Hip dislocation

Case 1: Posterior Hip Dislocation

A 35-year-old male presents to the emergency department after a high-speed motor vehicle accident. He complains of severe pain in his left hip and is unable to move his leg. On examination, the left lower limb is shortened, internally rotated, and adducted. Initial X-rays confirm a hip dislocation.

What is the most likely type of hip dislocation in this patient?
A) Anterior Dislocation
B) Posterior Dislocation
C) Inferior Dislocation
D) Superior Dislocation
E) Central Dislocation

Answer: B) Posterior Dislocation
Explanation:

Posterior hip dislocation is the most common type (90% of cases) and typically results from a dashboard injury, where a force is applied to a flexed knee, transmitting energy to the hip.
Classic clinical presentation: shortening, adduction, and internal rotation of the affected limb.

Case 2: Hip Joint Stability

A 40-year-old female is undergoing a total hip arthroplasty (THA). The surgeon explains that several structures contribute to hip joint stability.

Which of the following is the primary stabilizing factor of the native hip joint?
A) Labrum
B) Capsule
C) Iliofemoral ligament
D) Bony fit of the femoral head and acetabulum
E) Muscular support

Answer: D) Bony fit of the femoral head and acetabulum
Explanation:

The deep congruency of the femoral head within the acetabulum provides the primary stability.
Ligaments (especially the iliofemoral ligament) and the capsule offer additional support but are secondary stabilizers.
The labrum deepens the socket and provides a suction seal effect but does not contribute as significantly to stability as the bony fit.

Case 3: Imaging for Avascular Necrosis (AVN) Post-Hip Dislocation

A 28-year-old athlete sustained a hip dislocation while playing soccer. The dislocation was reduced within 6 hours. Six months later, he presents with increasing groin pain. X-rays are inconclusive for AVN.

Which imaging modality is most sensitive for detecting AVN in this patient?
A) X-ray
B) CT scan
C) MRI
D) Ultrasound
E) Bone scan

Answer: C) MRI
Explanation:

MRI is the most sensitive imaging modality for early detection of AVN, as it detects marrow changes before they are visible on X-rays.
X-rays may show late-stage AVN with crescent sign or subchondral collapse.
CT scan is useful for assessing structural integrity but is not as sensitive as MRI for early AVN.

Case 4: Initial Management of Hip Dislocation

A 45-year-old male presents with a traumatic posterior hip dislocation following a fall from a height. There is no associated acetabular fracture.

What is the initial treatment of choice?
A) Open reduction
B) Closed reduction under anesthesia
C) Immediate surgery
D) Traction for 4-6 weeks
E) Observation with analgesia

Answer: B) Closed reduction under anesthesia
Explanation:

Closed reduction under general anesthesia or sedation is the first-line treatment for a dislocated hip.
Open reduction is only indicated if closed reduction fails or if there is an associated fracture blocking reduction.
Delayed reduction (>6 hours) increases the risk of AVN.

Case 5: Indications for Surgery in Hip Dislocation

A 32-year-old patient presents with a posterior hip dislocation following a motorcycle accident. Closed reduction is attempted, but the joint remains incongruent on post-reduction CT scan.

What is the next step in management?
A) Repeat closed reduction
B) Non-weight-bearing for 6 weeks
C) Surgical intervention
D) Traction therapy
E) Physical therapy

Answer: C) Surgical intervention
Explanation:

Surgery is indicated for hip dislocations with non-concentric reduction, loose bodies, or associated fractures.
Persistent joint incongruity on post-reduction imaging suggests soft tissue interposition or fracture fragments, requiring open reduction.

Case 6: Complications of Delayed Hip Reduction

A 50-year-old patient presents with a neglected posterior hip dislocation, which has been unreduced for 48 hours.

What is the most serious complication associated with delayed reduction?
A) Sciatic nerve injury
B) Avascular necrosis (AVN)
C) Myositis ossificans
D) Chronic instability
E) Recurrent dislocation

Answer: B) Avascular necrosis (AVN)
Explanation:

AVN is the most serious complication, occurring due to disruption of the medial circumflex femoral artery supplying the femoral head.
The risk of AVN significantly increases if reduction is delayed beyond 6 hours.
Other complications like sciatic nerve injury and chronic instability may occur but are less devastating than AVN.

Case 7: Reduction Techniques in Hip Dislocation

A 25-year-old male presents with a posterior hip dislocation. The treating physician decides to attempt a closed reduction using a technique where the patient is placed prone on a stretcher with the leg hanging off, allowing gravity to assist the reduction.

Which reduction technique is being used?
A) Allis Method
B) Bigelow-Keverse Method
C) Stimson Gravity Method
D) Kocher-Langenbeck Method
E) Ludloff’s Maneuver

Answer: C) Stimson Gravity Method
Explanation:

The Stimson method involves placing the patient prone on a stretcher, allowing gravity to assist while gentle traction is applied.
The Allis method is done with the patient supine, using longitudinal traction.
Kocher-Langenbeck refers to a surgical approach for hip dislocations, not a reduction technique.

Case 8: Mechanism of Posterior Hip Dislocation

A 40-year-old male presents with a hip dislocation following a car accident. He was sitting in the front seat with his knee flexed when another vehicle struck from the front.

What is the most likely mechanism of injury?
A) Fall on the side
B) Dashboard injury
C) Direct blow to the greater trochanter
D) Hyperextension injury
E) Axial loading in abduction

Answer: B) Dashboard injury
Explanation:

A dashboard injury occurs when a force is transmitted through the flexed knee, driving the femoral head posteriorly out of the acetabulum.
This mechanism is classic for posterior hip dislocations and may be associated with acetabular fractures.

Case 9: Clinical Presentation of Posterior Dislocation

A 55-year-old male presents with a suspected hip dislocation after a fall. His left leg is shortened, adducted, and internally rotated.

Which type of dislocation does this presentation suggest?
A) Anterior dislocation
B) Posterior dislocation
C) Inferior dislocation
D) Central dislocation
E) Superior dislocation

Answer: B) Posterior dislocation
Explanation:

Posterior dislocations present with shortening, adduction, and internal rotation.
Anterior dislocations show external rotation and abduction.

Case 10: Surgical Approach for Posterior Hip Dislocation with Fracture

A 38-year-old male with a posterior hip dislocation and acetabular wall fracture requires open reduction and fixation.

Which surgical approach is most appropriate?
A) Smith-Peterson
B) Kocher-Langenbeck
C) Hardinge
D) Watson-Jones
E) Ilioinguinal

Answer: B) Kocher-Langenbeck
Explanation:

The Kocher-Langenbeck approach is the gold standard for posterior acetabular fractures.
Smith-Peterson is used for anterior fractures.

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