THE LOWER EXTREMITY
THE TIBIA
The Tibia is situated at the anterior und inner side of the leg, and, excepting the femur, is the longest and largest bone in the skeleton. It is pris-moid in form, expanded above, where it enters into formation with the knee joint, and more slightly below. In the male, its direction is vertical, and parallel with the bone of the opposite Bide, but in the female it has a slight oblique direction downwards and outwards, to compensate for the oblique direction of the femur inwards. It presents for examination a shaft and two extremities.
The Superior Extremity, or head, is large and expanded on each side into two lateral eminences, the tuberosities. Superiorly, the tuberosities present two smooth concave surfaces, which articulate with the con-dyles of the femur; the internal articular surface is longer than the external, oval from before backwards, to articulate with the internal condyle; the external one being broader, flatter, and more circular, to articulate with the external condyle. Between the two articular surfaces, and nearer the posterior than the anterior aspect of the bone, is an eminence, the spinous process of the tibia, surmounted by a prominent tubercle on each side, which give attachment to the extremities of the semilunar fibro-cartilages; and in front and behind the spinous process, a rough depression for the attachment of the anterior and posterior crucial ligaments and the semilunar cartilages. Anteriorly the tuberosities are continuous with one another, presenting a large and somewhat flattened triangular surface, broad above, and perforated by large vascular foramina, narrow below, where it terminates in a prominent oblong elevation of large size, the tubercle of the tibia; the lower half of this tubercle is rough, for the attachment of the ligamentum patellae; the upper half is a smooth facet corresponding, in the recent state, with a bursa which separates this ligament from the bone. Posteriorly, the tuberosities are separated from each other above by a shallow depression, the popliteal notch, which gives attachment to the posterior crucial ligament. The posterior surface of the inner tuberosity presents a deep transverse groove, for the insertion of the tendon of the Semi-membranosus; and the posterior surface of the outer one, a flat articular facet, nearly circular in form, directed downwards, backwards, and outwards, for articulation with the fibula. The lateral surfaces are convex and rough, the internal one, the most prominent, gives attachment below to the internal lateral ligament.
Tibia
The Shaft of the tibia is of a triangular prismoid form, broad above, gradually decreasing in size to the commencement of its lower fourth, its most slender part, and then enlarges again towards its lower extremity. It presents for examination three surfaces and three borders.
The anterior border, the most prominent of the three, is called the crest of the tibia, or in popular language, the shin; it commences above at the tubercle, and terminates below at the anterior margin of the inner malleolus. This border is very prominent in the upper two-thirds of its extent, smooth and rounded below. It presents a very flexuous course, being curved outwards above, and inwards below; it gives attachment to the deep fascia of the leg.
The internal border is smooth and rounded above and below, but more prominent in the centre; it commences at the back part of the inner tuberosity, and terminates at the posterior border of the internal malleolus; its upper third gives attachment to the internal lateral ligament of the knee, and to some fibres of the Popliteus muscle; its middle third, to some fibres of the Soleus and Flexor longus digitorum muscles.
The external border is thin and prominent, especially its central part, and gives attachment to the interosseous membrane; it commences above in front of the fibular articular facet, and bifurcates below, forming the boundaries of a triangular rough surface, for the attachment of the inferior interosseous ligament, connecting the tibia and fibula.
The internal surface is smooth, convex, and broader above than below; its upper third, directed forwards and inwards, is covered by the aponeurosis derived from the tendon of the Sartorius, and by the tendons of the Gracilis and Semi-tendinosus, all of which are inserted nearly as far forwards, as the anterior border; in the rest of its extent it is sub-cutaneous.
The external surface is narrower than the internal, its upper two-thirds present a shallow groove for the attachment of the Tibialis anticus muscle; its lower third is smooth, convex, curves gradually forwards to the anterior part of the bone, and is covered from within outwards by the tendons of the following muscles: Tibialis anticus, Extensor proprius pollicis, Extensor longus digitorum, Peroneus tertius.
The posterior surface presents at its upper part a prominent ridge, the oblique line of the tibia, which extends from the back part of the articular facet for the fibula, obliquely downwards, to the internal border, at the junction of its upper and middle thirds. It marks the limit for the insertion of the Popliteus muscle, and serves for the attachment of the popliteal fascia, and part of the Soleus, Flexor longus digitorum, and Tibialis posticus muscles; the triangular concave surface, above, and to the inner side of this line, gives attachment to the Popliteus muscle. The middle third of the posterior surface is divided by a vertical ridge into two lateral halves; the ridge is well marked at its commencement at the oblique line, but becomes gradually indistinct below; the inner and broadest half gives attachment to the Flexor longus digitorum, the outer and narrowest, to part of the Tibialis posticus. The remaining part of the bone is covered by the Tibialis posticus, Flexor longus digitorum, and Flexor longus pollicis muscles. Immediately below the oblique line is the medullary foramen, which is directed obliquely downwards.
