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Emergencies in Clinical Radiology

Edited by Richard Graham, Ferdia Gallagher

Publisher:
Oxford University Press
Print Publication Date:
Jan 2009
Print ISBN-13:
9780199238439
Published to Oxford Medicine:
Aug 2010
DOI:
10.1093/med/9780199238439.001.0001

Disclaimer

Oxford University Press makes no representation, express or implied, that the drug dosages in this book are correct. Readers must therefore always check the product information and clinical procedures with the most up to date published product information and data sheets provided by the manufacturers and the most recent codes of conduct and safety regulations. The authors and the publishers do not accept responsibility or legal liability for any errors in the text or for the misuse or misapplication of material in this work. Except where otherwise stated, drug dosages and recommendations are for the non-pregnant adult who is not breastfeeding.

Musculoskeletal

Chapter:
Musculoskeletal
DOI:
10.1093/med/9780199238439.003.0011

  • General principles of fracture imaging [link]

  • Cervical spine trauma [link]

  • Thoracolumbar spine trauma [link]

  • Discitis [link]

  • Skull fractures [link]

  • Pelvic fractures [link]

  • Knee fractures [link]

  • Shoulder fractures and dislocations [link]

  • Hip fractures and dislocations [link]

  • Wrist fractures and dislocations [link]

  • Ankle fractures and dislocations [link]

  • Sternal and rib fractures [link]

  • Septic arthritis [link]

  • Achilles tendon rupture [link]

  • Intramuscular haematomas [link]

  • Retained foreign body [link]

General principles of fracture imaging

Imaging

Radiographs

These are sensitive and readily available. It is the initial imaging modality used in the assessment of trauma. At least two views should be obtained in most cases of suspected bone injury.

CT

CT can better define injuries with complex fracture patterns, and identify intra-articular fracture fragments which can be important for surgical management. Modern multislice CT scanners can provide fast acquisition of isotropic volumetric data, minimizing motion artefacts and allowing reconstruction in the coronal and sagittal planes without loss of resolution. It is more difficult to detect solely trabecular, undisplaced fractures (e.g. some scaphoid fractures) with CT compared to MRI.

Where possible, the patient should be positioned so that the extremities can be scanned in a plane that does not include the rest of the body to minimize beam-hardening artefacts (e.g. holding the arm outstretched over the head). Images should be obtained with bone (e.g. window 2500/500HU) and soft tissue (e.g. window 300/50HU) reconstruction kernels. Thin sections as low as 0.5mm are routine in many centres. 3D volume rendering is a useful feature for some clinicians to help with pre-operative planning. CT images should be reviewed on both bone and soft tissue windows as diverse pathology can be present, e.g. pneumothorax, sternal fracture, bladder rupture. The scout image should also be scrutinized as it provides an additional global view.

MRI

MRI is not required for most fractures. It is mainly used to evaluate soft-tissue injuries, such as to the surrounding ligament or tendon, or to exclude occult fractures. MRI is very sensitive at detecting bone marrow abnormalities such as bone contusions or solely trabecular fractures.

Given that MRI has a significantly longer imaging time than CT it is often not practical in the emergency trauma setting, particularly when movement artefacts are likely. In addition, any contraindication to MRI may not be known (e.g. ferrous metal foreign bodies).

Bone scintigraphy

Bone scintigraphy is useful in the assessment of stress fractures. It also has a role in detecting occult fractures, although there is an increasing preference to use cross-sectional imaging modalities (CT, MRI) due to their improved anatomical information and to the relative non-specificity of scintigraphy. Local availability of each modality will usually determine the imaging strategy used.

Further reading

  1. 1.

    Resnick R and Kransdorf MJ (eds) (2005) Bone and Joint Imaging. Elsevier, Philadelphia, PA.
    Find This Resource

  2. 2.

    Lee JKT, Sagel SS, Stanley RJ and Heiken JP (eds) Computed Body Tomography with MRI Correlation. Lippincott William and Wilkins, Philadelphia, PA.
    Find This Resource

Musculoskeletal Musculoskeletal Cervical spine trauma

Aetiology and epidemiology

Up to 10% of unconscious patients from an RTA or fall have a serious injury to the cervical spine. About 50% of cervical spine injuries occur at C6/7; about 30% occur at C2.

Clinical features

Localized pain and restricted range of motion. Neurological deficits if there is cord injury.

Classification

C1; atlas

Jefferson’s fracture (unstable; Fig. 11.1)

This is a burst fracture of C1 from axial loading. There is outward displacement of the lateral masses with fractures of the anterior and posterior arches. Marked prevertebral swelling is often present.

Posterior arch fracture (stable)

Isolated fractures (unilateral or bilateral) of the posterior arch of C1 occur from hyperextension. Care should be taken to avoid diagnosing a fracture with a congenital cleft of the posterior arch (midline defect with smooth corticated margins).

C2; axis

Odontoid process fractures (types II and III are unstable; Fig. 11.2)

Type II fractures are the most common and are associated with non-union.

Fig. 11.2 Classification of odontoid process fractures: type I (avulsion fracture at the tip of the dens; should be differentiated from an os odontoideum), type II (fracture at the base of the dens), and type III (fracture extends into the body of C2).

Fig. 11.2
Classification of odontoid process fractures: type I (avulsion fracture at the tip of the dens; should be differentiated from an os odontoideum), type II (fracture at the base of the dens), and type III (fracture extends into the body of C2).

Hangman’s fracture (unstable) (Fig. 11.3)

This consists of bilateral fractures of the pars interarticularis of C2 from hyperextension. Anterior subluxation of the C2 body on C3 increases the risk of spinal cord injury.

Lower cervical spine fractures

Hyperextension injuries

Hyperextension dislocation (unstable) (Fig. 11.4)

There is injury to the anterior longitudinal ligament with disc disruption or an avulsion fracture at the anteroinferior margin of the vertebral body at the attachment of the annulus. This avulsion fragment is typically larger in width than height. Severe neurological deficit is often present. If there is no fracture, this injury can be difficult to detect with radiographs or CT with only prevertebral swelling present.

Extension teardrop fracture (unstable in extension) (Fig. 11.5).

This is an avulsion fracture at the anteroinferior margin of the vertebral body. The avulsion fragment is usually small (less than 25% of the AP vertebral body dimension) and typically larger in height than width. Neurological deficit is not usually present.

Fig. 11.4 Hyperextension dislocation. The avulsion fragment is typically larger in width than height.

Fig. 11.4
Hyperextension dislocation. The avulsion fragment is typically larger in width than height.

Fig. 11.5 Extension teardop fracture. The avulsion fragment is typically larger in height than width.

Fig. 11.5
Extension teardop fracture. The avulsion fragment is typically larger in height than width.

Flexion injuries

Hyperflexion sprain

This is a distracting injury to the posterior ligaments, usually without a fracture. Radiographs are frequently normal; occasionally widening of the interspinous distance with localized kyphosis is present. Chronic pain and instability can occur with conservative management.

Wedge fracture

See Musculoskeletal p. [link].

Bilateral facet joint dislocation (unstable) (Fig. 11.6)

This occurs from a high-magnitude flexion injury with ligamentous disruption particularly to the middle and posterior spinal columns. Neurological deficit (narrowing of the spinal canal) and vertebral artery injury is common. Radiographs typically show anterior displacement of the upper vertebra by more than 50% of the AP vertebral body dimension.

Flexion teardrop fracture (unstable) (Fig. 11.7)

This occurs from a high-magnitude flexion injury resulting in a large anteroinferior fracture fragment of the vertebral body and posterior ligamentous disruption (widening of the interspinous distance). The fracture fragment is typically 30 to 50% of the vertebral body. Neurological deficit is common.

Clay-shoveller’s fracture (stable) (Fig. 11.8)

This is an avulsion fracture of the spinous process at the attachment of the supraspinous ligament. It usually occurs at C6 to C7.

Fig. 11.6 Bilateral facet joint dislocation. There is usually anterior displacement of the upper vertebra by more than 50% of the AP vertebral body dimension.

