Fracture Characteristics

Transverse/posterior wall fractures represent—other than both-column fractures—the second most common acetabular fracture type. It can be expected in approximately 18% of cases.^1,​2

Comparable to pure transverse fractures, the main fracture plane can be extremely variable with a wide variety orientations and angulations. In general, infratectal, juxtatectal, and transtectal fracture lines can be distinguished:

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  Infratectal fractures: the main fracture line is orientated through the anterior and posterior wall, across the acetabular fossa

  
  
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  Juxtatectal fractures: the main fracture line is orientated through the anterior and posterior wall, at the transition of the acetabular fossa to the cranial/superior joint surface

  
  
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  Transtectal fractures: the main fracture line is orientated through superior acetabulum, leaving only a small articular fragment connected to the intact iliac bone

From inside the pelvis, only the infratectal fracture line shows a classical transverse orientation, whereas all other fracture subtypes show a more oblique fracture. The more superior the fracture, the larger the inclination angle relative to the horizontal plane. The ischiopubic segment typically shows a medial (internal) rotation around a hypothetical axis running through the pubic symphysis. Additionally, a rotation of this fragment around an axis running through the upper pubic ramus is observed, resulting in lateral rotation of the ischial tuberosity. This rotational deformity leads to a posterior dislocation of the ischiopubic segment. The intact iliac bone is normally in its anatomical position and therefore undisplaced. Rarely, superior external rotation of the iliac bone due to widening of the anterior sacroiliac (SI) joint or even complete SI joint dislocation can be observed.

The additional wall fragment often is an isolated large fragment, but can be multifragmentary or even with an additional marginal impaction. Comparable to pure posterior wall fractures, the fragment(s) can be located either posterior, posterosuperior, and posteroinferior.

In nearly half of the cases an additional posterior or posterior-cranial hip dislocation is present, and in approximately 20% a central dislocation is observed. Posterior fracture dislocations are often associated with trans- or juxtatectal transverse fracture components, whereas central fracture dislocations show more infra- or juxtatectal transverse fracture components.³

Letournel also described an atypical fracture type with a transverse fracture and a large posterosuperior posterior wall fragment extending cranially to the iliac crest.

15.2 Radiological–Anatomical Criteria

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  Pelvic anteroposterior (AP) view (▶ Fig. 15.1). The lines representing the columns (iliopectineal line, ilioischial line, line of the anterior and posterior walls) are disrupted. A fracture of the obturator foramen is normally not present. Additional “isolated” inferior pubic ramus fractures are rarely seen, without a perpendicular course, as in T-type fractures. The teardrop figure is medially displaced, following the displacement of the ischiopubic segment. The acetabular roof can be involved in transtectal fracture types. An additional posterior wall fragment can be seen directly lateral to the acetabulum or as a bony shadow superimposing the acetabulum. Often, a posterosuperior or a central dislocation of the femoral head is observed. Accompanying injuries of the pubic symphysis or the ipsilateral SI joint can be confirmed or excluded.

  
  
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  Iliac oblique view (IOV) (▶ Fig. 15.2). The extent of the fracture line at the posterior column becomes clear.

  
  
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  Obturator oblique view (OOV) (▶ Fig. 15.2). The orientation of the anterior fracture line becomes clearer, and the height of the fracture course in the anterior column is observed. An injury at the bony border to the obturator foramen can be analyzed and additional pubic rami fracture lines can be diagnosed as being independent from the transverse fracture. The fracture of the posterior wall is best seen using this view, as it is most often observed lateral to the acetabulum or on top of the femoral head.

  
  
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  Computed tomography (▶ Fig. 15.3). On two-dimensional axial images, the transverse fracture is vertically orientated (sagittal fracture line) in an AP direction. Accompanying injuries of the SI joint or the pubic symphysis can be confirmed or excluded. The extent of the posterior wall fracture, the presence of intraarticular fragments, and marginal impactions can be analyzed. Three-dimensional (3D) images allow an optimal view of the fracture pattern, the fracture orientation, and the division into infratectal, juxtatectal, and transtectal fractures.

  
  
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  Transition forms to other fracture types. In large posterior wall fragments extending to the ischial tuberosity, transitions to T-type fractures can be present. In vertically orientated transverse fracture with extension into the iliac fossa, transitions to both-column fractures are possible.

  
  
  
  

  

  
  

  Fig. 15.1 Transverse plus posterior wall fracture. The dotted lines and arrows show the disruption of the column lines, according to the transverse fracture component, and the additional fragment of the posterior wall, respectively.

  
  
  
  

  

  
  

  Fig. 15.2 IOV and OOV from ▶ Fig. 15.1. The dotted line represents the disruption of the posterior column; the OOV shows the disruption of the anterior column near the superior acetabulum. The typically displaced posterior wall fragment is seen lateral to the joint (arrows).

