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spring the fibres of origin of the abductor digiti quinti muscle. On the anterior part of the plantar surface there is an elevated elongated tubercle, which terminates somewhat abruptly just behind the anterior border of this aspect of the bone, giving rise at times to a notch. From the tubercle spring the fibres of the long plantar ligament, whilst the notch serves for the attachment of the deeper fibres of the plantar calcaneo-cuboid ligament. The two heads of origin of the quadratus plantæ muscle arise from the bone on either side of the long plantar ligament.
The medial surface of the calcaneus is crossed obliquely, from above downwards and forwards, by a broad groove of considerable depth; along this pass many of the structures which enter the sole of the foot from the back of the leg. The groove is overhung in front and above by a projecting bracketlike process, called the sustentaculum tali. The plantar surface of the sustentaculum is channelled by a groove in which is lodged the tendon of the flexor hallucis longus muscle; whilst its medial border, to which is attached a part of the deltoid ligament (tibio-calcanean fibres) of the ankle, is overlain by the tendon of the flexor digitorum longus. To the anterior border of the sustentaculum is attached the plantar calcaneo-navicular ligament, and placed on its dorsal surface is the articular facet already referred to (facies articularis media). Posteriorly the medial surface of the bone is limited inferiorly by the projection of the medial process of the tuber calcanei, and above by the medial lipped edge of the tuberosity.
FACETS FOR TALUS
FACETS FOR TALUS
LATERAL PROCESS MEDIAL PROCESS
FIG. 260.-THE RIGHT CALCANEUS. C. Seen from the lateral side; D. Seen from the medial side.
The lateral surface, broad behind and narrower in front, is of flattened form. Springing from it, just below the lateral end of the sinus tarsi, is the trochlear process, often indistinctly marked. To this the fibres of the inferior retinaculum of the peroneal tendons are attached; whilst in grooves, above and below it, pass the
tendons of the peronæus brevis and longus muscles respectively. To the upper and posterior part of this surface are attached the fibres of the calcaneo-fibular ligament of the ankle.
The anterior extremity is furnished with a saddle-shaped surface on its anterior aspect for articulation with the cuboid. This facet is concave from above downwards, and slightly convex from side to side; its edges are sharply defined, except medially, and serve for the attachment of ligaments.
The posterior extremity, called the tuber calcanei (tuberosity), forms the projection of the heel. Of oval form and rounded surface, it rests upon the two processes or tubercles inferiorly and is divisible into three areas. Of these the highest is smooth and crescentic, and is covered by a bursa; the intermediate is also fairly smooth, and is defined inferiorly by an irregular line, sometimes a definite ridge,
the edges of which are striated. Into this surface the tendo calcaneus is inserted. The lowest surface is rough and striated, and is confluent below with the medial and lateral processes; this is overlain by the dense layer of tissue which forms the pad of the heel.
Os Naviculare Pedis.
The navicular bone (O.T. scaphoid), of compressed piriform shape, is placed on the medial side of the foot, between the head of the talus posteriorly and the three cuneiform bones anteriorly. The bone derives its name from the oval or boat-shaped hollow on its posterior surface, which rests upon the head of the talus. Its anterior aspect is furnished with a semilunar articular area, which is subdivided by two faint ridges into three wedge-shaped facets for articulation, medio-laterally, with the first, second, and third cuneiform bones. The dorsal surface of the bone, convex from side to side, is rough for the attachment of the ligaments on the dorsal aspect of the foot. On its plantar aspect the bone is irregularly concave; projecting downwards and backwards from its lateral side there is often a prominent spur of bone, the plantar process, to which is attached the plantar calcaneo-navicular ligament. The lateral surface is narrow from before backwards, and rounded from above downwards. In 70 per cent. of cases (Manners Smith) it is provided with a facet which rests upon a corresponding area on the cuboid. Behind this, in rare instances, there is a facet for the calcaneus. The medial surface of the bone projects beyond the general line of the medial border of the foot, so as to form a thick rounded tuberosity (tuberositas ossis navicularis), the position of which can be easily determined in the living. To the medial and plantar surface of this process an extensive portion of the tendon of the tibialis posterior muscle is inserted.
FOR HEAD OF
OCCASIONAL FACET FOR CUBOID
FOR SECOND CUNEIFORM
FOR FIRST CUNEIFORM
The Cuneiform Bones.