Fig. 11.6
Bilateral facet joint dislocation. There is usually anterior displacement of the upper vertebra by more than 50% of the AP vertebral body dimension.

Fig. 11.7 Flexion teardrop fracture. The fracture fragment is typically 30 to 50% of the vertebral body.

Fig. 11.7
Flexion teardrop fracture. The fracture fragment is typically 30 to 50% of the vertebral body.

Fig. 11.8 Clay-shoveller’s fracture.

Fig. 11.8
Clay-shoveller’s fracture.

Compression injuries

Burst fracture

Musculoskeletal p. [link].

Flexion–rotation injuries

Unilateral facet joint dislocation (stable) (Fig. 11.9)

Radiographs typically shows anterior displacement of the upper vertebra by less than 50% of the AP vertebral body dimension. Neurological deficit may be present.

Fig. 11.9 Unilateral facet joint dislocation. There is usually anterior displacement of the upper vertebra by less than 50% of the AP vertebral body dimension.

Fig. 11.9
Unilateral facet joint dislocation. There is usually anterior displacement of the upper vertebra by less than 50% of the AP vertebral body dimension.

Imaging

In general, radiographs should be obtained in patients with neurology, neck pain or tenderness, or a distracting injury. The Canadian cervical spine rules or the NEXUS criteria (see box below) are decision protocols to exclude significant cervical spine pathology in low-risk patients. There is still debate as to which is more useful in terms of clinical performance. NICE (National Institute for Health and Clinical Excellence, UK) have issued guidelines based on the above two protocols (see box).

Canadian C-spine rules for clearing low-risk patients with suspected cervical spine injury

Patients must:

  • • Be alert (GCS 15), not intoxicated or with a distracting injury (e.g. long bone fracture, large laceration).

  • • Not be at high risk (age 65 or older, dangerous mechanism of injury or paraesthesia in extremities).

  • • Have a low risk factor (rear-end collision, ambulation at any time post-trauma, delayed onset of neck pain, absence of midline cervical tenderness, can maintain seated position in emergency department) that allows safe assessment of range of motion.

  • • Be able to actively rotate neck 45° right and left.

National Emergency X-Radiography Utilization Study (NEXUS) criteria for clearing low-risk patients with suspected C-spine injury

Patients must:

  • • Be alert (GCS 15), not intoxicated or with a distracting injury.

  • • Have no midline cervical tenderness.

  • • Have no focal neurological deficit.

NICE guidelines 2007

Patients should have plain radiography of the C-spine with any of the following:

  • • Neck pain or midline tenderness with: age 65 or older, or dangerous mechanism of injury.

  • • Unsafe to assess neck movement for reasons other than those above.

  • • Cannot actively rotate the neck 45° to the left or right.

  • • An urgent definitive diagnosis of C-spine injury is needed, e.g. pre-surgery

  • • It is considered safe to assess neck movement if the patient has a low risk factor (see above).

Radiographs

Protocol

AP (full cervical spine), AP (peg) and lateral views are commonly obtained. The lateral view should demonstrate the top of the T1 vertebral body.

The patient should not be placed in a position that would increase the risk of neurological deficit, e.g. log-rolling and a cervical collar should be considered.

Findings

  • • A: check adequacy and alignment (anterior vertebral body line, posterior vertebral body line, spinolaminar line, and spinous process line; clivus baseline) (Fig. 11.10).

  • • B: check bones, i.e. vertebral body height, fracture.

  • • C: check cartilage (discs) for uniform disc height.

  • • S: check soft tissues. Prevertebral swelling is an important indirect indicator of cervical trauma (more than 7mm or 1/3 vertebral body width at C1–4; more than 22mm or 1 vertebral body width at C5–7 is abnormal). The distance between the dens and C1 should be less than 3mm in adults and 5mm in children.

  • • The three spinal columns (anterior, middle, posterior) should be assessed (Fig. 11.11). Injuries involving more than one column are considered unstable.

Fig. 11.10 Lateral view of the cervical spine. (a) Anterior vertebral body line; (b) posterior vertebral body line; (c) spinolaminar line; (d) clivus baseline.

Fig. 11.10
Lateral view of the cervical spine. (a) Anterior vertebral body line; (b) posterior vertebral body line; (c) spinolaminar line; (d) clivus baseline.

Fig. 11.11 Denis three-column principle. The anterior column consists of the anterior longitudinal ligament and the anterior half of the vertebral body. The middle column includes the posterior longitudinal ligament and the posterior half of the vertebral body. The posterior column consists of the posterior bone arch and its ligaments.

Fig. 11.11
Denis three-column principle. The anterior column consists of the anterior longitudinal ligament and the anterior half of the vertebral body. The middle column includes the posterior longitudinal ligament and the posterior half of the vertebral body. The posterior column consists of the posterior bone arch and its ligaments.

CT

CT is indicated if there is a questionable abnormality on the radiographs or significant clinical concern despite normal plain radiographs. CT is also useful in evaluating the posterior elements or fractures with complex patterns. The entire cervical spine (base of skull to T1) is usually imaged; consider scanning down to T4 in unconscious patients.

MRI

MRI is used for assessing the cord and adjacent soft tissues. Adding a fat-suppressed sequence (e.g. STIR) helps in detecting these soft tissue injuries (cord, ligaments, intervertebral discs) and assessing if changes to a vertebral body are acute (high signal on fluid-sensitive sequences) or chronic (lack of high signal on fluid-sensitive sequences).

Differential diagnosis

Soft tissue injuries.

Complications

  • • Injuries to the cord and ligaments

  • • Epidural haematomas

  • • Vertebral artery dissection

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders, USA.
    Find This Resource

  2. 2.

    Resnick R and Kransdorf MJ (eds) (2005) Bone and Joint Imaging. Elsevier, Philadelphia, PA.
    Find This Resource

  3. 3.

    Lee JKT, Sagel SS, Stanley RJ and Heiken JP (eds) Computed Body Tomography with MRI Correlation. Lippincott William and Wilkins, USA.
    Find This Resource

  4. 4. NICE (2007) Head Injury: Triage, Assessment, Investigation and Early Management of Head Injury in Infants, Children and Adults. Clinical Guidelines from the National Institute for Clinical Excellence, CG56, available at http://www.nice.org.uk/nicemedia/pdf/cg56NICEGuideline.pdf.

Musculoskeletal Musculoskeletal Thoracolumbar spine trauma

Aetiology and epidemiology

The thoracolumbar junction is a common site for spinal fracture due to its wide range of motion. Most injuries are secondary to flexion or compression forces.

Clinical features

Localized pain and deformity. Neurological deficits if there is cord injury.

Wedge (compression) fracture (Fig. 11.12)

There is typically loss of height of the anterior vertebral body with preservation of the middle and posterior spinal columns. The posterior vertebral wall is intact with no posterior displacement of bone fragments. Severe wedge fractures are associated with injury to the posterior ligaments (demonstrated by widening of the interspinous distance).

Burst fracture

This is typically a vertically oriented fracture of the vertebral body with disruption of the posterior vertebral wall and retropulsion of bone fragments into the spinal canal. It is associated with fractures of the posterior elements.

Chance fracture seat-belt injury

This is typically a horizontally oriented fracture through the spinous process, pedicles and vertebral body. It occurs from flexion at the thoracolumbar region (level of a seat-belt) which results in distraction of the posterior elements. Significant intra-abdominal injury (e.g. to the small bowel or pancreas) is present in up to 50%.

Fracture–dislocation (unstable)

This is intervertebral subluxation or dislocation from disruption of all three spinal columns. Spinal cord injury is often present.

Fig. 11.12 Simplified diagrams of (a) wedge fracture, (b) burst fracture, (c) chance fracture and (d) fracture-dislocation of the spine.

Fig. 11.12
Simplified diagrams of (a) wedge fracture, (b) burst fracture, (c) chance fracture and (d) fracture-dislocation of the spine.

Imaging

The three spinal columns (anterior, middle, posterior) should be assessed. Injuries involving more than one column are considered unstable.

