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

 

ILIUM

 

The Ilium or the flank forms the upper extended plate-like part of the hip bone. It has upper and lower parts and three surfaces. The upper end is called the iliac crest which forms the two-fifths of the acetabulum and the lower end which is smaller than upper end is fused with pubis and ischium at the acetabulum. The upper part is much expanded, and has gluteal, sacropelvic and iliac (internal) surfaces. The posterolateral gluteal surface is an extensive rough area; the anteromedial iliac fossa is smooth and concave; and the sacropelvic surface is medial and posteroinferior to the fossa, from which it is separated by the medial border.

Ilium

Ilium

 

Iliac crest

The iliac crest is the superior border of the ilium. It is broad and convex upwards but sinuous from side to side, being internally concave in front and convex behind. Its ends project as anterior and posterior superior iliac spines. The anterior superior iliac spine is palpable at the lateral end of the inguinal fold; the lateral end of the inguinal ligament is attached to the anterior superior iliac spine. The posterior superior iliac spine is not palpable but is often indicated by a dimple, approximately 4 cm lateral to the second sacral spinous process, above the medial gluteal region.

The iliac crest has ventral and dorsal segments. The ventral segment occupies slightly more than the anterior two-thirds of the iliac crest. It has internal and external lips and a rough intermediate zone that is narrowest centrally. The dorsal segment, which occupies approximately the posterior 1/3^rd in humans. It has two sloping surfaces separated by a longitudinal ridge ending at the posterior superior spine. The tubercle of the iliac crest projects outwards from the outer lip approximately 5 cm posterosuperior to the anterior superior spine. The summit of the iliac crest, a little behind its midpoint, is level with the 4^th lumbar vertebral body in adults and with the 5^th lumbar vertebral body in children aged 10 years or less.

Anterior border

The anterior border descends to the acetabulum from the anterior superior spine. Superiorly it is concave forwards. Inferiorly, immediately above the acetabulum, is a rough anterior inferior iliac spine, which is divided indistinctly into an upper area for the straight head of rectus femoris and a lower area extending laterally along the upper acetabular margin to form a triangular impression for the proximal end of the iliofemoral ligament.

Posterior border

The posterior border is irregularly curved and descends from the posterior superior spine, at first forwards, with a posterior concavity forming a small notch. At the lower end of the notch is a wide, low projection known as the posterior inferior iliac spine. Here the border turns almost horizontally forwards for approximately 3 cm, then down and back to join the posterior ischial border. Together these borders form a deep notch, the greater sciatic notch, which is bounded above by the ilium and below by the ilium and ischium. The upper fibres of the sacrotuberous ligament are attached to the upper part of the posterior border. The superior rim of the notch is related to the superior gluteal vessels and nerve. The lower margin of the greater sciatic notch is covered by piriformis and is related to the sciatic nerve.

Medial border

The medial border separates the iliac fossa and the sacropelvic surface. It is indistinct near the crest, rough in its upper part, then sharp where it bounds an articular surface for the sacrum and finally rounded. The latter part is the arcuate line, which inferiorly reaches the posterior part of the iliopubic ramus, marking the union of the ilium and pubis.

• Gluteal surface

Gluteal surface is the outer surface of the ilium, which is convex in front and concave behind, like the iliac crest. It is rough and curved, convex in front, concave behind, and marked by three gluteal lines which divides into four areas. The posterior gluteal line is shortest, descending from the external lip of the crest approximately 5 cm in front of its posterior limit and ending in front of the posterior inferior iliac spine. Above, it is usually distinct, but inferiorly it is poorly defined and frequently absent. The anterior gluteal line, the longest, begins near the midpoint of the superior margin of the greater sciatic notch and ascends forwards into the outer lip of the crest, a little anterior to its tubercle. The inferior gluteal line, seldom well marked, begins posterosuperior to the anterior inferior iliac spine, curving posteroinferiorly to end near the apex of the greater sciatic notch. Between the inferior gluteal line and the acetabular margin is a rough, shallow groove. Behind the acetabulum, the lower gluteal surface is continuous with the posterior ischial surface.

The articular capsule is attached to an area adjoining the acetabular margin, most of which is covered by gluteus minimus. Posteroinferiorly, near the union of the ilium and ischium, the bone is related to piriformis.

• Iliac fossa

The iliac fossa, the internal concavity of the ilium, faces anterosuperiorly. It is limited above by the iliac crest, in front by the anterior border and behind by the medial border, separating it from the sacropelvic surface. It forms the smooth and gently concave posterolateral wall of the greater pelvis. Below it is continuous with a wide shallow groove, bounded laterally by the anterior inferior iliac spine and medially by the iliopubic ramus.

