Sacral Dysmorphism Research Articles

Évaluation du couloir osseux pour vissage trans-iliaque et trans sacral et ses applications cliniques : étude de simulation informatique

BackgroundTransiliac-transsacral (TITS) screw fixation might be necessary in some cases involving the vertical shearing injuries with transforaminal fracture and bilateral posterior ring injuries. However, the possibility of S1 TITS screw should be preoperatively assessed because the pelvic ring injuries with sacral dysmorphism had the insufficient osseous corridors. HypothesisAxWS2 may predict the possibility of TITS screw fixation and be used as the new indicator to discriminate the sacral dysmorphism. Materials and methodsThe conventional CT images of Eighty-two cadaveric pelvis imported into Mimics® software to reconstruct three-dimensional (3D) models. A 7.0-mm-sized screw was processed into a 3D model using a 3D-sensor at actual size and virtually implanted as S1 and S2 TITS screw using Mimics® software. The cortical violation around screw path was evaluated using 3D biplanar and conventional CT images. The osseous corridor widths around TITS screws were measured in the axial plane images and defined as AxWS1 and AxWS2, respectively. ResultsDespite no cortical violation in S2 of all models, cortical violation of S1 TITS screw was found in 20 models. Of them, 14 models (impossible models) were identified in the 3D biplanar images, and all 20 models (CT-violation models) were identified only in CT axial plane images. AxWS1 was<7mm in the impossible models and<9.0mm in the CT-violation models. AxWS2 negatively correlated with AxWS1 (R 0.450, p<0.01). By receiver operating characteristic curve analysis to identify the CT-violation model using AxWS2, the cut-off value of AxWS2 was 13.32mm (sensitivity 0.70, specificity 0.70). DiscussionBy using AxWS2, The possibility of S1 TITS screw fixation could be predicted and safely placed without cortical violation, if AxWS2 was less than 13mm. Considering the negative relationship with AxWS1, AxWS2 should be used as new indicator to predict safe S1 TITS screw fixation. Level of evidenceIII, controlled laboratory study.

Determination of Anatomical Sacral Dysmorphism Criteria based on CT scan Findings for Iliosacral Screw Fixation in a Sample of Iranian Population without Pelvic Ring Fracture

Background: The pelvic ring, sacral fractures and sacroiliac dislocations are managed with different methods. The preferred treatment in sacral fractures or SIjoint dislocations is iliosacral screw fixation. The upper sacral segment dysplasia increases the risk of perforation of the osseous cortex during Iliosacral fixation with a screw. The dysmorphic sacra have a narrow and angular osseous corridor. Objectives: To date, no study has been conducted on the sacral dysmorphism and quantitative and qualitative criteria for fixation with iliosacral screw in sacral dysmorphism among the Iranian population. Methods: We analyzed 100 CT scan and Outlet CT reformation forms of traumatic patients without pelvic trauma to determine 5 qualitative criteria of sacral dysmorphism (i.e., mammillary bodies, misshapen sacral foramen, upper sacral segment not recessed in the pelvis, residual disc between S1 and S2 vertebra and acute alar slope). Upper sacral surface area and angulation were determined based on the CT scan reformatted. Results: Five qualitative criteria from the 3D pelvic CT outlet view and sixth characteristic (tongue-in-groove) from the axial pelvic CT section were obtained by an orthopedic surgeon. Coronal reconstruction was used to divide the patients into dysmorphic and non-dysmorphic groups by drawing a line along the axis of the osseous corridor from one side of iliosacral to its other side. The results showed that 37% of the patients were in the dysmorphic group and 63% in non-dysmorphic. Qualitative criteria were in the range 24% -71% in the dysmorphic group and 14%-34% in the non-dysmorphic group. The sacral dysmorphism score was calculated in all patients. The sacral dysmorphism score = (first sacral segment coronal angle) + 2(first sacral segment axial angle). The obtained mean angle in the dysmorphic and non-dysmorphic group was 84° and 72°, respectively. As the score increased, the safety of the osseous corridor decreased. The dysmorphic score ranged between 70 and 84 in one-third of the patients and none of them was less than 70°. Conclusion: In this study, sacral dysmorphism was detected in 37% of the patients. Axial angulation and coronal angulation were the most important quantitative criteria for determining the sacral dysmorphism. Detecting sacral dysmorphism can be useful for preoperative planning of iliosacral screw placement.

