Fracture Characteristics

Anterior wall fractures are rare acetabular fractures with a suspected incidence of approximately 3.5%.¹

The fracture of the anterior wall usually has a trapezoidal shape and starts typically proximal below the level of the anterior inferior iliac spine. The location of the distal fracture line is variable at the superior pubic ramus and can be incomplete. The anterior horn is fractured in many cases. Medial extension can lead to involvement of the quadrilateral surface or the acetabular roof. In the former fracture type, an articular component of the posterior acetabulum can be attached to the fragment.

11.2 Radiological–Anatomical Criteria

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  Pelvic anteroposterior (AP) view (▶ Fig. 11.1). Characteristically, the iliopectineal line is disrupted at two points. Cranially, a characteristic spur of the trapezoidal-shaped fragment is often visible, whereas the distal disruption is usually seen at a variable point at the upper pubic rami. Disruption of the anterior wall line is typically located in its upper third. In extended fractures with involvement of the quadrilateral surface, the teardrop figure can be displaced or appears rotated or, in rare cases, the ilioischial line can be disrupted when fracture lines extend into the posterior articular area. Overall, the lines of the posterior acetabulum (ilioischial line, posterior wall line) usually remain intact. The femoral head is dislocated or subluxated either anteriorly or medially.

  
  
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  Iliac oblique view (IOV) (▶ Fig. 11.2). The posterior column, including the greater sciatic notch, and the iliac fossa and iliac crest are uninjured. On this view, extended fractures with involvement of the quadrilateral surface and the most cranial fracture line are visible. In severe medial displacement of the anterior wall, these fractures can appear like a posterior column fracture. Only accurate analysis of the posterior column line can avoid misinterpretation (▶ Fig. 11.3).

  
  
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  Obturator oblique view (OOV) (▶ Fig. 11.4). On the OOV, the typical trapezoid shape of the fragment with medialization of the femoral head is best seen. The structures of the posterior column and the posterior wall are found intact.

  
  
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  Computed tomography. In addition to the exact anatomy of the fracture fragment, the fragment size, further fracture lines, and possible additional injuries (e.g., extent of involvement the quadrilateral surface, intraarticular fragments, or marginal impactions) are optimally visualized. The three-dimensional (3D)-CT shows the spatial anatomy of this fracture.

  
  
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  Transition forms to other fracture types. When multiple fracture lines are present in the pubic rami, transitions to inferior anterior column fractures are possible (62-A 3.3).

  
  
  
  

  

  
  

  Fig. 11.1 Fracture of the anterior wall. The typical trapezoidal shape of the fragment as well as the typical central hip dislocation are already apparent on the anteroposterior pelvic view. The nondisrupted ilioischial line confirms the intact posterior column. The extent of the main fragment is marked with arrows.

  
  
  
  

  

  
  

  Fig. 11.2 The marked line of the posterior column on the iliac oblique view confirms its integrity. The gap at the quadrilateral surface, representing fracture fragments, is marked with arrows. In the proximal part, the line of the posterior column is superimposed by the anterior wall fragment (see ▶ Fig. 11.3).

  
  
  
  

  

  
  

  Fig. 11.3 Fracture of the anterior wall. On the anteroposterior pelvic view, disruption of the iliopectineal line at two points is clearly visible. The fracture extends far into the quadrilateral surface reaching the posterior column. On the iliac oblique view, the overall medial displacement is recognized. The line of the posterior column is superimposed and seems interrupted. However, detailed analysis shows the integrity of this line. The obturator oblique view confirms the extent of the fracture with a long split through the quadrilateral surface, which tangents the posterior column.

  
  
  
  

  

  
  

  Fig. 11.4 The obturator oblique view clearly identifies the typical trapezoidal shape of the fragment and the extensive defect in the area of ​​the anterior column. The femoral head is anatomically reduced with normal alignment to the acetabular roof. The intact posterior column is shown with dotted lines.

11.3 Pathobiomechanics

Letournel proposed an injury mechanism with force transmission along the greater trochanter and the femoral neck in neutral position for abduction/adduction while the hip is 50 degrees externally rotated. This mechanism resulted in 5.1% rate of anterior wall fracture occurrence.² As this excessive external rotation position is clinically unusual, anterior wall fractures are rarely expected, whereas anterior column fractures are more common, as these are the result from more slight external rotations.

In the presence of anterior wall fractures, involvement of the quadrilateral surface is frequent, suggesting that a more central force transmission with < 50 degrees of external rotation was causal.

Dakin et al reported one single anterior wall fracture after force transmission along the greater trochanter in an anterolateral collision,³ whereas Lansinger et al only observed pure transverse fractures and fractures of the anterior column after this injury mechanism.⁴

11.4 Hip Joint Stability

In most cases, the fragment is centrally displaced with an additional medial hip dislocation. Due to the additional quadrilateral surface fracture(s), a significant instability is present. Thus, open reduction and internal fixation is often recommended.

11.5 Biomechanics of Anterior Wall Fractures

There is only one biomechanical analysis dealing with anterior wall fractures.⁵ Konrath et al simulated anterior wall fractures regarding change of hip joint mechanics using a standardized fracture model.^5,​6,​7

Compared to the intact acetabulum, an anterior wall fracture resulted in a significant reduction of the contact anterior and posterior area and to an increased anterior and posterior pressure distribution, whereas the superior contact areas showed no difference.

11.6 Treatment Indications

The type of treatment depends on the fracture displacement with the corresponding hip instability and the presence of additional articular injuries.

