Fracture Characteristics
Definition
Associated fractures of the posterior column and posterior wall are partially articular fractures, characterized by a combination of a classical posterior column fracture and posterior wall fragment(s).
Associated fractures of the posterior column and posterior wall are rare injuries, similar to isolated fractures of the posterior column with a reported frequency of 5–6% of all acetabular fractures.1
The fracture characteristic is a summary of that described in ▶ 8 and ▶ 9. According to the fracture morphology, the posterior wall fragment(s) is located purely posterior, posteroinferior, or posterosuperior, respectively. The posterior column component can appear as an incomplete fracture or present with all typical fracture courses with or without involvement of the obturator foramen (see ▶ 9).
More often, the posterior column fracture is slightly displaced or incomplete and does not extend into the obturator foramen. Letournel therefore pointed out that this fracture type is primarily a fracture of the posterior wall and secondarily an additional posterior column fracture.2 Correspondingly, in the majority of cases, a posterior-cranial hip dislocation is present, whereas central or medial dislocations are exceptions.
10.2 Radiological Criteria
Pelvic anteroposterior (AP) view (▶ Fig. 10.1a). The ilioischial line is disrupted and the radiographic lines of the anterior column (anterior wall line and iliopectineal line) remain intact. The line of the anterior wall is often better visualized due to the lack of superimposition of the dorsal structures. The acetabular roof can be different compared to the uninjured side by displaced posterosuperior parts of the posterior wall fragment. The line of the posterior wall is disrupted. Depending on the extent of involvement of the quadrilateral surface, the teardrop figure may be altered. Frequently, there is a posterior-cranial hip dislocation; less commonly, a medial/central hip dislocation occurs.
Iliac oblique view (IOV) (▶ Fig. 10.1b). The IOV reveals the integrity of the anterior column structures and the most cranial and medial extent of the fracture. Fractures of the iliac wing or the anterior roof can be excluded. The posterior wall fragment(s) can be visualized as dense bone structures in projection to the iliac bone.
Obturator oblique view (OOV) (▶ Fig. 10.1b). The integrity of the iliopectineal line and the anterior wall is confirmed. The size of the posterior wall fragment(s) and the displacement of the posterior column fractures are best visualized.
Computed tomography (▶ Fig. 10.1c). CT is necessary to analyze the exact size of the posterior wall fragment(s) and to visualize intraarticular fragments and marginal impaction zones of the femoral head and/or the acetabular surface, the localization of articular surface involvement, and extent of posterior hip dislocation and the rotation of the fragments. A three-dimensional (3D)-CT is only necessary to give a better anatomical understanding of the fracture morphology.
Transition forms to other fracture types. Extended fractures involving the quadrilateral surface or with incomplete fracture lines extending to the anterior column can appear as transitions to associated transverse posterior wall fractures or “fractures of the posterior column with an anterior hemitransverse fracture.”2
Fig. 10.1 Associated fracture of the posterior column and posterior wall. (a) The pelvic anteroposterior view shows the column fracture (dotted line) and the small posterosuperior wall fragment (arrows). The typical spur in the true pelvis projection is clearly visible. (b) The ala and obturator oblique views show the typical posteromedial separation (black arrows) of the posterior column fragment and the small chiplike wall fragment (white arrows). (c) CT reveals the classical horizontal separation of the posterior column from the intact anterior column together with the small wall fragment. The schematic drawing represents the classical orientation of the fracture lines on axial CT slides. (d) 3D-CT confirms the fracture morphology.
10.3 Pathobiomechanics
The dashboard injury mechanism is appropriate to cause an associated fracture of the posterior column and posterior wall.
In the analysis by Dakin et al, this fracture type was created in more than half of the cases (57%)—more often than the pure posterior wall fracture—with axial loading of the femur.3
Letournel analyzed this mechanism and reported this fracture type in 4.6% of the resulting fractures.2 A further identified injury mechanism was force transmission along the greater trochanter, which was observed in 1.8%.2
The exact position of the hip joint at the time of impact is unknown. As many posterior column fractures remain incomplete, Letournel assumed that primarily a fracture of the posterior wall resulted, followed by a secondary posterior column component.2 Thus, the reported mechanism leading to isolated posterior wall fractures may be also responsible for this type of fracture. Correspondingly, the frequency of additional fracture modifiers, such as accompanying articular injuries, is suspected to be similar.
Clinical Relevance
The dashboard injury is appropriate to create associated fractures of the posterior column and posterior wall.
10.4 Hip Joint Stability
A considerable hip instability is suspected due to the combination of instabilities of both fracture components. Letournel reported a rate of accompanying hip dislocation up to 90%.2 Depending on the degree of involvement of the posterior column, especially posterior-cranial and central, fracture dislocations occur.
10.5 Biomechanics of Posterior Wall Fractures
There are no biomechanical data on associated fractures of the posterior column and posterior wall.
10.6 Treatment Indications
The amount of fracture instability determines the type of treatment in the majority of cases.
10.6.1 Conservative Treatment
Conservative treatment is only indicated in minimally displaced fractures without additional fracture pathologies, such as marginal impactions or intraarticular fragments.
Conservative treatment consists of physiotherapeutic treatment with muscle strength support, gait training, and coordination exercises. A partial weight bearing was allowed with one-fifth body weight for 6–12 weeks with subsequent increase. Full weight bearing was possible normally after 10–12 weeks.
10.6.2 Operative Treatment
Indications for operative treatment are:
Unstable hip joint
Incongruence of the hip joint
Intraarticular fragments
Increasing sciatic nerve lesions
Presence of an acetabular impaction area
If the joint or fracture is unstable, an emergency closed reduction under general anesthesia is immediately performed using standard reduction techniques (see ▶ 8).
