Fracture Characteristics

Pure transverse fractures are the second most common elementary acetabular fracture type with a typically singular fracture line. This fracture type is expected in approximately 10% of cases.¹

The fracture plane can be extremely variable and runs through the acetabular joint at different inclination angles. In general, infratectal, juxtatectal, and transtectal fractures are distinguished (▶ Fig. 14.1):

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

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

  
  
  
  

  

  
  

  Fig. 14.1 Different subtypes of pure transverse fractures depending on the most proximal fracture course.

From inside the pelvis, only the infratectal fracture line shows a classical transverse orientation. 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 is typically medial (internal) rotated 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 femoral head often remains directly below the superior fragment or follows the ischiopubic segment, imposing as a central dislocation.

14.2 Radiological–Anatomical Criteria

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  Pelvic anteroposterior (AP) view (▶ Fig. 14.2). The lines representing the columns (iliopectineal line, ilioischial line, line of the anterior and posterior wall) 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. Often, 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. 14.2). The localization of the fracture line at the posterior column becomes clear.

  
  
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  Obturator oblique view (OOV) (▶ Fig. 14.2). As the orientation of the anterior fracture line becomes clearer, 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.

  
  
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  Computed tomography (▶ Fig. 14.3). On two-dimensional (2D) 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 conformed or excluded. 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. Transtectal transverse fractures can be combined with an additional fracture at the pubic rami. These belong to transverse fractures, when the inferior part of the acetabulum is intact and no separation between the anterior and posterior columns is present (transition to T-type fractures).

  
  
  
  

  

  
  

  Fig. 14.2 (a) Left infratectal transverse fracture. The typical disruption of both column lines (iliopectineal and ilioischial line) is seen. OOV (right) shows the inferior course of the transverse fracture. Signs of wall involvement are not found. (b) Right undisplaced infratectal transverse fracture.

  
  
  
  

  

  
  

  (c) Slightly displaced juxtatectal transverse fracture. (d) Severely displaced juxta- to transtectal transverse fracture.

  
  
  
  

  

  
  

  Fig. 14.3 Pure transverse fracture. Three-dimensional CT with subtraction of the femoral head shows the typical fracture course.

14.3 Pathobiomechanics

Letournel described various mechanisms resulting in pure transverse fractures.² Fractures can occur by forces acting along the greater trochanter and the femoral neck to the acetabulum or even a dashboard mechanism was postulated.

The lateral compression mechanism can result in this fracture type, when the hip joint is slightly internally rotated of about 20 to 40 degrees. The position of the hip joint regarding abduction or adduction influences the height of the transverse component. With more adduction, more transtectal fractures are expected and in abducted hip positions, infratectal fractures are expected. Clinically, this mechanism resulted in pure transverse fractures in 4% of cases and in a total of 16.7% of fractures with a transverse fracture component (pure transverse fracture, T-type fracture, associated transverse plus posterior wall fracture).

Additionally, the dashboard mechanism can be appropriate to produce a transverse fracture. An abduction of 50 degrees with force transmission along the femoral shaft axis is suggested.

Furthermore, theoretically, an axial force in hip extension (fall from a height) and slight abduction can result in a transtectal transverse fracture. Clinically, this mechanism led to a pure transverse fracture in 3.7% of cases, and to fractures with a transverse fracture component in 22.2% (pure transverse fracture, T-type fracture, associated transverse plus posterior wall fracture).

Lansinger et al confirmed experimentally the lateral compression mechanism.³ Additionally, axial loading in hip extension with various degrees of rotation (20 degrees internal rotation, 30 degrees external rotation) resulted in this fracture type. Overall, forces of 500 N were necessary. In 20 hip joints, this fracture type was found in 55%.

Dakin et al observed pure transverse fractures after analysis of the accident mechanism in 26% after lateral compression injury. The exact force vector, however, remained unclear. Transverse fractures were observed after direct frontal collision, anterolateral force transmission, after side collision, and even after complex mechanisms with ejection out of the vehicle.⁴

Rupp et al experimentally confirmed the dashboard mechanism as being capable of producing a transverse fracture.⁵ However, in this analysis, transverse fractures occurred only in combination with a posterior wall fracture.

14.4 Hip Joint Stability

Some studies analyzed hip stability in the presence of a pure transverse fracture.

