Hydroxyapatite-Coated Screws Versus Titanium Triangular Dowels for Sacroiliac Joint Fusion: Results From a Nonrandomized Prospective Outcome Study.

OBJECTIVE: This is a single-surgeon series that prospectively evaluates the results of sacroiliac joint (SIJ) fusion for patients with SIJ dysfunction using hydroxyapatite-coated screws (HACSs) compared with titanium triangular dowels (TTDs). METHODS: A total of 113 patients underwent SIJ fusion surgery between 2013 and 2018 at the University Hospital Llandough to treat symptomatic SIJ dysfunction not responding to nonoperative measures. Of the 113 patients, 40 were treated with HACSs and 73 with TTDs. Patient-reported outcomes measures (PROMs) were collected preoperatively and at 12 months postoperatively, including the 36-item short-form health survey, Oswestry disability index, EuroQol-5D-5L, and Majeed pelvic score. Patients with ongoing symptoms were followed up beyond the study period. RESULTS: Of the 113 patients, 33 completed follow-up in the HACS group compared with 61 in the TTD group. Both groups had comparable preoperative PROMs; however, the postoperative PROMs were significantly better in the TTD group. Additionally, 21 patients (63%) in the HACS group had radiological evidence of screw lysis compared with 5 patients (9%) in the TTD group. A subgroup analysis revealed less significant improvement in PROMs for patients with screw lysis compared with those without. Four patients were offered further revision surgery. CONCLUSIONS: Minimally invasive SIJ fusion has been shown to have good clinical outcomes for select patients. However, our experience shows that HACSs are associated with a high rate of screw lysis and poorer patient outcomes compared with TTDs. Therefore, we recommend the use of TTDs instead of HACSs for SIJ fusion surgery.

Hip-sacroiliac joint-spine syndrome in total hip arthroplasty patients.

This study is designed to compare the extent of sacroiliac joint (SIJ) degeneration at total hip arthroplasty (THA) for two pathologies: osteoarthritis of the hip (OA) and osteonecrosis of the femoral head (ON). We also assessed the prevalence of SIJ degeneration in patients with lumbar spondylolisthesis or degenerative scoliosis. A total of 138 hips from 138 patients (69 OA and 69 ON) were assessed in this study, including 66 hips affected by OA secondary to developmental dysplasia of the hip. The degenerative changes in the SIJ and lumbar spine were evaluated prior to THA using radiographs and computed tomography (CT) scans, showing 9 instances of spondylolisthesis and 38 of degenerative scoliosis. The OA group exhibited longer duration from onset to surgery than the ON group. The OA group also included more cases with significant pelvic obliquity (3 degrees or more) and with significant increases in SIJ sclerosis and irregularities. Patients with lumbar spondylolisthesis or degenerative scoliosis were significantly more likely to have SIJ irregularities. The prevalence of SIJ degeneration was higher in cases of THA for OA than for ON. This study also suggests the possibility of Hip-SIJ-Spine syndrome in THA patients with OA.

The Sacroiliac Joint: A Current State-of-the-Art Review.

¼ The sacroiliac joint (SIJ) is a common cause of low back pain and should be included in the differential diagnosis.¼ Nonoperative treatment of sacroiliac pain is always the first line of therapy; however, when it is unsuccessful and becomes chronic, then recurrent nonoperative treatment becomes expensive.¼ Surgical treatment is cost-effective in appropriately selected patients. High-quality clinical trials have demonstrated statistically and clinically significant improvement compared with nonsurgical management in appropriately selected patients.¼ Spinal fusion to the sacrum increases degeneration of the SIJ and frequency of SIJ pain.

Effect of revision sacroiliac joint fusion on unresolved pain and disability: a retrospective cohort study.