Assessment of osseous corridor for transiliac–transsacral screws and clinical applications: Computational simulation study

BackgroundTransiliac–transsacral (TITS) screw fixation might be necessary in some cases involving the vertical shearing injuries with transforaminal fracture and bilateral posterior ring injuries. However, the possibility of S1 TITS screw should be preoperatively assessed because the pelvic ring injuries with sacral dysmorphism had the insufficient osseous corridors. HypothesisAxWS2 may predict the possibility of TITS screw fixation and be used as the new indicator to discriminate the sacral dysmorphism. Materials & methodsThe conventional CT images of eighty-two cadaveric pelvis imported into Mimics® software to reconstruct three-dimensional (3D) models. A 7.0 mm-sized screw was processed into a 3D model using a 3D-sensor at actual size and virtually implanted as S1 and S2 TITS screw using Mimics® software. The cortical violation around screw path was evaluated using 3D biplanar and conventional CT images. The osseous corridor widths around TITS screws were measured in the axial plane images and defined as AxWS1 and AxWS2, respectively. ResultsDespite no cortical violation in S2 of all models, cortical violation of S1 TITS screw was found in 20 models. Of them, 14 models (impossible models) were identified in the 3D biplanar images, and all 20 models (CT-violation models) were identified only in CT axial plane images. AxWS1 was<7mm in the impossible models and<9.0mm in the CT-violation models. AxWS2 negatively correlated with AxWS1 (R -0.450, p<0.01). By receiver operating characteristic curve analysis to identify the CT-violation model using AxWS2, the cut-off value of AxWS2 was 13.32mm (sensitivity 0.70, specificity 0.70). DiscussionBy using AxWS2, the possibility of S1 TITS screw fixation could be predicted and safely placed without cortical violation, if AxWS2 was less than 13mm. Considering the negative relationship with AxWS1, AxWS2 should be used as a new indicator to predict safe S1 TITS screw fixation. Level of evidenceIII, controlled laboratory study.

Surgical Technique of Percutaneous Iliosacral Screw Fixation in S3 Level in Unstable Pelvic Fracture with Closed Degloving Injury and Morrell Lavallee Lesion: Two Case Reports

Unstable pelvic ring fractures raise treatment challenges in severely injured patients. Beside patient survival, demanding surgical technique also required. Classic technique of internal fixation requires extensive surgical exposure that leads to most complications of the pelvic fractures fixation. Therefore less invasive technique is a reasonable alternative especially in unstable pelvic fracture with soft tissue injury or potential infection. Unfortunately in sacral dysmorphism pelvic injury or in complete vertical sacral fracture, we need S3 level insertion to improve stability of iliosacral (IS) screw in S1 or S2. Purpose of this study was to show feasibility technically inserting IS screw in S3 level.Methods:We reported 2 cases of unstable pelvic injury. First case was an 11 years old boy with Torode and Zieg IV or Marvin Tile C1 pelvic fracture with right sacroiliac joint disruption and soft tissue injuries of skin avulsion on the left hip and Morel-Lavallée lesion on the right hip. He was managed with early anatomic reduction and fixation with percutaneous screws on both pubic rami and IS screw (sacroiliac lag screw type) on S1 and S3. Second case was a 30 years old male with open pelvic fracture Faringer zone III type, Marvin Tile B2 or YoungBurgess LC I and also with vertical sacral fracture Denis zone 1. This polytrauma case had associated injuries includes Morel-Lavallée lesion, intraperitoneal bladder rupture, infected laparotomy wound dehiscence, and immunocompromised. The same minimal invasive management of pelvic fracture was performed in this case by inserting percutaneous screws on pubic rami and IS (sacral screw type) on S1 and S3. Functional outcome was evaluated using Majeed and Hannover pelvic scoring system.Results:All patients survived and considered to have good reduction, with no residual displacement on the sacroiliac joint. The former case, at 21-month follow up, present with excellent outcome (80 out of 80) by Majeed score and very good outcome (4 out of 4) by Hannover score; while the latter case, at 18-month follow up, present with poor outcome (50 out of 100) by Majeed score and fair outcome (2 out of 4) by Hannover score.Conclusion:Percutaneous screw fixation for pelvic ring injury is a less invasive alternative that can be used for early stabilization of unstable anterior and posterior pelvic fractures and provide stable internal fixation. IS screw is feasible to be inserted in S3 level either sacroiliac joint type or sacral screw type.

