Iliosacral Screw Research Articles

Effectiveness of closed reduction and percutaneous fixation of isolated sacral fractures. Functional outcomes and sagittal alignment after 3.6 years in 20 patients

BackgroundDisplaced U- or H-shaped sacral fractures (Roy-Camille Grade II or III) are treated at our institution by early transcondylar traction and manual countertraction, hyperlordosis induced by a pad positioned under the lumbo-sacral junction, and percutaneous ilio-sacral screw fixation. The objective of this study was to evaluate the outcome of this technique used in a level 1 trauma centre.Hypothesis Our early reduction technique provides anatomical reduction of U- or H-shaped sacral fractures by correcting the sagittal malalignment due to the intra-sacral kyphosis, thereby obviating the need for decompression laminectomy and improving neurological outcomes. Material and methodsWe retrospectively evaluated 20 patients treated for U- or H-shaped sacral fractures using our original reduction technique followed by percutaneous fixation only. Mean follow-up was 42.4 months. Mean displacement of the S1 posterior wall was measured on computed tomography scans obtained before and after surgery. Pelvic incidence (PI) and measured lumbar lordosis (LLm) were evaluated on standard radiographs before surgery and on stereoradiographs after surgery. Expected lumbar lordosis (LLe) was computed as LLe=PI+9°. A 25% or greater difference between LLe and LLm defined lumbo-pelvic mismatch. At last follow-up, functional outcomes were assessed based on the Majeed score and the Iowa Pelvic Score (IPS), and a neurological examination was performed. ResultsMean S1 posterior wall displacement in the sagittal and axial planes was 64% and 64.8%, respectively, before surgery versus 5.6% and 15.2%, respectively, after surgery. At last follow-up, LLm was 63.5° and the LLe-LLm difference was 11.2%; only 3 (15%) patients had lumbo-pelvic mismatch at last follow-up. The mean Majeed score and IPS values were 86.6 and 79, respectively, and lumbo-pelvic mismatch correlated significantly with a worse functional outcome defined as a Majeed score below 75 (p=0.0087). At last follow-up, the neurological dysfunctions were improved in 90% of patients, and 70% of patients had achieved a full neurological recovery. Discussion/ConclusionGiven these encouraging findings, we advocate early reduction and percutaneous fixation of U- or H-shaped sacral fractures. Although technically demanding, this method restores the normal pelvic parameters and improves neurological function. Level of evidenceIV, retrospective observational study.

Fragility fractures of the pelvis

Fragility fractures of the pelvis are increasing in frequency. In most cases patients suffer aminor injury, have intense pain in the pelvic region and impaired mobility. The new fragility fractures of the pelvis (FFP) classification distinguishes between four types with increasing instability. The FFP typesI and II are treated conservatively. For FFP typesIII and IV and typeII with unsuccessful conservative treatment, minimally invasive stabilizing techniques are recommended. Both the posterior and anterior pelvic ring must be stabilized. Alternative techniques for dorsal stabilization are iliosacral screw and transsacral bar osteosynthesis, transiliac internal fixator and lumbopelvic fixation. External fixation, retrograde transpubic screw fixation, anterior internal fixation and plate and screw osteosynthesis are alternatives for the anterior pelvic ring. Treatment of fragility fractures of the pelvis should be carried out as part of an orthogeriatric co-management.

Two Transiliac-Transsacral Screws in a Single Sacral Level: Surgical Technique and Patient Outcomes

Percutaneous fixation of posterior pelvic injuries is increasingly common. Use of transiliac-transsacral (TI-TS) screws can provide improved fixation, relative to standard iliosacral screws. In certain circumstances, utilizing 2 TI-TS screws may confer greater stability and strength, and there may be a need or desire to place them both in a single sacral level safe zone. We describe a technical guide on how to preoperatively assess if the S1 or S2 corridor can safely accommodate 2 TI-TS screws, and how to execute the technique using intraoperative fluoroscopy. We also report our institutional experience of 20 patients who were treated with 2 TI-TS screws for both high-energy and fragility posterior pelvic ring injuries.

