Biomechanical analysis of motion following sacroiliac joint fusion using lateral sacroiliac screws with or without lumbosacral instrumented fusion

A literature review of biomechanical studies on physiological and pathological sacroiliac joints: Articular surface structure, joint motion, dysfunction and treatments

BACKGROUND

Sacroiliac joints are affected by mechanical environments; the joints are formed under mechanical stimulation, receive impact of walking between the upper and lower parts of the bodies and can be a cause of pain due to non-physiological loads. However, there are so far very few studies that reviewed biomechanics of physiological and pathological sacroiliac joints. This review article aims to describe the current sacroiliac joint biomechanics.

METHODS

Previous original papers have been summarized based on three categories: articular surface structure, sacroiliac joint motion and sacroiliac joint dysfunction and treatments.

FINDINGS

Although the articular surface morphologies vary greatly from individual to individual, many researchers have tried to classify the joints into several types. It has been suggested that the surface morphologies may not change regardless of joint dysfunction, however, the relationship between the joint structure and pain are still unclear. The range of sacroiliac joint motion is demonstrated to be less than 1 mm and there is no difference between physiological and pathological joints. The sacroiliac joint absorbs shock within the pelvis by the joint structures of pelvic morphology, ligaments and fat tissues. The morphology and motion of the sacroiliac joints may be optimized for upright bipedal walking.

INTERPRETATION

There is no doubt that pelvic mechanical environments affect pain induction and treatment; however, no one has yet provided a concrete explanation. Future research could help develop treatments based on sacroiliac joint biomechanics to support joint function.

A cadaveric biomechanical evaluation of anterior posterior compression II injuries

PURPOSE

Pelvic fractures are associated with high morbidity and often require surgical intervention. An Anterior Posterior Compression (APC) II injury consists of disruption at the pubic symphysis and anterior sacroiliac joint. Studies investigating specific ligamentous contributions would aid in development of novel fixation techniques. The objective of this study is to determine the level of pelvic destabilization from progressive soft tissue disruptions associated with APC II injuries.

METHODS

Six fresh-frozen cadaveric pelvises were dissected of soft tissues, preserving joint capsules and ligaments. Each pelvis was secured in a double-leg stance and joint motion was tracked with the specimens cyclically loaded to 60% body weight. Each specimen was measured in the intact state and again following stepwise destabilization to an APC II injury model (PS: sectioned pubic symphysis, IPS JOINT: PS + ipsilateral anterior sacroiliac, sacrotuberous, sacrospinous ligaments sectioned, IPS LIGS: IPS JOINT + ipsilateral interosseous ligaments sectioned, IPS JOINT+CONT ASI: IPS LIGS + contralateral anterior sacroiliac ligament disruption).

RESULTS

Compared to the intact state, there was a statistically significant increase in movement in the IPS JOINT (ipsilateral 177%, p<0.001; contralateral 46%, p<0.005) and IPS JOINT+CONT ASI (ipsilateral 184%, p<0.002; and contralateral 62%, p<0.002) states bilaterally. No significant change was demonstrated in the PS or IPS LIGS state.

CONCLUSION

Disruption of ipsilateral ligamentous structures destabilized both sacroiliac joints. The interosseous and posterior sacroiliac ligaments provide the majority of stability of the sacroiliac joint and will likely benefit most from surgical stabilization.

LEVEL OF EVIDENCE

mechanism-based reasoning.

An In Vitro Biomechanical Analysis of Contralateral Sacroiliac Joint Motion Following Unilateral Sacroiliac Stabilization with and without Lumbosacral Fixation

STUDY DESIGN

Cadaveric biomechanics study.

PURPOSE

This study investigated the effects of unilateral sacroiliac joint (SIJ) fixation for fusion with/without L5-S1 fixation on contralateral SIJ range of motion (ROM).

OVERVIEW OF LITERATURE

SIJ fusion raises concerns that unilateral SIJ stabilization for fusion may increase contralateral SIJ mobility, leading to accelerated SIJ degeneration. Also, prior lumbosacral fixation may lead to accelerated SIJ degeneration, due to adjacent level effects. SIJ fixation biomechanics have been evaluated, showing a reduced-ROM, but SIJ fixation effects on contralateral nonfixated SIJ remain unknown.

METHODS

Seven human lumbopelvic spines were used, each affixed to six-degrees-of-freedom testing apparatus; 8.5-Nm pure unconstrained bending moments applied in flexion-extension, lateral bending, and axial rotation. The ROM of left and right SIJ was measured using a motion analysis system. Each specimen tested as (1) intact, (2) injury (left), (3) L5-S1 fixation, (4) unilateral stabilization (left), (5) unilateral stabilization+L5-S1 fixation, (6) bilateral stabilization, and (7) bilateral stabilization+L5-S1 fixation. Both left-sided iliosacral and posterior ligaments were cut for injury condition to model SIJ instability before surgery.

