Search PubMed⌕ Search

Biomedical subjects

J L Marsh

Publications and source records attributed to J L Marsh.

At least 55 records · Page 3Linked to original sources
PubMed2000

High density polyetherurethane foam as a fragmentation and radiographic surrogate for cortical bone.

BACKGROUND: Although one of the most important factors in predicting outcome of articular fracture, the comminution of the fracture is only subjectively assessed. To facilitate development of objective, quantitative measures of comminution phenomena, there is need for a bone fragmentation surrogate. METHODS: Laboratory investigation was undertaken to develop and characterize a novel synthetic material capable of emulating the fragmentation and radiographic behavior of human cortical bone. RESULT: Screening tests performed with a drop tower apparatus identified high-density polyetherurethane foam as having suitable fragmentation properties. The material's impact behavior and its quasi-static mechanical properties are here described. Dispersal of barium sulfate (BaSO4) in the resin achieved radio-density closely resembling that of bone, without detectably altering mechanical behavior. The surrogate material's ultimate strength, elastic modulus, and quasi-static toughness are within an order of magnitude of those of mammalian cortical bone. The spectrum of comminution patterns produced by this material when impacted with varying amounts of energy is very comparable to the spectrum of bone fragment comminution seen clinically. CONCLUSIONS: A novel high-density polyetherurethane foam, when subjected to impact loading, sustains comminuted fracture in a manner strikingly similar to cortical bone. Moreover, since the material also can be doped with radio-opacifier so as to closely emulate bone's radiographic signature, it opens many new possibilities for CT-based systematic study of comminution phenomena.

Barium Sulfate↗
PubMed1999

Three-dimensional morphological analysis of isolated metopic synostosis.

Morphological differences were quantified in three-dimensions among individuals with untreated isolated metopic synostosis and between those individuals and similar aged-matched normal dry skulls to test two hypotheses: first, that the dysmorphology is a self-correcting condition; and second, that a lack of vertical growth of the skull produces this dysmorphology. Three-dimensional (3D) coordinates were recorded for 22 craniofacial landmarks from CT scans of 15 metopic patients, ranging from 5- to 32-months-old, and of four normal dry skulls, ranging in age from 6- to 36-months-old. The patient population was diagnosed with isolated metopic synostosis at The Johns Hopkins Medical Institutions in Baltimore, Maryland or Children's Hospital in St. Louis, Missouri. Comparisons between the metopic age groups indicate that the trigonocephalic phenotype worsens through time. Between 5 and 14 months, the neurocranium displays an increase in vertical growth. This was followed by a lack of vertical growth between 14 and 32 months. The face displays a lack of vertical growth from 5 to 14 months and an increase in vertical growth after 14 months. Comparisons between the metopic age groups and the normal skulls indicate that the trigonocephalic head is taller superoinferiorly and longer anteroposteriorly. Relative to the normal phenotype, the inferior temporal region in the metopic phenotype is narrow. These findings enabled the rejection of both hypotheses and localized form differences between normal and metopic phenotypes. Based on these results, we suggest that the trigonocephalic phenotype worsens with age and the amount of vertical growth that produces the trigonocephalic phenotype varies throughout growth with respect to location within the skull and age.

Age Factors↗
PubMed1999

Regeneration in insects.

@9cIntroduction@21T issues exhibit an impressive ability to respond to a myriad of insults by repairing and regenerating complex structures. The elegant and orderly process of regeneration provides clues to the mechanisms of pattern formation but also offers the hope that the process might one day be manipulated to replace damaged body parts. To manipulate the process, it will be necessary to understand the genetic basis of the process. In the case of the insect leg, we are coming close to such a level of understanding and many of the lessons learned are relevant to vertebrate systems. A dynamic web of gene regulatory networks appears to create a robust self-organizing system that is at once extremely intricate but also perhaps simple in its reliance on a few key signaling pathways and a few simple processes, e.g. autoactivation and lateral inhibition. Here we will summarize what has been learned about the networks of gene regulation present in the Drosophila leg discs and then we will explore how the regenerative responses to different insults can be understood as predictable responses to these networks. Each of the regulatory networks could themselves serve as the subject of a detailed review and that is beyond the scope of this discussion. Here we will focus on the interplay between the regulatory networks in patterning the tissue.

Animals↗
PubMed1999

Articulated external fixation of the ankle: minimizing motion resistance by accurate axis alignment.

