Session 3: Disorders of the Hip

Question 1

Explain what a pulled hamstring is.

Answer 1

Sudden muscular exertion resulting in a stretch of the posterior thigh muscle. A muscle sprain, a partial tear or a complete tear from the ischial tuberosity. Can even be accompanied by an avulsion of a fragment of a bone (where a tendon or ligament attaches to the bone, the ligament or tendon can pull of a bit of the bone).

Question 2

What is the cause and risk factors of primary osteoarthritis?

Answer 2

There is no known cause. Risk factors:

• Age
• Sex (female)
• Ethnicity (increased risk in African-american, American Indian or hispanic women)
• Genetics
• Nutrition (rich diet in vitamin C and E may provide some protection)

Question 3

What are the risk factors of secondary osteoarthritis?

Answer 3

• Obesity • Trauma • Malalignment like developmental dysplasia of the hip. • Infection like septic arthritis and tuberculosis • Inflammatory - rheumatoid arthritis, ankylosing spondylitis e.g. • Metabolic disorders affecting joints (gout) • Haematological disorders (bleeding into joints e.g.) • Endocrine abnormalities

Question 4

Give symptoms of osteoarthritis.

Answer 4

• Deep aching joint pain • Reduced range of motion and crepitus • Stiffness during rest • Pain in the hip, gluteal and groin regions radiating to the knee via the obturator nerve

Question 5

Explain the pathology of osteoarthritis.

Answer 5

• Damage of hyaline cartilage usually due to an uneven loading of the joint • Hyaline cartilage becomes swollen due to increased proteoglycan synthesis by chondrocyte (this stage can last for years as an attempt to repair the cartilage damage) • Proteoglycan levels eventually fall. Cartilage soften and loses elasticity. Flaking and fibrillation develop along the articular surface and over time the cartilage becomes eroded down to the bone resulting in loss of joint space. • Vascular invasion, increased cellularity and swelling as the subchondral bone becomes thickened and denser at areas of pressure. (Called eburnation which is manifested as subchondral sclerosis) • Cystic degeneration forming subchondral bone cysts • Osseous metaplasia of connective tissue leading to osteophytes

Question 6

What are the four cardinal signs of osteoarthritis?

Answer 6

• Reduced joint space • Subchondral sclerosis • Bone cysts • Osteophytes

Question 7

Give non-operative management options.

Answer 7

• Activity modification • Weight loss • Assisted walking like a stick • Physiotherapy • Medications ◦ General pain medication like paracetamol ◦ NSAIDs ◦ Cox-2 inhibitors ◦ Nutritional supplements • Injections ◦ Corticosteroids ◦ Viscosupplementation (hyaluronic acid)

Question 8

Give operative management options.

Answer 8

The only cure for osteoarthritis is total hip replacement which is the insertion of an implant where the distal part of the femur used to be (mostly head and neck of femur)

Question 9

What is a fractured neck of femur defined as?

Answer 9

A fracture of the proximal femur up to 5 cm below the lesser trochanter.

Question 10

Label the diagram. Which types of fracture?

Answer 10

Question 11

NOF can be put into two categories. Which?

Answer 11

• Intracapsular
• Extracapsular (intertrochanteric and subtrochanteric)

Question 12

What type of fracture is the most damaging? Why? How is this risk increased?

Answer 12

Intracapsular fracture.

Because they are likely to disrupt the ascending cervical branches (retinacular arteries) of the medial circumflex femoral arteries (MCFA).

The ligamentum teres will not be able to supply the femoral head on its own, this can lead to avascular necrosis of the femoral head.

If the fracture is displaced.

Question 13

Why would not extracapsular fracture cause avascular necrosis of the femoral head?

Answer 13

Because the retinacular arteries are likely to remain intact.

Question 14

Are different people more susceptible to either intra or extracapsular fracture?

Answer 14

Intra: usually elderly and post-menopausal women with osteoporotic bone usually from a minor fall.

Extra: Affect young and middle-aged population. Usually from significant trauma like road traffic collision.

Question 15

Explain how avascular necrosis of intracapsular fracture (#NOF) would be treated.

Answer 15

Surgical replacement of the femoral head either by hemiarthroplasty which is the femoral head only or a totalt hip replacement where you replace both the femoral head and the acetabular cup.

Question 16

What are the symptoms of #NOF?

Question 17

What would #NOF look like upon examination if the fracture is displaced?

Answer 17

Affected leg would usually be shortened, abducted and externally rotated.

Exacerbation of pain on palpation of the greater trochanter and pain is exacerbated by rotation of the hip.

Question 18

Why would the hip be shortened, abducted and laterally rotated?

Answer 18

The displaced fracture allows the shaft of the femur to move independently from the hip joint.

Axis of rotation is instead to pass trhough the greater trochanter and vertically down the long axis of the femoral shaft.

The short lateral rotators of the hip contract and laterally (externally) rotate the femoral shaft.

Iliopsoas will also act as a lateral rotator now.

Gluteus medius and gluteus minimus abduct the femur distal to the fracture site. They also rotate the greater trochanter laterally adding to the external rotation.

Shortening of limb is becuase the strong muscles of the thigh pull the distal framgent of the femur upwards. (rectus femoris, adductor manus and the hamstring muscles)

Question 19

Define dislocation of the hip.

Answer 19

The head of femur is fully displaced out of the cup-shaped acetabulum of the pelvis.

Question 20

What main types of dislocations are there?

Answer 20

Congenital (developmental dysplasia (DHH) and Congenital dislocation (CDH))

and traumatic.

Question 21

There are three subtypes of dislocation of the hip. Which is most common?

Answer 21

Posterior, anterior and central dislocation.

Posterior is most common (90%)

Question 22

What do the different hip dislocations look like? (Not looking at X-ray)

What are palsies are associated with each dislocation?

Answer 22

Posterior: Affected limb will be shortened and held in a position of flexion, adduction and medial rotation.
Sciatic nerve palsies (8-20%)

Anterior: Affected limb is held in a position of external rotation and abduction with a slight flexion.

Femoral nerve palsies can present but are uncommon

Central dislocation: Head of femur is driven into the pelvis through the acetabulum. Always a fracture dislocation. Femoral head is palpable on rectal examination and high risk of intrapelvic haemorrhage due to disruptino of the pelvic venous plexuses

Question 23

Why do shortening and internal rotation of the affected limb occur after posterior dislocation of the hip?

Answer 23

Femoral head is pushed backwards over the posterior amrgion of the acetabulum.

This means it comes to lie on the lateral surface of the ilium.

Head of the femur is then pulled upwards by strong extensors (gluteus maximus and hamstrings) and adductors of the hip causing limb shortening.

The anterior fibres of the gluteus medius and minimus which are inserted on the lateral surface of the greater trochanter and anterior aspect of the greater trochanter respectively will pull on the greater trochanter causing internal rotation.

Question 24

How does an anterior dislocation of the hip present?

Answer 24

Limb is held in a position of external rotation and abduction with slight flexion.

Femoral nerve palsies can be present but are uncommon.

Question 25

What is a central dislocation of the hip?

Answer 25

When the head of the femur is driven into the pelvis through the acetabulum. This type of dislocation is always a fracture dislocation.

Question 26

How can you examine (not x-ray) central dislocation?

Answer 26

Upon rectal examination the femoral head will be palpable.

Question 27

Complications of central dislocation of the hip.

Answer 27

High risk of intrapelvic haemorrhage due to disruption of the pelvic venous plexuses. This can be a life-threatening injury.