Gender-Associated Differences in Sacral Morphology Do Not Affect Feasibility Rates of Transsacral Screw Insertion. Radioanatomic Investigation Based on Pelvic Cross-sectional Imaging of 200 Individuals.

Retrospective radioanatomic single-center cohort study. To investigate sex-specific differences in transsacral corridor dimensions, determine feasibility rates of transsacral screw placement without extended safety zones around planned screw positions, and develop an index defining sacral dysmorphism (SD) irrespective of transsacral corridor diameters. Previously reported SD definitions used radiologically identifiable pelvic characteristics or predefined minimum diameter thresholds of transsacral corridors in the upper sacral segment including safety zones for screw placement. Technical progress of surgical 3D image guidance improved sacral screw insertion accuracy questioning established minimum diameter threshold-based SD definitions. Datasets from cross-sectional pelvic imaging of 100 women and 100 men presenting to a general hospital from July 2018 through August 2018 were included in a database to evaluate transsacral trajectory rates, and dimensions of transsacral corridor lengths, widths (TSCWs), and heights (TSCHs) in sacral segments I to III (S1-3). SD was assumed, if no transsacral trajectory was found in S1 with a corridor diameter of at least 7.5 mm. Women presented significantly higher rates of transsacral trajectories in the inferior sector of S1 (P = 0.03), and larger transsacral corridor lengths in S2 (superior sector, P = 0.045), and S3 (central position, P = 0.02). In men, significantly higher feasibility rates were found for the placement of two transsacral screws in S2 (P = 0.0002), and singular screws in S3 (P = 0.006), with larger S1- (P = 0.0002), and central S2-TSCWs (P = 0.006). SD was prevalent in 17% of women, and 16% of men (P = 0.85). Calculating TSCW ratios of S1 and S2 was significantly indicative for SD at values below a threshold of 0.8 in women (P < 0.00001), and men (P = 0.0004). SD is independent of sex despite significant differences in sacral morphology. An index defining SD irrespective of absolute transsacral corridor dimensions is presented to reliably differentiate dysmorphic from nondysmorphic sacra in women and men. 2.

Intérêt de la manipulation des plans en tomodensitométrie pour identifier le dysmorphisme sacré et évaluer la variabilité de hauteur pour prédire la possibilité de fixation par vis trans-sacrée