10.7 Techniques of Osteosynthesis
10.7.1 Biomechanics of Osteosynthesis
Biomechanical data on stability of different stabilization techniques in associated posterior column and posterior wall fractures are not available.
10.7.2 Approach
Operative stabilization of associated posterior column and posterior wall fractures is performed using the Kocher-Langenbeck approach.
10.7.3 Reduction and Stabilization Techniques
The following reduction instruments are most frequently used:
Large pointed reduction forceps (Weller clamp)
Small pelvic reduction forceps for use with cortex screws (Farabeuf clamp)
Small pelvic reduction forceps for use with cortex screws (Jungbluth clamp)
Ball spike pusher
Universal chuck with T-handle for 5-mm Schanz screws
Spring plate4 (see ▶ Fig. 8.20 and ▶ Fig. 8.22)
If necessary, indirect reduction via plate
A stepwise reduction and stabilization concept is recommended for associated posterior column and posterior wall fractures:
Reduction of the posterior column
Lag screw fixation of the posterior column
Identification of (intra-)articular pathology
Reduction of marginal impactions
Reduction of posterior wall fragments
Lag screw fixation of posterior wall fragments
Reduction control
Labrum reconstruction
If necessary, additional spring plate fixation
Neutralization plate osteosynthesis posterior column/wall
Reduction of the Posterior Column
The first treatment step in these fractures is anatomical reduction of the posterior column fragment, which is guided at its proximal fracture line near the greater sciatic notch. Here, a fracture spike is usually present and, therefore, clear identification of both fracture sites is necessary to perform a reduction under direct visualization and digital palpation.
The close relationship of the gluteal neurovascular bundle must be considered to avoid iatrogenic injury.
Useful reduction tools are placement of a Schanz screw into the ischial tuberosity and then manipulation the posterior column fragment with an attached T-handle allowing de-rotation. Displacement can be corrected by internal rotation of the fragment (▶ Fig. 10.2).
Fig. 10.2 Manipulation of the posterior column fragment with the joystick technique using a Schanz screw inserted into the ischial tuberosity. Rotation and tilting allows for compensation of the internal rotation displacement of the fragment.
Alternatively, the small Farabeuf forceps can be used to allow fracture compression. Two bicortical 3.5 mm screws have to be inserted on each side of the fracture.
By fixing the forceps at the screw heads, compression and careful rotational movements can easily be performed to get anatomical reduction (▶ Fig. 10.3). The large Farabeuf forceps as well as the Jungbluth forceps are normally too bulky for addressing the spike area. Also, the Matta forceps can be used (see ▶ Fig. 10.8).
Fig. 10.3 Reduction of the posterior column fracture with the Farabeuf forceps.
The reduction maneuver can be supported by additional axial pressure perpendicular to the fracture plane using a ball spike pusher.
In distally displaced (short posterior column) fragments, reduction can be carried out by cranial pull of a plate that is only distally fixed in the direction of the greater sciatic notch (▶ Fig. 10.4).
Fig. 10.4 Reduction of the posterior column fracture using a distally fixed plate.
During reduction of the posterior column, the definitive plate position and localization of an additional lag screw insertion have to be considered.
Control of reduction is confirmed by digital palpation of the fracture line at the inner surface of the quadrilateral plate, palpating through the superior part of the greater sciatic notch or by displacing the posterior wall fragment dorsally under direct intraarticular view.
Only if no stepoffs or gaps are palpable or visible, anatomical reduction can be assumed (▶ Fig. 10.5).
Fig. 10.5 Digital reduction control palpating the fracture line on the quadrilateral surface.
Additionally, attention has to be paid on accompanying articular injuries. Distraction of the femoral head can be useful. This can be performed by placing an additional Schanz screw into the femoral neck and head.
Osteosynthesis of the Posterior Column
Definitive fixation of the posterior column fragment is performed by either lag screw fixation or posterior plate osteosynthesis (▶ Fig. 10.6, ▶ Fig. 10.7).
Frequently, first a temporary fixation of the posterior column is performed using K-wires or a short plate (▶ Fig. 10.8).
Fig. 10.6 Typical fixation of the posterior column and wall with lag screw fixation and application of a neutralization plate.
Fig. 10.7 An additional plate fixed close to the posterior border bridging the posterior column fracture leads to an increase in stability.
Fig. 10.8 Intraoperative views. (a) The image shows the already reduced high-posterior fracture of the posterior column, fixed with a Matta reduction forceps and a percutaneously inserted K-wire. (b) Temporary fixation was performed using a two-hole plate.
Identification of (Intra-)Articular Pathology/Reduction of Marginal Impactions
The next step consists of clear identification of concomitant intraarticular injuries. Intraarticular fragment have to be removed and, depending on their size, have to be additionally fixed.
It is crucial to identify marginal impactions. In rare cases, these fragments can be rotated up to 180 degrees and impacted into the cancellous bone of the posterior column and therefore can be difficult to find. Overlooked impaction fragments can result in articular stepoffs and gaps, thus increasing the risk of developing a secondary degenerative arthrosis.1,5
Reduction of Marginal Impactions
In the next step, reduction of identified marginal impactions is performed. Release of the cancellous bone is carefully performed using a raspatory or a chisel without damaging these fragments. These fragments are then reduced against the anatomically reduced femoral head, the latter acting as a template. The created cancellous bone defect can be filled up with autogenous cancellous bone from the greater trochanter6 or alternatively from the anterior/middle iliac crest (▶ Fig. 10.9).
Fig. 10.9 Technique of reduction of marginal impactions zone and bone support using cancellous chips.
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