Treatment of Spinopelvic Dissociation

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Treatment of Spinopelvic Dissociation A Critical Analysis Review Abstract » Multiplanar sacral fractures are characterized by the combination of horizontal and bilateral vertical fracture lines, leading to complex fracture types.

Ian David Kaye, MD Richard S. Yoon, MD William Stickney, DO Joseph Snavely, MD Alexander R. Vaccaro, MD, PhD, MBA Frank A. Liporace, MD

Investigation performed at the Division of Orthopaedic Trauma, Jersey City Medical Center, RWJBarnabas Health, Jersey City, New Jersey

» With a resultant disconnect between the cephalad axial spine and the caudad segment attached to the pelvis and lower extremities, these fracture characteristics, along with associated soft-tissue complications, make these injuries difficult to treat. » Outcomes are maximized with stable fixation and often are based on initial neurological compromise, which can be a reliable predictor of a return to a functional level. » Several methods of reconstructing the posterior pelvic-sacral complex exist, each with its own advantages and disadvantages. » Surgeons should select a fixation strategy on the basis of a careful analysis of the specific fracture pattern and resultant vectors causative of pelvic, sacral, and spinal deformity.

T

he sacrum plays a critical role in the stability of the lower body. It serves as the mechanical nucleus of the spine and anchors the axial spine to the appendicular skeleton through the sacroiliac articulations. The ligamentous connection at the sacroiliac joint as well as the sacral connections to the pelvis, including the sacrospinous and sacrotuberous ligaments, are among the strongest in the body1. Multiplanar fractures are characterized by both horizontal and vertical fracture lines, forming an H, Y, T, or U-shaped pattern (Fig. 1). While the upper part of the sacrum remains connected to the lumbar spine, the lower part of the sacrum remains attached to the pelvis, creating the aptly called spinopelvic dissociation2-4. These injuries are difficult to treat and are associated with high mortality and morbidity, including concomitant orthopaedic polytrauma,

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JBJS REVIEWS 2018;6(1):e7

neurological, soft-tissue, and vascular injuries4. Multiplanar sacral fractures occur in the setting of high-energy trauma, including motor-vehicle accidents, crush injuries, and blast injuries, and frequently are seen after falls from a height, leading to the early eponym, the “suicidal jumper’s fracture.”2,5,6 Consequently, they are frequently associated with other injuries, including concomitant spine injuries and pelvic ring disruptions7,8. These injuries are notoriously difficult to detect on radiographic imaging and have been missed in the past; however, with the widespread use of advanced imaging, specifically computed tomography (CT), these injuries generally are diagnosed as part of the initial trauma work-up. The purpose of the present article is to review the diagnostic, work-up, and available treatment strategies for this complex injury.

Disclosure: No external funds were received in support of the present study. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work (http://links.lww.com/JBJSREV/A284).

· http://dx.doi.org/10.2106/JBJS.RVW.16.00119

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Tr e a t m e n t o f S p i n o p e l v i c D i s s o c i a t i o n

Fig. 1 Illustrations depicting multiplanar sacral fracture pattern types, including H-shaped (Fig. 1-A), Y-shaped (Fig. 1-B), T-shaped (Fig. 1-C), and U-shaped (Fig. 1-D).

Classification Several classification systems have been proposed for the evaluation of sacral fractures. Early classification systems described by Denis et al. and Tile underscored the importance of the sacrum in pelvic stability and the association with pelvic ring injuries7,9. Denis et al. classified sacral fractures on the basis of the location of the vertical fracture line. The Denis classification system has implications for the likelihood of sacral nerve root injury, with a higher likelihood of injury as the fracture line moves medially. Type-I fractures lie lateral to the sacral foramina, type-II

Fig. 2 Illustration depicting the Denis classification system according to the location of the fracture in relation to the foramen. Type-I fractures lie lateral to the neural foramen, type-II fractures violate the foramen, and type-III fractures lie medial to the foramen.

