1.1 Instability/subluxation

In 1948, Urist noted that the integrity of the acetabular cartilage along the posterior rim of the acetabulum is a critical factor for a good outcome [5]. In matched cases of posterior fracture dislocations of the hip treated nonoperatively and by open reduction, good function and little or no disability were shown when the joint surfaces were in anatomical alignment and the joint congruence was maintained.

1.2 Articular incongruity

In 1961, Rowe and Lowell [4] reported on a retrospective series of acetabular fractures and identified the following negative predictors for clinical outcomes:

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  Disruption of the superior acetabulum or “weight-bearing dome”

  
  
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  Loss of normal relationship between the femoral head and the superior acetabulum (incongruence)

  
  
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  Early or late posterior instability of the hip joint

  
  
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  Severe impaction injuries of the femoral head

1.3 Muscle dysfunction

Matta and Olson [6] reported normal hip strength in 186 (83%) of 224 patients with an acetabular fracture treated with a single approach at a 2-year minimum follow-up. Hip muscle weakness strongly correlated with clinical outcome as measured by the Postel-d’Aubigné score [7] and with radiographic evidence of osteoarthritis.

1.4 Radiology and classification

In 1964 Letournel and Judet [8] published their landmark work that described their radiographic assessment, classification, and early results of operative acetabular fracture treatment. This study and the subsequent work of Letournel form the basis of modern operative care of acetabular fractures. Currently, a displaced fracture of the acetabulum is usually considered an operative problem unless specific indications are present allowing a predictably successful outcome with nonoperative treatment.

Decision making in surgical treatment of acetabular fractures is challenging. An understanding of radiology and fracture classification is a necessary prerequisite in the decision-making process for operative versus nonoperative treatment. This chapter describes a modern day workup of acetabular fractures, including x-rays, computed tomographic (CT) scans, and image intensification stress examinations under anesthesia that are used to determine the optimal treatment. Nonoperative indications, the choice of operative approach for internal fixations, as well as indications for total hip arthroplasty (THA) are discussed and outcomes in current literature presented.

3.1 Judet and Letournel acetabular fracture classification

Judet and Letournel classification system of acetabular fractures describes ten fracture types. There are five elementary patterns—posterior wall, posterior column, anterior wall, anterior column, and the transverse types. There are five associated patterns—posterior column and posterior wall, transverse and posterior wall, T-shape, anterior and posterior hemitransverse, and the associated both-column pattern. The basic description of these fracture types is based on AP and two 45° oblique x-rays known as Judet views (iliac oblique and obturator oblique) [8].

3.2 AO/OTA Fracture and Dislocation Classification

AO Foundation has also developed a classification system for acetabular fractures [9]. There are three main classification groups in the AO/OTA Fracture and Dislocation Classification: A, B, and C. Type A fractures are isolated wall or column fractures. Type B includes those partial articular fractures that have anterior and posterior column involvement. Type C fractures include the associated both-column patterns.

However, for the purpose of this chapter Judet and Letournel classification is used because most published literature is based on this system.

4.1 How common is nonoperative treatment?

Olson and Matta described [10] a series of 499 acetabular fractures, in which 57 were treated nonoperatively (11%). A total of 33 of those had a both-column fracture pattern (58%). Only 17 non–both-column fractures of the 499 fractures fulfilled the criteria for nonoperative treatment.

4.2 How are patients treated nonoperatively?

Nonoperative treatment typically consists of mobilization, with approximately 10−15 kg weight bearing on the affected side if associated injuries and comorbidities permit. Weight bearing is progressively advanced over 3 months.

4.3 Assessment of the extent of articular involvement: the roof-arc angle

Matta et al [11–13] developed the concept of roof-arc measurements to assess the amount of acetabulum left intact after fracture. This idea is an extension of the work of Rowe and Lowell [4] who suggested that an undefined minimum amount of intact acetabulum was necessary for a successful outcome with nonoperative treatment. Olson and Matta [9] recognized that the radiographic landmark of the roof of the acetabulum reflects the portion of the acetabulum seen in tangent by the x-ray beam on a plain x-ray. If the roof is extended to include the medial wall of the acetabulum, it forms an “arc” that is a portion of the circumference of the circular acetabulum. The roof-arc angle describes the angle between a vertical line beginning at the center of the femoral head and a line from this point and the most superior displaced fracture line through the roof of the acetabulum measured on AP, obturator oblique, and iliac oblique x-rays. The concept of roof-arc measurements was developed in a retrospective review and validated prospectively [11−13].

However, rotation of the pelvis on the oblique views can vary with positioning. To overcome this limitation, Olson and Matta [10] proposed the use of CT to assess the superior acetabulum in place of roof-arc measurements ( Fig 2.5-1 ). The CT images describe the distance from the vertex of the acetabulum to the point where the subchondral ring of the acetabulum is violated by the fracture. Using the roof-arc or CT subchondral arc measures, the following criteria for nonoperative treatment were developed [10, 13]:

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  A minimum of superior acetabulum is intact, as judged by roof-arc measures of at least 45° on all three plain x-ray views (AP, obturator oblique, and iliac oblique), or the CT subchondral arc is intact in the superior 10 mm of the acetabulum.

