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a deeper plane than, the calcaneo-fibular ligament of the ankle-joint. It consists of short fibres passing between the adjacent rough lateral margins of the two bones.

The ligamentum talocalcaneum posterius (Fig. 324) closes the joint-cavity on its posterior aspect. It consists of fibres which radiate from the posterior aspect of the posterior process of the talus to the superior surface of the calcaneus, immediately behind the articular facet.

The ligamentum talocalcaneum mediale lies obliquely on the medial side of the joint, and consists of fibres which extend from the medial posterior tubercle of the talus to the posterior roughened border of the sustentaculum tali. Some of its fibres become continuous with the plantar calcaneo-navicular ligament.

The ligamentum talocalcaneum interosseum (Fig. 325) closes the antero-medial aspect of the joint. It is the strongest of the series of ligaments entering into the capsule. Compared with it the other bands are, comparatively speaking, insignificant. Its attachments are to the bottom of each

Articular surface on groove, so that it occupies

navicular for head of the tarsal canal formed by Navicular bone these opposing grooves.

Calcaneo-navicular part

) of bifurcate ligament A synovial stratum lines the fibrous stratum, and it is distinct from other tarsal synovial membranes. Plantar cal

Interosseous talo. caneo-navicular Articulatio Talocal- ligament

calcaneal

ligament caneonavicularis. This Tendon of tibialis

Articular surface is one of the most import

posterior muscle
(cut)

body of talus ant of the joints of the foot, not only because the Sustentaculum tali; articular

surface for talus talus is here situated in relation to the summit of the antero- posterior arch of the foot, but because the head of the talus is received into a composite socket made up of the sustentaculum tali, the navicular, and the plantar calcaneonavicular ligament.

FIG. 325.—THE COMPOSITE ARTICULAR SOCKET FOR THE HEAD OF The articular surface on the head of the talus presents anteriorly a convex rounded facet for articulation with the navicular, inferiorly a convex facet which rests upon the sustentaculum tali, and intermediate between these two there is a triangular facet which articulates with the plantar calcaneo - navicular ligament. All these facets are in continuity with each other, and are in front of the tarsal groove on the inferior surface of the talus. Occasionally a fourth narrow facet is found along the lateral and posterior part of the articular surface of the head of the talus, whereby it articulates with the calcaneo-navicular part of the bifurcate ligament.

The navicular bone presents a shallow, cup-shaped, articular cavity towards the head of the talus.

The articular surface of the sustentaculum tali is concave, and is usually marked off into two facets.

Two ligaments play an important part in binding together the calcaneus and the navicular, although these bones do not directly articulate; and further, these ligaments provide additional articular surfaces for the head of the talus. These are the two following :

(a) The ligamentum calcaneonaviculare plantare (Figs. 325 and 326) is an extremely powerful fibro-cartilaginous band. It extends between the anterior margin of the sustentaculum tali and the plantar surface of the navicular. Certain of its upper fibres radiate upwards on the medial surface of the navicular, and

[graphic]

THE Talus.

become continuous with the tibio-navicular portion of the deltoid ligament of the ankle-joint. The plantar aspect of this ligament is in contact with the tendon of the tibialis posterior muscle, through which the head of the talus receives great support. Superiorly it contributes an articular surface which forms a triangular portion of the floor of the composite socket in which the head of the talus is received.

(6) The calcaneo-navicular part of the bifurcate ligament (Fig. 325) lies deeply in the front part of the sinus tarsi, i.e. the interval between the talus and calcaneus. Its fibres are short, and extend from the dorsal surface of the front part of the

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Fig. 326. – PLANTAR ASPECT OF TARSAL AND TARSO-METATARSAL JOINTS.

calcaneus, immediately to the lateral side of the sustentacular facet, forwards to the lateral side of the navicular bone. Frequently the ligament presents a surface which articulates with the head of the talus, and in these cases it forms a part of the composite socket.

The cavity of the talo-calcaneo-navicular joint is closed posteriorly by the interosseous talo-calcaneal ligament already described. On its medial and lateral inferior aspects it is closed by the calcaneo-navicular ligaments.

The superior and lateral aspects are covered by the ligamentum talonaviculare dorsale. This ligament is thin, and extends from the proximal non-articular area on the head of the talus to the dorsal surface of the navicular bone. It may be subdivided into dorsal, lateral, and medial talo-navicular bands (Fig. 324), which, with the calcaneo-navicular and interosseous talo-calcaneal ligaments, complete the capsular investment of the joint.

A distinct synovial stratum lines all parts of the capsule of the joint.

Articulatio Calcaneocuboidea.—This is situated between the anterior concavo-convex surface of the calcaneus and the posterior similar surface of the cuboid.

The ligaments which invest this joint constitute a calcaneo-cuboid capsule, whose parts are arranged in relation to the four non-articular sides of the cuboid bone, and are especially strong upon the plantar aspect, in relation to their great importance in resisting strains.

