ReviewSacropelvic Fixation: A Comprehensive Review
Section snippets
Overview
The lumbosacral junction has complex anatomic features that make it a unique area of the spine [1]. It is the most mobile lumbar segment in the sagittal plane; however, its range of motion in the coronal plane is the narrowest of all spinal levels [2]. The lordotic curvature of the lumbar spine results in the lumbosacral segment having the most steeply angulated disc [3]. Load vectors in the setting of these unique anatomic parameters create the largest translational shear forces generated in
Anatomy
A comprehensive understanding of the spinopelvic anatomy and its variations is valuable in understanding and performing the various sacropelvic fixation techniques. The lumbar vertebrae are the largest of the human spine. They are characterized by a reniform shape, which is deeper and thicker ventrally than dorsally [15]. They differ from the thoracic spine in that they have transverse processes instead of lateral facet articulation with the ribs and a larger pedicle diameter [1], [2]. The fact
Classification of Pelvic Fixation Zones
The most widely used classification system for sacropelvic fixation was described by O'Brien et al. [22] in 2004. They divided the sacropelvis into three zones of fixation (Fig. 2). Zone I consists of S1 and the cephalad sacral alae, zone II encompasses the sacral alae below and S2, and zone III is the bilateral ilia. Zone I fixation with S1 screws or rods is the least biomechanically stable because of the high risk of facet fracture and screw pull-out [22], [23]. Zone II is noted for having
Pelvic Parameters
Spinal sagittal alignment is largely defined by the relationship of the spine to the pelvis. Analysis of the pelvis in the sagittal plane is typically assessed with three angular measurements: pelvic tilt (PT), pelvic incidence (PI), and sacral slope (SS) (Fig. 3) [29]. PT is defined as the angle between the vertical reference line and the line connecting the femoral head to the midpoint of the sacral plate. PT is usually elevated in the setting of sagittal imbalance as a compensatory
Indications
The most common indication for pelvic fixation in spine surgery is a long fusion to the sacrum. The tremendous flexion and cantilever moments at the lumbosacral junction require a rigid foundation to support the cephalad construct (Fig. 4). Cunningham et al. [33] showed that long fusions above L3 significantly increase the strain on S1 screws; therefore, augmenting the distal fixation with iliac screws helps protect the S1 screws. The cephalad fusion level at which sacropelvic fixation is
Preoperative Planning
Preoperative planning should involve the use of radiographs to formulate a three-dimensional scheme and determine the optimal screw path and positioning. Posteroanterior and lateral 36-inch radiographs should be part of the preoperative planning for all cases requiring sacropelvic fixation. These two views allow for the assessment of sagittal and coronal realignment and presence of pelvic obliquity, all of which are crucial factors in the correction of a spinal deformity [52]. Pelvic inlet and
Harrington Technique
Before the era of spinal instrumentation, sacropelvic fixation was attempted using whole-body casting. However, high pseudoarthrosis rates, complications of immobility, and inadequate correction led to the development of Harrington instrumentation [8], [57]. The Harrington technique consists of spinal distraction with cephalad and caudal hooks attached to the transverse processes or laminae while connected to a ratcheted rod [58]. Pseudoarthrosis rates were found to be high with this technique,
Conclusion
Sacropelvic fixation has evolved substantially since the advent of body casting in the 1960s. The two most widely used methods today, S2AI and iliac screw fixation techniques, offer comparable biomechanical stability and rates of fusion. Recent studies of the S2AI technique show significantly lower rates of instrumentation-related complications and reoperation rates compared with iliac screw fixation. Both methods are skill-dependent, but allow for rigid pelvic fixation and are interchangeable
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Cited by (24)
Does Prior Lumbar Fusion Influence Dislocation Risk in Hip Arthroplasty Performed for Femoral Neck Fracture?
2022, Journal of ArthroplastyCitation Excerpt :First, our study was unable to assess specific preoperative spinopelvic parameters or distinguish patients based on severity of residual spine disease following LF. In addition, we were unable to determine if prior LF included a fusion to the sacrum or pelvis, which has been shown to strongly influence spinopelvic mobility [23]. Similarly, this study only analyzed operatively fused lumbar spines, and future research should aim to determine whether arthritic spines behave similarly with respect to lumbopelvic kinematics.
Direct Iliac Screw vs Sacral-2-Alar-Iliac Screws Technique for Sacropelvic Fixation: Technical Nuances and a Review of the Literature
2023, International Journal of Spine SurgeryBiomechanical evaluation of multiple pelvic screws and multirod construct for the augmentation of lumbosacral junction in long spinal fusion surgery
2023, Frontiers in Bioengineering and Biotechnology
Author disclosures: MHED (none), MR (none), LO (none), KMK (personal fees and other from DePuy Synthes; personal fees from K2M and Orthofix, outside the submitted work).
IRB approval: Institutional review board approval was not required for this study.