Short term functional outcome of single percutaneous Ilio-sacral screw fixation in posterior pelvic ring injuries

Objective: To evaluate functional outcome of single percutaneous iliosacral screw fixation in posterior pelvic ring injuries. Materials and Methods: 20 adult patients of either sex with partially or completely unstable posterior pelvic ring injuries with or without anterior ring injuries admitted between October 2016 to November 2018 were treated with single percutaneous iliosacral screw fixation. The patients were followed clinically and radiologically at four, ten, sixteen and twenty four weeks and assessed with Majeed Pelvic Score.Results: There were 15 male and 5 female with mean average age of 38.1 with 60% being Tiles Type C and 40% being Tiles type B injuries. Out of 20 patients 17 patients (85%) were found to have excellent functional outcome 2 patients (10%) had Good and 1 patient (5%) had fair functional outcome based on clinical grade of Majeed Pelvic score. 1 patient had screw breakage. No patient had Neurological deficit. No case of infection was reported. Conclusion: The results obtained in our study compare well with other studies undertaken in the past and shows that single percutaneous iliosacral screw fixation is safe and efficacious procedure for fixation of sacral fracture and sacroiliac disruption.

Sacral Dysmorphism and its Implication on the Size of the Sacroiliac Joint Surface.

This is a retrospective data analysis. The aim of this study was to analyze the prevalence of sacral dysmorphism and its correlation to the size of the sacroiliac joint (SIJ) surface based on computed tomography (CT) scans. Sacroiliac screw fixation is a widely accepted technique for stabilization of posterior pelvic ring injuries. Safe sacral screw placement may be impaired by sacral dysmorphism. The prevalence and impact of sacral dysmorphism on the size of the SIJ surface is unknown. In total, 269 CT scans were evaluated for the presence of the 5 signs of sacral dysmorphism (mammillary bodies, tongue-in-groove, residual upper sacral disk space, colinearity, and dysmorphic sacral neural foramina). The size of the SIJ surface was calculated by measuring the sacral joint line of the SIJ on each axial CT slice. Logistic regression analyses were conducted to reveal sex-related or age-related differences and correlations between the presence of the dysmorphic signs and the size of the SIJ surface. Prevalence rates of the dysmorphic signs ranged from 5% (colinearity) to 70% (residual sacral disk space). Only 15% did not show any sign of sacral dysmorphism. The average size of the SIJ surface was 7.36 cm; it was significantly larger in male (8.46 cm) than in female (6.11 cm) patients (P<0.001). The presence of tongue-in-groove morphology was associated with a significantly larger SIJ surface (P<0.001), the presence of a residual upper sacral disk space with a significantly smaller joint surface (P=0.006). The prevalence of sacral dysmorphism is remarkably high in a normal population and it is questionable if the respective signs should be called dysmorphic after all. The possibility of a smaller joint surface in female patients and patients with a residual upper sacral disk space should be considered in the planning of iliosacral screw placement.

Псевдоаневризма верхней ягодичной артерии после введения илиосакрального винта – случай консервативного лечения со спонтанным регрессом

Псевдоаневризма верхней ягодичной артерии после введения илиосакрального винта – случай консервативного лечения со спонтанным регрессом

BIOMECHANICAL ANALYSIS OF DIFFERENT SURGICAL STRATEGIES FOR THE TREATMENT OF ROTATIONALLY UNSTABLE PELVIC FRACTURE USING FINITE ELEMENT METHOD

