FEMUR

 

The femur or the thigh bone is the only bone in thigh. It is the longest, heaviest and the strongest human bone. The name of the bone is derived from the Latin word ‘femur’ meaning ‘thigh’. The proximal end of the femur fits into the socket in the pelvis called as hip joint, and the bottom of the femur connects to the tibia and patella to form the knee joint.

The femur length on an average is 26.74% of an individual height.

The proximal end has a pyramid shaped neck attaches the spherical head at the top and the cylindrical shaft at the bottom. There are two prominent bony protrusions, greater and lesser trochanter which attaches muscles that helps in the motion of both hip and knee joints. The angle between neck of the femur and the shaft is known as the inclination angle which is about 128 degrees in an average adult which decreases with the age. In general population without any severe tibiofemoral deformities, the femoral-tibial angle is almost about 175 degrees.

The head of the femur is directed medially upwards and slightly forwards. The shaft is directed obliquely downwards and medially so that the lower surfaces of the two femoral condyles lie in the same horizontal plane.

The femoral length is associated with a striding gait, strength, weight and muscular forces it is required to withstand. The femur supports all the body weight while standing or doing other activities like running, walking, jumping, etc., stability of the gait and is an essential component of the lower kinetic chain. The weight of the upper body rests on the femoral heads. The degree of the femoral obliquity varies between individuals but is greater in women than in men.

The femur is divided into three parts: Proximal, Shaft and Distal.

PROXIMAL FEMUR

The proximal femur contains head, neck, greater trochanter, lesser trochanter, Intertrochanteric line and intertrochanteric crest.

FEMORAL HEAD

It faces antero-supero-medially to articulate with the acetabulum. The head is of a spheroidal shape. Its smoothness is interrupted posteroinferior to its centre by a small, rough fovea which is an ovoid depression. The fovea is connected through the round ligament to the sides of the acetabular notch known as the ligamentum teres. The head of femur articulates with the acetabulum to form a ball and socket joint known as hip joint. The femoral head is intracapsular and is encircled distal to its middle line by the acetabular labrum. The articular margin is distinct except anteriorly, where the articular surface extends to the femoral neck.

NECK

The femoral head narrows considerably to form a cylindrical neck that connects the head with the shaft with an average angle of 127 degrees also known as angle of inclination or neck-shaft angle. The neck is almost 4-5 cm long. The angle of inclination provides movement at the hip joint, allows the limb to swing and also provides a lever for the action of the muscles at the hip joint. The angle is widest at the birth and diminishes gradually until the age of 10 years and is smaller in the females due to wider pelvis. It is strengthened by a thickening of bone called calcar femorale present along the concavity. The neck is laterally rotated with respect to the angle of anteversion which is almost 10-15° and this varies from person to person. The neck is rounded, upper surface is almost horizontal and slightly concave, while the lower surface is straighter, oblique, directed inferolaterally and backwards to the shaft near the lesser trochanter.

The neck has 2 borders and 2 surfaces. The upper border is concave and horizontal which meets the shaft at the greater trochanter. The lower border is straight and oblique which meets the shaft near the lesser trochanter. The anterior surface is flat and meets the shaft at the intertrochanteric line, which is entirely intracapsular. The posterior surface is convex from above downwards and concave from side to side and meets the shaft at the intertrochanteric crest.

GREATER TROCHANTER

The greater trochanter is large, irregular, box shaped apophysis present laterally and posteriorly and is the most lateral prominent of the femur. The highest point of the greater trochanter is higher than the neck of the femur and it reaches the midpoint of the femur. It can be palpated very easily. It has an upper border with an apex which is inturned posterior part of the posterior border. The greater trochanter also has three surfaces: Anterior, Medial and Lateral. The anterior border is rough in the lateral part. The medial surface has a rough impression above and a deep trochanteric fossa below which presents a tubercle. The lateral surface is crossed by an oblique ridge directed downwards and forwards, it is palpable when muscles are relaxed.

LESSER TROCHANTER

The lesser trochanter is a cone shaped extension of the lowest part of the femoral neck. It is smaller than the greater trochanter. It projects from the postero-medial side of the femur. The lesser trochanter is not palpable.