PURPOSE: The sacroiliac (SI) joint is recognized as a source of low back pain in 15-30% of patients. Though randomized controlled trials have shown clinical improvement following SI joint fusion in 83.1% of patients, revision rates of 2.9% within 2 years have been reported. There is a paucity of literature reviewing this small yet significant population of patients requiring revision surgery. METHODS: Following IRB approval, retrospective review of patients, who underwent a revision SI joint fusion from 2009 to 2021 was completed. Patient-reported outcomes were measured before and at each clinic visit after surgery with visual analoge scale (VAS) for back pain and Oswestry Disability Index (ODI). Patient characteristics (chronic opiate use and prior lumbar fusion) and surgical factors (operative approach, type/number of implants and use of bone graft) were recorded. Patient-reported outcomes were evaluated with Paired t and Wilcoxon signed rank tests. Univariate and multivariate logistic regression determined if patients met the minimally clinical important differences (MCID) for VAS-back pain and ODI scores at 1 year. RESULTS: Fifty-two patients (77% female) with an average age of 49.1 (SD ± 11.1) years met inclusion criteria. Forty-four had single sided revisions and eight bilateral revisions. At 1 year follow-up there was no significant improvement in VAS-Back (p = 0.06) or ODI (p = 0.06). Patients with chronic opioid use were 8.5 times less likely to achieve the MDC for ODI scores (OR 0.118, p = 0.029). There was no difference in outcomes when comparing the different surgical approaches (p = 0.41). CONCLUSION: Our study demonstrates patients undergoing revision surgery have moderate improvement in low back pain, however, few have complete resolution of their symptoms. Specific patient factors, such as chronic opiate use and female sex may decrease the expected improvement in patient-reported outcomes following surgery. Failure to obtain relief may be due to incorrect indications, lack of biologic fusion and/or presence of co-pathologies. Further clinical examination and consistent long-term follow-up, clarify the role revision surgery plays in long-term patient outcomes.

Minimally invasive sacroiliac joint fusion using triangular titanium implants versus nonsurgical management for sacroiliac joint dysfunction: a systematic review and meta-analysis.

BACKGROUND: Minimally invasive sacroiliac joint (MISIJ) fusion is a surgical option to relieve SIJ pain. The aim of this systematic review and meta-analysis was to compare MISIJ fusion with triangular titanium implants (TTI) to nonoperative management of SIJ dysfunction. METHODS: We searched MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials. We included prospective clinical trials that compared MISIJ fusion to nonoperative management in individuals with chronic low back pain attributed to SIJ dysfunction. We evaluated pain on visual analogue scale, Oswestry Disability Index (ODI) score, health-related quality of life (HRQoL) using the 36-Item Short Form Health Survey (SF-36) physical component (PCS) and mental component summary (MCS) scores, patient satisfaction, and adverse events. RESULTS: A total of 8 articles representing 3 trials that enrolled 423 participants were deemed eligible. There was a significant reduction in pain score with MISIJ fusion compared with nonoperative management (standardized mean difference [SMD] -1.71, 95% confidence interval [CI] -2.03 to -1.39). Similarly, ODI scores (SMD -1.03, 95% CI -1.24 to -0.81), SF-36 PCS scores (SMD 1.01, 95% CI 0.83 to 1.19), SF-36 MCS scores (SMD 0.72, 95% CI 0.54 to 0.9), and patient satisfaction (odds ratio 6.87, 95% CI 3.73 to 12.64) were significantly improved with MISIJ fusion. No significant difference was found between the 2 groups with respect to adverse events (SMD -0.03, 95% CI -0.28 to 0.23). CONCLUSION: Our analysis showed that MISIJ fusion with TTI shows a clinically important and statistically significant improvement in pain, disability score, HRQoL, and patient satisfaction with a similar adverse event profile to nonoperative management in patients with chronic low back pain attributed to SIJ dysfunction.

The Effects of Abdominal Obesity and Sagittal Imbalance on Sacroiliac Joint Pain After Lumbar Fusion.

