TRANSVERSAL FRACTURE OF THE SACRUM: PLACE OF IMAGING

 

A ACHOUR, S JERBI OMEZZINE,

Z KHADIMALLAH, M SAIDI, Z CHAEIB1,

N SASSI1, HA HAMZA.

 Department of Medical Imaging, University Hospital Tahar Sfar, Mahdia,

Tunisia 1Department of Orthopaedics, University Hospital Tahar Sfar, Mahdia,

Tunisia

 

MK2

Introduction

-Transverse sacral fractures (TSFs) are an uncommon type of

sacral fractures.

-They are classified as zone III sacral fractures.

-Sacral fractures are injuries that frequently are overlooked.

-They present diagnostic and therapeutic dilemmas to the

clinicians who evaluate trauma patients.

-Between 40% and 50% of sacral fractures have a concomitant

pelvic fracture.

-Usually associated with neurologic impairment and injuries of

the pelvic ring

-Most commonly, sacral fractures are longitudinal.

-Transverse fractures of the sacrum are frequently difficult to

appreciate on conventional radiographs.

-Knowledge of the range of radiological appearances of sacral

fractures and when to use the appropriate imaging techniques

will enable the radiologist to properly assess the sacrum.

Objectif

Reports on sacral fractures, particularly transverse fractures,

appear infrequently in the literature in comparison to those on

other fractures of the pelvis. This may be due in part to failure to

recognize them due to low suspicion of a fracture or difficult

radiological examination .

Reported is the case of a patient who sustained a transverse sacral

fracture with subsequent neurologic complications.

Materials and methods

-A 20 year-old woman slipped and fell directly onto her low

back.

-She presented later that day with complaints of nonradiating

low back pain made worse with ambulation and weight bearing.

She had urinary hesitancy and could void only small amounts of

urine at a time.

-She denied hematuria, dysuria, or any urinary or fecal

incontinence. --She sustained no other trauma in the fall.

- On examination the patient was in moderate pain.

- The sacrococcygeal area was tender to palpation. Rectal

examination was normal with good sphincter tone.

-She demonstrated good muscle strength of the lower

extremities and her sensation was intapt.

-Both patellar and ankle reflexes were intact bilaterally.

-The patient's pain worsened with walking.

Results

-The initial radiographs of the lumbosacral and coccygeal

areas were read as a fracture through the junction of the mid

and distal thirds of the sacrum with slight anterior

displacement of the distal fragment.

-Tomograms confirmed a fracture through the S 4 level with

minimal displacement and angulation.

Discussion

Epidemiology:

-TSF are rare.

-They constitute less than 1% of all spinal fractures and only 3%

to 5% of all sacral fractures .

-TSF are most common among young people between the

second and third life decade, and are slightly more frequent in

males.

-There are diverse types of accidents causing TSF, almost 37%

are caused by motor vehicle accidents (MVA); 35% are caused

by a fall usually landing on buttocks.

Classification:

* Zone I fractures involve the alar region.

*Zone II fractures occur in the sacral foraminal area.

*Zone III fractures occur in the vicinity of the central canal.

-Because of the location of zone III fractures, they have a

high incidence of neurological deficits.

-Transverse sacral fractures (TSFs) have been traditionally

included as a type of zone III fractures

Diagnosis

Because of the low incidence and the radiological difficulties to

visualize the fracture, the diagnosis of TSF is often delayed.

Clinical diagnosis:

-The saddle anesthesia, loss of bladder function, and rectal tone

presented in patients with sacral fractures may be masked orr

unrecognized during the acute phase of trauma.

-Sacral injury should be suspected in any patient reporting

sacrococcigeal pain .

-Lacerations, bruising, tenderness, swelling, and crepitus over sacral

area are signs of potential injury .

-Patients with a suspected sacral fracture must have assessment of the

lower sacral roots.

-Rectal examination is very important in these patients; diminished

anal sphincter tone may be present even without bowel or bladder

symptoms.

-The neurological deficit secondary to TSF most commonly

described in the literature are BBD and saddle anesthesia.

-The most common neurological deficit was BBD characterized by

incontinence, retention, or flaccid sphincters. Another common

presentation was nerve root disturbance, usually L5 or S1 roots.

Radiological diagnosis

-Conventional radiography of the sacrum is often difficult to

interpret as overlying bowel gas, bladder, and the normal angulation

of the sacrum make the diagnosis of injury problematic.

-The fracture does not project well on the anteroposterior view

because of the sacral orientation.

-Pelvic inlet and outlet views are recommended as additional studies

to improve visualization of the sacrum in any patient with a

suspected sacral fracture.

-Certain findings intimate the presence of sacral fractures and

suggests the need for more extensive investigation: 1)fracture of a

lower lumbar transverse process; 2) pelvic ring fractures known to

be associated with a sacral fracture (eg, bilateral rami fractures); 3)

discontinuity or asymmetry in the ‘‘sacral notch’’; 4) irregularity of

the arcuate lines in the upper three sacral foramina.

-Although TSF are seen best in lateral radiographs, anteroposterior

radiographs can show the step ladder sign caused by displacement

and overriding of the fracture fragments, this finding is very

suggestive of TSF.

CT SCAN

-Computed tomography is the preferred modality for diagnosing

suspected or known posterior injury of the pelvic ring.

-Computed tomography with 1- to 2-mm cuts as well as sagittal

and coronal reformatted views offers superior visualization of the

fractured sacrum.

MRI

-Because the termination of the thecal sac at the S1–S2 interspace,

myelography is of limited usefulness. Sacral magnetic resonance imaging

may be useful for patients presenting with posttraumatic sacral neurological

deficits which are not explained by conventional radiological test findings;

however, it has little usefulness to define a fracture in an acutely

traumatized patient.

-With MR imaging, the sacral plexus and surrounding structunes

can be studied in detail .

-Mubtiplanar examination aids in the assessment of the effect of diseases on

the sacral plexus. The anatomic axial and oblique coronal planes display the

relevant structures somewhat more distinctly than the sagittal plane does.

-Obtaining axial and oblique coronal images, with T1weighting in

one plane and T2 weighting in the other, appears to be a reasonable

approach to MR imaging of the sacral plexus.

-If necessary, supplemental sagittal images on additional pulse

sequences can be added.

Treatment

-Different types of treatments for TSF have been reported.

-These treatments include : -conservative management

-initial conservative management followed by surgical treatment

-surgical treatment

Conclusion

-TSF are a special type of sacral fractures which can be difficult to diagnose initially.

-The U-shaped sacral fracture can be overlooked without appropriate imaging.

-Although it is difficult to discern on anteroposterior radiographs andaxial or coronal CT, the fracture is easily identifiable on CT images in the sagittal plane.

-We advocate reconstruction of CT images of the sacrum in the sagittal plane in trauma to prevent failure of identification.