Vrahas et al analyzed the effect of different transverse acetabular fractures on hip joint stability.⁶ They distinguished transverse fractures on the basis of different roof–arc angles according to Matta⁷ at 40, 50, and 60 degrees, respectively. Forces of 800 N in 25 degrees hip flexion and 20 degrees abduction resulted in 91%, 50%, and 17% in displacement, in transtectal, juxtatectal, and infratectal fractures, respectively. With increasing forces (1600 N), additionally in infratectal fractures (roof–arc angle 60 degrees), displacement occurred in 58%.

A roof–arc angle of 30 to 40 degrees was associated with an unstable fracture, whereas a transition zone to stable fractures was observed at angles of 40 to 60 degrees.

Thomas et al also analyzed hip stability in simulated transverse fractures with a roof–arc angle of 90, 60, 30, and 0 degrees.⁸ Below a roof–arc angle of 60 degrees, fractures were considered stable. Instability occurred between angles of 30 degrees and 60 degrees. Abduction more often resulted in instability than adduction.

14.5 Biomechanics of Pure Transverse Fractures

The influence of incongruent reduction was analyzed by Malkani et al and Hak et al.^9,​10

Malkani et al found that remaining steps of up to 1 mm in transverse fractures were tolerable, whereas remaining steps of ≥ 2 mm lead to a significant increase in acetabular peak pressures.¹⁰ Although no significant increases in peak pressures were observed after anatomical reduction, a malalignment of 1 mm led to a peak pressure increase of 20% and a malalignment of >2 mm resulted in an increase of 50%.

Hak et al stated that the fracture height and the amount of displacement were associated with higher stress concentrations.⁹

A persistent step in transtectal transverse fractures resulted in a twofold increase of stress concentrations in the superior area, whereas remaining steps or gaps in juxtatectal fractures and gaps in transtectal fractures had no influence on peak stresses.

14.6 Treatment Indications

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

14.6.1 Conservative Treatment

Conservative treatment is only recommended in undisplaced or minimally displaced transverse 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 sufficiently be treated nonoperatively.

14.6.2 Operative Treatment

Operative treatment is indicated in:

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  Unstable hip joint

  
  
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  Femoral subluxation (incongruency)

  
  
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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

In undisplaced or minimally displaced, but potentially unstable, high transverse fractures (transtectal) with a low roof–arc angle, prophylactic percutaneous screw osteosynthesis can be a treatment option.

In high transverse fractures with central hip dislocation, temporary traction to avoid additional articular damage should be considered.

14.7 Techniques of Osteosynthesis

14.7.1 Biomechanics of Osteosynthesis

Several authors analyzed the stability of various stabilization concepts for the fracture stabilization of pure transverse fractures.^{11,​12,​13}

Sawagushi et al analyzed the type of displacement after anterior and posterior stabilization.¹² A posterior plate osteosynthesis was combined with different anterior stabilization concepts. Posteriorly, smallest displacement was observed when two posterior plates were combined with an anterior column screw. The same combination resulted in low shear forces acting at the quadrilateral surface. At the anterior column, all stabilization techniques resulted in comparable displacements.

However, the maximum displacement was below 0.1 mm for the majority of osteosyntheses.¹² Thus, all osteosyntheses with a combined AP stabilization of a pure transverse fracture lead to a sufficient stability.

Shazar et al analyzed different stabilization techniques in juxtatectal transverse fractures using a synthetic bone model.¹³ First, single anterior reconstruction plate osteosynthesis was used with four different screw configurations. In the second experimental setup, six different osteosyntheses were analyzed: isolated anterior plate osteosynthesis, isolated posterior plate osteosynthesis, anterior plating with a posterior column screw, posterior plating with an anterior column screw, combined anterior plus posterior plate osteosynthesis, and posterior double plate osteosynthesis. A single leg stance situation was simulated.

The highest levels of stiffness were found for screw configurations, where a screw was placed as near and as far away from the fracture on both sides, corresponding to a standardized fixation design.

Regarding various stabilization techniques, the highest level of stiffness was observed after posterior plate and anterior column screw osteosynthesis at the anterior fracture gap and after AP plate osteosynthesis at the anterior and posterior fracture gap, respectively.