Radiographs

Protocol

AP and lateral views. The patient should not be placed in a position that would increase the risk of neurological deficit, e.g. log-rolling and a spinal board should be considered.

Findings

  • • Assess alignment and vertebral body height. Check the interpediculate distance (AP view) and the posterior vertebral body margin (lateral view). The interpediculate distance should get wider as you go down the spine.

  • • Adjacent localized haematoma can be detected by deviations of the paraspinal lines (Fig. 11.13).

Fig. 11.13 Localized bulging of the paraspinal lines can indicate a haematoma from an adjacent fracture.

Fig. 11.13
Localized bulging of the paraspinal lines can indicate a haematoma from an adjacent fracture.

CT

CT is useful in evaluating the posterior elements for fractures with complex patterns. Images should contain at least one full vertebra above and below the fracture. Check for any retropulsed bone fragment that may potentially be impinging on the cord.

MRI

MRI is used for assessing the cord and adjacent soft tissues (Musculoskeletal p. [link]; CNS chapters). Adding a fat-suppressed sequence (e.g. STIR) helps in detecting these soft tissue injuries (cord, ligaments, intervertebral discs) and assessing if changes to a vertebral body are acute or chronic.

Differential diagnosis

  • • Soft tissue injuries

Complications

  • • Injuries to the cord and ligaments

  • • Epidural haematomas

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders. USA
    Find This Resource

  2. 2.

    Resnick R and Kransdorf MJ (eds) (2005) Bone and Joint Imaging. Elsevier, Philadelphia, PA.
    Find This Resource

  3. 3.

    Lee JKT, Sagel SS, Stanley RJ and Heiken JP (eds) Computed Body Tomography with MRI Correlation. Lippincott William and Wilkins. USA
    Find This Resource

Musculoskeletal Musculoskeletal Discitis

Aetiology and epidemiology

Discitis and vertebral osteomyelitis often occur together. The thoracic and lumbar spine are most commonly affected. The routes of infection include haematogenous (e.g. in drug abusers or the immunocompromised) and ascending spread (via the Batson plexus from pelvic infections), and direct implantation.

Clinical features

Back pain with systemic symptoms of fever and weight loss. Onset is often slow and insidious, and diagnosis can be delayed for many months.

Imaging

MRI is the preferred imaging modality for suspected spinal infections.

Radiographs

Protocol

AP and lateral views.

Findings

  • • Abnormalities are usually not visible until several weeks after the onset of symptoms.

  • • There is typically rapid loss of disc space with destruction of the adjacent endplates.

  • • Late changes: bone sclerosis and spinal subluxation. TB is slower in progression compared to pyogenic organisms. With TB, there is typically preservation of disc spaces, calcified soft tissue abscesses and lack of severe bone sclerosis.

MRI

Protocol

  • • T1; T2 FS (or STIR); T1 FS+Gd.

  • • Axial and sagittal planes.

Findings

  • • T1: The involved disc and adjacent vertebrae are low in signal. The adjacent endplates are indistinct or destroyed.

  • • T2: The involved disc and adjacent vertebrae are high in signal (Fig. 11.14).

  • • T1+Gd: Epidural abscesses have wall enhancement and can be separated from the adjacent thecal sac. There is also enhancement of the disc and adjacent vertebrae.

  • • Check for extension into the paraspinal soft tissues.

Fig. 11.14 (a) Sagittal T1 MR image. Discitis of T10/11 (arrow) with osteomyelitis. The adjacent T10 and T11 vertebrae are hypointense. (b) Sagittal T2 MR image. The infected T10/11 disc (arrow) is hyperintense.

Fig. 11.14
(a) Sagittal T1 MR image. Discitis of T10/11 (arrow) with osteomyelitis. The adjacent T10 and T11 vertebrae are hypointense. (b) Sagittal T2 MR image. The infected T10/11 disc (arrow) is hyperintense.

CT

CT is less sensitive than MRI for spinal infections. It can detect paravertebral soft tissue involvement but is poor for visualizing epidural or subdural spread.

Nuclear medicine

Radionuclide imaging is used when there are no localizing symptoms. It has a high sensitivity for spinal infections shortly after the onset of symptoms. Bone scintigraphy using MDP labelled with Tc99m is most often used.

Differential diagnosis

  • • Inflammatory spondylitis.

  • • Spinal tumours.

Management

  • • Intravenous antibiotics.

  • • Immobilization.

Complications

  • • Neurological deficits occur in up to 40% of patients.

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders USA.
    Find This Resource

  2. 2.

    Lee JKT, Sagel SS, Stanley RJ and Heiken JP (eds) Computed Body Tomography with MRI Correlation. Lippincott William and Wilkins.
    Find This Resource

Musculoskeletal Musculoskeletal Skull fractures

Clinical features

Most present without any neurology. May have loss of consciousness particularly with associated intracranial injury. Basal skull fractures have characteristic signs: CSF leak from the nose or ears, raccoon eyes (bruising around the eyes), and Battle’s sign (bruising over the mastoids).

Classification

Undisplaced linear skull fracture

These are the most common type of skull fracture. They can cause epidural haemorrhage or venous sinus thrombosis if they cross an artery or venous sinus. However, these fractures are usually of no clinical significance.

Basal skull fracture

These are usually associated with a dural tear and are typically found at three anatomical sites: temporal bone, occipital condyle, and clivus. Adjacent cranial nerves may be injured.

Depressed skull fractures

These comminuted fractures are often located at the frontoparietal bone. When the depressed fragment lies deeper than the adjacent inner table of the skull, surgical intervention is usually required.

See Musculoskeletal p. [link] for facial fractures.

Skull fractures are associated with cervical spine injuries in about 15% of cases.

Imaging

Evidence-based guidelines indicate that skull radiographs should not be requested for mild head injuries. If there is concern about an intracranial haemorrhage, CT should be requested; any skull fracture can be assessed at the same time.

Radiographs

Protocol

  • • Lateral and AP frontal views. The AP is often substituted with an AP axial (Towne’s) view with trauma to the occipital bone.

Findings

  • • Fractures are lucent lines with irregular branches. Vascular markings are less lucent with sclerotic margins and have smoothly tapering branches. Suture lines occur in characteristic anatomical locations.

  • • Depressed fractures appear sclerotic.

  • • Check for a fluid level in the sphenoid sinus on the lateral view. This finding is suggestive of a basal skull fracture.

CT

CT is often requested if there is a clinical concern for intracranial haemorrhage. Any skull fracture present can also be assessed on bone window settings.

Differential diagnosis

  • • Intracranial injury.

Management

  • • Usually conservative, particularly when there is no neurology. Surgery is sometimes required with depressed skull fractures.

Complications

  • • Intracranial injury, particularly haemorrhage.

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders. USA
    Find This Resource

Musculoskeletal Pelvic fractures

Aetiology and epidemiology

Pelvic fractures account for about 3% of all fractures. They can occur with minor trauma in elderly individuals or with major injury, e.g. RTA.

Clinical features

  • • Pelvic tenderness with pelvic springing.

  • • Pelvic instability on bimanual compression or distraction.

Classification

The pelvis is a series of bony rings: the main pelvic ring and two smaller rings formed by the pubic rami (Fig. 11.15). It is unusual to break a ring in only one place and a second fracture or dislocation should be actively sought.

Fig. 11.15 Kane classification of pelvic fractures: type I (no break to the main pelvic ring), type II (single break), type III (two breaks) and type IV (acetabular fracture).

Fig. 11.15
Kane classification of pelvic fractures: type I (no break to the main pelvic ring), type II (single break), type III (two breaks) and type IV (acetabular fracture).

Type I fractures (stable)

These fractures do not disrupt the main pelvic ring. They include avulsion fractures, single ramus fractures, and isolated fractures of the iliac wing or sacrum; (Fig. 11.16).

