Generality
The femur is the bone that resides inside the thigh, that is the upper part of each lower limb.
Each portion has a particular anatomy and has some specific areas, which act as both a point of origin and an insertion point for muscles and ligaments.
The femur is essential for the distribution of body weight throughout the lower limb and for locomotion.
What is the femur
The femur is the only bone in the thigh . It belongs to the category of long bones and represents the longest bone in the human body.
The femur is an equal bone and serves as both a point of origin and an insertion zone for numerous muscles and ligaments.
Anatomy
Anatomy experts divide the femur into three main bone regions (or portions): the proximal end, the body, and the distal end.
Important note: meaning of medial and lateral
Medial and lateral are two terms with the opposite meaning. However, to fully understand what they mean, it is necessary to take a step back and review the concept of the sagittal plan.
Figure: the plans with which the anatomists dissect the human body. In the image, in particular, the sagittal plane is highlighted.
The sagittal plane, or median plane of symmetry, is the antero-posterior division of the body, a division from which two equal and symmetrical halves are derived: the right half and the left half. For example, from a sagittal plane of the head derive a half, which includes the right eye, the right ear, the right nasal nostril and so on, and a half, which includes the left eye, the left ear, the left nasal nostril etc.
Returning to the medial-lateral concepts, the word media indicates a relationship of proximity to the sagittal plane; while the word side indicates a relationship of distance from the sagittal plane.
All anatomical organs can be medial or lateral with respect to a reference point. A couple of examples clarify this statement:
First example. If the reference point is the eye, it is lateral to the nasal nostril of the same side, but medial to the ear.
Second example. If the reference point is the second toe, this element is lateral to the first toe (toe), but medial to all the others.
End? PROXIMAL
The proximal end of the femur is the bone portion closest to the trunk. Moreover, in the medical-anatomical language, the proximal term means "closer to the center of the body" or "closer to the point of origin" (NB: by convention, the point of origin of any bone departing from the trunk is the trunk itself).
The proximal end has a morphology that allows it to join perfectly with the acetabulum of the pelvis (the acetabulum is a concavity, similar to a bowl) and forms the articulation of the hip .
The relevant structural components of the proximal end are 6:
- The head : is the most proximal part of the femur. Projected in the medial direction, it has the appearance of a sphere, precisely a 2/3 sphere. It has a smooth surface and a small depression ( fovea capitis ), which serves as an insertion point for the round ligament. The round ligament is one of the most important ligaments of the hip joint: one of its heads is tied to the head of the femur and its other end to the acetabulum.
The acetabulum is a hollow of bone nature, located in the pelvis, whose role is to accommodate the head of the femur.
- The neck : is the short section of femoral bone that connects the head to the body of the femur. With a very similar appearance to a cylinder, it is slightly bent in a medial direction: this fold, in the adult human being, forms an angle of about 130 ° with the neck.
The angle in question is particularly important, as it allows the hip joint to enjoy a considerable range of movement.
- The great trochanter : it is a bone process (or bone projection) that originates from the body and is placed laterally, with respect to the neck. It has a quadrangular shape and a particular anatomy, which allows it to accommodate the terminal heads of numerous muscles involved in the movement of the hip and thigh (piriformis muscle, external obturator muscle, internal obturator muscle, twin muscles, small gluteal muscle and muscle buttock medium).
The great trochanter is palpable: the reader can appreciate its presence by touch, touching the upper-external side of one of its two thighs.
- The small trochanter : is a bone process smaller than the large trochanter, which originates on the body of the femur, in an area with posterior-lateral positioning. With a squat conical shape, it protrudes just below the neck and has an orientation opposite to that of the great trochanter (thus "pointing" inwards, that is, in a medial direction).
The small trochanter serves as an insertion point for the terminal portions of the tendons of the large psoas and iliac muscles (which combined together are called ileo-psoas).
