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PubMed1996

Selecting a surgical method for thoracic myelopathy caused by ossification of the posterior longitudinal ligament.

STUDY DESIGN: The authors classified typical distributional patterns of ossification of the posterior longitudinal ligament of the thoracic spine in 1) central part of S-curve, 2) just above apical vertebra, and 3) combined with ossification of ligamentum flavum below apical vertebra. The results of the surgical methods selected according to the authors' classification were compared with those of previous reports. OBJECTIVES: To establish the criteria for selecting an appropriate surgical method for ossification of the posterior longitudinal ligament of the thoracic spine. SUMMARY OF BACKGROUND DATA: Poor surgical results for ossification of the posterior longitudinal ligament of "middle or lower thoracic spine" have been reported, but the unsuccessful location and curve has not been strictly defined. METHODS: The authors studied postsurgical results in 26 cases of thoracic myelopathy caused by ossification of the posterior longitudinal ligament. They also investigated radiographs of 111 cases, including 85 patients under observation, and examined the relationships between thoracic spine alignment and ossification of the posterior longitudinal ligament distribution. RESULTS: Twenty-three patients treated with methods conforming to the authors' criteria achieved satisfactory recovery in walking ability except for one patient. The results of the other three patients who underwent surgery with nonconforming methods were uneven. CONCLUSION: Posterior decompression, as well as anterior decompression, is effective in the first pattern in the cervicothoracic region. In case of the second pattern, the responsible ossification of the posterior longitudinal ligament always lies one or two levels above the apical vertebra and should be removed by anterior approach, regardless of the extent of kyphosis. Transthoracic anterior decompression surgery is considered the best method for most patients under the second and third patterns.

Adult↗
PubMed2002

Association of bone metabolism regulatory factor gene polymorphisms with susceptibility to ossification of the posterior longitudinal ligament of the spine and its severity.

STUDY DESIGN: A case-control association study and a stratified study investigating the genetic etiology for ossification of the posterior longitudinal ligament of the spine. OBJECTIVE: To determine the association of restriction fragment length polymorphisms of estrogen receptor, vitamin D receptor, parathyroid hormone, and interleukin-1alpha and -1beta with susceptibility to ossification of the posterior longitudinal ligament of the spine and its severity. SUMMARY OF BACKGROUND DATA: Contribution of genetic backgrounds to the etiology for ossification of the posterior longitudinal ligament of the spine has been suggested by epidemiologic studies. METHODS: Genomic deoxyribonucleic acid samples obtained from 120 patients (77 men and 43 women) with ossification of the posterior longitudinal ligament of the spine and 306 control subjects without the disorder (166 men and 140 women) were amplified by polymerase chain reaction, and polymorphism genotypes were determined by restriction endonuclease digestion. The distribution of genotypes was compared between patients with the disorder and control subjects. In addition, the severity of ossification was determined by the number of ossified vertebrae in patients with the disorder, and associations of the severity with age, gender, and genotypes were examined. RESULTS: Estrogen receptor (P = 0.007) and interleukin-1beta (P = 0.001) polymorphisms exhibited different distributions between patients with ossification of the posterior longitudinal ligament of the spine and control subjects in women, but not in men. In patients with the disorder, the severity of ossification was negatively correlated with age in women (P = 0.013), but not in men. Estrogen receptor polymorphism was associated with the severity only in women (P = 0.001). CONCLUSIONS: The contribution of genetic backgrounds is likely to be stronger in women than in men with ossification of the posterior longitudinal ligament of the spine. Estrogen receptor polymorphism was associated with both initiation and promotion of the disorder, but interleukin-1beta polymorphism was associated only with its initiation in women.

Adult↗
PubMed2002

Relative safety of anterior microsurgical decompression versus laminoplasty for cervical myelopathy with a massive ossified posterior longitudinal ligament.

