Why Measurements Are Useful

Growth is the essence of the developing organism. Physical growth starts shortly after fertilization and continues throughout pregnancy, childhood, and adolescence. It may even occur in the adult. Growth of different parts of the body follows a predictable schedule during normal development and maturation. This timetable of development is influenced and controlled by many genetic and environmental factors. Any disturbance in the "normal" sequence of development and growth may lead to disproportion of physical features. These imbalances may be transient and can sometimes be compensated for by later catch-up growth. Most syndromes with dysmorphic features, however, display more or less recognizable patterns of disproportionate growth.

The growth of different parts of the body can be observed and measured at one point in time or over specific periods of time. It can be expressed as a number, a comparison, a percentile, or standard deviation from the norm. The comparison may be either with the growing individual, at different ages (so that one can observe the changes over time), or with standardized normal values (obtained from either cross-sectional or longitudinal studies of a specific group of individuals). One can assess and compare differential growth of the various parts of the body.

Longitudinal studies follow a group of individuals or cohort over time, with standardized measurements obtained at precise intervals. Longitudinal studies are difficult because they include a large number of individuals, who must be measured at set intervals, using the same techniques, and, ideally, by the same person(s). The work involved and the time span are enormous. Longitudinal studies provide data on patterns of growth and growth velocity. Velocity curves are valuable in demonstrating the rate of change of a specific dimension with time.

Cross-sectional studies utilize data obtained from a large number of individuals of the same age, usually collected at one time. Cross-sectional studies are technically less difficult to do because they do not rely on the long-term cooperation of many individuals. Cross-sectional studies are used mainly as standards of physical measurement and provide less information about variability, velocity, or patterns of growth over time.

Statistical methods and data collection methods involved in the construction of normal growth curves will not be discussed further. Details are available in the literature references listed here. It is important for the reader to be aware that the various standards provided in this book often come from different populations using different methodologies and so are not really comparable. Nevertheless, they are the only measurements presently available.

Most syndromes with dysmorphic features show disturbances of growth either of the entire body or of certain body parts. In the past, various unusual features have been expressed in qualitative terms such as: short stature, long fingers, or other terms that imply a comparison with other body proportions. An impression of the patient or a "gestalt" is formed in the reader's mind. The more objective way to assess body proportions is by quantitative measurement. This is especially important when the disturbance in growth involves only a specific body area or can be related to a disease process, because it may give insight into the basic mechanisms underlying the growth disturbance and thus the pathogenesis of the disease.

Comparison of the dimensions obtained in a specific individual or patient with a normal standard curve requires three things:

1. standardized landmarks on the body from which and to which measurements can be taken;

2. standardized methods of taking measurements;

3. standard equipment.

The landmarks that we will use are shown in Fig. 2.1 and will be referred to at the beginning of each measurement section. In general they represent surface landmarks of underlying bony structures that can be palpated easily through the skin. To obtain a minimum degree of accuracy in physical measurement, the examiner should be aware of these landmarks. There are individual anatomical variations, especially in patients with congenital anomalies or syndromes with dysmorphic features. Landmarks for measurements of the head and facial structures will be discussed in detail in Chapter 7.

Summary

By taking accurate physical measurements we can express and communicate observations on growth, proportion, and disturbance of the developmental process in quantitative terms. Single measurements are

Foot Anatomy Landmarks

Foot Foot width length

Figure 2.1 Body landmarks to and from which measurements can be taken.

Foot Foot width length

Figure 2.1 Body landmarks to and from which measurements can be taken.

meaningless in isolation. They are valuable only in relation to other parameters and in comparison with normal values.

Pregnancy And Childbirth

Pregnancy And Childbirth

If Pregnancy Is Something That Frightens You, It's Time To Convert Your Fear Into Joy. Ready To Give Birth To A Child? Is The New Status Hitting Your State Of Mind? Are You Still Scared To Undergo All The Pain That Your Best Friend Underwent Just A Few Days Back? Not Convinced With The Answers Given By The Experts?

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