Usually consider sacral fractures in
conjunction with pelvic fractures.
Unrecognized and inadequately treated
sacral fractures may lead to painful deformity and progressive loss of
Delayed surgery for posttraumatic
sacral deformity is complex, and the results are often less favourable than
after early surgery.
- Lumbosacral plexus (L4-S1)
- Sacral plexus (S2-S4)
- The anterior rami of S2-S5 contribute to sexual function as well as bowel
and bladder control by providing parasympathetic innervation to the bladder and
- The sympathetic ganglia of the inferior hypogastric plexus extend from
the anterolateral L5 and S1 vertebral bodies caudally to the anterior surface of
the sacrum along the medial margin of the anterior foramina of S2, S3, and S4.
- The posterior rami of the sacral roots consist of small sensory fibres, with
contributions to the cluneal nerves.
Several classification systems exist
- Tile, Denis et al., Roy-Camille et al., Strange-Vognsen, and Isler
Denis three-zone classification
Based on fracture anatomy
||Denis - 1988
Zone-I injuries are entirely
lateral to the neuroforamina
Zone-II injuries involve the neuroforamina but not the spinal canal
Zone-III injuries extend into the spinal canal with primary or associated
Zone I - Fractures occur lateral to
the sacral foramina. The most common, accounting for 50% of the fractures
in the series of Denis et al. Zone-I fractures mainly involve the sacral
ala, with possible extension into the sacroiliac joint. The fractures can be subdivided
into stable and unstable injuries, according to the three-stage severity system. Neurological injury occurs in approximately 6% of patients and
typically involves the L4 and L5 nerve roots.
Zone II - Vertical transforaminal
fracture without involvement of the sacral spinal canal. Second most common
pattern, accounting for 34% of the injuries in the study by Denis et al.
Neurological injury is found in 28% of patients, and most
frequently affects the L5, S1, or S2 nerve root. It is important to distinguish
between stable and unstable zone-II injuries because malunions in this area are
associated with very poor functional outcomes. Vertical shear injuries are
considered to be highly unstable zone-II fractures.
Any sacral fracture involving the spinal canal. Least frequently encountered
fracture pattern, only 16% of the patients in the study by Denis et al. Zone III
injuries are associated with the highest prevalence and severity of neurological
injury. Affecting 57% of the patients.
Two additional factors to consider are whether the injury is bilateral and the
axial level of the fracture. Patients with a transverse sacral fracture
involving the S1, S2, or S3 segment tend to have a higher prevalence of bladder
dysfunction than do those with a more caudal sacral fracture affecting the S4 or
S5 segment. Bilateral zone-I or II injuries are
extremely uncommon and, on closer inspection, are usually associated with an
unrecognized zone-III injury with an obscure transverse fracture line.
Subclassification of Denis
zone-III fractures as suggested by Roy-Camille et al. and modified by Strange-Vognsen
With this subclassification of injury severity,
the likelihood of neurological
injury, and therapeutic implications are directly related to increasing grade (1
Subclassification of Denis
zone-III fractures, Roy-Camille et al. - 1985
Type-1 Simple flexion deformity of the sacrum.
Type-2 Partial translation and hyperkyphotic.
Type-3 Complete translation with no
Modified Strange-Vognsen - 1991
Denis Zone 3 injury patterns
on image for larger image in new window
Isler - Injury at the Lumbosacral
||Lumbosacral junction - Isler 1990
Type A -
Lateral to L5-S1 facet
Type B - Through the L5-S1 facet joint
Type C - Violates the spinal canal.
The lumbosacral ligaments are very
strong, patients presenting with an injury in this transitional zone have
usually sustained very high-energy trauma.
Like cervical spine injuries, lumbosacral injuries can be viewed conceptually as
unilateral or bilateral dislocations, with or without accompanying fractures.
