S2 iliosacral screw fixation for disruptions of the posterior pelvic ring: a report of 49 cases

Simplifying the Orientation of S1 Iliosacral Screws for Placement in the Dysmorphic Sacrum

BACKGROUND

Determining the proper iliosacral screw orientation in a dysmorphic S1 sacral segment using a C-arm is difficult, and pelvic computed tomography (CT) is often necessary for the preoperative planning. On the preoperative pelvic axial CT section, the intended screw trajectory can be delineated intraosseously along the axis of the oblique osseous corridor. An inherently accurate orientation would be determined by 2 factors: (1) the trajectory is in the pelvic transverse plane, and (2) it is oriented relative to the coronal plane at a patient-specific angle, which should be measured preoperatively. Based on the above reasoning, we aimed to simplify and verify the orientation.

METHODS

After establishing the starting point on the sacral lateral view, we tested a method of simplifying the guidewire orientation: placing the guidewire in the pelvic transverse plane and then manipulating it to be angled relative to the coronal plane at the preoperatively measured patient-specific angle. The guidewire orientation should then be reproducibly accurate on the pelvic outlet and inlet views. The feasibility and safety of our method were verified through computer-simulated virtual surgical procedures in 95 dysmorphic sacra and clinical surgical procedures in 12 patients. The primary outcome parameters were the guidewire orientation and screw placement accuracy.

RESULTS

Using our method, the S1 guidewire orientation was reproducibly accurate on the pelvic outlet and inlet views in all of the virtual and clinical surgical procedures. Ninety-five virtual S1 screws (1 screw in each left hemipelvis) were placed intraosseously in the pelvic transverse plane. Fourteen unilateral S1 screws were placed intraosseously in the pelvic transverse plane in the 12 patients (2 patients had double screws) without iatrogenic injuries.

CONCLUSIONS

The guidewire orientation can be simplified by placing the guidewire in the pelvic transverse plane and replicating the preoperatively measured patient-specific angle between the guidewire and the coronal plane. After establishing the starting point on the sacral lateral view, our simplified manipulation yields a reproducibly accurate orientation on the pelvic outlet and inlet views.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Iliosacral screw osteosynthesis - state of the art

Iliosacral screw osteosynthesis is a widely recognized technique for stabilizing unstable posterior pelvic ring injuries, offering notable advantages, including enhanced mechanical stability, minimal invasiveness, reduced blood loss, and lower infection rates. However, the procedure presents technical challenges due to the complex anatomy of the sacrum and the proximity of critical neurovascular structures. While conventional fluoroscopy remains the primary method for intraoperative guidance, precise preoperative planning using multiplanar reconstructions and three-dimensional volume rendering is crucial for ensuring accurate placement of iliosacral or transsacral screws. Particular attention must be given to the preoperative evaluation of both the iliosacral and transsacral corridors, as anatomical variations may restrict the available space for screw insertion. This review aims to highlight the essential aspects of sacroiliac osteosynthesis, with a focus on the critical role of thorough preoperative planning and its impact on achieving successful surgical outcomes.

Evaluation of the true lateral fluoroscopic projection for the relation of the S1 recess/foramen to safe corridors in transiliac-transsacral screw placement in human cadaveric pelves

INTRODUCTION

Percutaneous screw fixation is a widely used treatment for posterior pelvic ring injuries. Transiliac-transsacral screw fixation has demonstrated superior biomechanical properties over bilateral sacroiliac screws, particularly in the minimally displaced bilateral sacral fractures. Screw placement under fluoroscopic control is still common, while CT navigation is gaining popularity. However, the accurate placement of screws within a safe zone is essential to avoid neurovascular complications.

METHODS

An anatomical study using human cadaveric pelves was conducted to assess radiological landmarks and determine a safe zone in relation to the S1 recess/foramen for transiliac-transsacral screw placement.

RESULTS

Fourteen pelves were evaluated. Ten pelves were classified as having a satisfactory corridor for screw placement, while four were deemed to have an impossible or high-risk corridor. A safe zone was defined based on the diagonal bisector of the S1 vertebral body, ICD and anterior cortex.

DISCUSSION

The study findings suggest that lateral fluoroscopic projection can determine a safe entry point for screw placement. Understanding the anatomy and landmarks on lateral fluoroscopic images is crucial for successful screw placement and avoiding complications.

CONCLUSION

The S1 body diagonal is consistently located anterior to the S1 recess in lateral fluoroscopic projections, providing a potential safe corridor for transiliac-transsacral screw placement at the S1 level in nondysmorphic pelves. Further research is needed to confirm these findings with CT imaging and evaluate the technical feasibility of screw placement.

Experimental study of fractures of the posterior pelvic ring C1.1 using LC-II screws and internal fixation by plate

INTRODUCTION

To compare the biomechanical outcomes of C1.1 posterior pelvic ring fractures treated with different numbers of LC-II screws and plate internal fixation.

MATERIALS AND METHODS

Nine adult preserved pelvic specimens were used. After being measured by bone densitometry, the specimens were randomly divided into 3 groups of 3 pelvic specimens each. The C1.1 pelvic fractures were generated by iliac osteotomies and anterior pelvic ring osteotomies. The fractures were fixed and randomly divided into three groups: (1) one LC-II screw, (2) two LC-II screws, and (3) two reconstruction plates. The anterior pelvic rings were all fixed with pubic branch screws. A biomechanical testing machine loaded all specimens vertically, recording the displacement and ultimate load of the specimens to quantify the stiffness.

RESULTS

When loads up to 1000 N were applied, the displacement of the iliac bone was close between the one LC-II screw and the two LC-II screw group specimens; (P > 0.05); when loads such as 1000 N, 1200 N and 1400 N were applied, there was no significant difference in displacement between the plate fixation group and the two LC-II screw fixation group (P > 0.05), both of which were superior to the one LC-II screw fixation group (P < 0.05). There was no significant difference in compressive stiffness between the two LC-II screw fixation groups and the plate fixation group (P > 0.05), and both were superior to the one LC-II screw fixation group (P < 0.05) the ultimate load of both the two LC-II screws and the steel plate is greater than that of one LC-II screw (1.74 times the ultimate load of one LC-II screw for the two LC-II screws and 1.83 times the ultimate load of one LC-II screw for the steel plate).

