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Advanced trauma life support radiographic trauma series: Part 3--the pelvis radiograph.

Introduction

In this series of papers we are reviewing the radiographs performed as part of the advanced trauma life support (ATLS) trauma series, and this paper deals with pelvic radiographs.

Pelvic injuries often occur due to high velocity injuries such as road traffic accidents, and may be associated with polytrauma (i.e. multiple injuries) (see case study 1 and case study 2). Low velocity pelvic injuries such as falls usually occur in the elderly but may occur in young athletic patients due to sudden muscular contraction leading to avulsion injuries (Koval & Zuckerman 2006). Pelvic ring fractures account for 1.5% of all joint fractures and have a high morbidity and mortality (Theumann et al 2002, Sathy et al 2009). Life-threatening major haemorrhage is the leading cause of death in patients with a pelvic fracture and may occur if the pelvic vessels are injured. It may also be due to accompanying extrapelvic injuries (ATLS 2004, Balogh et al 2007). Methods of immediate haemorrhage control include wrapping a pelvic binder around the pelvis and external fixation (Koval & Zuckerman 2006). The use of pelvic angiography with embolisation may improve patient outcomes if haemorrhage continues despite these measures (Wiss 2001).

Structures such as the bladder, urethra, rectum and uterus are at risk due to sharp bone edges of the fracture lacerating adjacent organs. The elastic recoil of the tissues may result in the bone fragments returning to a near-normal position. As a result, even minimally displaced pelvic fractures may be associated with significant organ damage (case study 2). Therefore, injury severity cannot be predicted according to the degree of displacement seen radiographically (Raby et al 2005, Gardner et al 2010).

There should be a high index for suspicion for pelvic fractures to enable rapid identification in order to reduce the risk of fatality (Raby et al 2005). It is important to recognise when interpreting these films that some fractures, such as posterior fractures involving the sacrum and sacro-iliac joints, are not always visible (Lunsjo et al 2007).

Anatomy

The pelvic cavity contains organs such as the urinary bladder, the rectum, the inferior parts of the ureters and the reproductive system, as well as blood vessels, lymphatics and nerves.

The bony pelvis is a ring of bone formed by the two innominate bones anteromedially, the sacrum posteriorly and the coccyx which is inferior to the sacrum. The innominate bones consist of three parts, namely the ilium, ischium and pubis (Moore et al 1999). The pelvis has several joints. The lumbosacral joints are articulations formed by the intervertebral disc between the fifth lumbar vertebral body and the first sacral vertebral body. The sacrococcygeal joint unites the sacrum and the coccyx. The sacroiliac joints are strong articulations between the sacrum and the ilium. The pubic symphysis is where the innominate bones join anteriorly in the midline. There are anatomical differences between the male and female pelves. The female pelvis is broader and wider as an adaptation for childbearing (Moore et al 1999). Figure 1 illustrates the main anatomical features of the bony pelvis.

The pelvis is described as having three bony rings which are shown in Figure 2. The main pelvic ring contains the pubic symphysis and the sacroiliac bones. The two smaller rings, which are known as the obturator foramina, are formed by the pubic and is chial bones (Raby et al 2005). The pelvis is divided into the 'true' (lesser) pelvis and the 'false' (greater) pelvis by the pelvic brim. The pelvic brim is formed by arcuate lines passing from the sacral promontory to the superior border of the pubis anteriorly. The 'true' pelvis is below the pelvic brim and contains the pelvic viscera. The 'false' pelvis is above the pelvic brim and contains some of the abdominal viscera (Koval & Zuckerman 2006).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

The bony pelvis is stabilised by several strong ligaments. The long and short posterior sacroiliac ligaments, the interosseous ligaments within the sacroiliac joints and the sacrotuberous ligaments all resist forces leading to vertical translation between the ilia and the sacrum. The anterior sacroiliac, symphyseal and sacrospinous ligaments are arranged transversely and resist forces that lead to rotation of the pelvis (Theumann et al 2002)

Plain pelvic radiographic views

A portable pelvis radiograph taken in the resuscitation room is usually the first line investigation performed to diagnose pelvic fractures in patients with major trauma. It is used as a screening test as part of the ATLS trauma series following the primary survey (i.e. the initial clinical assessment) to identify pelvic fractures that may need further investigation. This view is taken with the patient supine and the feet approximately 15 degrees internally rotated. The central beam is directed vertically towards the mid-portion of the pelvis. The antero-posterior (AP) pelvis radiograph should demonstrate the iliac bone, sacrum, pubis, ischium, proximal femur, greater trochanter and lesser trochanters (Nicholas 2006).

