L2 - Pelvis & Hip Joint Flashcards
What is the function of the pelvic girdle?
How does it compare to the shoulder girdle?
it connects the vertebral column to the femurs
it is much stronger and less flexible than the shoulder girdle
What are the 3 bones and 3 joints of the pelvic girdle?
Bones:
- left and right innominate (hip) bones
- sacrum
Joints:
- 2 sacroiliac joints
- pubic symphysis joint
What is the main function of the pelvis?
it bears the weight of the upper body when walking
the vertebral column transfers body weight to the lower limbs through the pelvis
What is the secondary function of the pelvis?
it protects the pelvic viscera and blood vessels
it protects the foetus during pregnancy
What are the articulations of the innominate bones?
the innominate bones articulate posteriorly with the sacrum
they articulate anteriorly at the pubic symphysis joint
Label the features of the pelvic girdle
What are the 3 bones that fuse together to form the innominate (hip) bone?
What do they form when they fuse?
- ileum
- ischium
- pubis
These fuse at the acetabulum
What does the acetabulum articulate with?
the acetabulum articulates with the femoral head
this is the hip joint
Label the bones and articulation of the hip joint
What are the 2 main ligaments in the pelvis?
What structures do they form?
Sacrospinous ligament:
this runs from the sacrum to the ischial spine
this forms the greater sciatic foramen
Sacrotuberous ligament:
this runs from the sacrum to the ischial tuberosity
this forms the lesser sciatic foramen
How does the sciatic nerve pass through the pelvis?
it passes from inside the pelvis out into the lower limb via the greater sciatic foramen
Which colours represent the ligaments and the foramina of the of the pelvis?
red - greater sciatic foramen
green - lesser sciatic foramen
pink - sacrotuberous ligament
purple - sacrospinous ligament
What is the function of the acetabular labrum?
it is a lip of cartilage that deepens the articular surface
this makes the acetabulum a better fit for the femoral head
Label the features of the acetabulum
What is the role of the fibrous capsule?
it is a strong and dense fibrous capsule that surrounds the femoral head within the acetabulum
even if the femoral head is moving within the acetabulum, the fibrous capsule surrounding it keeps it stable
What are the proximal and distal attachments of the fibrous capsule?
proximal attachment:
rim of the acetabulum
distal attachment:
femoral neck (intertrochanteric line and greater trochanter)
What are the three ligaments of hip joint?
- pubofemoral ligament
- iliofemoral ligament
- ischiofemoral ligament
What is the role of the pubofemoral ligament?
it prevents excessive abduction
What is the role of the iliofemoral ligament?
it is the strongest ligament
it prevents hyperextension of the hip during standing as it “screws in” the femoral head
What is the weakest ligament of the hip joint?
ischiofemoral ligament
What is the function of the hip joint ligaments?
How do they acheive this?
- they spiral around the hip joint
- they become taut when the hip is extended
- they pull the femoral head into the acetabulum
THIS IMPROVES STABILITY
Which ligaments are shown in the diagram?
Which ligament is this?
ischiofemoral
What are the 3 factors that provide stability of the hip joint?
- the anatomy of the acetabulum
- fibrous capsule
- the ligaments - iliofemoral, ischiofemoral and pubofemoral
What are the typical injuries that occur to the hip?
- fractures to the pelvic ring
- dislocation of the hip joint
- fracture to the neck of the femur - ‘hip fracture’
What happens in a congenital hip problem?
children can have problems with development of the hip joint, leading to joint laxity, subluxation and dislocation of the hip
if this is not detected and treated early, the hip fails to develop
Label the features on the AP pelvis X-ray
Which points of the pelvis are common sites for fracture in elderly people?
the superior and inferior pubic rami
What is Shenton’s line?
Why is this clinically significant?
it is a smooth line along the medial aspect of the femur, over and around the top of the obturator foramen
in a hip fracture, Shenton’s line is often disrupted and no longer smooth
What fracture is shown below?
What is significant about the yellow line?
fracture of the pubic rami
both the superior and inferior pubic rami have been fractured
Shenton’s line has been disrupted and is no longer smooth on the fractured side
What type of fracture is shown in the X-ray?
What usually causes it?
‘Open book’ fracture
the pubic symphysis is splayed wide open
this occurs when there is a large force causing compression on the anterior surface of the pelvis
What type of fracture is shown in the image?
What causes this and why can it be fatal?
‘Vertical shear’ fracture
this occurs when one part of the pelvis moves more vertically relative to the other
it can be fatal due to the presence of blood vessels and the risk of them being torn and causing concealed bleeding into the pelvis
What device is this?
When is it used and why?
Pelvic binder
it is put on the patient at the site of accident
it is slipped underneath the patient, wrapped around and tightened up to keep the pelvis as stable as possible in case there are fractures present
Label the parts of the proximal femur
Where is the subtrochanteric region of the femur?
the region underneath the lesser trochanter
What are the 4 regions in which a fracture of the proximal femur can occur?
- subcapital # is just underneath the head of the femur
- transcervical # is a fracture through the neck of the femur
- trochanteric #
- subtrochanteric # is just underneath the trochanteric region
What fracture is shown in the X-ray?
this is a fracture of the neck the femur
this is a typical “hip fracture”
How is Shenton’s line affected in a hip fracture (neck of femur fracture)?