CONCLUSION

For posterior pelvic ring fractures of type C1.1, placement of two LC-II screws provides comparable posterior pelvic ring stability compared to reconstructed plates. At loads below 1000 N, one LC-II screw fixation and two LC-II screws were comparable in restoring posterior pelvic ring stability.

CT-Based Evaluation of Volumetric Posterior Pelvic Bone Density with Implications for the Percutaneous Screw Fixation of the Sacroiliac Joint

Background: Operative treatment of fragility fractures of the pelvis has become a gold standard. Preoperative planning, including the assessment of the pathway for iliosacral screws, is crucial. The anchorage of the screw depends on the bone quality. Some recent studies have concentrated on assessing bone mineral density (BMD) with the use of Hounsfield unit (HU) values obtained from CT scans. The aim of the present study is to determine the best sacral levels of S1-S3 on the pathway of iliosacral screws for sacroiliac joint fixation. Methods: Patients admitted to the Independent Public Healthcare Center in Rypin between 1 of September and 1 of December in 2023, who had CT scans of the pelvis performed on them for different reasons, were included in this study. In total, 103 patients-56 men and 47 women-were enrolled in the study and consecutively separated into two groups of different ages: 18-60 years old (group A) and above 60 years old (group B). The volumetric bone density expressed in HU values was measured with sacral levels of S1, S2 and S3. Apart from the bodies of sacral vertebrae S1-S3, our measurements involved the ala of the ilium in the vicinity of the sacroiliac joint and the wing of the sacrum. All the measurements were performed on the pathway of presumptive iliosacral screws to stabilize the sacroiliac joint. Results: In group A (58 patients) the highest bone density in sacral bodies was found in S1 that gradually decreased to S3, while the opposite tendency was demonstrated in the ala of ilium. The HU values in the wing of the sacrum did not display statistical significance. In group B (45 patients), the highest bone density was also found in the sacral body S1 that decreased toward S3 but in the ala of ilium, the highest bone density was found with level S1 and lowest with level S2. In both groups, the highest bone density referred to the wing of the sacrum. Conclusion: While the perfect construct for posterior pelvic ring fixation remains unclear, our findings may imply that sacroiliac joint screws inserted into the wing of the sacrum of greater bone density could provide much more successful fixation in comparison to those anchored in the body of sacral vertebra of lesser bone density.

Operative management of sacroiliac joint dislocation in children with unstable pelvic fractures - A STROBE-compliant investigation

Objective

Injuries involving severe spinal axial loading may be accompanied by sacroiliac joint dislocations. In children, these injuries are relatively rare, and there is little information on their optimal management in young patients. We conducted a multicentre study to investigate the outcome of surgical treatment of unstable pelvic fracture with sacroiliac joint dislocation in children.

Patients & methods

We assessed the quality of surgical reduction and functional outcome at follow-up in 7 patients (5 girls, 2 boys) with a median age of 6.4 years (range: 4.2-14.8 years). Patients with pelvic fractures and sacroiliac joint dislocations were treated at four international paediatric level 1 trauma centres between January 2008 and August 2023. We applied the Matta criteria to assess the quality of fracture reduction and graded the functional follow-up results using adjusted Majeed score.

Results

At follow-up, 3 patients showed excellent fracture reduction, with 2 patients showing good reduction and 2 patients exhibiting fair fracture reduction according to the Matta criteria. At follow-up visits at a median of 12 months (range: 3-84 months) after the injury, patients achieved a median adjusted Majeed score of 76 (range: 63 to 76).

Conclusions

Unstable pelvic injuries with sacroiliac joint dislocation without comminution can be stabilised with a single iliosacral screw in children. Comminuted pelvic fractures with unstable sacroiliac dislocation require stabilisation with lateral compression screws or plates. In case of residual pelvic instability after internal fixation, an additional external fixator or pelvic hammock should be applied to optimize the stability of fixation.

Pelvic Ring Fractures: A Biomechanical Comparison of Sacral and Lumbopelvic Fixation Techniques

BACKGROUND CONTEXT

Pelvic ring fractures are becoming more common in the aging population and can prove to be fatal, having mortality rates between 10% and 16%. Stabilization of these fractures is challenging and often require immediate internal fixation. Therefore, it is necessary to have a biomechanical understanding of the different fixation techniques for pelvic ring fractures.

METHODS

A previously validated three-dimensional finite element model of the lumbar spine, pelvis, and femur was used for this study. A unilateral pelvic ring fracture was simulated by resecting the left side of the sacrum and pelvis. Five different fixation techniques were used to stabilize the fracture. A compressive follower load and pure moment was applied to compare different biomechanical parameters including range of motion (contralateral sacroiliac joint, L1-S1 segment, L5-S1 segment), and stresses (L5-S1 nucleus stresses, instrument stresses) between different fixation techniques.

RESULTS

Trans-iliac-trans-sacral screw fixation at S1 and S2 showed the highest stabilization for horizontal and vertical displacement at the sacral fracture site and reduction of contralateral sacroiliac joint for bending and flexion range of motion by 165% and 121%, respectively. DTSF (Double transiliac rod and screw fixation) model showed highest stabilization in horizontal displacement at the pubic rami fracture site, while the L5_PF_W_CC (L5-Ilium posterior screw fixation with cross connectors) and L5_PF_WO_CC (L5-Ilium posterior screw fixation without cross connectors) showed higher rod stresses, reduced L1-S1 (approximately 28%), and L5-S1 (approximately 90%) range of motion.

CONCLUSIONS

Longer sacral screw fixations were superior in stabilizing sacral and contralateral sacroiliac joint range of motion. Lumbopelvic fixations displayed a higher degree of stabilization in the horizontal displacement compared to vertical displacement of pubic rami fracture, while also indicating the highest rod stresses. When determining the surgical approach for pelvic ring fractures, patient-specific factors should be accounted for to weigh the advantages and disadvantages for each technique.

