The role of pediculolaminar fixation in compromised pedicle bone

STUDY DESIGN

This in vitro study analyzed the effects of a supralaminar hook on pedicle screw fixation in compromised pedicle bone.

OBJECTIVES

To determine the ability of pediculolaminar fixation to restore pedicle screw pull-out strength after stripping of senile pedicle bone.

SUMMARY OF BACKGROUND DATA

Despite improvements in pedicle screw design, the bone-screw interface remains the "weakest link" in pedicle screw fixation. This interface is especially vulnerable in osteoporotic bone previously instrumented pedicles, and at the ends of long instrumentation constructs.

METHODS

Side-to-side testing between a pedicle screw and a pedicle screw supplemented with a supralaminar hook (pediculolaminar fixation) was performed in human cadaveric lumbar vertebrae. Comparisons were made for intact and compromised pedicle bone.

RESULTS

Pediculolaminar fixation restored 89% of intact pedicle screw pull-out strength whereas the pedicle screw alone restored only 19% of intact pull-out strength. The role of pediculolaminar fixation was greatest in weaker bone. Significant differences were noted in energy to failure and post-failure energy. In intact bone, the pediculolaminar construct did not increase pull-out strength or energy to failure, although it did have a greater post-failure energy.

CONCLUSIONS

Pediculolaminar fixation can augment pedicle screw fixation in pedicle bone compromised by previous stripping or significant osteoporosis or both.

Sunlight--can it prevent as well as cause cancer?

Excessive exposure to sunlight is known to damage the skin. However, the emphasis of most studies has been on the consequences of sunlight exposure to fair-skinned individuals, and the situation of people with heavy skin pigmentation residing in, or migrating to, geographic locations with limited sunlight incidence has been largely neglected. Recent epidemiological studies suggested the hypothesis that sunlight deprivation, and the associated reduction in the circulating levels of vitamin D3 (vit D3) derivatives may lead to the increased incidence of the carcinomas of the breast, colon, and prostate. Two endocrine pathways may mediate these effects. The pineal function can potentially be involved, but the formation of vit D3 derivatives is gaining credibility as a mechanism for the retardation of cancer progression. Evidence is accumulating that such compounds, e.g., 1,25-dihydroxyvitamin D3 (1,25D3) induce differentiation of several neoplastic cell types, arrest or retard their proliferation, and act as chemopreventive agents in animal carcinogenesis. We also propose that the antineoplastic effects of vit D3 derivatives are exerted at several steps in tumor progression and that immunomodulating effects of 1,25D3 may contribute to these effects of sunlight. The recent findings that common cancers, e.g., carcinoma of the prostate and the breast, behave more aggressively in black Americans than in white Americans may be explained on this basis. Although more data are needed on the effects of sunlight on the circulating levels of 1,25D3, a corollary of this hypothesis is that there should be no broad condemnation of moderate sunlight exposure, as it may be available in insufficient amounts to some Americans.

Acclimation of a non-indigenous sub-Arctic population: seasonal variation in thyroid function in interior Alaska

Total, as well as free, T4 and T3 levels were obtained over four seasons for young male infantry soldiers assigned to interior Alaska. Significant seasonal variations were found in both T3 and T4. Total T4 and T3 levels were highest in winter, while free T4 and T3 levels were highest in early spring. Correlations with melatonin levels from a concurrent study showed an association between late day (17.00) mean spot melatonin levels during the preceding summer and T3 levels in winter and spring. Differences in seasonal T4 and T3 levels between indigenous and newly arrived people in the sub-Arctic may be related not only to cold acclimation but also to light.

Hypothalamic hamartoma in oral-facial-digital syndrome type VI (Váradi syndrome)

Oral-facial-digital syndrome (OFDS) type VI (Váradi syndrome) is an autosomal recessive trait of orofacial anomalies, cerebellar dysgenesis, and polysyndactyly. Developmental anomalies of the posterior fossa, including cerebellar hypoplasia and variants of the Dandy-Walker complex, are the most common central nervous system malformations reported in patients with this syndrome. We report hypothalamic hamartoma, supernumerary maxillary incisor, and precocious puberty in a boy with OFDS type VI. We propose that hypothalamic hamartoma is an occasional manifestation of OFDS type VI.

