THE FOOT
THE SCAPHOID
The Scaphoid or Navicular bone, so called from its fancied resemblance to a boat, is situated at the inner side of the tarsus, between the astragalus behind and the three cuneiform bones in front. This bone may be distinguished by its boat-like form, being concave behind, convex, and subdivided into three facets in front.
The anterior surface, of an oblong from, is convex from side to side, and subdivided by two ridges into three facets, for articulation with the three cuneiform bones. The posterior surface is oval, concave, broader externally than internally, and articulates with the rounded head of the astragalus. The superior surface is convex from side to side, and rough for the attachment of ligaments. The inferior, somewhat concave, irregular, and also rough for the attachment of ligaments. The internal surface presents a rounded tubercular eminence, the tuberosity of the scaphoid, which gives attachment to part of the tendon of the Tibialis posticus. The external surface is broad, rough, and irregular, for the attachment of ligamentous fibres, and occasionally presents a small facet for articulation with the cuboid bone.
To ascertain to which foot it belongs, hold the bone with the concave articular surface backwards, and the broad dorsal surface upwards; the broad external surface will point to the side to which the bone belongs.
Articulations. With four bones; astragalus and three cuneiform; occasionally also with the cuboid.
Attachment of Muscles. Part of the Tibialis posticus.
The Cuneiform Bones have received their name from their wedge-like form. They form.the most anterior row of the inner division of the tarsus, being placed between the scaphoid behind, the three innermost metatarsal bones in front, and the cuboid externally. They are called the first, second, and third, counting from the inner to the outer side of the foot, and from their position, internal, middle, and external.
THE INTERNAL CUNEIFORM
The Internal Cuneiform is the largest of the three. It is situated at the inner side of the foot, between the scaphoid behind and the base of the first metatarsal in front. It may be distinguished by its large size, as compared with the other two, and from its more irregular wedge-like form. It presents for examination six surfaces.
The internal surface is subcutaneous, and forms part of the inner border of the foot; it is broad, quadrilateral, and presents at its anterior inferior angle a smooth oval facet, over which the tendon of the Tibialis anticus muscle glides; rough in the rest of its extent, for the attachment of ligaments. The external surface is concave, presenting, along its superior and posterior borders, a narrow surface for articulation with the middle cuneiform behind, and second metatarsal bone in front; in the rest of its extent, it is rough for the attachment of ligaments, and prominent below, where it forms part of the tuberosity. The anterior surface, reniform in shape, articulates with the metatarsal bone of the great toe. The posterior surface is triangular, concave, and articulates with the innermost and largest of the three facets on the anterior surface of the scaphoid. The inferior or plantar surface is rough, and presents a prominent tuberosity at its back part for the attachment of part of the tendon of the Tibialis posticus. It also gives attachment in front of this to part of the tendon of the Tibialis anticus. The superior surface is the narrow pointed end of the wedge, which is directed upwards and outwards; it is rough for the attachment of ligaments.
To ascertain to which side it belongs, hold the bone so that its superior narrow edge looks upwards, and the long articular surface forwards; the external surface marked by its vertical and horizontal articular facets will point to the side to which it belongs.
Articulations. With four bones; scaphoid, middle cuneiform, and first and second metatarsul bones.
Attachment of Muscles. The Tibialis anticus and posticus.
THE MIDDLE CUNEIFORM
The Middle Cuneiform, the smallest of the three, is of very regular wedge-like form; the broad extremity being placed upwards, the narrow end downwards. It is situated between the other two bones of the same name, and corresponds to the scaphoid behind, and the second metatarsal in front.
The anterior surface, triangular in form, and narrower than the posterior, articulates with the base of the second metatarsal bone. The posterior surface, also triangular, articulates with the scaphoid. The internal surface presents an articular facet, running along the superior and posterior borders, for articulation with the internal cuneiform, and is rough below for the attachment of ligaments. The external surface presents posteriorly a smooth facet for articulation with the external cuneiform bone. The superior surface forms the base of the wedge; it is quadrilateral, broader behind than in front, and rough for the attachment of ligaments. The inferior surface, pointed and tubercular, is also rough for liga-mentous attachment.
To ascertain to which foot the bone belongs, hold its superior or dorsal surface upwards, the broadest edge being towards the holder, and the smooth facet (limited to the posterior border) will point to the side to which it belongs.
Articulations. With four bones; scaphoid, internal and external cuneiform, and second metatarsal bone.
THE EXTERNAL CUNEIFORM
The External Cuneiform, intermediate in size between the two preceding, is of a very regular wedge-like form, the broad extremity being placed upwards, the narrow end downwards. It occupies the centre of the front row of the tarsus between the middle cuneiform internally, the cuboid externally, the scaphoid behind, and the third metatarsal in front. It has six surfaces for examination.
