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month of fœtal life, and is of service from a medico-legal standpoint in determining the age of the foetus. According to Hartman, it is absent in about 12 per cent. of children at term, and may appear as early as the eighth month of foetal life in about 7 per cent. The proximal extremity, entirely cartilaginous at birth, comprises the head, neck, and trochanter major. A centre appears for the head during the early part of the first year. It is worthy of note that this epiphysis has a double blood-supply-one through the neck, the other through the ligamentum teres. That for the trochanter major begins to ossify about the second or third year, whilst the neck is developed as a proximal extension of the body, which is, however, not confined to the neck alone, but forms
the distal circumference of
the articular head, as may
Appears early in 2nd month of foetal life
the 9th month of
be seen in bones up to the Usually appears in
About 12 years.
Fuses with shaft about 20-22 years
The epiphysis of the greater trochanter unites with the body and neck about eighteen or nineteen, whilst the epiphysis for the trochanter minor, which usually makes its appearance about the twelfth or thirteenth year, is usually completely fused with the body about age of eighteen. The epiphysis for the distal end, although the first to ossify, is not completely united to the body until from about the twentieth to the twenty-second year. It is worthy of note that the line of fusion of the body and distal epiphysis passes through the adductor tubercle, a point which can easily be determined in the living. The distal end is the so-called "growing end of the bone."
The patella, the largest of the sesamoid bones, overlies the front of the kneeOf compressed form and joint in the tendon of the quadriceps extensor. somewhat triangular shape, its distal angle forms a peak, called the apex patella, whilst its proximal edge, or base (basis patella), broad, thick, and sloping forwards and a little distally, is divided into two areas by a transverse line or groove; the anterior area so defined serves for the attachment of the common tendon of the quadriceps extensor muscle, whilst the posterior, of compressed triangular shape, is covered with synovial membrane. The medial and lateral borders, of curved outline, receive the insertions of the vastus medialis and lateralis muscles, respectively, the attachment of the vastus medialis being more extensive than that of the vastus lateralis. The anterior surface of the bone, slightly convex in both diameters, has a fibrous appearance, due to its longitudinal striation, and is pierced here and there by the openings of vascular canals. Oftentimes at the superior lateral angle there is a well-defined area for the tendinous insertion of the vastus lateralis. The posterior or articular surface is divided into two unequal parts (of which the lateral is the wider) by a vertical elevation which glides in the furrow of the patellar surface of the femur, and in extreme flexion passes to occupy the intercondyloid fossa. The lateral of the two femoral surfaces is slightly concave in both its diameters; the medial, though slightly concave proximo-distally, is
usually plane, or somewhat convex transversely. Occasionally, in the macerated bone, indications of a third vertical area are to be noted along the medial edge of the posterior aspect. This defines the part of the articular surface which rests on the lateral border of LATERAL ARTICULAR FACET the medial condyle in
MEDIAL ARTICULAR FACET
Surface for the ligamentum patellæ
the recent condition, when the femoral surface is coated with cartilage, a more complex arrangement of facets may be in some cases displayed (as indicated in Fig. 244). Lamont (Journal of Anat. and Physiol., 1910, vol. xliv. p. 149) has shown that these areas undergo considerable variation in
their arrangement in races who habitually adopt the squatting posture. Distal to the femoral articular area the posterior surface of the apex is rough and irregular; the greater part of this is covered with synovial membrane, the ligamentum patella being attached to its summit and margins, reaching some little distance round the borders on to the anterior aspect of this part of the bone.
Ossification. The patella is laid down in cartilage about the third month of fœtal life. At birth it is cartilaginous, and the tendon of the quadriceps is continuous with the ligamentum patellæ over its anterior surface, and can easily be dissected off. About the third year an ossific centre appears in it and spreads more particularly over its deeper surface. Two centres, vertically disposed, have also been described. Ossification is usually completed by the age of puberty.
The tibia is the medial bone of the leg. It is much stouter and stronger than its neighbour the fibula, with which it is united proximally and distally. By its
proximal expanded ex
tremity it supports the
condyles of the femur, Anterior cruciate ligament
while distally it shares in the formation of the ankle-joint, articulating with the proximal surface and medial side of the talus.
The proximal extremity comprises the medial and lateral condyles (O.T. tuberosities), the intercondyloid eminence (O.T. spine), and the tuberosity.