Body image and eating behavior in adolescents

Approximately two-thirds of adolescent girls at any age are dissatisfied with their weight, the proportion increasing with actual weight. Slightly more than half of all girls are dissatisfied with the shape of their bodies, an attitude which also is positively correlated with body weight. Girls are most likely to be distressed about excess size of their thighs, hips, waist and buttocks, and inadequate size of their breasts. Those who are dissatisfied with their bodies are more likely to engage in potentially harmful weight control behaviors, such as dieting, fasting, self-induced vomiting, diuretic use, laxative use and diet pill use. Those who diet are more likely to begin in early adolescence, to be white than black, to be of higher socioeconomic status, to engage in other eating-related practices and to have a poor body image and self esteem. Boys who are underweight are most likely to be dissatisfied with their weight and many with normal weight wish to weigh more. Approximately one-third of boys are dissatisfied with their body shape, desiring larger upper arms, chest and shoulders. Dieting and purging are less likely than exercise to be chosen by boys as methods of weight control. Dieting among boys is more likely to be associated with increased body weight and some sports, such as wrestling. Body consciousness and altered body image are widespread among adolescents, and may be associated with potentially harmful eating practices in both sexes, but more so in girls.

Inhibition by 1,25 dihydroxyvitamin D3 of c-myc down-regulation and DNA fragmentation in cytosine arabinoside-induced erythroid differentiation of K562 cells

The effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on DNA fragmentation, altered expression of the heat shock protein (hsp) 70 gene, and protooncogenes c-myc and c-myb was studied during chemical induction of erythroid differentiation in K562 cells. Preincubation of K562 cells with 1,25(OH)2D3 did not alter the concentration of hemoglobin in cells which did differentiate, but led to a reduction in the accumulation of low molecular weight DNA generated by Ara-C administration. The extent of this reduction was similar to the degree of inhibition of hemoglobin formation in the culture as the whole. Preincubation with 1,25(OH)2D3 had no effect on the increase of hsp 70 gene expression induced by a 48-hr treatment with Ara-C, but prevented the Ara-C-induced down-regulation of the protooncogene c-myc. The protooncogene c-myb was down-regulated after 15 min of treatment with Ara-C, and exposure to 1,25(OH)2D3 prior to Ara-C caused a further down-regulation of its expression. The data suggest that the events associated with erythroid differentiation may be separable into at least two groups; one of these may have an influence on the kinetics of the cell cycle traverse, and the other may be related to the expression of the erythroid phenotype.

Gynaecomasty as the first manifestation of sexual precocity (case report)

We report on a young boy who developed gynaecomastia 15 months before he showed clinical manifestations of sexual precocity. He was treated with medroxyprogesterone acetate with good results. His development to adulthood is presented. The causes of gynaecomastia in the prepubertal child are reviewed.

Vitamin D analogs inhibit erythroid differentiation and induce monocytic differentiation of leukemic cells with the same relative potency

Myeloid leukemia cells of human and murine origin can be induced to differentiate into more mature forms which lose their neoplastic properties. The hormonal form of vitamin D is a powerful inducer of monocytic differentiation, but its therapeutic use is limited by hypercalcemia. It was recently reported that a novel derivative of vitamin D, 1,25-dihydroxy-16-ene-23-yne-vitamin D3, is an exceptionally potent inducer of monocytic differentiation, and prolongs survival of mice bearing leukemia cells. We now show that this compound is also a most potent inhibitor of erythrodifferentiation. This finding has important implications for the control of hematopoiesis.