Additional views include the pelvic inlet and outlet views, and Judet views. The pelvic inlet (superior pelvic aperture) is the opening into the 'true' pelvis which contains the urinary bladder and rectum as well as the uterus in females. This view is taken with the patient supine and the x-ray tube angled 45 degrees inferiorly and perpendicular to pelvic brim. This view is useful for diagnosing and assessing the degree of displacement of the sacroiliac joint, sacrum or iliac wing. Additionally, it may be useful to diagnose internal or external rotation of the hemipelvis, pubic diastasis (separation) or overlap and the presence of subtle sacral fractures or sacral impaction (Koval & Zuckerman 2006, Nicholas 2006). The pelvic outlet view may demonstrate the magnitude of vertical hemipelvis displacement. Sacral foramina as well as some sacral/pubic rami fractures may be visualised better on the outlet view than the AP. The outlet view is obtained with the patient supine and the X-ray tube angled 45 degrees superiorly and perpendicular to the pelvic brim (Koval & Zuckerman 2006, Nicholas 2006). Oblique Judet views are 45 degree internal and external rotation views. They are useful for visualisation of suspected acetabular fractures (Theumann et al 2002).

Interpretation of the plain AP pelvic radiographs

An adequate AP pelvis view will include the anatomy from the top of both the iliac crest superiorly through to the iliac tuberosities and will include the lesser trochanters of the femur as shown in Figure 1. The lateral margins of the film should include the anterior portions of the iliac wings. The radiographic exposure technique should demonstrate good bone detail. A systematic inspection of the radiograph should be made. Firstly, the main pelvic ring and the two small rings should be examined for continuity. Following this, the sacroiliac joints should be inspected. They should have equal widths. The pubic symphysis is examined. The width of the joint should not be more than 5mm. Additionally, the superior surfaces of the pubic bones should align. The sacral foramina are then assessed for any evidence of disruption of the smooth arcuate lines which would indicate a fracture (see Figure 3). Both sides should be compared (Raby et al 2005). Finally, the acetabula should be examined. The continuity of the four lines shown in Figure 4 should be assessed. These lines are: the iliopectineal line which is formed by the anterior column of the acetabulum, the ilioischial line which is formed by the posterior column of the acetabulum, the anterior and posterior lips of the acetabulum (Solomon et al 2001, Wheeless 2008).

Patterns of pelvic injury

The Young and Burgess classification system may be used to describe patterns of pelvic injury and categorises injuries according to four mechanisms (Koval & Zuckerman 2006):

Lateral compression

Lateral compression occurs due to a laterally applied force and may result in transverse or oblique fractures of the pubic rami which may be either ipsilateral or contralateral to a posterior injury. Lateral compression injuries are subdivided into:

* Type I--Sacral compression on the side of impact associated with coronal pubic rami fractures.

* Type II--Posterior iliac wing fracture or sacroiliac joint disruption on the side of impact.

* Type III--An external rotation injury due to force being transmitted to the contralateral hemipelvis resulting in disruption of the sacroiliac, sacrotuberous and sacrospinous ligaments (Koval & Zuckerman 2006, Slater & Baron 2010).

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

AP compression

AP compression injuries include external rotation injuries, diastasis of the pubic symphysis or longitudinal fractures of the pubic rami. This occurs due to direct application of force to the pubis or the posterior pelvis or indirect application of force transferred via the lower limbs (Theumann et al 2002, Koval & Zuckerman 2006). AP compression injuries are subdivided into:

* Type I--Diastasis of the pubic symphysis of less than 2.5cm or anterior sacroiliac joint disruption. There may be longitudinal fractures of the pubic rami. The sacrotuberous, sacrospinous and posterior sacroiliac ligaments remain intact.

* Type II--Diastasis of the pubic symphysis of more than 2.5cm, widening of the anterior sacroiliac joint caused by disruption of the anterior sacroiliac, sacrotuberous and sacrospinous ligaments. The posterior sacroiliac ligaments remain intact.

* Type III (open book fracture)--There is complete disruption of the pubic symphysis and the sacroiliac joint. This leads to extreme rotational instability and lateral displacement. The anterior and posterior sacroiliac, sacrotuberous and sacrospinous ligaments are disrupted. This injury is associated with a high risk of vascular injuries and haemorrhage (Koval & Zuckerman 2006, Slater & Baron 2010).

Vertical shear

Vertical shear is due to longitudinally applied forces and may result in diastasis of the pubic symphysis and complete disruption of the sacrotuberous, sacrospinous and sacroiliac ligaments. These injuries are highly unstable (Koval & Zuckerman 2006, Slater & Baron 2010).

