Clinical Conditions of the Hip Joint Flashcards
How is Osteoarthritis defined pathologically?
A degenerative disorder arising from the breakdown of articular hyaline cartilage
How is Osteoarthritis defined clinically?
A clinical syndrome comprising joint pain accompanied by functional limitation and reduced quality of life
What is Osteoarthritis?
It’s a chronic disease of the musculoskeletal system without systemic involvement (i.e. no involvement of eyes, skin, etc) and is non-inflammatory.
Is ankylosis seen in Osteoarthritis?
Compared with some inflammatory arthropathies (e.g. ankylosing spondylitis), ankylosis (bony fusion across a joint) is very rarely seen in osteoarthritis.
How can OA be classified?
OA can be classified into primary or secondary
Primary OA - cause is unknown
Secondary OA - cause is known
Give examples of causes of secondary OA
Trauma, Metabolic disorders affecting the joint (e.g. gout), Inflammatory arthritis (e.g. rheumatoid arthritis)
What are the risk factors for OA?
Obesity, Age, Female sex
What are the symptoms of OA?
Deep aching joint pain, exacerbated by use
Reduced range of motion and crepitus (grinding)
Stiffness during rest (morning stiffness, usually lasting <1 hour)
Describe the pathology of osteoarthritis
Hyaline cartilage covering the articular surface becomes swollen due to increased proteoglycan synthesis by chondrocytes, with increased numbers of chondrocytes differentiating from chondroprogenitor cells. This is due to an attempt to repair the cartilage damage and can last for several years
As the disease progresses, however, the level of proteoglycans falls, causing the cartilage to soften and lose elasticity. Microscopically, flaking and fibrillations (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 dense at areas of pressure. This is eburnation, and manifests as subchondral sclerosis on X-rays.
The traumatised subchondral bone may also undergo cystic degeneration to form subchondral cysts. These are attributable to either osseous necrosis secondary to 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)
Name the four cardinal signs of OA on an X-ray
Reduced joint space
Subchondral sclerosis
Bone cysts
Osteophytes
If a patient experiences osteoarthritis of the hip, why might they feel pain radiating to the knee?
Pain is radiated to the knee via the obturator nerve
What is the cure for osteoarthritis of the hip?
Total Hip Replacement
Define a fractured neck of femur
A fracture of the proximal femur, up to 5cm below the greater trochanter
What are the symptoms of a fracture neck of femur?
Reduced mobility/sudden inability to bear weight on the limb
Pain which may be felt in the hip, groin and/or knee
How does a fractured neck of femur present on examination?
The affected leg is shortened, abducted and externally rotated.
What else can be seen on examination of a fractured neck of femur?
There is exacerbation of pain on palpation of the greater trochanter and pain is exacerbated by rotation of the hip. When examining a fractured hip, avoid vigorous examination as there’s a risk of displacing the fracture
How can a fractured neck of femur be classified?
Intracapsular - either subcapital or transcervical
Extracapsular - either intertrochanteric or subtrochanteric See pic
Why are intracapsular fractures more problematic?
Intracapsular fractures are likely to disrupt the ascending cervical branches of the medial femoral circumflex artery. Due to the inability of the artery in the ligament to the head of femur to sustain the metabolic demand of the femoral head, there’s a high risk of avascular necrosis of the bone. The risk is increased if the fracture is displaced
Why are extra capsular fractures less problematic?
The ascending cervical branches of the MFCA to the femoral head is likely to remain intact
Why is the limb shortened, abducted and externally rotated in a displaced fractured neck of femur?
Shortened - strong muscles of the thigh (flexors, adductors and extensors) pull the distal fragment of the femur upwards
Externally rotated - the fractured neck of femur allows the shaft of the femur to move independently of the hip joint; the axis of rotation of the femur that normally passes through the head shifts to pass through the greater trochanter and along the long axis of the femoral shaft. The iliopsoas now acts as an external rotator of the femur because of the fractured neck
Abducted - the strong abductors that attach to the greater trochanter abduct the femur distal to the fracture site
In which direction are most hip dislocations?
Most hip dislocations are posterior. The most common cause is the knee impacting the dashboard during a road traffic collision..
What position will the affected limb of a posterior hip dislocation be in?
The affected limb will be in a position of flexion, adduction and internal rotation.
A sciatic nerve palsy is present in some cases
What position will the affected limb of an anterior hip dislocation be in?
The affected limb is held in a position of external rotation with mild flexion and abduction.
Femoral nerve palsies can be present but are uncommon.
Why does shortening and internal rotation of the limb occur after posterior dislocation of the hip?
Shortening - 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
Internally rotated - the anterior parts of the gluteus medius and minimus pull on the posteriorly-displaced greater trochanter and cause the femur to rotate internally.
