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Biomedical subjects

A Nachemson

Publications and source records attributed to A Nachemson.

At least 55 records · Page 3Linked to original sources
PubMed1985

Standing and supine Cobb measures in girls with idiopathic scoliosis.

The standing Cobb measure in a group of 287 girls with idiopathic scoliosis at the start of treatment was in the mean approximately 9 degrees larger than the supine Cobb measure. This mean standing-supine difference was essentially independent of curve severity expressed by the supine Cobb measure. Because of this, when the difference was expressed as a percentage of the supine Cobb measure, the mean values of this ratio decreased substantially with increasing curve severity. The mean difference decreased only slightly with age through adolescence, indicating that spine lateral curves stiffen little as patients mature. The standard deviations in the standing minus supine Cobb differences were approximately 6 degrees in the majority of the age and severity groupings studied. Ninety-three percent of these patients had standing-supine Cobb measure differences that were between 0 degrees and 20 degrees.

Adolescent↗
PubMed1985

Lumbar spine instability. A critical update and symposium summary.

Conflicting views exist on the definition of motion segment instability, from a clinical as well as from an experimental point. Enough data are at hand, however, on normal and abnormal motion to test their validity in clinical patient material, using refined radiographic techniques. It is likely that such testing must include motion in three planes, as well as correlation to relevant measures obtained by computed tomography.

Biomechanical Phenomena↗
PubMed1984

Evaluation of the use of the argon laser in repairing rat and primate nerves.

The argon laser coagulates blood selectively, making it an adherent material. Argon laser energy is almost completely absorbed by red blood cells and does not seem to affect white nerve tissue. To demonstrate the technical feasibility of laser repair for severed nerves, we cut the sciatic nerves of rats and the median nerves of nonhuman primates and then repaired them by use of an argon laser beam delivered through a 400 microns optical fiber and handpiece that was developed in our laboratory. Autogenous blood was spread around the group of fascicles at the repair site and was then coagulated with the laser to form a minitubule around each fascicle group. Transmission and scanning electron microscopy showed that the repairs appeared technically superior to control sutured nerves and that the laser apparently had no untoward effects on either the repair site or on the control nerve. The minitubules seemed to channel the axon sprouts into the distal tubules extremely well and to prevent ingrowth of scar tissue at the juncture site.

Animals↗
PubMed1984

A locking hook spinal rod system for stabilization of fracture-dislocations and correction of deformities of the dorsolumbar spine. A biomechanic evaluation.

Existing internal fixation systems for the injured or deformed spine present problems with overdistraction and control of the contoured rod necessary for transverse forces. A locking hook spinal rod avoids these problems by using a locking cover to secure the lamina in the hook and meshing radial grooves to lock the contoured rod to both the upper and lower hooks in 6 degrees intervals of rotation. The 7-mm stainless-steel rod is 50% stronger than the 1/4-in Harrington rod and also avoids the weakening effect of the notches. Cadaver spine testing gives nearly a threefold increase in failure strength (125 +/- 17 Nm versus 44.1 +/- 2.1).

Adult↗
PubMed1983

Joint flexibilities in structurally normal girls and girls with idiopathic scoliosis.

Seven clinical measurements of joint flexibilities were made in 51 girls with untreated mild idiopathic scoliosis and 65 girls with structurally normal spines. Subject ages ranged from 10 to 16 years. Abilities to have the index finger passively extended, the wrist bent, and the elbow and the knee hyperextended, along with abilities to bend the trunk voluntarily forward and to the right and left sides, were measured. The girls with scoliosis in the mean either had the same flexibilities or were less flexible than the normal girls. The study provided no evidence that untreated mild idiopathic scoliosis occurs or progresses because of increased joint flexibilities.

Adolescent↗
PubMed1983

Long-term anatomic and functional changes in patients with adolescent idiopathic scoliosis treated by Harrington rod fusion.