Shenton’s line cannot be traced due to loss of alignment
What type of fracture is shown here?
What is the problem when interpreting this X-ray clinically?
this is a fracture through the femoral neck (hip fracture)
Shenton’s line does not look disrupted even though a fracture is present
Which arteries that supply the hip joint are shown?
What artery is the main supply to the hip joint?
medial circumflex artery
this gives off the branches that enter the joint capsule to supply the femoral head
How does blood go from the aorta to the hip?
Which arteries must it pass through?
- the abdominal aorta divides into a left and right common iliac artery
- each common iliac artery divides into internal and external iliac arteries
- the external iliac artery passes underneath the inguinal ligament and becomes the femoral artery
- the profunda femoris is a large branch of the femoral artery
- the profunda femoris gives rise to the medial circumflex artery and lateral circumflex artery which supply the hip
What may happen if a fracture to the neck of the femur tears the surrounding blood vessels?
Most of the blood supply to the hip is via the lateral and medial circumflex arteries
if these are compromised, it may lead to avascular necrosis of the head of the femur
What other artery contributes to the blood supply at the hip?
inferior gluteal artery
this comes from the internal iliac artery
What is the cruciate anastomosis?
Which vessels are involved?
it is a collateral artery supply to the hip joint consisting of:
- medial circumflex arteryy
- lateral circumflex artery
- inferior gluteal artery
- first perforating artery of profunda femoris
What happens if a fracture to the femoral neck tears the medial circumflex artery?
it leads to loss of blood supply to the femoral head
this can lead to avascular necrosis of the femoral head
What condition is shown in these X-rays?
arthritis of the hip
it is characterised by joint space narrowing
Why is hip arthritis painful for the patient?
every time the patient moves, there is bone grinding on bone as the articular cartilage has been worn away
this causes pain on moving and the pain eases with rest
Which injury is shown in the X-ray?
How is the appearance of the limb affected?
posterior dislocation
the limb appears shortened and internally rotated
How is the position of the limb different after posterior dislocation and fracture of the hip?
When the hip is fractured, the limb appears shortened and externally rotated
In posterior dislocation, the limb appears shortened and internally rotated
What causes posterior dislocation of the hip?
Impact when the hip is:
- flexed
- internally rotated
- adducted
This occurs when impact is applied in the seated position
This causes the head of the femur to be driven posteriorly out of the acetabulum
What injuries are associated with posterior dislocation of the hip?
- sciatic nerve injury (L4-S3)
- acetabular fracture
What injury is shown in the X-ray?
What causes it?
anterior dislocation
occurs when force is applied during extreme abduction with external rotation of the hip
this causes the femoral head to be levered out anteriorly
How does the limb appear in an anterior dislocation?
it appears:
- externally rotated
- abducted
- flexed
What injury is shown in the X-ray?
medial dislocation / acetabular fracture
the head of the femur is driven medially into the pelvis
What is DDH?
developmental dysplasia of the hip
it is a congenital abnormality causing hip dysplasia
What happens in DDH?
the ligaments around the hip are lax (loose)
the head of the femur can sublux and move slightly out of the acetabulum
this means that the acetabulum doesn’t develop properly as it is not in contact with the head of the femur
What are the different types of hip dysplasia that may be present in DDH?
- subluxation
- high dislocation
- low dislocation
What is the treatment for DDH and how does it work?
a cast and harness is used to keep the head of the femur within the acetabulum
this allows for normal development to continue
What movements are possible at the hip joint?
- flexion
- extension
- abduction
- adduction
- external/internal rotation
Which muscles are shown on the diagram and what is their function?
Where are the flexors/extensors of the hip joint located?
Flexors lie anteriorly
Extensors lie posteriorly
Lateral rotators also lie posteriorly
What is iliopsoas formed from?
What is its insertion?
Psoas major:
comes off the lumbar vertebrae and forms part of the posterior body wall
Iliacus:
comes off the iliac fossa of the pelvis
These muscles come together and form a common tendon that inserts onto the lesser trochanter
What is the function of iliopsoas?
it is a primary flexor of the hip joint
it pulls the lesser trochanter up towards the pelvis and trunk when it contracts
What is the function of rectus femoris?
Where does it insert?
It is a flexor of the hip
It attaches to the anterior inferior iliac spine
What is the function of sartorius?
it flexes the hip joint
What is the insertion and function of the adductor muscles?
they come off of the pubic bone medially and insert onto the femur
they are adductors of the hip
Why do the adductor muscles play an important role in walking?
they bring the legs back towards the midline during walking
this allows you to walk with one foot in front of the other
Which muscles are shown in this diagram?
Orange - gluteus muscles
Green - short hip muscles
Blue - hamstring muscles
Pink - adductor muscles
What are the functions of the gluteus muscles?
Gluteus maximus - extensor of the hip
Gluteus minimus and gluteus medius are abductors of the hip
What are the functions of the short hip muscles and the hamstring muscles?
Short hip muscles - primarily lateral rotators
Hamstring muscles - extensors of the hip
Which structures are shown by the red lines?
superior and inferior gluteal neurovascular bundles
these consist of an artery, vein and nerve
they emerge above and below the piriformis muscle
