Practical Lab 5: Lower Limb Bones - Hip and Proximal Femur Study Guide to the Proximal Femur
Administrative Information and Introduction to Lower Limb Anatomy
This material serves as the documentation for Practical Lab- of the Introduction to Anatomy course for year Medical Students during the Second Semester of the academic year. The instruction is provided by Dr. Abedallah Hamida, MBBS, PhD, from the Department of Anatomy and Histology at the School of Medicine, The University of Jordan. The focus of this laboratory session is the skeletal anatomy of the lower limb, specifically detailing the structures of the Hip bone and the Proximal End of the Femur.
Anatomical Overview and Major Divisions of the Hip Bone
The hip bone, also known as the coxal bone, is a large, irregularly shaped bone that forms the pelvic girdle. It is characterized by its fusion from three primary parts: the ilium, the ischium, and the pubis. The ilium is defined as the superior and largest part of the hip. The ischium constitutes the thick posteroinferior section. The pubis represents the anteroinferior portion. Two significant landmarks situated between these parts are the acetabulum and the obturator foramen. The acetabulum is a large, cup-shaped cavity located on the lateral surface of the hip bone, formed at the point where the ilium, ischium, and pubis fuse. It is directed laterally and serves to receive the head of the femur to form the hip joint. The obturator foramen is a substantial opening in the lower part of the hip bone, positioned between the pubis and the ischium. In a living subject, this foramen is mostly closed by the obturator membrane.
Structural Anatomy of the Ilium
The ilium is divided into two main components: the body and the wing, or ala. The body of the ilium is the smaller, inferior portion that contributes to the upper of the acetabulum. The wing is a broad, fan-shaped expansion characterized by four borders and two surfaces. The borders consist of the superior, anterior, posterior, and medial borders. The superior border is defined by the iliac crest, a thickened and curved border ending anteriorly at the Anterior Superior Iliac Spine (ASIS) and posteriorly at the Posterior Superior Iliac Spine (PSIS). The anterior border extends from the ASIS down toward the acetabulum and features the Anterior Inferior Iliac Spine (AIIS). The posterior border extends from the PSIS toward the ischium, featuring the Posterior Inferior Iliac Spine (PIIS) and the Greater sciatic notch. The medial border extends downward and forward on the medial surface from the iliac crest toward the pubis, dividing the medial surface into an anterior iliac fossa and a posterior sacropelvic surface. The lower portion of the medial border forms a rounded ridge called the arcuate line.
Surfaces and Muscular Origins of the Ilium
The ilium possesses both medial (inner) and lateral (outer) surfaces. The medial surface contains the iliac fossa, which is a shallow concave surface located below the iliac crest. The posterior part of this internal surface, known as the sacropelvic surface, contains the iliac tuberosity (a rough area below the dorsal iliac crest) and the auricular surface. The auricular surface is an ear-shaped articular surface that articulates with the sacrum to form the sacroiliac joint. The lateral or gluteal surface is divided into four distinct areas by three gluteal lines: the inferior, anterior, and posterior gluteal lines, all of which radiate from the upper margin of the greater sciatic notch. These areas provide the origin for the gluteal muscles: the Gluteus maximus originates posterior to the posterior gluteal line; the Gluteus medius originates between the posterior and anterior gluteal lines; and the Gluteus minimus originates between the anterior and inferior gluteal lines.
Structural Detail of the Ischium and Pubis
The ischium consists of a body and a ramus. The body of the ischium is located below and posterior to the acetabulum. Its posterior border contains the ischial spine and the lesser sciatic notch. The posteroinferior part of the body forms a large protuberance called the ischial tuberosity, which acts as a site for several muscle attachments. The ramus of the ischium arises from the lower body, running forward and medially to join the inferior ramus of the pubis, forming the conjoint ischiopubic ramus. The pubis consists of a body, a superior ramus, and an inferior ramus. The body of the pubis is located anteromedially and features the pubic tubercle on its anterosuperior aspect. The medial or symphyseal surface of the body articulates with the opposite pubis to form the pubic symphysis. The superior ramus arises from the superolateral angle of the body, extending laterally above the obturator foramen. It features the pectineal line (pecten pubis), which extends from the pubic tubercle and continues as the arcuate line of the ilium. The inferior ramus extends downward and laterally to meet the ischial ramus.
Anatomical Position and Identification Tricks for the Hip Bone
To correctly determine the side and anatomical position of the hip bone, it must be held so that the following criteria are met: the acetabulum must be directed laterally; the obturator foramen must lie below the acetabulum; the ilium must be directed upward; the pubis must be directed anteromedially; and the ischium must be directed posteroinferiorly. A practical trick for identification involves holding the bone such that the greater sciatic notch fits comfortably between the thumb and index finger, while the remaining fingers of that hand cover the acetabulum.
Anatomy of the Proximal End of the Femur
The femur is divided into a proximal (upper) end, a shaft, and a distal (lower) end. The proximal end consists of the head, neck, and trochanters. The head is spherical and articulates with the acetabulum to form the hip joint. It contains a small central depression known as the fovea capitis, or fovea of head, where the ligamentum teres femoris (ligament of the head of the femur) attaches to connect the femur to the acetabulum. The neck is a constricted region connecting the head to the shaft, directed medially, upward, and slightly anteriorly. Two prominent projections, the trochanters, are found at the junction of the neck and shaft. The Greater Trochanter is a large projection on the lateral side, directed upward and laterally. The Lesser Trochanter is a smaller projection on the posteromedial aspect of the neck-shaft angle, directed medially. These two structures are connected by the intertrochanteric line on the anterior surface and the intertrochanteric crest on the posterior surface.