Surface for attach. of post. extrem. of medial meniscus
Post. cruciate ligament
FIG. 246. THE PROXIMAL SURFACE OF THE PROXIMAL EXTREMITY
Each condyle is provided on its proximal aspect with an articular surface (facies articularis superior), which supports the corresponding femoral condyle, as well as the interposed meniscus. Of these two condylic surfaces the medial is the larger. Of oval shape, its long axis is placed antero-posteriorly; slightly concave from before backwards and from side to side, its circumference rises in the form of a sharp and well-defined edge. The lateral condylic surface is smaller and rounder. Slightly concave from side to side, and gently convex from before backwards, its circumfer
ence is well defined in front, but is rounded off behind, thus markedly increasing the convexity of its posterior part. Between the two condylic surfaces the bone is raised in the centre to form the intercondyloid eminence which consists of two intercondyloid tubercles separated by an oblique groove, in the anterior part of which lies the anterior cruciate ligament. The medial tubercle (tuberculum intercondyloideum mediale), the higher, is prolonged backwards and laterally by an oblique ridge to which part of the posterior cornu of the lateral meniscus is attached. The lateral tubercle (tuberculum intercondyloideum laterale) is more pointed and not so elevated. In front of and behind the intercondyloid eminence the articular areas are separated by two irregular V-shaped surfaces, the intercondyloid fossæ. The anterior intercondyloid fossa, the larger and wider, furnishes areas for the attachment of the menisci on either side, and for the anterior cruciate ligament immediately in front of the intercondyloid eminence. The floor of this space is pierced by many nutrient foramina. The posterior intercondyloid fossa is concave from side to side, and slopes downwards and backwards. The lateral meniscus is attached near its apex to a surface which rises on to the back of the intercondyloid eminence; the medial meniscus is fixed to a groove which runs along its medial edge, and the posterior cruciate ligament derives an attachment from the smooth posterior rounded surface.
The lateral condyle is the smaller of the two. It overhangs the body to a greater extent than the medial, though this is obscured. in the living by its articulation with the fibula. The facet for the fibula, often small and indistinct, is placed postero-laterally on the distal surface of its most projecting part. Antero-laterally the imprint caused by the attachment of the trachis iliotibialis (O.T. ilio-tibial band) is often quite distinct. Curving distally and forwards from the fibular facet there is often a definite ridge for the attachment of the expansion of the biceps tendon;
ANTERIOR PART OF
FIG. 247. THE RIGHT TIBIA AND FIBULA AS SEEN
The anterior part of the medial surface of the fibula is coloured
distal to this the areas for the origins of the peronæus longus and extensor digitorum longus are often crisply defined. The circumference of the medial condyle is grooved postero-medially for the insertion of the tendon of the semi-membranosus.
In front of the condyles, and about an inch distal to the level of the condylic surfaces, there is an oval elevation called the tuberosity of the tibia. The proximal half of this is smooth and covered by a bursa, while the distal part is rough and serves for the attachment of the ligamentum patellæ.
Considered in its entirety, the proximal extremity of the tibia is broader transversely than antero-posteriorly, and is inclined backwards so as to overhang the shaft posteriorly.
The corpus tibiæ (body) is irregularly three-sided, possessing a medial, a lateral, and a posterior surface, separated by an anterior crest, a medial margin, and a lateral or interosseous crest. It is narrowest about the junction of its middle and distal thirds, and expands proximally and distally to support the extremities. Running along the front of the bone there is a gently-curved, prominent margin, the crista anterior, confluent proximally with the tuberosity, but fading away distally
on the anterior surface of the distal third of the bone, where it may be traced in the direction of the anterior border of the medial malleolus. This is the anterior crest or shin, which is subcutaneous throughout its entire length. To the medial side of this is a smooth, slightly convex SEMITENDINOSUS Surface, which reaches the medial condyle proximally, and distally becomes continuous with the medial surface of the medial malleolus. This is the medial or subcutaneous surface of the body, which is covered only by skin and superficial fascia, except in its proximal fourth, where the tendons of the sartorius, gracilis, and semitendinosus muscles overlie it, as they pass towards their insertions. This surface is limited posteriorly by the medial margin, which passes from the medial and distal surface of the medial condyle proximally to the posterior border of the medial malleolus distally. This margin is rounded and indefinite proximally and distally, being usually best marked about its middle third. To the lateral side of the anterior crest is the lateral surface of the bone; it is limited behind by a straight vertical ridge, the crista interossea (interosseous crest), to which the interosseous membrane, which occupies the interval between the tibia and the fibula, is attached. This ridge commences near the middle of the lateral and distal surface of the lateral condyle, and terminates about two inches from the distal extremity by dividing into two lines, which separate and enclose between them the surface for articulation with the distal end of the fibula, and the area of attachment of the interosseous ligament, which here unites the two bones. In its proximal two-thirds the lateral surface provides an extensive origin for the tibialis anterior. Distally, where the anterior crest is no longer well defined, the lateral surface turns forwards on to the front of the body, and is limited by the anterior margin of the distal articular surface. Over this the tendon of the tibialis anterior, and the combined fleshy and tendinous parts of the extensor hallucis proprius and extensor digitorum longus muscles pass obliquely distally. The posterior surface of the body lies between the interosseous crest laterally and the medial margin on the medial side. Its contours are liable to considerable variation according to the degree of side to side compression of the bone. It is usually full