BACKGROUND: Postoperative sacroiliac joint pain (SIJP) is a common manifestation of failed back surgery syndrome after a posterior lumbar interbody fusion (PLIF). However, there is currently no consensus on the risk factors for SIJP after PLIF. OBJECTIVES: We explored the effects of abdominal obesity and sagittal imbalance on SIJP after PLIF. STUDY DESIGN: This is a prospective observational cohort study. SETTING: This study occurred at the Department of Spinal Surgery at a hospital affiliated with a medical university. METHODS: A total of 401 patients who underwent PLIF from June 2018 to June 2021 were enrolled in this study. 36 patients experienced postoperative SIJP. In contrast, a matched group comprised 72 non-SIJP patients. We used 1:2 propensity score matching to compare obesity features and sagittal spine parameters in the 2 groups. Inflammatory cytokines and visual analog scale (VAS) scores were measured in the SIJP group. RESULTS: A total of 36 patients (8.98%) experienced SIJP during the follow-up. Compared with the non-SIJP group, patients with postoperative SIJP had a higher body mass index (BMI), greater abdominal obesity, a higher incidence of pelvic incidence-lumbar lordosis greater than 10°, and a higher incidence of a sagittal vertical axis greater than 5 cm (P < 0.05). Receiver operating characteristic curve analysis showed that the area under the curve for waist circumference was greater than that for BMI (0.762 vs. 0.650, P = 0.049). Logistic regression analysis revealed that the risk factors for SIJP were abdominal obesity, a pelvic incidence-lumbar lordosis of greater than 10°, and a sagittal vertical axis greater than 5 cm (P < 0.05). In patients with SIJP, interleukin 6, tumor necrosis factor-α, and VAS scores were higher in the abdominal obesity group than in the non-abdominal obesity group (P < 0.05). LIMITATIONS: There was no uniform diagnosis of SIJP, so the incidence rate of SIJP might not be accurate. CONCLUSIONS: The significant predictors of SIJP were abdominal obesity and sagittal imbalance. Patients with abdominal obesity showed higher levels of inflammatory markers and pain intensity. More attention should be paid to body shape and the angle of correction of lumbar lordosis before lumbar surgery.

A systematic review and update on diagnosis and treatment of new onset sacroiliac joint dysfunction after lumbar fusion.

BACKGROUND: Sacroiliac joint dysfunction (SIJD) after lumbar/lumbosacral fusion has become increasingly recognized as the utilization of lumbar fusion has grown. Despite the significant morbidity associated with this condition, uncertainty regarding its diagnosis and treatment remains. We aim to update the current knowledge of the etiology, diagnosis, and treatment of post-lumbar surgery SIJD. METHODS: PRISMA guidelines were used to search the PubMed/Medline, Web of Science, Cochrane Reviews, Embase, and OVID databases for literature published in the last 10 years. The ROBIS tool was utilized for risk of bias assessment. Statistical analyses were performed using the R foundation. A Fisher's exact test was performed to determine the risk of SIJD based on operative technique, gender, and symptom onset timeline. Odds ratios were reported with 95% confidence intervals. A p-value [Formula: see text] 0.05 was considered statistically significant. RESULTS: Seventeen publications were included. The incidence of new onset SIJD was 7.0%. The mean age was 56 years, and the follow-up length was 30 months. SIJD was more common with fixed lumbar fusion vs floating fusion (OR = 1.48 [0.92, 2.37], p = 0.083), fusion of [Formula: see text] 3 segments (p < 0.05), and male gender increased incidence of SIJD (OR = 1.93 [1.27, 2.98], p = 0.001). Intra-articular injection decreased the Visual Analogue Scale (VAS) score by 75%, while radiofrequency ablation (RFA) reduced the score by 90%. An open approach resulted in a 13% reduction in VAS score versus 68 and 29% for SIJ fixation using the iFuse and DIANA approaches, respectively. CONCLUSIONS: Lumbar fusion predisposes patients to SIJD, likely through manipulation of the SIJ's biomechanics. Definitive diagnosis of SIJD remains multifaceted and a newer modality such as SPECT/CT may find a future role. When conservative measures are ineffective, RFA and SIJ fixation using the iFuse System yield the greatest improvement VAS and ODI.

Comparison of the operation safety and biomechanical stability of sacral alar-iliac vs. sacroiliac screws in the fixation of sacroiliac joint in simulated models of low bone density.

