Disorders of the Hip Flashcards
Who is osteoarthritis most common in?
Most commonly affects the elderly; 20-30% of people over the age of 70 suffer from
OA of the hip
Pathology of osteoarthritis
Precipitating risk factors (e.g. obesity, trauma, malalignment) lead to excessive
or uneven loading of the joint. This leads to damage to the hyaline cartilage
covering the articular surface.
Initially, the hyaline cartilage becomes swollen due to increased proteoglycan
synthesis by chondrocytes, with increased numbers of chondrocytes
differentiating from chondroprogenitor cells [Note: normal adult chondrocytes
are fully differentiated and do not proliferate]. This stage reflects an attempt to
repair the cartilage damage and can continue for several years.
As the disease progresses however, the proteoglycan content falls, causing the
cartilage to soften and lose elasticity. Microscopically, flaking and fibrillation
(vertical clefts) develop along the normally smooth articular surface. Over time,
the cartilage becomes eroded down to the subchondral bone, resulting in loss
of joint space. These surface changes in the cartilage alter the distribution of biomechanical
forces and trigger further active changes in the tissues. The subchondral bone
responds with vascular invasion and increased cellularity, becoming thickened
and denser at areas of pressure. This process, known as eburnation, manifests
as subchondral sclerosis on X-rays.
The traumatised subchondral bone may also undergo cystic degeneration to
form subchondral bone cysts. These are attributable to either osseous necrosis
secondary to chronic impaction (pressure), or to the intrusion of synovial fluid.
At areas along the articular margin, osseous metaplasia of connective tissue
occurs, leading to irregular outgrowth of new bone (osteophytes).
Risk factors for primary osteoarthritis
Age
* Female sex
* Ethnicity (e.g. increased risk in African-American, American Indian or Hispanic
women compared with Caucasian Americans)
* Genetics (OA runs in families)
* Nutrition e.g. consumption of a diet rich in Vitamins C and E (antioxidants)
may provide some protection against OA.
Specific causes of secondary osteoarthritis
Obesity
* Trauma (including sports and occupational risk factors)
* Malalignment e.g. Developmental dysplasia of the hip (previously referred to
as congenital hip dislocation)
* Infection e.g. septic arthritis, tuberculosis
* Inflammatory arthritis e.g. rheumatoid arthritis, ankylosing spondylitis
Metabolic disorders affecting the joints e.g. gout
* Haematological disorders e.g. haemophilia with haemarthrosis
(bleeding into joints)
* Endocrine abnormalities e.g. diabetes with neurovascular impairment,
which can lead to chronic malalignment of the articular surfaces
(Charcot joint) and secondary osteoarthritis
Symptoms of osteoarthritis
A deep aching joint pain, exacerbated by use
* Reduced range of motion and crepitus (grinding)
* Stiffness during rest (morning stiffness, usually lasting < 1 hour)
Four cardinal signs of osteoarthritis on an X-ray
Reduced joint space
* Subchondral sclerosis
* Bone cysts
* Osteophytes
Who is osteoarthritis of the hip most common in?
Males over 40 years of age
Symptoms of osteoarthritis of the hip
Joint stiffness (typically occurs getting out of bed and when standing up after
sitting down for a long time)
* Pain in the hip, gluteal and groin regions radiating to the knee (via the
obturator nerve)
* Mechanical pain (pain accentuated by mobilisation or weight-bearing)
* Crepitus (a grating sound or crunching/crackling sensation on movement of
the joint)
* Reduced mobility e.g. difficulty walking, difficulty putting on socks and shoes,
getting in and out of a car / the bath etc.
Treatment of osteoarthritis of the hip
Weight reduction if overweight
A walking-stick or walking frame may also be
used to reduce the load through the arthritic joint whilst walking
Muscle-
strengthening exercises and orthotic footwear can rebalance a misaligned load
through the joint
Analgesia (e.g. paracetamol) and anti-inflammatories (NSAIDs,
COX-2 inhibitors) can be prescribed and some patients report an additional benefit
from taking nutritional supplements e.g. glucosamine and chondroitin sulfate
Steroid injections can be performed into the joint to reduce swelling and thereby
alleviate shoulder stiffness and pain
Hyaluronic acid injections into the joint
(viscosupplementation) may increase lubrication and possibly promote cartilage
repair, although the evidence for this is limited
‘Cure’ for osteoarthritis of the hip
Total hip replacement
What is a fracture of the femoral neck?
