Lower limb Trauma Structured oral examination question 6
A 50-year-old woman, front-seat passenger, was involved in a head-on high speed car collision. In A&E she was diagnosed with a right hip dislocation.
Minute 1
EXAMINER: What will be your management?
CANDIDATE: I would assess and resuscitate the patient along ATLS principles, exclude any associated injuries. I would examine the lower right leg looking at alignment, position and document neurovascular status especially of the sciatic nerve. With the mechanism of injury it is likely to be posterior dislocation with often an associated acetabular rim or femoral neck fracture. In a posterior dislocation the leg is usually shortened and internally rotated, whilst with anterior dislocations the leg is externally rotated and abducted.
EXAMINER: It appears to be an isolated injury with paraesthesia in the sole of the foot, however motor function is intact. How will you manage this further?
CANDIDATE: A traumatic hip dislocation is a surgical emergency because of the risks to the vascularity of the femoral head, danger of chondrolysis as well as pressure effects on the surrounding soft tissues especially neurovascular structures.
The paraesthesia in the foot is an indication of pressure or traction involving the sciatic nerve. I would arrange urgently for the patient to go to the theatre the same night. I would get an urgent CT scan performed provided it did not delay surgery; inform theatres, the anaesthetic team and the ward. I would
arrange for haematological and biochemical investigations including crossmatch. I would take an informed consent for a closed or open reduction under general anaesthesia.
Minute 2
EXAMINER: There is delay in getting the CT scan and you take her to the operating theatre. How will you reduce the hip?
CANDIDATE: I would attempt closed reduction under general anaesthesia. I would position her supine on the table with the table height as low as possible. I would request the anaesthetist to use muscle relaxant to make it easier to reduce the hip.
I would stand on the side of the dislocated hip and have the image intensifier (II) come in from the opposite side. My assistant would be on the opposite side towards the head end of the patient to hold down and stabilize her pelvis when
I attempt manipulation. I would screen her first before attempting reduction to exclude a femoral neck fracture and assess the acetabulum using Judet views. If it is a posterior dislocation, I would gently apply traction on the hip (in-line) and then gradually flex the hip and the knee maintaining traction. I would check reduction under II and also check once again for any associated fractures.
EXAMINER: You manage to reduce the hip and get this radiographic image. What are your thoughts? (Figure 8.7.)
CANDIDATE: In this II view of the right hip, the femoral head appears to be in the acetabulum but is incongruent. I would like to confirm this on lateral radiograph. The femoral head is inferiorly subluxed and there appears to be a bony fragment in the hip joint superiorly and another one inferiorly. There is
Figure 8.7 Image intensifier (II) image right hip.
one more fragment on the superolateral lip of the acetabulum. The bony fragments are most likely to be from the acetabulum, however femoral head fragments need to be ruled out.
Minute 3
EXAMINER: How will you assess this hip further?
CANDIDATE: Peroperatively I would screen the hip in AP and lateral views as well as obtaining Judet views to assess the anterior and posterior walls and columns. In addition, I would assess the hip for stability. A CT scan will be useful to delineate this further, if it has not already been done.
EXAMINER: You obtain a CT scan in the morning and this is one of the sections. What do you think? (Figure 8.8.)
CANDIDATE: [Note: just comment on what you have rather than ask for more images.] In this axial section of the pelvis at the level of the hip joints, I note that the femoral head on the injured side is at a different height to the opposite hip. There is a bony fragment trapped in the hip joint as well as a bony fragment lying posterior to the hip. It looks like a fracture dislocation with compromise of the acetabular wall postero- superiorly. I would need to study the whole CT sequence to ascertain the extent of damage.
EXAMINER: How will you deal with the bony fragment in the hip joint?
CANDIDATE: This depends on a number of factors including the exact original site of the bony fragment, the size of it, weightbearing dome state and the stability of the hip. The options for a bony fragment trapped in the hip joint are to remove it or to retrieve and fix it. If the fragment is quite small and does not affect hip stability or the weightbearing dome then it can be removed arthroscopically. However, if it compromises the weightbearing area of the hip or stability then I would retrieve it and fix it. It will have to be an open procedure though reports of arthroscopic intervention have been published. [Note: If the candidate does not have sound hip arthroscopy knowledge, then the safe option is open procedure and stay clear of hip arthroscopy.]
Minute 4
EXAMINER: You find that it is the postero-superior lip of the acetabulum. Which approach will you use to fix the fracture?
Figure 8.8 CT axial view pelvis.
CANDIDATE: The approach depends on where the bony fragment is arising from. If it is postero-superior or posterior, I would use a posterior approach. I would position the patient on the fracture table in lateral decubitus. To preserve the blood supply to the femoral head, I would remove the fractured loose body arthroscopically [however, see the argument above]. In the posterior approach to the hip one needs to respect the blood vessels supplying the femoral head and therefore not take down the quadratus or the short rotator muscles. I would retract the gluteus medius superiorly, identify the capsule and dissect superiorly to identify the fractured rim of the acetabulum. I would reduce the fragment anatomically under image intensifier screening and secure it with 2–3 partially threaded cannulated screws making sure that the screws do not penetrate the hip joint.
Minute 5
EXAMINER: What are the risks with posterior dislocation of the hip?
CANDIDATE: Immediate complications are neurovascular damage (10% with posterior dislocation), fractures and haemorrhage. Intermediate risks are chondrolysis, post- reduction neurological damage, avascular necrosis, intra- articular loose bodies and hip instability. Late complications are pain and post-traumatic arthritis.
EXAMINER: What other injuries are associated with this injury pattern?
CANDIDATE: This is determined by the direction of forces and may include patella fracture, PCL rupture, femoral fracture, femoral neck and head fractures.
[Note: The candidate is smiling as the examiner has run out of questions on his crib sheet!]