Specifying the Starting Point for S1 Iliosacral Screw Placement in the Dysmorphic Sacrum

BACKGROUND

Sacral dysmorphism is not uncommon and complicates S1 iliosacral screw placement partially because of the difficulty of determining the starting point accurately on the sacral lateral view. We propose a method of specifying the starting point.

METHODS

The starting point for the S1 iliosacral screw into the dysmorphic sacrum was specifically set at a point where the ossification of the S1/S2 intervertebral disc (OSID) intersected the posterior vertebral cortical line (PVCL) on the sacral lateral view, followed by guidewire manipulation and screw placement on the pelvic outlet and inlet views. Computer-simulated virtual surgical procedures based on pelvic computed tomography (CT) data on 95 dysmorphic sacra were performed to determine whether the starting point was below the iliac cortical density (ICD) and in the S1 oblique osseous corridor and to evaluate the accuracy of screw placement (with 1 screw being used, in the left hemipelvis). Surgical procedures on 17 patients were performed to verify the visibility of the OSID and PVCL, to check the location of the starting point relative to the ICD, and to validate the screw placement safety as demonstrated with postoperative CT scans.

RESULTS

In the virtual surgical procedures, the starting point was consistently below the ICD and in the oblique osseous corridor in all patients and all screws were Grade 1. In the clinical surgical procedures, the OSID and PVCL were consistently visible and the starting point was always below the ICD in all patients; overall, 21 S1 iliosacral screws were placed in these 17 patients without malpositioning or iatrogenic injury.

CONCLUSIONS

On the lateral view of the dysmorphic sacrum, the OSID and PVCL are visible and intersect at a point that is consistently below the ICD and in the oblique osseous corridor, and thus they can be used to identify the starting point.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Upper sacral segment fixation with converging iliosacral screws: A technical trick for preoperative planning and case series

INTRODUCTION

There are some situations where pelvic surgeons may want to place iliosacral screws with differing trajectories (Sacroiliac and Sacral styles) but may not be able to because of overlapping trajectories.

HYPOTHESIS

Sacroiliac and Sacral style screws can be placed in S1 in select patients by using a preoperative planning technique off the 3D reconstructed surface rendered preoperative CT scan.

MATERIALS/METHODS

Retrospective review of all patients receiving iliosacral screws using the described technique.

RESULTS

Six patients received iliosacral screws using the described technique. When the preoperative planning technique demonstrated feasibility, all screws were able to be safely placed.

DISCUSSION

Placing Sacroiliac and Sacral style screws within S1 may be ideal in some injury patterns. The described technique allows pelvic surgeons facile in iliosacral screw techniques to preoperatively plan for this construct.

LEVEL OF EVIDENCE

VI; Retrospective case series.

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.

Trends in non-operative management of low-energy pelvic fracture: An analysis of the Nationwide Inpatient Sample

Introduction

Non-operative management is common for low-impact pelvic fractures. In this study, we characterize the epidemiology of those treated nonoperatively following low-energy pelvic fracture, while identifying recent management trends.

Methodology

Data from the Nationwide Inpatient Sample (NIS) database from 2011 to 2018 were analyzed. We identified adult patients diagnosed with pelvic fracture based on International Classification of Diseases (ICD) codes, excluding fractures of the acetabulum, femur, polytrauma, and open fractures to isolate cases caused by low-impact mechanisms. Codes indicating operative management were excluded. Demographic information and outcomes (length of stay, in-hospital mortality, hospital discharge status) were collected. Sub-analyses were performed to identify trends.

Findings

123,936 eligible patients were identified. The average age was 68.7 years. 70% were female, showing a decline from 75% to 66% over the study period. Pubic bone involvement was observed in 59% of fractures. The mean Charlson Comorbidity Index (CCI) was 3.83, corresponding to a 10-year survival rate of 58.5%, which remained relatively stable throughout the study period. 62.4% of patients received treatment at urban teaching hospitals. Average length of hospital stay was 6.3 days. Discharge to a skilled nursing facility (SNF) was the most common outcome, ranging from 62.1% to 65.0% during the study period, while 20.0% of patients were discharged home (18.4%-21.1%). Mean in-hospital mortality was 3.28%, showing no significant change, with higher rates among male patients (5.1%) and patients of Asian descent (3.8%).

Conclusion

The majority of patients receiving nonoperative treatment for low-energy pelvic fractures were females in their mid-60s with moderate comorbidity. The study reveals a relatively high in-hospital mortality rate of 3.28%, particularly among male patients and those of Asian descent, indicating the need for increased surveillance for further injury in these groups. Most patients were discharged to a SNF, highlighting the necessity for extended rehabilitation in this population. This persistent trend is noteworthy considering the growing emphasis on the cost of inpatient admissions and advancements in outpatient management of orthopedic injuries.

Contemplate iliosacral screw in patients with developmental dysplasia of the hip

OBJECTIVES

Our aim in the study was evaluating sacroiliac morphology in patients with DDH and its possible effect on appropriate iliosacral screw fixation.

DESIGN

Retrospective cohort study.

SETTING

Level of evidence 3.

PATIENTS/PARTICIPANTS

We evaluated the anteroposterior pelvis X-ray and pelvic CT scans of patients. We mainly divided the patients into two groups: DDH group (n:105) and control group (n:105).

INTERVENTION

The presence of the five qualitative characteristics of sacral dysplasia evaluated according to Route in both groups. The DDH group was divided into four subgroups according to the degree of hip dysplasia.

MAIN OUTCOME MEASUREMENT

The cross-sectional area, length of the osseous corridor, coronal and vertical angulation evaluated in both groups.

RESULTS

The DDH group also exhibited a significantly higher S1 coronal and axial angulation, lower S1 cross-sectional area and S1 iliosacral screw length than the control group (p:0.033, p:0,002, p:0.006, p:0,019, respectively). According to the Rout classification, 9% were normal, 31% transient, 58% dysplastic in the DDH group. 45.7% were normal, 38% transient, 17% dysplastic in the control groups. These differences between the groups were statistically significant (p < 0.001). When the DDH groups were evaluated within themselves; no statistically significant difference was observed in S1 and S2 cross-sectional area, S1 and S2 maximum estimated iliosacral screw length, S1 and S2 axial and coronal angles assessment.

