evaluation of physical maturity in adolescent mentally retarded boys

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  • J . ment. Defic. Res. (1973) 17, 89 89

    EVALUATION OF PHYSICAL MATURITYIN ADOLESCENT MENTALLY RETARDED BOYS

    A. T. RUNDLE and P. E. SYLVESTERSt. Lawrence's Hospital, Caterham, Surrey

    Bourtourline-Young, GreuHch, Gallagher, Cone and Heald (1968), in a studyof physical maturity at adolescence derived a formula for puberal maturity, stated as;

    0.5 (pubic hair rating) + 0.4 (testicular voiume rating) + 0-3 (axillary hair. rating) -f 0.5 = puberal age. . . . . , _ . _

    This equation, according to the authors, gives a quick and precise method forcalculating puberal maturity and correlates very highly with the clinical assessmentmade by five independent experienced investigators.

    The equation was derived from data on normal children of West Europeanorigin, and we considered that in view of the reported widespread abnormalities inmaturation of mentally retarded children (Rundle and Sylvester 1962, 1963 and1965; Sylvester and Rundle, 1962; Flory 1936; Mosier, Grossman and Dingman 1962;Dooren, 1967) its applicability to such an abnormal population should be assessed.

    METHODSPubic hair

    The five standards of Tanner (1962) were adopted since they correspond to the0-4 stages used by Bourtourline-Young et al. (1968).Axillary hair

    In our original publication (Rundle and Sylvester, 1963) axillary hair wasassessed by the four stage standards of Quaade (1955), i.e.,

    Stage 1 Lanugo during infancyStage 2 Occasional, pigmented and non-curlingStage 3 Sparse, pigmented and curlingStage 4 Fully developed axillary hair.As it appears that the first two stages correspond to the first three stages of

    Bourtourline-Young et al. (1968), some re-evaluation of our data was necessary.Genital development

    The five standard ratings of Tanner (1962) were used.Testicular volume

    Our methods for the estimation of testicular volume are reported in detailelsewhere (Rundle and Sylvester, 1962) which, briefiy, involve the measurement ofthe length and breadth and width of the testis through the scrotum by means ofmodified Harpcndcn skinfold calipers and the subsequent application of the formulaof Lambert (1951):

    Testicular volume =0 .71 X length X breadth X width.

    Received 26th January, 1973

  • 90 MENTALLY RETARDED BOYS

    The testicular volumes so obtained were then transposed into the scale rating ofBourtourline-Young et al. (1968) using the volume quoted by them.

    Skinfold thicknessSkinfold thickness was determined by means of the Harpenden skinfold calipers

    (Edwards, Hammond, Healy, Tanner and Whitehouse, 1955; Tanner and White-house, 1955) at the triceps and subscapular sites. For the purpose of this communica-tion only the triceps values have been included, but the findings derived from theseare equally applicable to those of the subscapular region.

    Skeletal ageStandardised X-rays of the hand and wrist were compared with standards

    (Greulich and Pyle, 1959) either blind on at least two occasions or until the differencesbetween consecutive assessments were less than one standard.

    Miscellaneous anthropometric dataStanding heights, sitting heights, biacromial widths and pelvic widths were

    measured to the nearest 0.1 cm using standard anthropometric techniques. Weightwas measured to the nearest 0.1 kg by a precision balance.

    Subject materialSixty-nine mentally retarded boys were selected after the elimination of those

    cases where genetic, metabolic, traumatic or infiammatory mechanisms could be thecause of their mental retardation. An age range of ten to seventeen was taken sincethe lower limit would include any cases with an early onset of puberty (as suggestedby Dooren, 1967) and the upper limit would include some cases who had achievedfull puberty (Rundle and Sylvester, 1963).

    RESULTSFig. 1 shows the puberal maturity index as determined by the formula of

    Bourtourline-Young et al. (1968) of all cases plotted against chronological age. TheTable 1

    Coefficients of correlation of seven variables against age [inyears), puberalmaturity index [see text), and puberal maturity index with age

    effect partialled outPuberal Index

    Variable Age Puberal Index {age partialled out)0.810.490.420.350.16

    0.29

    WeightStanding heightSitting heightBiacromial widthPelvic widthPuberal indexSkeletal age

    0.600.750.700.230.70

    0.870.790.740.390.63

    0.69

  • A. T. RUNDLE and P. E. SYLVESTER 91

    P 10 11 12 13 U IS U 17Chronological age (yrs)

    Fig. 1. Puberal maturity index (see text) of sixty-nine menially retarded boys,aged ten to seventeen years, plotted against chronological age.