- The anterior intertrochanteric line : located on the anterior surface of the femur, it is a bone crest with infero-medial orientation (ie it goes downwards and inwards), which joins the two large trochanters together.
The anterior intertrochanteric line represents the insertion point for the iliofemoral ligament, one of the most important and resistant ligaments of the hip joint.
- The posterior intertrochanteric crest : located on the posterior surface of the femur, it is a bone crest with infero-medial orientation, which connects the two trochanters together.
Along its short path, it has a rounded tubercle, called a square tubercle, which houses the terminal head of the square muscle of the femur.
For a precise description of the two trochanters and other structures of the proximal end of the femur, readers are advised to consult the article on this page.
Figure: Posterior view of the upper extremity of the femur.
BODY OF THE FEMORE
The body is the central region of the femur, between the proximal end and the distal end.
It has an appearance similar to an hourglass: wide in the peripheral areas and narrow in the center.
Its posterior surface has a particular anatomy: in the middle, there is a bone crest with a longitudinal orientation - the so-called sour line - which bifurcates both above (therefore towards the proximal end) and inferiorly (therefore towards the distal end).
- The rough line welcomes the terminal ends of the long adductor muscles, short adductor and large adductor. Furthermore, it represents the point from which the biceps femoris, vastus lateralis and vastus medialis originate.
- The upper bifurcation forms a medial crest and a lateral crest. The medial crest is called the pectine line, while the lateral crest is called gluteal tuberosity .
The pettinea line welcomes the terminal head of the pectineus muscle; the gluteal tuberosity, on the other hand, serves as a point of attachment for the terminal head of the large gluteal muscle.
- The lower bifurcation forms (also) a medial crest and a lateral crest. The medial crest is the so-called medial supracondylar line, while the lateral crest is the so-called lateral supracondylar line .
The medial supracondylar line terminates its path with a small protuberance, called adductor tubercle . The adductor tuberculum represents, together with the rough line, the insertion point for the terminal head of the large adductor muscle.
Figure: inside the thigh, the femur runs slightly obliquely, with a medial orientation. This guarantees greater stability to the knee joint.
Looking from top to bottom, the femur has a medial pattern, ie it tends to develop in the direction of the sagittal plane. This feature is not random: it provides greater stability to the joint that the femur forms with the tibia; articulation that takes the name of knee .
End? DISTAL
The distal end of the femur is the bone portion furthest from the trunk. Moreover, in medical-anatomical language, the distal term is in antithesis with the word proximal and means "farther from the center of the body" or "farther from the point of origin".
The distal end is wider than the proximal end, has a cuboid shape and has some peculiarities that allow it to articulate perfectly with the tibia and the patella and form the knee joint.
The tibia is one of the two bones which, together with the fibula, constitutes the leg ; the patella, on the other hand, is the bony element, with the appearance of a shell, which resides in the front part of the knee, to protect the latter.
The anatomical structures that distinguish the femur are:
- The medial condyle and the lateral condyle . They are two oblong and rounded prominences, which are located at the end of the femur. Their postero-inferior surface is articulated with the tibia and the medial and lateral meniscus of the knee, while their anterior surface articulates with the patella. Among these structures there is a physical proximity.
Anteriorly, to separate the two condyles, there is a slight depression that takes the name of patellar surface . The patellar surface is smooth and has a fundamental role in the femur-patella articulation.
Special feature: the medial condyle is slightly longer than the lateral condyle. This means that, despite the medial orientation of the femur, the lower edge of the distal end is still horizontal.
- The medial epicondyle and the lateral epicondyle . There are two bony eminences, respectively, of the medial condyle and the lateral condyle, located above the latter (NB: the prefix epi- means "above"). They participate in the knee joint in a different way compared to the condyles: they act as an attachment point for the initial head of the medial collateral ligament (medial epicondyle) and of the lateral collateral ligament (lateral epicondyle). The medial and lateral collateral ligaments are essential to provide stability to the knee and allow the latter a wide range of movements, without the distal end of the femur touching the proximal end of the tibia.