CONCLUSION

Sacral dysplasia was more common, narrower and more angled osseous canal for the iliosacral screw was found in the DDH group. There was no relation between the degree of hip dysplasia and sacrum morphology in the DDH group. Thus, we suggest the surgeons be aware of iatrogenic injury even in constrained dysplastic hips.

Biomechanical analysis of pelvic holding pathways and strategies for use of the steinmann pin in pelvic fracture reduction

Pelvic fracture is the most serious bone trauma and has the highest mortality and disability rate. Surgical treatment of pelvic fracture is very challenging for surgeons. Minimally invasive close reduction of pelvic fracture is considered the most difficult operation due to the complex pelvic morphology and abundant soft tissue anatomy, both of which increase the difficulty of pelvic fracture reduction. The most challenging aspect of such surgery is how to hold the pelvic bone and effectively transmit the reduction force to the bone. Therefore, a safe and effective pelvic holding pathway for reduction is necessary for pelvic fracture operations. Existing research on the pelvic holding pathway addresses anatomical position and dimension. Few studies have focused on biomechanical properties or on surgical techniques related to these pathways. This paper studies the three holding pathways that are most commonly used in clinical practice. The most effective force direction for each holding pathway is identified through finite element modeling. Pathway 1 is suitable for internal rotation operation and open/close-book operation of the pelvis; Pathway 2 is suitable for translation of the fractured pelvis toward the sacrum and internal pelvic rotation operations; Pathway 3 is suitable for pulling and lifting of the fractured pelvis against gravity and open/close-book operation of the pelvis. In addition, we find through our simulation that the use of a combined holding strategy can reduce the reduction force during the reduction process. We compared the performances of the 2-pin combined holding strategy (2P-CH) and the 3-pin combined strategy (3P-CH). During translational reduction, 2P-CH and 3P-CH showed little difference in pelvic reduction force. However, in rotational reduction, 3P-CH shows advantages. It has less reduction force and the least combined muscle resistance. It can also maximize the displacement of the iliac crest under the same conditions. The results of this study can be applied to surgical planning and to the development of robot-assisted surgery systems in selecting holding pathways and operation strategies for fractured pelvis.

Prospective Characterization of Pain and Function in Patients With Unstable Pelvic Fractures Treated With Posterior Screw Fixation

OBJECTIVES

Describe patient-reported pain and function within 24 months of a pelvic fracture treated with posterior screw fixation and identify factors associated with increased pain.

DESIGN

Prospective case series.

SETTING

Academic trauma center.

PATIENTS/INTERVENTION

Eighty-eight patients with adult pelvic fracture treated with sacroiliac or transiliac screws.

MAIN OUTCOME MEASURES

Average pain measured with the Brief Pain Inventory (BPI); function measured with the Majeed Pelvic Outcome Score from 6 to 24 months postinjury.

RESULTS

The mean pain from 6 to 24 months postinjury was 2.22 on the 10-point BPI scale (95% CI, 0.64-3.81). Sixty-nine patients (78.4%) reported mild to no pain at 6 months; 12 (13.6%) patients had severe pain. Two years after injury, 71 patients (80.6%) exhibited mild to no pain. Within 24 months of injury, the mean pelvic function was 71 on the 100-point Majeed scale (95% CI, 60-82). Half of the sample (n = 44) had good to excellent pelvis function by 6 months postinjury; 55 patients (62.5%) attained this level of function by 24 months. A history of chronic pain (1.31; 95% CI, 0.26-2.37; P = 0.02), initial fracture displacement (≥5 mm) (0.99; 95% CI, 0.23-1.69; P = 0.01), and socioeconomic deprivation (0.28; 95% CI, 0.11-0.44; P < 0.01) were significantly associated with increased pain.

CONCLUSION

Our findings suggest that most patients with unstable pelvic ring fractures treated with posterior screw fixation achieve minimal to no pelvis pain and good to excellent pelvic function 6-24 months after injury.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The surgical management of highly unstable fragility fractures of the sacrum with spinopelvic dissociation: A case series and proposal of a surgical treatment algorithm

INTRODUCTION

U- and H-shaped fragility fractures of the sacrum (FFP IVb) are unstable fractures. Non-operative treatment may be associated with impaired walking abilities, chronic pain and the potential loss of independency. However, different treatment options are still controversially debated. The aim of surgical treatment includes sufficient fracture stability for immediate full weight bearing and good pain control postoperatively. A new surgical treatment algorithm was developed. This algorithm was evaluated in a cohort of geriatric patients with FFP type IVb regarding surgical complications and patient-related outcome.

METHODS

Retrospective case series. Patients ≥65 years, admitted with FFP IVb between 01/2017 and 12/2020 were included. Pelvic CT was performed and the surgical technique was chosen according to the proposed surgical treatment algorithm. For this algorithm, the technique of fracture stabilisation was adapted to sacral anatomy and the specific fracture pattern to minimize the impact of surgery and postoperative complications without compromising a sufficient fracture stability. Pain levels, complications and surgical revisions were recorded. Level of independency, walking abilities and -aids were compared 3- and 12- months postoperatively to the pre-injury situation.

RESULTS

Twenty-three patients were included. Outcome parameters could be obtained in 20 patients (85%) after three months and in 18 patients (78%) patients one year postoperatively. All patients were treated according to the algorithm. Sixteen patients received two transilio-transsacral screws (TI-TSS), whereas either lumbopelvic fixation (LPF) combined with a TI-TSS or bilateral ilio-sacral screws (ISS) was performed four times. Three patients underwent bilateral ISS into S1 with one TI-TSS into S2. Three days postoperatively, median pain VAS was 2 (0-8) compared to 7 (4-10) before surgery. One loosened TI-TSS was removed six weeks postoperatively. Three-month mortality was 14% (n=3). At one-year follow-up, all patients regained their pre-injury level of walking abilities.