The Lower Extremity, much smaller than the upper, is somewhat quadrilateral in form, and prolonged downwards, on its inner side, into a strong process, the internal malleolus. The inferior surface of the bone presents a quadrilateral smooth surface, for articulation with the astragalus; narrow internally, where it becomes continuous with the articular surface of the inner malleolus, broader externally, and traversed from before backwards by a slight elevation, separating two lateral depressions. The anterior surface is smooth and rounded above, and covered by the tendons of the Extensor muscles of the toes; its lower margin presents a rough transverse depression, for the attachment of the anterior ligament of the ankle joint. The posterior surface presents a superficial groove directed obliquely downwards and inwards, continuous with a similar groove on the posterior extremity of the astragalus, it serves for the passage of the tendon of the Flexor longus pollicis. The external surface presents a triangular rough depression, the lower part of which, in some bones, is smooth, covered with cartilage in the recent state and articulates with the fibula, the remaining part is rough for the attachment of the inferior interosseous ligament, which connects it with the fibula. This surface is bounded by two prominent ridges, continuous above with the interosseous ridge; they afford attachment to the anterior and posterior tibio-fibular ligaments. The internal surface is prolonged downwards to form a strong pyramidal-shaped process, flattened from without inwards, the inner malleolus; its inner surf ace is convex and subcutaneous. Its outer surface, smooth and slightly concave, deepens the articular surface for the astragalus. Its anterior border is rough, for the attachment of ligamentous fibres. Its posterior border presents a broad and deep groove, directed obliquely downwards and inwards; it is occasionally double, and transmits the tendons of the Tibialis posticus and Flexor longus digitorum muscles. Its summit is marked by a rough depression behind, for the attachment of the internal lateral ligament of the ankle joint.
Tibia
Structure. Like that of the other long bones.
Development. By three centres: one for the shaft, and one for each extremity. Ossification commences in the centre of the shaft about the same time Ossification commences in the centre of the shaft about the same time
as in the femur, the fifth week, and gradually extends towards either extremity. The centre for the upper epiphysis appears at birth; it is flattened in form, and has a thin tongue-shaped process in front, which forms the tubercle. That for the lower epiphysis appears in the second year. The lower epiphysis joins the shaft at about the twentieth year, and the upper one about the twenty-fifth year. Two additional centres occasionally exist, one for the tongue-shaped process of the upper epiphysis, the tubercle, and one for the inner malleolus.
Articulations. With three bones: the femur, fibula, and astragalus.
Attachment of Muscles. To the inner tuberosity, the Semi-membra-nosus. To the outer tuberosity, the Tibialis anticus and Extensor longus digitorum: to the shaft; its internal surface, the Sartorius, Gracilis, and Semi-tendinosus: to its external surface, the Tibialis anticus: to its posterior surface, the Popliteus, Soleus, Flexor longus digitorum, and Tibialis posticus: to the tubercle, the ligamentum patellae.
Development of Tibia
THE FIBULA
The Fibula is situated at the outer side of the leg. It is the smaller of the two bones, and, in proportion to its length, the most slender of all the long bones; it is placed nearly parallel with the tibia, its lower extremity inclining a little forwards, so as to be on a plane anterior to that of the upper end. It presents for examination a shaft and two extremities.
The Superior Extremity or Head, is of an irregular rounded form, presenting above a flattened articular facet, directed upwards and inwards, for articulation with a corresponding facet on the external tuberosity of the tibia. On the outer side is a thick and rough prominence, continued behind into a pointed eminence, the styloid process, which projects upwards from the posterior part of the head. The prominence above mentioned gives attachment to the tendon of the Biceps muscle, and to the long external lateral ligament of the knee, the ligament dividing this tendon into two parts. The summit of the styloid process gives attachment to the short external lateral ligament. The remaining part of the circumference of the head is rough, for the attachment, in front, of the anterior superior tibio-fibular ligament, and the upper and anterior part of the Peroneus longus; and behind, to the posterior superior tibio-fibular ligament, and the upper fibres of the outer head of the Soleus muscle.