Fig. 11.16 Tendon insertion sites at various pelvic apophyses.1 anterior superior iliac spine (sartorius, tensor fascine latae); 2 ischial tuberosity (hamstrings); 3 anterior inferior iliac spine (rectus femoris)

Fig. 11.16
Tendon insertion sites at various pelvic apophyses.1 anterior superior iliac spine (sartorius, tensor fascine latae); 2 ischial tuberosity (hamstrings); 3 anterior inferior iliac spine (rectus femoris)

Type II fractures (stable)

These disrupt the main pelvic ring in only one place. They include ipsilateral fractures of both pubic rami and subluxation of the sacroiliac joint or pubic symphysis (may have a fracture nearby). Diastasis of the symphysis pubis greater than 15mm and symphyseal disruption with overlapping of the pubis represent anterior injuries that should strongly raise the possibility of posterior disruption of the pelvic ring.

Type III fractures (unstable)

These fractures disrupt the main pelvic ring in two places. They include straddle fractures (bilateral fractures involving both pubic rami or dislocation of the symphysis pubis), and Malgaigne’s fractures (disruption of both the anterior and posterior pelvic ring). Type III fractures are associated with excessive bleeding, urethral or visceral damage, and nerve damage.

Type IV fractures (acetabular fractures)

Acetabular fractures occur with impact of the femoral head against the acetabulum especially with posterior hip dislocations (Musculoskeletal p. [link]). Assessment should be made of four bony landmarks: the anterior acetabular rim, the posterior acetabular rim, the iliopubic (anterior) column, and the ilioischial (posterior) column.

Imaging

Radiographs

Protocol

AP pelvis. Optional views include outlet, inlet and oblique (Judet) views to assess the acetabulum.

Findings

  • • Sacral fractures can be difficult to detect—check that the arcuate lines are not disrupted.

  • • Avulsion injuries occur in young people and can be recognized from their characteristic location near an apophysis (e.g. ischial tuberosity for the hamstrings, anterior inferior iliac spine for the rectus femoris) (Fig. 11.16).

CT

CT can evaluate complex fracture patterns such as those involving the acetabulum. CT can also assess injuries to the internal pelvic viscera.

Differential diagnosis

  • • Hip fractures

  • • Injury to the internal pelvic organs

Complications

Pelvic fractures are associated with major trauma and injuries to the internal pelvic organs are frequent. This includes injury to the:

  • • Urinary tract

  • • Pelvic vessels and nerves

  • • Pelvic viscera

Further radiological assessment is usually done with CT.

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders, USA.
    Find This Resource

  2. 2.

    Lee JKT, Sagel SS, Stanley RJ and Heiken JP (eds) Computed Body Tomography with MRI C 2. Bone and Joint Imaging. Elsevier 2005, USA.
    Find This Resource

Musculoskeletal Knee fractures

Aetiology and epidemiology

Knee fractures are caused by direct or indirect forces.

Clinical features

Localized pain and swelling at the knee. Inability to straight leg raise with transverse patellar fractures.

Classification

Distal femoral fractures

Usually occur from axial loading with varus or valgus stress. See Fig. 11.17.

Fig. 11.17 Distal femoral fractures can be classified as (1) supracondylar, (2) intercondylar, or (3) condylar.

Fig. 11.17
Distal femoral fractures can be classified as (1) supracondylar, (2) intercondylar, or (3) condylar.

Patellar fractures

Caused by direct trauma or indirectly from contraction of the quadriceps muscle. Fractures are usually transverse (∼50 to 80%) and occur from indirect force.

Care should be taken to avoid diagnosing a fracture with a bipartite patella (a normal variant where there is a separate ossification centre in the superolateral patellar corner).

Dislocations of the patella occur laterally from direct or indirect forces. Predisposing conditions include an abnormally high patella (patella alta) and a shallow femoral trochlear groove. Dislocation is often transient. Axial radiographs may show associated osteochondral fractures of the medial patellar facet and the lateral femoral condyle.

Proximal tibial fractures

Tibial plateau fractures (Fig. 11.18) usually occur from valgus stress (e.g. car bumper collision) and often involve the lateral plateau.

Fig. 11.18 Schatzker classification of tibial plateau fractures: type I (split fracture of the lateral tibial plateau without depression), type II (split fracture of the lateral tibial plateau with depression), type III (depression fracture of the lateral tibial plateau without splitting), type IV (fracture of the medial tibial plateau; may have split and/or depression), type V (split fracture of the medial and lateral tibial plateaux), and type VI (usually comminuted fracture that separates the articular surface from the diaphysis).

Fig. 11.18
Schatzker classification of tibial plateau fractures: type I (split fracture of the lateral tibial plateau without depression), type II (split fracture of the lateral tibial plateau with depression), type III (depression fracture of the lateral tibial plateau without splitting), type IV (fracture of the medial tibial plateau; may have split and/or depression), type V (split fracture of the medial and lateral tibial plateaux), and type VI (usually comminuted fracture that separates the articular surface from the diaphysis).

Proximal fibular fractures

These can occur as part of a Maissoneuve fracture (associated ankle fracture).

Injury to internal soft tissue structures may be present. Fractures of the tibial spine may indicate injury to the cruciate ligaments; an avulsion fracture at the tibial insertion of the lateral collateral ligament (Segond fracture) is strongly associated with an injury to the anterior cruciate ligament.

Imaging

The Ottawa knee rules provide practical guidelines in selecting patients for radiographs. This consists of any one of:

  • • Age 55 or over

  • • Tenderness at the fibular head

  • • Isolated tenderness of the patella

  • • Inability to flex to 90°

  • • Inability to weight-bear both immediately and at assessment for four steps.

Radiographs

Protocol

AP and lateral views are standard. A skyline (axial) view increases detection of patellar fractures. Oblique views can be useful in detecting subtle tibial plateau fractures.

Findings

  • • Some tibial plateau fractures are difficult to detect: look for an area of sclerosis and lateral displacement of the tibial margin.

  • • A lipohaemarthrosis (Fig. 11.19) indicates an intra-articular fracture.

Fig. 11.19 Lateral knee radiograph showing a lipohaemarthrosis taken with a horizontal beam. A straight fluid line (arrow) is demonstrated at a fat–blood interface (fat above; blood below) indicating the presence of an intra-articular fracture.

Fig. 11.19
Lateral knee radiograph showing a lipohaemarthrosis taken with a horizontal beam. A straight fluid line (arrow) is demonstrated at a fat–blood interface (fat above; blood below) indicating the presence of an intra-articular fracture.

CT

CT can better define injuries with complex fracture patterns, such as fractures of the tibial plateau where articular depression can be difficult to assess with radiographs.

MRI

MRI is the test of choice for assessing associated injuries to the ligaments, menisci and cartilage. MRI can be used in the acute situation e.g. when there is a suspicion of posterolateral corner injury or if the patient is a professional athlete.

Protocol (one of many available)

  • • PD FS; T2 FS; sagittal plane. T1; T2 FS; coronal plane. T2 FS; axial plane.

Findings

  • • Meniscal tears are linear high signal on fluid sensitive sequences that disrupts an articular surface

  • • Cruciate tears demonstrate loss of normal fibres with associated high signal on fluid-sensitive sequences.

Differential diagnosis

  • • Soft tissue injuries

Complications

  • • Neurovascular injury

  • • Compartment syndrome

  • • Delayed union/non-union

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders, USA.
    Find This Resource

  2. 2.

    Resnick R and Kransdorf MJ (eds) (2005) Bone and Joint Imaging. Elsevier, Philadelphia, PA.
    Find This Resource

Musculoskeletal Shoulder fractures and dislocations

Aetiology and epidemiology

Proximal humeral fractures usually occur in the elderly. Glenohumeral dislocations are more common in young adults.

Clinical features

Localized pain and swelling at the shoulder.

Classification

Proximal humeral fractures (Fig. 11.20)

One-part fractures are most common (∼80% of proximal humeral fractures).

Fracture-dislocation is a combination of a fracture and the articular surface of the humeral head being displaced outside the joint space.

Glenohumeral dislocations

Usually anterior (∼90%) and posterior (∼4%) dislocations. Inferior, superior and intrathoracic dislocations are rare.