RESULTS

There were no statistical differences between fixated and contralateral nonfixated SIJ ROM following unilateral stabilization with/without L5-S1 fixation for all loading directions (p>0.930). Injured condition and L5-S1 fixation provided the largest motion increases across both joints; no significant differences were recorded between SIJs in any loading direction (p>0.850). Unilateral and bilateral stabilization with/without L5-S1 fixation reduced ROM compared with the injured condition for both SIJs, with bilateral stabilization providing maximum stability.

CONCLUSIONS

In the cadaveric model, unilateral SIJ stabilization with/without lumbosacral fixation did not lead to significant contralateral SIJ hypermobility; long-term changes and in vivo response may differ.

Comparative Analysis of Optoelectronic Accuracy in the Laboratory Setting Versus Clinical Operative Environment: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

The optoelectronic camera source and data interpolation process serve as the foundation for navigational integrity in robotic-assisted surgical platforms. The current systematic review serves to provide a basis for the numerical disparity observed when comparing the intrinsic accuracy of optoelectronic cameras versus accuracy in the laboratory setting and clinical operative environments.

METHODS

Review of the PubMed and Cochrane Library research databases was performed. The exhaustive literature compilation obtained was then vetted to reduce redundancies and categorized into topics of intrinsic accuracy, registration accuracy, musculoskeletal kinematic platforms, and clinical operative platforms.

RESULTS

A total of 465 references were vetted and 137 comprise the basis for the current analysis. Regardless of application, the common denominators affecting overall optoelectronic accuracy are intrinsic accuracy, registration accuracy, and application accuracy. Intrinsic accuracy equaled or was less than 0.1 mm translation and 0.1 degrees rotation per fiducial. Controlled laboratory platforms reported 0.1 to 0.5 mm translation and 0.1 to 1.0 degrees rotation per array. Accuracy in robotic-assisted spinal surgery reported 1.5 to 6.0 mm translation and 1.5 to 5.0 degrees rotation when comparing planned to final implant position.

CONCLUSIONS

Navigational integrity and maintenance of fidelity of optoelectronic data is the cornerstone of robotic-assisted spinal surgery. Transitioning from controlled laboratory to clinical operative environments requires an increased number of steps in the optoelectronic kinematic chain and error potential. Diligence in planning, fiducial positioning, system registration and intra-operative workflow have the potential to improve accuracy and decrease disparity between planned and final implant position.

Instrumentation of the sacroiliac joint with cylindrical threaded implants: A detailed finite element study of patient characteristics affecting fixation performance

The sacroiliac joint (SIJ) is a known pain generator that, in severe cases, may require surgical fixation to reduce intra-articular displacements and allow for arthrodesis. The objective of this computational study was to analyze how the number of implants affected SIJ stabilization with patient-specific characteristics such as the pelvic geometry and bone quality. Detailed finite element models were developed to account for three pelvises of differing anatomy. Each model was tested with a normal and low bone density (LD) under two types of loading: compression only and compression with flexion and extension moments. These models were instrumented with one to three cylindrical, threaded and fenestrated implants through a posterior oblique trajectory, requiring less muscle dissection than the more common lateral trajectory used with triangular implants. Compared with the noninstrumented pelvis, the change in range of motion (ROM) and stress distribution were used to characterize joint stabilization. Noninstrumented mobility ranged from 0.86 to 2.55 mm and from 1.37° to 6.11°. Across patient-specific characteristics, the ROM reduction with one implant varied from 3% to 21% for vertical and 15% to 47% for angular displacements. With two implants, the ROM reduction ranged from 12% to 41% for vertical and from 28% to 61% for angular displacements. Three implants, however, did not further improve the joint stability (14% to 42% for vertical and 32% to 63% for angular displacements). With respect to patient characteristics, an LD led to a decreased stabilization and a higher volume of stressed bone (>75% of yield stress). A better understanding of how patient characteristics affect the implant performance could help improve surgical planning of sacroiliac arthrodesis.