This study describes how an optimal single hinge axis position can be established for the application of articulated external fixation to the ankle joint. By deliberately introducing various amounts of relative mal-alignment between the optimal talocrural joint axis and the actual fixator hinge axis, it was possible to measure the corresponding amounts of additional resistance to joint motion. In a cadaveric study of six ankle specimens, we determined the instant axis of rotation of the talocrural joint from 3-D kinematic data. acquired by an electromagnetic motion tracking system. For each specimen, an optimal fixator hinge position was calculated from these motion data. Compared to the intact natural joint, aligning the fixator along the optimized axis position caused a moderate increase in energy (0.14 J) needed to rotate the ankle through a prescribed plantar/dorsiflexion range. However, malpositioning the hinge by 10 mm caused more than five times that amount of increase in motion resistance. While articulated external fixation with limited internal fixation can establish a favorable environment for the repair of severe injuries such as tibial pilon fractures, the large additional resistance to motion accompanying a malpositioned fixator axis suggests the development of untoward intra-articular forces that could act to disturb fragment alignment.

Ankle↗
PubMed1999

Long-term stability of postpalatoplasty perceptual speech ratings: a prospective study.

This prospective study was undertaken to assess the long-term stability of velopharyngeal perceptual speech ratings of patients with repaired cleft palate. All patients were evaluated and managed at the Cleft Palate and Craniofacial Deformities Institute, St. Louis Children's Hospital. Patients alternately received palatoplasty with or without intravelar veloplasty. Two senior surgeons standardized their operative procedures and performed or supervised directly all operations. Perceptual speech and language evaluations were conducted by the same experienced speech pathologist when the children were 6 years old and 12 years or older. Data were analyzed from the 28 patients available for long-term follow-up. The intravelar veloplasty (N = 14) and nonintravelar veloplasty (N = 14) groups were similar with respect to cleft anatomy and mean age at palatoplasty and at the second perceptual speech evaluation. Evaluation of the 12-year-old and older ratings indicated that the overwhelming majority of patients improved or maintained clinical stability in perceptual ratings of velopharyngeal function. When assessing direction and magnitude of change (i.e., incremental improvement vs. deterioration), the intravelar veloplasty and nonintravelar veloplasty groups had a similar distribution of perceptual speech ratings at both the 6-year and 12-year or older speech evaluations. Results were consistent with previously published data from our center, that the intravelar veloplasty procedure did not affect demonstrably the incidence of postpalatoplasty auditory perceptual symptoms of velopharyngeal dysfunction.

Age Factors↗
PubMed1999

Sagittal craniosynostosis outcome assessment for two methods and timings of intervention.

A retrospective quantitative analysis of 40 infants who underwent surgery for sagittal craniosynostosis was conducted to determine whether any difference in outcome, with respect to cranial index (cranial width/cranial length x 100), could be associated with either the age at surgery or the extent of the operation. Children < or = 13 months old at surgery and for whom there were archived computed tomography digital data preoperatively, perioperatively, and 1 year postoperatively were studied. For statistical analysis, the operation was classified as either extended strip craniectomy or subtotal calvarectomy, and the age at operation was either < or = 4 months or > 4 months. Twenty-eight patients underwent extended strip craniectomy at a mean age of 5.1 months. Their mean cranial index preoperatively was 67 versus 71 at 1 year postoperatively (p < 0.0001). Of extended strip craniectomy patients, 15 were operated on at age < or = 4 months (mean = 2.9 months) and 13 at age > 4 months (mean = 7.6 months). Mean cranial indices for age at operation groups did not achieve age-appropriate normal range values 1 year postoperatively for either group, and there was no significant difference between the mean percentages of improvement achieved (p = 0.143). Twelve patients underwent subtotal calvarectomy at a mean age of 5.2 months. Their mean cranial index preoperatively was 66 versus 74 at 1 year postoperatively (p < 0.0001). The mean cranial index in this group reached age-appropriate normal range values 1 year postoperatively. The percentage improvement in cranial index 1 year after subtotal calvarectomy was greater than after extended strip craniectomy (p = 0.003). Extended strip craniectomy for sagittal craniosynostosis does not achieve normal cranial width:length proportions, even when performed before 4 months of age. Subtotal calvarectomy for sagittal craniosynostosis does achieve normal cranial width:length proportions in the majority of the children, at least when performed within the first 13 months of life.

Craniosynostoses↗
PubMed1999

Photographic assessment of head shape following sagittal synostosis surgery.