Anterior dislocations are associated with a fracture at the anterior glenoid rim (Bankart) and a fracture at the posterolateral aspect of the humeral head (Hill–Sachs). Posterior dislocations can result from fitting or electrocution injuries and are associated with a fracture at the anterior aspect of the humeral head (reverse Hills–Sachs).

Fig. 11.20 Neer classification system for proximal humeral fractures. The four major segments of the proximal humerus are: 1, greater tuberosity; 2, lesser tuberosity; 3, humeral head; and 4, humeral shaft. Segments are displaced if there is separation by more than 1 cm or angulation by more than 45°. Fractures that do not meet this criteria are considered one-part fractures. There are also two-part (single segment displaced), three-part (two segments displaced) and four-part (all segments displaced) fractures.

Fig. 11.20
Neer classification system for proximal humeral fractures. The four major segments of the proximal humerus are: 1, greater tuberosity; 2, lesser tuberosity; 3, humeral head; and 4, humeral shaft. Segments are displaced if there is separation by more than 1 cm or angulation by more than 45°. Fractures that do not meet this criteria are considered one-part fractures. There are also two-part (single segment displaced), three-part (two segments displaced) and four-part (all segments displaced) fractures.

Acromioclavicular dislocations (Fig. 11.21)

Acromioclavicular joint dislocations account for approximately 10% of all shoulder dislocations.

Fig. 11.21 Simplified classification of acromioclavicular joint injuries: type I (mild sprain of the acromioclavicular ligaments; the coracoclavicular ligaments are intact. Minimal disruption to the acromioclavicular joint alignment); type II (tear of the acromioclavicular ligaments with intact coracoclavicular ligaments; there is a small step or gap at the acromioclavicular joint); type III (tear of both the acromioclavicular and coracoclavicular ligaments; there is frank dislocation at the acromioclavicular joint).

Fig. 11.21
Simplified classification of acromioclavicular joint injuries: type I (mild sprain of the acromioclavicular ligaments; the coracoclavicular ligaments are intact. Minimal disruption to the acromioclavicular joint alignment); type II (tear of the acromioclavicular ligaments with intact coracoclavicular ligaments; there is a small step or gap at the acromioclavicular joint); type III (tear of both the acromioclavicular and coracoclavicular ligaments; there is frank dislocation at the acromioclavicular joint).

Traumatic rotator cuff injuries

Rotator cuff injuries occasionally occur from an acute traumatic episode. Plain radiographs are often normal. The diagnosis can be made with ultrasound or MRI, after treatment of the acute symptoms.

Imaging

Radiographs

Protocol

AP and axillary or scapular Y-views.

Findings

  • • AP view: Check glenohumeral and acromioclavicular alignment, and for glenoid fractures.

  • • Up to 50% of posterior dislocations are unrecognized on initial presentation. Findings can be subtle on the AP view (lightbulb sign; Fig. 11.22) and are better confirmed on the second view.

  • • Check for glenohumeral dislocation in the second view.

Fig. 11.22 Lightbulb sign. The humeral head on the AP view is often internally rotated in posterior glenohumeral dislocation, appearing more rounded like a ‘lightbulb’.

Fig. 11.22
Lightbulb sign. The humeral head on the AP view is often internally rotated in posterior glenohumeral dislocation, appearing more rounded like a ‘lightbulb’.

CT

CT can better define intra-articular involvement. It can be useful after reduction of glenohumeral dislocations to assess for associated bone defects (Hills–Sachs, bony Bankart lesions).

MRI

MRI (with intra-articular contrast medium) is the test of choice for assessing associated glenoid labrum injuries.

Protocol (one of many available)

  • • Dilute gadolinium is injected into the glenohumeral joint

  • • T1 FS; axial, coronal and sagittal planes. T2 FS (or STIR); coronal plane. T1; axial plane.

Findings

  • • Labral or tendon tears are usually linear high signal on T1 (post Gd) or T2 images.

  • • Bony deformities are usually best seen on the axial images.

Differential diagnosis

  • • Soft tissue injuries

Complications

  • • Delayed union/non-union (after fracture)

  • • Recurrent dislocations (after dislocation)

  • • Avascular necrosis

  • • Neurovascular injury (brachial plexus, axillary artery)

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders, USA.
    Find This Resource

  2. 2.

    Resnick R and Kransdorf MJ (eds) (2005) Bone and Joint Imaging. Elsevier, Philadelphia, PA.
    Find This Resource

Musculoskeletal Hip fractures and dislocations

Aetiology and epidemiology

Hip fractures can occur with minimal trauma in elderly osteoporotic individuals or with major injury in young adults.

Clinical features

Localized pain and swelling at the hip.

Inability to move the hip.

Externally rotated and shortened leg.

Classification

Proximal femoral fractures (Fig. 11.23)

Intracapsular fractures are approximately twice as common as extracapsular fractures. AVN and non-union are complications associated with intracapsular fractures.

Isolated fractures of the greater or lesser trochanter can occur from avulsion injuries in children or young athletes.

Hip dislocations

Major trauma is the usual cause of hip dislocations. They can be classified as anterior, posterior (most common) or central, and they can occur with reciprocal acetabular fractures. Posterior dislocations are associated with a flexed knee striking the dashboard during a RTA (‘dashboard injury’).

Fig. 11.23 Fractures of the proximal femur can be classified anatomically as: 1, subcapital; 2, transcervical; 3, basicervical; 4, intertrochanteric; and 5, subtrochanteric. Fractures 1, 2 and 3 are intracapsular, fractures 4 and 5 are extracapsular.

Fig. 11.23
Fractures of the proximal femur can be classified anatomically as: 1, subcapital; 2, transcervical; 3, basicervical; 4, intertrochanteric; and 5, subtrochanteric. Fractures 1, 2 and 3 are intracapsular, fractures 4 and 5 are extracapsular.

Imaging

Radiographs

Protocol

AP pelvis and lateral view of the symptomatic hip.

Findings

  • • Some proximal femoral fractures may only be detected as a sclerotic line. Check for associated acetabular and pubic ramus fractures. MRI should be considered if the patient remains symptomatic with normal radiographs.

CT

CT can better define intra-articular involvement, and is useful after reduction of hip dislocations to assess subtle fracture patterns, particularly involving the acetabulum.

MRI

MRI is preferred over CT for detecting a radiographically occult proximal femoral fracture.

Protocol (one of many available)

  • • T1; T2 FS (or STIR); large field of view (include both hips); axial and coronal planes.

  • • Use a small field of view (e.g. one hip) if detailed assessment of a region is required.

Findings

  • • Fractures are low signal on T1 and T2. There is often surrounding marrow oedema (low signal on T1; high signal on T2).

Differential diagnosis

  • • Pelvic fractures.

Complications

  • • Delayed union/non-union (after fracture)

  • • Avascular necrosis

  • • Neurovascular injury (sciatic nerve with posterior dislocations)

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders, USA.
    Find This Resource

  2. 2.

    Resnick R and Kransdorf MJ (eds) (2005) Bone and Joint Imaging. Elsevier, Philadelphia, PA.
    Find This Resource

Musculoskeletal Wrist fractures and dislocations

Aetiology and epidemiology

Injuries of the upper limb most commonly involve the wrist. Fractures of the distal radius and ulna are approximately 10 times more frequent than carpal fractures.

Clinical features

Usually fall onto an outstretched hand. Localized pain and swelling. Tenderness in the anatomical snuffbox if there is a scaphoid fracture.

Classification

Distal radial and ulnar fractures

Table 11.1 provides a simplified description of the main fracture types. It is important to describe the number of fracture fragments, the amount of displacement or angulation, and the absence or presence of intra-articular involvement.

Table 11.1 Fractures of the distal radius and ulna

Fracture

Characteristics

Colles’

Dorsal displacement of the distal fragment

Smith’s

Volar displacement of the distal fragment

Barton’s

Fracture extending from the dorsal margin of the radius to the radial articular surface

Greenstick

Fracture that involves only one cortex; occurs in children

Torus

Fracture that produces buckling of both cortices; occurs in children

Carpal fractures

Scaphoid fractures account for about 65% of carpal fractures and may not be demonstrated on initial radiographs. Most scaphoid fractures occur in the waist (∼70%) or proximal pole (∼20%) and fractures at these locations potentially compromise the blood flow to the proximal portion (most of the blood supply to the scaphoid enters distally). Proximal fractures have a higher rate of avascular necrosis and non-union. Scaphoid fractures are associated with other fracture–dislocations of the wrist.