Chang et al compared isolated anterior and posterior lag screw osteosyntheses, pure posterior plate osteosynthesis, and dynamic posterior cerclage wiring combined with an additional anterior column screw in transtectal transverse fractures.¹¹ The highest level of stiffness was observed using posterior plate osteosynthesis. However, anterior gaps were observed due to insufficient plate contouring (see ▶ Fig. 14.13).

A recent biomechanical analysis using supra- and infrapectineal plates on plastic models of a transverse fracture with a medial-superior orientated load transmission showed comparable results to conventional osteosyntheses, or even better results under certain conditions.¹⁴

Higher stiffness was observed with these new plates in comparison to posterior plating with anterior column screw fixation, whereas no difference was seen when compared to bilateral lag screw fixation. The infrapectineal plate showed the highest stress limits.

A recent finite element analysis of five different reconstruction concepts found insignificant fracture zone movement for all simulated stabilization methods. The persisting movements all were below 0.1 mm.¹⁵

14.7.2 Approach

The decision of which approach to choose in treating pure transverse fractures depends on several factors: localization of the main displacement (anterior or posterior), the height of the transverse fracture, and presence and localization of additional intraarticular injuries (e.g., intraarticular fragments, marginal impactions).²

Indications for the use of the Kocher-Langenbeck approach:

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  Undisplaced fractures¹⁶

  
  
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  Infratectal fractures with predominantly posterior displacement^2,​16

  
  
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  Juxtatectal fractures with predominantly posterior displacement^2,​16

A main posterior displacement is present in most transverse fractures, due to internal rotation of the ischiopubic segment around a vertical axis through the pubic symphysis (see fracture characteristics); therefore, most reported cases in the literature were treated using a posterior (Kocher-Langenbeck) approach.^{17,​18,​19,​20} However, no direct visualization of the anterior fracture component is possible and, therefore, control of reduction is only possible by digital palpation or fluoroscopy. Digitally, this can be performed at the medial side (quadrilateral surface) by palpating through the greater sciatic notch.

Enlargement of the Kocher-Langenbeck approach using the trochanter flip osteotomy with surgical hip dislocation allows direct visual control of the anterior reduction,²¹ addressing intraarticular pathologies and safe periarticular screw placement. This extension is recommended especially in transtectal fractures, free articular fragments, and marginal impactions.^{22,​23,​24,​25}

When the main displacement is found anteriorly, an anterior approach is recommended. The ilioinguinal approach^2,​16 or the intrapelvic approach^{26,​27,​28} are suggested.

Indications for the use of the ilioinguinal approach:

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  Infratectal fractures with predominantly anterior displacement²

  
  
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  Juxtatectal fractures with predominantly anterior displacement²

For transtectal fractures, the extended iliofemoral approach was recommended by Letournel.² Alternatively, the Kocher-Langenbeck approach in conjunction with the surgical hip dislocation is an option.^{23,​24,​25}

Indications for use of intrapelvic approach are comparable to the ilioinguinal approach. However, the intrapelvic approach is frequently used even in transtectal fractures.

In rare cases, if a direct anterior and posterior visual control is necessary, a combined anteroposterior approach can be chosen,^{18,​19,​20} but is associated with longer operating time and a higher blood loss (see ▶ 7).

14.7.3 Reduction and Stabilization Concept

Posterior Approach (Kocher-Langenbeck)

A step-by-step reduction and fixation protocol is recommended.

Various instruments are available for reduction. The following are most frequently used^21,​29 (▶ Fig. 14.4):

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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.

First Step: Mobilization of the Fracture

By inserting laminar spreaders, raspatories, or by fracture distraction using the Farabeuf forceps, the fracture is opened and 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. 14.5). Fracture cleaning with removal of hematoma formation and fracture debris is performed.

Second Step: Posterior Joint Inspection

Posterior joint inspection is limited. Here, preoperative radiological evaluation to detect additional injuries is essential. However, in 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, approach extension to surgical hip dislocation according to Ganz should be considered to address the intraarticular pathology. Cleaning of the fracture surfaces is then performed.

Third Step: Fracture Reduction

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

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

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, Farabeuf forceps (▶ Fig. 14.6) or Jungbluth forceps can control reduction, depending on the size of the intraoperative field.

Related posts:

Epidemiology Classification of Acetabulum Fractures Indications and Planning T-Type Fractures Approaches Radiological Diagnostics

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