Thieme Dissector Volume 2 (eBook)

Introduction

The lower limbs are caudal extensions (appendages) from the trunk, specialized for the transmission of the body weight and locomotion. The lower limb extends from hip to the toes. It comprises four major parts or regions: the gluteal, thigh, leg, and foot (Fig. 1.1).

The Common people’s reference of lower limb as the leg, is in fact the part of lower limb between knee and foot.

Gluteal region: The gluteal region overlies the side and back of the pelvis. The gluteal region comprises a rounded prominent region, the buttock, and a less prominent region, the hip. It extends from the waist down to the gluteal fold, which limits the buttock inferiorly and to the hollow on the lateral side of the hip. Usually, the hip and buttock are not clearly distinguished from each other. The hip is the lateral aspect of region while buttock is rounded bulge behind. The groove between the buttocks is called the natal cleft. The lower part of the sacrum and coccyx can be felt in this groove. Anterior to the gluteal region lies the perineum, in the depth of the cleft, and continues forward between the thighs.

This region contains the hip bone. It comprises three parts, the ilium, ischium, and pubis, which are fused together at the acetabulum where the head of the femur articulates with it. The ilium is the expanded upper part with a crest, the iliac crest, which can be felt in the lower margin of the waist at the level between the L3 and L4 vertebrae. The ischium is the posteroinferior part. It consists of the ischial tuberosity and ramus on which the body rests during the sitting position. The pubis is the anterior part and comprises a body and superior and inferior pubic rami. The body of the pubis articulates with its fellow of the opposite side through a median fibrocartilaginous pad, the pubic symphysis. It may be felt at the lower end of the abdominal wall in the median plane. Draw your finger laterally from the symphysis on the anterosuperior surface of the body of the pubis. The bone felt is the pubic crest which ends in a small, blunt prominence, the pubic tubercle 2.5 cm laterally. In males, it is not easily palpable as it is covered by the spermatic cord.

Thigh region: The thigh region lies between the gluteal, abdominal, and perineal regions proximally and the knee region distally. It contains the femur, which connects the hip and the knee. The femur articulates at the upper end with the hip bone to form the hip joint and at the lower end with the tibia and patella to form the knee joint.

The junction between the trunk and lower limb is abrupt anteromedially. The boundary between abdomen and lower limb, the inguinal ligament extends between anterior superior iliac spine and pubic tubercle. This junction between the two regions is called the inguinal region or groin.

Leg (L. crus) or leg region: The leg region extends from the knee joint to the ankle joint. The leg contains two bones, the tibia and fibula which are united along the length by interosseous membrane. The soft fleshy prominence on the back of the leg is called the calf and is formed by the triceps surae muscle. The lower end of the tibia and fibula form prominences on the medial and lateral sides of the ankle to form the medial and lateral malleoli. The flattened upper surface of the expanded proximal end of the tibia articulates with the lower end of the femur at the knee joint. The proximal end of the fibula articulates with the inferolateral surfaces of the lateral condyle of the tibia and does not take part in the formation of the knee joint.

Foot (L. Pes) or foot region: The foot region is the distal part of the lower limb and extends from the heel to the tips of the toes. It contains the tarsus, metatarsals, and phalanges. Its superior surface is the dorsum of the foot, while its inferior surface is the sole of the foot, which comes in contact with the ground.

An Overview of the Bones of the Lower Limb

A brief account of the bones of the lower limb is necessary before beginning to dissect so that the student studies the surface anatomy and relates it to the appropriate dried bone. The bones of the lower limb include the hip bone, femur, patella, tibia, fibula, and foot bones (Fig. 1.2).

Hip bone (Fig. 1.3): Hip bone is a large, flat bone formed by the fusion of three primary bones, the ilium, ischium, and pubis. At birth, the components are joined with each other by a Y-shaped triradiate hyaline cartilage (Fig. 1.3). By adulthood, they are ossified.

The hip bone looks like a propeller with a large sinuous blade directed upward and a smaller blade directed downward. The upper blade is called the ilium and the lower blade consists of the ischium and pubis. It is perforated by a large aperture, the obturator foramen. The lateral aspect of the hip bone at the junction of the two blades presents a cup-shaped hollow called the acetabulum. Posteriorly, each hip bone articulates with the sacrum at the sacroiliac joint.

Ilium: Ilium’s flattened upper border is called the iliac crest. It runs backward from the anterior superior iliac spine to the posterior superior iliac spine. It can be felt at the lower margin of the waist and below each of these spines are the corresponding inferior spines. The outer surface of the ilium is termed the “gluteal surface,” which provides attachment to the gluteal muscles. The inferior, anterior, and posterior gluteal lines demarcate bony attachments of these muscles. The inner surface of the ilium is smooth and hollowed out to form the iliac fossa. It provides attachment to the iliacus muscle. The articular surface of the ilium articulates with the sacrum at the sacroiliac joints. The iliopectineal line runs anteriorly on the inner surface of the ilium, from the auricular surface to the pubis.

Ischium: Ischium forms the posteroinferior part of the hip bone. It comprises a spine on its posterior part which demarcates the greater sciatic notch (above) from the lesser sciatic notch (below). The ischial tuberosity is a thickening on the lower part of the body of the ischium which bears the body’s weight in the sitting position. The ischial ramus projects forward from the tuberosity to meet with the inferior pubic ramus to form the ischiopubic ramus.

Pubis: Pubis forms the anteromedial part of the hip bone. It comprises a body and superior and inferior pubic rami. It articulates with the pubic bone of the contralateral side by a secondary cartilaginous joint (the symphysis pubis). The superior surface of the body bears the pubic crest and the pubic tubercle. The large obturator foramen is bounded by the pubis, ischium, and their rami.

Femur (Fig. 1.4): The femur is the longest and heaviest bone in the body. It transmits the body weight from the hip bone to the tibia. It presents the following characteristic features:

1.Femoral head: It articulates with the acetabulum of the hip bone at the hip joint. It extends from the femoral neck and is rounded and smooth. It forms two-thirds of the sphere and is covered with articular cartilage except for a medially placed depression or pit called the fovea to which the ligamentum teres is attached. This configuration permits a wide range of movement. The head faces medially, upward and forward into the acetabulum.

2.Femoral neck: It forms an angle of 125 degrees with the femoral shaft, the neck shaft angle. This angle is less in females because of the increased width of the pelvis.

3.Femoral shaft: It constitutes the length of the bone. At its upper end, it carries the greater trochanter placed superolaterally and the lesser trochanter placed posteromedially. Anteriorly the rough intertrochanteric line and posteriorly the smooth trochanteric crest demarcate the junction between the shaft and the neck. The linea aspera is the crest seen running longitudinally along the posterior surface of the femur. It splits in the lower portion into the medial and lateral supracondylar lines. The medial supracondylar line terminates at the adductor tubercle.

The lower end of the femur presents the medial and lateral condyles. These condyles bear the articular...