BONES AND LIGAMENTS AT HIP
The femur is the longest and strongest bone in the body, comprising a shaft and two irregular extremities that articulate at the hip and knee joints (see Plate 2-19).
The superior extremity of the bone has a nearly spherical head mounted on an angulated neck, and prominent trochanters provide for muscular attachments. The head is smooth, with an articular surface that is largest above and anteriorly; this is interrupted medially by a depression, the fovea capitis femoris, into which attaches the capitis femoris ligament.
|OSTEOLOGY OF THE FEMUR|
The neck is about 5 cm long and forms an angle with the shaft, which varies in the normal person from 115 to 140 degrees. It is compressed anteroposteriorly and contains a large number of prominent pits for the entrance of blood vessels.
The greater trochanter is the bony prominence of the hip. It is palpable 12 to 14 cm below the iliac crest, is large and square, and marks the upper end of the shaft of the femur. Its large quadrilateral surface is divided by an oblique ridge running from the posterosuperior to its anteroinferior angles. In front and above the ridge there is a triangular surface (which may be smooth) for a bursa. Below and behind the ridge the bone is also smooth. Its posterior rounded border bounds the trochanteric fossa and continues downward as the inter- trochanteric crest. The trochanteric fossa is a deep pit on the internal aspect of the trochanter.
The lesser trochanter is a blunt, conical projection at the junction of the inferior border of the neck with the shaft of the femur. The trochanters are joined behind by the intertrochanteric crest. On the anterior surface of the femur, the junction of the neck and shaft is also ridged. This is the intertrochanteric line, which provides attachment for the capsule of the hip joint across the front of the bone and continues as a spiral line, winding backward to blend into the medial lip of the linea aspera.
The shaft of the bone is fairly uniform in caliber but broadens slightly at its extremities. It is bowed forward and its surface is smooth, except for the thickened ridge along its posterior surface, the linea aspera. This is especially prominent in the middle third of the bone, where lateral and medial lips are developed. Superiorly, the lateral lip blends with the prominent gluteal tuberosity; an intermediate lip extends as the pectineal line to the posterior border of the lesser trochanter; and the medial lip continues as the spiral line. The nutrient foramen of the femur, directed upward, is located on the linea aspera.
The inferior extremity of the femur is broadened about threefold for the knee joint. Its surfaces, except at the sides, are articular two oblong condyles for articulation with the tibia are separated by an intercondylar fossa and united anteriorly by the patellar surface. The wheel-like condyles are also curved from side to side. The intercondylar fossa is especially deep posteriorly and is separated by a ridge from the popliteal surface of the femur above. The medial condyle is longer than the lateral condyle. The condyles rest on the horizontal condyles of the tibia, and the shaft of the femur inclines downward and inward.
The epicondyles bulge above and within the curvatures of the condyles. The medial epicondyle is the more prominent, giving attachment to the tibial collateral ligament of the knee joint. It bears on its upper surface a pointed projection, the adductor tubercle. The lateral epicondyle gives rise to the fibular collateral ligament. A groove below the epicondyle borders the articular margin.
The femur is ossified from five centers: one for the shaft, one each for the head and inferior extremity, and one for each trochanter. The shaft is ossified at birth; ossification extends into the neck after birth. The center for the inferior extremity of the bone appears during the ninth month of fetal life; that for the head appears during the first year. The center in the greater trochanter appears during ages 3 to 5; that for the lesser trochanter appears at age 9 or 10. The epiphyses for the head and trochanters fuse with the shaft at ages 14 to 17; those at the knee fuse with the shaft at about age 1712.
Movements of the hip joint are flexion-extension, abduction-adduction, and medial and lateral rotation. Circumduction is also allowed.
The hip joint, a synovial ball-and-socket joint, consists of the articulation of the globular head of the femur in the cuplike acetabulum of the coxal bone (see Plate 2-20). Compared with the shoulder joint, it has greater stability and some decrease in freedom of movement. The head forms about two thirds of a sphere and is covered by articular cartilage, thickest above and thinning to an irregular line of termination at the junction of the head and neck. The acetabulum of the coxal bone exhibits a horseshoe-shaped articular surface arching around the acetabular fossa. The articular fossa lodges a mass of fat covered by synovial membrane; the transverse ligament of the acetabulum closes the fossa below. An acetabular labrum attaches to the bony rim and to the ligament. It attaches to the bony rim and to the ligament. Its thin, free edge cups around the head of the femur and holds it firmly.
The articular capsule of the joint is strong. It is attached to the bony rim of the acetabulum above and to the transverse ligament of the acetabulum inferiorly. On the femur, it is attached anteriorly to the intertrochanteric line and to the junction of the neck of the femur and its trochanters. Behind, the capsule has an arched free border, covering only two thirds of the neck of the femur distally. Most of the fibers of the capsule are longitudinal, running from the coxal bone to the femur, but some deeper fibers run circularly. These zona orbicularis fibers are most marked in the posterior part of the capsule; they help to hold the head of the femur in the acetabulum.
Three ligaments, as thickenings of the capsule, add strength. The very strong iliofemoral ligament lies on the anterior surface of the capsule, in the form of an inverted Y. Its stem is attached to the lower part of the anterior inferior iliac spine, with the diverging bands attaching below to the whole length of the intertrochanteric line. The iliofemoral ligament becomes taut in full extension of the femur and thus helps to maintain erect posture, because in this position the body’s weight tends to roll the pelvis backward on the femoral heads. The pubofemoral ligament is applied to the medial and inferior part of the capsule. Arising from the pubic part of the acetabulum and the obturator crest of the superior ramus of the pubis, this ligament reaches the underside of the neck of the femur and the iliofemoral ligament. The ligament becomes taut in extension and also limits abduction. The articular capsule is thinnest between the iliofemoral and pubofemoral ligaments but is crossed here by the robust iliopsoas tendon. The iliopectineal bursa lies between this tendon and the capsule. The ischiofemoral ligament forms the posterior margin of the capsule. It arises from the ischial portion of the acetabulum and spirals lateralward and upward, ending in the superior part of the femoral neck. The capitis femoris ligament, about 3.5 cm long, is intracapsular, arising from the two margins of the acetabular notch and the lower border of the transverse acetabular ligament and ending in the fossa of the head of the femur. It becomes taut in adduction of the femur.
The synovial membrane of the hip joint lines the articular capsule, covers the acetabular labrum, and is extended, sleevelike, over the ligament of the head of the femur. The membrane covers the fat of the acetabular notch and is reflected back along the femoral neck at the femoral attachment of the capsule. Blood vessels to the head and neck of the femur course under these synovial reflections.
The arteries of the hip joint are branches of the medial and lateral circumflex femoral arteries, the deep branch of the superior gluteal artery, and the inferior gluteal artery. The posterior branch of the obturator artery provides a significant portion of the blood supply of the femoral head. Nerve supply to the hip joint is derived from the nerves supplying the quadratus femoris and rectus femoris muscles, the anterior division of the obturator nerve (rarely also from the accessory obturator nerve), and the superior gluteal nerve.