  
  
  
  

  

  
  

  Fig. 15.3 CT analysis from ▶ Fig. 15.1. Two- and three-dimensional CTs clearly show the extent of the fracture and the location of posterior wall fragments, including an intraarticular fragment. The lines represent the typical fracture pattern on the axial CT.

15.3 Pathobiomechanics

Letournel described various mechanisms resulting in transverse/posterior wall fractures.³ Fractures can occur by forces acting along the greater trochanter and the femoral neck to the acetabulum, although this mechanism is inappropriate to explain the presence of the additional posterior wall fragment. Additionally, the classical dashboard mechanism with hip flexion and force transmission from anterior was postulated. Clinically, this mechanism resulted in transverse/posterior wall fractures in 16%, but predominantly to pure posterior wall fractures and in a total of 22.2% of fractures with a transverse fracture component (pure transverse fracture, T-type fracture, associated transverse plus posterior wall fracture).

Another possible mechanism is the impact on the foot while the knee is extended and the hip joint slightly flexed.

Dakin et al observed transverse/posterior wall fractures after analysis of the accident mechanism as the most frequent fracture type and postulated a dashboard mechanism with axial loading of the femur in a nonneutral abduction position. This fracture type was observed in 30% after frontal collisions and in 47% after slight frontal-oblique collisions.⁴

Rupp et al experimentally confirmed the dashboard mechanism as being capable of producing a transverse/posterior wall fracture.⁵

15.4 Hip Joint Stability

Studies analyzing hip joint stability in associated transverse and posterior wall fractures do not exist. However, there are some studies analyzing pure transverse fractures and isolated fractures of the posterior wall. Thus, these results can be partially transferred to this fracture type. These results are described in detail in ▶ 8 and ▶ 14.

In summary, fractures of the posterior wall of less than 25% and more than 50% articular involvement have to be considered stable or unstable, respectively. An instability is usually associated with an additional femoral head dislocation.^{6,​7,​8,​9} The transverse component of the fracture can be considered as stable, when the roof–arc angle is > 60 degrees.^10,​11

15.5 Biomechanics of Transverse/Posterior Wall Fractures

No biomechanical data are presently available on transverse/posterior wall fractures. However, the influence of an incongruent reduction after pure transverse fracture and the consequences of the reduction of isolated posterior wall fragments were analyzed.

Residual step-offs after reduction of transverse fractures leads to stress concentrations at the acetabular roof, whereas gaps have been found to be prognostically more favorable.^12,​13

Small defects at the posterior wall lead to an at least 1.3-fold increase of superior contact forces,^14,​15 which can lead to a relatively high rate of posttraumatic arthrosis, which is supported by clinical evaluations.^2,​3,​16

15.6 Treatment Indications

The type of treatment depends on fracture morphology, fracture displacement, articular congruence, overall joint stability, and additional articular modifiers.

15.6.1 Conservative Treatment

Conservative treatment is only recommended in undisplaced or minimally displaced fractures without additional articular injuries.

Very low infratectal transverse fractures with a roof–arc angle > 45 degrees and a stable joint with congruency in the weight-bearing area can be sufficiently treated nonoperatively only when the posterior wall fragment is undisplaced and stable during dynamic fluoroscopic investigation.

15.6.2 Operative Treatment

Operative treatment is indicated in:

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  Unstable hip joint

  
  
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  Femoral subluxation (joint incongruency)

  
  
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  Roof–arc measurement < 45 degrees

  
  
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  Posterior wall fragment size > 25%

  
  
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  Displacement > 2 mm in the weight-bearing area

  
  
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  Intraarticular fragments

  
  
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  Increasing sciatic nerve injury

  
  
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  Presence of marginal impaction

If the joint or fracture is unstable, an emergency closed reduction under general anesthesia is immediately performed using standard reduction techniques (see ▶ 8).

In femoral head dislocation, emergency treatment consists of closed reduction by supracondylar traction with one-seventh to one-tenth of body weight. Often, medial displacement cannot fully be corrected. To prevent cartilage shearing injury, gentle reduction maneuvers should be performed.

In persistent dislocations and especially in fractures with increasing sciatic nerve injury, a relative emergency indication for open reduction and osteosynthesis is given.

In undisplaced or minimally displaced, but potentially unstable, high transverse fractures (transtectal) with a low roof–arc angle, a prophylactic percutaneous screw osteosynthesis has to be considered to avoid further displacement until definitive surgery.

In unstable central or posterior fracture dislocations, supracondylar traction is always recommended.

15.7 Techniques of Osteosynthesis

15.7.1 Biomechanics of Osteosynthesis

There are no biomechanical studies of the osteosynthesis of transverse/posterior wall fractures available.

Again, only the results of studies of the fracture components can be transferred to this special fracture entity (see ▶ 8 and ▶ 14).