    curve represents the yearly means smoothed by eye and demonstrates the pubertalspurt from thirteen to seventeen years which is in agreement with data on a similargroup of boys presented elsewhere (Rundle and Sylvester, 1962 and 1963). Althoughthere appears to be considerable scatter about the means, this is not so marked aswhen trsticular volume is used as the criterion (Fig. 2). The same data, i.e. puberalindex, is presented in Fig. 3, but plotted against skeletal age. The curve for the mean inFig. 3 resembles that of puberal index against age (Fig. 1), but the degree ofscatter isreduced, and more closely resembles the curve for testicular volume against skeletalage (Rundle and Sylvester, 1962). In Fig. 4 the triceps skinfoldthicknessofoursample(with some additional cases aged five to ten years) is plotted against age. The degreeof scatter not only reflects the low correlation between this variable and puberty(also shown in the data of Bourtourline-Young et al.^ 1968), but is probably greaterthan that which would be found in normal boys due to the heterogeneity of oursample. Fig. 4 casts serious doubt on the value of single estimates of this parameter ina cross-sectional survey.

    To make this study comparable to that of Bourtourline-Young et al. (1968),simple correlations between the puberal index and the seven variables are shown inTable 1. The two sets of correlations are not strictly comparable as the originalauthors correlated their variables with a puberal maturity judgement, but since theseauthors give a correlation between the clinical judgement and the puberal index as0.99, we consider that the degree of error arising from such a comparison is negligiblesince only general conclusions are drawn. Comparison of our correlations with those

  • 92 MENTALLY RETARDED BOYS

    Fig. 2. Testicular volume (deter-mined by the method of Rundleand Sylvester, (1962) of sixty-ninementally retarded boys, aged tento seventeen years, plotted againstchronological age.

    7 VChronological age (yrs)

    " 4

    toE 3

    .n

    7 B 9 U 12 13 USkeletal age (yrs)

    Fig. 3. Puberalmaturity index (seetext) of thirty-threementally retardedboys plotted againstskeletal age.

    of the original authors shows that, with the exceptions of skeletal age and weight, ourdata do not correlate as well as theirs. Weight is notoriously inaccurate and mostinfluenced by exogenous factors, and skeletal age has been shown not to differsignificantly from normal boys (Rundle and Sylvester, 1963), but it is difficult tosuggest a reason why, of all the variables investigated, these two parameters shouldbe contrary to the general trends. Also included in Table I are the intercorrelationsbetween puberal index and the several variables with the age effect partialled out.The effect of this procedure is, in all cases with the exception of the weight, to reducethe coefficient of correlation considerably. It is suggested that the lower correlationin our data is a measure in our sample of a core of abnormal rate of maturation, orpossibly both.

    In Fig. 5 the three physical maturity standards (pubic hair, genitalia and axil-lary hair) are plotted against testicular voiume. The horizontal bars indicate the

  • A. T. RUNDLE and P. E. SYLVESTER 93

    Fig. 4. Triceps skinfold thick-ness (mm) of sixty-two boys,aged five to seventeen years,plotted against chronologicalage.

    Age in yearsU 1> l 17

    25th, 50th and 75th percentile, and the two most mature ratings in each case havebeen combined since it is our experience that the separation of these requires thegreatest degree of experience and is most open to error. Analysis of this data rulesout the use of means and standard deviations as the results were fotind to exhibit aconsiderable degree of positive skewness, particularly in the first two (most immature)stages. Differences between the three variables and the differing degree of overlapbetween stages is further evidence of individual differences in rates of maturation.

    To test this further, thirty-four cases from our sample aged 10-13.5 years werere-examined to determine which physical criterion or combination of criteria firstindicated onset of puberty. Although it may be open to criticism, a testicular volumein excess of 5 ml, and in the other three criteria one or more stages above the pre-pubertat, were taken as evidence that the pubertal spurt had started. These resultsare given in Table 2. The variability in the criteria first presenting evidence ofpuberty is evident from Table 2, and confirms similar findings on mentally retardedboys and girls by Dooren (1967).

    DISCUSSIONSuperficially at least, data on growth and niaturation appear to be simple to

    collect, simpler to evaluate and give a reliable indication of normal physiologicalfunction, but experience soon indicates that this is not the case. Failure of growth andmaturation is regularly suggested as one of the most constant concomitants of mentalretardation with very little attention being paid to the nature of the group beinginvestigated other than their reduced intelligence. Most anthropometric surveys onthe mentally retarded have been criticised as either not segregating

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