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fractures violate the foramina, and typeIII fractures lie medial to the sacral foramina and are associated with neurological injury rates of .50% (Fig. 2)7. This classification system was later modified by Strange-Vognsen and Lebech to include a type-IV segmental comminution pattern of the first sacral vertebral body10. Sacral fractures at the lumbosacral junction were further elucidated by Isler, who defined a type-I injury as a fracture exiting the lumbosacral junction lateral to the L5 to S1 facet, a type-II injury as a fracture through the facet, and a type-III injury as a fracture medial to the facet, violating the sacral canal and possibly causing lumbosacral instability (Fig. 3)11. Fractures lateral to the facet joint are understandably more stable as the joint is not compromised. Roy-Camille and colleagues classified the horizontal sacral fracture in their review of the “suicidal jumper’s fracture” (Fig. 4)5. According to that system, a type-I horizontal fracture is a flexion-type injury with a resultant kyphotic deformity of the sacrum but without fracture displacement, a typeII injury is a flexion-type injury with resultant posterior displacement of the cephalad segment relative to the caudad segment, and a type-III injury is an extension-type injury with resultant anterior translation of the cephalad segment. Classification as either type II or type III largely depends on whether the segments are more kyphotic (type II) or lordotic (type III) at the time of

axial loading. Several authors have contributed anatomical classification schemes, describing the fracture lines as forming an H, U, T, or Y shape4,12,13. Multiplanar sacral fractures cause instability of the spinopelvic junction when the fracture lines cause a separation of the upper part of the sacrum and spine from the remainder of the sacrum and pelvis. The resultant spinopelvic dissociation must be distinguished from other unstable injuries around the sacrum, such as bilateral sacroiliac joint dislocation or lumbosacral fracturedislocation2.

Fig. 3 Illustration depicting the Isler classification system according to the location of the fracture in relation to the L5-S1 facet. Type-I fractures occur lateral to the facet (A), type-II fractures occur through the facet (B), and type-III fractures occur medial to the facet, which by definition violates the spinal canal (C).

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Fig. 4 Illustration depicting the Roy-Camille classification system for what was originally described as a “suicidal jumper’s fracture.” Type I is a flexion-type injury with a resultant kyphotic deformity of the sacrum but without franocture displacement. Type II is also a flexion-type injury, but with resultant posterior displacement of the cephalad segment relative to the caudad segment. Type III is an extension-type injury with resultant anterior translation of the cephalad segment.

TABLE I

Lumbosacral Injury Classification System (LSICS)14 Points* Morphology type Flexion compression #20° kyphosis

1

.20° kyphosis

2

Axial compression Without canal/foraminal encroachment

2

With canal/foraminal encroachment

3

Translation/rotation Anterior or posterior translation of upper sacrum

3 3

Lumbosacral facet injury or dislocation

3

Vertical translation or instability Blast/shear (severe comminution/bone loss)

3 4

Posterior ligamentous complex status Intact

0

Indeterminate Disrupted

1 2

Neurological status Intact

0

Paresthesias only

1

Lower-extremity motor deficit

2

Bowel and/or bladder dysfunction

3

Progressive neurological deficit

4

*Determination of nonoperative versus operative treatment is based on a summation of the 3 categories (morphology, integrity of the posterior ligamentous complex, and neurological status); scores of 1 to 3 would recommend nonoperative treatment, whereas scores of $5 would recommend operative treatment, which consists of reduction, decompression, and stabilization. A score of exactly 4 is controversial, and treatment is determined by the surgeon.

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Most recently, Lehman et al. proposed a new fracture-classification system in 2012 called the lumbosacral injury classification system (LSICS) (Table I)14. This system was developed in an attempt to improve the prediction of outcomes while maintaining a high degree of interobserver reliability. The system is based on 3 characteristics: injury morphology, posterior ligamentous integrity, and neurological status. It also accounts for several modifiers when determining surgical indications, including systemic injury load, soft-tissue status, and expected mobility status. The authors found good to excellent interobserver and intraobserver reliability, although reliability at a multicenter level remains to be determined. Clinical Evaluation Initial assessment must include advanced trauma life support protocols. Many complex sacral fractures initially were missed because of inadequate imaging8,15. Findings on clinical examination may include urinary retention and decreased anal sphincter tone16. The sequelae after delayed diagnosis