IntroductionIlio-sacral screw fixation has been used for sacral fractures and sacroiliac joint dislocations. However, it is associated with significant complications including screw loosening with backing-out and loss of reduction. Trans-sacral screw fixation is indicated for rigid fixation in specific circumstances including bilateral posterior ring injuries, osteoporotic bone, or to supplement other types of posterior ring fixation. HypothesisThe reformatting the CT scanning plane may distinguish sacral dysmorphism and predict the possibility of trans-sacral screw fixation by introducing the new indicator. Material and methodsThe CT data of 112 adult cadavers (61 males and 51 females) were imported into Mimics® software and a 7.0mm-sized trans-sacral screw was virtually placed in the ideal position of S1. The osseous widths around screw in the axial images (AxWS1) were measured. By reformatting the CT scanning plane parallel to the superior endplate of S1, the AxWRS1 was measured and the height of elevated segment in the upper sacrum (elevated height) was assessed as a new preoperative indicator. ResultsCortical violation around screw was detected in 26 models and was considered as sacral dysmorphism. The average AxWS1 was measured as 13.70±2.76mm in the non-dysmorphism group, and 5.81±2.19mm in the dysmorphism group, with statistical difference (p<0.001). By reformatting the CT scanning plane, the average AxWRS1 increased to 16.61±2.79mm in the non-dysmorphism group, and 8.04±2.62 in the dysmorphism group, and the difference was statistically significant (p<0.001). The elevated height was 3.29±4.19mm in the non-dysmorphism group, and 17.52±3.09mm in the dysmorphism group, and the differences were statistically significant (p<0.001). Based on the ROC curve analysis, the cut-off value of elevated height was 12.90mm (sensitivity 1.0 and specificity 1.0). DiscussionBy reformatting the CT scanning plane, the osseous width around screw was widened, and the new preoperative indicator of elevated height could be introduced to predict the possibility of trans-sacral screw fixation into S1. If the elevated height exceeded 13mm, the pelvis was assigned to sacral dysmorphism and thus, could not apply the trans-sacral screw fixation into S1. Level of evidenceIII, controlled laboratory study.

The usefulness of reformatting CT scanning plane to distinguish sacral dysmorphism and introducing the variable of elevated height for predicting the possibility of trans-sacral screw fixation

IntroductionIlio-sacral screw fixation has been used for sacral fractures and sacroiliac joint dislocations. However, it is associated with significant complications including screw loosening with backing-out and loss of reduction. Trans-sacral screw fixation is indicated for rigid fixation in specific circumstances including bilateral posterior ring injuries, osteoporotic bone, or to supplement other types of posterior ring fixation. HypothesisThe reformatting the CT scanning plane may distinguish sacral dysmorphism and predict the possibility of trans-sacral screw fixation by introducing the new indicator. Material and methodsThe CT data of 112 adult cadavers (61 males and 51 females) were imported into Mimics® software and a 7.0 mm-sized trans-sacral screw was virtually placed in the ideal position of S1. The osseous widths around screw in the axial images (AxWS1) were measured. By reformatting the CT scanning plane parallel to the superior endplate of S1, the AxWRS1 was measured and the height of elevated segment in the upper sacrum (elevated height) was assessed as a new preoperative indicator. ResultsCortical violation around screw was detected in 26 models and was considered as sacral dysmorphism. The average AxWS1 was measured as 13.70±2.76mm in the non-dysmorphism group, and 5.81±2.19mm in the dysmorphism group, with statistical difference (p<0.001). By reformatting the CT scanning plane, the average AxWRS1 increased to 16.61±2.79mm in the non-dysmorphism group, and 8.04±2.62 in the dysmorphism group, and the difference was statistically significant (p<0.001). The elevated height was 3.29±4.19mm in the non-dysmorphism group, and 17.52±3.09mm in the dysmorphism group, and the differences were statistically significant (p<0.001). Based on the ROC curve analysis, the cut-off value of elevated height was 12.90mm (sensitivity 1.0 and specificity 1.0). DiscussionBy reformatting the CT scanning plane, the osseous width around screw was widened, and the new preoperative indicator of elevated height could be introduced to predict the possibility of trans-sacral screw fixation into S1. If the elevated height exceeded 13mm, the pelvis was assigned to sacral dysmorphism and thus, could not apply the trans-sacral screw fixation into S1. Level of evidenceIII, controlled laboratory study.

Sacral Dysmorphism and Lumbosacral Transitional Vertebrae (LSTV) Review.