Association of c-myc protein with enzymes of DNA replication in high molecular weight fractions from mammalian cells

Oncoprotein c-myc is expressed in proliferating but not quiescent mammalian cells, and its overexpression or inappropriate expression is associated with malignant transformation. However, in spite of an intense interest, the normal function of this protein has remained elusive. As a step towards the elucidation of the function of c-myc protein, we studied its distribution within several types of cells, including HL 60, K 562, COLO 320, and CHEF/18 cells. In all of the cells studied, c-myc protein was detected in high molecular weight protein fractions, in 350-600 Kd range, in gel-exclusion chromatography and sucrose gradient centrifugation. This distribution of c-myc protein coincided with the distribution of DNA polymerase alpha and several other enzymes necessary for DNA replication. The data suggest that c-myc product may be a component of the replitase complex of enzymes involved in nuclear DNA replication.

Autogeneic bone marrow and porous biphasic calcium phosphate ceramic for segmental bone defects in the canine ulna

The purpose of this study was to evaluate a porous biphasic hydroxyapatite-calcium phosphate ceramic as a modifier and extender of an autogeneic marrow graft for filling a 2.5-cm segmental bony defect. Twenty adult mongrel dogs were surgically treated to create diaphyseal defects in the left ulnae. The defects were (1) filled with autogeneic bone marrow mixed with granular hydroxyapatite-tricalcium phosphate ceramic (granular ceramic); (2) grafted with a solid block of ceramic soaked in autogeneic bone marrow (block ceramic); (3) received no graft (no implant); or (4) were grafted with autogeneic bone marrow alone (bone marrow). All animals were followed clinically and roentgenographically for 24 weeks and then killed. Repair of diaphyseal defects with the block ceramic led to three solid unions and three fibrous unions; with the granular ceramic implants and marrow, the defects of five dogs formed solid unions, and one progressed to a fibrous union. Defects in all five dogs grafted with autogeneic bone marrow united. The three dogs with no implant formed nonunions. Histology showed normal marrow and only a light immune reaction. Complete bridging of the defect in the dogs treated with the granular ceramic occurred significantly earlier than bridging in the dogs grafted with bone marrow alone. Histomorphometry, performed on the block ceramic implants indicated active resorption of ceramic. Clinically, addition of ceramic to a marrow graft improved the handling characteristics of the graft material and accelerated healing according to roentgenographic evaluation.

Inhibition by 1,25 dihydroxyvitamin D3 of chemically induced erythroid differentiation of K562 leukemia cells

The physiologically active form of vitamin D, 1,25 dihydroxyvitamin D3 [1,25(OH)2D3], was found to inhibit erythroid differentiation of human leukemic K562 cells. Differentiation was induced by 1 mumol/L arabinocytosine (Ara-C), 40 mumol/L tiazofurin, 1 mumol/L aphidicolin, or 1 mumol/L hydroxyurea, and was monitored daily by the appearance of hemoglobin in an increasing proportion of cells. Pretreatment for 48 hours with 2.4 x 10(-8) mol/L 1,25(OH)2D3, a concentration that is also optimal for induction of monocytic differentiation of HL-60 cells, reproducibly inhibited subsequent induction of erythroid differentiation by all of the above inducers, and modified the morphologic changes that Ara-C produced in these cells. The inhibition of hemoglobinization was approximately 50% irrespective of the degree of differentiation produced by the various inducers, but growth inhibition associated with exposure to the inducers was not affected by 1,25(OH)2D3. Similar inhibition of differentiation by 1,25(OH)2D3 was observed in mouse erythroleukemia cells MEL-D1B treated with 5 mmol/L hexamethylenebisacetamide. The inhibitory effect of 1,25(OH)2D3 on erythroid differentiation of K562 cells was abrogated by cyclohexamide (20 micrograms/mL), an inhibitor of protein synthesis. The mRNA for 1,25(OH)2D3 receptor (VDR) was detected in K562 cells, and was downregulated by a 96-hour exposure to 1,25(OH)2D3 or a 48-hour exposure to Ara-C. The presence of VDR mRNA suggests a physiologic role for 1,25(OH)2D3 in K562 cells that are precursors of erythroid cells. This role is perhaps to shift the pathways of differentiation from the erythroid to the monocytic lineage.