A rotationally unstable pelvic fracture can lead to loss of function and limit moving ability. Immediate fracture fixation is needed for patients with the pelvic fractures. However, it may be difficult to evaluate different surgical strategies for the fracture treatments due to variations in patients’ anatomies and surgical techniques. Thus, the purpose of the present study was to analyze the biomechanical performances of the intact, injured, and treated pelvises based on different physiological movements of the spine using finite element method. Three-dimensional musculoskeletal finite element models of the spine-pelvis-femur complex were developed. The intact pelvis, the rotationally unstable pelvis, and six types of pelvic fixation techniques were analyzed. Additionally, seven types of physiological movements of the spine were also considered. The results showed that the posterior iliosacral screws combined with lower and anterior plate (PIS-LAP) had good fixation stability, lower plate stress, and lower pelvic stress. However, the PIS-LAP increased the stress of the posterior iliosacral screws. The right lateral bending, left lateral bending, and flexion significantly affect all the biomechanical performances compared to the other physiological movements of the spine. The present study can provide engineers and surgeons with the understanding of the biomechanics of various fixation techniques during different physiological movements for the treatment of rotationally unstable pelvic fractures.

When and How to Operate Fragility Fractures of the Pelvis?

Fragility fractures of the pelvis (FFP) are an entity with an increasing frequency. The characteristics of these fractures are different from pelvic ring fractures in younger adults. There is a low energy instead of a high energy trauma mechanism. Due to a specific and consistent decrease of bone mineral density, typical fractures in the anterior and posterior pelvic ring occur. Bilateral sacral ala fractures are frequent. A new classification system distinguishes between four categories with increasing loss of stability. The subtypes represent different localizations of fractures. The primary goal of treatment is restoring mobility and independency. Depending on the amount of instability, conservative or surgical treatment is recommended. The operative technique should be as less invasive as possible. When the broken posterior pelvic ring is fixed operatively, a surgical fixation of the anterior pelvic ring should be considered as well. FFP Type I can be treated conservatively. In many cases, FFP Type II can also be treated conservatively. When conservative treatment fails, percutaneous fixation is performed. FFP Type III and FFP Type IV are treated operatively. The choice of the operation technique is depending on the localization of the fracture. Iliosacral screw osteosynthesis, transsacral bar osteosynthesis, transiliac internal fixation, and iliolumbar fixation are alternatives for stabilization of the posterior pelvic ring. Plate osteosynthesis, retrograde transpubic screw, and anterior internal fixation are alternatives for stabilization of the anterior pelvic ring. Postoperatively, early mobilization, with weight bearing as tolerated, is started. Simultaneously, bone metabolism is also analyzed and its defects compensated. Medical comorbidities should be identified and treated with the help of a multidisciplinary team.

Recommendations for iliosacral screw placement in dysmorphic sacrum based on modified in-out-in corridors.

(1) Can iliosacral osseous corridor diameters in sacral dysmorphism be enlarged by in-out-in screw placement at the posterior iliosacral recessus? (2) Are lumbosacral transitional vertebra (LSTV) the anatomical cause for sacral dysmorphism? (3) Are there sex-specific differences in sacral dysmorphism? 594 multislice CT scans were screened for sacral dysmorphism and 55 data-sets selected. Each pelvis was segmented manually and cylindrical iliosacral corridors (on the level of S1 and S2 vertebra) were semi-automatically determined. Corridor trajectories, -diameters and -lengths were measured. LSTV (Castellvi-type IIIb and IV) were found in 3 of 55 pelves and these lumbosacral variations are therefore not the anatomical basis for sacral dysmorphism. The prevalence of transsacral osseous corridors with diameters of <7.5 mm in axial CT images correlates with qualitative and quantitative criteria of sacral dysmorphism. Enlarging the osseous corridor diameters by penetration of the posterior iliosacral recessus increase the safe corridor diameters (females versus males) by 26% versus 15% at the level of S1- and 50% versus 48% at the level of S2-vertebra. Sex-specific differences for both corridors (osseous and in-out-in) were only found for the osseous corridor diameters at the level of S1 vertebra, being smaller in females (females versus males: 13.3 ± 3.6 mm versus 15.5 ± 3.8 mm, p = 0.04). Dysmorphic sacra can be reliably detected on standard axial CT slice images. Modified in-out-in corridors on the level of S1-vertebra allow screw placement in all patients, but is still demanding compared to non-dysmorphic sacra, due to the oblique corridor axis. Recommendations for intraoperative orientation for oblique screw placement are defined. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