CONCLUSIONS

Restoration of walking abilities, preservation of independency and efficient pain control can be achieved with surgical fixation of FFP type IVb fractures. With the proposed surgical algorithm, the fixation techniques are adapted to the fracture pattern to minimize the surgical burden.

LEVEL OF EVIDENCE

IV.

Percutaneous iliosacral screw insertion with only outlet and inlet fluoroscopic view for unstable pelvic ring injuries: Clinical and radiological outcomes

Background:

Percutaneous iliosacral screw fixation in posterior pelvic ring fractures is challenging and commonly performed under fluoroscopy or navigation techniques. This study aimed to assess the safety and efficacy of percutaneous iliosacral screw implantation under fluoroscopy guidance with only inlet and outlet views.

Methods:

This retrospective study included 58 consecutive unstable posterior pelvic injury patients (36 sacral fractures and 22 sacroiliac joint disruptions) treated with percutaneous iliosacral screws between January 2015 and November 2019. Acceptable inlet radiographs show the anterior cortex of the S1 body superimposed on the S2 body. Acceptable outlet radiographs show the superior pubic symphysis at the level of the S2 foramen and visualize the S1 and S2 sacral foramina. In our technique, the screw was inserted at the inferior half of the outlet view and the posterior half of the inlet view. The time needed for screw insertion and the radiation exposure time was recorded. Intra and postoperative complications were documented. Postoperative computed tomography (CT) scans assessed screw position.

Results:

In total, 69 iliosacral screws were inserted in 58 patients. In postoperative CT scans, the screw position was assessed, 89.8% were in a secure position, and 10.2% had malposition. The mean operation time per screw was 21.18 min and the mean fluoroscopy time per screw was 112 s. There was no evidence of wound infection or iatrogenic neurovascular injury. No reoperation was performed.

Conclusion:

Percutaneous iliosacral screws can be placed using the only outlet and inlet fluoroscopic views with comparable radiological and clinical outcomes to the conventional method.

A clinical and biomechanical comparison of INFIX plus single versus double sacroiliac screw fixation for unstable pelvic ring injury

BACKGROUND

The aim of this study is to compare the clinical and biomechanical outcome of INFIX plus single with two sacroiliac screw fixation for unstable pelvic fractures of Type C.

METHODS

Sixteen cadavers were randomly subjected to INFIX plus single or double sacroiliac screw fixations and then mounted onto the ElectroForce loading machine under different vertical loads. To investigate the clinical outcomes of the two techniques, nineteen patients were retrospectively analyzed. The main outcome measures were postoperative radiographic reduction grading (using the Tornetta and Matta grading system), functional outcome (using the Majeed scoring system), and incidence of complications.

RESULTS

In the biomechanical study, INFIX plus double sacroiliac screw fixation showed better biomechanical stability than fixation with a single sacroiliac screw (p < 0.05). In our clinical case series, all 19 patients had bony union 6 months after the operation. INFIX plus double sacroiliac screw fixation also demonstrated a better functional outcome and a higher radiographic satisfactory rate than INFIX plus single sacroiliac screw fixation (79.25 ± 5.47; 91.33 ± 4.97; p < 0.05), (77.78% vs. 60%; p = 0.05). One patient in INFIX plus single-screw fixation group had screw loosening at 6-month follow-up postoperatively. One case in each group suffered heterotopic ossification and the lateral femoral cutaneous nerve paralysis, and one patient suffered from infection.

CONCLUSION

INFIX plus double sacroiliac screw fixation demonstrated more stability in cadaveric biomechanical analysis and better clinical outcomes than INFIX plus single sacroiliac screw fixation.

Minimally Invasive Percutaneous TightRope® System Fixation for an Unstable Posterior Pelvic Ring: Clinical Follow-up and Biomechanical Studies

Objective

To evaluate the mechanical stability and clinical efficacy of minimally invasive percutaneous TightRope® systems applied via gun‐shaped reduction forceps for unstable posterior pelvic ring fractures.

Materials and methods

This study consists of two parts: a clinical retrospective study and a randomized controlled biomechanical test. For the clinical study, a retrospective analysis of posterior pelvic ring fractures was performed between June 2015 and May 2020. Eighteen patients underwent surgery using two TightRope® systems to fix a broken posterior pelvic ring because of unstable AO type C1 and C2 pelvic ring fractures. The patients were followed up for at least 2 years, and all patients were evaluated using the Majeed scoring system and vertical displacement. In the biomechanical tests, six embalmed adult pelvic specimens were used. The fractures were subjected to TightRope®, IS screw, and TBP fixation in a randomized block design. The specimens were placed in a biomechanical testing machine in a standing neutral posture. A cyclic vertical load of up to 500 N was applied, and the displacement of the specimens was recorded by the testing machine. The ultimate load in each group of specimens was recorded. The displacement and ultimate load were compared and analyzed by statistical methods.

Results

At a mean follow‐up of 38.89 ± 8.72 months, the functional Majeed score was excellent in 14 patients and good in four patients. The final radiological examinations showed that the outcome was excellent in 14 patients and good in four patients. In these patients, no serious clinical complications were found. Weight‐bearing was delayed in four patients. In biomechanical tests, the displacement of the specimens fixed with TightRope® was significantly lower than that of the specimens fixed with TBP (P < 0.05) when the load ranged from 300 to 500 N. The displacement in the IS screw group was significantly lower than that in either the TBP or TightRope® group (P < 0.05) when the load ranged from 0 to 500 N. The ultimate load in the IS screw group (1798 ± 83.53 N) was significantly greater than that in the TBP group (1352 ± 74.41 N) (t = 9.78, P < 0.0001) and the TightRope® group (1347 ± 54.28 N) (t = 11.11, P < 0.0001). However, no significant difference was observed between the TightRope® and TBP groups (t = 0.13, P = 0.90).

Conclusion

Percutaneous posterior TightRope® system shows strong stability in mechanical experiments and shows good results in clinical follow‐up while this system has certain advantages in lower surgical requirements and lower risk of related nerve and vascular structural damage.