may include skin breakdown, infections of the urinary tract or lung, and symptomatic malunion. Furthermore, patients with a malunion are at risk for limb-length discrepancy, sitting imbalance, chronic pain, and permanent neurological impairment7,16,17. General examination should include a complete skin assessment, with particular attention to the posterior skin and the perineum. Internal soft-tissue degloving and a Morel-Lavallée lesion may be encountered. Pelvic and rectal examinations should be performed routinely to determine any associated injuries caused by osseous fragments. Assessment of pelvic stability, with rotational and vertical stressing of the pelvis, is critical as well18. Full neurological evaluation should be performed according to American Spinal Injury Association guidelines. Gibbons et al. proposed a system designed specifically for the evaluation of injuries of the sacral plexus19, with the injuries being classified as type 1 (normal nerve function), type 2 (impaired sensation), type 3 (lower-extremity weakness with

intact bowel and bladder function), or type 4 (absent bowel and bladder function). Common radiographic features of multiplanar sacral fractures include disruption of the sacral foramina, a paradoxical inlet view of the upper part of the sacrum (representing focal kyphosis), lumbosacral disruption, and an associated pelvic ring injury (Fig. 5). The transverse fracture lines may be missed on axial CT cuts, and additional radiographic views and 3-dimensional CT reconstruction may be useful for operative planning (Fig. 5). The transverse nature of the fracture can be confirmed on the lateral projection of the sacrum. The commonly seen kyphotic deformity develops secondary to the translation of the unstable cephalad sacral segment and can be very misleading as an anteroposterior radiograph can present as an inlet view because of the kyphosis. However, in the setting of minimal kyphotic deformity at the fracture site, this finding may be absent12. More subtle findings may include associated fractures, such as those of the lumbar spine transverse processes12,16,20-22.

Fig. 5 Fig. 5-A Anteroposterior radiograph of the pelvis of a patient with a U-shaped sacral fracture, demonstrating the paradoxical inlet view of the sacrum secondary to the kyphotic deformity. Figs. 5-B, 5C, and 5-D Axial, sagittal, and 3-dimensional CT scans for same patient, demonstrating vertical fracture lines through the sacral foramina with associated transverse fracture resulting in kyphotic deformity (Roy-Camille type-II fracture) with posterior displacement.

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Treatment Because of improvements in diagnosis as well as the evolution of fixation techniques, operative treatment has largely supplanted nonoperative treatment of spinopelvic dissociations. Nonoperative treatment is reserved for patients who cannot tolerate an operation or (according to more recent guidelines) those who have concomitant lowerextremity injuries requiring a prolonged period of non-weight-bearing (approximately 3 months) and mild deformity14. Nonoperative treatment may involve a period of bed rest with skeletal traction or immobilization in an orthosis and non-weight-bearing precautions. Recumbency generally is not well tolerated and may result in morbidity, including skin breakdown, painful deformity, progressive neurological decline, limblength discrepancy, problems sitting, and immobility. Immobility plays a major role in a patient with multiple injuries. As patients with spinopelvic dissociation often have associated injuries, an early return to walking is critical. Operative intervention may result in earlier mobilization, which is associated with improved long-term outcomes related to quality-of-life measures, including pain and overall mood4. The timing of operative intervention in these cases is controversial. The principles of damage control orthopaedics frequently are employed in these settings15, and the benefits of early operative intervention, such as neurological recovery and quicker rehabilitation7, must be measured against the potential risk of hemodynamic instability, hemorrhage, wound complications, and cerebrospinal fluid leak. The ideal timing of operative intervention for spinopelvic dissociation seems to be within 1 to 2 weeks17. However, in the setting of cauda equina syndrome, urgent decompression within 24 hours is recommended23. Neurological Decompression The role of sacral decompression in the setting of complex fractures is controversial. Furthermore, whether to perform a limited decompression (through

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the fracture site24) or a full sacral laminectomy17 and when to optimally perform the decompression remain unknown. To our knowledge, no studies have specifically evaluated the utility of decompression, but the available evidence suggests that decompression may be beneficial. Although some studies have demonstrated partial or even complete resolution of deficits without decompression, others have documented both prognostic and potential neurological benefits in association with decompression3,12,24. Schildhauer et al., in a study of 34 patients with a vertically unstable sacral fracture, found that, without decompression, only 27% of patients had any signs of neurological improvement25. Conversely, in a different study of 18 patients with a U-type sacral fracture with complete bowel and/or bladder dysfunction, Schildhauer et al.17 reported that 15 patients (83%) had some degree of neurological recovery after sacral laminectomy and spinopelvic fixation. The authors found good prognosis following decompression even in cases without recovery: 6 of 7 patients with intact sacral roots regained bowel and bladder function, compared with only 4 of 11 when 1 or more roots were transected. Similarly, Bellabarba et al. found that lack of bowel and bladder function recovery was positively correlated with lumbosacral root transection26. In cases of neurological deficit, we generally recommend performing a sacral decompression with a laminectomy down to S4. The sacral nerve roots may be traced anteriorly out the ventral sacral foramina, and any retropulsed free bone fragments may be removed. Ventral canal decompression may be performed with angled downward-pushing impactors. If the CT scan demonstrates the presence of intraforaminal osseous fragments, decompression should be performed before fracture reduction in order to prevent further injury. Surgical Options Posterior Tension Band Plating Open reduction and plating offers the advantage of direct visualization of the