INTERTROCHANTERIC LINE

The intertrochanteric line is a prominent ridge at the junction of the anterior surface of the neck and shaft which descends medially from a tubercle on the upper part of the anterior aspect of the greater trochanter to a point on the lower border of the neck and anteriorly to the lesser tubercle. Distally this line is known as the pectineal line which serves as the anterior attachment of the hip joint capsule.

INTERTROCHANTERIC CREST

The intertrochanteric crest marks as a junction of the posterior surface of the neck with shaft of femur. It is a smooth rounded ridge, which starts above at the posterosuperior angle of the greater trochanter and ends at the lesser trochanter. The rounded elevation, a little above its middle is called as the quadrate tubercle (linea quadrata) which is almost 5cm in length.

SHAFT

The shaft or the body of the femur is large, thick and almost cylindrical in form. It is little broader above than in the center, widest and somewhat flattened from before backward below. It is slightly arched hence it is convex in anterior side and concave in posterior side, where it is strengthened by a prominent longitudinal ridge known as linea aspera which divides proximally and distal as the medial and lateral ridge.

In the upper 1/3^rd of the shaft, two lips of linea aspera diverge to enclose an additional posterior surface. It has 4 borders: Medial, Lateral, Spiral line and Lateral lip of the gluteal tuberosity. It also has 4 surfaces: Anterior, Medial, Lateral and Posterior. The gluteal tuberosity is a broad roughened ridge on the lateral part of the posterior surface.

In the middle 1/3^rd shaft has 3 borders: Medial, Lateral and Posterior & 3 surfaces: Anterior, Medial and Lateral. The medial and lateral borders are rounded and ill-defined, but the posterior border is in the roughened ridge as linea aspera. The medial and lateral surfaces are directed more backwards than towards the sides. Its subjacent compact bone is augmented to withstand compressive forces which are concentrated here by the anterior curvature of the shaft. Nutrient foramina, directed proximally, appear in the linea aspera, varying in number and site, one usually near its proximal end, a second usually near its distal end.

In the lower 1/3^rd of the shaft the two lips of linea aspera diverge as supracondylar lines to accommodate popliteal surface. This part of the shaft also has 4 surfaces: Anterior, Medial, Lateral and Popliteal. Anterior surface is smooth and convex for most of the part. The upper portion of this surface has a roughened area called the patellar fossa. Posterior surface also known as popliteal surface is smooth and concave throughout most of its length. The linea aspera extends upwards from the upper two-thirds of the posterior surface and ends just above the condyles. Medial surface is relatively flat and smooth. Contains the adductor tubercle, a roughened area near the upper part of this surface for attachment of the adductor muscles, which pull the thigh towards the midline. The medial condyle, a rounded bony prominence, forms the lower part of the medial surface. Lateral surface is convex and smoother than the medial surface. The lateral condyle, a rounded bony prominence, forms the lower part of the lateral surface.

DISTAL END

The distal end of the femur is cuboid in form and widely expanded as a bearing surface for the transmission of the weight to the tibia. It has 2 condyles, medial and lateral. Anteriorly, the condyles are merging and continues into the shaft. The condyles are slightly prominent and are separated by a smooth shallow articular depression called patellar surface. Posteriorly, the condyles are separated by a deep intercondylar fossa or intercondylar notch and project beyond the plane of the popliteal surface. The distal end articulates with tibia and patella which forms the knee joint. The articular surface for knee joint is a broad area like an inverted U shape and has 2 surfaces, Tibial and Patellar.

PATELLAR SURFACE

The patellar surface extends anteriorly on both the condyles, especially the lateral then medial. It is transversely concave, vertically convex and grooved for the posterior patellar surface. The anterior border is therefore oblique and runs distally and medially, separated from the tibial surfaces by two small grooves that crosses the condyles obliquely. The lateral groove runs laterally and bit forwards from the front of the intercondylar fossa and expands to form a small triangular depression which rests on the anterior edge of the lateral meniscus when the knee is fully extended. The medial groove is restricted to the medial part of the medial condyle and rests on the anterior edge of the medial meniscus in full knee extension.