STUDY DESIGN: A retrospective clinical study was conducted. OBJECTIVE: To investigate the relative safety of anterior microsurgical decompression with iliac strut graft fusion versus laminoplasty for a massive ossified posterior longitudinal ligament in the cervical spine. SUMMARY OF BACKGROUND DATA: The question of how the treatment for cervical myelopathy associated with a massive ossified posterior longitudinal ligament can be improved remains unclear. METHODS: Addressing this question involved analyzing the data for 26 patients who had undergone either an anterior (n = 14) or posterior procedure (n = 12) for a large ossified posterior longitudinal ligament with the thickness exceeding 50% of the bony canal diameter (average, 65%; range, 52-81%). RESULTS: The two groups showed no statistical difference in preoperative factors including age, duration of symptoms, functional score, maximal occupancy ratio of the ossified posterior longitudinal ligament to the canal, and magnetic resonance findings such as the longitudinal extent of distinct cord indentations and the degrees of spinal cord flattening. Despite comparable postoperative improvement of the cord flattening between the two groups, the anterior procedure showed a significantly better functional result (P < 0.003) with no neurologic complications. In comparison, laminoplasty was associated with a significant neurologic deterioration immediately after surgery in four patients (33%). CONCLUSIONS: Anterior microsurgical decompression for a massive ossified posterior longitudinal ligament, although technically more demanding, seems counterintuitively safer than laminoplasty. For a better understanding of the underlying mechanism for neurologic worsening after laminoplasty, electrophysiologic monitoring of the spinal cord and the roots function seems essential not only during surgery, but also during presurgical positioning of the patient.

Adult↗
PubMed2006

Risk factors for childhood diarrhea incidence: dynamic analysis of a longitudinal study.

BACKGROUND: Several longitudinal studies have investigated factors associated with childhood diarrhea in developing countries. However, most studies have neglected important dynamic features of the longitudinal design and hierarchical interrelationships among the potential risk factors. METHODS: We conducted a longitudinal study of 902 children, age 0 to 36 months at baseline, in a large urban center in northeastern Brazil. Diarrhea data were collected by following children from October 2000 until January 2002 with biweekly home visits. We used a dynamic time-to-event analysis to account for several longitudinal features. We applied an effect-decomposition strategy to quantify direct and indirect effects of risk factors grouped in different blocks. RESULTS: Child's age and an autoregressive effect of past diarrhea episodes explained some of the decline of diarrhea incidence observed throughout the study (from more than 14 episodes to 2 episodes per child-year), a phenomenon already observed but not explained in other longitudinal diarrhea studies. We identified the following major diarrhea determinants: low socioeconomic status, poor sanitation conditions, presence of intestinal parasites, and absence of prenatal examination. The effect of socioeconomic status was mediated mostly by living and sanitation conditions. CONCLUSION: Our study shows important advantages of applying a dynamic analysis approach to longitudinal observational studies of diarrhea or other acute diseases and highlights the complex interrelationships of diarrhea determinants. Our results confirm the importance of sanitation as a major determinant of child health in urban settings of developing countries.

Brazil↗
PubMed2004

Cross-sectional versus longitudinal performance assessments in the management of diabetes.

BACKGROUND: Performance assessments help to quantify the level of adherence with practice standards and are often used to measure and compare the quality of care. However, most performance assessments are based on a cross-sectional analysis of patient information, whereas patient care is inherently longitudinal. This discordance could confound the relationship between the performance measure and the true quality of care. OBJECTIVE: The objective of this study was to illustrate differences in performance assessment as measured by a traditional cross-sectional analysis compared with a longitudinal analysis. METHODS: We conducted a cross-sectional and longitudinal analysis of a cohort of diabetic patients in an integrated delivery system having primary care visits and hemoglobin A1c (HBA1c) testing in both 1999 and 2000. RESULTS: In the cross-sectional analysis of 4661 patients, we found a modestly increasing proportion achieved an HBA1c level of <8.0%: 73.1% in 1999 and 75.6% in 2000. Longitudinal analysis, however, suggested that certain subsets of patients were more likely to switch from good to poor control or retain their level of poor control over the 2 years studied. In particular, compared with whites, blacks were 1.76 (95% confidence interval [CI], 1.31-2.37) times as likely to switch from good to poor control and only 0.56 (95% CI, 0.41-0.76) times as likely to switch from poor to good control. Patients aged 35 to 49 were 2.54 (95% CI, 1.79-3.45) times as likely to switch from good to poor and only 0.66 (95% CI, 0.47-0.94) times as likely to switch from poor to good control than patients over age 64 years. CONCLUSIONS: Cross-sectional performance assessments could mask changes in diabetes control among individuals belonging to a cohort and, conceptually, are poorer indicators of care process than longitudinal measures. In addition, longitudinal analyses suggest the influence of patient sociodemographic factors on the performance assessment that should be accounted for when comparing quality of care for diabetes.

Age Factors↗
PubMed2003

Bayesian approaches to joint cure-rate and longitudinal models with applications to cancer vaccine trials.

