Hip and shoulder dislocations Flashcards
Describe the three types of hip dislocation [2]
Which is most common? [1]
Posterior dislocation:
- Accounts for 90% of hip dislocations.
- The affected leg is shortened, adducted, and internally rotated.
Anterior dislocation:
- The affected leg is usually abducted and externally rotated. No leg shortening.
Central dislocation
Hip dislocations can be classified into two primary categories: [cause]
Hip dislocations can be classified into two primary categories: traumatic and atraumatic.
Describe the subtypes of anterior dislocations with regards to the patient presentation and palpation findings:
- Obturator dislocation [2]
- Pubic dislocation [2]
Obturator dislocation:
- Patient presentation: affected limb is abducted, externally rotated, and mildly flexed.
- Palpation findings: Prominence of the greater trochanter laterally; femoral head palpable in the medial thigh region near the obturator foramen.
Pubic dislocation:
* Patient presentation: Affected limb is abducted, externally rotated, and significantly flexed at both the hip and knee joints.
* Palpation findings: Femoral head palpable in the inguinal region; lesser trochanter prominence may be appreciated posteriorly.
Describe the subtypes of posterior dislocations with regards to the patient presentation and palpation findings:
- Iliac dislocation [2]
- Ischiatic dislocation [2]
Subtype: Iliac
* Patient presentation: Affected limb is adducted, internally rotated, and mildly flexed at the hip joint.
* Palpation findings: Prominence of the greater trochanter posteriorly; femoral head palpable in the buttock region near the sciatic notch.
Subtype: Ischiatic
* Patient presentation: Affected limb is adducted, internally rotated, and significantly flexed at both the hip and knee joints.
* Palpation findings: Femoral head palpable in proximity to the ischial tuberosity; lesser trochanter prominence may be appreciated anteriorly.
How do you manage hip dislocations [4]
- ABCDE approach.
- Analgesia
- A reduction under general anaesthetic within 4 hours to reduce the risk of avascular necrosis.
- Long-term management: Physiotherapy to strengthen the surrounding muscles.
Describe the pathoanatomy of a shoulder dislocation [1]
What is a subluxation? [1]
Shoulder dislocation is where the ball of the shoulder (head of the humerus) comes entirely out of the socket (glenoid cavity of the scapula).
Subluxation refers to a partial dislocation of the shoulder. The ball does not come fully out of the socket and naturally pops back into place shortly afterwards.
What are the main causes of anterior and posterior shoulder disclocations [2]
Describe the position the shoulder / arm is in when force occurs [2]
Anterior shoulder dislocation:
- include high-energy sporting collisions and falls; a force to an abducted, externally rotated and extended arm
- occurs when the arm is forced backwards
Posterior dislocation:
- force to the anterior surface of the shoulder, or axial loading of an adducted and internally rotated arm. Due to 3Es:
* Epilepsy - seizures are the most common cause. The dislocation occurs either from a fall itself or from strong muscular contractions that may occur during the clonic phase
* Electrocution
* Ethanol - typically following a fall
Label this diagram [5]
Label this diagram [5]
Anterior or posterior dislocation? [1]
Figure 5. Anterior shoulder dislocation
What sign on an x-ray indicates posterior shoulder dislocation? [1]
The ‘light bulb sign’ suggests a posterior shoulder dislocation (Figure 3). The Y-view can help differentiate between anterior and posterior dislocations.
Which structure surrounds the glenoid cavity? [1]
The glenoid labrum surrounds the glenoid cavity.
Describe associated fractures that occur in 25% of dislocations [4]
Fractures of the tuberosity or surgical neck:
- these dislocations may not be suitable for closed reduction in the emergency department
Bankart lesions:
- are tears to the anterior portion of the labrum
- these develop when the glenoid labrum is damaged; they may sometimes be associated with an avulsion fracture (bony Bankart)
- These occur with repeated anterior subluxations or dislocations of the shoulder.
Hill-Sachs lesions:
- compression fractures of the posterolateral humeral head
- commonly occurring in anterior dislocations
- shoulder dislocates anteriorly, the posterolateral part of the humeral head impacts with the anterior rim of the glenoid cavity
Reverse Hill-Sachs lesions:
- an impaction fracture of the anteromedial humeral head commonly occurring in posterior dislocations
Shoulder dislocations commonly cause axillary nerve damage.
Which nerve roots does the axillary nerve come from? [2]
How does this manifest in a patient?
Axillary nerve damage is a key complication. The axillary nerve comes from the C5 and C6 nerve roots.
Damage causes a loss of sensation in the “regimental badge” area over the lateral deltoid.
It also leads to motor weakness in the deltoid and teres minor muscles.
TOM TIP: Axillary nerve damage is a common association with anterior dislocations to remember for your exams. This knowledge may be tested in MCQs, where you are asked to identify the nerve, location of sensory loss or muscle affected by weakness.
Describe what is meant by the Apprehension test
The apprehension test is a special test to assess for shoulder instability, specifically in the anterior direction.
It is likely to be positive after previous anterior dislocation or subluxation of the shoulder. This may be performed after recovery from any acute injuries.
- The patient lies supine.
- The shoulder is abducted to 90 degrees, and the elbow is flexed to 90 degrees.
- The shoulder is then slowly externally rotated in this position while watching the patient
- .As the arm approaches 90 degrees of external rotation, patients with shoulder instability will become anxious and apprehensive, worried that the shoulder will dislocate.
There is no pain associated with the movement, only apprehension!
Which type of fracture are labelled as A & B? [2]
A: Hill-Sachs
- compression fractures of the posterolateral humeral head commonly occurring in anterior dislocations
:
B: Bankart
A patient suffers from a shoulder dislocation.
What is the associated defect occuring?
Fractures of the tuberosity or surgical neck
Bankart lesions
Hill-Sachs lesions
Reverse Hill-Sachs lesions
A patient suffers from a shoulder dislocation.
What is the associated defect occuring?
Fractures of the tuberosity or surgical neck
Bankart lesions
Hill-Sachs lesions
Reverse Hill-Sachs lesions
What position is the arm in an anterior shoulder dislocation? [2]
Which bony landmark may appear prominent? [1]
Arm position:
* Slightly abducted
* Externally rotated
Acromion process may appear prominent, particularly in slim individuals
What position is the arm in an posterior shoulder dislocation? [2]
How does the shoulder change position? [2]
Which bony landmark may appear prominent? [1]
Arm position:
* Adducted
* Internally rotated
Shoulder position:
* The posterior shoulder will appear much more prominent than usual
* The anterior shoulder will appear more flattened than usual
Prominent coracoid process
If you had to describe the change in position of the shoulder in an anterior shoulder dislocation - what would it look like? [2]
If you had to describe the change in position of the arm in an anterior shoulder dislocation - what would it look like? [2]
Shoulder:
- loss of rounded appearance (humeral head) and sharp prominence of the acromion (“squaring”)
Arm:
- arm is abducted and externally rotated
What is an Acromioclavicular Joint Injury and how do you differentiate this from a shoulder dislocation? [2]
ACJ injuries involve disruption between the acromion and clavicle - hence they are sometimes referred to as ‘separated shoulders’; Injuries here are most commonly caused by a fall onto or direct blow to the shoulder.
Shoulder dislocations have displaced humeral head from glenoid socket
