1 Principles topenlarge
Definition: Posterior column/posterior wall fracture
These fractures are a combination of the two elemental fracture patterns: posterior column and posterior wall.
The posterior column component is often nondisplaced, and the wall fracture is the more obvious component.
Complex fracture of the posterior wall and dislocation of the femoral head associated with nondisplaced fracture of the posterior column.
Associated posterior column/wall fracture pattern with displacement of both components.
Note that the posterior column is comminuted, as well as displaced.
Mechanism of the injury
All posterior wall fracture types, elemental and associated, are commonly caused by a blow to the flexed knee on the dashboard in a car accident.
The knee is also at risk of injury, such as patellar fracture or posterior cruciate ligament tear.
When a posterior dislocation is associated with a posterior wall fracture, open reduction and internal fixation is virtually always indicated because the posterior wall defect renders the hip unstable.
Posterior dislocations also increase the risks of sciatic nerve injury and of avascular necrosis of the femoral head.
Any dislocation should have been reduced as soon as possible after the patient’s arrival in hospital. This reduction should be maintained, with traction if necessary, until open reduction internal fixation.
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
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.
Whenever the femoral head is dislocated, its reduction into the acetabulum takes priority, even if posterior column displacement is significant. Often the posterior column fracture alignment will improve once the head is relocated.
5 Posterior column: Reduction of the fracture top
Posterior column reduction is done before that of the posterior wall. The displaced posterior wall fragment makes it easier to see the column fracture.
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
Displace the wall fragment as necessary to see the posterior column 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.
If the posterior column is satisfactorily reduced, it will be possible to place the posterior wall fragment into its bed anatomically, and this should be confirmed.
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 Posterior column: Preliminary fixation topenlarge
If possible, begin posterior column 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 inserted 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 to fix the wall fragment, as well as increasing stability of the column fixation.
Place the medial plate out of the way of the lateral plate.
7 Posterior wall: Reduction of the fracture topenlarge
Use a ball spike pusher or pelvic reduction forceps
Reposition the wall fragment in its bed and compress it into place. Remember that this may be more difficult should the fragment be comminuted.
A ball spike pusher can be used to compress and maintain the reduction until definitive fixation.
It may be necessary to stabilize the fragment with a K-wire or two before proceeding.
Alternatively, this can be done with a pelvic reduction forceps with pointed ball tips.
One tip is inserted through the greater sciatic notch, against the quadrilateral lamina. The other is placed on the wall fragment and the clamp is tightened.
Confirm reduction before proceeding.
It is important to avoid placing fixation screws into the hip joint. Thus the surgeon must remember the joint location which will be obscured by posterior wall reduction.
One may even consider drilling the posterior wall gliding holes before reduction.
Elevate impacted fragments
Remember that any impaction must be corrected before the posterior wall can be reduced.
Typically, the femoral head, in its reduced position, is a helpful template for reduction of impacted areas.
Carefully elevate and mold the impacted bone against the femoral head, packing graft into the created defect.
When elevating impacted joint surface, use a small osteotome and create a thick enough fragment, including impacted cancellous bone so that the joint surface does not crumble.
Fill the defect
Fill the defect zone with cancellous autograft or a bone substitute.
Use a K-wire, a screw, or a resorbable pin(s) to hold the reduction.
8 Posterior wall: Preliminary fixation topenlarge
Fix posterior wall fragment with lag screw
If the posterior wall fragment is large enough, it should be fixed into its bed with a lag screw.
Before turning back the posterior wall fragment, it is important to assess the quality of the reduction. After satisfactory reduction, insert the lag screw, carefully avoiding the joint.
This shows fixation of a large posterior wall fragment with 2 screws.
Typically the medial edge of the fragment is very thin. Screws should be placed
laterally enough to capture a thicker part of the bone, while carefully
avoiding the joint.
Predrilling the fragment before reduction may be helpful. Washers may be needed.
These lag screws may be in the way of the posterior plate. If possible, place them medially to it, or place the plate over the screw heads.
9 Definitive fixation topenlarge
Contour the plate
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.
Apply the reconstruction plate
Definitive stabilization is obtained by adding a 3.5 mm reconstruction plate spanning the posterior column and anchored securely to ilium and ischium. This follows the lateral border of the retroacetabular surface, and should be positioned for maximal support of the posterior wall fragment(s).
Screws overlying the acetabulum may be omitted, but if at all possible, at least one screw, in addition to the plate, should fix significant wall fragments.
Remember that this plate supports both the posterior column fracture and the posterior wall. It must be contoured appropriately, applied under tension with tension by screw position and direction. Thus tightening proximal and distal screws should complete the contouring of the plate and compress it against the underlying bone.
Alternative: Screw for wall fragment through plate
Sometimes the definitive screw for a posterior wall fragment can best be inserted through the plate after it is applied.
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.
Pitfall: Intraarticular screws
It is vital that all the screws avoid the hip joint. The best way to confirm this is with intraoperative fluoroscopy. Check each questionable screw with the central ray directed along the screw axis. This should show the screw end-on, as a point, clearly outside the joint surface.
These x-rays show completed fixation of posterior column/wall associated fracture. For better access to the anterosuperior acetabular margin, a trochanteric osteotomy was used.