A novel patient-specific three-dimensional-printed external template to guide iliosacral screw insertion: a retrospective study

BackgroundIliosacral screw fixation is a popular method for the management of posterior pelvic ring fractures or dislocations, providing adequate biomechanical stability. Our aim in this study was to describe the use of a new patient-specific external template to guide the insertion of iliosacral screws and to evaluate the efficacy and safety of this technique compared with the conventional fluoroscopy-guided technique.MethodsThis was a retrospective study of patients with incomplete or complete posterior pelvic ring disruptions who required iliosacral screw fixation. For analysis, patients were divided into two groups: the external template group (37 screws in 22 patients) and the conventional group (28 screws in 18 patients). The operative time per screw, radiation exposure time and the rate of screw perforation (accuracy) were compared between groups. In the external template group, the difference between the actual and planned iliosacral screw position was also compared.ResultsIn the conventional group, the average operative time per screw was 39.7 ± 10.6 min, with an average radiation exposure dose of 1904.0 ± 844.5 cGy/cm2, with 4 cases of screw perforation. In the external template group, the average operative time per screw was 17.9 ± 4.7 min, with an average radiation exposure dose of 742.8 ± 230.6 cGy/cm2 and 1 case of screw perforation. In the template group, the mean deviation distance between the actual and planned screw position was 2.75 ± 1.0 mm at the tip, 1.83 ± 0.67 mm in the nerve root tunnel zone and 1.52 ± 0.48 mm at the entry point, with a mean deviation angle of 1.73 ± 0.80°.ConclusionsThe external template provides an accurate and safe navigation tool for percutaneous iliosacral screw insertion that could decrease the operative time and radiation exposure.

Factors influencing the accuracy of iliosacral screw insertion using 3D fluoroscopic navigation.

The purpose of the present study was to determine which factors affect the positional accuracy of iliosacral screws inserted using 3D fluoroscopic navigation. Specifically, we asked: (1) does the screw insertion angle in the coronal and axial planes affect the positional accuracy of iliosacral screw insertion using 3D fluoroscopic navigation? (2) Is the positional accuracy of iliosacral screw insertion using 3D fluoroscopic navigation affected by the type of screw (transsacral versus standard iliosacral), site of screw insertion (S1 versus S2), patient position (supine versus prone), presence of a dysmorphic sacrum, or AO/OTA classification (type B versus C)? Twenty-seven patients with AO/OTA type B or C pelvic ring fracture were treated by percutaneous iliosacral screw fixation. A total of 55 screws were inserted into S1 or S2 using 3D fluoroscopic navigation combined with preoperative CT-based planning. The positional accuracy of screw placement was assessed by matching postoperative CT images with preoperative CT images. The distance between the central axis of the inserted screw and that of the planned screw placement was measured in the sagittal plane passing through the center of the vertebral body. The mean deviation between the planned and the inserted screw position was 2.9 ± 1.7mm (range 0-8.5mm) at the vertebral body center. Multiple regression analysis showed that the screw insertion angle relative to the vertical line of the bone surface in the axial plane (β = 0.354, p = 0.013) and the use of a transsacral screw (β = 0.317, p = 0.017) were correlated with the positional accuracy of screw placement (adjusted R2 = 0.276, p = 0.002). A greater screw insertion angle relative to the vertical line on the bone surface and the use of transsacral screws increases the positional error of iliosacral screws inserted using 3D fluoroscopic navigation. Level IV, therapeutic study.

Biomechanical Study of Posterior Pelvic Fixations in Vertically Unstable Sacral Fractures: An Alternative to Triangular Osteosynthesis.

