The evolution of functional bracing of fractures.
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Braces↗
Biomedical subjects
L Latta
Publications and source records attributed to L Latta.
Patterns of genetic architecture for life-history traits and molecular markers in a subdivided species.
Understanding the utility and limitations of molecular markers for predicting the evolutionary potential of natural populations is important for both evolutionary and conservation genetics. To address this issue, the distribution of genetic variation for quantitative traits and molecular markers is estimated within and among 14 permanent lake populations of Daphnia pulicaria representing two regional groups from Oregon. Estimates of population subdivision for molecular and quantitative traits are concordant, with QST generally exceeding GST. There is no evidence that microsatellites loci are less informative about subdivision for quantitative traits than are allozyme loci. Character-specific comparison of QST and GST support divergent selection pressures among populations for the majority of life-history traits in both coast and mountain regions. The level of within-population variation for molecular markers is uninformative as to the genetic variation maintained for quantitative traits. In D. pulicaria, regional differences in the frequency of sex may contribute to variation in the maintenance of expressed within-population quantitative-genetic variation without substantially impacting diversity at the genic level. These data are compared to an identical dataset for 17 populations of the temporary-pond species, D. pulex.
Animals↗
Understanding what makes people tick. Interview by Anne Manchester.
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Forensic Psychiatry↗
Alveolar bone turnover and tooth movement in male rats after removal of orthodontic appliances.
The purpose of this study was to acquire tooth movement, histomorphometric and biochemical data on oral tissues that had previously been loaded with calibrated orthodontic forces. One hundred and forty-four male Sprague-Dawley rats were randomly divided into two groups: Group I, orthodontic appliances placed for 16 days to mesially move maxillary first molars with an initial force of 40 gm, and group II, sham orthodontic treatment. Seven to twelve rats were killed at each of six times after removal of appliance. Tooth movement was measured cephalometrically, alveolar bone turnover by histomorphometry, and tissue phosphatase levels biochemically. Treated molars moved distally more rapidly than the shams (13.9 vs 5.0 microns/day). The appliance removal group had a persistent 10-fold elevation in root resorption on the mesial (p < 0.0001), as well as early elevations in osteoclasts on the mesial and osteoblasts on the distal (p < 0.001) that returned to control by 3 to 5 days. Acid, alkaline phosphatase, and tartrate-resistant acid phosphatase (TRAP) remained elevated in the tissues until 10 days (p < 0.0001). Changes in the dynamic measures of bone formation were characterized by low rates at days 1 and 3 (p < 0.01), elevating thereafter on the mesial and the converse on the distal. Orthodontic tooth movement relapses, and bone remodeling continues for several days after removal of appliance consistent with the direction of loading, orthodontic treatment stimulates root resorption at sites that were loaded in pressure without detectable recovery, and root resorption does not increase at the tension sites.
Acid Phosphatase↗
Alveolar bone turnover in male rats: site- and age-specific changes.
BACKGROUND: This study compares alveolar bone turnover adjacent to distally drifting maxillary first molar teeth of rapidly and slowly growing rats. METHODS: Two groups of forty male rats (1 and 3 months) were sacrificed. Sera were analyzed for acid (AcP), alkaline (AlkP), and tartrate-resistant acid phosphatase (TRAP). Bone histomophometry was done on parasagittal sections of maxillary molars. Molar drift was quantified cephalometrically. RESULTS: Distal surface contained more osteoclasts and higher osteoclast percents than mesials at both ages (P < 0.001). There were also more osteoclasts on the distals of the older rats as compared to the young (P < 0.001). Osteoblast percents were higher (P < 0.001) in the older rats on both surfaces. Mesials had higher double-labeled surface, MAR and BFR than distals in the younger rats (P < 0.001). The younger rats had higher (P < 0.001) AlkP, AcP, and TRAP. There were no age-specific differences in rate of molar drift. A model of rate of molar drift (P < 0.0015) containing bone formation measures accounts for 54.9% of the variability. CONCLUSIONS: We conclude that the bone turnover dynamics adjacent to maxillary first molars represent predominantly remodeling on the distal in both groups and modeling on the mesial only in the young rats, that distal molar tooth drift reflects alveolar bone turnover, and that alveolar bone manifests the marked reduction in bone cell activity that occurs in the rat skeleton after 8 weeks but that this reduction is compensated by recruitment or maintenance of more bone cells at these sites.
Aging↗
Mechanical failures of intramedullary tibial nails applied without reaming.
The clinical mechanical failures of small diameter intramedullary interlocking nails were evaluated to determine the relationship of failure modes to the type or location of tibial fractures. Methods were developed to duplicate failure modes in vitro in standardized tests to simulate the clinical situations. Where standard test methods were inadequate, new methods were developed to provide quantifiable, reliable methods of evaluating potential clinical performance. The modes and rates of mechanical failure in the clinical series were consistent among participating centers: (1) In diaphyseal fractures with secondary trauma, the intramedullary nail bent at the fracture site where the working length was unsupported; (2) failures that occurred several weeks after nailing were the result of fatigue fractures of the locking screws, usually at the distal end; and (3) nail and screw failures occurred most commonly in proximal and distal tibial fractures. The strength of the 8- and 9-mm sizes of Synthes and Russell-Taylor nails were comparable.
Bone Nails↗
An absence of structural changes in the proximal femur with osteoporosis.
The hypothesis that osteoporosis occurs not as a preferential loss of the tensile trabeculae but as a general loss of bone was tested by using bone mineral densitometry and an indentation test on dissected proximal femora. As osteoporosis advanced a significantly correlated decrease was found in both bone mineral density and mechanical properties between the principal compressive and tensile trabeculae. The decrease correlated with a decrease in the Singh index. These findings led to the conclusion that a sequential bone loss from the tensile trabeculae to the compressive ones did not occur as Singh reported, but instead a generalized loss of bone mineral in both the tensile and compressive trabeculae supervened. The structural changes, on which the grading system by Singh was based, were not observed in the proximal femur affected by osteoporosis.