Anatomic variation in the relationship between the lumbar spine and sacrum was first described in the literature nearly a century ago and continues to play an important role in spine deformity, low back pain (LBP), and pelvic trauma. This review will focus on the clinical and surgical implications of abnormal lumbosacral anatomy in the context of sacroiliac joint (SIJ) disease, spine deformity, and pelvic trauma. A PubMed search using the keywords "lumbosacral transitional vertebrae," "LSTV," "transitional lumbosacral vertebrae," "TLSV," and "sacral dysmorphism" was performed. The articles presented here were evaluated by the authors. The prevalence of LSTV varies widely in the literature from 3.9-% to 35.6% in the spine literature, and sacral dysmorphism is described in upwards of 50% of the population in the trauma literature. The relationship between LSTV and LBP is well established. While there is no agreed-on etiology, the source of pain is multifactorial and may be related to abnormal biomechanics and alignment, disc degeneration, and arthritic changes. Understanding abnormal lumbosacral anatomy is crucial for preoperative planning of SIJ fusion, spine deformity, and pelvic trauma surgery. LSTV can alter spinopelvic parameters crucial in planning spine deformity correction. Traditional safe zones for sacroiliac screw placement do not apply in the first sacral segment in sacral dysmorphism and risk iatrogenic nerve injury. LSTV and sacral dysmorphism are common anatomic variants found in the general population. Abnormal lumbosacral anatomy plays a significant role in clinical evaluation of LBP and surgical planning in SIJ fusion, spine deformity, and pelvic trauma. Further studies evaluating the influence of abnormal lumbosacral anatomy on LBP and surgical technique would help guide treatment for these patients.

Feasibility of iliosacral screw placement in patients with upper sacral dysplasia

BackgroundExact knowledge of the sacral anatomy is crucial for the percutaneous insertion of iliosacral screws. However, dysplastic anatomical patterns are common. In addition to a preoperative computed tomography (CT) analysis, conventional radiographic measures may help to identify upper sacral dysplasia and to avoid damage to surrounding structures. Aiming to further increase safety in percutaneous iliosacral screw placement in the presence of sacral dysmorphism, this study examined the prevalence of previously established radiographic signs and, in addition, defined the “critical SI angle” as a new radiographic criterion.MethodsPelvic CT scans of 98 consecutive trauma patients were analysed. Next to assessment of established signs indicating upper sacral dysplasia, the critical sacroiliac (SI) angle was defined in standardized pelvic outlet views.ResultsThe critical SI angle significantly correlates with the presence of mammillary bodies and an intraarticular vacuum phenomenon. With a cut-off value of − 14.2°, the critical SI angle detects the feasibility of a safe iliosacral screw insertion in pelvic outlet views with a sensitivity of 85.9% and a specificity of 85.7%.ConclusionsThe critical SI angle can support the decision-making when planning iliosacral screw fixation. The clinical value of the established signs of upper sacral dysplasia remains uncertain.

Preoperative planning and safe intraoperative placement of iliosacral screws under fluoroscopic control.

ObjectivePreoperative planning of the starting point and safe trajectory for iliosacral screw (SI screw) fixation using CT scans for safe and accurate fluoroscopically controlled percutaneous SI screw placement.IndicationsTransalar and transforaminal sacral fractures. SI joint disruptions and fracture-dislocations. Non- or minimally displaced spinopelvic dissociation injuries.ContraindicationsTransiliac instabilities. Sacral fractures with neurological impairment requiring decompression. Relevant residual displacement after closed reduction attempts. Insufficient fluoroscopic visualization of the anatomical landmarks of the upper sacrum.Surgical techniquePreoperative planning of the starting point and the safe screw trajectory using CT scans and two-dimensional multiplanar reformation tools. Fluoroscopically guided identification of the starting point using the lateral view according to preoperative planning. Advancing the guidewire under fluoroscopic control using inlet and outlet views according to the planned trajectory. Predrilling and placement of 6.5 mm cannulated screws.Postoperative managementWeightbearing as tolerated using crutches. Immediate CT scan in case of postoperative neurological impairment. Generally no screw removal.ResultsFifty-nine screws were placed in 34 patients using the described technique. There were 2 cases of screw malpositioning (anatomical landmarks inadequately identified and fluoroscopically controlled SI screw fixation should thus not have been performed at all; in a case with sacral dysmorphism, preoperative planning suggested a posterior and/or caudal S1 starting point, respectively, but intraoperatively, selection of a different starting point and screw trajectory resulted in screw malpositioning with iatrogenic L5 nerve palsy).