The cuneiform bones, three in number, are placed between the navicular posteriorly and the bases of the first, second, and third metatarsal bones anteriorly, for which reason they are now named the first, second, and third cuneiforms (O.T. internal, middle, and external). More or less wedge-shaped, as their name implies, the first is the largest, whilst the second is the smallest of the group. Combined, they form a compact mass, the posterior surface of which, fairly regular in outline, rests on the anterior surface of the navicular; whilst anteriorly they form a base of support for the medial three metatarsals, the outline of which is irregular, owing to the base of the second metatarsal bone being recessed between the first and third cuneiforms, as it articulates with the anterior surface of the shorter second cuneiform.
The first cuneiform bone, the largest of the three, lies on the medial border of the foot between the base of the metatarsal bone of the great toe anteriorly, and the medial part of the anterior surface of the navicular posteriorly. In form the bone is less characteristically wedge-shaped than its fellows of the same name and differs from them in this respect, that whilst the second and third cuneiforms are so disposed that the bases of their wedges are directed upwards towards the dorsum of the foot, the first cuneiform is so placed that its base is
directed towards the plantar aspect; further, the vertical diameter of the bone is not the same throughout, but is much increased at its anterior or metatarsal end. The
dorsal and medial surfaces are confluent, and I. METATARSAL form a convexity from above downwards, which is most pronounced inferiorly, where it is turned round the plantar side of the foot to become continuous with the plantar or inferior aspect, which is rough and irregular. On the anterior part of the medial aspect of the bone there is usually a distinct oval impression, which indicates the surface of insertion of a portion of the tendon of the tibialis anterior muscle. Elsewhere this surface is rough for ligamentous attachments. The lateral surface of the bone, quadrilateral in shape, is directed towards the second cunei
FIG. 262.-ANTERIOR SURFACES OF THE
THREE CUNEIFORM BONES OF THE form; but as it exceeds it in length, it also comes in contact with the medial side of the base of the second metatarsal bone. Running along the posterior and dorsal edges of this area is an -shaped articular surface, the anterior and dorsal part of which is for the base of the second metatarsal bone, the remainder articulating with the medial side of the second cuneiform. The non-articular part of this aspect of the bone is rough for the attachment of the strong interosseous ligaments
which bind it to IMPRESSION
II. FIRST METATARSAL CUNEIFORM
FIG. 263.-THE RIGHT FIRST
the second cuneiform and second metatarsal bones. The posterior surface of the bone is provided with a piriform facet which fits on the most medial articular area of the navicular. Here the wedge-shaped form of the bone is best displayed. Anteriorly the vertical diameter of the bone is much increased, and the facet for the
base of the metatarsal bone of the great toe is consequently much larger than that for the navicular. This metatarsal facet is usually of semilunar form, but not infrequently is more reniform in shape, and may in some cases display complete separation into two oval portions.
The second cuneiform is of a typical wedge shape, the base of the wedge being II. METATARSAL directed towards the dorsum of the foot; FIG. 266. THE RIGHT shorter than the others, it lies between
FIG. 265.-THE RIGHT SECOND CUNEIFORM SECOND CUNEIFORM them, articulating with the base of the (Medial Side). (Lateral Side). second metatarsal in front, and the middle facet on the anterior surface of the navicular behind. Its dorsal surface, which corresponds to the base of the wedge, conforms to the roundness of the instep, and is slightly convex from side to side, affording attachments for the dorsal ligaments. Its plantar aspect is narrow and rough, forming the edge of the wedge; with this the plantar ligaments are connected. The medial surface, quadrilateral in outline, is furnished with an -shaped articular area along its posterior and dorsal borders in correspondence with the similar area on the lateral. side of the first cuneiform. The rest of this aspect is rough for ligaments.
FIG. 264. THE RIGHT FIRST
The lateral surface displays a facet arranged along its posterior border, and usually somewhat constricted in the middle; this is for the third cuneiform. In front of this the bone is rough for the interosseous ligaments which bind the two bones. together. The posterior surface is provided with a triangular facet slightly concave from above downwards; this rests on the intermediate articular surface on the anterior aspect of the navicular. In front the bone articulates by means of a wedge-shaped facet with the base of the metatarsal bone of the second toe.