Accuracy of Robotic-Assisted Spinal Surgery-Comparison to TJR Robotics, da Vinci Robotics, and Optoelectronic Laboratory Robotics

BACKGROUND

The optoelectronic camera source and data interpolation serve as the foundation for navigational integrity in the robotic-assisted surgical platform. The objective of the current systematic review serves to provide a basis for the numerical disparity that exists when comparing the intrinsic accuracy of optoelectronic cameras: accuracy observed in the laboratory setting versus accuracy in the clinical operative environment. It is postulated that there exists a greater number of connections in the optoelectronic kinematic chain when analyzing the clinical operative environment to the laboratory setting. This increase in data interpolation, coupled with intraoperative workflow challenges, reduces the degree of accuracy based on surgical application and to that observed in controlled musculoskeletal kinematic laboratory investigations.

METHODS

Review of the PubMed and Cochrane Library research databases was performed. The exhaustive literature compilation obtained was then vetted to reduce redundancies and categorized into topics of intrinsic optoelectronic accuracy, registration accuracy, musculoskeletal kinematic platforms, and clinical operative platforms.

RESULTS

A total of 147 references make up the basis for the current analysis. Regardless of application, the common denominators affecting overall optoelectronic accuracy are intrinsic accuracy, registration accuracy, and application accuracy. Intrinsic accuracy of optoelectronic tracking equaled or was less than 0.1 mm of translation and 0.1° of rotation per fiducial. Controlled laboratory platforms reported 0.1 to 0.5 mm of translation and 0.1°-1.0° of rotation per array. There is a huge falloff in clinical applications: accuracy in robotic-assisted spinal surgery reported 1.5 to 6.0 mm of translation and 1.5° to 5.0° of rotation when comparing planned to final implant position. Total Joint Robotics and da Vinci urologic robotics computed accuracy, as predicted, lies between these two extremes-1.02 mm for da Vinci and 2 mm for MAKO.

CONCLUSIONS

Navigational integrity and maintenance of fidelity of optoelectronic data is the cornerstone of robotic-assisted spinal surgery. Transitioning from controlled laboratory to clinical operative environments requires an increased number of steps in the optoelectronic kinematic chain and error potential. Diligence in planning, fiducial positioning, system registration, and intraoperative workflow have the potential to improve accuracy and decrease disparity between planned and final implant position. The key determining factors limiting navigation resolution accuracy are highlighted by this Cochrane research analysis.

Biomechanical analysis of the number of implants for the immediate sacroiliac joint fixation

PURPOSE

The fusion of the sacroiliac joint (SIJ) is the last treatment option for chronic pain resulting from sacroiliitis. With the various implant systems available, there are different possible surgical strategies in terms of the type and number of implants and trajectories. The aim was to quantify the effect of the number of cylindrical threaded implants on SIJ stabilization.

METHODS

Six cadaveric pelvises were embedded in resin simulating a double-leg stance. Compression loads were applied to the sacral plate. The pelvises were tested non-instrumented and instrumented progressively with up to three cylindrical threaded implants (12-mm diameter, 60-mm length) with a posterior oblique trajectory. Vertical (VD) and angular (AD) displacements of the SIJ were measured locally using high-precision cameras and digital image correlation.

RESULTS

Compared to the non-instrumented initial state, instrumentation with one implant significantly decreased the VD (- 24% ± 15%, p = 0.028), while the AD decreased on average by - 9% (± 15%; p = 0.345). When compared to the one-implant configuration, adding a second implant further statistically decreased VD (- 10% ± 7%, p = 0.046) and AD (- 19% ± 15, p = 0.046). Adding a third implant did not lead to additional stabilization for VD nor AD (p > 0.5).

CONCLUSION

Compared to the non-instrumented initial state, the two-implant configuration reduces both vertical and angular displacements the most, while minimizing the number of implants.

Sacroiliac joint dysfunction: pathophysiology, diagnosis, and treatment

PURPOSE

To review the anatomy and function of the sacroiliac joint (SIJ), as well as the pathophysiology, clinical presentation, diagnostic criteria, and treatment options for SIJ dysfunction.

METHODS

The SIJ serves an extremely crucial function in mobility, stability, and resistance against shear forces. Joint mobility becomes increasingly limited with age-related cartilaginous changes that begin in puberty and continue throughout life. Pain can also be localized to the SIJ itself, known as SIJ dysfunction. A literature review was performed on the anatomy, etiology, risk factors, diagnostic modalities, and treatment options for SIJ dysfunction.

RESULTS

SIJ dysfunction is an under-recognized source of low back pain. Dysfunction can result from various clinical conditions, as well as abnormal motion or malalignment of the joint. Diagnosis and evaluation of SIJ dysfunction are difficult, with use of physical maneuvers and image-guided anesthetic injection. Non-operative treatment options are considered first-line due to high surgical complication rates. Such options include conservative management, radiofrequency treatment, nerve blocks, and articular injections. Surgical management involves open and percutaneous approaches.