TIBIAL SURFACE

The tibial surface is divided by the intercondylar fossa but is anteriorly continuous with the patellar surface and is convex in all the directions. The medial part of the tibial surface is a broad strip on the convex infero-posterior surface of the medial condyle and is gently curved with a medial convexity. The lateral part of the tibial surface is broader and passes slightly back. Both the medial and lateral surfaces have dis-similar antero-posterior curvatures.

MEDIAL CONDYLE

The medial condyle is longer and when femur is held with its body perpendicular projects to a lower level. The condyle is convex medially, has a bulging and is easily palpable. Posterosuperior to the epicondyle there is projection known as the adductor tubercle. This tubercle is an important landmark as an epiphyseal line for the lower end of the femur passes through it. The lateral surface of the condyle is the medial wall of the intercondylar fossa. A curved strip which is 1cm wide and adjoining the medial articular margin, is covered by the synovial membrane and is inside the joint capsule.

LATERAL CONDYLE

The lateral condyle is more prominent and is broader both in its antero-posterior and transverse diameters. The condyle is thicker, stronger and flat laterally and is more in the line of the shaft of femur hence it takes greater part in the transmission of the body weight to the tibia. the popliteal grove just below the epicondyle has a deeper anterior part and a shallower posterior part.

INTERCONDYLAR FOSSA OR NOTCH

The intercondylar fossa separates both the condyles distally and behind. The fossa is intracapsular but moreover extracapsular. The distal border of the patellar surface limits the fossa in front and at back intercondylar line limits the fossa separating from the popliteal surface. Its lateral wall, the medial surface of the lateral condyle, bears a flat posterosuperior impression that spreads to the floor of the fossa near the intercondylar line for the proximal attachment of the anterior cruciate ligament. The medial wall of the fossa, i.e. the lateral surface of the medial condyle, bears a similar larger area, but far more anteriorly, for the proximal attachment of the posterior cruciate ligament. Both impressions are smooth and largely devoid of vascular foramina, whereas the rest of the fossa is rough and pitted by vascular foramina. A bursal recess between the ligaments may ascend to the fossa. The capsular ligament and, laterally, the oblique popliteal ligament are attached to the intercondylar line. The infrapatellar synovial fold is attached to the anterior border of the fossa.

Attachments on the Femur

1. Fovea: Attachment for ligamentum teres.
2. Greater Trochanter:
• Piriformis at apex.
• Gluteus minimus on anterior surface.
• Obturator internus and gemelli on medial surface.
• Obturator externus in trochanteric fossa.
• Gluteus medius on lateral surface; trochanteric bursa behind it.
3. Lesser Trochanter:
• Psoas major on apex and anterior surface.
• Iliacus on base and below.
• Bursa covers posterior surface.
4. Intertrochanteric Line:
• Capsular ligament attachment.
• Iliofemoral ligament upper and lower bands.
• Vastus lateralis and medialis origin from ends of the line.
5. Quadrate Tubercle: Quadratus femoris insertion.
6. Shaft:
• Medial head of gastrocnemius on popliteal surface.
• Vastus intermedius from anterior and lateral surfaces.
• Articularis genu below vastus intermedius.
• Suprapatellar bursa related to lower anterior surface.
• Vastus lateralis from greater trochanter and linea aspera.
• Vastus medialis from intertrochanteric line and linea aspera.
• Gluteus maximus, adductors, and pectineus insertions detailed along linea aspera.
7. Lateral Condyle:
• Fibular collateral ligament attachment.
• Popliteus origin in popliteal groove.
8. Medial Condyle:
• Tibial collateral ligament attachment.
• Adductor tubercle receives adductor magnus insertion.
9. Intercondylar Notch:
• Cruciate ligaments attached to condyles.
• Capsular and oblique popliteal ligament attachments.

Nutrient Artery: From second perforating artery, enters via foramen on linea aspera.

This summary maintains the original description’s essence while being more concise for easier reference.

BLOOD SUPPLY

1. Deep Femoral Artery: Supplies blood to the shaft and distal portion of the femur.

2. Medial and Lateral Circumflex Femoral Arteries: Supplies blood to the head and neck of the bone.

3. Obturator Artery: Supplies blood to the femoral head.

4. Foveal Artery: Supplies blood to the femoral head.

 

OSSIFICATION

The femur, the long bone in your thigh, has distinct growth regions at its ends called epiphyses. These epiphyses are capped with cartilage and separated from the main shaft (diaphysis) by growth plates (physes). Understanding these regions is important for various reasons, including bone development, forensic analysis, and proper imaging techniques.