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Fig. 6 Illustration depicting the hypothetical position of a posterior tension band plate (A) and a minimally invasive adjustable posterior pelvic plate (B). Both constructs typically would also be supplemented with iliosacral screws.

reduction and the potential for direct decompression of the sacral canal. In cases of sacral fractures associated with an intact anterior cortex a posterior plate functions as a tension band, whereas in cases of anterior comminution it serves as a bridge plate (Fig. 6)27. Posterior plating is indicated if iliosacral screws are insufficient to stabilize a vertical, comminuted sacral fracture. They also can be useful in cases of sacral dysmorphism when there is an inadequate path for an iliosacral screw28. Suzuki et al. found posterior plating to be an effective method for the fixation of vertically unstable sacral fractures associated with posterior comminution27. Those authors described placing transiliac posterior plates just below the posterior superior iliac spines. This fixation strategy may be used alone or as a neutralizing device for iliosacral or transsacral screws. Simonain et al., in a cadaveric study in which screws alone were compared with screws and a plate, found no difference in fracture stability, provided that the reduction was adequate29. Precontouring of the posterior plates can prove challenging, and implant prominence must be considered when using a plate posteriorly. Open reduction and plate fixation, while offering improved reduction as a result of direct visualization and clamping, has been shown to be associated with increased rates of wound complications because of the larger exposure required. In patients with an extensive posterior soft-tissue

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injury, such as a Morel-Lavallée lesion, a less-invasive approach should be considered27. Adjustable Plates Minimally invasive adjustable plates have been developed as an alternative treatment strategy to tension band plating or iliosacral screws. Chen et al.30 introduced a minimally invasive adjustable plate to address issues with the aforementioned modalities (Fig. 6, B). Sixteen patients with posterior pelvic injury, 12 of whom had associated sacral fractures, were managed with adjustable plates. In all cases, the fixation was performed with the patient in the prone position and the adjustable plate was inserted after fracture reduction. If a gap remained at the fracture site, the plate also could be used as a reduction tool.

Subsequently, each patient was placed in the supine position for anterior fixation of the pelvic ring injury. After 24 to 38 months of follow-up, there were no cases of implant failure. Osseous union was achieved in all patients within 4 months postoperatively, and neurological symptoms decreased in all patients. Adjustable plate fixation may provide a viable alternative for the treatment of simple sacral fractures; however, its utility for the treatment of multiplanar or comminuted fracture patterns is unknown. While the minimally invasive approach decreases wound complications, operating room time, and blood loss compared with open reduction and fixation, the reduction has been reported as inferior, and lumbosacral decompression is not possible27. Rarely reported complications include

irritation at the site of the implant when the patient is lying supine, the need for implant removal, implant breakage, and loss of reduction31. Iliosacral Screws Iliosacral screws allow for the stabilization of sacral fractures and sacroiliac joint injuries through a minimally invasive approach. The screws may be placed percutaneously or through a limited open approach, on either side of the body, and with the patient in a prone or supine position. These advantages may be particularly useful when managing polytraumatized, hemodynamically compromised patients. Furthermore, in patients with soft-tissue injury, the sacropelvic region may be avoided altogether with the use of iliosacral screws. Potential disadvantages

Fig. 7 Axial CT scans of normal S1 (Fig. 7-A) and S2 (Fig. 7-B) corridors, with lines indicating “safe” passages for iliosacral screws.