A photographic assessment of the head shape of infants who had undergone surgical correction of sagittal synostosis was performed to determine (a) whether this subset could be delineated from an age-matched normal subpopulation and (b) whether two operative procedures differed in achieving normalization of head shape. This retrospective study included 8 patients who underwent extended strip craniectomy, 12 patients who underwent subtotal calvarectomy and cranial vault remodeling, and 12 age-matched subjects with no calvarial abnormality, for a total of 32 subjects. Criteria for inclusion in this study included surgery for sagittal synostosis within the first year of life and postoperative photographs at ages 4 to 8 years (mean, 4.5 years). Each set of images (frontal and lateral profile) were ranked from most to least normal by five lay observers and four professional observers. The rankings were analyzed with statistics designed for ordinal data. Differences in ranking between treatment groups were examined with Kruskal-Wallis rank sums tests. Mean ranks were calculated for lay and professional observers in an attempt to produce simpler and more generalizable results; these means were also analyzed using statistics designed for ordinal data. There was no statistical difference in the ranks of infants who had undergone a surgical correction and the normal subpopulation. In the mean rankings of the lay observers, the normal groups had the highest score mean (15.6), the group with extended strip craniectomy was second (16.0), and the subtotal calvarectomy with calvarial remodeling group was last (17.8) (p = 0.84). In the mean rankings of the professional observers, the normal groups again had the highest score mean (15.8), the subtotal calvarectomy group was second (15.9), and the extended craniectomy group was last (18.6) (p = 0.77). These results suggest that children who have undergone correction of sagittal synostosis in infancy are indistinguishable from their peers, on the basis of fully haired head shape on frontal and lateral photographs, when they begin primary school, irrespective of the type of calvarial surgery.

Craniosynostoses↗
PubMed1999

Rank order analysis of tibial plafond fractures: does injury or reduction predict outcome?

We investigated the effects of severity of initial injury pattern and the quality of the articular reduction on outcome of displaced intra-articular distal tibial fractures, using a series of 25 patients who were treated with articulated external fixation and limited internal fixation, which provided a spectrum of reduction quality. Outcome was assessed by clinical ankle scores and radiographic arthrosis. The results demonstrate the rank order method to be a reliable means of stratifying severity of injury and quality of reduction. Neither injury nor reduction correlated with clinical ankle score. Reduction had a significant correlation with radiographic arthrosis. We conclude that the rank order method is useful in stratification of fracture patients, and that factors other than injury pattern and quality of articular reduction are important in determining outcome of patients with this severe articular injury.

Adolescent↗
PubMed1999

Brain growth rates in craniosynostotic rabbits.

OBJECTIVE: It has been suggested that abnormal brain morphology or growth rates may be a primary causal factor of craniosynostosis due, in part, to a lack of normal growth stretch and tension at the sutural margins. The purpose of the present study was to quantify cerebral hemisphere morphology and growth in a rabbit model of nonsyndromic coronal suture synostosis to determine whether cerebral dysmorphology is primary or secondary to synostosis in this model. DESIGN: Fifty-seven brains (114 hemispheres) were examined from 40 normal control rabbits and 17 rabbits with bilateral coronal suture synostosis ranging in age from 25 to 450 days postconception (synostosis occurs at approximately 23 days postconception in this model). The calvariae were removed, the brains were fixed in 10% paraformaldehyde, and in situ bilateral measurements of cerebral hemisphere length and cerebral hemisphere width were obtained using a Wild microscope with a camera lucida attachment and digital caliper. Regression analysis was used to compare cerebral cortex growth rates by age between the two groups. RESULTS: Cerebral hemisphere width and cerebral index regression line slopes had similar y intercepts (23 day postconception) with significantly (p < .05) diverging slopes over time. Normal rabbits increased more rapidly than synostosed rabbits. No significant (p > .05) differences were noted in regression line slopes between groups for cerebral hemisphere length by age or length by width. CONCLUSIONS: Cerebral dysmorphologies are probably a compensatory, secondary (postsynostotic) event and not a primary causal factor of craniosynostosis in this rabbit model of human familial, nonsyndromic coronal suture synostosis.

Aging↗
PubMed1999

Quantitative assessment of osseous, ocular, and periocular changes after hypertelorism surgery.