BACKGROUND: Sacral alar-iliac screws (SAISs) have been used for sacroiliac joint and are superiority to traditional sacroiliac screws (SISs) in patients with low bone density. The aim of this study was to investigate the operation safety and biomechanical stability of the SIS, transsacral-transiliac screw (TSTIS), S1AIS and S2AIS in the treatment of sacroiliac joint in simulated models of low bone density. METHODS: CT data from 80 normal pelvic structures were employed to measure the anatomical parameters, including the safety zones of the S1AIS and S2AIS at the insertion point and the trajectory lengths of the SIS, TSTIS, S1AIS and S2AIS. Sixteen synthetic pelvises with simulated osteoporotic bone structure were used to simulate type C Tile lesions and divided into 4 groups with an anterior plate and posterior fixation using one of the following: 1) one SIS on each side, 2) one TSTIS fixing both sides, 3) one S1AIS on each side, or 4) one S2AIS on each side. The stiffness and maximum load of the specimens were analyzed using a biomechanical machine under vertical loading. RESULTS: The safety zone of S1AIS was larger than that of S2AIS (p < 0.05). The TSTIS had the largest trajectory length, followed by the S1AIS and S2AIS, and the SIS had the smallest trajectory length (p < 0.05). However, the lengths of the TSTIS (26.1 ± 1.7 mm) and SIS (27.8 ± 1.8 mm) trajectories on the short side (the iliac side) were smaller than those of S1AIS (40.4 ± 3.8 mm) and S2AIS (39.1 ± 3.8 mm), thus indicating significant differences (p < 0.05). The stiffness and maximum load of S1AIS and S2AIS were similar and the greatest, followed by TSTIS and SIS (p < 0.05). CONCLUSION: The stability of S1AIS and S2AIS is similar, both stronger than that of SIS and TSTIS, which have shorter lengths of the screw trajectories on the ilium side. However, the safety zone of S2AIS at the insertion point is smaller than that of S1AIS. Therefore, considering both safety and stability, S1AIS is the preferred choice for fixation of sacroiliac joint dislocation in simulated models of low bone density.

Cooled radiofrequency ablation versus standard medical management for chronic sacroiliac joint pain: a multicenter, randomized comparative effectiveness study.

INTRODUCTION: Low back pain is the leading cause of disability worldwide, with sacroiliac joint pain comprising up to 30% of cases of axial lower back pain. Conservative therapies provide only modest relief. Although placebo-controlled trials show efficacy for sacral lateral branch cooled radiofrequency ablation, there are no comparative effectiveness studies. METHODS: In this randomized, multicenter comparative effectiveness study, 210 patients with clinically suspected sacroiliac joint pain who obtained short-term benefit from diagnostic sacroiliac joint injections and prognostic lateral branch blocks were randomly assigned to receive cooled radiofrequency ablation of the L5 dorsal ramus and S1-S3 lateral branches or standard medical management consisting of pharmacotherapy, injections and integrative therapies. The primary outcome measure was mean reduction in low back pain score on a 0-10 Numeric Rating Scale at 3 months. Secondary outcomes included measures of quality of life and function. RESULTS: 3 months post-treatment, the mean Numeric Rating Scale pain score for the cooled radiofrequency ablation group was 3.8±2.4 (mean reduction 2.5±2.5) compared with 5.9±1.7 (mean reduction 0.4±1.7) in the standard medical management group (p<0.0001). 52.3% of subjects in the cooled radiofrequency ablation group experienced >2 points or 30% pain relief and were deemed responders versus 4.3% of standard medical management patients (p<0.0001). Comparable improvements favoring cooled radiofrequency ablation were noted in Oswestry Disability Index score (mean 29.7±15.2 vs 41.5+13.6; p<0.0001) and quality of life (mean EuroQoL-5 score 0.68±0.22 vs 0.47±0.29; p<0.0001). CONCLUSIONS: In patients with sacroiliac joint pain, cooled radiofrequency ablation provided statistically superior improvements across the spectrum of patient outcomes compared with standard medical management. TRIAL REGISTRATION NUMBER: NCT03601949.

Return to Duty in Military Service Members Following Minimally Invasive Sacroiliac Joint Fusion.