CONCLUSION

With the aging nature of the population, SIJ dysfunction has emerged as an extremely prevalent issue. Current research into the pathophysiology and risk factors of SIJ dysfunction is extremely important for planning preventative and therapeutic strategies. Various treatment options exist including conservative management, radiofrequency, nerve blocks, intra-articular or peri-articular injections, and surgical fixation. Improved diagnostic methods in clinical practice are thus critical to properly identify patients suffering from SIJ dysfunction, plan early intervention, and hasten return to function.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Sacroiliac joint stabilization using implants provide better fixation in females compared to males: a finite element analysis

PURPOSE

This study's objective was to assess biomechanical parameters across fused and contralateral sacroiliac joints (SIJs) and implants during all spinal motions for both sexes. Various SIJ implant devices on the market are used in minimally invasive surgeries. These implants are placed across the joint using different surgical approaches. The biomechanical effects of fusion surgical techniques in males and females have not been studied.

METHODS

The validated finite element models of a male, and a female spine-pelvis-femur were unilaterally instrumented across the SIJ using three screws for two SIJ implants, half threaded and fully threaded screws placed laterally and posteriorly to the joint, respectively.

RESULTS

Motion and peak stress data at the SIJs showed that the female model exhibited lower stresses and higher reduction in motion at the contralateral SIJ in all motions than the male model predictions with 84% and 71% reductions in motion and stresses across the SIJ.

CONCLUSION

Implants exhibited higher stresses in the female model compared to the male model. However, chances of SIJ implant failure in the female patients are still minimal, based on the calculated factor of safety which is still very high. Both lateral and posterior surgical approaches were effective in both sexes; however, the lateral approach may provide a better biomechanical response, especially for females. Moreover, implant design characteristics did not make a difference in the implants' biomechanical performance. SIJ stabilization was primarily provided by the implants which were the farthest from the sacrum rotation center.

Systematic review of sacroiliac joint motion and the effect of screw fixation

BACKGROUND

Pelvic injuries that disrupt the sacroiliac joints often require surgical intervention to restore stability. Quantitative characterization of sacroiliac motion in response to physiologic loading provides important metrics of adequate fixation in the evaluation of newly emerged fixation techniques. The objective of this study was to systematically review and evaluate biomechanical evidence on the motion of the sacroiliac joint in its normal, destabilized, and stabilized states.

METHODS

We searched the PubMed database for studies available until June 2020 using keywords: sacroiliac, biomechanic*, and fixation. Publications of any in vivo or in vitro biomechanical study that included measurements of the range of motion at the sacroiliac joint were considered.

FINDINGS

We identified and screened 176 total records, and 13 articles of them met inclusion criteria and were used in this review. The average sacroiliac joint range of motion of the intact pelvis was 1.88° in flexion/extension, 0.85° in lateral bending, 1.26° in axial rotation. Of the 13 studies, four reported sacroiliac motion from a destabilized state, while seven reported the motion after stabilization. A forest plot of the stabilized data set in flexion/extension showed that while the heterogeneity was poor, the weighted effect size of the changes from the intact state to the stabilized state was 0.0%.

INTERPRETATION

Quantitative evidence on sacroiliac joint motion relating to pelvic injuries or fixation is limited. Our results indicate that the pooled intact range of motion from the literature may serve as a viable reference to quantify the effectiveness of new stabilization techniques.

LEVEL OF EVIDENCE

Level V, systematic review.

STUDY TYPE

Therapeutic- investigating the results of a treatment.

Finite element analysis of load transition on sacroiliac joint during bipedal walking

The sacroiliac joint (SIJ) is burdened with variant loads. However, no methods have allowed to measure objectively how the SIJ deforms during bipedal walking. In this study, in-vivo walking conditions were replicated in a kinematic model combining the finite element method with 3D walking analysis data divided into five phases in order to visualize the load transition on the SIJ and clarify the role of the SIJ. Both models with and without inclusion of the SIJ were investigated. In models with bilateral SIJs, the displacement differed greatly between the sacrum and both hip bones on the SIJ as the boundary. The movements of the sacrum involved a nutation movement in the stance phase and a counter-nutation in the swing phase relative to the ilium. In models without SIJs, the displacement of the pelvis and loads of pelvic ligaments decreased, and the equivalent stress of the SIJs increased compared to the model with SIJs. The walking loads cause distortion of the entire pelvis, and stress concentration at the SIJ are seen due to the morphology of the pelvic ring. However, the SIJs help dissipate the resulting stresses, and the surrounding ligaments are likewise involved in load transmission.