Predictors of improvement in tardive dyskinesia following discontinuation of neuroleptic medication

Forty-nine chronic psychiatric out-patients (ten were schizophrenic) with tardive dyskinesia (TD) were examined monthly for a mean of 40 weeks (range 1-59 months) after discontinuation of neuroleptic medication. Complete and persistent reversibility of TD was rare (2%), but many patients showed noticeable improvement in movements within the first year of discontinuation, which was sometimes interrupted by psychological relapse. Using three separate outcome measures and appropriate model-fitting techniques for each, we identified several predictors of improvement in TD, including an affective or schizoaffective psychiatric diagnosis, chronic (over 20 years) psychiatric illness, being employed, younger age, and increased neuroleptic dose before discontinuation. Consistent findings emerging from these analyses suggest that the type and history of psychiatric illness affect the course of TD.

Body image and eating behavior in adolescent boys

A questionnaire about attitudes toward body weight and shape, and eating and weight control practices, was administered to 895 adolescent boys. Overall, 42% were dissatisfied with their weight and 33% with their body shape. Sixty-eight percent of the dissatisfied normal weight boys thought they were underweight and 32% thought they were overweight. Subjects dissatisfied with their body shape were most likely to desire an increased chest and arm size and decreased abdomen size. Binge eating (24%) and fasting (12%) were the most prevalent eating practices and were more common in boys dissatisfied with weight or shape. There was no difference in prevalence of eating practices between boys wishing to gain and boys wishing to lose weight. Although many boys were concerned about body weight and shape, they wished to increase weight and muscularity, rather than lose weight. Binge eating was common, but was not related to the binge-purge cycle described in girls, because losing weight is not a major concern, and other weight control practices were not more common among boys who wanted to lose weight vs gain.

Morphological and physiological effects of beta-hydroxybutyrate on rat embryos grown in vitro at different stages

Diabetic women are more likely to give birth to infants with congenital malformations than are nondiabetic women. Rodent embryos have been used as a model for the study of abnormal fetal development associated with maternal diabetes, and some of the metabolic factors which are altered in diabetes, such as raised glucose and ketones, have been shown to cause abnormal development of rodent embryos in vitro. The present work explores further the teratogenicity of beta-hydroxybutyrate to rat embryos. To determine the sensitivities of rat embryos at different stages of their development, rat embryos at 9.5 days of gestation have been cultured in vitro for 24 or 48 h, with or without 4 x 10(-2) M beta-hydroxybutyrate for all or part of the culture period. The embryos have been examined by scanning electron microscopy, and a detailed morphometric analysis of one tissue, the neuroepithelium, has been undertaken. The results confirm that beta-hydroxybutyrate causes abnormal development of rat embryos. The results of experiments in which embryos were exposed to beta-hydroxybutyrate for only part of a 48 h culture show that embryos exposed to beta-hydroxybutyrate for a complete 48 h culture are more severely affected than embryos exposed to beta-hydroxybutyrate for only part of the culture and that embryos are more vulnerable to beta-hydroxybutyrate during the first half of a 48 h culture (equivalent to 9.5 to 10.5 days of gestation) than during the second half of a 48 h culture (10.5 to 11.5 days of gestation). The results of experiments in which embryos were cultured with beta-hydroxybutyrate from 9.5 days of gestation for 24 h (equivalent to 9.5 to 10.5 days of gestation) showed that some effects of beta-hydroxybutyrate are already apparent after 24 hours in culture. Many of the abnormalities produced by beta-hydroxybutyrate can be classified as embryonic retardations rather than malformations--that is, embryos show features characteristic of normal, but younger, embryos. Embryos exposed to beta-hydroxybutyrate for the complete 48 h culture period consume less glucose and produce less lactate than control embryos on a per embryo basis, but not on a per microgram protein basis, suggesting that the reduced metabolism is an effect of beta-hydroxybutyrate-induced developmental delay rather than a cause of it.(ABSTRACT TRUNCATED AT 400 WORDS)