

Centrifugation as a method of improving tensile and fatigue properties of acrylic bone cement.

In this study centrifugation dramatically reduced the porosity and substantially increased the mechanical properties of bone cement. Monotonic tensile tests to failure of centrifuged specimens of cement demonstrated an increase of 24 per cent in the mean ultimate tensile strength compared with the control value. Mean ultimate tensile strain was improved by 54 per cent. In fully reversed tension-compression fatigue-testing, centrifugation resulted in a mean increase in fatigue life of 136 per cent. These strong advantages in mechanical properties were obtained without any detrimental changes. There was no change in elastic modulus, setting time, or peak temperature. Handling properties were improved. There was no increase in systemic toxicity as demonstrated in dogs by assessment of arterial blood-pressure response and peak levels of monomer in the serum during simulated total hip arthroplasty. We also present a practical system of cement centrifugation and delivery that is suitable for use in the operating room.

Acrylic Resins↗
PubMed1984

Femoral cement pressurization during total hip arthroplasty. The role of different femoral stems with reference to stem size and shape.

Aseptic loosening is the most common cause of femoral component failure following total hip arthroplasty (THA). Improvements have been made in cementing technique, but little attention has been directed toward the effect of different femoral components on bone cement pressurization. The effect of three different femoral stem sizes in one femoral canal and of eight different femoral stem designs on bone cement extrusion pressures was investigated on autopsy specimens. In a given femur significant increases in bone cement pressurization were achieved about the distal two-thirds of the femoral component in progressing from a small to a medium to a large stem. Similarly, femoral stems with rounded, rectangular cross sections generated greater bone cement pressurization about the distal two-thirds of the stems than stems trapezoidal and diamond-shaped in cross section due to their increased stem volume. The results of this study favor the use of the largest femoral component stem, preferably one with a rounded, rectangular cross section, that will fit comfortably in a given femoral canal and still allow a surrounding cement envelope such that bone cement pressurization will be enhanced with implant introduction.

Cadaver↗
PubMed1984

Advances in total hip arthroplasty. The metal-backed acetabular component.

Detailed, long-term studies of cemented total hip arthroplasties clearly show that failure of fixation of the acetabular component is a major problem, with a rising incidence and an unusual complexity. By finite element analysis the stress distribution in the human acetabulum before and after total hip arthroplasty was analyzed by three different groups of investigators. Data from all three studies are in agreement that the introduction of cemented acetabular components of high-density polyethylene results in major disturbances of stress distribution, with peak stresses after total hip arthroplasty occurring in the cement, trabecular bone, and medial wall of the acetabulum. The most effective way to reduce these peak stresses in these three critical areas is to use an acetabular component with a metal backing. Long-term follow-up studies of 51 patients who underwent total hip arthroplasty performed by the author during the period from 1971 to 1975 using metal-backed acetabular components confirm the improved fixation that results from use of this design. Both the analytic data of stress distribution and clinical follow-up studies strongly support the use of metal-backed acetabular components in cemented total hip arthroplasty.

Acetabulum↗
PubMed1984

Failed total hip replacement: assessment by plain radiographs, arthrograms, and aspiration of the hip joint.

We reviewed a series of sixty-one revised total hip replacements in order to assess the accuracy of plain radiographs (all hips), arthrograms (thirty-one hips), and aspiration (sixty hips) in demonstrating the presence of loosening or infection. Plain radiographs correctly showed the status of the fixation of 92 per cent of the femoral components but of only 63 per cent of the sockets. They indicated loosening in only 37 per cent of the loose sockets. Arthrography improved the over-all accuracy in demonstrating the status of the fixation of the sockets to 80 per cent and increased the accurate detection of loose sockets to 89 per cent; however, it was no more useful than the plain radiographs in the assessment of the femoral components. Aspiration of the joint proved reliable in excluding the possibility of infection in fifty-nine of sixty hips. We concluded that femoral components are best evaluated for loosening by plain radiographs, but arthrography substantially improves the diagnostic accuracy for loosening of the socket. Aspiration of the joint accurately excluded sepsis as the cause of pain in all of the hips from which joint fluid was obtained.

Acetabulum↗
PubMed1983

Evaluation of bone cement failure criteria with applications to the acetabular region.

A Strain energy density (SED) criterion based on a fracture mechanics approach was used to assess the possible failure of acetabular bone cement after total hip replacement. Stress distributions in the cement at the bone-cement interface were calculated using two-dimensional finite element analyses. The results indicate that increasing the thickness of bone cement reduces the risk of cement fracture. The addition of a metal backing to the polyethylene cup and retention of the subchondral bone further reduces the risk of failure. The SED criterion was found to predict the same critical regions as zones of possible cement failure as the von Mises' criterion. Although either criterion can be used for predicting failure in this acetabular analysis both criteria are excessively conservative in predicting failure in regions where high principal compressive stresses are present. Further development of cement failure criteria are indicated.

Acetabulum↗