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include an inability to directly visualize fracture reduction during percutaneous fixation, an inability to decompress the sacral canal, the potential for iatrogenic nerve injury, and limited strength of fixation. Safe iliosacral screw placement must be carefully planned, both preoperatively and intraoperatively (Fig. 7). During preoperative evaluation, the surgeon must consider several factors, including the presence of sacral dysmorphism, the orientation of fracture lines, deformity at the fracture site, bone quality, comminution, associated injuries, and the potential for malreduction. Sacral dysmorphism, in particular, may be present in 30% to 40% of adults32. Careful evaluation of both radiographs and CT scans can reveal the presence of abnormal sacral morphology, lumbarization of S1, or the sacralization of L5 vertebral bodies. Some of the characteristic findings of dysmorphism include a steeply sloped ala, collinearity between the iliac wings and the lumbosacral disc space, noncircular first sacral foramen, a residual disc space between the first and second sacral vertebral bodies, and obliquely oriented, residual transverse processes on the sacral ala32,33. Depending on the degree of deformity, the presence of sacral dysmorphism does not necessarily preclude the use of iliosacral screws. Gardner et al. attempted to determine the safe zone for screw placement in the setting of dysmorphism. They found that, in addition to the aforementioned radiographic characteristics, the sacroiliac joint may have tongue-in-groove irregularities, precluding the use of the iliocortical density as a landmark for the sacral ala34. Traditionally, the second sacral segment has been utilized for screw fixation because of the difficulties of using the first segment. Conflitti et al., in a study of sacral injuries that were treated with iliosacral screws in patients with dysmorphism, found that the average diameter of the osseous safe zone in the first sacral segment was 13.2 mm (range, 7.2 to 17.2 mm)35. The maximum length of

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screw that could be utilized averaged 100.8 mm, without the possibility of a transsacral screw. This length was limited by the oblique orientation of the safe screw trajectory ending at the anterior part of the sacrum. The safe zone for the second sacral segment averaged 15.2 mm (range, 11.3 to 17.7 mm) in diameter, and the maximum screw length averaged 151.9 mm (120.7 to 178.4 mm), allowing for potential transsacral screw placement. In the setting of sacral dysmorphism, the second sacral segment more likely provides a larger window for safe screw placement. Iliosacral screw placement varies according to the pattern of injury; longer screws that can traverse the entire spinopelvic region are preferred for the treatment of sacral fractures, whereas shorter screws are used for the treatment of pure sacroiliac joint instability. In cases of comminuted fracture patterns such as Denis type-II fractures, care must be taken to avoid compression of the neural foramen28. Iliosacral screws typically do not provide adequate fixation to maintain reduction when used alone for the treatment of vertically unstable, comminuted fracture patterns27. In the setting of a multiplanar sacral fracture, fixation may be achieved with the transsacral or unilateral placement of 1 screw or multiple screws within S1 or S2. These screws may be either fully or partially threaded, depending on the fracture pattern and the degree of comminution. In the setting of a simple fracture line and good bone quality, the surgeon may consider using a partially threaded screw, with care being taken not to overcompress the foramina or nerve roots. In the setting of a comminuted fracture and/or poor bone quality, the goal often will be to fix the bone in place and prevent additional deformity. One or 2 fully threaded screws may be used to achieve this goal and avoid overcompression of the neural foramina36. However, Simonain et al. found no difference in stability between 1 and 2 iliosacral screws when used for the treatment of transforaminal sacral fractures29. Iliosacral screws placed

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transsacrally to the contralateral sacroiliac joint have demonstrated increased fixation strength37,38. Despite comprehensive knowledge of sacral anatomy and adequate usage of intraoperative fluoroscopy, inadvertent extraosseous placement of iliosacral screws may occur. Penetration of the anterior part of the sacral ala is best detected on a pelvic inlet view. The pelvic outlet view is used to evaluate for superior penetration of iliosacral screws into the S1 foramen39. Because of varying degrees of sacral dysmorphism and lumbosacral lordosis, Ziran et al. proposed using landmarks rather than predetermined angles on fluoroscopic views when placing iliosacral screws40. Those authors recommend determining the anterior border of the S1 ala on an inlet view via superimposition of the anterior S1 and S2 alar opacities. For determination of the superior aspect of the S1 foramen on an outlet view, it is recommended to superimpose the S2 foramen over the superior portion of the pubic symphysis. As demonstrated by Sagi and Lindvall, the first sacral foramen is tangential in nature and slight posterior placement of the screw may violate the first foramen as opposed to injuring the nerve anteriorly41. Transsacral Bar Fixation Unstable sacral fractures or posterior pelvic ring patterns mandating bilateral fixation can be challenging to address in patients with sacral dysmorphism. If the safe zone of S2 is only wide enough for 1 screw, transsacral fixation is a minimally invasive alternative to plating or triangular osteosynthesis. Transsacral fixation with use of locking bars or cannulated screws has been described42. Transsacral fixation has the distinct advantage of engaging the cortices of the sacroiliac joint bilaterally, potentially augmenting fixation strength through the entire spinopelvic junction. Several authors have advocated using transsacral screws and bars as an effective treatment modality for sacral fractures37,38,42,43. Moed and Whiting found that fixation with transsacral cannulated screws with