Complex issues arise when investigating the association between longitudinal immunologic measures and time to an event, such as time to relapse, in cancer vaccine trials. Unlike many clinical trials, we may encounter patients who are cured and no longer susceptible to the time-to-event endpoint. If there are cured patients in the population, there is a plateau in the survival function, S(t), after sufficient follow-up. If we want to determine the association between the longitudinal measure and the time-to-event in the presence of cure, existing methods for jointly modeling longitudinal and survival data would be inappropriate, since they do not account for the plateau in the survival function. The nature of the longitudinal data in cancer vaccine trials is also unique, as many patients may not exhibit an immune response to vaccination at varying time points throughout the trial. We present a new joint model for longitudinal and survival data that accounts both for the possibility that a subject is cured and for the unique nature of the longitudinal data. An example is presented from a cancer vaccine clinical trial.

Bayes Theorem↗
PubMed2004

The utility of the zero-inflated Poisson and zero-inflated negative binomial models: a case study of cross-sectional and longitudinal DMF data examining the effect of socio-economic status.

OBJECTIVES: To examine the utility of the zero-inflated Poisson (ZIP) and zero-inflated negative binomial (ZINB) modelling approaches for modelling four sets of dental caries data from the same cohort study [with particular attention to the influence of childhood socioeconomic status (SES)]: cross-sectional data on the deciduous dentition at age 5 years; cross-sectional data on the permanent dentition at age 18 and 26 years; and longitudinal data on caries increment between ages 18 and 26 years. METHODS: Data on dental caries occurrence at ages 5, 18 and 26 years were obtained from the Dunedin Multidisciplinary Health and Development Study (DMHDS). ZIP and ZINB models were fitted to the cross-sectional (n = 745) and longitudinal (n = 809) data sets using Stata (Intercooled Stata 7.0). The dependent variables for the three cross-sectional analyses were the DMFS indices at age 5, 18, and 26 years, and net DFS increment (NETDFS) was the dependent variable for the longitudinal analysis. RESULTS: The empty ZIP model was a poor fit for all four data sets, whereas the empty ZINB model showed good fit; consequently both the cross-sectional and longitudinal analyses were conducted using ZINB modelling. Being in the high-SES group during childhood was associated with a greater probability of being caries-free by age 18 years, over and above that which would be expected from the negative binomial process. Low childhood SES also had the largest coefficient in the modelling of the negative binomial process, but at age 5 years, where the adjusted mean dmfs score in the low-SES group was 6.8 (compared with 4.7 and 2.9 in the medium- and high-SES groups, respectively). The substantial SES differences which existed at age 5 years (in the deciduous dentition) had reduced somewhat by age 18 years, and had widened again by age 26 years. In the longitudinal analysis, "baseline" caries experience (age 18-year DMFS) was a predictor both of being an extra zero and of caries severity. CONCLUSION: This investigation of the utility of the zero-inflated approach for modelling both cross-sectional and longitudinal caries data has shown that ZIP/ZINB models can provide new insight into disease patterns. It is anticipated that they will become increasingly useful in epidemiological studies that use the DMF index as the outcome measure.

Adolescent↗
PubMed2005

The precision of longitudinal lung function measurements: monitoring and interpretation.

BACKGROUND: The efficacy of decision making based on longitudinal spirometric measurements depends critically on the precision of the available data, which is determined by the magnitude of the within-person variation. AIMS: Firstly, to describe and investigate two statistical methods-a pairwise estimate of within-person standard deviation s(p) and the reliability coefficient G-for use in the monitoring of precision of longitudinal measurements of forced expiratory volume in one second (FEV1). Secondly, to investigate the effect of longitudinal data precision on the detectable excess rate of decline in FEV1. METHODS: The authors "monitored" retrospectively on a yearly basis the magnitude of the within-person variation s(p) and the coefficient G in 11 workplace based spirometric monitoring programmes conducted from 1987 to 2001 on 12 729 workers in various industrial plants. RESULTS: The plant-specific mean values s(p) (range 122-166 ml) and G (range 0.88-0.95), averaged over all years of follow up, correlated well with the plant-specific within-person standard deviation s(r) (range 130-177 ml) estimated from all longitudinal data. The correlations were 0.90 for s(p) and 0.68 for G. The average precision of the longitudinal FEV1 measurements affected the duration of follow up needed to identify a "true" excess rate of decline in FEV1 in an individual. CONCLUSIONS: The results show that monitoring of longitudinal spirometry data precision (1) allows that data precision can be improved or maintained at levels that allow individuals with a rapid decline to be identified at an earlier age; and (2) attaches a measure of precision to the data on which decision making is based.