Differences in Accuracy and Radiation Dose in Placement of Iliosacral Screws: Comparison between 3D and 2D Fluoroscopy

Percutaneous iliosacral screw fixation is a widely accepted method of stabilizing the posterior pelvic ring. Recently developed tools such as 3D-navigated fluoroscopy and computed navigation seem to prevent a surgeon from conducting screw misplacement. The study aimed to comparatively assess the introduction of sacroiliac screw placement using 2D and 3D fluoroscopy in terms of accuracy and radiation exposure. Iliosacral screws were introduced in 37 patients using 2D (group N1) and in 36 patients using 3D fluoroscopy (group N2) techniques. Overall, 61 and 56 screws were introduced in groups N1 and N2, respectively. Screw placement accuracy was assessed using postoperative computed tomography and Smith’s scale. Intraoperative radiation exposure was also assessed. No differences were noted between groups in terms of screw positioning accuracy and radiation dose. Both 2D and 3D fluoroscopy provide good visualization for safely placing percutaneous iliosacral joint screws. Using 3D fluoroscopy-based navigation in comparison with 2D fluoroscopy is not advantageous.

What's old is best again Is anterior plating best for fixation of type-C pelvic fractures? A systematic review and meta-analysis

BACKGROUND

Type-C pelvic fractures are a rare but potentially fatal injury that often leads to poor outcomes, despite surgical fixation. Many fixation methods are used but the optimal method remains contentious, with failure and complications common. This study compared outcomes for each fixation method.

METHODS

A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). A search of studies which reported on outcomes after surgically treated type-C pelvic fractures was undertaken. Data retrieved included fixation method, length of follow up, surgical revision, and complications rates (hardware breakage, post-operative outcomes, screw mal-positioning, screw loosening, loss of reduction and infection). Study quality was assessed using the Methodological Index for Non-Randomised Studies (MINORS). Pooled revision, outcome and complication rates were calculated using a quality-adjusted model in MetaXL 5.3.

RESULTS

Fifty-two studies met the inclusion criteria representing 1567 patients and 7 fixation methods. The meta-analyses demonstrated high rates of 'less-than-good' outcomes for most fixation methods, with a higher rate for bilateral injuries (overall 23%; unilateral 21% v bilateral 41%). The mean pooled rate for surgical revision rate was 4%, hardware breakage 3%, screw mal-positioning 2%, screw loosening 3%, loss of reduction 5% and infection 4%. Each fixation method had different performance profiles; however, anterior plating outperformed all other fixation methods for patient outcomes, with a 'less-than-good' rate of just 7% vs the pooled mean of 23% and demonstrated at or below pooled mean rates for all complications except revision which was 5%.

CONCLUSIONS

Post-operative outcomes for surgically treated type-C pelvic fractures revealed a 'less-than-good' pooled outcome rate of 23% and a revision rate of 4%. Anterior plates outperformed most other systems particularly for patient reported outcomes. Pooled revision, patient-reported outcome and complication rates for type-C pelvic fractures have not previously been reported and these data provide a benchmark for practice and future research.

Does Cement Augmentation of the Sacroiliac Screw Lead to Superior Biomechanical Results for Fixation of the Posterior Pelvic Ring? A Biomechanical Study

Background and Objectives: The stability of the pelvic ring mainly depends on the integrity of its posterior part. Percutaneous sacroiliac (SI) screws are widely implanted as standard of care treatment. The main risk factors for their fixation failure are related to vertical shear or transforaminal sacral fractures. The aim of this study was to compare the biomechanical performance of fixations using one (Group 1) or two (Group 2) standard SI screws versus one SI screw with bone cement augmentation (Group 3). Materials and Methods: Unstable fractures of the pelvic ring (AO/OTA 61-C1.3, FFP IIc) were simulated in 21 artificial pelvises by means of vertical osteotomies in the ipsilateral anterior and posterior pelvic ring. A supra-acetabular external fixator was applied to address the anterior fracture. All specimens were tested under progressively increasing cyclic loading until failure, with monitoring by means of motion tracking. Fracture site displacement and cycles to failure were evaluated. Results: Fracture displacement after 500 cycles was lowest in Group 3 (0.76 cm [0.30] (median [interquartile range, IQR])) followed by Group 1 (1.42 cm, [0.21]) and Group 2 (1.42 cm [1.66]), with significant differences between Groups 1 and 3, p = 0.04. Fracture displacement after 1000 cycles was significantly lower in Group 3 (1.15 cm [0.37]) compared to both Group 1 (2.19 cm [2.39]) and Group 2 (2.23 cm [3.65]), p ≤ 0.04. Cycles to failure (Group 1: 3930 ± 890 (mean ± standard deviation), Group 2: 3676 ± 348, Group 3: 3764 ± 645) did not differ significantly between the groups, p = 0.79. Conclusions: In our biomechanical setup cement augmentation of one SI screw resulted in significantly less displacement compared to the use of one or two SI screws. However, the number of cycles to failure was not significantly different between the groups. Cement augmentation of one SI screw seems to be a useful treatment option for posterior pelvic ring fixation, especially in osteoporotic bone.

Percutaneous Robot-Assisted versus Freehand S2 Iliosacral Screw Fixation in Unstable Posterior Pelvic Ring Fracture

OBJECTIVES

To assess the efficiency, safety, and accuracy of S₂ (IS) screw fixation using a robot-assisted method compared with a freehand method.

METHODS

This is a retrospective clinical study. We analyzed the patients treated with S₂ IS screw fixation for unstable pelvic fractures from January 2016 to January 2019 in our institution. Sixty-three patients (17 men and 46 women) aged between 21 and 55 years (with an average age of 39.22 ± 9.28) were included in this study. According to the Tile classification, there were 26 (41.3%) type B fractures and 37 (58.7%) type C fractures. All patients were divided into robot-assisted (RA) group (38 patients) or the traditional freehand (FH) group (25 patients). In RA group, the S₂ IS screws were implanted with a robot-assisted technique. And S₂ IS screws were implanted with a traditional freehand technique in FH group. The screw-related complications were recorded during and after the surgery. The position of all screws and fracture reduction was assessed by postoperative CT scans according to the Gras classification. The number of guide wire attempts and the radiation exposure for S₂ screw implantation during operation were also recorded. Finally, the Matta standard was used to evaluate the fracture reduction of the IS joint.