The purpose of this study was to develop a methodology to quantify osseous, ocular, and periocular fat changes caused by correction of orbital hypertelorism to test the hypothesis that there is a quantitatively predictable relationship between the movement of the osseous orbit and that of the ocular globe. A retrospective review was performed of 10 patients who were status post unilateral or bilateral transcranial medial orbital translocation, for whom there were archival digital data for preoperative and postoperative (mean interval = 30 months) three-dimensional computed tomographic (CT) scans. In addition to standard demographic and surgical data, the clinical preoperative and postoperative interpupillary and intermedial canthal distances were recorded. By using a computer graphics workstation, the CT digital data were registered to four surgically unaltered anatomic fiducial points to allow longitudinal quantitative comparisons. The following three-dimensional measurements were made for each patient preoperatively and postoperatively: interdacryon and interocular centroid distances, and on a standard series of three horizontal and two vertical planes, the position of the medial and lateral orbital walls, and the thickness of the medial and lateral periorbital fat (20 orbits). CT digital distances were compared with similar clinical distances when possible. The age at operation ranged from 4.0 to 12.5 years (mean, 6.6 years). The reduction in interdacryon distance exceeded the reduction in intercentroid distance (mean interdacryon change = -5.3 mm versus mean intercentroid change = -2.7 mm). Although there was a strong correlation between the amount of reduction of the lateral orbital wall and intercentroid distances, there was only a moderate correlation between the reduction in the intercentroid distance and that of the medial orbital wall. Similarly, there was a moderate correlation between the decrease in thickness of the lateral periorbital fat and the reduction of intercentroid distance but not of the medial orbital fat. In conclusion, medial translocation of the orbit does not produce equivalent movement of the ocular globe; neither the intermedial canthal nor the interdacryon distance is a useful predictor of ocular centroid position; and if the goal of hypertelorism operation is reduction of interocular distance, then CT measurement of globe intercentroid distance is essential for outcome assessment.

Adipose Tissue↗
PubMed1999

External fixation of open humerus fractures.

Fifteen patients with open shaft of humerus fractures were treated with a monolateral external fixator. Nine patients presented with nerve palsies. Two radial nerves were disrupted and required grafting. Of the seven others, six spontaneously recovered and one brachial plexus partially improved. All fractures healed. The average duration of external fixation was 21 weeks. Four patients required additional procedures prior to healing (external fixator reapplication-2, plating and bone grafting-2). Two of these four experienced breakage of 4.5 mm external fixation pins. Eight patients developed pin tract infections, which all resolved with local care and antibiotics. Thirteen patients were contacted at an average of 63 months after injury. Eleven reported they were satisfied with their result, nine had no functional limits, and eight reported no pain.

Adolescent↗
PubMed1998

The gastrulation defective gene of Drosophila melanogaster is a member of the serine protease superfamily.

The establishment of dorsal-ventral polarity in the oocyte involves two sets of genes. One set belongs to the gurken-torpedo signaling pathway and affects the development of the egg chorion as well as the polarity of the embryo. The second set of genes affects only the dorsal-ventral polarity of the embryo but not the eggshell. gastrulation defective is one of the earliest acting of this second set of maternally required genes. We have cloned and characterized the gastrulation defective gene and determined that it encodes a protein structurally related to the serine protease superfamily, which also includes the Snake, Easter, and Nudel proteins. These data provide additional support for the involvement of a protease cascade in generating an asymmetric signal (i.e., asymmetric Spätzle activity) during establishment of dorsal-ventral polarity in the Drosophila embryo.

Amino Acid Sequence↗
PubMed1998

Changes in the pattern of twisted gastrulation gene expression among Drosophila species.

A long-standing hypothesis posits that morphological changes may be more likely to result from changes in regulation of gene expression than from changes in the protein coding sequences of genes. We have compared the expression pattern of the twisted gastrulation (tsg) gene among five Drosophila species: D. melanogaster, D. simulans, D. subobscura, D. mojavensis, and D. virilis. The tsg gene encodes a secreted protein that is required for the specification of dorsal midline fates in the Drosophila early embryo. TSG is unlike other secreted growth and differentiation factors in Drosophila in that its expression pattern can be experimentally varied and still result in normal development. Because of this, its regulatory region may be freer to diverge than that of other developmental genes whose misexpression may lead to lethal defects. Thus, the tsg gene may be a good indicator of the frequency and nature of evolutionary changes affecting patterns of gene expression. Over approximately 60 million years (Myr), the tsg gene has retained a dorsal-on/ventral-off pattern and a middorsal region of expression; but there have been marked changes in the middorsal domain of expression as well as the appearance/loss of other domains of expression along the anterior/posterior axis. Changes between closely related species (approximately 2-5 Myr since divergence) that are not reflected among more distantly related species suggest frequent changes in gene expression over evolutionary time. These changes in gene expression may serve as the raw material for eventual evolutionary changes in morphology.

Animals↗
PubMed1998

External fixation of tibial plafond fractures: is routine plating of the fibula necessary?

