CASE 31 traumatic hip dislocations

 

A 53-year-old male arrives in the trauma bay with a GCS 15 and hemodynamically stable following a high-speed motor vehicle crash. He is complaining of severe right hip pain and is unable to move his right lower extremity. You note that his leg is shortened, slightly flexed, internally rotated, and adducted. He has symmetric pulses, and he is neurologically intact throughout his extremity. He has a normal examination otherwise. As part of the standard Advanced Trauma Life Support

algorithm, an an AP pelvis is obtained seen in Figure 6–33.

 

 

 

Figure 6–33

 

What do you do next?

1. Obtain a CT scan to evaluate for incarcerated fragments and acetabular fracture pattern

2. Emergent hip reduction prior to further pelvic imaging

3. Obtain ABI

4. Proceed directly to OR for open reduction of hip and internal fixation of acetabulum

5. Admit the patient to the floor for closed reduction under anesthesia in the morning

Discussion

The correct answer is (B). This presentation is classic for a posterior hip dislocation occurring during a motor vehicle crash and is often called a “dashboard injury” due to the axially directed force that is transmitted from the dashboard of a vehicle through the knees with the hips flexed and adducted as is normal while sitting in a vehicle. As a result, ipsilateral knee injuries are common. In an otherwise stable patient without associated femoral neck fracture, closed reduction of the dislocated hip should be attempted urgently regardless of acetabular fracture. This is performed in order to decrease the incidence of avascular necrosis, which can be as high as 15%, and chondral damage to the femoral head. However, if vascular injury is suspected, obtaining prereduction ABIs should be performed as part of a

thorough neurovascular examination. Due to the high trait of sciatic nerve injuries (more commonly the peroneal division), a thorough neuro examination should be conducted pre- and postreduction. Furthermore, an attempt at closed reduction should be performed prior to proceeding to the OR for open reduction.

After completing the remainder of the ATLS protocol, you reduce the hip and obtain the AP pelvis seen in Figure 6–34.

 

 

 

Figure 6–34

 

What is the next appropriate step?

1. MRI of hip

2. CT pelvis with intravascular contrast

3. CT pelvis without contrast

4. Repeat reduction attempt

5. Judet views of pelvis to evaluate acetabulum fracture

 

Discussion

The correct answer is (C). Following closed reduction of a hip with an associated acetabulum fracture, a CT pelvis without contrast should be ordered in order to evaluate for incarcerated fragments, malreduction, impaction of the acetabulum and/or femoral head, and overall fracture pattern. Doing so will also allow you to better evaluate the acetabulum fracture pattern. MRI or ultrasound of the hip is not indicated in this situation and, although Judet views are needed, these should be ordered following evaluation for incarcerated fragments. IV contrast is not needed in this situation as the patient has no evidence of vascular injury and will not

provide you with meaningful information.

During the CT scan, a small subdural hematoma is also discovered and the patient is taken to the ICU for further care. You notice on the CT pelvis without contrast that his hip is not concentrically reduced. You subsequently repeat the reduction attempt and are unable to adequately obtain a well-reduced hip due to the continued posterior subluxation of the hip. You then place a distal femoral traction pin and apply traction, which keeps the hip concentrically reduced.

What structure is most at risk with distal femoral traction pin placement?

1. Peroneal nerve

2. Femoral artery

3. Medial geniculate artery

4. Popliteal artery

5. Sciatic nerve

 

Discussion

The correct answer is (C). When placing a distal femoral traction pin, one must be aware of surrounding neurovascular structures. Traditional teaching has stated that the femoral artery at Hunter’s canal is most at risk when placing a distal femoral pin; however, anatomic studies have shown that the medial geniculate artery is most at risk when placing this pin at a distance between 9 and 12 mm. The femoral artery can be found at approximately 29 to 35 mm from the course of the traction pin.

Five months after open reduction and internal fixation of his posterior acetabulum fracture, the patient presents to clinic with continued right hip pain deep in his groin that is worse with internal rotation and walking up stairs. Repeat radiographs of his hip reveal a well-healed acetabular fracture and sclerosis of his femoral head.

What is the most likely etiology of his hip pain?

1. Posttraumatic osteoarthritis

2. Avascular necrosis of the femoral head

3. Femoroacetabular impingement

4. Missed ligamentum teres avulsion fracture

5. A or B

 

Discussion

The correct answer is (E). Commonly associated injuries following a posterior hip

dislocation include posttraumatic osteoarthritis (PTOA), femoral head osteonecrosis, sciatic nerve injury, ipsilateral knee injuries, and recurrent dislocations. PTOA has been noted to occur between 20% and 40% of hip dislocations with a higher incidence occurring with associated acetabular fractures. A time-dependent association has been noted with AVN of the femoral head in both animal and human models with times to reduction greater than 6 to 8 hours and 12 hours, respectively, showing increased incidence of AVN of up to 40%. This is primarily due to disruption of the blood supply to the femoral head, primarily the medial femoral circumflex artery.

 

Objectives: Did you learn...?CASE                               31 traumatic hip dislocations

 

 

Diagnostic and treatment considerations in posterior hip dislocations? Anatomic considerations of distal femoral traction pin placement?

 

Complications of traumatic hip dislocations?