RESULTS

A total of 89 IS screws were implanted into S2 iliosacral joint. Fifty-four screws were placed by RA (38 patients) and 35 screws were by FH (25 patients). There was no difference between the two groups with respect to demographic data. There was no screw-related complications or revision surgery in any group. In terms of screw placement, the excellent and good rate was 100% in the RA group, better than that in the FH group where it was only 85.7% (P < 0.001). The fluoroscopy time was 8.06 ± 3.54 s in RA group, which was much less than that in the FH group (27.37 ± 8.82 s, P < 0.001). The guide wire attempts in the RA group (0.685 ± 0.820) were much less than those in the FH group (5.77 ± 3.34) (P < 0.001). Both the fluoroscopy time per screw and the number of guide wire attempts in the RA group were much less than those in the FH group (P < 0.001). The overall postoperative excellent and good rate of Matta standard in RA and FH groups were 86.8% (34/4) and 90.0% (23/25), respectively (P = 0.750), and there was no statistical difference.

CONCLUSION

The robot-assisted surgery is an accurate and minimally invasive technique. S₂ IS screw implantation assisted by TiRobot to treat the posterior pelvic ring fractures, have a high success rate than the freehand technique. Percutaneous RA S₂ IS screw fixation for unstable posterior pelvic ring injuries is safe and clinically feasible and has great clinical application value.

Iliosacral screw corridors in Japanese subjects: a study using reconstruction CT scans

Objectives:

To investigate the characteristics of iliosacral (IS) screw corridors of Japanese pelves.

Methods:

Computer tomography images of 42 adult Japanese subjects without any pelvic injury were analyzed at a workstation. Using the manual reconstruction function, the width of a simulated horizontal corridor for an IS screw on the true coronal and true axial planes in the upper (S1), second (S2), and the third (S3) sacral segments was measured. For pelves without an adequate S1 corridor, a cranially tilted corridor was sought. A corridor was defined as “adequate” if its width on both planes was 10 mm or more.

Results:

An adequate horizontal corridor was found in S1 in 17 (40.5%) subjects, in S2 in 29 (69.0%) subjects, and in S3 in no subject. An independent factor affecting the adequacy of the S1 corridor was the adequacy of the S2 corridor (OR: 0.09). Similarly, an independent factor affecting S2 adequacy was S1 adequacy (OR: 0.10). A tilted, 10 mm diameter corridor was found in all 25 subjects who did not have an adequate horizontal corridor in the S1 segment. The angle required to obtain a 10 mm diameter corridor inversely correlated with the diameter of a horizontal corridor on the true coronal plane (R = −0.713, P = .000).

Conclusions:

The characteristics of IS screw corridors in the 42 Japanese subjects were similar to those reported in previous studies conducted in the West. The importance of preoperative planning using reliable techniques, such as three-dimensional reconstruction, should be emphasized.

Level of evidence: Diagnostic Level III. See Instructions for Authors for a complete description of level of evidence.

One sacroiliac screw for posterior ring fixation in unstable pelvic fractures

Unstable pelvic injuries are considered uncommon and they are usually associated with high rate of morbidity and mortality. High energy blunt trauma and falling from height are usually the main mechanism of injury. It is a retrospective study that was performed in academic level I trauma center. From September 2015 to December 2019, a consecutive series of 26 patients (7 females), with average age of 32 years with unstable pelvic fracture were included in this study. All patients underwent reduction and percutaneous fixation with one sacroiliac screw posteriorly for each sacroiliac joint and anterior arch fixation of the pelvic ring with either platting or external fixator. The average duration of follow up was 36 months. Clinical results: at the final follow-up, all patients had complete radiological healing of the fractures. The subjective functional assessment yielded excellent for twenty-two patients, good for two patients and fair for two patients. Posterior arch fixation of the pelvic ring with one sacroiliac screw beside anterior arch fixation in unstable fracture pelvis is a sufficient fixation method to maintain the requiring stability to allow complete union of the fracture. Level of Evidence: Therapeutic Level III.

Three-dimensional morphometry of the first two sacral segments and its impact on safe transiliac-transsacral screw placement

INTRODUCTION

Percutaneous screw fixation of the posterior pelvic ring is a popular technique to treat unstable pelvic ring lesions. This technique is practicable in both, the high-energy pelvic ring fractures, mostly in the young population as well as the osteoporotic fractures in the elderly. Risk of the transiliac-transsacral screw positioning is that the critical area of nerve root exit has to be passed twice. For secure screw placement, without causing iatrogenic neurovascular injuries, the knowledge of distances to the narrowest areas is essential. Purpose of this anatomical study was to examine the optimal intraosseous screw placement for the first two sacral segments.

MATERIAL/METHODS

Images of uninjured pelves from 50 patients (64-line CT scanner) were evaluated. Then virtual transiliac-transsacral srews were positioned into the first two sacral segments. The distance from the screws' entrance points at the ilium's alar bone to the narrowest portion of the whole pedicle as well as the height and width in this area were measured. Descriptive statistics were used and gender related differences were evaluated using student T-test.

RESULTS

For the first sacral segment the distance to the narrowest zone amounted in mean 62.75 mm, respectively 63.31 mm, depending on the selected way of measurement. For the second segment the mean distance to the neuroforamina was on average 50.61 mm, respectively 51.54 mm. The average height in S1 measured 25.88 mm and the average width 25.49 mm. The average height for S2 was 17.54 mm and the average width 17.61 mm. We could not find any statistically significant gender correlation for the measured distances.

CONCLUSION

Results of this anatomical study may help in performing a safe surgical procedure.

Superior gluteal artery injury risk from third sacral segment transsacral screw insertion

OBJECTIVES

Iliosacral (IS) and transsacral (TS) screws are commonly used to stabilize pelvic ring injuries. The course of the superior gluteal artery (SGA) can be close to implant insertion paths. The third sacral segment (S3) has been described as a viable osseous fixation pathway (OFP) but the proximity of the SGA to the S3 screw path is unknown.