The anterior surface triangular in form, articulates with the third metatarsal bone. The posterior surface articulates with the most external facet of the scaphoid, and is rough below for the attachment of ligamentous fibres. The internal surface presents two articular facets separated by a rough depression; the anterior one, situated at the superior angle of the bone, articulates with the outer side of the base of the second metatarsal bone; the posterior one skirts the posterior border, and articulates with the middle cuneiform; the rough depression between the two gives attachment to an interosseous ligament. The external surface also presents two articular facets, separated by a rough non-articular surface; the anterior facet, situated at the superior corner of the bone, is small, and articulates with the inner side of the base of the fourth metatarsal; the posterior, and larger one, articulates with the cuboid; the rough non-articular surface serves for the attachment of an interosseous ligament. The three facets for articulation with the three metatarsal bones are continuous with one another, and covered by a prolongation of the same cartilage; the facets for articulation with the middle cuneiform and scaphoid are also continuous, but that for articulation with the cuboid is usually separate and independent. The superior or dorsal surface, of an oblong form, is rough for the attachment of ligaments. The inferior or plantar surface is an obtuse rounded margin, and serves for the attachment of part of the tendon of the Tibialis posticus, some of the fibres of origin of the Flexor brevis pollicis, and ligaments.
To ascertain to which side it belongs, hold the bone with the broad dorsal surface upwards, the prolonged edge backwards; the separate articular facet for the cuboid will point to the proper side.
Articulations. With six bones: the scaphoid, middle cuneiform, cuboid, and second, third, and fourth metatarsal bones.
Attachment of Muscles. Part of Tibialis posticus, and Flexor brevis pollicis.
THE METATARSAL BONES
The Metatarsal bones are five in number; they are long bones, and subdivided into a shaft, and two extremities.
The Shaft is prismoid in form, tapers gradually from the tarsal to the phalan-geal extremity, and is slightly curved longitudinally, so as to be concave below, slightly convex above.
The Posterior Extremity, or Base, is wedge-shaped, articulating by its terminal surface with the tarsal bones, and by its lateral surfaces with the contiguous bones; its dorsal and plantar surfaces being rough, for the attachment of ligaments.
The Anterior Extremity, or Head, presents a terminal rounded articular surface, oblong from above downwards, and extending further backwards below than above. Its sides are flattened, and present a depression, surmounted by a tubercle, for ligamentous attachment. Its under surface is grooved in the middle line, for the passage of the Flexor tendon, and marked on each side by an articular eminence continuous with the terminal articular surface.
PECULIAR METATARSAL BONES
The First is remarkable for its great size, but is the shortest of all the metatarsal bones. The shaft is strong, and of well-marked prismoid form. The posterior extremity presents no lateral articular facets; its terminal articular surface is of large size, of semi-lunar form, and its circumference grooved for the tarso-metatarsal ligaments; its inferior angle presents a rough oval prominence, for the insertion of the tendon of the Peroneus longus. The head is of large size; on its plantar surface are two grooved facets, over which glide sesamoid bones, separated by a smooth elevated ridge.
The Second is the longest and largest of the remaining metatarsal bones; its posterior extremity being prolonged backwards, into the recess formed between the three cuneiform bones. Its tarsal extremity is broad above, narrow and rough below. It presents four articular surfaces: one behind, of .a triangular form, for articulation with the middle cuneiform; one at the upper part of its internal lateral surface, for articulation with the internal cuneiform; and two on its external lateral surface, a superior and an inferior, separated by a rough depression. Each articular surface is divided by a vertical ridge into two parts; the anterior segment of each facet articulates with the third metatarsal; the two posterior (sometimes continuous) with the external cuneiform.
The Third articulates behind, by means of a triangular smooth surface, with the external cuneiform; on its inner side, by two facets, with the second metatarsal; and on its outer side, by a single facet, with the third metatarsal. This facet is of circular form, and situated at the upper angle of the base.
The Fourth is smaller in size than the preceding; its tar sal extremity presents a terminal quadrilateral surface, for articulation with the cuboid; a smooth facet on the inner side, divided by a ridge into an anterior portion for articulation with the third metatarsal, and a posterior portion for articulation with the external cuneiform; on the outer side a single facet, for articulation with the fifth metatarsal.
The Fifth is recognised by the tubercular eminence on the outer side of its base; it articulates behind, by a triangular surface cut obliquely from without inwards, with the cuboid, and internally with the fourth metatarsal.
Articulations. Each bone articulates with the tarsal bones by one extremity, and by the other with the first row of phalanges. The number of tarsal bones with which each metatarsal articulates, is one for the first, three for the second, one for the third, two for the fourth, and one for the fifth.
Attachment of Muscles. To the first metatarsal bone, three: part of the Tibialis anticus, Peroneus longus, and First dorsal interosseous. To the second, three: the Adductor pollicis, and First and Second dorsal interosseous. To the third, four: the Adductor pollicis, Second and Third dorsal interosseous, and First plantar. To the fourth, four: the Adductor pollicis, Third and Fourth dorsal, and Second plantar interosseous. To the fifth, five: the Peroneus brevis, Peroneus tertius, Flexor brevis minimi digiti, Fourth dorsal, and Third plantar interosseous.