INTRODUCTION: As the utilization of minimally invasive sacroiliac joint fusion (SIJF) continues to expand, a better understanding of postoperative outcomes is needed, particularly in young and active individuals. The purpose of this study is to assess the outcomes of this procedure in an active duty military population by examining return-to-duty (RTD) rates. MATERIALS AND METHODS: A retrospective review of the electronic medical record from a tertiary military medical center was performed for active duty service members undergoing SIJF from January 2013 to January 2019. The primary outcome measured was RTD at 6 months, with active duty status at 1 year, last follow-up, and revision surgery as secondary outcomes. Demographic and surgical variables recorded included patient age, gender, military rank, utilization of navigation, and implant type. RESULTS: Sixteen service members met the inclusion criteria, with a mean age of 40.5 ± 6.7 years. The mean follow-up after surgery was 24 ± 15 months. Patients received either cylindrical (n = 6) or triangular (n = 10) implants placed with (n = 6) or without (n = 10) navigation. Within 6 months of surgery, 56% of patients were able to RTD. Patients undergoing navigation-assisted procedures were significantly more likely to RTD at 6 months (100% vs. 30%, P = .011) compared to those undergoing surgery performed with orthogonal fluoroscopic imaging. Compared to those with cylindrical implants, patients with triangular implants were also more likely to RTD at 6 months (80% vs. 17%, P = .035). CONCLUSIONS: Following SIJF, a small majority of service members were able to return to full active duty status by 6 months. Further studies are needed to assess the potential benefits of navigation and implant selection, as our retrospective review noted differences in outcomes based on these variables.

Biomechanical Comparison of Double 2.3-mm Headless Cannulated Self-Compression Screws and Single 3.5-mm Cortical Screw in Lag Fashion in a Canine Sacroiliac Luxation Model: A Small Dog Cadaveric Study.

OBJECTIVE: The aim of this study was to evaluate the feasibility of safe positioning of double 2.3-mm headless cannulated self-compression screws (HCS) in a small dog cadaveric sacroiliac luxation model and to compare the static rotational biomechanical properties of fixation repaired using two different screw systems with a minimally invasive osteosynthesis technique: double 2.3-mm HCS and a single 3.5-mm standard cortical screw placed in a lag fashion. STUDY DESIGN: A unilateral small dog sacroiliac luxation model was stabilized using double 2.3-mm HCS (n = 11) or a single 3.5-mm cortical screw (n = 11). Radiographic and computed tomography (CT) imaging analyses and biomechanical testing of rotational force on the sacroiliac joint of both fixations were performed. The maximum load at failure and failure modes of each fixation were recorded and compared. RESULTS: Fluoroscopically guided percutaneous application of double HCS was safe in a unilateral sacroiliac luxation model in small dogs without violation of the vertebral and ventral sacral foramen. Furthermore, resistance to rotational force applied on fixation of the sacroiliac joint repaired with double 2.3-mm HCS estimated by maximum failure load was significantly higher than that of a single 3.5-mm cortical screw (p < 0.001). CONCLUSION: Although this was an experimental cadaveric study, based on our results, the use of smaller double HCS may be beneficial as an alternative to the conventional single lag screw for stabilization of sacroiliac luxation in small dogs.

Comparison of sacroiliac screw techniques for unstable sacroiliac joint disruptions: a finite element model analysis.

Vertically unstable pelvic injuries associated with sacroiliac disruption are challenging. Although percutaneous iliosacral fixation using two screws at S1 vertebral body has been shown beneficial, the use of two transiliac screws at S1 has been proposed to increase the fixation strength of the construct. In the herein study, the finite element method (FEM) was performed to analyse the biomechanical behaviour of five different constructions using iliosacral screws only, transiliac screws only, and combining an iliosacral and a transiliac screw. A vertically unstable AO 61C1.2 type pelvic injury was produced for the evaluation of the posterior pelvic displacement and implant stress, and the anterior implant stress using FEM. The symphysis pubis was fixed with a 3.5-mm reconstruction plate in all cases. The model was axially loaded with 800N applied in the centre of S1 body, perpendicular to the ground (Y-axis), simulating the bipodal stance moment. There was a statistically significant reduction in both posterior displacement and implant stresses in the groups fixed with at least one transiliac screw compared to the groups fixed with iliosacral screws. In our FEM study, the construct using two transiliac screws in S1 is biomechanically superior for stabilizing the sacroiliac joint in vertically unstable pelvic ring injuries compared to the other configurations. Lateral displacement, posterior displacement, and von Mises stress were reduced with this construct. A good option can be the use of one iliosacral screw and one transiliac screw in S1.