Study DesignBiomechanical study.PurposeTo investigate the relative stiffness of a new posterior pelvic fixation for unstable vertical fractures of the sacrum.Overview of LiteratureThe reported operative fixation techniques for vertical sacral fractures include iliosacral screw, sacral bar fixations, transiliac plating, and local plate osteosynthesis. Clinical as well as biomechanical studies have demonstrated that these conventional techniques are insufficient to stabilize the vertically unstable sacral fractures.MethodsTo simulate a vertically unstable fractured sacrum, 12 synthetic pelvic models were prepared. In each model, a 5-mm gap was created through the left transforaminal zone (Denis zone II). The pubic symphysis was completely separated and then stabilized using a 3.5-mm reconstruction plate. Four each of the unstable pelvic models were then fixed with two iliosacral screws, a tension band plate, or a transiliac fixation plus one iliosacral screw. The left hemipelvis of these specimens was docked to a rigid base plate and loaded on an S1 endplate by using the Zwick Roell z010 material testing machine. Then, the vertical displacement and coronal tilt of the right hemipelves and the applied force were measured.ResultsThe transiliac fixation plus one iliosacral screw constructions could withstand a force at 5 mm of vertical displacement greater than the two iliosacral screw constructions (p=0.012) and the tension band plate constructions (p=0.003). The tension band plate constructions could withstand a force at 5° of coronal tilt less than the two iliosacral screw constructions (p=0.027) and the transiliac fixation plus one iliosacral screw constructions (p=0.049).ConclusionsThis study proposes the use of transiliac fixation in addition to an iliosacral screw to stabilize vertically unstable sacral fractures. Our biomechanical data demonstrated the superiority of adding transiliac fixation to withstand vertical displacement forces.

High-Energy Pelvic Ring Disruptions with Complete Posterior Instability: Contemporary Reduction and Fixation Strategies.

* Accurate reduction and rigid internal fixation of anterior pelvic ring injuries enhances overall stability of the pelvic ring and augments posterior fixation constructs.* Closed reduction techniques can be highly effective for unstable pelvic ring disruptions and are preferable over open reduction methods.* Percutaneous iliosacral screw fixation is a generally safe and effective method of fixation of posterior pelvic ring injuries.* Multiple and longer (transiliac-transsacral) screws at both sacral segments are required to create a stronger screw construct for complete posterior pelvic disruptions.* Lumbopelvic fixation substantially augments iliosacral screw fixation and is particularly useful for comminuted transforaminal sacral fractures with associated vertical instability.

Anterior Pelvic Ring: Introduction to Evaluation and Management.

The evaluation and management of pelvic ring injuries continues to evolve. Historic treatment was primarily nonsurgical, which yielded to open surgical treatment as the benefits of restoring pelvic anatomy and stability became clear. The development of percutaneous techniques for pelvic ring fixation enabled surgeons to reduce and stabilize certain injuries without the need for large open surgical dissections. Although percutaneous iliosacral screw fixation of sacral fractures and sacroiliac disruptions is the standard for most posterior pelvic ring injuries, the evaluation and treatment of anterior pelvic ring disruptions remains a controversial topic among surgeons who treat these injuries. Universally accepted indications for anterior pelvic ring stabilization do not exist, and there is little comparative data to support one surgical technique over another. In fact, some believe that for many injuries, the anterior ring rarely requires fixation after stable fixation of the posterior pelvic ring. The purpose of this work is to present a brief history on management of the anterior pelvic ring as a component of pelvic ring disruptions and briefly review the anatomy of the anterior pelvic ring. Finally, we will introduce the current techniques available for anterior pelvic reduction/stabilization and present information on evaluation of anterior ring stability as a means of guiding treatment.

Computational analysis on the feasibility of transverse iliosacral screw fixation for different sacral segments.