CUBOID IV. METATARSAL
The third cuneiform, intermediate in size between the first and second, is also of a fairly typical wedge shape; though its anteroposterior axis is not straight but bent, so that the anterior end of the bone turns slightly medially. Its dorsal surface, which corresponds to the base of the wedge, is slightly convex from side to side, and provides attachments for the dorsal ligaments. Its inferior or plantar aspect forms a rough blunt edge, and serves for the attachment of the plantar ligaments. Its medial surface, of quadrilateral form, displays two narrow articular strips, placed along its anterior and posterior borders respectively, each somewhat constricted in the middle. The anterior facet articulates with the lateral surface of the base of the second metatarsal bone, the posterior with the lateral surface of the second cuneiform. The rough non-articular surface, which separates the two elongated facets, serves for the attachment of ligaments. The lateral aspect of the bone is characterised by a large circular or oval facet, placed near its posterior border, for articulation with the cuboid; in front of this the anterior border is lipped above by a small semi-oval facet for articulation with the medial side of the base of the fourth metatarsal. The rest of the bone around and between these facets is rough for ligaments. Posteriorly the bone is furnished with a blunt, wedge-shaped facet for articulation with the corresponding area on the anterior surface of the navicular. Below this the surface is narrow and rough for the attachment of ligaments. The anterior surface of the bone articulates with the base of the third metatarsal by an area of triangular shape
FIG. 268.-RIGHT THIRD
The cuboid lies on the lateral side of the foot, about its middle, articulating with the calcaneus posteriorly and the fourth and fifth metatarsal bones anteriorly. Its dorsal surface, plane in an antero-posterior direction, is slightly rounded from side to side, and provides attachment for ligaments. Its plantar aspect is traversed obliquely from the lateral side medially and forwards by a thick and prominent ridge, the lateral extremity of which, at the point where it is confluent with the lateral surface, forms a prominent tubercle (tuberositas ossis cuboidei), the anterior and lateral surface of which is smooth and facetted to allow of the play of a sesamoid bone which is frequently developed in the tendon of the peronæus longus muscle. Anterior to this ridge there is a groove (sulcus peronæi) in which the tendon of the peronæus longus muscle is lodged as it passes across the plantar surface of the bone. Behind the ridge the bone is rough, and serves for the attachment of the plantar calcaneo-cuboid ligament, the superficial fibres of which pass forwards and are attached to the summit of the ridge. The lateral aspect of the bone is short and rounded, and is formed by the confluence of the dorsal and plantar surfaces: it is more or less notched by the peroneal groove which turns round its plantar edge. The medial surface of the bone is the most extensive; it is easily recognisable on account of the presence of a rounded or oval facet situated near
its middle and close to its dorsal border. This is for articulation with the lateral side of the third cuneiform; anterior and posterior to this the surface is rough for ligaments. Not infrequently, behind the facet for the third cuneiform, there is
TUBEROSITY GROOVE FOR PERONEUS
a small articular surface for for the navicular, as is the case normally in the gorilla, whilst posteriorly and on the plantar aspect the projecting inferior angle is sometimes provided with a facet on which the head of the talus rests. (Sutton, "Proc. Anat. Soc.," Journ. Anat. and Physiol. vol. xxvi. p. 18.) The anterior surface is oval or conical in outline; sloping obliquely from the medial side laterally and backwards, it is divided about its middle by a slight vertical ridge into two parts, the medial of which articulates with the base of the fourth metatarsal bone, the lateral with that of the fifth. The posterior surface, also articular, has a semilunar outline, the convex margin of which corresponds to the dorsal roundness of the bone. The inferior lateral angle corresponds to the tubercle on the lateral border of the bone, whilst the inferior medial angle forms a pointed projection which is sometimes called the calcanean process. This surface articulates with the calcaneus by means of a saddle-shaped facet, which is convex from side to side, and concave from dorsal to plantar margins.
FIG. 269.-THE RIGHT CUBOID BONE.
B. Medial Side.
The tarsus as a whole may be conveniently described as arranged in two
1. About fifth month.
No ossification in the tarsus visible.
3. About seventh month. Nucleus for calcaneus well developed.
4 and 5. About eighth month. Centre for talus, as well as for calcaneus, is now seen.
6. About birth. Centres for the talus and calcaneus are well developed; there is also a considerable centre for the cuboid, and the appearance of a centre for the third cuneiform is now displayed.
columns; the medial, corresponding to the medial border of the foot, comprising the talus, navicular, and three cuneiforms, and forming a base for the support of the medial three metatarsal bones and their phalanges. The lateral column, formed by the calcaneus and cuboid, supports the fourth and fifth metatarsal bones, together with their phalanges. The dorsal surface of the anterior portion of the