Introduction to Sports Biomechanics: Analysing Human Movement ...

Bone fracture
THE ANATOMY OF HUMAN MOVEMENT
others can be easily felt (palpated) – some of these are the anatomical landmarks used to
estimate the axes of rotation of the body’s joints (see Box 6.2), which are crucially
important for quantitative biomechanical investigations of human movements in sport
and exercise.
Lumps on bones known as tuberosities or tubercles – the latter are smaller than the
former – and projections, known as processes, show attachments of strong fibrous
cords, such as tendons. The styloid processes (Figure 6.6(a)) on the radius and ulna
are used to locate the wrist axis of rotation in the sagittal plane. The acromion
process on the scapula (Figure 6.5) is often used to estimate the shoulder joint axis of
rotation in the sagittal plane (see Box 6.2).
Ridges and lines indicate attachments of broad sheets of fibrous tissue known as
aponeuroses or intermuscular septa.
Grooves, known as furrows or sulci, holes – or foramina, notches and depressions or
fossae – often suggest important structures, for example grooves for tendons. The
suprasternal notch (Figure 6.5) is often used to establish the trunk–neck boundary
for centre of mass calculations (see Table 5.1).
A projection from a bone was defined above as a process, while a rounded
prominence at the end of a bone is termed a condyle, the projecting part of which
is sometimes known as an epicondyle. The humeral epicondyles (Figure 6.6(b)) and
the femoral condyles (Figure 6.6(c)) are used, respectively, to locate the elbow and
knee axes of rotation in the sagittal plane.
Special names are given to other bony prominences. The greater trochanter on the
lateral aspect of the femur, shown in Figure 6.5, is often used to estimate the
position of the hip joint centre. The medial and lateral malleoli, on the medial and
lateral aspects of the distal end of the tibia (Figure 6.6(d)), are used to locate the
ankle axis of rotation in the sagittal plane.
The factors affecting bone fracture, such as the mechanical properties of bone and the
forces to which bones in the skeleton are subjected during sport or exercise, will not be
discussed in detail here. The loading of living bone is complex because of the combined
nature of the forces, or loads, applied and because of the irregular geometric structure of
bones. For example, during the activities of walking and jogging, the tensile and compressive
stresses along the tibia are combined with transverse shear stresses, caused by
torsional loading associated with lateral and medial rotation of the tibia. Although
the tensile stresses are, as would be expected, much larger for jogging than walking, the
shear stresses are greater for the latter activity. Most fractures are produced by such a
combination of several loading modes.
After fracture, bone repair is effected by two types of cell, known as osteoblasts
and osteoclasts. Osteoblasts deposit strands of fibrous tissue, between which ground
substance is later laid down, and osteoclasts dissolve or break up damaged or dead bone.
235