Biomedical Engineering Reference
In-Depth Information
(
Figure 4.4
). The names used for the tarsal bones of all
primates, including humans, differ somewhat from those
used for other orders. The distinct heel process (calcaneal
tuberosity) on the proximal end of the calcaneus is a point
of substrate contact in many postures, patterns of resting,
and/or locomotion.
The metatarsals and phalanges of the foot are typical
well-developed long bones. The mobility of all of the digits
as well as the divergent, pseudo-opposable big toe and
other modifications are described in the sections on feet
and digits (see the sections “Overview of limbs” (above)
and “Musculature of hindlimb” (below)). In humans, the
convergence of the big toe as part of the development of
a bipedal striding gait has resulted in numerous differences
between the foot of humans and that of nonhuman
primates. Despite this, the foot of nonhuman primates is
still in many ways more similar to that of humans than to
other highly specialized animals. As in the hand, the muscle
tendons of the nonhuman primate foot and entire lower
limb have more numerous sesamoid bones than their
human equivalents.
scapula. The sternoclavicular joint is a synovial joint with
an articular disc within the capsule. Movement of the
clavicle includes elevation and depression, retraction and
protraction, and rotation around the long axis. (See
description of the curvature of the clavicle in the section
“Skeleton of forelimb” above.) Mobility in this joint is
a critical component of most of the movements of the
forelimb as a whole, particularly abduction. A second
synovial joint is the acromioclavicular joint which unites
the scapula and clavicle at the lateral margin of the shoulder
immediately superior to the glenohumeral joint. As in the
previous articulation, unrestricted movement in this joint is
essential for a large variety of movements of the extremity.
The last synovial joint in this region is the glenohumeral, or
shoulder joint, which is the articulation between the
pectoral girdle and the proximal limb segment. Movement
within the joint capsule is free, but movement in this joint
must be accompanied by movement in the other three areas
in order for a full range of motion to be accomplished. The
full range of motion including circumduction in the
shoulder region of nonhuman primates is not very different
than that of humans (
Chan, 2008
). (See any functional
anatomical text of human anatomy for a more detailed
explanation of the movements and functioning of the
shoulder region.)
The elbow joint capsule includes both the elbow joint
and the proximal radioulnar articulation. The degree of
extension and flexion in the elbow joint varies among
species and is correlated to both the length of the olecranon
process and locomotor behavior. In all cases the elbow joint
strongly resembles that of humans both in configuration
and in range of motion. On either side of the joint fan-
shaped collateral ligaments attach broadly to the ulna and
the annular ligament surrounding the radial head to allow
a larger range of extension than found in most other
mammals.
The radioulnar joints include a proximal articulation
enclosed in the same capsule as the elbow joint and a distal
articulation whose capsule communicates with that of the
wrist. In the proximal radio-ulnar joint, the head of the
radius rotates freely within the confines of a strong annular
ligament. In most primates both the radius and ulna artic-
ulate with the proximal carpal row, but in Hominoidea the
head of the ulna is separated from the carpus by an articular
disc and thus does not participate directly in the articulation
between the forearm and hand (
Lewis, 1972, 1974;
Sarmiento, 1988
). Between the two radioulnar synovial
articulations lies a strong interosseous membrane which
transmits forces between the radius, the dominant forearm
component in the wrist joint, and the ulna, the dominant
forearm component in the elbow joint. The predominant
fiber orientation in the interosseous membrane reflects the
transmission of either primarily tensile forces in species
utilizing extensive suspensory locomotion or compressive
Joints of Forelimb
The joints of the forelimb and hindlimb of nonhuman
primates (
Sullivan, 1933
) resemble very closely the
equivalent joints in humans. The primary difference
between many of these joints and those of other mammals
is a larger range of mobility. Unlike many other animals
where limb use is almost exclusively postural or locomo-
tive, primates also utilize their limbs in numerous non-
locomotive activities (e.g. feeding and social behavior).
Primate locomotor patterns tend to be varied not just in
relation to speed but also to different substrates and uses.
For example, the same species may walk quadrupedally on
the ground, use both suspensory and quadrupedal loco-
motion either above or below the branches in trees, and
stand or even walk on their hindlimbs. Thus the limbs are
usually not as highly specialized for a single repetitive
motion (
Oxnard, 1973
) and the potential movements in
their joints reflect their diverse locomotor and postural
repertoires. The actual range of motion permitted in any
given joint is species specific and is influenced by age, sex,
and environment (
DeRousseau et al., 1986; Turnquist,
1983; Turnquist and Kessler, 1989b
).
The highly mobile shoulder region consists of three
synovial joints and one muscular complex which acts as
a joint. The muscular complex which acts a joint is the
movement of the scapula upon the thorax. This movement
is without any direct bony articulations and includes
movements in three planes (protraction and retraction,
elevation and depression, and rotary movements) which
result in the glenoid fossa moving in the direction contrary
to the movement of the caudal (inferior) angle of the