The medial calcaneo-cuboid ligament occupies part of the interval between the talus and calcaneus—the sinus tarsi. It is the calcaneo-cuboid part of the lig. bifurcatum, and is a V-shaped structure, of which the single end is attached to the calcaneus, and the double ends separate to reach contiguous areas on the navicular and cuboid respectively.

The dorsal calcaneo-cuboid ligament (Fig. 324) is a broad portion of the fibrous stratum of the capsule extending from the dorsal and lateral surfaces of the calcaneus to the dorsal surface of cuboid.

The lateral calcaneo-cuboid ligament is another but narrower part of the capsule which extends from the lateral aspect of the calcaneus to the lateral side of the cuboid, immediately behind the facet on the tuberosity.

The inferior calcaneo-cuboid ligament consists of two parts--a superficial and a deep. The superficial series of fibres, the long plantar ligament (Fig. 326), is attached to the plantar surface of the calcaneus in front of the processes of the tuber calcanei. It forms a long powerful structure which runs forwards to be fixed to the plantar surface of the cuboid ridge, but many of its fibres pass superficial to the tendon of the peronæus longus, and extend to the bases of the third, fourth, and fifth metatarsal bones.

The deep series of fibres, the plantar calcaneo-cuboid ligament (O.T. short plantar ligament) (Fig. 326), is distinctly separated from the long plantar ligament by a layer of areolar tissue. It forms a broad but short band of great strength, which is attached to the plantar surface of the distal end of the calcaneus, and extends to the plantar surface of the cuboid just behind the ridge. Both of these ligaments are of great importance in maintaining the longitudinal arch of the foot, and in this respect are only second to the plantar calcaneo-navicular ligament.

A synovial stratum lines the capsule.

Articulatio Tarsi Transversa (Choparti).—This is a term sometimes applied to the talo-navicular and calcaneo-cuboid joints. These articulations do not communicate with each other; and although there is an occasional direct articulation between the navicular and cuboid, it does not constitute an extension of the transverse tarsal joint, but is a prolongation from the series of cuneo-navicular and cuneo-cuboid articulations.

Nevertheless there is always a set of ligaments which bind the navicular and cuboid bones together, and these may be regarded as accessory to the various transverse tarsal joints.

The dorsal cuboideo - navicular ligament (Fig. 324) consists of short oblique fibres which attach the contiguous dorsal surfaces of the cuboid and navicular bones.

The plantar cuboideo - navicular ligament is transverse in direction, and extends between adjacent plantar areas of the cuboid and navicular bones.

The interosseous cuboideo - navicular ligament intervenes between contiguous surfaces of the same bones. When there is an extension of the cuneo-navicular joint backwards between the navicular and cuboid, it is situated in front of the lastInentioned ligament, and is called the articulatio cuboideonavicularis. Around this joint the preceding ligaments are grouped. Since, however, the joint is inconstant while the ligaments are always present, it is preferable to consider them as above indicated.

Articulatio Cuneonavicularis. - The cuneo - navicular articulation joint is situated between the navicular and the three cuneiform bones. The anterior surface of the navicular presents a facet for each of the cuneiform bones, but its articular surface is not interrupted. These facets form a somewhat convex anterior surface which fits into the shallow articular concavity presented by the proximal ends of the three cuneiform bones. This joint may be extended by the occasional cuboideo-navicular articulation already referred to.

The fibrous stratum of the articular capsule is composed of short strong bands which are distinctly visible on all sides except towards the cuboid bone, where the joint may communicate with the cuneo-cuboid and cuboideo-navicular joints. Anteriorly the joint communicates with the intercuneiform articulations. The dorsal parts of the capsule are short longitudinal bands termed dorsal cuneo-navicular ligaments (Figs. 323 and 324). These extend without interruption to the medial aspect of the joint. Inferiorly there are similar bands, known as plantar cuneo - navicular ligaments, also longitudinal in direction, but intimately associated with offsets from the tendon of the tibialis posterior muscle.

The synovial stratum which lines the fibrous stratum sends prolongations forwards on each side of the second cuneiform bone, and in addition it often communicates with the cuneo-cuboid joint cavity, and it always communicates with the cuboideo-navicular cavity when that joint exists.

Articulationes Intercuneiformeæ. These ar two in number, and exist between adjacent contiguous surfaces of the three cuneiform bones. These surfaces are partly articular and partly non-articular. The small size of the second cuneiform bone allows the first cuneiform as well as the third cuneiform to project forwards beyond it, one on each side, and therefore the articular surfaces turned towards the second cuneiform are not entirely occupied by that bone. They form a recess facing the metatarsus, into which the base of the second metatarsal bone is thrust.

Ligamenta intercuneiformea dorsalia constitute fairly strong transverse bands which extend between adjacent dorsal surfaces and invest the joint cavities in this direction.