Structure and Fusion:

• Upper end: There are three epiphyses at the top of the femur:
• The head (capital epiphysis) forms the ball-shaped joint with the hip socket.
• The greater trochanter, a large bony prominence for muscle attachment.
• The lesser trochanter, a smaller ridge on the posterior aspect.
• Lower end: A single epiphysis exists at the lower end of the femur.

These fuse with the shaft at different times: * Upper epiphyses (lesser trochanter, greater trochanter, head): Fuse around 18 years old. * Lower epiphysis: Fuses around 20 years old.

Ossification and Forensic Importance:

The presence of an ossification center (bone formation starting point) in the lower femoral epiphysis of a newborn found dead indicates the child was viable, meaning it could have survived independently outside the womb.

Growth and Development:

• The lower end of the femur is the primary growth region during childhood and adolescence.
• The lower epiphyseal line (growth plate) interestingly passes through the adductor tubercle, a bony bump for muscle attachment.
• In contrast, the upper head epiphysis is entirely cartilaginous in infants and not visible on standard X-rays. Ultrasound is preferred for early visualization.
• The growth plate of the head starts ossifying around 10 years old. Initially, it has a horizontal orientation, incorporating the inferomedial part of the articular surface (joint surface) into the neck region.
• Over time, the medial part of the epiphysis grows down, covering this previously neck-related articular surface. This process transforms the head into a hollow cup shape sitting atop the femoral neck.
• Notably, the epiphyseal line of the head generally follows the articular margin, except for a superior non-articular area allowing blood vessel passage into the head.

Fusion Timeline:

• Lesser trochanter: Fuses shortly after puberty.
• Greater trochanter: Fuses after the lesser trochanter.
• Capital epiphysis (head): Fuses around 14 years in females and 17 years in males.
• Distal epiphysis (lower end): Fuses around 16 years in females and 18 years in males.
• Distal epiphyseal plate: Notably, this growth plate runs through the adductor tubercle.

Ossification Process:

The femur has one primary ossification center in the shaft that appears between the 5th and 7th week of fetal development. Secondary ossification centers then emerge at different times:

• Distal end: 9th month of fetal development
• Head: 6th month after birth
• Greater trochanter: 4th year
• Lesser trochanter: 12th to 14th years

 

HAND PHALANGES

The phalanges are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones.

Each proximal phalanx consists of three parts:

• The base, which represents the expanded proximal part. It has a concave, oval-shaped articular facet that articulates with the metacarpal head to form the metacarpophalangeal (MCP) joint. The base also contains nonarticular tubercles for the attachment of various soft tissue structures.
• The body, which continues distally from the base. It tapers distally and has two surfaces: dorsal and palmar. The dorsal surface is round and smooth, appearing convex in the transverse plane. The palmar surface is flat and rough, especially on the sides where the flexor fibrous sheaths of digits attach. The surface appears flat in the transverse plane but concave in the sagittal plane.
• The head, which represents the expanded and rounded distal part. It has a pulley-shaped articular surface that articulates with the base of the middle phalanx to form the proximal interphalangeal (PIP) joint. The heads consist of smooth grooves, especially on the palmar aspects. These grooves represent the attachment points of the collateral interphalangeal ligaments of hand.

Various ligaments attach to the proximal phalanges. The most complex one is the digital fascial complex which attaches the surrounding subcutaneous tissue and neurovasculature to the bony phalanges. The collateral and palmar metacarpophalangeal ligaments attach to the bases of the proximal phalanges. They provide strength to the metacarpophalangeal joints. The collateral interphalangeal ligaments of hand attach to the heads, supporting the PIP joints. The proximal phalanges are also covered by the extensor expansion of hand on the dorsal aspect.

The proximal phalanges are very mobile at the MCP joints. They are mainly capable of flexion, extension, adduction and abduction. Circumduction and rotation are also possible, especially at the MCP joint of the thumb. These movements are enabled by the action of several muscles:

• Posterior (extensor) forearm muscles, such as extensor digitorum, extensor pollicis brevis, extensor digiti minimi and extensor indicis.
• Metacarpal muscles, such as the lumbricals, palmar interossei and dorsal interossei.
• Thenar muscles, for example flexor pollicis brevis and adductor pollicis.
• Hypothenar muscles like abductor digiti minimi and flexor digiti minimi.