• Sacropelvic surface

The sacropelvic surface, the posteroinferior part of the medial iliac surface, is bounded posteroinferiorly by the posterior border, anterosuperiorly by the medial border, posterosuperiorly by the iliac crest and anteroinferiorly by the line of fusion of the ilium and ischium. It is divided into iliac tuberosity and auricular & pelvic surfaces. The iliac tuberosity, a large, rough area below the dorsal segment of the iliac crest, shows cranial and caudal areas separated by an oblique ridge and connected to the sacrum by the interosseous sacroiliac ligament. The sacropelvic surface gives attachment to the posterior sacroiliac ligaments and, behind the auricular surface, to the interosseous sacroiliac ligament. The iliolumbar ligament is attached to its anterior part. The auricular surface, immediately anteroinferior to the tuberosity, articulates with the lateral sacral mass. Shaped like an ear, its widest part is anterosuperior, and its ‘lobule’ posteroinferior and on the medial aspect of the posterior inferior spine. Its edges are well defined but the surface, though articular, is rough and irregular. It articulates with the sacrum and is reciprocally shaped. The anterior sacroiliac ligament is attached to its sharp anterior and inferior borders. The narrow part of the pelvic surface, between the auricular surface and the upper rim of the greater sciatic notch, often shows a rough pre-auricular sulcus (that is usually better defined in females) for the lower fibres of the anterior sacroiliac ligament. The pelvic surface is anteroinferior to the acutely curved part of the auricular surface, and contributes to the lateral wall of the lesser pelvis. Its upper part, facing down, is between the auricular surface and the upper limb of the greater sciatic notch. Its lower part faces medially and is separated from the iliac fossa by the arcuate line. Anteroinferiorly, it extends to the line of union between the ilium and ischium. Though usually obliterated, it passes from the depth of the acetabulum to approximately the middle of the inferior limb of the greater sciatic notch.

Muscle attachments

The attachment of sartorius extends down the anterior border below the anterior superior iliac spine.

The iliac crest gives attachment to the anterolateral and dorsal abdominal muscles, and to the fasciae and muscles of the lower limb.

The fascia lata and iliotibial tract are attached to the outer lip and tubercle of its ventral segment.

Tensor fasciae latae is attached anterior to the tubercle. The lower fibres of external oblique and, just behind the summit of the crest, the lowest fibres of latissimus dorsi are attached to its anterior two-thirds. A variable interval exists between the most posterior attachment of external oblique and the most anterior attachment of latissimus dorsi, and here the crest forms the base of the lumbar triangle through which herniation of abdominal contents may rarely occur.

Internal oblique is attached to the intermediate area of the crest.

Transversus abdominis is attached to the anterior two-thirds of the inner lip of the crest, and behind this to the thoracolumbar fascia and quadratus lumborum. The highest fibres of gluteus maximus are attached to the dorsal segment of the crest on its lateral slope.

Erector spinae arises from the medial slope of the dorsal segment.

The straight head of rectus femoris is attached to the upper area of the anterior inferior spine.

Some fibres of piriformis are attached in front of the posterior inferior spine on the upper border of the greater sciatic foramen.

The gluteal surface is divided by three gluteal lines into four areas. Behind the posterior line, the upper rough part gives attachment to the upper fibres of gluteus maximus and the lower, smooth region to part of the sacrotuberous ligament and iliac head of piriformis. Gluteus medius is attached between the posterior and anterior lines, below the iliac crest, and gluteus minimus is attached between the anterior and inferior lines.

The fourth area, below the inferior line, contains vascular foramina. The reflected head of rectus femoris attaches to a curved groove above the acetabulum.

Iliacus is attached to the upper two-thirds of the iliac fossa and is related to its lower one-third. The medial part of quadratus lumborum is attached to the anterior part of the sacropelvic surface, above the iliolumbar ligament.

Piriformis is sometimes partly attached lateral to the pre-auricular sulcus, and part of obturator internus is attached to the more extensive remainder of the pelvic surface.

Vascular supply Branches of the iliolumbar artery run between iliacus and the ilium; one or more enter large nutrient foramina lying posteroinferiorly in the iliac fossa. The superior gluteal, obturator and superficial circumflex iliac arteries contribute to the periosteal supply. The obturator artery may supply a nutrient branch. Vascular foramina on the ilium underlying the gluteal muscles may lead into large vascular canals in the bone. Innervation The periosteum is innervated by branches of nerves that supply muscles attached to the bone, the hip joint and the sacroiliac joint.