Combined mechanical injuries

Combined mechanical injuries involve a combination of patterns and are often due to crush injury. Lateral compression with vertical shear is the most common combination (Koval & Zuckerman 2006).

The main limitation of this and other classifications of pelvic fracture patterns is that there is a degree of inter- and intraobserver variability among orthopaedic surgeons when applying it. However, this degree of variability is less when the classification systems are applied by specialists in pelvic surgery (Koo et al 2008, Furey et al 2009).

Pelvic fractures

Disruption of the main pelvic ring

A fracture at one site is very likely to be associated with disruption of the ring at a second site. Disruption of the ring is not necessarily a fracture of a bone. For example, the ring may be broken by diastasis of the pubic symphysis or the sacroiliac joint due to ligamentous disruption as shown in Figure 5 (Solomon et al 2001, Raby et al 2005).

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

Acetbular fractures

Acetabular fractures most commonly involve disruption of the acetabular socket when the hip is driven backwards during a road traffic accident. Acetabular fractures are frequently comminuted and osteoarthritic degeneration is a potential long-term consequence. Judet views and computer tomography (CT) scanning are needed to classify the type of acetabular fracture and to guide treatment (Dandy & Edwards 2004). Examples of acetabular fractures are shown in Figure 6.

Sacral fractures

Sacral fractures are often difficult to detect on the AP radiograph and commonly lead to missed or delayed diagnosis. Up to a quarter of sacral fractures are associated with neurological injury (Mehta et al 2006, Slater & Baron 2010). Impacted vertical fractures of the sacrum and nondisplaced fractures of the posterior sacroiliac complex are stable. Fractures may appear as asymmetry of the sacral arcuate lines. Diastasis of the fracture of more than 5mm and ligamentous disruption are features of unstable sacral fractures (Wheeless 2008).

Coccygeal fractures

Fractures of the coccyx result from a direct impact such as a fall onto the buttocks. The diagnosis is made clinically and radiography is unnecessary as findings do not change the management (Dandy & Edwards 2004, Raby et al 2005).

Iliac wing fractures

Fractures of the iliac wing occur due to a direct impact or crush injury. An isolated fracture of the iliac wing with an intact pelvic ring is a stable injury and may be treated non-operatively provided that it is not associated with significant complications such as haemorrhage or visceral injury (see Figure 7) (Dandy & Edwards 2004, Abrassart et al 2009).

Pubic ramus fractures

Pubic rami fractures are common in the elderly patients with osteoporosis following falls. They may be associated with posterior ring injuries (Solomon et al 2001, Cosker et al 2005). Figure 8 shows several examples of pubic rami fractures.

Avulsion of an apophysis

These fractures usually result from repeated or sudden violent muscle contraction in young athletic patients (Solomon et al 2001, Raby et al 2005). For example, Figure 9 shows avulsion fractures of the anterior superior iliac spine. The anterior superior iliac spine is the attachment of the sartorius and the tensor fascia lata.

Further radiological investigations

Fractures identified on plain radiography may be further investigated to delineate the fracture pattern by CT scanning. CT is very useful for the assessment of the posterior aspect of the pelvis, including the sacrum and the sacroiliac joint. Magnetic resonance imaging (MRI) is more accurate than CT for imaging of the genitourinary and pelvic vascular structures, however, is usually not practical as it limits access to the injured patient, takes longer to perform than other imaging modalities and is not immediately available in some settings (Koval & Zuckerman 2006).

[FIGURE 7 OMITTED]

There are several interventional radiological techniques to investigate and treat significant soft tissue injuries. Pelvic angiography and embolisation to control haemorrhage due to damage to pelvic vessels has reduced the mortality associated with pelvic fractures (case study 1). Investigations for bladder and urethral injury include intravenous cystourethrograms (intravenous contrast material is used to visualise the bladder and ureters on plain radiographs) or retrograde cystourethrograms (the contrast material is injected into the urethra and flows into the bladder).