These muscles carry out their functions via their direct attachments to the bases of the proximal phalanges. In addition, many extensors carry out the movements via the extensor expansion of hand which covers the phalanges

Middle phalanges

There are four middle (intermediate) phalanges in each hand because the thumb is missing one. They have a similar structure to the proximal ones, consisting of a base, body and head. The base of each middle phalanx has two concave-shaped articular facets and matches the head of the corresponding proximal phalanx. Their apposition forms the PIP joint. The heads of the middle phalanges have a pulley-like appearance. They articulate with the bases of the distal phalanges to form the distal interphalangeal (DIP) joints of hand.

The middle phalanges are reinforced by the same ligaments supporting the proximal ones, digital fascial complex, collateral interphalangeal ligaments and extensor expansion of hand. The collateral interphalangeal ligaments attach to the base and heads of the middle phalanges to reinforce the PIP and DIP joints.

The middle phalanges are less mobile compared to the proximal phalanges. They are only capable of flexion and extension at the PIP joints. Only the flexor digitorum superficialis muscle attaches directly to the sides of the middle phalanges, flexing them at the PIP joints. The remaining contributions are provided by the action of the previously mentioned muscles; the forearm extensors, metacarpal, thenar and hypothenar muscle groups. Flexion and extension are transferred to the middle phalanges from the direct action of these muscles on the proximal phalanges or via the extensor expansion of hand.

Distal phalanges

Each hand has five distal phalanges, which look shorter and slightly thicker compared to the previous two sets. Each distal phalanx has a base, body and head. The base has a double articular facet which matches the shape of the head of the middle phalanx. The distal phalanges have a smooth and round dorsal surface. In contrast, their palmar surface is wrinkled and irregular. The nonarticular heads contain an irregular, curved shaped distal tuberosity. It serves as an anchor point for the pulps of the digits.

The distal phalanges are stabilized by the digital fascial complex, collateral interphalangeal ligaments and extensor expansion of hand. The collateral interphalangeal ligaments attach to the base of the distal phalanges to reinforce the DIP joints.

The distal phalanges are capable of flexion and extension at the DIP joints. Two forearm extensors and one flexor muscle insert directly into the bases of the distal phalanges, permitting these actions. These include flexor digitorum profundus, flexor pollicis longus and extensor pollicis longus. The previously mentioned muscle groups acting on the proximal and middle phalanges also act indirectly on the distal ones via the extensor expansion of hand.

BLOOD SUPPLY

The hand phalanges are richly supplied with blood, lymphatics, and nerves, and their development involves a precise pattern of ossification. The blood supply to the phalanges comes primarily from the digital arteries, which are branches of the superficial and deep palmar arches derived from the radial and ulnar arteries. These arteries run alongside the phalanges, especially near the lateral aspects, where they give off perforating branches that penetrate the bone through nutrient foramina. Venous drainage mirrors the arterial supply, with the digital veins draining into the superficial and deep venous systems of the hand. The lymphatic drainage follows the venous pathways, with lymphatic vessels accompanying the digital veins. These vessels drain into the epitrochlear and axillary lymph nodes, playing a crucial role in immune surveillance and fluid balance in the hand.

NERVOUS SUPPLY

The nervous supply of the phalanges is derived from the median, ulnar, and radial nerves, which innervate the hand based on their anatomical distribution. The median nerve supplies the palmar side of the first three and a half fingers and their corresponding phalanges, while the ulnar nerve supplies the remaining fingers. The radial nerve provides sensation to the dorsal aspect of the phalanges, primarily for the proximal portions of the first three fingers. These nerves are responsible for transmitting sensory information, including pain, touch, and temperature, and they also play a critical role in motor function by innervating the muscles controlling finger movement.