Displacement can vary from lumbosacral subluxation to complete lumbopelvic
dissociation. Isler proposed a system for assessing lumbosacral injury on the
basis of the location of the pelvic ring fracture relative to the L5-S1 facet
joint . A vertical sacral fracture lateral to the L5-S1 facet joint
is unlikely to have an impact on lumbosacral stability but may affect pelvic
ring stability. Fractures crossing through the L5-S1 facet joint can be
differentiated as extra-articular fractures of the lumbosacral junction and
articular dislocations with various stages of displacement of the L5 and S1
articular processes. Fractures crossing into the neural arch medial to the L5-S1
joint are usually complex and inherently unstable, necessitating Lumbopelvic stabilization.
Spinal cord injury classification
Classified in a methodical fashion by the American
Spinal Injury Association partly on the basis of the original work of Frankel.
Frankel system (1969)
Complete: No motor or sensory
Motor useful (grade 3 or higher)
Intact: Normal sensory and motor
|American Spinal Injury Association
The systems above, however,
incompletely address sacral injuries and the greater
variability of neural deficits arising from root injuries.
Gibbons et al. designed a useful
four-stage system specifically to grade sacral neurological injuries.
Stage 1 - No injury
Stage 2 - Parasthesias only
Stage 3 - Motor loss but bowel and
bladder control intact
Stage 4 - Impaired bowel and/or
A three-stage system of stability
classification has been proposed for sacral injuries.
Stage A - Osseoligamentous injury with retention of structural function
Stage B - Occult osseoligamentous disruption
Stage C - Obvious complete osseoligamentous disruption
Differentiation between Stage-A and B injuries can
be very difficult and may require provocative tests, such as weight-bearing and
traction studies, or repeated imaging over time.
By convention, any sacral or
posterior pelvic fracture-displacement of 1 cm is considered to be unstable.
Approximately 30% of sacral fractures
are identified late.
Sacral injury should be suspected in
any patient reporting peripelvic pain.
Inspection and palpation of the entire
body is necessary following high-energy blunt trauma, especially in the presence
of an altered sensorium. Lacerations, bruising, tenderness, swelling, and
crepitus are clear signs of a potential underlying injury. More specific signs
suggesting possible sacral injury include a posterior sacral osseous prominence
or a palpable subcutaneous fluid mass consistent with lumbosacral fascial
degloving (Morel-Lavelle lesion).
Patients with a suspected sacral fracture should undergo functional assessment
of the lower sacral roots, including
Determination of spontaneous and maximum
voluntary rectal sphincter contraction.
and pinprick sensation along the perianal concentric dermatomes of S2 through S5.
Specific reflexes - perianal wink, bulbocavernosus and
All patients with Sacral fractures
should have a digital rectal examination and female patients should undergo a vaginal examination to
exclude an occult open pelvic fracture.
Pelvic ring stability can be tested
manually by gently applied internal and external rotation of the iliac wings.
Lower-extremity push-and-pull tests with supplemental radiographic documentation
of pelvic shifting have been described but are not commonly performed.
In patients who can walk, the
presence of mechanically related low-back or buttock pain may indicate a sacral
Due to sacral inclination true AP pelvis not adequate to asses sacral
injuries, Pelvic inlet and outlet views improve visualization of the sacrum.
|| Pelvic outlet
- AP Pelvis - Provides limited visualization of the sacrum due to the
inclination angle of the sacrum.
- Pelvic inlet - Shows the sacral spinal canal and a superior view of
outlet - Provides true AP visualization of the
- Ferguson view - Centrally coned-down modification of a pelvic
outlet view directed perpendicular to the sacral inclination to allow en face
visualization of the entire sacrum.
- Lateral sacrum - Simple effective radiograph for screening and assessing sacral injuries
Nork et al. identified several radiographic indicators of potential sacral
- Fracture L5 transverse process (found in 61% of patients
with a sacral fracture)
- Paradoxical pelvic inlet view found on supine AP pelvis radiograph (92% of patients)
sign indicative of anterior sacral foraminal disruption
Computed Axial Tomography
CT Scanning is the preferred modality for diagnosing suspected or known
posterior injury to the pelvic ring. A dedicated sacral computed tomography scan
with 2-mm or thinner cuts as well as sagittal and coronal reformatted views
offers superior visualization of a disrupted sacrum and is useful for
complex sacral fractures.
Magnetic Resonance Imaging
May be helpful for patients presenting with unexplained sacral
neurological deficits after trauma.