OSSIFICATION

Ossification is by three primary centers: one each for the ilium, ischium and pubis. The iliac centre appears above the greater sciatic notch prenatally at about the 9^th week and the pubic centre in its superior ramus between the 4^th and 5^th months. The pubis is often not recovered from prenatal remains due to its size and fragility and because it is the last of the hip bones to begin ossification (Scheuer and Black 2004). At birth the whole iliac crest, the acetabular floor and the inferior margin are cartilaginous. Gradual ossification of the three components of the acetabulum results in a triradiate cartilaginous stem extending medially to the pelvic surface as a Y-shaped epiphysial plate between the ilium, ischium and pubis, and including the anterior inferior iliac spine. Cartilage along the inferior margin also covers the ischial tuberosity, forms conjoined ischial and pubic rami and continues to the pubic symphysial surface and along the pubic crest to the pubic tubercle. The ossifying ischium and pubis fuse to form a continuous ischiopubic ramus at the 7^th or 8^th year. 

Secondary centres, other than for the acetabulum, appear at about puberty and fuse between the 15^th and 25^th years. There are usually two for the iliac crest (which fuse early), and single centres for anterior inferior iliac spine (although it may ossify from the triradiate cartilage) and symphysial surface of the pubis (the pubic tubercle and crest may have separate centres). Progression of ossification of the iliac crest in girls is an index of skeletal maturity and is useful in determining the optimal timing of surgery for spinal deformity. Between the ages of 8 and 9 years, three major centres of ossification appear in the acetabular cartilage. The largest appears in the anterior wall of the acetabulum and fuses with the pubis, the second in the iliac acetabular cartilage superiorly, fusing with the ilium, and the third in the ischial acetabular cartilage posteriorly, fusing with the ischium. At puberty, these epiphyses expand towards the periphery of the acetabulum and contribute to its depth. Fusion between the three bones within the acetabulum occurs between the sixteenth and eighteenth years. Delaere et al have suggested that ossification of the ilium is similar to that of a long bone, possessing three cartilaginous epiphyses and one cartilaginous process, although it tends to undergo osteoclastic resorption comparable with that of cranial bones. During development, the acetabulum increases in breadth at a faster rate than it does in depth. Avulsion fractures of pelvic apophyses may occur from excessive pull on tendons, usually in athletic adolescents. The most frequent examples of such injuries are those to the ischial tuberosity (hamstrings) and anterior inferior iliac spine (rectus femoris).

Complied & written by Dr. Palak Shah.

 

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.

CARPAL BONES

 The Latin word "carpus" is derived from Greek καρπὁς meaning "wrist". The root "carp-" translates to "pluck", an action performed by the wrist.  In human anatomy, the main role of the wrist is to facilitate effective positioning of the hand and powerful use of the extensors and flexors of the forearm, and the mobility of individual carpal bones increase the freedom of movements at the wrist. 

There are 8 carpal bones, organized into two longitudinal rows, the proximal row contains Scaphoid, 

Lunate, Triquetrum and Pisiform and the distal row has Trapezium, Trapezoid, Capitate and 

Hamate.

SCAPHOID

It is a boat shaped bone and has a tubercle which is laterally, forwards and downwards.

The tubercle of the scaphoid gives attachment to flexor retinaculum and a few fibres of 

abductor pollicis brevis.

Scaphoid articulates with Radius, Lunate, Capitate, Trapezium and Trapezoid.

LUNATE

It is half-moon shaped or crescentic bone.

As it has a semi lunar surface, it articulates with the scaphoid on its lateral side. A quadrilateral 

surface for the triquetral on its medial side.

TRIQUETRAL 

It is a pyramid shaped bone.

The oval facet for the pisiform lies on the distal part of the palmar surface.

The medial and dorsal surfaces are continuous and nonarticular.

It articulates with pisiform, lunate, hamate and articular disc of the inferior radioulnar joint.

PISIFORM

It is a pea shaped bone.

The oval facet for the triquetral lies on the proximal part of the dorsal surface.

The lateral surface is grooved by the ulnar nerve.

It only articulates with Triquetral.

TRAPEZIUM

It is quadrangular in shape, has a crest and a groove anteriorly.

The palmar surface has a vertical groove for the tendon of the flexor carpi radialis.

The groove is limited literally by the crest of the trapezium.

The distal surface bears convexo-concave articular surface for the base of the 1st metacarpal bone.

It articulates with scaphoid, trapezium, capitate and 1st and 2nd metacarpal.

TRAPEZOID

It looks like a shoe of a baby.

The distal articular surface is bigger than the proximal.

The palmar nonarticular surface is prolonged laterally.

It articulates with scaphoid, trapezium, 2nd metacarpal and capitate.

CAPITATE

It is the largest bone in the carpal bones which has a rounded head.

The dorsomedial angle is the distal most projection from the body of the bone which bears a small facet for the 4th metacarpal bone.