OSSIFICATION

Ossification of the hand phalanges follows a well-defined sequence. Each phalanx typically ossifies from one primary ossification center, which appears during fetal development, generally between the 8th and 12th weeks of gestation. A secondary ossification center forms at the base of the phalanx during early childhood, usually between 2 and 4 years of age, depending on the specific phalanx and its position in the hand. The fusion of the primary and secondary ossification centers, marking skeletal maturity, occurs by 15–18 years of age. The ossification sequence begins with the proximal phalanges, followed by the middle and distal phalanges. This progression is vital for assessing growth and development in pediatric radiology and clinical evaluations.

ULNA

The ulna is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. It runs parallel to the radius, the other long bone in the forearm. The ulna is usually slightly longer than the radius, but the radius is thicker.

The ulna has a bony process, the olecranon process, a hook-like structure that fits into the olecranon fossa of the humerus. This prevents hyperextension and forms a hinge joint with the trochlea of the humerus. There is also a radial notch for the head of the radius, and the ulnar tuberosity to which muscles attach.

The long, narrow medullary cavity of the ulna is enclosed in a strong wall of cortical tissue which is thickest along the interosseous border and dorsal surface. At the extremities the compact layer thins. The compact layer is continued onto the back of the olecranon as a plate of close spongy bone with lamella parallel. From the inner surface of this plate and the compact layer below its trabecula arch forward toward the olecranon and coronoid and cross other trabecula, passing backward over the medullary cavity from the upper part of the shaft below the coronoid. Below the coronoid process there is a small area of compact bone from which trabecula curve upward to end obliquely to the surface of the semilunar notch which is coated with a thin layer of compact bone. The trabecula at the lower end has a more longitudinal direction.

The ulna has an upper end, shaft and a lower end.

GENERAL FEATURES

Upper End

It presents the olecranon and coronoid processes and the trochlear and radial notches.

1. Olecranon process projects upwards from the shaft. It has 5 surfaces. Anterior surface is articular which forms the upper part of the trochlear notch. Posterior surface forms a triangular subcutaneous area which is separated from the skin by bursa. Inferiorly it is continuous with the posterior border of the shaft of the ulna and upper part forms the point of the elbow. Medial surface is continuous inferiorly with the medial surface of the shaft. Lateral surface is smooth and Superior surface in its posterior part shows a roughened area.

2. Coronoid process projects forwards from the shaft just below the olecranon and has 4 surfaces. Superior surface forms the lower part of the trochlear notch. Anterior surface is triangular and rough & its lower corner forms the ulnar tuberosity. Lateral surface upper part is marked by radial notch for the head the radius. Annular ligament is attached to the anterior and posterior margins of the notch. Lower part forms a depressed area to accommodate the radial tuberosity. It is limited behind by a ridge called supinator crest. Medial surface is continuous with the medial surface of the shaft.

3. Trochlear notch forms an articular surface which articulates with trochlea of the humerus to form the elbow joint.

4. Radial notch articulates with the head of the radius to form the superior radioulnar joint.

Shaft

The shaft of the Ulna at its upper part is prismatic in form and curved so as to be convex behind and lateralward; its central part is straight; its lower part is rounded, smooth, and bent a little lateralward. It tapers gradually from above downward and has three borders and three surfaces.

Borders

1.The interosseous or lateral border is sharpest in its middle two-fourths. Inferiorly, it can be traced to the lateral side of the head. Superiorly, it is continuous with the supinator crest.

2.The anterior border is thick and rounded. It begins above on the medial side of the ulnar tuberosity, passes backwards in its lower one-third, and terminates at the medial side of the styloid process.

3.The posterior border is subcutaneous. It begins, above, at the apex of the triangular subcutaneous area at the back of the olecranon and terminates at the base of the styloid process.

Surfaces

1.The anterior surface lies between the anterior and interosseous borders. A nutrient foramen is seen on the upper part of this surface. It is directed upwards. The nutrient artery is derived from the anterior interosseous artery.

2.The medial surface lies between the anterior and posterior borders.

3.The posterior surface lies between the posterior and interosseous borders. It is subdivided into three areas by two lines. An oblique line divides it into upper and lower parts. The lower part is further divided by a vertical line into a medial and a lateral area.

Lower End 

The lower end of the ulna presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the triangular articular disc which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the ulnar notch of the radius.

Near the wrist, the ulnar, with two eminences; the lateral and larger is a rounded, articular eminence, termed the head of the ulna; the medial, narrower and more projecting, is a non-articular eminence, the styloid process.

