Open Reduction and Internal Fixation of Posterior Wall Acetabular Fractures
Lawrence X. Webb, MD, MBA
Dr. Webb or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of the Musculoskeletal Transplant Foundation; serves as a paid consultant to or is an employee of Biocomposites; has received nonincome support (such as equipment or services), commercially derived honoraria, or other non-research-related funding (such as paid travel) from Kinetic Concepts, Doctors Group, Smith & Nephew, Stryker, and Synthes; and serves as a board member, owner, officer, or committee member of the Orthopaedic Trauma Association Southeastern Fracture Consortium Foundation.
INTRODUCTION
Classification
Fractures of the acetabulum are classified according to Letournel into two main groups: elementary fractures and associated fractures.1 The classification is morphologic and is based on Judet oblique view radiographs.2 Each group has five types (Figure 1). Posterior wall fractures are one of the elementary types; they also may occur as a component in two of the associated types—posterior column and posterior wall fractures, and transverse and posterior wall fractures. This chapter focuses on elementary posterior wall fractures. These are the most common of the 10 types, accounting for approximately one-fourth to one-third of all acetabular fractures.3,4
Associated Injuries
Although posterior wall fractures are occasionally seen in isolation, these fractures are often the result of high-energy trauma, and associated injuries are not uncommon. Some of these are life-threatening and should be identified and managed at the time of presentation, using ATLS (Advanced Trauma Life Support) protocols.5
VIDEO 71.1 Posterior Wall Fracture-Dislocation: Reduction and Traction Pin Placement. Lawrence X. Webb, MD; John M. Tabit, DO (4 min)Video 71.1
The mechanism of injury is thought to be axial loading of the femur with the hip in the flexed position.4 This occurs in motor vehicle accidents with frontal impact when the knee strikes the dashboard. The force is driven via the flexed hip against the posterior wall of the acetabulum, producing the fracture. The size of the fragment is thought to be determined by the degree of abduction or adduction at the time of impact.4 With displacement of the fractured posterior wall, the femoral head is unconstrained, and it subluxates or dislocates posteriorly in 78% to 86% of the cases.4,6 Also, as the femoral head displaces posteriorly, it may impact the edge of the fractured acetabular articular surface, resulting in a marginal impaction fracture. This accompanying fracture occurs in 27% to 46% of posterior wall fractures.4,6 Other potential associated injuries include fracture of the femoral head, femoral neck, and femoral shaft as well as ligamentous injury to the knee.
PREOPERATIVE IMAGING
In patients who present with multiple injuries, careful scrutiny of the initial pelvic radiograph will usually show the fracture. The fracture can be clearly seen and classified on Judet oblique views, particularly the obturator oblique view. CT helps in assessing the femoral head, the size and extent of segmentation or comminution of the posterior wall fragment(s), the size and location of intra-articular fragments, and associated marginal impaction fractures (Figure 2).
PROCEDURE
Equipment/Implants
The following instruments are commonly used in the open reduction and internal fixation (ORIF) of posterior wall acetabular fractures:
A self-retaining Charnley retractor
Schanz pins (5.0-mm), hand chuck, small femoral distractor
Sciatic nerve retractor, cobra retractor, Taylor retractor
Adhesive plastic strips to temporarily hold retractors
Standard and pituitary rongeurs (helpful in extracting joint fragments and debris)
Cancellous bone allograft or bone graft substitute (to address marginal impaction)
A ball-spike pusher
1.5-and 2.0-mm Kirschner wires (K-wires)
Spring plates
FIGURE 1 The Letournel classification of acetabular fractures.
3.5-mm reconstruction plates with corresponding aluminum templates and plate benders
C-arm (preferably situated on the side of the table opposite the surgeon)
Early Management of Dislocation
Reduction of a hip dislocation in a timely fashion is important for pain relief as well as femoral head blood flow considerations. Protracted time (longer than 12 hours) with the hip dislocated is thought to have a deleterious effect on femoral head blood supply.6,7,8,9 The reduction can be accomplished with conscious sedation in the emergency department or trauma bay or, if need be, with a general anesthetic with muscle relaxation in the operating room. Once the joint is reduced and this is verified on radiographs, the surgeon may choose to maintain the knee in extension with a splint (knee immobilizer).10 For reductions that are unstable with large displaced fragments or those with intra-articular fragments, distal femoral skeletal pin traction should be used. In these instances, traction protects the head of the femur from the pressure of a fracture edge or an incarcerated intra-articular fragment that might otherwise focus localized heightened stress on the articular cartilage of the femoral head and corresponding acetabular surface.
 FIGURE 2 Axial CT scan of the pelvis clearly shows a marginal impaction fracture (arrow). |
Preoperative Planning and Patient Positioning
The nature of the posterior wall fragments, including their displacement, can be ascertained by study of the CT scan. This morphology can vary significantly.
The Kocher-Langenbeck approach is used. For this approach, the patient is placed in either the lateral
decubitus position or the prone position. In either case, the knee is maintained in the flexed position to relax the sciatic nerve (Figure 3).
decubitus position or the prone position. In either case, the knee is maintained in the flexed position to relax the sciatic nerve (Figure 3).
 FIGURE 3 Illustrations show patient positioning for ORIF of posterior wall acetabular fractures. A, The lateral decubitus position. A Mayo stand, upon which the padded knee and leg rest, can be adjusted to effect hip adduction/abduction. Varying the height of a soft bump placed beneath the foot/ankle with the knee flexed is used to effect rotation. B, The prone position. Skeletal traction through a transfixing pin in the distal femur is used. The knee is maintained in the flexed position as shown. The unaffected leg is kept in extension. The patient’s thighs and the peroneal post are appropriately padded. (Panel B reproduced with permission from Siegel J, Templeman DC: Open reduction and internal fixation of the posterior wall of the acetabulum, in Tornetta P III, Williams GR, Ramsey ML, Hunt TR III, Wiesel SW, eds: Operative Techniques in Orthopaedic Trauma Surgery. Philadelphia, PA, Lippincott Williams & Wilkins, 2011, pp 315-325.) |
With the patient in the lateral decubitus position, neutral adduction/abduction can be facilitated by placing a padded Mayo stand beneath the flexed knee (Figure 3, A). Internal and external hip rotation can be achieved by raising or lowering the padded ankle and foot (while the knee is flexed and the skin is protected) using folded towels on a Mayo stand.
With the patient in the prone position, the use of a fracture table with maintenance of skeletal traction through a distal femoral transfixing pin is recommended, with the knee flexed to 80° using a fracture table boot over an appropriately padded foot and ankle (Figure 3, B). The radiopacity of gel rolls is a potential problem for C-arm imaging, so folded sheets should be used instead.11 Care should be taken to appropriately pad the peroneal post on the fracture table to minimize the likelihood of a pudendal nerve palsy. The contralateral foot and ankle are padded well and placed in a fracture table boot with the knee extended. Both thighs are appropriately padded.
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