The metacarpal index of infants.

Abstract

Some infants appear to have long fingers, and since arachnodactyly is a feature of Marfan's syndrome, it is important to know whether a baby's long fingers are outside the normal range.In 1960, Sinclair, Kitchin, and Turner observed that arachnodactyly in Marfan's syndrome was related to the length and breadth of the metacarpal bones and showed that the metacarpal index was a useful criterion of arachnodactyly. The index is calculated by measuring the 2nd, 3rd, 4th, and 5th metacarpals. The sum of the lengths is divided by the sum of the breadths, as measured at the midpoint of each metacarpal. Sinclair's measurements were carried out mainly on adults, and it is not known if they are relevant to babies, or to children before the appearance of secondary ossification centres in the metacarpals.The aim of this study was to obtain values for the metacarpal index of children aged 2 years and under, and to compare the normal values with the indices of some infants who were thought to have long or short fingers.Material and Method Dr. Alice Stewart kindly allowed us to use x-rays of the hands of normal children who had been observed in a longitudinal study of growth at Oxford (Acheson, Kemp, and Parfit, 1955). The x-rays of both hands of 25 girls and 25 boys had been taken at 6 months, 12 months, 18 months, and 24 months. The children had been examined and were known to be healthy.The metacarpal index of each hand was measured in each child at all four ages by a method similar to that described by Sinclair et al. (1960). The mid-point of the metacarpal was identified by observation rather than by measurement; in practice this causes a difference of less than 0 * 5 mm. in the width recorded. The maximum length was measured, and in older infants the distal border of the epiphysial ossification centre was taken to be the end of the metacarpal. All measurements were recorded to the nearest 0 5 mm. ResultsNormal children. Table I shows the mean metacarpal index of the right and left hands of the Received February 24, 1969. 50 children at the ages of 6, 12, 18, and 24 months, as well as the standard deviation at each age. There is no significant difference between the right and left hands at any age.Thoughout the first two years girls have a greater index than boys, but the difference is small. A detailed comparison of the mean indices for each metacarpal of the 50 children at the age of 6 months showed that each metacarpal contributed to the higher mean metacarpal index observed in the girls, and their metacarpals were both longer and narrower than the boys.There is a tendency for the index to increase with age; thus it is 0K17 more in boys and 0 24 more in girls at the age of 24 months than at 6 months.

Clinical Features of Congenital Contractural Arachnodactyly

“…In roentgenograms, the metacarpal index in this series increased compared with that of normal controls reported by Parish (1966) and Joseph and Meadow (1969). Tatsuno et al (1983) reported the same results.…”

“…The metacarpal index was measured in 8 cases and it ranged from 7.2 to 9.4. The metacarpal index of these cases increased compared with that of normal control reported by Parish (1966) and Joseph and Meadow (1969). Spinal deformity was observed in 7 cases.…”

Limb Malformations

“…On the proximal end of these metacarpals, pseudoepiphyses and pseudoepiphyseal notches can occur normally (most prevalent on metacarpals II and V), while Humerus and radius/ulna in a-e, hands in l-p, and femur and tibia/fibula in f-k. a Newborn. The metacarpal index is a measure of relative slenderness (Sinclaire et al 1960;Joseph and Meadow 1969;Parish 1966). b An 8-year-old.…”

Hands

“…In infancy before the appearance of the metacarpal epiphyses and up to about 2 years of age the index remains constant (5.2 in male; 5.5 in female infants). The index rises during childhood, reaching a peak at about 16 years of age, and then falls slightly during adult life (Walker 1979;Rand et al 1980;Joseph and Meadow 1969 The epiphyses in the hands frequently undergo minor changes in shape, size or structure, many of which occur in the general population as normal anatomical variants. One example is the occurrence of multiple centers of ossification in the proximal phalanx of the thumb.…”