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Biomedical subjects

S I Reger

Publications and source records attributed to S I Reger.

34 records · Page 2Linked to original sources
PubMed1981

Aid for training and evaluation of handicapped drivers.

An indoor driver-evaluator and trainer-aid vehicle, developed to quantify students' ability and progress in learning to drive, is described. In general, the instrumentation for each control was built to measure operating force and elapsed time. The system consists of functional ignition and gear shift control, instrumented steering wheel, hand controls for brake and acceleration, and elapsed response time meters for each control. The controls allow the major driving functions to be evaluated in their interactive mode and the subjects to be taught using variable mechanical resistance elements. Pilot tests were made on nine tetraplegic subjects, spaced over a 4-week period for a subject. Evaluation results by the third test agreed with road evaluation for all six of the subjects who thus far have attempted licensing examinations.

Automobile Driving↗
PubMed1978

Methylmethacrylate: A study of teratogenicity and fetal toxocity of the vapor in the mouse.

To determine possible deleterious effects of methylmethacrylate vapor on mouse gestation, pregnant mice were exposed to average vapor concentrations of 1330 parts per million for two hours twice daily during Day 6 through Day 15 of pregnancy. A slight increase in the average weight of the fetuses of the exposed mothers were demonstrated but no other evidence of fetal toxicity or teratologic effects was found. During three total hip replacements, the concentration of methylmethacrylate in operating-room air never rose above 280 parts per million.

Abnormalities, Drug-Induced↗
PubMed1978

The strength of metal reinforced methylmethacrylate fixation of pathologic fractures.

Fixation of the pathological fracture in terminal patients has in the past added the trauma of an extensive surgical procedure to an already weakened patient. Intramedullary fixation with single and double rods in conjuction with polymethylmethacrylate have been compared to ascertain the effect of different loading conditions using torque and analysis under compression measurements of the strength of repair bone. Extensive intramedullary reaming can be avoided with polymethylmethacrylate. The cement effectively transmits the load from the proximal to the distal fragment. The single large rod method would be more desirable for stiffer bones while the double thin rod technique may be applicable to more flexible bones.

Animals↗
PubMed1977

Nonunion of fractures of the proximal humerus: a method of treatment using a modified Moe plate.

Treatment of nonunion of fractures of the proximal or middle third of the humerus by use of a modified Moe plate is described. We have found this treatment to produce more favorable results than other methods using either internal or external immobilization. Simple modification of an existing mechanically sound device has led to a very useful instrument for the internal fixation of this type of fracture.

Aged↗
PubMed1977

Fat-cell changes as a mechanism of avascular necrosis of the femoral head in cortisone-treated rabbits.

Large doses of cortisone were given to growing and adult rabbits over a five-month period to produce avascular necrosis of the femoral head. The cortisone caused an increase in the serum cholesterol, fatty metamorphosis of the liver, and fat emboli visible in sections of the femur and humerus. These emboli partially obliterated the microcirculation of the subchondral vessels of both femoral and humeral heads. The average diameter of the marrow fat cells also increased more than ten micrometers. This increase in cell volume might be significant because in the closed chamber of the femoral head it could increase tissue pressure, diminish perfusion, and be the mechanism for avascular necrosis induced by cortisone.

Animals↗
PubMedDate not supplied

Spinal evoked potentials from the cervical spine.

Spinal cord evoked potentials were recorded from spinous processes of the lumbar, thoracic, and cervical levels of the spinal column of normal cats in response to direct stimulation of the sciatic nerve and subcutaneous stimulation of the posterior tibial nerve. The typical primary response was altered by changes in location, magnitude, and frequency of the stimulation. Further changes in the primary response could be associated with spinal level of observation. Reduction in amplitude and decrease in signal complexity with increasing frequency of stimulus indicated the loss of the slower components of the primary response of average evoked potentials. Sharp reduction of signal amplitude and increase in latency was evident as the recording moved from L1 to C3 and C2.

Animals↗
PubMedDate not supplied

Influence of AC and DC electrical stimulation on wound healing in pigs: a biomechanical analysis.