The ligamenta intercuneiformea plantaria are two strong bands which pass from the rough non-articular areas on opposite sides of the second cuneiform to the opposing surfaces of the first and third cuneiform bones. These ligaments shut in the joint cavities inferiorly, and also anteriorly in the case of the lateral of the two joints.

The ligamenta intercuneiformea interossea are bonds which bind together adjacent cuneiform bones.

The synovial stratum is an extension of that which lines the cuneo-navicular joint; but while it is restricted to the lateral of the two joints, in the case of the medial one it is prolonged still farther forward to the tarso-metatarsal series of joints.

Articulatio Cuneocuboidea.—This occurs between the rounded or oval facets on the opposing surfaces of the cuboid and third cuneiform.

The ligamentum cuneocuboideum dorsale is a flat, somewhat transverse band which closes the joint on its dorsal aspect, and extends between the dorsal surfaces of the two bones.

The ligamentum cuneocuboideum plantare is difficult to determine. It is situated deep to the long plantar ligament, and extends between adjacent rough surfaces of the two bones.

The ligamentum cuneocuboideum interosseum is the strongest. It closes the joint cavity anteriorly, and is attached to the contiguous non-articular surfaces of the two bones.

The synovial stratum is frequently distinct, but at other times the joint cavity communicates with those of the cuneo-navicular and cuboideo-navicular articulations.

Synovial Strata of the Intertarsal Joints.--Four and sometimes five distinct and separate synovial strata may thus be enumerated in connexion with the tarsal articulations, viz. : (1) talo-calcaneal; (2) talo-calcaneo-navicular; (3) calcaneo-cuboid ; (4) cuneo-navicular and its extensions ; (5) occasionally cuneocuboid.

ARTICULATIONES TARSOMETATARSEÆ.

The tarso-metatarsal joints are found between certain articular facets on the cuboid and three cuneiform bones on the one hand, and others on the bases of the five metatarsal bones. These articulations are associated with three distinct synovial cavities-namely, a medial, lateral, and intermediate.

(1) The medial tarso-metatarsal articulation occurs between the anterior convex reniform surface of the first cuneiform bone and the concavo-reniform surface on the posterior aspect of the base of the first metatarsal bone.

Ligaments which form the fibrous stratum of the articular capsule surround the articulation. In the capsule the ligamenta tarsometatarsea dorsalia et plantaria are its strongest parts, but it is not deficient either on the medial or on the lateral aspects.

A separate synovial stratum lines the fibrous stratum.

(2) The intermediate tarso-metatarsal articulation is an elaborate joint. It involves the three cuneiform bones and the bases of the second, third, and part of the fourth metatarsal bones.

The articulation presents the outline of an indented parapet both on its tarsal and its metatarsal aspects. Thus, on its tarsal side, the first and the third cuneiform bones project in front of the second cuneiform, so that the latter only presents a distal surface to the articulation; while the first cuneiform presents a portion of its lateral surface, and the third cuneiform presents both its distal and portions of its lateral and medial surfaces, since it projects in front of the cuboid bone. metatarsal side the base of the second metatarsal bone fits into the indentation between the third and first cuneiforms, to which it presents lateral and medial articular facets, but its posterior facet rests upon the anterior facet of the second cuneiform. The base of the third metatarsal bone rests its posterior facet upon the third cuneiform. The fourth metatarsal base presents part of its medial facet to the lateral side of the third cuneiform. In this way the indentations alternate on the two sides of the articulation, and an extremely powerful interlocking of parts is provided, which places any marked independent movement of these metatarsal bones entirely out of the question.

The ligamenta tarsometatarsea dorsalia are broad, flat bands which represent the most distinct part of the fibrous stratum of an investing articular capsule. They pass from behind forwards, and while the second metatarsal bone receives three, i.e. one from each cuneiform, the third metatarsal only receives one-from the third cuneiform.

The ligamenta tarsometatarsea plantaria correspond with the foregoing in their general arrangement, but they are weaker. That for the second metatarsal is the strongest. Oblique bands extend from the first cuneiform bone to the second and third metatarsals.

The ligamenta cuneometatarsea interossea are three in number. The medial connects the lateral side of the first cuneiform with the medial side of the base of the second metatarsal bone. The middle connects the medial side of the third cuneiform with the lateral side of the base of the second metatarsal. The lateral connects the adjacent lateral sides of the third cuneiform and third metatarsal.

The stratum synoviale, which lines this articulation, sends a prolongation backwards between the first and second cuneiform bones, where it opens into the cuneonavicular joint. It is likewise prolonged forwards upon both sides of each of the bases of the second and third metatarsal bones.

(3) The lateral tarso-metatarsal articulation is found between the proximal surfaces of the bases of the fourth and fifth metatarsal bones and the distal surface of the cuboid.

The fibrous stratum of the investing articular capsule may be resolved into the following ligaments

The ligamenta tarsometatarsea dorsalia resemble those already described. The base of the fourth metatarsal receives one from the third cuneiform and one from the cuboid. The base of the fifth metatarsal receives one from the cuboid.

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