OBJECTIVES: To determine the advantages and disadvantages of plating an associated fibula fracture in tibial plafond fractures treated with external fixation that spans the ankle. STUDY DESIGN: Retrospective clinical review. METHODS: The incidence of treatment complications and the outcomes achieved were compared between two groups of patients with tibial plafond fractures and associated fractures of the fibula. Both groups were treated by a uniform technique of monolateral external fixation. One group, consisting of twenty-two patients with twenty-two fractures, had plate fixation of the distal fibula and the other group, thirty-one patients with thirty-two fractures, had no fibular fixation. RESULTS: The demographics of the two groups, including sex, fracture classification, and number of open fractures, were similar. The outcome of the two groups for radiographic arthrosis and clinical ankle score, measured at minimum two-year follow-up, showed no statistically significant difference. The total numbers of complications were not statistically different between the two groups (p = 0.15), but the types of complications varied. Group I had eight complications: five fibular wound infections, two fibular nonunions, and one angular nonunion. Group II had seven complications: six angular malunions and one tibial wound infection. CONCLUSION: Open reduction and internal fixation of the fibula fracture in tibial plafond fractures treated with external fixation that spans the ankle is associated with a significant rate of complications, and good clinical results may be obtained without fixing the fibula.

Adolescent↗
PubMed1998

Quantification of dynamic velopharyngeal port excursion following sphincter pharyngoplasty.

The sphincter pharyngoplasty is a surgical procedure designed to correct velopharyngeal dysfunction. Its advocates cite the theoretical advantage of its induction of dynamic activity of the neovelopharyngeal port, but this dynamic activity has yet to be quantitatively demonstrated in the literature. The purpose of this study was to quantify postoperative velopharyngeal dynamism and to document the results of intervention outcome on sphincteric excursion measurements from minimal-to-maximal orifice closure. We conducted a 7-year retrospective review of speech videofluoroscopy evaluations in patients who had undergone sphincter pharyngoplasty in our center. Between 1989 and 1994, there were 58 patients so treated for postpalatoplasty velopharyngeal dysfunction by two surgeons using the same operative technique. Patients for whom sphincter pharyngoplasty was recommended fulfilled both of the following criteria: (1) velopharyngeal dysfunction caused by an anatomic, myoneural, or combined deficiency of the velopharyngeal sphincter that would not be expected to be managed by speech therapy alone, and (2) preoperative videonasendoscopy and speech videofluoroscopic studies that demonstrated large-gap coronal, circular, or bow-tie closure patterns or velopharyngeal hypodynamism. Of the original 58 patients, 24 underwent postoperative speech videofluoroscopic evaluations with basal views. Of these, 20 of the evaluations (83 percent) were of adequate quality to be included in a research study. Still images showing maximum and minimum excursion of the sphincter in basal view were obtained. To test for observer reliability, the speech videofluoroscopic studies were randomized and presented for measurement to the same individual on two occasions, each session separated by a 1-month time interval. Topographic imaging software was used to obtain maximum and minimum measurements to within 0.1 mm. Partitioning the variance of the data showed that measurement variability was a very small portion of the total, and that difference between the minimum and maximum values was the largest source of variability. Of the total variability in the data, 64.0 percent originated in the minimum/maximum difference, 34.3 percent came from patient variability, and only 1.7 percent resulted from original or repeat measurements. The patient variability may be exaggerated because of variability in the scale of measurement. Results of this study indicate a quantifiable and statistically significant difference in maximum-to-minimum excursion of sphincteric closure. Sphincter pharyngoplasty appears to be dynamic in the majority of cases.

Adolescent↗
PubMed1998

Does preexisting posterior pharyngeal wall motion drive the dynamism of sphincter pharyngoplasty?

Lateral speech videofluoroscopic evaluations were videotaped preoperatively and postoperatively for 20 patients who underwent sphincter pharyngoplasty. Randomized videotapes were constructed and subsequently evaluated by speech/language pathologists experienced in assessing patients with velopharyngeal dysfunction. Rating forms assessing various motion parameters of the posterior pharyngeal wall were completed and analyzed statistically. Results showed that the posterior pharyngeal wall configuration postoperatively was less likely to be rated as smooth relative to the preoperative configuration (p = 0.019). No other statistically significant data were obtained, although there was a trend for posterior pharyngeal wall movement rated as discrete preoperatively to be described as generalized postoperatively. We conclude that when comparing preoperative and postoperative parameters, sphincter pharyngoplasty does not significantly affect posterior pharyngeal wall motion. Posterior pharyngeal wall configuration is less likely to be categorized as smooth after sphincter pharyngoplasty relative to the preoperative condition. Although sphincter pharyngoplasty has been shown to improve velopharyngeal function, there is little evidence from this study to suggest that preexisting posterior pharyngeal wall motion causes sphincteric movement.

Child↗