To evaluate the feasibility of transverse iliosacral (TIS) screw placement in different segments of the sacrum and measure the parameters of the unilateral iliosacral (IS) screw in the case that cannot be inserted the TIS screw. This study used 100 pelvic continuous computed tomography images. Mimics (Materialise Interactive Medical Image Control System) was used to reconstruct the three-dimensional pelvis model. All sacrums were divided into the normal group and dysmorphic group. Any difference in osseous fixation pathway (OFP) diameter in the first two segments between both groups was investigated. In dysmorphic sacrums, the optimal inserting angle and length of the unilateral S1 screw were measured. The number of foramen in every sacrum was recorded. Thirty-two sacrums had sacral dysmorphism. The OFP diameter for the S2 TIS screw in the dysmorphic group was larger than that in the normal group (p = 0.02). Receiver operating characteristic curve analysis indicated the cutoff values as 20.55mm and 15.18° for the S1 front edge height and S1S2 angle, respectively. In the dysmorphic case, the unilateral S1 IS screw should be inserted with a cephalad incline angle of 36.14 ± 5.97° and a ventrally incline angle of 37.33 ± 4.64°. S3 TIS screw placement rate was 53.1% in the dysmorphic group. The most common cause of sacral dysmorphism is the fusion of the L5 to the true S1. In dysmorphic sacrums, the unilateral IS screw should be placed obliquely in the S1 segment, and the S2 segment usually has a sufficient OFP for the TIS screw. Using S3 TIS screw and two TIS screws in the first segment technique is not recommended because of a high risk.

Intraoperative CT and Surgical Navigation for Iliosacral Screws: Technique for Patients With Sacral Dysmorphism.

Percutaneous iliosacral screw (IS) fixation for pelvic ring injuries with the use of an O-arm imaging system has been associated with decreased procedure time and improved accuracy of IS screw placement compared with the use of fluoroscopic guidance. Specifically, patients with sacral dysmorphism require identification of safe bony sacral corridors, using specific anatomical measurements, to decrease the likelihood of complications such as screw perforation. Intraoperative computed tomography imaging and navigation can aid in safe and accurate IS screw fixation in patients with difficult anatomy.

Accuracy of navigated and conventional iliosacral screw placement in B- and C-type pelvic ring fractures.

The objective of this study is to report the institutions experiences with standardized 2D computer-navigated percutaneous iliosacral screw placement (CNS), as well as the conventional fluoroscopically assisted screw placement method (CF) over a period of 10years. A total of 604 patients with sacral fractures (OTA B and C) were treated at the institution. Cases with both, a preoperative and postoperative CT scan were included for further analysis. With this prerequisite, a total of 136 cases were included. The quality of screw positioning, length of operation and intraoperative radiation exposure were recorded and compared. Moreover, it was analyzed whether the presence of dysmorphic sacra influenced the precision of screw positioning. Two hundred and thirty-two screws were implanted in 136 patients (100 navigated, 36 conventional). The duration of the average procedure was similar in the two groups [49.8min (p = 0.7) conventional group (CF) vs. 48.0min computer-navigated (CNS) group]. With computer navigation, radiation exposure was significantly reduced by almost half [128.3 vs. 65.2s (p = 0.023)]. Screw placement was more accurate in the navigation group (79.03% CF vs. 86.47% CNS). The presence of dysmorphic sacral foramina or an increased alar slope increased the incidence of screw malpositioning. The conventional percutaneous method and a standardized 2D navigated method have similar rates of malpositioning. Dysmorphic upper sacral foramina and increased alar slope were identified as risk factors for screw malpositioning. Radiation exposure rates were reduced by half when using computer navigation. Therefore, computer navigation in iliosacral screw placement is recommended as method of choice.