Isolated fractures of the other carpal bones are less common. Triquetral fractures typically involve the dorsal aspect and are best seen on lateral radiographs (Fig. 11.24). Hamate fractures may involve any portion of the bone, but fractures involving the hamate hook can be difficult to identify on radiographs.

Fig. 11.24 AP and lateral wrist radiograph. Triquetral chip fracture. There is a small bone fragment (arrow) dorsal to the carpal bones.

Fig. 11.24
AP and lateral wrist radiograph. Triquetral chip fracture. There is a small bone fragment (arrow) dorsal to the carpal bones.

Dislocation of the distal radio-ulnar joint

This can occur with a fracture of the radial shaft (Galeazzi fracture–dislocation; this is an example of looking actively for a second fracture when a fracture involves a bone ring, cf. pelvic fractures, Musculoskeletal p. [link]) or with a Colles’ fracture. The ulna usually dislocates dorsally.

Carpal instability

Lunate and perilunate dislocations are uncommon injuries.

  • • Lunate dislocation: the lunate dislocates volarly;

  • • Perilunate dislocation: the lunate remains in alignment with the radius while the other carpal bones dislocate dorsally. Perilunate dislocations are often associated with scaphoid fractures.

  • • Midcarpal dislocations: this represents a combination of the previous two injuries with partial volar tilt of the lunate and partial dorsal dislocation of the other carpal bones (Fig. 11.25).

Fig. 11.25 Carpal dislocations. Classification is easiest on the lateral view.

Fig. 11.25
Carpal dislocations. Classification is easiest on the lateral view.

Scapholunate dissociation is relatively common and is suggested when there is widening between the scaphoid and lunate by more than 2mm (Terry Thomas or Madonna sign).

Imaging

Radiographs

Protocol

PA and lateral views. Obtain a scaphoid series (PA, lateral, 45° pronation PA, and ulnar deviation PA) if a scaphoid fracture is suspected.

Findings

  • • PA view: Check for distal radioulnar dislocation, scapholunate widening.

  • • Lateral view: Check for triquetral fractures, carpal dislocations and that the radial articular surface has its normal palmar tilt.

  • • If a scaphoid fracture is suspected and the scaphoid series appears normal, the patient must be re-imaged. The options include:

    • • A repeat scaphoid series in 10–14 days.

    • • Bone scintigraphy after 3 days.

    • • CT/MRI.

    • • MRI is believed to be most sensitive for radiographically occult scaphoid fractures, but the choice often depends on local factors such as cost and availability.

CT

CT can better define fracture comminution, depression and intra-articular involvement, particularly with the small, complex carpal bones. It can identify occult carpal fractures such as a hook of hamate fracture.

MRI

MRI is used to evaluate soft-tissue injuries, such as to the triangular fibrocartilage, or to exclude occult carpal fractures.

Protocol (one of many available)

If a fracture is suspected then the following protocol can be used: T1; T2 FS (or STIR); coronal plane (additional planes are optional).

Findings

  • • Fractures are low signal on T1 and T2. There is often surrounding marrow oedema (low signal on T1; high signal on T2).

Bone scintigraphy

Bone scintigraphy can be used to detect radiographically occult fractures such as to the scaphoid. However, there is an increasing preference to use CT or MRI in this situation.

Differential diagnosis

  • • Soft tissue injury.

Complications

  • • Delayed union/non-union (after fracture)

  • • Avascular necrosis

  • • Post-traumatic secondary osteoarthritis

  • • Neurovascular injury (median and ulnar nerves)

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders, USA.
    Find This Resource

  2. 2.

    Resnick R and Kransdorf MJ (eds) (2005) Bone and Joint Imaging. Elsevier, Philadelphia, PA.
    Find This Resource

Musculoskeletal Ankle fractures and dislocations

Aetiology and epidemiology

Approximately 15% of ankle injuries result in a fracture.

Clinical features

  • • Localized pain and swelling at the ankle.

  • • Inability to weight-bear.

Classification of fractures

Ankle fractures can be described as unimalleolar, bimalleolar or trimalleolar (involvement of the posterior lip of the tibial plafond). Orthopaedic surgeons make use of the Denis–Weber classification (Fig. 11.26), which is based on the level of the fibular fracture in relation to the syndesmosis.

Fig. 11.26 Denis–Weber classification.

Fig. 11.26
Denis–Weber classification.

Weber A: Fibular fracture (often transverse) below the syndesmosis. These fractures are usually stable and treated with closed reduction and casting unless accompanied by a displaced fracture of the medial malleolus.

Weber B: Fibular fracture (often spiral) at the level of the syndesmosis. Associated injury to the deltoid ligament–medial malleolus complex may be present. These fractures may be stable or unstable depending on the extent of the injury.

Weber C: Fibular fracture above the syndemosis usually associated with injuries to the deltoid ligament–medial malleolus complex and the anterior tibiofibular ligament complex. There may also be injury to the posterior tibiofibular complex.

  • • Type C1: the interosseous membrane is intact and the fracture is low.

  • • Type C2: the interosseous membrane is ruptured at the fracture site

  • • and the fracture is higher on the fibula.

  • • Type C3: the interosseous membrane is ruptured above the fracture.

The fracture site can be at the proximal fibula (Maisonneuve fracture).

Weber C fractures are usually unstable and often require open reduction and internal fixation.

In general, medial malleolar fractures that are displaced and spiral fibular fractures that are above the syndesmosis are considered unstable.

Other ankle fractures

Pilon fracture

This is a comminuted fracture involving the distal tibial articular surface (Fig. 11.27). It results from an axial loading injury. Associated fractures often coexist, e.g. involving the malleoli.

Triplane fracture

This usually occurs in adolescents. Fractures are seen in three different axes (planes): a vertical (sagittal) fracture through the distal tibial epiphysis, a horizontal fracture through the distal tibial physis, and an oblique (coronal) fracture posteriorly through the distal tibial metaphysis (Fig. 11.28).

Fig. 11.28 Triplane fracture (two-part).

Fig. 11.28
Triplane fracture (two-part).

Juvenile Tillaux fracture

This usually occurs in adolescents. It is a vertical fracture of the distal tibial epiphysis with lateral extension of the fracture through the open physis and represents a Salter–Harris type 3 fracture (Fig. 11.29).

Imaging

The Ottawa ankle rules provide practical guidelines in selecting patients for ankle radiographs. This consists of pain in the malleolar area with any one of:

  • • Bone tenderness along the distal 6cm of the posterior edge of the tibia or fibula.

  • • Bone tenderness at the tip of the medial or lateral malleolus.

  • • Inability to weight-bear both immediately and for four steps.

  • • There are additional rules for suspected foot injuries.

Radiographs

Protocol

AP and lateral views are commonly obtained. Some centres make use of the AP mortice view as this can provide better evaluation of the space around the talar dome. The AP mortice view is obtained with the foot internally rotated 20° so that the fibula does not overlap the talus. The lateral view should include the entire calcaneum and ideally include the base of the fifth metatarsal.

Findings

  • • Fractures are usually obvious. Pay particular attention to the talar dome for osteochondral injuries.

CT

CT can better define injuries with complex fracture patterns, such as triplane or pilon fractures.

MRI

MRI can be used to assess occult fractures of the talar dome.

Differential diagnosis

  • • Ankle ligament sprains.

Complications

  • • Delayed union/non-union.

Ankle dislocations

Ankle dislocations of the tibiotalar joint are usually part of complex malleolar fractures and rarely occur in isolation. Standard radiographs are used to help make the diagnosis. Posterior dislocation of the talus is most common.

Urgent reduction is required.

Further reading

  1. 1.