It articulates with scaphoid, lunate, hamate, trapezoid and 2nd, 3rd & 4th metacarpals.

HAMATE

It is a wedge shaped with a hook near its base.

The hook projects from the distal parts of the palmar surface and is directed laterally.

MUSCLES AND LIGAMENTS

The intricate movements of the hand are facilitated by a delicate balance of muscular forces and a robust ligamentous network within the wrist. Two primary muscle groups contribute: extrinsic muscles, originating in the forearm, stabilize the wrist by maintaining hand position on the radius during coordinated muscle contractions. Intrinsic muscles, originating within the hand, fine-tune movements by balancing flexor and extensor forces.

The flexor carpi ulnaris, an extrinsic muscle, significantly influences wrist movement by inserting onto the hamate, pisiform, and the base of the fifth metacarpal. Intrinsic muscles demonstrate diverse origins: thenar muscles arise from the scaphoid and trapezium, the adductor pollicis originates from the capitate and second/third metacarpals, and hypothenar muscles originate from the pisiform and hamate.

A complex system of ligaments provides stability. Radiocarpal ligaments connect the radius to various carpal bones (scaphoid, lunate), while ulnocarpal ligaments connect the ulna to the lunate and capitate. Intercarpal ligaments bind the carpal bones together (e.g., lunotriquetral, scapholunate), forming a strong, interconnected structure. These ligaments, along with carpometacarpal and intermetacarpal ligaments, ensure stability during a wide range of hand movements.

BLOOD SUPPLY, LYMPHATICS AND NERVOUS SUPPLY

The radial artery, ulnar artery, and their anastomoses provide the blood supply of the wrist. The radial artery predominantly supplies the thumb and the lateral side of the index finger while the ulnar artery supplies the rest of the digits and the medial side of the index finger. In particular, vascular supply takes place via the anastomotic network consisting of three dorsal and three palmar arches, which arise from both the radial and ulnar arteries, that overlie the carpal bones. The scaphoid, capitate, and a minority of lunates (20%) all have one intraosseous vessel supply. Of note, the scaphoid has a single blood supply from the radial artery that enters from the distal portion of the bone to supply the proximal portion, thus making its proximal pole most vulnerable to avascular necrosis. The trapezoid and hamate both have two areas of blood supply without intraosseous anastomoses. The trapezium, triquetrum, pisiform, and most lunates (80%) have two areas of blood supply and consistent intraosseous anastomoses. Therefore, the rest of the carpal bones, excluding the scaphoid, capitate, and the minority of lunates, have a lower risk of developing avascular necrosis following a fracture.

Innervation of the wrist joint comes from the:

• anterior interosseous branch of the median nerve
• posterior interosseous branch of the radial nerve
• the dorsal and the deep branches of the ulnar nerve

The lateral antebrachial cutaneous nerve, the posterior interosseous nerve, the dorsal branch and the perforating branches of the ulnar nerve, and the superficial branch of the radial nerve innervate the wrist joint from the dorsum. The palmar cutaneous branch of the median nerve, the anterior interosseous nerve, and the main trunk and deep branch of the ulnar nerve innervate the wrist joint from the palmar side.

EMBRYOLOGY

Upper limb development initiates with the activation of a group of mesenchymal cells in the lateral mesoderm towards the end of the fourth week, with the limb buds becoming visible around day 26 or day 27. Each limb bud comprises a mass of mesenchyme covered by ectoderm. This mesenchyme remains undifferentiated until it is ready to develop into bone, cartilage, and blood vessels later in development. Meanwhile, at the apex of each limb bud, the ectoderm thickens to form the apical ectodermal ridge, which stimulates the growth and development of the upper limb bud in the proximal-distal axis. Other signaling centers and primary morphogens such as the zone of polarizing activity, derived from an aggregate of mesenchymal cells in the limb bud, and the Want pathway, expressed from the dorsal epidermis of the limb bud, also contribute to the development of the upper limb buds by regulating growth along the anteroposterior axis and the dorsoventral axis, respectively.

At the end of the sixth week of development, digital rays form in the hand plate. By the seventh week, the carpal chondrification process begins. The capitate and the hamate carpal bones are the first chondrogenic centers to appear as immature cartilage early in the eighth week while the pisiform is the last to appear later in the eighth week. The hamulus, otherwise known as the “hook of the hamate,” also appears as an immature cartilaginous tissue towards the end of the eighth week and does not complete its development until the thirteenth week. Last, in the fourteenth week, a vascular bud penetrates the lunate cartilage mold, an early sign of the osteogenic process that will complete during the first year of life.

Complied & Written by Dr. Palak Shah