Aged↗
Comparison of patellar resurfacing versus nonresurfacing in bilateral total knee arthroplasty.
Twenty-five patients who received bilateral total knee prostheses were studied to evaluate the advantages and disadvantages of patellar resurfacing. Only patients with advanced patellofemoral disease were included in the study. In all patients, patellar resurfacing had been done in the right knee but not in the left knee. The DePuy porous-coated implant was used in all cases. Subjective criteria were compared with objective criteria, which included range of motion, knee flexion and extension, and roentgenographic evaluation. The findings in this study suggest that patellar resurfacing can offer the patient a superior knee with regard to pain relief and strength.
Aged↗
Femoral neck fractures. A biomechanical study of a new form of internal fixation using multiple telescoping variable length compression screws.
Biomechanical tests of a new method of fixation for intracapsular hip fractures compared with other types of mechanical fixation were investigated under one specific loading condition. Human femora fixed in formalin were classified by the Singh index for degree of osteoporosis. Specimens of Grade III or less were grouped as osteoporotic, and Grade IV or greater, normal. Both normal and osteoporotic bones were tested. A transverse osteotomy in the subcapital region was fixed by one of two techniques: (1) Asnis screws (AS) or (2) variable length telescoping compression screws (VLCS). Each specimen was roentgenographed after fixation to assess the placement of the devices and reduction. Each femur was held in an angle vise that was placed on rollers on a table mounted on the servohydraulic testing machine. Compression was applied at a constant displacement rate of 10 mm per second to failure. Load and displacement were monitored; specimens were photographed and roentgenographed after failure. In osteoporotic bone, the VLCS provided yield and ultimate load values several times greater than those of the AS. Resistance to combined compression varus loading was significantly higher with the experimental system in osteoporotic bone. In normal bone there was no significant difference between the two systems.
Biomechanical Phenomena↗
Computed tomography evaluation of stability in posterior fracture dislocation of the hip.
Measurements of the percentage of remaining posterior acetabulum on computed tomography (CT) scan (the Acetabular Fracture Index) in posterior fracture dislocations of the hip were evaluated to determine the stability of the joint. All hips with less than 34% of the remaining posterior acetabulum were unstable. Hips with greater than 55% were stable. Between these values, hips were either stable or unstable. A statistical analysis demonstrated highly significant differences in the average remaining posterior acetabulum between the stable and unstable group. These findings were based on a review of 26 patients with posterior fracture dislocations of the hip (Epstein Type I-IV injuries) combined with CT scan analysis. The clinical status of hip stability was correlated with the Acetabular Fracture Index, and this provided the basis for the study. A simple linear measurement of the remaining posterior acetabulum on CT (the Approximate Acetabular Fracture Index) can be done easily by a physician, and this closely approximates the true remaining acetabular arc. Seven of ten unstable hips in 31 Epstein Type I-V patients showed femoral head subluxation of 0.5 mm or more on CT scan, whereas none of the 21 stable hips had demonstrable subluxation. Risk analysis provided a means of predicting hip stability for individual patients.
Acetabulum↗
Biomechanical and biochemical properties of dog cartilage in experimentally induced osteoarthritis.
The finding of other investigators that increased water content is often associated with signs of a torn collagen network in human osteoarthritic (OA) cartilage led to this study. In the Pond-Nuki model of post-traumatic OA experimental but not control femoral condylar cartilage showed evidence of breakdown and stiffening of collagen network as assessed by measurement of swelling properties and indentation behaviour respectively. These changes in the unstable knees occurred despite lack of erosion of that surface cartilage ascertained from carbon black mapping and history. The stiffening rather than softening change was therefore attributed to cartilage oedema of the middle and deep certilagenous zones, wherein breakdown of collagen network has been postulated to occur. Because of insignificant reduction of total hexuronate in these cartilages, a proteoglycan (PG) profile of sedimentation coefficients for aggregate (PGA) and subunit species (PGS) was analysed to see if collagen network changes in the dog preceded PG alteration. Despite minimal histological changes our results confirmed previous findings in the tibial plateau cartilage in this model, that PGA was reduced in size and PGS increased in amount. Slight enzymatic breakdown of PGs, or altered synthesis due to cellular responses to either the injury directly or to synovial inflammation, seems necessary to explain such changes in the absence of cartilage erosion.
Animals↗
Miami TLSO in the management of scoliosis: preliminary results in 100 cases.
A custom fabricated polypropylene thoraco-lumbo-sacral orthosis (TLSO) for the treatment of scoliotic curves with an apical vertebrae of T7 or below is described, and the results in 100 patients treated over a 5 year period are reported. The average follow-up for all cases was 13 months, the longest being 59 months. Average initial correction in brace for thoracic curves was 36%, for thoraco-lumbar curves 56%, and for lumbar curves 63%. Double major curves averaged 38% initial correction for the upper curves and 37% for the lower curves. Twenty cases had completed brace treatment with an average follow-up of 8 months out of brace. Of the 30 curves in the 20 patients, 11 were improved more than 5 degrees, 19 remained unchanged (+5 degrees), and none had progressed more than 5 degrees. Twenty-three percent of the patients required a second orthosis and complications occurred in only two patients. The primary advantages of this TLSO include improved cosmesis, minimal discomfort, excellent provision for heat exchange, minimal confinement of the thoracic cage, and maximum retention of spinal mobility.
Adolescent↗
The role of soft tissue in the stabilization of tibial fractures.
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Biomechanical Phenomena↗