  
  
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  The femoral head maintains a congruent relationship with the intact acetabulum on AP, obturator oblique, and iliac oblique x-rays, with all three taken out of traction.

  
  
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  There is no evidence of posterior hip instability. A low posterior wall acetabular fracture may be present while still having met minimum intact superior acetabular criteria.

Olson and Matta [10] reviewed a series of 23 patients treated nonoperatively. Eleven of them met all three criteria for nonoperative treatment. At the 1-year follow-up 9 (82%) of the 11 patients had a good or excellent clinical result. Twelve patients did not meet the criteria for nonoperative treatment. Only 5 (42%) of 12 patients had a good-to- excellent clinical result. Roof-arc measurements are not applicable to both column and posterior wall fractures.

4.4 Assessment of acetabular fractures for nonoperative treatment: stress examination under anesthesia

Tornetta [14] added to the criteria for nonoperative treatment by describing dynamic image intensification stress views. Tornetta recognized that incongruity may be present in positions other than those seen on plain x-rays. Range of motion was performed intraoperatively with image intensification to assess for incongruity. The fracture was treated operatively in case of or loss of congruence or between the femoral head and acetabulum (also known as subluxation) occurs during range of motion of the hip joint in the face of meeting the criteria described by Olson and Matta [10] for nonoperative treatment.

With the patient under anesthesia, the hip was rotated externally and internally in a flexed, extended, and abducted position. In each of the three positions, the relationship of the femoral head to the roof of the acetabulum was observed with image intensification. Subsequently, a force was applied in the direction of the displacement. AP, iliac oblique, and obturator oblique views were then taken to assess the congruency of the hip joint.

A total of 41 fractures with roof-arc measurements of 45°, a subchondral CT arc of 10 mm, displacement of less than 50% of the posterior wall, and congruence on the AP and Judet views were evaluated with image intensification stress examination. Three of the 41 fractures were unstable on dynamic image intensification stress views; these patients underwent open reduction and internal fixation (ORIF). The remaining 38 fractures were treated nonoperatively. Overall results were good or excellent for 91% of patients at a mean of 2.7-year follow-up [14].

4.5 Nonoperative treatment of posterior wall fractures based on size on CT scans and stress examination under anesthesia

Two clinical and two cadaveric studies used CT assessment of the size of a posterior wall acetabular fracture as a predictor of hip instability [15–18]. Importantly, all four studies described different methods to determine the size of the fracture fragment; therefore, the amount of posterior wall involvement is not comparable across studies. One study [16] created fractures in 16 cadavers and correlated the size of the posterior wall on CT scans with stability at 90° of flexion and 20° of abduction. Another study [18] evaluated the stability of posterior wall fractures related to the fragment size in a series of 22 cadavers. However, both studies were done on cadavers and thus do not consider the normal muscle tone that can contribute to stability of the hip joint in a patient. A series [15] reviewed 26 patients who presented with posterior hip fracture dislocations, and another series [17] reported on 33 consecutive patients with isolated posterior wall fractures. In both studies CT scans were used to compare the fractured side to the intact, contralateral side. However, different measurement techniques were used. Moed et al [17] correlated the size of posterior wall fractures with stress examination under anesthesia. An axial CT scan cut at the level of the largest defect of the posterior wall fracture fragment was used. The percentage of the medial-to-lateral dimension of the fractured fragment was calculated relative to the intact contralateral medial-to-lateral dimension ( Fig 2.5-2 ). All four fractures involving less than 20% of the posterior wall were stable with stress examination under anesthesia, whereas all six fractures involving more than 40% were unstable. Fractures involving 20−40% of the posterior wall were indeterminate: a total of 9 (38%) of 23 were unstable and 14 (61%) of 23 stable. Therefore, fractures involving between 20% and 40% of the posterior wall, for which nonoperative treatment is being considered, should undergo a stress examination under anesthesia to evaluate stability. The assessment of the size of the posterior wall fragment has been shown to have high-interobserver and intraobserver reliability, with an intraclass correlation coefficient of > 0.8 regardless of observers’ experience level [19].

A series of 21 consecutive patients with posterior wall acetabular fractures were found to be stable with stress examination under anesthesia and were treated nonoperatively [20]. All 18 patients with a minimum follow-up of 2 years had at least a good clinical outcome based on the modified Merle d’Aubigné score [7] and no radiographic evidence of arthritis. However, CT follow-up was not performed. A false-negative outcome, defined as the hip stable on examination but presenting with late instability, was not observed in this series. To our knowledge, these results have not been duplicated to date.

4.6 Current indications for nonoperative treatment

Related posts:

2.2 Biomechanics of acetabular fractures 2.6 General assessment and perioperative management of acetabular fractures 2.1 Anatomy of the acetabulum 2.4 Defining the injury: assessment and principles of management of acetabular fractures 2.3 Pathoanatomy and classification of acetabular fractures 1.8.4 The management of the injured pelvic ring: internal fixation of the anterior pelvic injuries—open book (type B1)

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