The head presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the triangular articular disk which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the ulnar notch of the radius. 

The styloid process projects from the medial and back part of the bone; it descends a little lower than the head, and its rounded end affords attachment to the ulnar collateral ligament of the wrist joint.

The head is separated from the styloid process by a depression for the attachment of the apex of the triangular articular disk, and behind, by a shallow groove for the tendon of the extensor carpi ulnaris.

PARTICULAR FEATURES:

MUSCLES

The ulna serves as the attachment site for numerous muscles with a myriad of actions. The following are organized in terms of the direction and where on the ulna is the attachment of the muscle’s fibers.

The following muscles insert into the ulna:

Triceps brachii – posterior section of the superior surface of the olecranon Anconeus – olecranon Brachialis – the volar surface of the coronoid process

The following muscles originate from the ulna:

• Pronator teres – the medial surface of the coronoid process
• Flexor carpi ulnaris – olecranon process
• Flexor digitorum superficialis – coronoid process
• Flexor digitorum profundus – anteromedial surface
• Pronator quadratus – distal anterior shaft
• Extensor carpi ulnaris – posterior border
• Supinator – proximal ulna
• Abductor pollicis longus – posterior surface
• Extensor pollicis longus – dorsal shaft
• Extensor indicis – posterior distal shaft
  

Blood vessels and Lymphatics

The main blood supply of the ulna originates from the ulnar artery or the ulnar recurrent artery. The ulnar artery then branches into a common interosseous artery that then further subdivides into the posterior and anterior interosseous vessels. These vessels are vital for the nutrients of the ulnar diaphysis. The ulnar metaphysis is supplied by the end branches of the anterior interosseous artery, while the head of the ulna receives its supply from small divisions off of the ulnar artery proper.

The lymphatics of the ulna drain either to the supratrochlear lymph node or directly travel to the adjacent cluster of axillary lymph nodes.

Nerves

Three main nerves run in the forearm in the proximity of the ulna: the median, ulnar, and radial nerves. The median nerve runs anterolaterally and innervates the muscles responsible for flexion of the wrist and the fingers (digits 1 to 3 and radial aspect of the fourth). The ulnar nerve is positioned more anteromedially, running in between the flexor digitorum superficialis and flexor digitorum profundus. This nerve is also involved in flexion of the wrist and fingers (the ulnar aspect of 4th and all of the 5th) but also is responsible for spanning the fingers. A major branch of the median nerve is the anterior interosseous nerve. Impingement or entrapment of the anterior interosseous nerve results in the characteristic clinical finding of weakness related to the "pincer" movement. The radial nerve extends posteriorly to the ulna and the radius and is the sole nerve involved in the muscles responsible for extension of the forearm, wrist, and fingers.  The posterior interosseous nerve is a branch of the radial nerve with both motor and sensory functions. Posterior interosseous nerve impingement or entrapment occurs in the region of the radial tunnel resulting in weakness related to the extension of the digits.

EMBRYOLOGY AND OSSIFICATION

The ulna develops from the induction of the lateral plate mesoderm. From this, it differentiates into the somatic mesoderm, which, in turn, gives rise to all of the bones, ligaments, connective tissue, and blood vessels of the extremities. Endochondral ossification allows for the induction of bone from previously laid hyaline cartilage. The ulna itself is ossified in three sections. First, it commences at the body of the ulna. Around week eight of gestation, the chondrocytes in the middle of the ulna lay down collagen and fibronectin to appropriately calcify the bone template. At the time of birth, the ends of the bone are still cartilaginous and not ossified. Around age four, an ossification center arises in the middle of the ulnar head and then encompasses into the styloid process. At age ten, a subsequent center appears in the olecranon, which is then met by the growth of the epiphysis at approximately age sixteen. The ossification centers about the elbow occur in a predictable order and understanding/knowledge of these stages of development is essential for identifying traumatic injuries about the elbow

CLAVICLE

The clavicle is a sigmoid-shaped long bone with a convex surface along its medial end when observed from cephalad position. It connects axial and appendicular skeleton. It supports shoulder so that arm can swing clearly away from the trunk. Clavicle transmits weight of the limb to the sternum. 

