Hand dominance and bilateral asymmetry in the structure of the second metacarpal

Abstract

Bilateral asymmetry in the structure of the second metacarpal was examined in relation to functional hand dominance in a large, clinically nonselected, healthy population sample from the Baltimore Longitudinal Study of Aging. Bilateral bone measurements were made from anteroposterior hand radiographs of a total of 992 individuals, 609 males and 383 females, with an age range of 19-94 years. Hand dominance was determined on the basis of personal impression. Total width and medullary width at the midshaft of the second metacarpal were measured to 0.05 mm using a Helios caliper. These two measurements were used to derive cortical thickness, cortical bone area, periosteal (total) area, medullary area, percent cortical area, and the second moment of area in the mediolateral plane. In both right and left-handed individuals, statistically significant side differences were found in the calculated bone areas and the second moment of area, with the dominant hand being larger. Cortical thickness did not show significant side-related differences for either handedness. These results show that functional handedness leads to periosteal and endosteal expansion of the second metacarpal cortex on the dominant side, increasing bone strength without increasing cortical thickness. This is the first time this pattern of asymmetry has been reported in left-handers as well as right-handers. Our results argue for the primacy of environmental (mechanical) effects in determining bilateral asymmetry of limb bone structural properties.

Limb bone bilateral asymmetry: variability and commonality among modern humans

“…This hypothesis is strongly supported by observations of greatly increased asymmetry between the playing and nonplaying arms of racquetball and tennis athletes (Jones et al, 1977;Krahl et al, 1994;Ruff et al, 1994;Kontulainen et al, 2001;Kontulainen et al, 2002;Bass et al, 2002), as well as between normal and mechanically compromised (i.e., paralyzed or otherwise mechanically restricted) limbs (Biewener and Bertram, 1993;Trinkaus et al, 1994). Left-handed individuals in the ''normal'' population have also been shown to have equivalent but reversed asymmetry in metacarpal dimensions compared to right-handed individuals (Roy et al, 1994). Such observations form the basis for using patterns of skeletal bilateral asymmetry in archaeological samples to infer asymmetry in mechanical loading due to behavior or pathology (e.g., Stirland, 1993;Churchill and Formicola, 1997;Mays, 2002).…”

Bilateral Asymmetry of Humeral Torsion and Length in African Apes and Humans

“…In humans, habitual lateralization of behaviours, possibly associated with this cerebral lateralization, has been shown to produce skel-etal asymmetries, and a number of osteological studies have established an association between lateralized mechanical loads and bone remodelling [Ruff and Hayes, 1983;Steele, 2000a, b;Lazenby, 2002;Stock and Pfeiffer, 2004]. In particular, upper limb asymmetries have been well documented in the skeleton of Homo sapiens with numerous studies showing how asymmetric loads influence upper limb morphology in human populations and professional athletes [Roy et al, 1994;Trinkaus et al, 1994;Kontulainen et al, 2002;Lazenby, 2002;Rhodes and Knüsel, 2005;Lazenby et al, 2008;Shaw and Stock, 2009a, b;Shaw, 2011]. Bilateral asymmetries in the upper limbs of great apes are, however, less well documented, even though these are potentially informative about the origins of functional lateralization in humans and non-human primates.…”

Morphological Assessment of Ethnic, Sex and Side Differences in the Human Radius Based on Intra-Regional and Side Ratios.

“…This bone is always changing throughoutchildhood by growth, and throughout adulthood by remodelling . Childhood growth is affected by intrinsic factors such as genetic background , hormonal activities and diet, and by extrinsic factors such as mechanical stresses during work and play (Miyamoto , 1925;Martin andSailer, 1957, 1959;Hiramoto , 1993;Trinkaus et al, 1994;Roy et al, 1994;Steele and Mays, 1995). Even the latter adult remodelling is known to be influenced by intrinsic and extrinsic factors, such as diet and daily activities .…”

“…Remarkable side differences in both bone length growth and remodelling at the distal parts for the paired humeri have been reported for sportsmen and sportswomen (Buskirk et al, 1956;Kings et al, 1969;Trinkaus et al, 1994;Roy et al, 1994;Steele and Mays, 1995). However, since they have often devoted their childhood and adolescence to training their functionally dominant arms, bone length growth and remodelling is often promoted in the distal region.…”

“…The upper limb bones always show delicate bilateral asymmetries in morphology, although they have macroscopically the outward appearance of symmetry. Therefore, many scholars have accumulated evidence that extrinsic factors, such as mechanical stresses from sports, can affect bone morphology and bilateral asymmetries for the paired upper limbs (Buskirk et al, 1956;Kings et al, 1969;Trinkaus et al, 1994;Roy et al, 1994;Steele and Mays, 1995).…”