and rounded proximally, and flat distally. Proximally it is crossed by the linea poplitea (popliteal line), which runs distally and medially, from the fibular facet to the medial border on a level with the junction of the middle with the proximal third of the body. To this line the deep transverse fascia is attached, whilst distal to it, as well as from the medial border of the bone distally, the soleus muscle takes origin. Into the bulk of the triangular area proximal to it the popliteus muscle is inserted. Arising from the middle of the popliteal line there is a vertical ridge, which passes distally and divides the posterior aspect of the body into two surfaces-a lateral for the tibial origin of the tibialis posterior muscle, and a medial for the flexor digitorum longus muscle. The distal third of this surface of the body is free from muscular attachments, but is overlain by the tendons of the above muscles, together with that of the flexor hallucis longus. A large nutrient canal, having a distal direction, opens on the posterior surface of the body a little distal to the popliteal line and just lateral to the vertical ridge which springs from it.
The distal extremity of the tibia displays an expanded quadrangular form. It is furnished with a saddle-shaped articular surface on its distal surface (facies articularis inferior), which is concave from before backwards and slightly convex from side to side. This rests upon the upper articular surface of the body of the talus, and is bounded in front and behind by well-defined borders. The anterior border is the rounder and thicker, and is oftentimes channelled by a groove for the attachment of the anterior ligament of the joint; further, it is occasionally provided with a pressure facet caused by the locking of the bone against the neck of the talus in extreme flexion. Laterally the edge of the articular area corresponds to the base of the triangle formed by the splitting of the interosseous ridge into two parts. Where these two lines join it, both in front and behind, the bone is elevated into the form of tubercles, in the hollow between which (incisura fibularis) the, distal end of the fibula is lodged, being held in position by powerful ligaments. The cartilage-covered surface occasionally extends for some little distance proximal to the base of the triangle. Medially there is a process projecting distally, and called the medial malleolus, the medial aspect of which is subcutaneous and forms the projection of the medial ankle. Its lateral surface is furnished with a piriform facet (facies articularis malleolaris), confluent with the cartilagecovered area on the tarsal surface of the distal extremity; this articulates with a corresponding area on the medial surface of the body of the talus. Distally the malleolus is pointed in front, but notched behind for the attachment of the deltoid or tibial collateral ligament of the ankle. Running obliquely along the posterior surface of the malleolus there is a broad groove (sulcus malleolaris) in which the tendons of the tibialis posterior and flexor digitorum longus muscles are lodged; whilst a little to the fibular side of this, and running distally over the posterior surface of the distal extremity of the bone, there is another groove; often faintly marked, for the lodgment of the tendon of the flexor hallucis longus muscle.
The proportionate length of the tibia to the body height is as 1 is to 4:32–4·80. Arterial Foramina.-Nutrient canals are seen piercing the proximal extremity of the bone around its circumference and proximal to the tuberosity. The floors of the intercondyloid fossæ are also similarly pierced, and there is usually a canal of large size opening on the summit of the intercondyloid eminence. Two or three foramina of fair size are seen running proximally into the substance of the bone a little distal to and to the medial side of the tuberosity, while the principal vessel for the body passes distally into the bone on its posterior surface, about the level of the junction of the proximal and middle thirds. The medial surface of the medial malleolus, as well as the anterior and posterior borders of the distal extremity, are likewise pitted by the orifices of small vascular channels.
Connexions. Proximally the tibia supports the condyles of the femur, and is connected in front with the patella by means of the patellar ligament. Articulating laterally with the fibula proximally and distally, it is united to that bone throughout nearly its entire length by the interOsseous membrane. The anterior crest and medial surface can be readily examined, as they are subcutaneous, except proximally, where the medial surface is overlain by the thin tendinous aponeuroses of the muscles passing over the medial side of the knee. The form of the distal part of the knee in front is determined by the condyles on either side crossed centrally by the ligamentum patellæ. Distally the medial malleolus forms the projection of the medial ankle, which is wider, not so low, less pointed, and extends further forwards than the projection of the lateral