Diagnostic accuracy of MRI for detection of occult instability of type I anterior to posterior pelvic injuries.

Type I Young and Burgess anterior posterior compression (APC) pelvic injuries have been classically managed non operatively due to theoretical integrity of sacroiliac joint ligaments (SIJL), though examination under anesthesia (EUA) has been proven occult mechanical instability in up to 50% of these injuries.  We sought to determine the diagnostic accuracy of magnetic resonance (MRI) for detection of occult instability on APC-I injuries when compared to EUA. METHODS: Diagnostic test study of prospectively recruited patients admitted with APC-I pelvic injuries between 2015 and 2022. All patients consented to participate in this study were subjected to MRI and EUA. The evaluators of each of these tests were blinded.  On MRI evaluation, SIJL were considered compromised when unilateral injury to anterior SIJL was visualized in three or more consecutive images or in bilateral injuries, when injury to the anterior SIJL in two or more consecutive images on each side was observed. Positive EUA was considered a symphyseal diastasis over 25 mm on stress fluoroscopy. Demographic data was collected as recruited and sensitivity, specificity, accuracy, and positive and negative predictive values were calculated. Confidence interval was set at 95%. EUA was considered the gold standard in statistical analysis. RESULTS: A total of 32 patients mean aged 36 (24-61) years were included. Mean symphyseal diastasis at admission was 17.58 (11 - 25) mm. The median time from injury to EUA was 5 (0-21) days. Positive EUA was observed on 20 patients and 25 patients  presented compromised SIJL. MRI presented a sensitivity of 95% (75.13% - 99.87%), specificity of 50% (21.09% - 78.91%), positive-predictive value of 73% (60.61% to 82.93%), negative-predictive value of 87% (48.66% - 98.08%). CONCLUSION: Injury to SIJL on MRI presented an accuracy of 77% (58.29% - 89.64%) for the detection of occult pelvic instability on EUA.

Clinical study of modified INFIX combined with sacroiliac joint screws for pelvic instable injuries.

OBJECTIVE: The INFIX technique is becoming one of the most commonly performed surgical procedures for anterior pelvic ring instability injuries. The purpose of this article is to compare the clinical outcomes of modified anterior subcutaneous internal fixation (M-INFIX) with conventional anterior subcutaneous internal fixation (C-INFIX) for anterior pelvic ring instability injuries. PATIENTS AND METHODS: A retrospective analysis of 36 cases of unstable pelvic injuries treated operatively at our institution, 20 of which were treated with C-INFIX and 16 with M-INFIX. Data collected included age, gender, ISS score, fracture typing, operative time, operative bleeding, postoperative complications, fracture healing time, Matta score, Majeed score, and follow-up time. Statistical sub-folding of each variable between the two groups was performed. RESULTS: There was no statistical difference between the C-INFIX and M-INFIX groups in terms of age, gender, ISS (Injury Severity Score), follow-up time, fracture typing, fracture healing time, and Majeed score (P > 0.05). the M-INFIX had a significantly lower incidence of postoperative complications than the C-INFIX group, especially in the incidence of Lateral femoral cutaneous nerve (LFCN) injury (P < 0.05). In contrast, the M-INFIX group had statistically higher operative time, intraoperative bleeding, and Matta score than the C-INFIX group (P < 0.05). CONCLUSION: This study was based on a modified application of the surgical experience with C-INFIX and showed better clinical outcomes in terms of complication rates and quality of repositioning than the conventional surgical approach. These findings indicate that further analytical studies of this study would be valuable.

Anatomy of the sacroiliac joint with relation to the lumbosacral trunk: Is there sufficient space for a two-hole plate?