Data Interpretation, Statistical↗
PubMed2006

Analysis of longitudinal data: the integration of theoretical model, temporal design, and statistical model.

This article argues that ideal longitudinal research is characterized by the seamless integration of three elements: (a) a well-articulated theoretical model of change observed using (b) a temporal design that affords a clear and detailed view of the process, with the resulting data analyzed by means of (c) a statistical model that is an operationalization of the theoretical model. Two general varieties of theoretical models are considered: models in which the time-related change of primary interest is continuous, and those in which it is characterized by movement between discrete states. In addition, two general types of temporal designs are considered: the longitudinal panel design and the intensive longitudinal design. For each general category of theoretical models, some of the analytic possibilities available for longitudinal panel designs and for intensive longitudinal designs are discussed. The article concludes with brief discussions of two issues particularly relevant to longitudinal research--missing data and measurement--and a few words about exploratory research.

Humans↗
PubMed1994

Discrepancies between longitudinal and cross-sectional change in ventilatory function in 12 years of follow-up.

We compared the age dependence of cross-sectional and longitudinal changes in ventilatory function. FEV1, FVC, and data on chronic respiratory symptoms were obtained from 4,395 adults in a longitudinal survey of normal populations in two different areas in the Netherlands. They participated in up to five surveys at 3-yr intervals between 1972 to 1973 and 1984 to 1985. The ventilatory function in the oldest cohorts is substantially lower than might have been expected from the longitudinal change in the youngest cohorts. This holds for males and females, smokers and nonsmokers, subjects with or without symptoms, and for both survey populations. The robustness of the findings is demonstrated by various data-analytic strategies or omitting one or two of the five surveys from the analysis. Selective loss to follow-up cannot explain the discrepancy. It is concluded that the main differences between our longitudinal and cross-sectional findings may be due to a cohort effect. The implication is that in longitudinal studies of populations at risk, reference equations based on cross-sectional surveys may overestimate longitudinal change and hence lead to underestimating effects of exposure. Similarly, in clinical studies, accelerated decline in ventilatory function may be underrated if it is compared with cross-sectional standards. In older people at any one age the ventilatory function seems to improve in successive birth cohorts.

Adult↗
PubMed1999

Diurnal variation in lung function in subgroups from two Dutch populations: consequences for longitudinal analysis.

We studied circadian variation in FVC, FEV1, PEF, TLC, VC, and RV between 9:00 A.M. and 9:00 P.M. and analyzed how this variation affected estimated longitudinal change. Data from 876 adults were obtained in a longitudinal survey of samples from two Dutch areas. Subjects participated in four surveys held at 3-yr intervals between 1975 and 1985. FVC, FEV1, PEF, and VC increased from 9:00 A.M. until noon and decreased afterwards. TLC was constant over the day, whereas RV decreased from 9:00 A.M. to noon. Average variation in FVC, FEV1 and PEF, expressed as percentages of average level, was 4. 8% (200 ml), 2.8% (86 ml), and 3.1% (250 ml/s), respectively. These results are compatible with circadian changes in airway size. No differences in variability were found between men and women. Significantly larger changes between 9:00 A.M. and noon were found in young adults, smokers, and those with respiratory symptoms than in other subgroups. Adjustment for diurnal variation reduced, albeit slightly, residual standard deviations of estimated longitudinal declines. Average diurnal change was large relative to underlying longitudinal change. Its effect on longitudinal change within an individual can therefore be large depending on age, smoking habits, symptomatology, number of visits, time of measurement, and difference in time between measurements. However, when people are measured at random times during the day for at least three visits, or when measurements are made after 11:00 A.M., effects of diurnal variation in pulmonary function on estimated average longitudinal decline are minimal.

Adult↗
PubMed1982

Noncomparability of longitudinally and cross-sectionally determined annual change in spirometry.