    Raby N, Berman L and de Lacey G (2005) Accident and Emergency Radiology: A Survival Guide. Saunders, USA.
    Find This Resource

  2. 2.

    Resnick R and Kransdorf MJ (eds) (2005) Bone and Joint Imaging. Elsevier, Philadelphia, PA.
    Find This Resource

Musculoskeletal Musculoskeletal Sternal and rib fractures

Aetiology

These fractures usually occur from direct blunt trauma, e.g. impact between the sternum and car steering wheel in an RTA. Sternal fractures occur in approximately 5% of blunt chest trauma; rib fractures in 50%.

Clinical features

Localized pain after direct trauma. Fractures of the first and second ribs imply high-velocity trauma and are associated with injuries to the brachial plexus and subclavian vessels.

Imaging

Radiographs

Protocol

Sternal views (frontal and lateral).

Routine CXR (frontal and lateral) are usually sufficient for assessing rib fractures. Specific rib views rarely change management.

Findings

  • • The lateral view is most useful for detecting sternal fractures and demonstrating the degree of displacement.

  • • Most sternal fractures are transverse and occur in the body.

  • • Look for a flail chest (at least three ribs broken in two or more places).

CT

Protocol

  • • Chest CT may have been performed to assess for concomitant internal injury but is not indicated to detect rib fractures alone. Use multiplanar reconstructed images with bone settings to assess for skeletal trauma.

Findings

  • • Fractures are more accurately delineated than on plain film.

  • • Look for associated soft tissue or lung injuries.

  • • Anterior mediastinal haemorrhage is common with a sternal fracture.

  • • Assess for upper abdominal organ injuries with lower rib fractures.

Differential diagnosis and complications

  • • Cardiac contusion.

  • • Lung contusion, pneumothorax and flail chest.

  • • Nerve injuries (e.g. brachial plexus).

Management

  • • Conservative management in most cases.

  • • Early intubation may be required with a flail chest.

  • • Treat any associated injuries. Assess for cardiac trauma (e.g. elevated troponin levels) with significant displacement of a sternal fracture.

Further reading

  1. 1.

    Miller LA (2006) Chest wall, lung and pleural space trauma. Radiol Clin North Am 44; 213–24.
    Find This Resource

  2. 2.

    Bull S (2005) Skeletal Radiography: A concise introduction to projection radiography. Toolkit Publications, UK.
    Find This Resource

Musculoskeletal Septic arthritis

Definition and aetiology

Infection in a joint, usually bacterial.

Clinical features

The joint is usually hot and swollen and typically there is a monoarticular presentation. Pyogenic bacterial infection usually has an acute onset. Involvement with tuberculosis or fungal organisms is more indolent.

Blood tests (CRP, ESR) can be useful. However, joint fluid analysis is more definitive and should be obtained if there is a clinical suspicion of septic arthritis.

Imaging

Plain radiographs are the initial investigation. If there are typical radiographic findings, joint aspiration and culture should follow. If radiographs are normal, then consider MRI. US is useful to confirm a joint effusion and guide aspiration.

Radiographs

Protocol

Standard views for the joint in question which usually involve two orthogonal planes.

Findings

  • • Often normal, although peri-articular soft tissue swelling and joint space widening may be seen.

  • • (Late changes) Joint space narrowing and peri-articular erosions which progress to bone destruction. Articular changes occur more slowly in tuberculosis and fungal infection.

US

Protocol

  • • A high-frequency (7.5MHz or higher) linear-array transducer can be used to assess most joints, although a lower-frequency probe may be more suitable in obese patients.

Findings

  • • Septic effusions may be completely anechoic or septated/debris-filled.

  • • Imaging cannot distinguish between inflammatory and infected joint effusions.

  • • Ultrasound is useful to guide needle aspiration, particularly in paediatric hips.

MRI

Protocol

  • • T1; T1 FS+Gd; T2 FS (or STIR).

  • • Use at least 2 image planes (axial and coronal or sagittal).

Findings

  • • Look for joint effusions, synovial enhancement, marrow changes, cartilage erosion and soft tissue abscesses.

  • • Reactive bone marrow oedema is present in up to 50% of septic arthritis (in the absence of osteomyelitis).

  • • MRI is sensitive but not as specific as joint aspiration and the latter is still required to establish the diagnosis.

Differential diagnosis

  • • Non-septic arthritis.

  • • Internal derangement from trauma.

Management

  • • Early diagnosis is essential to prevent permanent joint damage.

  • • Intravenous antibiotics.

  • • Drainage of joint effusions.

Complications

  • • Osteomyelitis

  • • Joint subluxation and dislocation

  • • Fibrous or bony ankylosis

  • • Secondary osteoarthritis

Paediatric hip pain

Acute hip pain is a common cause of presentation by children to the emergency department. The vast majority of these cases are due to transient synovitis, a self-limiting condition. However, clinical differentiation from more serious conditions such as Perthe’s, slipped capital femoral epiphysis or septic arthritis can be difficult. Initial assessment often involves a plain radiograph but findings can be subtle with septic arthritis.

Many centres make use of hip ultrasound to assess for joint effusions. If a joint effusion is present, aspiration is performed under ultrasound guidance and fluid analysis is used to exclude septic arthritis.

Further reading

  1. 1.

    Aurea V, Mohana-Borges R, Chung CB et al. (2004) Monoarticular arthritis. Radiol Clin North Am 42; 135–49.
    Find This Resource

  2. 2.

    Berquist T (ed.) (2006) MRI of the Musculoskeletal System. Lippincott Williams and WIlkins, Philadelphia, PA.
    Find This Resource

Musculoskeletal Musculoskeletal Achilles tendon rupture

Definition

Complete tear of the Achilles tendon; retraction may be present.

Aetiology and epidemiology

The Achilles tendon is the most commonly injured ankle tendon. Rupture typically occurs in the fourth to fifth decades and with athletic activity (‘weekend warriors’). M:F = 5:1. The usual location is 2–6cm above the calcaneal insertion, a region of relative avascularity. Tears at the musculotendinous junction are less common but occur with younger people.

Clinical features

Sudden pain at the back of the ankle during activity. Unable to stand on tiptoes. A tendon gap may be palpable.

Up to 25% of Achilles tendon ruptures can be missed clinically at initial presentation.

The main clinical question is to differentiate complete tears from partial thickness tears or tendinosis (degenerative tendinopathy).

Imaging

Imaging is helpful when the clinical examination is equivocal or there is a delay in presentation. In particular, imaging is used to differentiate between full- and partial-thickness tears. Ultrasound is the first-line test.

Radiographs

Protocol

Standard AP and lateral views for trauma.

Findings

  • • Loss of the pre-Achilles fat pad.

  • • Useful to exclude avulsion injuries or other fractures.

US

Protocol

Lie patient in the prone position with the feet hanging over the end of the examination couch. Use a high-frequency (7.5MHz or higher) linear-array transducer with liberal application of US gel over the Achilles tendon. Scan in both longitudinal and transverse planes.

Findings

  • • Full-thickness interruption of the tendon. The space may be filled with fluid or haemorrhage. Look for posterior acoustic shadowing which indicate ruptured tendon ends.

  • • Measurement of the tendon gap with the foot in plantar flexion is useful to help decide between surgical or conservative treatment.

  • • Partial-thickness tears and tendinosis demonstrate increased AP tendon diameter. Look for focal defects. At least some intact tendon fibres should be present in partial thickness tears (Fig. 11.30).

  • • Dynamic tendon movement helps to differentiate full-thickness from severe partial-thickness tears.

Fig. 11.30 Longitudinal US image. Partial-thickness tear of the Achilles tendon. There is fusiform tendon swelling with a focal defect (arrow) anteriorly; intact posterior tendon fibres are present.

Fig. 11.30
Longitudinal US image. Partial-thickness tear of the Achilles tendon. There is fusiform tendon swelling with a focal defect (arrow) anteriorly; intact posterior tendon fibres are present.

MRI

Protocol

  • • Sagittal and axial STIR or PD FS; T1 (any plane).