Posterior tension band plate osteosynthesis for unstable sacral fractures: A preliminary study

IntroductionStable reduction and rigid fixation of the sacrum and posterior ring structures are of paramount importance in the management of complex pelvic ring disruptions, Tile B and C. The major concern with the use of conventional methods, like iliosacral screws and iliolumbar fixations is the increased risk for surgical and implant-related morbidity, especially in difficult situations, such as comminuted, bilateral sacral fractures, and fractures in the dysmorphic sacrum. Although various biomechanical studies have reported the posterior trans-iliac plates to provide maximum resistance to distracting forces by the principle of tension band, the literature pertaining to this implication in clinical studies has been limited. The purpose of our study was to assess the efficacy of the trans-iliac plate in the management of unstable sacral fractures and its utility in pelvic disruptions associated with surgical site morbidity. MethodologyThe patients with unstable pelvic fractures (Tile B and C) between 2013 and 2017 were retrospectively analyzed at a trauma center. First, the anterior ring disruptions were stabilized, and then, the sacral fractures (Denis Zone 1–3) treated by posterior tension band plate osteosynthesis (3.5 mm reconstruction plate) were included. Demographic and perioperative data were assessed. The outcome variables studied were surgical morbidity, pain, loss of reduction, and union and implant-related complications. The outcomes were graded using Lindhal's (radiological) and Majeed (functional assessment) scores. ResultsThirteen patients (nine male/four female) with a median age of 42 years, had sacral fractures in Denis zones 1/2/3 (four/ten/one, respectively), resulting from Tile pelvic injury B and C were included. The pelvis in five patients was stabilized only with the posterior plate due to the anteriorly-associated surgical site morbidity (Morel-Lavallee lesions and urinary tract injuries). The mean follow-up was 21.5 ± 2.8 months. All fractures had a radiological union by 22 weeks; Lindhal's grade A in ten patients and grade B in three patients. Two out of three patients recovered from preoperative neurological involvement. Two had complained of implant prominence (BMI<19 kg/m2) and there were no implant failures. Four had excellent, six had good, and three had fair or poor functional outcomes. ConclusionThe posterior trans-iliac plate is a minimally invasive and safe procedure that can be used in a wide range of unstable sacral fractures with notably less implant failure rate. The rigid posterior construct restores the principle tension between the iliac blades and minimizes the secondary displacement of the anterior disrupted structures, thereby useful in managing ring disruptions with surgical site morbidity.

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.

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.

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.

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.

Novel mosaic SRY gene deletions in three newborn males with variable genitourinary malformations.

Ambiguous genitalia in the newborn can present a diagnostic challenge in medical practice. In most cases, the causes of genitourinary anomalies are not well understood; both genetic and environmental factors are thought to play a role. In this study, we report mosaic SRY gene deletion identified by fluorescence in situ hybridization (FISH) analysis in three unrelated newborn male patients with genital anomalies. G-banded chromosomes and microarray analysis were normal for all three patients. One patient had microphallus, hypospadias, bifid scrotum, exstrophic perineal tissue identified as a rectal duplication, lumbar vertebral anomalies, scoliosis, and a dysmorphic sacrum. The other two patients had isolated epispadias with the urethral meatus close to the penopubic junction. All three had bilateral palpable gonads in the scrotum. While this is the first report of mosaic SRY deletions, mosaic SRY sequence variants have been described in patients with variable genitourinary anomalies. This study identifies FISH analysis as a reliable method for mosaic SRY deletion detection. We suggest SRY FISH analysis should be used in the clinical workup of patients with genitourinary ambiguity.