Several studies have shown that the sensitivity of the AP pelvis is low and have claimed that there is a diminishing role for routine AP pelvis radiographs in trauma (Berg et al 1996, Guillamondegui et al 2002, Their et al 2005). A study of the radiological findings of 1386 patients who had undergone multidetector CT in serious blunt trauma revealed that only 55% of pelvic fractures were detected by plain pelvic radiography. The sensitivity of pelvic radiography varied depending on the anatomical region. For example, the sensitivity was better antero-inferiorly (i.e. pubic symphysis, pubic ramus and proximal femur) and was poor posteriorly (i.e. sacroiliac joint and sacrum) (Their et al 2005). It has been suggested that routine AP pelvis radiography often adds little to the management of the trauma patient and that haemodynamically stable patients who undergo an abdominopelvic CT during their immediate management do not require an AP pelvis radiograph (Berg et al 1996, Guillamondegui et al 2002, Vo et al 2004, Kessel et al 2007). This view is controversial. Some have argued that the role of the AP pelvis radiograph is broader than to simply diagnose pelvic fractures. It may be considered as having a role as an adjunct to the ATLS secondary survey by guiding the process of diagnosis and planning during the ATLS assessment. Omission of this rapid screening test could potentially cause delays in the appreciation of the full extent of injury (Flint 2002).

[FIGURE 8 OMITTED]

[FIGURE 9 OMITTED]

Conclusion

It is essential that pelvic fractures are identified rapidly in cases of major trauma due to the risk of life-threatening haemorrhage. Although a systematic approach to interpretation of the AP pelvis radiograph increases the identification of injuries, it may not be possible to visualise all fractures. Additional plain radiographic views such as pelvic inlet, outlet and oblique Judet views may facilitate diagnosis. Other imaging modalities such as CT are useful to provide more detailed information in haemodynamically stable patients.

Case study 1

A 59 year old woman was driving a car with a seatbelt and headrest when she had a high-velocity impact to the front of her vehicle. She was extracted from the vehicle by an ambulance crew and had a pelvic binder applied. She was taken to A&E where she had a Glasgow Coma Scale (GCS) score of 14, pulse rate of 120 beats/min, respiration rate of 24/min, and blood pressure of 104/68 mm Hg. Following primary survey she had radiographs of her pelvis showing pelvic ring disruption with bilateral sacroiliac disruption and left superior and inferior pubic rami fractures. Initial hemoglobin level was 6.6 g/dl and the patient received 2 units of blood but remained haemodynamically unstable. Because of the fracture pattern and likelihood of ongoing pelvic hemorrhage, pelvic angiography was performed. Pelvic angiography revealed substantial bleeding from the left internal pudendal artery. The feeding vessel was selectively cannulated and embolised successfully. Four days later, the patient had open reduction and internal fixation of the pelvis, and was subsequently discharged on day 16.

Case study 1

A 39 year old construction site worker got caught between two trucks for almost one minute. When the ambulance crew arrived, he was unable to stand and complained of pain over the left sacroiliac joint and abdomen. He was brought to A&E and following the primary survey, had pelvic radiographs revealing an 'open book' type of pelvic fracture with left and right sacroiliac joint disruption. An ultrasonogram of the abdomen revealed free fluid. Initial resuscitation efforts failed to provide haemodynamic stability and the patient was taken to theatre. After application of the external fixator, a midline laparotomy was performed. A liver laceration was identified and repaired. The patient remained haemodynamically stable and six days later underwent open reduction and internal fixation of the pelvis following a CT scan.

Provenance and Peer review: Commissioned by the editor; Peer reviewed; Accepted for publication August 2010.

Acknowledgements:

We would like to thank Caroline Morrison, Lead Radiographer Emergency Department, Queen's Hospital, Romford for her assistance.

References

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Ms M Chimutengwende-Gordon

MBChB, MSc, MRCS

Academic Orthopaedic Registrar, University College London Institute of Orthopaedic and Musculoskeletal Sciences, Royal National Orthopaedic Hospital, Stanmore, Middlesex

Mr W Khan

MBChB, MRCS, PhD

Academic Orthopaedic Registrar, University College London Institute of Orthopaedic and Musculoskeletal Sciences, Royal National Orthopaedic Hospital, Stanmore, Middlesex

Dr J Sidhu

MBBS, BSc

Senior House Officer Orthopaedics, Queen's Hospital, Romford

Mr N Maruthainar

MBBS, FRCS (Orth)

Consultant Orthopaedic Surgeon, Department of Trauma & Orthopaedics, Royal Free Hampstead NHS Trust, London

No competing interests declared

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Correspondence address: Wasim Khan, Academic Clinical Fellow, University College London Institute of Orthopaedics and Musculoskeletal Science, Royal National Orthopaedic Hospital, Stanmore, Middlesex, London, HA7 4LP, UK. Email: wasimkhan@doctors.org.uk
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Title Annotation:CLINICAL FEATURE
Author:Chimutengwende-Gordon, Mukai; Khan, Wasim; Sidhu, Jasmeet; Maruthainar, Nimalan
Publication:Journal of Perioperative Practice
Article Type:Report
Geographic Code:4EUUK
Date:Jan 1, 2011
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