Sacral fractures occur in nearly one half of all pelvic fractures, with most of them due to motor vehicle collisions, and approximately 25% are associated with some form of neurological injury (1). Neurological deficit following vertically unstable pelvic fractures is not unusual, with rates ranging from 24% to 60% depending on the location of the fracture, and it is a common cause of long-term disability following the disruption of the pelvic ring (2-6).
The type of neurological injury associated with sacral fractures is related to fracture type. The Denis classification of sacral fractures (1) categorizes them into zones I, II, and III. A zone I sacral fracture is characterized by a fracture lateral to the neural foramina, and results in a 6% chance of neurological injury, usually due to damage to the L5 nerve root from the vertically displaced sacral ala (1-6). A zone II fracture is one through the neural foramina, and results in a 28% chance of neurological injury due to damage to the L5, S1, or S2 nerve root (1). A zone III fracture is the most severe, as it involves the spinal canal, and carries with it a 57% chance of neurological injury (1). Additionally, bowel/bladder and/or sexual dysfunction are found in 76% of zone III fractures (1).
Various methods of stabilization can be used to treat sacral fractures with associated pelvic instability (1). Spinopelvic fixation is the most stable biomechanical construct as it effectively “skips” the comminuted sacral region and transmits weight from the spine to the ilium (1). However, compared with other methods, this method is much more invasive, can lead to a higher incidence of wound complications, and carries a higher risk for infection.
Iliosacral screws are often utilized in the treatment of these injuries, especially if there is significant soft tissue or bowel injury. If utilized, attention should first be directed toward management and stabilization of any anterior pelvic ring disruptions (7). Contraindications include failure to reduce the posterior displacement and inability to fluoroscopically visualize the posterior and lateral sacrum (7). Sacral fracture comminution is a relative contraindication as it may lead to iliosacral fixation failure.
The proper placement of iliosacral screws is technically demanding, and certain situations make it even more difficult. Vertical shear sacral fractures are associated with a higher rate of fixation failure when iliosacral screws are used. Disparities in the quality of bone available for screw purchase as well as the inability to compress at the fracture site for fear of nerve damage are reasons for this increase in failure. A retrospective review done by Griffin et al. (8) revealed a 13% rate of fixation failure when iliosacral screws were used in the presence of a vertical sacral fracture. However, this review found iliosacral screws to be useful in the management of vertically unstable pelvic fractures. Additionally, residual fracture displacement can greatly compromise the space available for safe screw placement, placing intracanal and sacral root nerve structures at risk (9). The L5 nerve root is also at risk with anterior placement of the iliosacral screw. In a study by Reilly et al. (9), the available area for safe placement of iliosacral screws decreased as the degree of displacement in the fracture increased.
The study revealed that nine screws could be placed safely in a nondisplaced fracture, while only three screws could be placed in a fracture displaced by 10 mm (9). Fractures with a displacement of greater than 10 mm led to greatly compromised available screw space (9).
In our patient, it is uncertain whether the fractures were reduced prior to iliosacral screw placement because preoperative, intraoperative, and immediate postoperative radiographic studies were not available for review.
While percutaneous iliosacral screws can be very useful in the treatment of certain pelvic injuries, complications can occur with their use. Preoperative evaluation of the patient’s pelvis morphology is imperative for a successful outcome. Equally important is an adequate reduction with stable fixation. We present a case in which stabilization was achieved using spinopelvic fixation with improved neurological recovery.
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