One hundred patients from the Gothenburg Scoliosis Data Base were studied. They met the following criteria: (1) adolescent idiopathic scoliosis (2) completion of treatment before age 20, (3) a minimum follow-up of five years thereafter, (4) a minimum age of 22 years at final follow-up, and (5) operation performed by the senior author. Of these, 95 were personally examined. The surgical technique from 1968 to 1973 included a two-stage Harrington distraction, with fusion added at the second operation (52 patients). From 1973 to 1975, 48 patients were treated with a one-stage distraction and fusion after a week of preoperative Cotrel traction. Postoperatively, all patients were treated with a Milwaukee brace. A spinal examination and functional assessment, including a questionnaire and pain drawing, full standing anterior-posterior (AP), and lateral roentgenograms of the spine, was performed by independent observers. Eighty-five subjects without scoliosis served as a control group. The radiographic evaluation showed the usual nearly 50% permanent correction at the follow-up examination averaging nine years postoperatively. Lateral roentgenograms, however, demonstrated in 52% flattened or kyphotic cervical spines producing no significant complaints, non-significant flattening of the thoracic kyphosis, but significant lowering of the lumbar lordosis. Fifteen of the 24 patients with distal hook insertion and fusion including L4 or L5 demonstrated retrolisthesis. All had significant low-back pain. Degenerative facet joint changes and disc space narrowing was noted in 11 patients, again with a distal hook purchase in L4 or L5. Compared to the controls, the operated patients, as a group, revealed no lessened activity or back pain at any location.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Screening of children with congenital dislocation of the hip joint on the maternity wards in Sweden.

In Sweden screening for congenital dislocation of the hip joint (CDH) on the maternity wards was commenced in the 1950s. Of the estimated number of cases with CDH approximately 50% are diagnosed on the maternity wards and 80% during the first 6 months of life. Of the children "missed" at the primary screening on the maternity wards a substantial number have been premature babies treated at the intensive care unit postpartum. X-ray examination at the age of 1.5-3 months has been a helpful tool to reveal failure of early abduction treatment, which has been difficult to detect by clinical examination. Children with neonatal hip instability and a family history of CDH seem to represent a subgroup with an increased risk of failure of primary treatment and may need prolonged abduction treatment. The von Rosen splint has proved to be a reliable brace if used properly. If abduction treatment is commenced already during the first few days of life the risk for avascular necrosis is very low--1%.

Braces↗
PubMed1983

Work for all. For those with low back pain as well.

The problem of low back pain is enormous in all industrialized societies. Attempts to decrease its impact by different educational, ergonomic, or treatment methods have generally failed. The deleterious effects of long-term absence from activity and work are well known. New information is available regarding the healing time and properties of possibly diseased tissues and the actual loads on the lower back in various positions of activity and work; data are also available regarding the perception of pain, both acute and chronic, and how it can be affected by muscle activity. This new information may well serve as a basis for a new type of treatment for back pain--early, gradual, biomechanically controlled return to activity and work for the 80% of patients with back pain in whom no objective cause for the pain can be found after a thorough examination.

Acute Disease↗
PubMed1983

Mechanical effectiveness studies of lumbar spine orthoses.

Intradiscal pressures, intra-gastric pressures and myoelectric trunk muscle activities were measured in four volunteers wearing five different orthoses of three principle types, and performing six tasks. A biomechanical model was used to estimate the load on the spine in the different tasks so as to compare those tasks reliably when done with and without the orthoses. The results indicate that wearing a brace can significantly unload the trunk in some situations, but has no effect in others. Lumbar spine compression was reduced by about one-third in the task involving trunk flexion. The disc pressure values with an orthosis were lower in about two-thirds of the exercises and higher in the remaining one-third. The back muscle activity was in some experiments reduced by one-third by the use of the brace, in others it increased by the same amount. None of the orthoses raised the intra-gastric pressure significantly. No one orthosis was found to be clearly superior in mechanical effectiveness in the tasks studied.

Adult↗
PubMed1983

Surgery versus chemonucleolysis for herniated lumbar discs. A prospective study with random assignment.