The Lower Extremity, called the malleolus externus, is of a pyramidal form, somewhat flattened from without inwards, and is longer, and descends lower than the internal malleolus. Its external surface is convex, sub-cutaneous, and continuous with a triangular (also sub-cutaneous) surface on the outer side of the shaft. The internal surface presents in front a smooth triangular facet, broader above than below, convex from above downwards, which articulates with a corresponding surface on the outer side of the astragalus. Behind and beneath the articular surface is a rough depression, which gives attachment to the posterior fasciculus of the external lateral ligament of the ankle. Its anterior border is thick and rough, and marked below by a depression for the attachment of the anterior fasciculus of the external lateral ligament. The posterior border is broad and marked by a shallow groove, for the passage of the tendons of the Peroneus longus and brevis muscles. Its summit is rounded, and gives attachment to the middle fasciculus of the external lateral ligament.
The Shaft presents three surfaces, and three borders. The anterior border commences above in front of the head, runs vertically downwards to a little below the middle of the bone, and then curving a little outwards, bifurcates below into two lines, which bound the triangular sub-cutaneous surface immediately above the outer side of the malleolus externus. It gives attachment to an inter-muscular septum, which separates the muscles on the anterior surface from those on the external.
The internal border or interosseous ridge, is situated close to the inner side of the preceding, it runs nearly parallel with it in the upper third of its extent, but diverges from it so as to include a broader space in the lower two-thirds. It commences above just beneath the head of the bone (sometimes it is quite indistinct for about an inch below the head), and terminates below at the apex of a rough triangular surface immediately above the articular facet of the external malleolus. It serves for the attachment of the interosseous membrane, and separates the extensor muscles in front, from the flexor muscles behind. The portion of bone included between the anterior and interosseous lines, forms the anterior surface.
The posterior border is sharp and prominent; it commences above at the base of the styloid process, and terminates below in the posterior border of the outer malleolus. It is directed outwards above, backwards in the middle of its course, backwards and a little inwards below, and gives attachment to an aponeurosis which separates the muscles on the outer from those on the inner surface of the shaft. The portion of bone included between this line and the interosseous ridge, forms the internal surface. Its upper three-fourths are subdivided into two parts, an anterior and a posterior, by a very prominent ridge, the oblique line of the tibia, which commences above at the inner side of the head, and terminates by being continuous with the interosseous ridge at the lower fourth of the bone. It attaches an aponeurosis which separates the Tibialis posticus from the Soleus above, and the Flexor longus pollicis below. This ridge sometimes ceases just before approaching the interosseous ridge.
The anterior surface is the interval between the anterior and interosseous lines. It is extremely narrow and flat in the upper third of its extent; broader and grooved longitudinally in its lower third; it serves for the attachment of three muscles, the Extensor longus digitorum, Peroneus tertius, and Extensor longus pollicis.
The external surface, much broader than the preceding, is directed outwards in the upper two-thirds of its course, backwards in the lower third, where it is continuous with the posterior border of the external malleolus. This surface is completely occupied by the Peroneus longus and brevis muscles.
The internal surface is the interval between the interosseous ridge and the posterior border, and occupies nearly two-thirds of the circumference of the bone. Its upper three-fourths are divided into an anterior and a posterior portion by a very prominent ridge already mentioned, the oblique line of the fibula. The anterior portion is directed inwards, and is grooved for the attachment of the Tibialis posticus muscle. The posterior portion is continuous below with the rough triangular surface above the articular facet of the outer malleolus; it is directed backwards above, backwards and inwards at its middle, directly inwards below. Its upper fourth is rough, for the attachment of the Soleus muscle; its lower part presents a triangular rough surface, connected to the tibia by a strong interosseous ligament, and between these two points, the entire surface is covered by the fibres of origin of the Flexor longus pollicis muscle. At about the middle of this surface is the nutritious foramen, which is directed downwards.
Fibula
Articulations. With two bones; the tibia and astragalus.
Development. By three centres; one for the shaft, and one for each extremity. Ossification commences in the shaft about the sixth week of foetal life, a little later than in the tibia, and extends gradually towards the extremities. At birth both ends are cartilaginous. Ossification commences in the lower end in the second year, and hi the upper one about the fourth year. The lower epiphysis, the first in which ossification commences, becomes united to the shaft about the twentieth year, contrary to the law which appears to prevail with regard to the junction of the epiphyses with the shaft; the upper one is joined about the twenty-fifth year.
Attachment of Muscles. To the head, the Biceps, Soleus, and Peroneus longus: to the shaft, its anterior surface, the Extensor longus digito-, rum, Peroueus tertius, and Extensor longus pol-licis: to the internal surface, the Soleus, Tibialis posticus, and Flexor longus pollicis: to the external surface, the Peroneus longus and brevis. PREVIOUS PAGE