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distal self-locking bolts was an effective method, with no instances of malreduction, iatrogenic nerve injury, or screw malpositioning in their initial series42. Tabaie et al., in a cadaveric model involving the use of 7.0-mm screws, compared iliosacral screw strength with transsacral screw strength44. The transsacral construct performed significantly better in terms of load to failure (p 5 0.02). Transsacral screw fixation follows the same principles as iliosacral screw fixation, with the need for an additional skin incision on the contralateral side if a locked construct is to be used. The surgeon should carefully evaluate preoperative radiographs to ensure that transsacral fixation is possible, which may not be the case in the setting of sacral dysmorphism. Furthermore, fracture reduction must be adequate to safely allow passage of the device. Because of the difficulty of obtaining appropriate intraoperative fluoroscopic views and the proximity of surrounding neurovascular structures, transsacral fixation should only be performed by surgeons who have adequate expertise in posterior pelvic fixation. As with iliosacral screw fixation, preoperative planning should include anteroposterior, lateral, and inlet and outlet radiographic views as well as preoperative pelvic CT scans39. Potential complications of transsacral fixation include malreduction, broken screws or bars, iatrogenic nerve root compression, vascular injury, and infection45. Spinopelvic Fixation Spinopelvic fixation with or without sacroiliac fixation was developed in response to the difficulty of obtaining a rigid construct in cases of vertically unstable transforaminal sacral fractures46. Theoretically, this fixation modality unloads the damaged sacrum, bypassing it with fixation into the lumbar spine and the iliac wings, thus reconnecting the hemipelvis to the axial skeleton47. In the cadaveric biomechanical study by Schildhauer et al., triangular osteosynthesis was compared with an iliosacral screw construct for the fixation of

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unstable sacral factures48. The authors reported decreased loss of reduction and less motion with cyclic loading in the triangular osteosynthesis group. These findings suggest that, in cases of vertically unstable sacral fractures, early patient mobilization would be safer and more favorable for prognosis following triangular osteosynthesis as opposed to iliosacral screw fixation alone. In another study, Schildhauer et al. tested the triangular osteosynthesis construct clinically in 18 patients with highly displaced, comminuted sacral fractures with spinopelvic instability and reported favorable results, with only a 9% rate of instrumentation loosening17. Triangular osteosynthesis is primarily indicated for the treatment of vertically unstable fractures without substantial impaction. Isler type-I fractures (fractures lateral to the L5-S1 facet joint) are more stable than type-II fractures (fractures through the L5-S1 articulation) and type-III fractures (fractures medial to the articulation), which are more likely to be vertically unstable. Such vertical instability is associated with increasing displacement of the hemipelvis and resultant damage to the lumbosacral articulation, thereby pushing the treatment algorithm in favor of a triangular osteosynthesis construct47,49. One must also evaluate the L5 pedicle for safe placement of a pedicle screw. If the L5 transverse process is avulsed by the iliolumbar ligament, the L5 pedicle also may be damaged as a result. This scenario would require the surgeon to use the L4 pedicle for screw fixation or to consider alternative treatment options47. Although spinopelvic fixation has a high success rate for maintaining reduction and also may allow for earlier patient mobilization, it can be associated with complications26,50. Bellabarba et al., in a review of 19 consecutive patients, reported that the most common complications associated with this treatment modality were fracture of the connecting rods (31%) and woundhealing disturbances (26%)26. However, neither complication posed a