- The intercondylar pit . It is the depression that separates the two condyles on the posterior surface of the femur (NB: the prefix inter- means "between"). It serves as an insertion point for the initial ends of the internal ligaments of the knee: the anterior cruciate ligament and the posterior cruciate ligament.
- The face for attaching the anterior cruciate ligament . It is an area of the intercondylar fossa, situated in a lateral position. On it, the anterior cruciate ligament (ACL) is inserted, a fundamental structure for the knee joint. LCA rupture severely limits the range of joint movement and promotes the knee arthrosis process.
- The face for attaching the posterior cruciate ligament . It is an area of the intercondylar fossa larger than the previous one, with medial localization. It serves as an attachment point for the posterior cruciate ligament (PCL), another important joint element of the knee.
Functions
The femur is a fundamental bone for the equitable distribution of forces and body weight on the lower limb and for locomotion (the muscles that engage are essential for walking, running and jumping).
The table below lists the 22 muscles that originate or end at the femur.
| Muscle | Head end or initial leader | Contact site on the femur |
| Iliac muscle | Head end | Small trochanter |
| Big muscle psoas | Head end | Small trochanter |
| Large gluteal muscle | Head end | Glutea tuberosity |
| Gluteus muscle average | Head end | Lateral surface of the great trochanter |
| Gluteus small muscle | Head end | Front of the great trochanter |
| Piriformis muscle | Head end | Upper margin of the great trochanter |
| Upper twin muscle | Head end | Great trochanter |
| Internal shutter muscle | Head end | Medial surface of the large trochanter |
| Lower twin muscle | Head end | Great trochanter |
| Femoral square muscle | Head end | Posterior intertrochanteric crest |
| External shutter muscle | Head end | Trochanteric fossa (small depression near the great trochanter; see the figure of the great trochanter). |
| Pectineus muscle | Head end | Combi line |
| Long adductor muscle | Head end | Medial part of the rough line |
| Short adductor muscle | Head end | Medial part of the rough line |
| Adductor large muscle | Head end | Medial part of the asphalt line and adductor tubercle |
| Lateral broad muscle | Initial leader | Large trochanter and lateral part of the harsh line |
| Intermediate broad muscle | Initial leader | Frontal and lateral surface of the femur |
| Medial vast muscle | Initial leader | Distal section of the intertrochanteric line and medial part of the asphalt line |
| Hamstring | Initial leader | Lateral part of the rough line |
| Popliteus muscle | Initial leader | Under the lateral epicondyle |
| Gastrocnemius muscle | Initial leader | Behind the adductor tubercle, above the lateral epicondyle. |
| Plantar muscle | Initial leader | Above the lateral condyle |
Diseases of the Femur
The most important problems that can affect the femur are the fractures of the bone sections that constitute it, in this case: the fracture of the proximal end and the fracture of the body.
FRACTURES OF EXTREMITY? PROSSIMALE DEL FEMORE
Fractures of the proximal end of the femur have a high mortality. In fact, about 1/3 of the patients die within a year of breaking the thigh bone.
There are two different types of proximal end fractures: intracapsular femoral fractures and extracapsular femoral fractures .
In intracapsular fractures, bone rupture involves the femoral head, that is the portion that fits into the acetabulum and forms the so-called joint capsule (NB: intracapsular means "inside the capsule").
In extracapsular fractures, bone breakage involves a proximal portion not involved in the hip joint.
While intracapsular fractures are typical of the elderly, extracapsular fractures are more common in young subjects.
FRACTURES OF THE BODY OF THE FEMORE
Fractures of the body of the femur are uncommon because, to provoke them, strong traumas are required, which occur only in rare circumstances (for example, a particularly violent car accident).
Two particular complications of these fractures are: the paralysis of the femoral nerve and the shortening of the leg (NB: this complication is typical of fractures of the femoral body defined as "spiral").