To evaluate the effects of electrical stimulation on the mechanical properties of healing skin, 20 Hanford mini-pigs weighing 10-15 kg with trochanteric pressure ulcers were subjected to electrical stimulation. Examination of the biomechanical properties of the skin and changes in wound area and volume was done on previously wounded and healing pigskin subject to AC or DC electrical stimulation. The behavior of normal pigskin was compared to (1) denervated controls, (2) denervated AC-stimulated skin, and (3) denervated DC-stimulated skin. A denervated limb trochanteric pressure sore model developed in house permitted the use of a 6.5-mm percutaneous cancellous screw for wound formation and a 3-cm-diameter spring compression indentor to create reproducible and uniformly controlled grade 3 or higher tissue ulcers in the monoplegic hind limbs. Denervation was accomplished by right unilateral extradural rhizotomies from L2 to S1 nerve roots. Electrodes were placed 1 cm distal and proximal to the wound periphery, and wounds were stimulated 2 h/day, 5 days/week for 30 days. Dumbbell-shaped skin specimens with a length to width ratio of 3:1 were uniaxially loaded in tension until failure at an extension rate of 150 mm/min. The stiffness values for skin samples oriented parallel to the current flow were reduced by nearly half the values obtained for normal controls. Statistical differences (P < .05) were found for stress, Young modulus, and stiffness when compared to normal skin. Samples oriented in the perpendicular direction were comparable to normal skin (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

A technique for quantifying the response of seated individuals to dynamic perturbations.

A technique is presented for monitoring the seated postural stability and control of human subjects. Estimates are made of the locations of the subject's center of pressure (CP(S)) and projection of the center of mass (CM(NP)) from moment balance equations using measured force and acceleration data. The CP(S) and CM(NP) indices describe the stability of the subject, independent of the chair, even in the presence of perturbations. The measurement system was evaluated for both rigid objects and human subjects situated in a wheelchair undergoing displacement. Estimated CM(NP) was within +/-5 mm of the actual value for static loads. For human subjects, the average correlation coefficient between the estimated CM(NP) signal and that computed from video data was 0.90; however, transient overestimation of displacement was seen during subject acceleration. The technique could help to better assess seated stability in dynamic environments, such as those experienced by wheelchair users in motor vehicles.

Algorithms↗
PubMedDate not supplied

Semirigid rod fixation for long-bone fracture.

Experiments on 119 New Zealand rabbits were performed to measure healing strength of femurs. Four pairs of normal rabbit femurs were also studied in vitro by use of a four-point bending test to measure bending rigidity. Rabbit-sized octagonal cross-sectioned intramedullary rods with 12%, 20%, 50%, 75%, and 100% of femoral bending rigidity were specially prepared. For each animal, one intramedullary rod was implanted in an osteotomized femur through a standard lateral approach, with the other femur serving as a control. The results from the 12% rigidity rods were widely variable. In the 20% and 50% rigidity groups, the callus diameter was increased over the 75% rigidity group through all phases of healing. The torque ratio in this group increased up to eight weeks and then converged to the ratios of the other rigidities. The 75% rigidity group had shown increase of angular displacement up to eight weeks, while the 20% and 50% rigidity groups continued to improve and reached control strength at 12 weeks of treatment. Furthermore, the 20% and 50% groups absorbed more energy to failure in the later stage of healing than the 75% and 100% rigidity groups. Rods of 20% and 50% rigidity stimulate external callus formation and improve the stability of healing bone.

Animals↗
PubMedDate not supplied

The safety of cement fixation in the cervical spine. Studies of a rabbit model.

Immediate postoperative ambulation of patients with terminal neoplastic disease of the cervical spine can be permitted by vertebral stabilization with wire reinforced with polymethylmethacrylate. Precautions are necessary to avoid a temperature rise during cement polymerization and prevent vasular or nerve damage. Experiments on 20 rabbits and 2 human cadavers indicate that temperature at the cement-lamina interface can rise as high as 90 degrees while temperature under the intact lamina measures only 50 degrees. Precooling and insulation with Gelfoam may prevent heat injury to spinal cord.

Animals↗
PubMedDate not supplied

Cortisone induced bone changes and its response to lipid clearing agents.

Thirty-two rabbits were used experimentally to study the effect of cortisone in bone, lungs, kidneys, and liver. Cortisone does induce abnormal increases in the serum cholesterol, fatty metamorphosis of the liver and the fatty emboli of the subchondral vessels of the femoral heads. Clofibrate therapy appeared to modify the cortisone induced changes as evidenced by a lower serum cholesterol level, prevention or lessening of the increase in the marrow fat cell size. This might significantly improve microcirculation of the femoral head.

Animals↗
PubMedDate not supplied

Experimental femoral fracture immobilized by rigid and flexible rods (a rabbit model).

Experimental fractures in rabbits demonstrated that flexible intramedullary rod fixation of the midshaft long bone fracture enhances the fracture healing and may promote early mobility. When compared to rigid fixation, both excess flexibility and excess rigidity inhibited optimal fracture healing. The occurrence of angulation deformities with plastic rods also demonstrate the disadvantage of a very flexible rod.

Animals↗