A 30-years old neurologist felt walking down the stairs, landing on buttocks. During the physical examination, the emergency department physician noticed mild perianal hypoesthesia.
CT and MRI were obtained for diagnosis. Sagittal bone window CT of the pelvis (figure 1) demonstrates a transverse fracture through the S4 vertebral body and posterior elements (white arrow), with a mild retrolisthesis of the upper fragment.
MR sagittal T1W and T2W (figures 2a and 2c), and oblique coronal T1W and T2W (figure 2b and 2d) Dixon images of the pelvis show cancellous bone marrow oedema (white asterisk) associated with the fracture previously described (white arrows). Discrete sacral canal stenosis is noticed.
Transverse sacral fractures [TSF} are uncommon. They constitute up to 5% of sacral fractures, and they usually occur in young adults. A fall landing on the buttocks causes 35% of them, with 37% caused by motor vehicle accidents.
TSF can be categorized in high and low fractures, with both having a horizontal plane separation and two sacral fragments. The Denis classification of sacral fractures includes them in the zone III fractures. Nevertheless, many transverse sacral fractures affect the three zones described. They were later classified into four categories by Camille et al., but only including transverse high sacral fractures. They can be associated with thoracolumbar burst fractures.
High transverse sacral fractures are more common than low transverse sacral fractures. They are usually secondary to a high-energy traumatic event due to Indirect forces coming from the pelvis and lumbar spine and fixed to the sacrum.
Low transverse sacral fractures are mainly due to a direct impact against the coccyx or a direct hit to the lower sacral segments. The mechanism involved is a levering action through the distal sacrum, below the sacroiliac joints' level of fixation. Any of the three last sacral vertebrae may be affected. They are usually stable fractures.
A sacral fracture should always be suspected after trauma with resulting sacrococcygeal pain or a pelvic ring fracture with neurological deficits.
TSF is more often associated with neurological deficits than vertical fractures. The most commonly described neurological deficits are bowel-bladder dysfunction and saddle anaesthesia. A sacral root injury could produce sexual impairment [1].
In general, sacral fractures may be hard to identify on conventional radiology due to the overlying bowel gas, the bladder silhouette, and the normal angulation of the sacrum. TSF fractures are best seen in a lateral sacrum view, although an anteroposterior radiograph could show a step ladder by displacement and overriding of the sacral fragments.
CT and MRI have a higher sensitivity for transverse sacral fractures than conventional radiology. Besides the sacral horizontal fracture, cancellous bone marrow oedema, and paravertebral soft tissue oedema may be seen [2]. It is essential to describe if there is any displacement of the sacral fragments and sacral canal stenosis.
Management and treatment will depend on the patient's neurological status and the stability of the fracture. A fracture displacement of 1 cm or more is considered to be unstable. Low transverse sacral fractures usually don't need to be stabilized [1].
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Transversal low sacral fracture
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1. From the provided CT axial and sagittal images, a horizontally oriented fracture line can be seen in the distal sacrum, near the S3-S4 level (indicated by the arrows), with slight separation of the fracture surfaces. The surrounding soft tissue density appears normal or only mildly altered, and local soft tissue swelling is observed.
2. MRI sagittal and axial sequences show a clear horizontal fracture line in the lower sacrum, consistent with the CT findings, and a small amount of bone marrow edema signal (hyperintense on T2WI). The local dural sac and nerve roots do not show significant displacement or extensive compression, but there may be some degree of nerve root irritation or traction.
3. In combination with the clinical presentation, the patient has mild perineal sensory loss (“saddle anesthesia”). There is currently no evidence of major displacement of the fracture fragments or instability of the pelvic ring on imaging.
1. Low Transverse Sacral Fracture
Cause: Often caused by direct impact to the buttocks or falling from a height, typically involving the sacral segments below S3. Imaging shows a horizontal fracture line, usually relatively stable, mostly affecting the sacral endplate, with minimal adjacent soft tissue edema.
Features: Consistent with the clinical symptoms (e.g., mild saddle anesthesia). The fracture line is located at a lower sacral level, matching literature descriptions of low transverse fractures.
2. Sacro-coccygeal Joint Dislocation or Coccygeal Fracture
Cause: Related to buttock impact or direct trauma to the coccyx, commonly seen when falling and landing on the buttocks.
Features: If it involves a coccygeal fracture, a more distal fracture line may be visible on X-ray or MRI. In cases of joint dislocation, misalignment of the sacro-coccygeal joint surfaces is often observed. While it can cause local pain, perineal sensory loss is relatively less common.
3. Mid- to High-level Transverse Sacral Fracture
Cause: Usually caused by high-energy trauma, potentially involving large fracture fragments and affecting the lumbosacral nerve roots.
Features: In the present case, the fracture is nearer S3-S4 and does not show marked displacement, thus it does not strongly fit the typical presentation of a higher-level transverse sacral fracture. However, consideration should be given to the possibility of multiple fractures.
Considering the patient’s age, mechanism of injury (fall landing on the buttocks), imaging findings (horizontal fracture line at the lower sacrum, minimal displacement, mild marrow edema), and mild perineal sensory deficit, the most likely diagnosis in this case is: Low Transverse Sacral Fracture.
No significant ligamentous or extensive pelvic ring instability is indicated by the current imaging, and no additional higher-level spinal injuries are evident. If more pronounced neurological symptoms develop or if there is suspicion of more complex fractures, further 3D reconstruction or additional evaluation of the lumbosacral region may be warranted.
1. Treatment Strategy
(1) Conservative Treatment: For low-energy injuries with stable fractures and minimal displacement (<1 cm), conservative management can be employed, including symptomatic relief of pain (e.g., oral NSAIDs or short-term mild opioid analgesics) and use of cushions to reduce direct pressure on the fracture site.
(2) Surgical Management: In cases with significant displacement (≥1 cm) or severe neurological impairment (e.g., worsening bowel or bladder dysfunction, notable peripheral nerve deficits), surgical reduction and internal fixation may be considered to alleviate nerve compression and stabilize the fracture segment.
(3) Neurological Symptom Management: If perineal numbness or signs of saddle anesthesia worsen, urgent evaluation is recommended to check for severe cauda equina or nerve root compression. In some cases, nerve root decompression or close monitoring of neurological function recovery may be required under professional guidance.
2. Rehabilitation and Exercise Prescription
Utilize the FITT-VP principle (Frequency, Intensity, Time, Type, Progression, Volume) to create an individualized rehabilitation program:
(1) Acute Phase (Week 1–2):
This report provides a reference analysis, intended for general medical information and rehabilitation advice. It does not replace an in-person consultation or the professional diagnosis and treatment recommendations of a healthcare provider. Patients should follow their own specific conditions and consult with a physician for appropriate treatment and rehabilitation. If you have further questions, please contact a qualified orthopedic or rehabilitation specialist.
Transversal low sacral fracture