11.7 Conservative Treatment

Conservative treatment is only indicated in almost undisplaced fractures or if no additional fracture modifiers are present, such as marginal impactions or intraarticular fragments.

11.7.1 Operative Treatment

Indications for surgical treatment are:

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  Unstable hip joint

  
  
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  Femoral subluxation/dislocation

  
  
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  Intraarticular fragments

  
  
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  Presence of marginal impaction

In the presence of a severely unstable fracture/hip joint, emergency closed reduction with lateral and supracondylar axial traction is performed with one-seventh to one-tenth body weight. Medial displacement cannot always be corrected.

In order to avoid shearing injuries of the acetabular and femoral head cartilage to the fragment, gentle reduction maneuvers under general anesthesia are mandatory.

If reduction is impossible, a relative emergency indication exists for open reduction and primary osteosynthesis of the fracture.

11.8 Techniques of Osteosynthesis

11.8.1 Biomechanics of Osteosynthesis

Konrath et al analyzed the effect of anatomical reconstruction with osteosynthesis regarding changes of contact surface and resulting intraarticular joint pressures.⁵

In seven cadavers, typical anterior wall fractures were osteotomized and stabilization was performed using a 3.5 mm anterior column screw in combination with an inguinal 3.5 mm reconstruction plate.

Despite anatomical reduction, a significant reduction of the anterior and posterior contact area as well as a reduction of the posterior pressure distribution were observed. At ​​the superior acetabulum, no significant changes occurred.

11.8.2 Approach

For operative stabilization of anterior wall fractures, the intrapelvic or ilioinguinal approach is recommended.^{1,​2,​8,​9,​10,​11}

Alternatively, in severe comminuted fractures, a modification of the ilioinguinal approach according to Ganz is recommended to address the anterior rim of the acetabulum under direct visualization.¹² In fractures extending superiorly, the Smith-Petersen approach or the iliofemoral approach can be useful.

Lenarz and Moed described a modified Smith-Peterson approach for atypical anterior wall fractures.¹³ Here, an iliofemoral enlargement of this approach with detachment of the iliacus muscle from inside the iliac fossa is performed. The gluteus medius muscle is not dissected and the tensor fasciae latae muscle is released only in its anterior part. The caput reflexum of the rectus femoris muscle is only detached if the anterior inferior iliac spine is part of the anterior wall fragment, not to devascularize this fragment.¹³

11.8.3 Reduction Techniques

Various instruments are available for reduction. The following reduction instruments are most frequently used (▶ Fig. 11.5):

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  Ball spike pusher

  
  
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  5 mm Schanz screw with T-handle

  
  
  
  

  

  
  

  Fig. 11.5 Common reduction aids for fracture treatment in anterior wall fractures (from left to right: T-handle, Schanz screw, different ball spike pushers).

A stepwise reduction maneuver is recommended for anterior wall fractures:

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  Reduction hip joint

  
  
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  Identification of articular fragments or marginal impactions

  
  
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  Reduction main fragment

Reduction of the Hip Joint

Normally, longitudinal traction alone allows reduction of the femoral head out of its central dislocated position. Lateral traction by percutaneous insertion of a Schanz screw into the femoral neck can support the reduction maneuver (▶ Fig. 11.6).

Identification of the Intraarticular Pathology

It is mandatory to identify intraarticular fragment and marginal impaction zones, either in the wall fragment itself or in the anterosuperior acetabulum, before definitive reduction of the main fragment is performed. Impactions are often present in elderly people with relevant osteoporosis.

Medialization and reduction of the anterior wall fragment is often difficult using the ilioinguinal approach because manipulation increases the risk of iatrogenic injury to the femoral vessels. If reduction is possible, a bone window can be created to indirectly reduce an impaction zone against the reduced femoral head, which acts as a template.

Intraarticular fragments are correspondingly difficult to address with the ilioinguinal approach.¹⁴ The extended ilioinguinal approach according to Ganz has to be considered,¹² as this allows an articular view.

The intrapelvic approach has revolutionized reduction of these anterior and superior impaction zones. This approach always has to be considered in specific articular pathology to get a better overview.¹⁰

By medialization of the main wall fragment and twisting of quadrilateral surface fragments, using the intrapelvic approach, a direct view to the joint and to the cancellous fracture site is possible and reduction can be controlled under direct visualization.^{15,​16,​17}

A precondition for reduction of these impactions is the anatomical reduction of the femoral head into its anatomical position. Femoral head reduction is performed by lateral pull. A Schanz screw percutaneously inserted into the femoral neck supports this maneuver. As a consequence, this leads to reduced tension on the obturator neurovascular bundle and results in some reduction of medially displaced fracture components of the quadrilateral surface by ligamentotaxis and better visualization of superior marginal impactions (gull sign according to Anglen).¹⁸ The typical malposition of anterior wall fractures is a cranial and medially displaced main fragment.⁹ The extent of the articular (chondral) involvement is variable.

Mobilization of the impacted fragment is then performed against the femoral head, the latter acting as a template.^16,​17 Visualization of marginal impactions can also be optimized by additional osteotomy of anterior parts of the anterior column.¹⁶

Reduction of impactions is performed by using a periosteal elevator, osteotomes, or comparable instruments (▶ Fig. 11.7). The resulting cancellous bony defect can be filled with cancellous bone chips obtained from the iliac crest or the greater trochanter. Also, bone substitutes can be used.¹⁹ Temporary fixation of these reduced fragments is performed with K-wires or screws.^9,​16

Related posts:

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

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