 It receives its name from the Latin clavicula ("little key"), because the bone rotates along its axis like a key when the shoulder is abducted. Clavicle has a shaft and two ends.

SHAFT

The shaft is further divided in lateral one-third & medial two-thirds. 

Lateral one-third: It is flattened from above downwards. It has 2 borders and 2 surfaces.

The anterior border is concave forwards which gives origin to Deltoid muscle and Posterior border is convex backwards which gives origin to Trapezius muscle.

The superior surface is subcutaneous and the inferior surface has a ridge called the trapezoid line and a tubercle; the conoid tubercle for attachment with the trapezoid and the conoid ligament, part of the coracoclavicular ligament that serves to connect the collarbone with the coracoid process of the scapula.

Medial two-thirds: It is rounded and said to have 4 surfaces. The Anterior is convex forwards, Posterior has smooth surface, Superior surface is rough in medial part and & Inferior surface has a rough oval impression at the medial end.The lateral half of this surface has a longitudinal subclavian groove in which nutrient foraman lies.

LATERAL END & MEDIAL END

The lateral end is also known as the acromial end. It is flat from above downward. It bears a facet that articulates with the shoulder to form the acromioclavicular joint. The area surrounding the joint gives an attachment to the joint capsule. The anterior border is concave forward and posterior border is convex backward.

It is also known as the sternal end. The medial end is quadrangular and articulates with the clavicular notch of the manubrium of the sternum to form the sternoclavicular joint. The articular surface extends to the inferior aspect for articulation with the first costal cartilage.

Right clavicle - Superior aspect

      Right Clavicle - Inferior aspect

SIDE DETERMINATION

The side to which a clavicle belongs can be determined from the following characters:

1. The lateral end is flat, and the medial end is large and quadrilateral.

2. The shaft is slightly curved, so that it is convex forwards in its medial two-thirds, and concave forwards in its lateral one-third.

3. The inferior surface is grooved longitudinally in its middle one-third.

SEX DETERMINATION

1. In females, the clavicle is shorter, lighter, thinner, smoother, and less curved than in males.

2. The midshaft circumference and the weight of the clavicle are reliable criteria for sexing the clavicle.

3. In females, the lateral end of the clavicle is a little below the medial end; in males, the lateral end is either at the same level or slightly higher than the medial end.

DEVELOPMENT AND OSSIFICATION

The collarbone is the first bone to begin the process of ossification (laying down of minerals onto a preformed matrix) during development of the embryo, during the fifth and sixth weeks of gestation. However, it is one of the last bones to finish ossification at about 21–25 years of age. Its lateral end is formed by intramembranous ossification while medially it is formed by endochondral ossification. It consists of a mass of cancellous bone surrounded by a compact bone shell. The cancellous bone forms via two ossification centres, one medial and one lateral, which fuse later on. The compact forms as the layer of fascia covering the bone stimulates the ossification of adjacent tissue. The resulting compact bone is known as a periosteal collar.

Even though it is classified as a long bone, the collarbone has no medullary (bone marrow) cavity like other long bones, though this is not always true. It is made up of spongy cancellous bone with a shell of compact bone. It is a dermal bone derived from elements originally attached to the skull.

MUSCLES AND LIGAMENTS ATTACHMENT

   1.At the lateral end the margin of the articular surface for the acromioclavicular joint gives attachment to the joint capsule.

   2.At the medial end the margin of the articular surface for the sternum gives attachment to:

(a) the fibrous capsule all round

(b) the articular disc posterosuperiorly

(c) the interclavicular ligament superiorly.

   3.Lateral one-third of shaft

(a)The anterior border gives origin to the deltoid.

(b)The posterior border provides insertion to the trapezius.

(c) The conoid tubercle and trapezoid ridge give attachment to the conoid and trapezoid parts of the coracoclavicular ligament.

   4. Medial two-thirds of the shaft

(a)The anterior surface gives origin to the pectoralis major.

(b)The rough superior surface gives origin to the clavicular head of the stemocleidomastoid.

(c)The oval impression on the inferior surface at the medial end gives attachment to the costoclavicular ligament.

(d)The subclavian groove gives insertion to the subclavius muscle. The margins of the groove give attachment to the clavipectoral fascia.

The nutrient foramen transmits a branch of the suprascapular artery.