title: Functional hand proportion is approximated by the Fibonacci series.
abstract: The debatable relationship of functional human hand proportion with the Fibonacci  series has remained an obscure scientific enigma short of clinical interest.  The main difficulty of proving such a relationship lies in defining what  should constitute true functional proportion. In this study, we re-evaluate  this unique relationship using hand flexion creases as anatomical surrogates for  the functional axes of joint rotation. Standardised desktop photocopies of palmar  views of both hands in full digital extension and abduction were obtained  from 100 healthy male volunteers of Chinese ethnicity. The functional axes  were represented by the distal digital crease (distal interphalangeal joint, DIPJ),  proximal digital crease (proximal interphalangeal joint, PIPJ), as well as the midpoint  between the palmar digital and transverse palmar creases (metacarpophalangeal  joint, MCPJ). The ratio of DIPJ-Fingertip:PIPJ-DIPJ:MCPJ-PIPJ (p3:p2:p1)  was measured by two independent observers and represented as standard  deviation about the mean, and then compared to the theoretical ratio of 1:1:2.  Our results showed that, for the 2nd to 5th digits, the p2:p3 ratios were 0.97 ±  ± 0.09, 1.10 ± 0.10, 1.04 ± 0.12, and 0.80 ± 0.08, respectively; whilst the  p1:p2 ratios were 1.91 ± 0.17, 1.98 ± 0.14, 1.89 ± 0.16, and 2.09 ± 0.24,  respectively. When the data were analysed for all digits, they showed a combined  p3:p2:p1 ratio of 1:0.98:2.01. In conclusion, our results suggest that  functional human hand proportion, as defined by flexion creases, is approximated  by the Fibonacci series.
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: K W-Q
authors.initials: KW
authors.lastname: Choo
authors.forename: W-K
authors.initials: WK
authors.lastname: Quah
authors.forename: G-H
authors.initials: GH
authors.lastname: Chang
authors.forename: J Y
authors.initials: JY
authors.lastname: Chan
mesh_terms: D000293:Adolescent; D000328:Adult; D044466:Asian People; D002681:China; D005384:Finger Joint / Q000033:anatomy & histology* / Q000502:physiology*; D005385:Fingers / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D008297:Male; D016059:Range of Motion, Articular; D012399:Rotation