long-term threat to outcome. Most commonly, poor prognosis and morbidity were associated with either a dural tear or nerve root avulsion. In the study by Lindahl et al.50, 36 patients were managed with direct decompression and lumbopelvic fixation for the treatment of H-type sacral fractures. Despite good or excellent radiographic outcomes in all patients, only 58% had a good clinical outcome after a minimum duration of follow-up of 18 months. Timing of surgery, age, and Injury Severity Score did not influence outcome. However, complete fracture displacement portended a worse neurological outcome, with improvement being noted in only 31% of patients with complete displacement as compared with 75% of those with partial displacement (p 5 0.038). While the performance of a laminectomy did not influence outcomes, those authors found that the adequacy of fracture reduction, when controlling for initial neurological status, correlated with outcomes (p 5 0.011). Authors’ Preferred Technique for the Treatment of Spinopelvic Dissociation The authors prefer to use triangular osteosynthesis for the treatment of spinopelvic dissociation. Generally, bilateral pedicle screws are placed at L4 and L5 and 2 iliac bolts are placed in the pelvis after the placement of a transsacral screw (Fig. 8). As already mentioned, in cases of neurological deficit, a sacral laminectomy or decompression through the fracture site is performed. The procedure is performed with the patient prone on a fracture table, which allows traction to be more easily applied. For spinopelvic dissociations (U or H-shaped), a perineal post is used for counter-traction. We generally perform a midline approach from L4 to S4, exposing the transverse processes of L4 and L5 and the posterior superior iliac spines bilaterally. Alternatively, minimally invasive approaches for lumbopelvic fixation have been described recently, with less softtissue disruption and good outcomes51,52.

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Fig. 8 Figs. 8-A through 8-E Radiographs and CT scans of the pelvis and spine of a patient with a U-shaped sacral fracture (spinopelvic dissociation) that was fixed bilaterally with L4-L5 pedicle screws, iliac bolts, and sacroiliac screws. Figs. 8-A and 8-B Anteroposterior (Fig. 8-A) and lateral (Fig. 8-B) pelvic radiographs made immediately after the procedure. Figs. 8-C and 8-D CT scans, made immediately after the procedure, demonstrating some residual kyphotic alignment at the sacrum. A sacral laminectomy and partial sacral body resection were performed at the time of the procedure (as can be seen when the postoperative scan shown in Figure 8-D is compared with preoperative scan shown in Figure 8-E). At 3 months of follow-up, the patient had normal bowel and bladder function with impaired sexual function and bilateral foot paresthesias.

After dissection, the fracture site is exposed with attempted preservation of the overlying periosteum. All devitalized tissue is sharply debrided. A sacral laminectomy is performed down to S4 in order to allow for the visualization of the exiting roots from the ventral foramen and the removal of any compressive osseous fragments. In cases of root transection, the nerves are sharply debrided. Once the roots have been identified, care must be taken to prevent iatrogenic injury during reduction maneuvers and fixation. Once the decompression is complete, fracture reduction may be performed by applying longitudinal traction through both lower extremities

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with femoral skeletal traction, countered by the perineal post. Hip extension may aid in reduction. Sometimes, the placement of a distractor between L5 and the ilium can lead to fracture reduction. Reduction is confirmed with the use of fluoroscopy, and the fracture is clamped and compressed with a periarticular clamp on the outside of the posterior superior iliac spine (through stab incisions). A percutaneous transsacral screw may be placed to hold the reduction by drilling with a 3.2-mm drill across the sacrum, perpendicular to the fracture lines. The trajectory is cephalad to the S1 foramen on the pelvic outlet view and posterior to the anterior sacral cortex on

the pelvic inlet view (see section on iliosacral screws earlier). A partially threaded cannulated screw with a washer is inserted to compress the sacral fracture. Care must be taken during these steps to ensure that no iatrogenic injury occurs to the decompressed roots. Sagi explained that direct or indirect reduction should be obtained before definitive spinopelvic fixation is performed rather than using the pedicle screw construct to effect a reduction by compression and distraction on the screw-rod construct47. That author noted that reduction via the latter method may lead to gapping of the fracture, with posterior and lateral

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Fig. 9 Illustration depicting pelvic incidence, which is a measurement inherent to the pelvic anatomy and does not change with position. The pelvic incidence is the angle subtended by a line from the center of the S1 superior end plate to the femoral head and a line perpendicular to the S1 superior end plate.