Perineal somatosensory evoked potentials and anal sphincter
electromyography are useful for assessing patients with a possible neurological
deficit related to sacral injury or as a monitoring tool during surgical
intervention. Electrodiagnostic evaluation can also be used to differentiate
upper motor neuron lesions from spinal cord injury concurrent with sacral trauma
or for patients with an injury to the lower part of the urinary tract, for whom
neurological evaluation may be difficult.
Cystometrography performed with
sphincter electromyography and postvoiding residual measurements can be used as
a follow-up test for patients with a neurogenic bladder. However,
electromyography is not as useful in the acute setting, as abnormalities may
take several weeks to emerge.
Assessment of Sacral injuries
Five basic principles must be
followed when assessing a sacral injury.
Presence of active bleeding
Presence of an open fracture
Pattern and stability of skeletal
Systemic injury load
Presence of active bleeding:
Life-threatening injury to the iliac vessels, anterior perisacral venous
plexus, or superior gluteal artery can occur.
Presence of an open fracture:
Open sacral fractures substantially affects treatment and
prognosis. A variant of a true open fracture is an extensive lumbosacral
fascial degloving injury similar to that described in Morel-Lavelle syndrome.
Technically, these injuries are closed, but it is a substantial challenge to
treat them because of the severity of the soft-tissue trauma.
Neurological injury: Neurological injury
may involve the cauda equina, the lumbosacral
plexus, the sacral plexus, and the sympathetic and parasympathetic chains.
Pattern and stability of skeletal
injury: The issue of defining stability with respect to the pelvic ring remains largely
unresolved. Because of the pelvic ring's strong dependence on ligamentous
support, any posterior ligamentous disruption of the pelvic ring is likely to be
unstable. By convention, any sacral or posterior pelvic fracture-displacement of
1 cm is considered to be unstable. (See Stability
Systemic injury load: The cumulative injury load
to the patient has considerable short and long-term implications for
treatment and outcome. Certain patients or fractures may not be amenable to
Early treatment of substantial unstable sacral injuries may include:
General resuscitation measures
reduction of a displaced pelvic ring fracture using skeletal traction,
application of an anterior external fixator, placement of a pelvic clamp, or use
of a wrap-around sheet.
Angiographic embolisation of bleeding
pelvic vessels if patient remains haemodynamically unstable.
Nonoperative care consists mainly of
activity modification aimed at preventing further fracture displacement. This
may consist of prolonged bed rest in traction, bed rest in a brace, simple bed
rest, or early
mobilization with protected weight-bearing.
The typical time frame for healing of a posterior pelvic ring fracture is 2 to 4
months. This allows for a transitional period of protected weight-bearing of 1 to 2 months.
Remember in all patients on prolonged
Repeat imaging studies should be performed to verify that
fracture-healing is proceeding with satisfactory alignment.
displacement, deterioration of neurological function, or persistent pain with
attempts at mobilization may indicate failure of conservative treatment.
Indications for nonoperative management are vague and historically have included
nearly all sacral fracture patterns. Contraindications to nonoperative care are
relative but include fractures with soft-tissue compromise, an incomplete
neurological deficit with objective evidence of neural compression, and
extensive disruption of the posterior lumbosacral ligaments. Patients with
multiple injuries often benefit from timely surgical intervention in order to
Surgical intervention for patients with a sacral fracture should incorporate
clear and realistically attainable goals.
Fracture stabilization and lumbosacral realignment
Optimization of the chances for neurological recovery
Debridement of open injuries and compromised soft tissues,
Minimization of additional morbidity.
Timing of any surgical intervention should be chosen on the basis of
treatment goals, the patient's general medical status, and the invasiveness of
the surgical procedure. Delayed decompression of neural elements beyond 2 weeks may adversely
affect chances for neurological recovery. Most minimally invasive procedures
require early closed reduction and are limited in terms of the amount of
reduction that is attainable and the overall biomechanical stiffness of the
construct. Ultimately, when the treatment is being chosen, the advantages and
drawbacks of each approach should be carefully considered.