PHALANGES
The Phalanges of the foot, both in number and general arrangement, resemble those in the hand; there being two in the great toe, and three in each of the other toes.
The phalanges of the first row resemble closely those of the hand. The shaft is compressed from side to side, convex above, concave below. The posterior extremity is concave; and the anterior extremity presents a trochlear-articular surface, for articulation with the second phalanges.
The phalanges of the second row are remarkably small and short, but rather broader than those of the first row.
The ungual phalanges in form resemble those of the fingers; but they are smaller, flattened from above downwards, presenting a broad base for articulation with the second row, and an expanded extremity for the support of the nail and end of the toe.
Articulations. The first row with the metatarsal bones, and second phalanges; the second of the great toe with the first phalanx, and of the other toes with the first and third phalanges; the third with the second row.
Attachment of Muscles. To the first phalanges, great toe: innermost tendon of Extensor brevis digitorum, Abductor pollicis, Adductor pollicis, Flexor brevis pollicis, Transversus pedis. Second toe: First and Second dorsal interosseae. Third toe: Third dorsal and First plantar interosseae. Fourth toe: Fourth dorsal and Second plantar interosseas. Fifth toe: Flexor brevis minimi digiti, Abductor minimi digiti, and Third plantar interosseous.— Second phalanges, great toe: Extensor longus pollicis, Flexor longus pollicis. Other toes: Flexor brevis digitorum, one slip from the Extensor brevis digitorum and Extensor longus digitorum. — Third phalanges: two slips from the common tendon of the Extensor longus and Extensor brevis digitorum, and the Flexor longus digitorum.
DEVELOPMENT OF THE FOOT
The Tarsal bones are each developed by a single centre, excepting the os calcis, which has an epiphysis for its posterior extremity. The centres make their appearance in the following order: in the os calcis, at the sixth month of foetal life; in the astragalus, about the seventh month; in the cuboid, at the ninth month; external cuneiform, during the first year; internal cuneiform, in the third year; middle cuneiform, in the fourth year. The epiphysis for the posterior
tuberosity of the os calcis appears at the tenth year, and unites with the rest of the bone soon after puberty.
The Metatarsal bones are each developed by two centres: one for the shaft, and one for the digital extremity in the four outer metatarsal; one for the shaft, and one for the base in the metatarsal bone of the great toe. Ossification commences in the centre of the shaft about the seventh week, and extends towards either extremity, and in the digital epiphyses about the third year; they become joined between the eighteenth and twentieth years.
The Phalanges are developed by two centres for each bone: one for the shaft, and one for the metatarsal extremity.
SESAMOID BONES
These are small rounded masses, cartilaginous in early life, osseous in the adult, which are developed in those tendons which exert a certain amount of pressure upon the parts over which they glide. It is said that they are more commonly found in the male than in the female, and in persons of an active muscular habit than in those that are weak and debilitated. They are invested throughout their whole surface by the fibrous tissue of the tendon in which they are found, excepting upon that side which lies in contact with the part over which they play, where they present a free articular facet. They may be divided intotwo kinds: those which glide over the articular surfaces of joints; those which play over the cartilaginous facets found on the surfaces of certain bones.
The sesamoid bones of the joints are, in the lower extremity, the patella (already described), which is developed in the tendon of the Quadriceps extensor. Two small sesamoid bones are found opposite the metatarso-phalangeal joint of the great toe in each foot, in the tendons of the Flexor brevis pollicis, and occasionally one in the metatarso-phalangeal joints of the second toe, the little toe, and, still more rarely, in the third and fourth toes.
Sesamoid Bones
In the upper extremity, there are two on the palmar surface, opposite the meta-carpo-phalangeal joint in the thumb, developed in the tendons of the Flexor brevis pollicis. Occasionally one or two opposite the metacarpo-phalangeal articulations of the fore and little fingers, and, still more rarely, one opposite the same joints of the third and fourth fingers.
Those found in tendons which glide over certain bones occupy the following situations. One in the tendon of the Peroneus longus, where it glides through the groove in the cuboid bone. One appears late in life in the tendon of the Tibialis anticus, opposite the smooth facet on the internal cuneiform bone. One in the tendon of the Tibialis posticus, opposite the inner side of the astragalus. One in the outer head of the Gastrocnemius, behind the outer condyle of the femur; and one in the Psoas and Iliacus, where they glide over the body of the pubes. Occasionally in the tendon of the Biceps, opposite the tuberosity of the radius; in the tendon of the Gluteua maximus, as it passes over the great trochanter; and in the tendons which wind around the inner and outer malleoli. PREVIOUS PAGE