A fracture of the proximal femur, up
to 5cm below the lesser trochanter.
How are NOFs classified?
Intracapsular
Extracapsular (which are further divided into intertrochanteric and
subtrochanteric)
What are the implications for blood supply with an intracapsular fracture?
Intracapsular fractures are likely to disrupt the ascending cervical (retinacular)
branches of the medial femoral circumflex artery (MFCA). Due to the inability of
the Artery of the Ligamentum Teres to sustain the metabolic demand of the
femoral head, there is a high risk of avascular necrosis of the bone. This risk is
increased if the fracture is displaced.
Who are intracapsular fractures most common in?
Intracapsular fractures are more common in the elderly, especially post-
menopausal women with osteoporotic bone. They often occur after a minor fall.
Who are extracapsular fractures most common in?
Extracapsular fractures tend to affect the young and middle-aged population and
are usually the result of significant traumatic force e.g. a road traffic collision.
How is a displaced intracapsular fracture in an older person usually treated?
Surgical replacement of the femoral head (either
hemiarthroplasty [femoral head only] or total hip replacement [head and
acetabular cup])
Symptoms of NOF
- Reduced mobility / sudden inability to bear weight on the limb
- Pain which may be felt in the hip, groin and/or knee
Why is the hip shortened, abducted and externally rotated in a displaced #NOF?
The #NOF allows the shaft of the femur to move independently of the hip joint.
The axis of rotation of the femur that normally passes obliquely through the head
and down the neck of the femur, shifts to pass through the greater trochanter and
vertically down the long axis of the femoral shaft. The short lateral rotators of the
hip (piriformis, obturator internus, superior and inferior gemelli and quadratus
femoris) contract and laterally (externally) rotate the femoral shaft. The iliopsoas
also now acts as a lateral rotator of the femur as it pulls the lesser trochanter
anteriorly about the new axis of rotation, so the femoral shaft rotates externally.
The strong abductors that attach to the greater trochanter (gluteus medius and
minimus) abduct the femur distal to the fracture site. They also rotate the greater
trochanter laterally about the new longitudinal axis of rotation, adding to the
external rotation caused by iliopsoas and the short lateral rotators.
Shortening of the limb occurs because the strong muscles of the thigh pull the distal
fragment of the femur upwards. These include rectus femoris, adductor magnus
and the hamstring muscles.
What is traumatic dislocation of the hip?
The head of the femur being fully displaced out of
the cup-shaped acetabulum of the pelvis (less than complete displacement =
subluxation)
How else can dislocations of the hip occur?
Dislocations may be congenital - Developmental dysplasia of the hip (DDH)
How does traumatic dislocation of the hip usually present?
90% of hip dislocations are posterior. The most common cause is the knee
impacting the dashboard during a road traffic collision. The affected limb will be
shortened and held in a position of flexion, adduction and internal (medial)
rotation. A sciatic nerve palsy is present in 8-20% of cases.
Why do shortening and internal rotation of the limb occur after posterior
dislocation of the hip?
The femoral head is pushed backwards over the posterior margin of the
acetabulum and comes to lie on the lateral surface of the ilium. The head of the
femur is then pulled upwards by the strong extensors (gluteus maximus and
hamstrings) and adductors of the hip, causing limb shortening.
The anterior fibres of the gluteus medius and minimus pull on the posteriorly-
displaced greater trochanter and cause the femur to rotate internally.
How does the limb present in anterior dislocation?
The limb is held in a position of external rotation and
abduction with slight flexion. Femoral nerve palsies can be present but are
uncommon.
How does the limb present in central dislocation?
The head of the femur is driven into the pelvis through the
acetabulum. It is always a fracture-dislocation. The femoral head is palpable on
rectal examination and there is a high risk of intrapelvic haemorrhage due to
disruption of the pelvic venous plexuses. This can be a life-threatening injury.