Sacral roots subjected
to contusion, compression, or traction caused by angulation, translation, or
direct compression have a theoretical chance of recovery.
Neural recovery of transected or avulsed sacral nerve roots is unlikely.
Establishing the benefits of decompression over a nonoperative approach in
neurologically impaired patients is difficult. Neurological improvement rates of
up to 80% are frequently quoted, regardless of the type of operative or
Given an overall rate of neurological improvement of approximately 80%
regardless of treatment, the indications for and timing of surgical
decompression in patients with neurological injuries are somewhat controversial.
From a neurophysiological standpoint,
decompression of compromised neural elements is preferably performed early,
within the first 24 to 72 hours following injury.
Neural decompression can be achieved indirectly with
fracture reduction or directly with a laminectomy. Early surgical decompression
may be associated with an increased risk of haemorrhage and wound-healing
complications due to soft-tissue contusion and possibly to cerebrospinal fluid
Surgical decompression as an isolated procedure— i.e., without
stabilization—is rarely indicated.
Surgical decompression may be less useful in
patients with transected sacral roots and reconstruction of root avulsions is impossible.
Traumatically transected roots are commonly associated with Denis zone-III
injuries with Roy-Camille type-3 displacement.
Avulsions of the lumbopelvic
plexus are associated with severely displaced zone-II injuries (vertical shear
Surgery should be considered if there is a
reasonable chance of restoring even unilateral lower sacral root function
because such function is sufficient for voluntary bowel and bladder control.
An acceptable approach to early management of sacral injuries is an attempt at
minimal reduction and stabilization. The adequacy of reduction is then assessed
with computed tomography combined with repeat neurological and possibly
electrodiagnostic examination to characterize persistent neurological deficits.
In the presence of satisfactory skeletal stabilization but persistent
neuroforaminal or spinal canal compromise, a focal limited decompression may be
performed within the first 2 weeks after injury, with use of a limited midline
exposure and fluoroscopy-guided focal laminectomy.
Patients presenting with
a severely displaced fracture that is unsuitable for closed reduction and percutaneous stabilization should be considered for a comprehensive posterior
decompression and stabilization procedure with use of the most appropriate
stabilization methods available.
Surgical Stabilization Techniques
Consider anterior pelvic ring
stabilization prior to addressing the posterior sacral injury. Methods include,
anterior plate fixation, external fixation, or the use of retrograde pubic
Ensure stability of the lumbosacral
articulation where indicated.
Anterior sacral approach,
decompression and stabilization has substantial approach-related morbidity
and provides limited surgical exposure.
Where possible posterior sacral
stabilization should offer a high degree of mechanical construct stiffness while
producing a low implant profile that minimizes the risk of posterior soft-tissue
Posterior sacral stabilization
Percutaneous Sacroiliac screws - The
vast majority of sacral injuries can be effectively treated with posterior
percutaneously based approaches. Percutaneous placement of sacroiliac screws may
be contraindicated in patients with anomalous transitional lumbosacral anatomy
or when closed fracture reduction cannot be accomplished. Fixation with
this method is very challenging in patients with highly displaced zone-II
fractures (vertical shear injuries).
Zone-II fractures with segmental comminution are susceptible to overcompression
and secondary foraminal entrapment when an iliosacral compression screw is used.
Such injuries may be considered for fixation with two static sacroiliac screws
or for iliolumbar segmental fixation.
Open reduction of the posterior aspect of the pelvic ring with plate fixation
and screw insertion into the sacral ala, as described by Roy-Camille et al.,
is an infrequently used strategy.
The application of vertically aligned plates
on the posterior aspect of the sacral ala with anteroposterior small-fragment
screw fixation is also of limited value because of the frequent presence of
comminution and osteopenia at the fracture site.
Use of a posterior iliac
tension-band plate as a supplemental internal fixation method with sacroiliac
screw fixation can facilitate open fracture reduction and enhance biomechanical
stiffness. However, it requires a posterior two-incision approach, which has
been associated with an increased rate of wound-healing complications.
The most stable method of lumbosacral
fixation involves lower lumbar pedicle screw fixation and iliac screw fixation
with longitudanal and transverse connecting rods.
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