Accuracy of sacroiliac screw placement with and without intraoperative navigation and clinical application of the sacral dysmorphism score

IntroductionPercutaneously-placed sacroiliac (SI) screws are currently the gold-standard fixation technique for fixation of the posterior pelvic ring. The relatively high prevalence of sacral dysmorphism in the general population introduces a high risk of cortical breach with resultant neurovascular damage. This study was performed to compare the accuracy of SI screw placement with and without the use of intraoperative navigation, as well as to externally validate the sacral dysmorphism score in a trauma patient cohort. Patients and methodsAll trauma patients who underwent sacroiliac screw fixation for pelvic fractures at a level 1 trauma centre over a 6 year period were identified. True axial and coronal sacral reconstructions were obtained from their pre-operative CT scans and assessed qualitatively and quantitatively for sacral dysmorphism – a sacral dysmorphism score was calculated by two independent assessors. Post-operative CT scans were then analysed for breaches and correlated with the hospital medical records to check for any clinical sequelae. Results68 screws were inserted in 36 patients, most sustaining injuries from road traffic accidents (50%) or falls from height (36.1%). There was a male preponderance (83.3%) with the majority of the screws inserted percutaneously (86.1%). Intraoperative navigation was used in 47.2% of the patient cohort. 30.6% of the cohort were found to have dysmorphic sacra. The mean sacral dysmorphism scores were not significantly different between navigated and non-navigated groups. Three cortical breaches occurred, two in patients with sacral dysmorphism scores >70 and occurring despite the use of intraoperative navigation. There was no significant difference in the rates of breach between navigated and non-navigated groups. None of the breaches resulted in any clinically observable neurovascular deficit. ConclusionThe sacral dysmorphism score can be clinically applied to a cohort of trauma patients with pelvic fractures. In patients with highly dysmorphic sacra, reflected by high sacral dysmorphism scores, intraoperative navigation is not in itself sufficient to prevent cortical breaches. In such patients it would be prudent to consider instrumentation of the lower sacral corridors instead.

Is S3 a Viable Osseous Fixation Pathway?

To report the incidence of patients with a third sacral segment (S3) osseous fixation pathway (OFP) that could accommodate a transiliac-transsacral screw. Retrospective case series. Regional Level 1 Trauma Center. A total of 250 patients without pelvic trauma from January 2017 to February 2017 were included. The axial and sagittal reconstruction images of each patient's computed abdomen and pelvis tomography (CT) scans were reviewed. Each CT was evaluated for the presence of sacral dysmorphism and whether an S3 OFP that could accommodate an intraosseous transiliac-transsacral screw exists. There were 130 of the 250 patients (52%) with sacral dysmorphism. Overall, 38 of the 250 patients (15.2%) had an S3 OFP that could accommodate a 7.0-mm transiliac-transsacral style screw. When narrowed to patients who had an S3 OFP, 38 of 153 patients (24.8%) could accommodate a 7.0-mm transiliac-transsacral screw. Specific to the 38 patients with an adequate S3 OFP, 34 of 38 patients (89.5%) were noted to have sacral dysmorphism. Our study demonstrates that 15.2% of patients have an S3 OFP large enough to accommodate an intraosseous implant. Patients who have sacral dysmorphism are more likely to have an adequate S3 OFP. Additional studies are needed to quantify the S3 OFP, understand the bone quality of the S3 segment and accompanying biomechanical implications, and investigate the anatomical concerns associated with S3 screw placement. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Percutaneous Placement of Iliosacral Screws Under the Guidance of Axial View Projection of the S1 Pedicle: a Case Series

The aim of this study was to evaluate the safety and efficacy of percutaneous placement of iliosacral screws under the guidance of axial view projection of the S1 pedicle clinically. This case series includes 58 consecutive unstable pelvic injury patients, which were treated with iliosacral screws between July 2011 and July 2016. Patients were divided into two groups: normal sacrum (n = 31) and dysmorphic sacrum (n = 27). A single orthopedic surgeon operated on all patients, with percutaneous placement of iliosacral screws under the guidance of axial view projection of the S1 pedicle. The time needed for screw insertion and the radiation exposure time were recorded. Chi-squared test and Student t-test were used to analyze the differences between the two groups. Sacral dysmorphism was present in 47% of patients. The median time for screw insertion and radiation exposure time in these two groups showed no statistical difference (P > 0.05). No clinical complications or malpositioned screws occurred in any case. Preoperative pelvic CT is necessary to determine the sacral osseous anatomy. In patients with either a normal or dysmorphic sacrum, iliosacral screws can be placed by this method with less radiation exposure and complications than in the conventional method.