Annual decline in lung function determined longitudinally is often compared with predicted decline determined cross-sectionally. To test this comparison, spirometric data were collected 5 times over 5 yr from 52 adult male Caucasians. The age regression coefficient for FEV1 and FVC, determined cross-sectionally at each visit, was more than twice the longitudinal annual change computed from the same data as the mean of the slopes of each subject's regression lines. The discrepancy persisted even when the first visit was deleted to reduce learning effects on longitudinal estimates. This discrepancy may be partly explained by the sensitivity of cross-sectional analyses to past noxious influences, whereas longitudinal analyses are sensitive only to influences that continue to affect annual decline during the study period. We also found historical evidence of an increase in height-specific VC, which would artifactually steepen cross-sectionally determined regression lines. Thus, observed longitudinal changes of study cohorts should be compared with control longitudinal data.

Adult↗
PubMed2003

Identification of genes for complex disease using longitudinal phenotypes.

Using the simulated data set from Genetic Analysis Workshop 13, we explored the advantages of using longitudinal data in genetic analyses. The weighted average of the longitudinal data for each of seven quantitative phenotypes were computed and analyzed. Genome screen results were then compared for these longitudinal phenotypes and the results obtained using two cross-sectional designs: data collected near a single age (45 years) and data collected at a single time point. Significant linkage was obtained for nine regions (LOD scores ranging from 5.5 to 34.6) for six of the phenotypes. Using cross-sectional data, LOD scores were slightly lower for the same chromosomal regions, with two regions becoming nonsignificant and one additional region being identified. The magnitude of the LOD score was highly correlated with the heritability of each phenotype as well as the proportion of phenotypic variance due to that locus. There were no false-positive linkage results using the longitudinal data and three false-positive findings using the cross-sectional data. The three false positive results appear to be due to the kurtosis in the trait distribution, even after removing extreme outliers. Our analyses demonstrated that the use of simple longitudinal phenotypes was a powerful means to detect genes of major to moderate effect on trait variability. In only one instance was the power and heritability of the trait increased by using data from one examination. Power to detect linkage can be improved by identifying the most heritable phenotype, ensuring normality of the trait distribution and maximizing the information utilized through novel longitudinal designs for genetic analysis.

Cardiovascular Diseases↗
PubMed1986

Longitudinal approach to assessing maximal aerobic power during growth: the European experience.

This review deals with the principle and constraints of conducting longitudinal studies on exercise in children. As with cross-sectional studies, longitudinal ones have advantages and constraints: the different types of such designs as mass studies, population studies, or prospective cohort studies should be therefore selected to minimize their possible drawbacks. Other problems of longitudinal studies, such as the age span studied, time and sequential measurement effects, or interventional effects, have to be controlled by statistical measures and study design. In longitudinal studies ad hoc research groups working in field laboratories are for many reasons more flexible than permanent teams using institutional laboratories. Only direct determinations of maximal aerobic power should be used in longitudinal studies. These should be accompanied by such measurements as body height, body mass, lean body mass, and peak height velocity and by such health indicators as daily physical activity, blood pressure, smoking habits, and blood lipids. Examples for this approach are given in this paper, and general issues of longitudinal studies are discussed from the economic and ethical point of view.

Adolescent↗
PubMed1997

Peak expiratory flow from maximum expiratory flow volume curves in a community population: cross-sectional and longitudinal analyses.

The data from a longitudinal population study in Tucson, Arizona, were used to describe the development and decline with age of the peak expiratory flows (PEF) from maximum expiratory flow-volume (MEFV) curves derived using a computer-linked pneumotachometer. Subjects had performed at least one technically acceptable MEFV test in 9 of the first 11 surveys (1972-1989). There were 2,724 subjects with adequate MEFV curves, and thus PEF, in the first survey, but only 1315 in the 11th survey. The subjects were stratified based on responses to questionnaires into nonsmoking healthy subjects and others. The PEF were analysed cross-sectionally and longitudinally using data from the 6th-11th surveys (1979-1989). For longitudinal analysis, the reference population had 397 males with 1,153 observations, and 534 females with 1,700 observations. The resulting equations were compared, evaluating differences between the longitudinal and cross-sectional equations, and between reference and nonreference longitudinal populations. The results show that there were effort-dependent effects in absolute values of PEF, even after editing. Nevertheless, as with most MEFV measures in reference populations, PEF had an early increase in the rate of development, followed by a plateau phase, followed by a constant rate of decline. The ages at which changes in growth rates of PEF occurred differed by gender. The longitudinal data in adults showed a less steep decline with age compared to the cross-sectional data, as found previously for the other MEFV variables. Males in the nonreference group did not reach the same maximum level and had a steeper decline throughout adult life than did males in the reference group; females were similar. Asthmatics of both genders had slightly greater declines compared to the other nonreference subjects.

