Segmental 2:4 digit ratio. Unilateral, bilateral and hand-type differences in men

Abstract

Most studies of the 2:4 digit ratio (DR) of the human hand have analyzed its possibilities for use as an indicator of the functional, psychological, and, with rare exception, morphological features of the body. Each of the functional flexor segments (each phalanx) contributes to the common variability of the total digital length. The aim of this study was to determine patterns in the relationships between each segmental digit ratio (SDR) and the overall 2:4 DR. We studied the variability of the SDRs in comparison with the general 2:4 DR of 202 young males aged 16-21 years. The length of the functional segments of the digits was measured between the flexor skin furrows on the palmar surface. The change in the SDR means that values can be ranked as follows: proximal SDR (SDR-P) > DR > distal SDR (SDR-D) > medial SDR (SDR-M). Bilateral differences are inherent in the segmental SDR-P. Most quantitative regularities inherent in the total 2:4 DR are also intrinsic to the 2:4 DR of the distal segment of the digit; in particular, this phenomenon is displayed in hands of the ulnar (male) type. Overall, the values of the distal rather than the other functional flexor segments of the second and fourth digits are similar in magnitude to the general 2:4 DR. At the same time, the greatest correlation and hence, the largest contribution to the total variability in the general DR is from the variability of the SDR-P values. Our data demonstrate the importance of various digit segment sizes in determining their overall length and the derivative ratios. © 2011 Elsevier GmbH.