displacement of the central fragment. Resultant lumbosacral scoliosis may lead to facet joint overloading and should be avoided. Once the fracture has been reduced and held with the screw, spinopelvic fixation may be applied. Bilateral L4 and L5 pedicle screws are placed in the usual manner. Next, iliac bolts are placed by using a 3.5-mm drill to create a path starting at the internal aspect of the posterior superior iliac spine and aiming

toward the greater trochanter, which is approximately 20° laterally and 30° caudally53. The screw path should be through the sciatic buttress between the inner and outer iliac tables above the sciatic notch. Accurate screw placement can be assessed with anteroposterior, lateral, and rollover obturator oblique images. A rod is then contoured and placed, connecting the lumbar pedicle screws and the iliac bolts. The adequacy of reduction is somewhat difficult to assess given the nature of the multiplanar fracture lines and the difficulty of estimating the reduction of the sacrum to the ilium. Hart et al. suggested measuring pelvic incidence to determine adequate fracture reduction13. Pelvic incidence is the angle subtended by a line from the center of the S1 superior end plate to the femoral head and a line perpendicular to the S1 superior end plate (Fig. 9); this radiographic measurement is inherent to the pelvic anatomy and does not change with position. Hart et al. found that patients with abnormally high pelvic incidence that did not correspond with the lumbar lordosis (610°) experienced high lumbar fatigue with persistent stance after the fixation of H-type sacral

fractures and concluded that pelvic incidence (restoration to 610° of lumbar lordosis) can be used to assess sagittal plane reduction in cases of spinopelvic dissociation. Summary The treatment of spinopelvic dissociation is complex and depends on injuryrelated factors. As understanding of the injury evolves, new algorithms may be developed for optimal treatment. Neurological outcome is most closely correlated with the occurrence of nerve-root transection during the traumatic event, which is a factor that is outside of the surgeon’s control. Fixation strategies and knowledge about implant-specific complications have improved. When indicated, percutaneous methods can help to avoid soft-tissue complications. When open methods are used, meticulous soft-tissue handling and low-profile instrumentation can mitigate the risk of infection. When indicated, operative treatment can provide appropriate stability, allowing for early mobilization and improved outcomes. Larger, collaborative multicenter studies may prove to be helpful for determining true incidence of spinopelvic dissociation, outcomes, and survivorship (Table II).

TABLE II Recommendations for Care* Recommendation

Grade

Radiographs have a limited role in fracture diagnosis and characterization

B

CT is the standard for diagnosis and fracture pattern characterization

B

Initial neurological deficit and/or injury portends poor clinical outcome regardless of quality of reduction and/or fixation

C

Open posterior approaches to the sacrum are associated with high wound-complication rates

C

For multiplanar sacral fractures, with or without lumbar spine involvement, the ideal fixation construct is via lumbosacral fixation and/or triangular osteosynthesis with or without iliosacral and/or transsacral screws

B

Prominent hardware is consistently an issue for lumbosacral fixation and/or triangular osteosynthesis

B

Clinical outcomes regarding treatment, via iliosacral screws alone, posterior tension band plating, sacral bars alone, and adjustable plates , are reliable in the short term follow-up period.

I

*Grade A indicates good evidence (Level-I studies with consistent findings) for or against recommending intervention. Grade B indicates fair evidence (Level-II or III studies with consistent findings) for or against recommending intervention. Grade C indicates conflicting or poor-quality evidence (Level-IV or V studies) not allowing a recommendation for or against intervention. Grade I indicates that there is insufficient evidence to make a recommendation.

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Ian David Kaye, MD1, Richard S. Yoon, MD2, William Stickney, DO3, Joseph Snavely, MD2, Alexander R. Vaccaro, MD, PhD, MBA1, Frank A. Liporace, MD3

11. Isler B. Lumbosacral lesions associated with pelvic ring injuries. J Orthop Trauma. 1990; 4(1):1-6.

1Division of Spine Surgery, Rothman Institute, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania

13. Hart RA, Badra MI, Madala A, Yoo JU. Use of

2Division

of Orthopaedic Trauma, Orlando Regional Medical Center, Orlando Health, Orlando, Florida

3Division

of Orthopaedic Trauma, Jersey City Medical Center, RWJBarnabas Health, Jersey City, New Jersey Email address for F.A. Liporace: liporace33@ gmail.com

ORCID iD for F.A. Liporace: 0000-00027082-5329

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