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

BackgroundPelvic ring–comminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure. ObjectiveOur study purpose was to use three-dimensional (3D) optical tracking to detect onset location of bone–implant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques. Methods3D relative motion across sacral–rami fractures and screws relative to bone was measured with an optical tracking system. Synthetic pelves were used. Comminuted transforaminal sacral–rami fractures were modelled. Each pelvis was stabilised by either (1) two iliosacral screws in S1, (2) one transsacral screw in S1 and one iliosacral screw in S1 and (3) one trans-alar screw in S1 and one iliosacral screw in S1; groups 4–6 consisted of fixation groups with addition of anterior inferior iliac pelvic external fixator. Eighteen-instrumented pelvic models with right ilium fixed simulate single-leg stance. Load was applied to centre of S1 superior endplate. Five cycles of torque was initially applied, sequentially increased until permanent deformation occurred. Five cycles of axial load compression was next applied, sequentially increased until permanent deformation occurred, followed by axial loading to catastrophic failure. A Student t test was used to determine significance (p < 0.05). ResultsThe model, protocol and 3D optical system have the ability to locate how sub-catastrophic failures initiate. Our results indicate failure of all screw-based constructs is due to localised bone failure (screw pull-in push-out at the ipsilateral ilium–screw interface, not in sacrum); thus, no difference was observed when not supplemented with external fixation. ConclusionInclusion of external fixation improved resistance only to torsional loading. Translational Potential of this ArticlePatients with comminuted transforaminal sacral–ipsilateral rami fractures benefit from this fixation.

Anatomical Study of a Novel Iliosacral Screw Placement for Sacrum-Pelvis in Adult Via Computed Tomography Reconstruction.

This is a cross-sectional study. To investigate the feasibility and safety of a novel iliosacral screw placement for sacrum-pelvis in adult pelvis by computed tomography (CT) reconstruction. The optimal technique of spino-pelvic fixation is still being developed and redefined. However, neither the relevant anatomic parameters nor the potential spinal canal involvement for a novel iliosacral screw placement have been clearly analyzed. A total of 60 adults with normal pelvis, with the age ranging from 24 to 79 years old, were included in this study. Based on three-dimensional (3D) CT reconstruction of each pelvis, virtual iliosacral screw channel was identified bilaterally, the trajectory of which was characterized with the optimal width and length from the ilium to the sacrum. The virtual iliosacral screw channel that holding the greatest width and length of osseous channel was measured by rotating the 3D pelvis. Measurements of the determined channel on either side included iliosacral-screw-related and connector-related parameters. There was a virtual iliosacral screw channel passing through the ilium, the iliosacral joint and then into the sacrum on either side of each pelvis. The caudal angle, convergent angle, and maximal length were 16.3 ± 3.0°, 61.3 ± 5.9°, 97.0 ± 5.6 mm in male, respectively. In female, they were 16.4 ± 3.9°, 63.0 ± 5.5° and 96.2 ± 6.0 mm, respectively. The ideal direction of the connector was from posteromedial to anterolateral. The cephalad angle, divergent angle, and embedding depth of the connector were 28.0 ± 5.7°, 28.7 ± 5.9° and 19.0 ± 2.9 mm in male, respectively. In female, they were 26.7 ± 6.1°, 27.0 ± 5.5° and 16.4 ± 2.6 mm, respectively. It is safe and feasible to place the iliosacral screw when performing this novel instrumentation. Preoperative CT imaging and 3D reconstructions may help to determine the correct entry point and the trajectory of iliosacral screw. 5.

Minimally invasive, robot-assisted iliosacral screw insertion for fusionless fixation in children with neuromuscular scoliosis.

Fusionless surgery coupled with growing rod techniques is increasingly advocated for the treatment of early-onset scoliosis in general and neuromuscular scoliosis in particular. Iliosacral screws have excellent biomechanical characteristics but are hard to place safely. Here, the authors report on robot-assisted iliosacral screw positioning as part of growing rod surgery for the fusionless correction of early-onset scoliosis. The technique is based on a bilateral double sliding rod construct anchored to the pelvis proximally with 6 hooks or sublaminar bands and distally with iliosacral screws placed by the robot. The video can be found here: https://youtu.be/5HGH_DiD-ck .