Adolescent↗
PubMed1993

In vitro response of the human anal canal longitudinal muscle layer to cholinergic and adrenergic stimulation: evidence of sphincter specialization.

A study was performed to determine the in vitro response of the longitudinal smooth muscle layer (conjoined longitudinal coat) of the human and canal to cholinergic and adrenergic stimulation, and to compare this with similar features of the internal anal sphincter (IAS) and rectal smooth muscle. Tissue was obtained from abdominoperineal and anterior resection specimens, and strips of muscle mounted for isometric tension recording in superfusion organ baths. Both conjoined longitudinal coat and IAS strips generated and maintained spontaneous myogenic tension (mean(s.e.m.) 0.10(0.01) and 0.48(0.04) g per mg tissue respectively), whereas equivalent rectal smooth muscle did not. Stimulation of muscarinic (cholinergic) receptors caused contraction of strips from the conjoined longitudinal coat and rectal smooth muscle layers in a dose-dependent manner (10(-7)-10(-4) mol/l); however, IAS strips relaxed (10(-6)-10(-4) mol/l). Activation of alpha-adrenergic receptors in conjoined longitudinal coat and IAS strips produced concentration-dependent contraction (10(-7)-10(-4) mol/l). In comparison, rectal smooth muscle relaxed. All muscle layers relaxed in response to beta-adrenoceptor stimulation. These data indicate that in the anal canal both the conjoined longitudinal coat and IAS are specialized sphincteric smooth muscles.

Aged↗
PubMed2004

Differential effect of nitric oxide synthase inhibition on sigmoid colon longitudinal and circular muscle responses to nicotine and nerve stimulation in vitro.

BACKGROUND: Nicotine has been shown to release nitric oxide from nerves in human sigmoid colon. This effect has been used to investigate the innervation and functional relationship of the longitudinal and circular muscle layers. METHODS: Strips of longitudinal and circular muscle were obtained from 19 patients with colorectal cancer. The strips from ten patients were subjected to electrical field stimulation (EFS) in vitro using stimulus parameters for selective stimulation of nerves. The effect of nicotine 1-10 micromol/l on EFS responses was then measured in the presence and absence of a nitric oxide synthase inhibitor, nitro-L-arginine methyl ester (L-NAME) 200 micromol/l. The effect of nicotine on spontaneous activity was investigated in the muscle strips from the other nine patients. RESULTS: Both longitudinal and circular strips responded to EFS with contraction. The time to achieve a peak contractile response (time to peak; TTP) was significantly longer (P<0.001) in circular strips. L-NAME reduced the mean(s.e.m.) TTP in circular muscle from 23.3(2.0) to 17.2(1.5) s (P=0.007) and altered its pattern of response to resemble that of longitudinal muscle. Nicotine 10 micromol/l reduced the contraction to EFS in circular (P<0.001) but not in longitudinal (P=0.347) muscle. The nicotine-induced reduction in circular muscle contraction was blocked by L-NAME 200 micromol/l (P=0.005). CONCLUSION: These findings suggest that nitric oxide release on neural stimulation is greater in circular than in longitudinal muscle.

Colon, Sigmoid↗
PubMed1991

Linear relationship between the volume of hypertrophic chondrocytes and the rate of longitudinal bone growth in growth plates.

In this study, we tested the hypothesis that hypertrophic cell volume varies directly with the rate of longitudinal bone growth. The volume of hypertrophic chondrocytes (using stereological techniques) and longitudinal bone growth per 24 h (using oxytetracycline labeling techniques) were measured in the proximal and distal radial growth plates and the proximal and distal tibial growth plates of 21- and 35-day-old hooded rats and 21- and 35-day-old Yucatan pigs. We demonstrated a high coefficient of correlation (rats 0.98, pigs 0.83) between the final volume of hypertrophic chondrocytes and the rate of longitudinal bone growth over a wide range of growth rates and volumes of hypertrophic chondrocytes. In addition, we demonstrated a positive linear relationship between the rate of longitudinal bone growth and the final volume of hypertrophic chondrocytes. The slope of the regression line was different for rats than for pigs. The relationship was independent of the location of the growth plate in the animal and the age of the animal. The data suggest that mechanisms regulating volume changes in hypertrophic chondrocytes may exist and that chondrocytic volume increase is a major determinant of the rate of longitudinal bone growth. However, the relative contribution of cellular hypertrophy to longitudinal bone growth may be different in rats than in pigs.

Animals↗