Ultimately, a dorsoventral stabilization of the transverse component is recommended^{17,​18,​19,​20} and a safe standard fixation technique of the posterior wall fragment(s) by screw and/or plate osteosynthesis.^{21,​22,​23}

However, anatomical reconstruction of the posterior wall fracture is not able to reproduce a physiological load distribution within the acetabulum. Peak pressure is increased at the superior acetabulum and decreased at the anterior and posterior lunate surface.¹⁴

15.7.2 Approach

The classical approach for transverse/posterior wall fractures is the Kocher-Langenbeck approach. Isolated anterior approaches are not useful as the large and unstable posterior wall fracture cannot be addressed. Letournel additionally recommended the extended iliofemoral approach in fractures with a transtectal transverse fracture component or for delayed reconstructions (after 3 weeks). Due to the relevant approach-related morbidity, the latter approach is avoided.³

Because the main fracture displacement in most transverse fracture components is an internal rotation of the ischiopubic fragment around a vertical axis through the symphysis (see fractural characteristics) resulting in major posterior displacement, surgery from posterior is advantageous. According to the literature, in the majority of fractures with this fracture type, the Kocher-Langenbeck approach is performed.^{2,​16,​24,​25,​26}

Using the Kocher-Langenbeck approach, however, direct visualization of the anterior transverse component is not possible. Thus, control of reduction has to be performed either by fluoroscopy or by palpation.

Palpation of the quadrilateral surface can be digitally performed through the greater sciatic notch, reaching the anterior fracture with the tip of the finger.

Extension of the Kocher-Langenbeck approach by surgical hip dislocation with a trochanter flip osteotomy provides a good alternative to an extended iliofemoral approach, with the possibility of direct visual control reduction and complete inspection of the articular surface.²⁷

This allows addressing intraarticular pathologies and a safe periarticular screw placement under direct visualization. This approach is therefore recommended in transtectal fractures, free intraarticular fragments, and in the presence of marginal impactions.^{28,​29,​30,​31} In rare cases, a combined AP procedure can be an option.

15.7.3 Reduction and Stabilization Concept

Various instruments are available for reduction. The following are most frequently used (▶ Fig. 15.4):

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  Long-pointed reduction forceps (Weller clamp)

  
  
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  Ball spike pusher

  
  
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  Farabeuf clamps

  
  
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  Reduction forceps according to Jungbluth

  
  
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  Different Matta clamps

  
  
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  Asymmetrical reduction forceps

  
  
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  Colinear clamp

  
  
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  5-mm Schanz screw with T-handle

In addition, laminar spreaders and various raspatories or periosteal elevators are used.

Reduction and fixation of a transverse/posterior wall fracture follows a sequential step-by-step reduction and fixation protocol:

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   Mobilization of the fracture

   
   
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   Joint inspection

   
   
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   Reduction of the transverse fracture component

   
   
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   Stabilization of the transverse fracture component

   
   
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   Reduction of fracture of posterior wall

   
   
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   Stabilization of the posterior wall fracture

   
   
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   Definitive osteosynthesis of the transverse fracture

First Step: Mobilization of the Fracture

First, the posterior wall fragment is mobilized. This fragment is usually attached to the posterior joint capsule. It has to be mobilized and positioned posteriorly. By inserting laminar spreaders, raspatories, or by fracture distraction using the Farabeuf forceps, the transverse fracture is mobilized from posterior. Alternatively, mobilization of the ischiopubic segment with an inserted Schanz screw into the ischial tuberosity using the joystick technique allows adequate fracture gap opening (▶ Fig. 15.5). Fracture cleaning with removal of hematoma formation and fracture debris is performed.

Second Step: Posterior Joint Inspection

After posterior mobilization of the posterior wall fragment(s), by additional fracture gap distraction, the joint can easily be inspected from posterior. Free articular fragments and marginal impaction zones have to be addressed. Articular fragments have to be removed or, if possible should be stabilized, depending on their size. Marginal impactions have to be elevated and possibly supported with autologous bone grafts.

In all fractures with a transverse component, labral lesions have to be expected at the fracture level. Accordingly, the labrum should be evaluated regarding injury or avulsions.

If a marginal impaction was preoperatively detected, approaching the surgical hip dislocation according to Ganz should be considered to address the intraarticular pathology. Cleaning of the fracture surfaces is then performed.

Third Step: Reduction of Transverse Fracture Component

Reduction of the transverse fracture from posterior to visualize the anterior fracture part can only be achieved through exposure using the Kocher-Langenbeck approach or by additional surgical hip dislocation according to Ganz.

Different reduction techniques are proposed. While manipulating, the gluteal neurovascular bundle has to be protected, especially in transtectal fractures.

After fracture debridement, often a Schanz screw is inserted into the ischial tuberosity to reduce the rotational displacement. The course of the sciatic nerve has to be considered while manipulating. Additionally, the Farabeuf forceps (▶ Fig. 15.6) or the Jungbluth forceps can control reduction, depending on the size of the intraoperative field.

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Epidemiology Classification of Acetabulum Fractures Indications and Planning Pure Transverse Fractures Approaches Radiological Diagnostics

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