1 General considerations topenlarge
A posterior column fracture originates at the greater sciatic notch, passes through the roof, or weight bearing dome, and exits through the obturator ring. The result is a complete detachment of the posterior column.
Occasionally the fracture is limited to the ischium.
Isolated posterior column fractures are rare (2.4% - 3.2% of acetabular fractures [ Matta, Letournel]) and are usually associated with a posterior dislocation of the hip. Even associated with a posterior wall fragment, the prevalence of posterior column fractures is low (3.4% [Matta, Letournel]).
The caudal fragment of the fracture is usually displaced posteriorly, medially, and internally rotated, as the posterior column rotates about the ischial tuberosity.
As the femoral head is driven through the posterior column and fractures it, it tends to open up the posterior column like a swinging door, so that its posterior edge rotates into the pelvis.
The superior gluteal vessels and nerve can be caught within the fracture line, if it crosses their path.
2 Joint distraction topenlarge
Traction on the femur, laterally or distally, increases the joint space.
This will help
- expose the joint
- remove loose fragments and
- reduce some marginal impaction fractures
Traction can be applied in several ways, including
- by hand (the “assistant-distractor”)
- with a femoral distractor
- with a traction table
Traction with a femoral distractor
One way to apply traction is with a large distractor. This avoids both constant pulling and use of the fracture table, but does limit mobility of the hip. Properly placed, the distractor may properly realign the femoral head.
Insert a 5 mm Schanz screw into the sciatic buttress proximally. Place a second Schanz screw into the femur at the level of the lesser trochanter.
Tension on the distractor can be adjusted as needed for visualization or reduction
3 Cleaning of the fracture site topenlarge
Clean and irrigate
Exposure is completed subperiosteally at the fracture site. If there is a posterior wall fragment, it may need to be retracted as part of the capsulotomy.
Clean and irrigate the fracture site in preparation for the direct reduction.
Remove loose bodies
Loose bodies should be identified on the preoperative CT scan. Their removal and cleaning of the joint is mandatory.
This must be rechecked to remove any fragments displaced into the joint during the previous steps.
4 Reduction of the femoral head topenlarge
A posterior dislocation of the femoral head is typically associated with the posterior column acetabular fracture. This should have been reduced provisionally as part of initial management. Depending upon the location of the posterior column fracture, the hip joint may be unstable. This instability requires surgical repair, as does displacement of the fracture. The unstable hip may redislocate during exposure and re-reduction will be necessary.
During definitive posterior column reduction, the femoral head must be properly reduced against the superior-anterior stable portion of the acetabulum. The femoral head thus becomes a template for proper posterior column reduction. Improper position of the head prevents satisfactory fracture reduction.
5 Reduction of the fracture topenlarge
With the femoral head properly reduced, the mobile inferior portion of the posterior column must be repositioned. This requires correction of its medial and distal displacement and internal rotation. Direct manipulation and provisional stabilization with clamps are to be used. Once a satisfactory provisional reduction is achieved and confirmed, definitive fixation is applied.
Ischial Schanz screw as a handle
A 5 mm Schanz screw is placed in the ischial tuberosity, aligned so it does not overhang the posterior column. This is a key aid for manipulating the free fragment.
Rotation and fine adjustment of this fragment is aided with a bone hook, sharp dental hooks, and/or ball spike pusher.
Manipulation with a hook placed as shown demonstrates mobility of the posterior column, and helps in the reduction. If reduction is difficult, check the fracture site for interposed debris.
Use of a Farabeuf clamp
This clamp has jaws shaped to fit around screw heads. It can be used to compress fracture surfaces with two properly placed 4.5 mm cortical screws. They should be securely placed, and a little prominent, to be grasped by the clamp.
Properly placed, this clamp can both derotate the posterior column, and approximate the fracture fragments.
Use of a Jungbluth clamp
The Jungbluth pelvic reduction clamp is a similar alternative, which requires a larger exposure and also depends upon proper screw placement so that the forces applied by the clamp correctly realign the fracture.
A proximal screw is placed in the superior portion of the iliac wing above the acetabulum.
A distal screw is placed in the posterior column above the ischial tuberosity.
Their positions determine the direction of applied force, and this must be perpendicular to the fracture plane.
Articular surface reduction
Reduction must be perfect. The posterior column fragment must be manipulated into anatomical alignment with instruments as described above. Manipulation of the T-handle-Schanz screw is a significant aid.
Pulling it posteriorly will help to close the fracture. Translation and rotation may require assisting instruments.
To mobilize the posterior column in cases older than 3 weeks, cut the sacrospinous ligament at its insertion. Alternatively osteotomize the ischial spine.
Examine the result
Examine the reduction by inserting a finger or an appropriate instrument along the quadrilateral plate.
With a satisfactory reduction, the quadrilateral surface should have no palpable gap or step-off.
Reduction can also be checked by opening the hip capsule with an incision parallel to the acetabular border, avoiding damage to the labrum. Inspection of the joint surface demonstrates reduction.
6 Fixation topenlarge
If possible, begin definitive fixation with an interfragmentary lag screw, placed from the distal fragment, into the posterior buttress of the ilium.
The gliding hole can be drilled before reduction to ensure its proper placement.
It is recommended to use a washer with the lag screw.
Alternative initial fixation
If a lag screw can not be inserted satisfactorily, a short plate across the fracture can be applied along the medial edge of the posterior column. This can be used to help obtain the reduction.
A second plate along the acetabular margin will also be necessary, as described below.
Contour the plate with a template
A 3.5 mm reconstruction plate will be applied.
To contour it properly, use an aluminum template, bent to fit the pelvis in the chosen location. Final plate apposition, and fracture compression is achieved as the screws are tightened to bring it against the bone.
Contouring of the plate with a plastic model
Understanding the proper plate position and contouring can be aided by rehearsal using the malleable template and a plastic bone model, on which the fracture plane has been carefully drawn.
Apply the reconstruction plate
Definitive stabilization is obtained by adding a 3.5 mm reconstruction plate spanning the posterior column and achored securely to ilium and ischium. This follows the medial border of the retroacetabular surface.
Screws overlying the acetabulum may be omitted.
Result in a fracture in which a plate was applied along the medial edge of the posterior column for initial fixation.
Pitfall: Injury to gluteal vessels and nerve
Proximally, retraction and plate and screw placement may result in neurovascular injury. Careful retraction and attention to plate location are essential to protect these fragile structures.