The results of removal of a disc hernia at the L4/L5 level were compared with those obtained by the injection of 4000 IU (2 ml) of chymopapain (Discase) in 29 consecutive patients randomly selected for either treatment. All exhibited severe incapacitating sciatica, and all had a myelogram demonstrating a definite disc hernia. The two groups of patients did not differ significantly with regard to age, sex, or length of history. The total time of general anesthesia was significantly shorter for the injected patients by 20 minutes (p less than 0.01), as was the length of hospitalization, by three days (p less than 0.05). Within five months, eight of the patients receiving chymopapain injections had to be operated on because of unrelieved symptoms. All had definite disc herniae, and in four, a free fragment was found. All patients were seen at the time of dismissal from the hospital and at six and 12 months after operation by an independent observer. Comparisons made at these intervals, following either surgery or chymopapain injection with or without subsequent surgery, did not reveal any significant differences, but the short-term results following either treatment alone significantly (p less than 0.01) favored the surgical approach.

Adult↗
PubMed1982

Carbohydrate metabolism and concentration profiles of solutes in the canine lumbar intervertebral disc.

Utilization of glucose and oxygen by the cells as well as concentration profiles of solutes were studied in the canine intervertebral disc. Cell metabolism in this avascular tissue, being predominantly anaerobic, was found to be dependent on oxygen tension (this being especially pronounced in the region of 0.13-0.4 kPa (1-3 mmHg). A high production rate of lactic acid was found in the nucleus pulposus, whereas towards the periphery of the annulus fibrosus this rate gradually decreased. In the centrally located areas of the disc tissue, far away from the blood circulation, the highest concentrations of lactic acid were found. For the normal disc the energy demands seem to be met as even small amounts of oxygen account for a large energy source, whereas the cellular requirements are balanced up predominantly by glucose. In regions with extremely low oxygen tensions large amounts of glucose are consumed, but an additional potential energy pool of glycogen seems to be available.

Animals↗
PubMed1982

Loads on the lumbar spine. Validation of a biomechanical analysis by measurements of intradiscal pressures and myoelectric signals.

UNLABELLED: We studied the validity of predictions of compressive loads on the lumbar spine and contraction forces in lumbar trunk muscles based on a biomechanical model. The predictions were validated by quantitative measurements of myoelectric activities at twelve locations on the trunk and of the pressure in the third lumbar disc. Twenty-five tasks were performed isometrically by four healthy volunteers. The model predicted that the tasks imposed mean compressive loads on the spine of as much as 2400 newtons and required contraction forces of the posterior muscles of the back of as much as 1800 newtons. Intradiscal pressures of as much as 1600 kilopascals were measured. The predicted and measured quantities were well correlated. It appears that the model adequately predicted the compressive loads on the lumbar spine and the tensions in the back muscles. CLINICAL RELEVANCE: Patients with low-back disorders limit their physical activities, which indicates that loading on the spine must be a factor in those disorders. This study shows that the loads imposed on the spine by physical activities need not be measured. They can easily be calculated. This will significantly accelerate biomechanics research on low-back disorders. The calculation techniques that we validated for predicting loads on the spine can be used to calculate the loads on any skeletal structure. Those loads are largely determined not by the externally applied loads, but by the moments of those applied loads and by the moments of the weights of the body segments that the structure must support.

Abdomen↗
PubMed1982

Nutrition of the intervertebral disc: effect of fluid flow on solute transport.

Adult dogs were injected intravenously with 35S-sulphate, and moderately exercised for one to six hours to measure isotope concentrations and profiles throughout the intervertebral discs. The isotope profiles were also observed in control animals that had been under anesthesia between injections and death. In both sets of animals, the profiles were in agreement with those expected for isotope transport by diffusion. This agreement indicates that fluid "pumping" during movement has an insignificant effect on transport of nutrients into the disc. Small solutes, e.g., O2, glucose, and sulphate, are transported into the disc chiefly by diffusion. However, calculations show that because of their low diffusivities, "pumping" may increase the rate of transport of large solutes into the disc, as it does in articular cartilage.

Anesthesia↗