Overview
The femur is the longest bone in the body and the only bone in the thigh.
Gross Anatomy
Development
The femur
develops from the mesoderm and ectoderm in the limb buds. The primary centre in
the shaft ossifies at 7-8weeks in utero, and fuses at 16-18 years old. The
secondary ossification centres are at the distal physis (ossifies at birth,
fuses age 19), head (ossifies at 1year, fuses at 18 years), greater trochanter
(ossifies at 4-5 years, fuses at 16 years) and lesser trochanter (ossifies at
10years, fuses age 16).
Macro-anatomy
The head,
neck, greater and lesser trochanters are located proximally. The neck is
comprised of tensile and compressive groups of trabeculae. The head has a fovea
for the attachment of ligamentum teres. On the anterior surface, the
intertrochnteric line is where the fibrous capsule attaches. Posteriorly the
capsule attaches more proximally on the neck. The 2 femoral condyles, medial
and lateral, are located distally. The lateral condyle projects more anteriorly
and proximally. The medial condyle is larger, more posterior and distal. The
femoral anteversion is usually 12-14 degrees. The normal neck-shaft angle is
126 degrees. The anatomical axis is along the shaft of the femur. The
mechanical axis is from the femoral head to the intercondylar notch. The shaft
of the femur descends 7degress medially in the coronal plane. The mid femur is
triangular shape in cross-section. Along the posterior aspect of the shaft
proximally is the gluteal tuberosity and more distally the linea aspera.
Articulations
Hip joint: Proximally the femoral head
articulates with the pelvic acetabulum forming the hip joint. This is a
synovial ball and socket type joint. The acetabulum is deepened and stabilised
by the labrum. The transverse acetabular ligament runs from anteroinferior to
posteroinferior acetabulum.
The
ligaments involved in the joint capsule are: pubofemoral, iliofemoral,
ischiofemoral and zona orbicularis. The strongest of these is the iliofemoral
ligament.
Knee joint: Distally the femoral condyles
articulate with the tibia to form the knee joint.
Blood supply
Blood
supply to the head and neck comes from the retinacular branches of the medial
and lateral circumflex arteries (branches off profunda). The shaft is supplied
by the nutrient artery which is a branch of profunda femoris artery. The blood
supply to the head and neck of femur is tenuous and retrograde. This leads to
an increased risk of avascular necrosis in intracapsular neck of femur
fractures.
Ligamentous attachments
Greater trochanter:
§ Piriformis (insertion)
§ Obturator interus (insertion)
§ Superior gemellus (insertion)
§ Gluteus medius (insertion)
§ Gluteus minimus (insertion)
Lesser trochanter:
§ Ileopsoas (insertion)
Linea aspera:
§ Adductor magnus (insertion)
§ Adductor longus (insertion)
§ Adductor brevis (insertion)
§ Biceps femoris (origin)
§ Pectineus (insertion)
§ Gluteus maximus (insertion)
§ Vastus lateralis (origin)
§ Vastus medialis (origin)
Adductor tubercle:
§ Adductor magnus (insertion)
Clinical Anatomy
Femoral neck fractures:
Either low energy
fractures in the elderly oseoporotic patients, or high energy injuries in the
young.
Can be divided into
intracapsular or extracapsular fractures
Intracapsular fractures
have a higher risk of interrupting the blood supply to the femoral head,
leading to avascular necrosis. Intracapsular fractures can be classified
according to the Garden classification:
§ 1 = valgus
impacted/ incomplete
§ 2 = non-displaced
§ 3 = partially displaced
§ 4 = displaced
The fracture pattern and
patient factors dictate the choice of surgical management.
Hip dislocation:
Caused by high energy
trauma and often have multiple associated injuries.
85% are posterior
dislocations. In this case the thigh will be adducted, flexed and internally
rotated.
Early reduction is
essential
Complications include:
avascular necrosis, sciatic nerve injuries (posterior), femoral artery and
nerve injury (anterior), instability, osteoarthritis, heterotopic ossification
Femoral shaft fracture:
High energy injury and a
potential source of significant blood loss.
Perthes disease:
Osteonecrosis of the
femoral head of idiopathic or vascular etiology.
Usually presents in boys
aged 4-8 years with unilateral thigh or knee pain and limp.
Slipped upper femoral epiphysis (SUFE)
Usually presents in obese
11-14 year olds with hip, thigh or knee pain and limp.
Quick Anatomy
Key Facts
|
|
|
Ossify |
Fuse |
|
Primary |
Shaft |
7-8 wks
in utero |
16-18yrs |
|
Secondary
|
Distal
physis |
Birth |
19yrs |
|
Head |
1yr |
18yrs |
|
|
Greater
trochanter |
4-5yrs |
16yrs |
|
|
Lesser
trochanter |
10yrs |
16yrs |
Aide-Memoire
Summary
The femur
is a long bone, with multiple muscle attachments. The main pathology occurs because the femoral neck weakens with age
leading to an increased susceptibility to fracture.