Findings

  • • Separated tendon ends indicate complete rupture. There is high signal intensity on the fluid sensitive sequences in the tendon gap with acute injuries (Fig. 11.31).

  • • Partial-thickness tears and tendinosis demonstrate tendon thickening with heterogeneous signal intensity.

Fig. 11.31 Sagittal STIR MR image. Rupture of the Achilles tendon. There is complete disruption and retraction of the torn edges of the Achilles tendon with a fluid-filled gap (arrowed).

Fig. 11.31
Sagittal STIR MR image. Rupture of the Achilles tendon. There is complete disruption and retraction of the torn edges of the Achilles tendon with a fluid-filled gap (arrowed).

Differential diagnosis

  • • Partial-thickness tear of the Achilles tendon.

  • • Tear of the plantaris tendon.

Management

  • • Conservative (leg placed in an equinus cast) or surgical management is based upon the extent of the tear and amount of tendon retraction.

Complications

  • • Achilles tendon re-rupture.

Further reading

  1. 1.

    Hartergink P, Fessell DP, Jacobson JA et al. (2001) Full-versus partial-thickness Achilles tendon tears: sonographic accuracy and characterization in 26 cases with surgical correlation. Radiology 220; 406–12.
    Find This Resource

  2. 2.

    Rosenberg ZS, Breltran J and Bencardino JT (2000) From the RSNA refresher courses. Radiological Society of North America. MR imaging of the ankle and foot. Radiographics 20(Spec no); S153–79.
    Find This Resource

  3. 3.

    McNally EG (2004) Practical Musculoskeletal Ultrasound. Churchill Livingstone, Edinburgh.
    Find This Resource

Musculoskeletal Musculoskeletal Intramuscular haematomas

Definition

Muscle contusion secondary to blunt direct trauma.

Aetiology and epidemiology

Acute muscle injury is common and accounts for over one-third of all acute sports-related injuries. Direct trauma usually occurs in contact sports and muscles of the lower limb are most often involved.

Clinical features

Direct trauma to the muscle group with subsequent pain and swelling. There is still residual function unlike a muscle rupture.

Imaging

The diagnosis is usually made clinically and imaging tends to be reserved for when the diagnosis is in doubt, when the symptoms are not responding to therapy, or if the patient is a professional athlete. US is the first-line investigation. MRI is an alternative.

The appearance of haemorrhage varies with both US and MRI according to its age. Haematoma may predominate within the muscle or lie outside the epimysial covering between muscles. Intramuscular fluid–fluid levels (a layering effect with cellular components of the blood settling dependently and the less dense plasma forming a layer on top) may be seen.

Radiographs

Protocol

Standard views as for trauma.

Findings

  • • Useful to exclude a fracture.

  • • Myositis ossificans may be present, usually 6 weeks after the injury.

US

Protocol

A high-frequency (7.5MHz or higher) linear-array transducer can be used to assess most muscles, although a lower-frequency probe may be more suitable in obese or very muscular patients.

Findings

  • • Acute haematomas (0–4hrs) are echogenic with ill-defined margins and extensive surrounding echogenic swelling of the muscle. Dynamic imaging can help exclude a complete tear.

  • • After a few days, the haematoma becomes predominantly hypoechoic with a better defined echogenic margin (Fig. 11.32). Over the next few weeks, the echogenic periphery gradually fills in towards the centre. The majority of muscle haematomas from sporting injuries heal with normal muscle regeneration.

Fig. 11.32 Longitudinal US image. Rectus sheath haematoma (arrows) which is predominantly hypoechoic with echogenic areas.

Fig. 11.32
Longitudinal US image. Rectus sheath haematoma (arrows) which is predominantly hypoechoic with echogenic areas.

MRI

Protocol

Fluid sensitive sequences (T2 FS, STIR) demonstrate oedema well. T1-weighted sequences provide information about subacute haemorrhage and muscle atrophy/fatty infiltration. Use at least two image planes (axial and coronal or sagittal).

Findings

  • • Acute haematomas (0–48hrs) are often isointense to skeletal muscle on T1-weighted images and hypointense on fluid sensitive sequences. Adjacent oedema (low signal on T1; high signal on T2) can be a prominent feature.

  • • Subacute haematomas (weeks to months old) usually demonstrate increased signal intensity on both T1- and T2-weighted images due to the presence of extracellular methaemoglobin. As the lesion ages, the wall of the haematoma may become hypointense from haemosiderin deposition and fibrosis.

Differentiation between a simple haematoma and a haemorrhagic neoplasm can be difficult with imaging. Administration of contrast medium can help to exclude a neoplasm when the lesion in question shows no enhancement, but usually, correlation with the clinical history is most useful in this context.

Rectus sheath haematomas deserve a special mention. They are uncommon but are often an unsuspected cause of abdominal pain. Ultrasound is again the first-line test. The Valsalva manoeuvre and visualization of a defect in the deep fascia help differentiate from an abdominal wall hernia. Forced expiration against a closed airway increases intra-abdominal pressure and improves detection of abnormal movement of intra-abdominal contents through a deep fascial defect.

Further reading

  1. 1.

    McNally EG (2004) Practical Musculoskeletal Ultrasound. Churchill Livingstone, Edinburgh.
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  2. 2.

    Boutin RD, Fritz RC and Steinbach LS (2002) Imaging of sports-related muscle injuries. Radiol Clin N Am 40; 333–62.
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Musculoskeletal Musculoskeletal Retained foreign body

Definition and aetiology

A foreign body retained in the soft tissues is a common scenario in the emergency department, usually involving metal, glass or wood.

Clinical features

Occurs with penetrating injuries. Patient complains of a stinging sensation deep to a puncture wound. Up to 40% of retained foreign bodies in the soft tissues are overlooked at initial examination. Detection and removal is important to avoid infectious or inflammatory complications.

Imaging

  • • Plain radiographs are often the first imaging modality used and are good at detecting metal or glass. They can fail to detect non-radio-opaque foreign bodies such as wood or plastic. Radiographs can also be of limited use for precise localization of foreign bodies situated deep in the tissues.

  • • Ultrasound is used for detecting non-radio-opaque foreign bodies and accurately localizing all types of soft tissue foreign bodies. A mark can be placed on the skin overlying the foreign body to aid removal with ultrasound guidance or by surgical means.

Radiographs

Protocol

Use a soft tissue exposure with at least two projections. The soft tissue should be imaged without overlying bone where possible. Place a skin marker at the site of the puncture wound.

Findings

  • • Radio-opacity in the soft tissues.

  • • Note that all glass is radio-opaque to some degree on radiographs.

US

Protocol

Use a high-frequency (7.5MHz or higher) linear-array transducer with liberal application of US gel. Place the probe gently on the skin.

Findings

  • • Foreign bodies are often echogenic with posterior acoustic shadowing (Fig. 11.33). There may be a surrounding hypoechoic rim of granulation tissue, oedema or haemorrhage.

  • • Look for associated soft-tissue complications, e.g. soft-tissue abscesses, tendon or neurovascular injuries.

Fig. 11.33 Ultrasound of a small thorn in the soft tissues of the right index finger. There is an echogenic foreign body (between cursors) with a surrounding hypoechoic region.

Fig. 11.33
Ultrasound of a small thorn in the soft tissues of the right index finger. There is an echogenic foreign body (between cursors) with a surrounding hypoechoic region.

CT or MRI

In exceptionally difficult cases, CT or MRI should be considered. Add a gradient echo sequence to emphasize susceptibility artefacts when looking for metallic foreign bodies with MRI.

Further reading

  1. 1.

    Horton LK, Jacobson JA, Powell A et al. Sonography and radiology of soft-tissue foreign bodies. Am J Roentgenol 2001; 176; 1155–9.
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  2. 2.

    Boyse TD, Fessell DP, Jacobson JA et al. US of soft-tissue foreign bodies and associated complications with surgical correlation. Radiographics 2001; 21; 1251–6.
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  3. 3.

    McNally EG (2004) Practical Musculoskeletal Ultrasound. Churchill Livingstone, Edinburgh.
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