Biomedical Engineering Reference
In-Depth Information
quadriceps is relaxed. A part of the quadriceps tendon covers
the anterior surface of the bone and is continued, as the patellar
ligament, to the tuberosity of the tibia. The patella articulates
on its posterior side with the patellar surface of the condyles
of the femur. The articular surface of the patella comprises a
larger, lateral facet and a smaller, medial one. Lateral disloca-
tion of the patella is resisted by the shape of the lateral con-
dyle of the femur and by the medial pull of the vastus medialis.
Excision of the patella results in minimal functional deficiency.
The patella ossifies from several centers, which appear during
childhood.
• The tarsal bones (14) are seven pairs of bones (talus, calcaneus,
navicular, cuboid, and the first, second, and third cuneiform
bones). Only the talus articulates with the tibia and fibula. The
tarsus is convex superiorly and concave inferiorly. The tarsal
bones are the talus, navicular, and three cuneiforms on the
medial side, and the calcaneus and cuboid, which are more
laterally placed. Accessory ossicles may be found—for exam-
ple, a fibular sesamoid, the os tibiale externum (near the tuber-
osity of the navicular and sometimes called the “accessory
navicular”), and the os trigonum.
• The metatarsal bones (10) support the sole of the foot and are num-
bered I to V from medial to lateral, with the distal ends forming
the ball of the foot. They are connected to the phalanges by five
metatarsal bones, referred to collectively as the metatarsus. Each
metatarsal is technically a long bone, consisting of a base proxi-
mally, a shaft, and a head distally. Each bone has characteristic
features; for example, the first (which carries more weight) is
short and thick. The base of the fifth presents a tuberosity, which
projects posterolaterally and is palpable at the lateral aspect of
the foot.
• The phalanges (28) have the same arrangement as with the
fingers and thumb, but with the toes and great toe (hallux). They
are designated proximal, middle, and distal. Each phalanx is
technically a long bone, consisting of a base proximally, a shaft,
and a head distally. Although the phalanges of the foot are
shaped differently from those of the hand, their basic arrange-
ment is similar, in that each distal phalanx ends distally in a
tuberosity. The middle and distal phalanges of the little toe are
often fused. The phalanges usually begin to ossify during fetal
life, and centers appear postnatally in the bases of most of them.