Dislocations of the sacroiliac joint (SIJ) are treated with iliosacral screws or anterior plating. The study aimed to investigate the course of the lumbosacral trunk with reference to SIJ and determine whether is there sufficient space for two screws through the sacrum while performing anterior plating. Sixty patients, who underwent an MRI of the lumbar spine were included in our study. The three transverse LT-SIJ distances were measured at the three points (A, B, and C). We also analyzed 60 CT pelvic scans at points A, B, and C in order to measure: the vertebral canal-to-SIJ distance, the sacrum's pelvic-to-dorsal surface sagittal distance, and the median plane-to-SIJ angle. The mean transverse LT-SIJ distances at points A, B, and C were 20.0 ± 3.05 mm, 17.9 ± 3.20 mm, and 12.3 ± 2.49 mm, respectively. Based on CT analyses, the vertebral canal-to-SIJ distances were 30.5 ± 7.65 mm at point A, 21.4 ± 5.05 mm at point B and 15.7 ± 6.05 mm at point C. The sacrum's pelvic-to-dorsal surface sagittal distances reached values: 35.1 ± 11.62 mm at point A, 52.5 ± 10.58 mm at point B, and 57.5 ± 7.79 mm at point C. The median plane-to-SIJ angles measured 31.4 ± 4.82 degrees at point A, 26.6 ± 3.77 degrees at point B and 21.3 ± 3.25 mm at point C. Proximally, the safe zone for applying an anterior plate of SIJ is 20.0 mm. Since both the safe zone and safe corridor taper distally, surgeons may securely use one screw of gradually increased length towards the distal direction of SIJ, with inclination of 30 degrees in relation to the median plane of the lesser pelvis.

Bilateral Sacroiliac Joint Dislocation, Discussion and Surgical Strategies: A Case Report.

CASE: A 16-year-old male patient presented with isolated bilateral sacroiliac (SI) joint dislocation. In this report, we discuss the presentation and focus on strategies for operative reduction and fixation for this rare injury. CONCLUSION: In conclusion, we present a case of a bilateral ligamentous SI joint dislocation in an adolescent. The patient was reduced in the supine position with a sacral bump and bilateral traction with direct and indirect reduction aids inserted through a lateral window. Bilateral SI screws stabilized the pelvis, facilitating uncomplicated healing.

The effects of topping-off instrumentation on biomechanics of sacroiliac joint after lumbosacral fusion.

BACKGROUND: Lumbar/lumbosacral fusion supplemented with topping-off devices has been proposed with the aim of avoiding adjacent segment degeneration proximal to the fusion construct. However, it remains unclear how the biomechanics of the sacroiliac joint (SIJ) are altered after topping-off surgery. The objective of this study was to investigate the biomechanical effects of topping-off instrumentation on SIJ after lumbosacral fusion. METHODS: The validated finite element model of an intact lumbar spine-pelvis segment was modified to simulate L5-S1 interbody fusion fixed with a pedicle screw system. An interspinous spacer, Device for Intervertebral Assisted Motion (DIAM), was used as a topping-off device and placed between interspinous processes of the L4 and L5 segments. Range of motion (ROM), von-Mises stress distribution, and ligament strain at SIJ were compared between fusion (without DIAM) and topping-off (fusion with DIAM) models under moments of four physiological motions. RESULTS: ROM at the left and right SIJs in the topping-off model was higher by 26.9% and 27.5% in flexion, 16.8% and 16.1% in extension, 18.8% and 15.8% in lateral bending, and 3.7% and 7.4% in axial rotation, respectively, compared to those in the fusion model. The predicted stress and strain data showed that under all physiological loads, the topping-off model exhibited higher stress and ligament strain at the SIJs than the fusion model. CONCLUSIONS: Motion, stress, and ligament strain at SIJ increase when supplementing lumbosacral fusion with topping-off devices, suggesting that topping-off surgery may be associated with higher risks of SIJ degeneration and pain than fusion alone.

Halo Formation and Resolution at 7-Year Follow-Up After Sacroiliac Joint Fusion Revision: A Case Report.

CASE: A 49-year-old woman presented with low back pain after a work-related injury. She failed 5 months of conservative management and subsequently underwent minimally invasive (MI) left sacroiliac joint (SIJ) fusion with 3 triangular titanium implants. Four months postoperatively, she developed recurrence of symptoms and radiographic halo phenomenon about the implants. The cephalad and caudal implants were replaced with threaded self-tapping implants, and the middle implant was unable to be removed. At 7-year follow-up, the halo phenomenon had resolved. CONCLUSION: This is an unusual case of radiographic halo phenomenon formation after MI SIJ fusion and halo resolution after subsequent revision.