METHODS

Fifty uninjured patients with contrasted pelvic computed tomograms (CTA) were identified with an S3 path large enough for a 7.0 mm TS screw. Starting sites for S1 IS or TS, S2 and S3 TS screws were located on the volume rendered lateral CTA image and transferred onto the surface rendered 3D CTA with the SGA clearly visible. The distance from screw start sites to the SGA was measured. A distance less than 3.5 mm was considered likely for injury.

RESULTS

The average distances from screw start sites to the SGA were 23.0 ± 7.9 mm for S1 IS screws, 14.3 ± 6.4 mm for S2 TS screws and 25.9 ± 6.5 mm for S3 TS screws. No S1 IS screws, 5 S2 TS screws (10%), and no S3 TS screws were projected to cause injury to the SGA.

CONCLUSIONS

The osseous start site and soft tissue path for an S3 TS screw is remote from the SGA. The S1 IS and S3 TS pathways are further away from the SGA while the S2 TS pathway is closer and may theoretically pose a higher injury risk in patients with an available S3 OFP.

Pelvic antropometric measurement in 3D CT for placement of two unilateral iliosacral S1 - 7.3 mm screws

PURPOSE

Stability of the dorsal pelvic ring is important for patient mobilisation and can be restored using several surgical procedures after fracture. Placement of percutaneous iliosacral screws is a reliable and minimal-invasive technique to achieve stabilisation of the dorsal pelvic ring by placement of two screws in the first sacral vertebra. Aim of this study was to evaluate 3D CT scans regarding the anatomical possibility to place two 7.3 mm iliosacral screws for fixation of the dorsal pelvic ring.

METHODS

3D CT datasets of 500 consecutive trauma patients with 1000 hemipelves of a mid-european level I trauma centre with or without pelvic injury were evaluated and measured bilaterally in this retrospective study.

RESULTS

One thousand hemipelvic datasets of 500 patients (157 females, 343 males) with a mean age of 49.7 years (18 to 95) were included in this study. Only 16 hemipelves (1.6%, 11 in females, 5 in males) in 14 patients (2.8%, 9 females = 5.73%, 5 males = 1.5%) showed too narrow corridors so that 7.3 mm screw placement would not be possible (p = 0.001). In women, too narrow corridors occurred 3.9 times as often as in men. Only two females showed this bilaterally.

CONCLUSION

The evaluation of 3D CT scans of the pelvis showed the importance of planning iliosacral screw placement, especially if two 7.3 mm screws are intended to be placed in the first sacral vertebra.

Screw-in-screw fixation of fragility sacrum fractures provides high stability without loosening-biomechanical evaluation of a new concept

Surgical treatment of fragility sacrum fractures with percutaneous sacroiliac (SI) screw fixation is associated with high failure rates. Turn-out is detected in up to 20% of the patients. The aim of this study was to evaluate a new screw-in-screw implant prototype for fragility sacrum fracture fixation. Twenty-seven artificial hemipelvises were assigned to three groups (n = 9) for instrumentation of an SI screw, the new screw-in-screw implant prototype, ora transsacral screw. Before implantation, a vertical osteotomy was set in zone 1 after Denis. All specimens were biomechanically tested to failure in upright position. Validated setup and test protocol were used for complex axial and torsional loading applied through the S1 vertebral body to promote turn-out of the implants. Interfragmentary movements were captured via optical motion tracking. Screw motions were evaluated by means of triggered anteroposterior X-rays. Interfragmentary movements and implant motions were significantly higher for SI screw fixation compared to both transsacral and screw-in-screw fixations. In addition, transsacral screw and screw-in-screw fixations revealed similar construct stability. Moreover, screw-in-screw fixation successfully prevented turn-out of the implant that remained during testing at 0° rotation for all specimens. From biomechanical perspective, fragility sacrum fracture fixation with the new screw-in-screw implant prototype provides higher stability than an SI screw, being able to successfully prevent turn-out. Moreover, it combines the higher stability of transsacral screw fixation with the less risky operational procedure of SI screw fixation and can be considered as their alternative treatment option.

Corridor-diameter-dependent angular tolerance for safe transiliosacral screw placement: an anatomic study of 433 pelves

BACKGROUND

The purpose of this study was to determine the angular tolerance of the S1 and S2 segments to accommodate a transiliosacral screw across both sacroiliac joints.

HYPOTHESIS

We hypothesized that the angular tolerance for transiliosacral screw placement would be more constrained than the angular tolerance for iliosacral fixation in pelves where a safe osseous corridor was measured.

MATERIALS AND METHODS

The cortical boundaries of the S1 and S2 sacral segments in 433 pelvic CTs were digitally mapped. A straight-line path was placed within each osseous corridor and extended across both SI joints past the outer iliac cortices. The diameter of the path was increased until it breached the cortex, geometrically determining maximum diameter (Dmax). Angular tolerance for screw placement was calculated with trigonometric analysis of the Dmax value of the corridor, and the average distance from the termination of the osseous corridor to the site of percutaneous insertion. Gender, age, and BMI were evaluated as independent predictors using binomial logistic regression.

RESULTS

The transiliosacral angular tolerance for the S1 and S2 osseous corridors was 1.53 ± 0.57 degrees and 1.02 ± 0.33 degrees, respectively. 68.9% of S1 corridors and 81.1% of S2 corridors had a safe zone (corridor diameter ≥ 10 mm) for transiliosacral placement, 48.3% of the pelves had a safe zone for both corridors, while 5.1% had no safe zones. Females had a less frequent Dmax ≥ 10 mm at S1, 52% vs 67% (p = 0.001), and at S2, 64% vs 86% (p < 0.001).

DISCUSSION

In conclusion, the angular tolerance of 1.53 and 1.03 degrees for the S1 and S2 segments, respectively, creating a narrow interval for safe passage of the trans-iliac and trans-sacral, with approximately 31.1% of patients not having a viable corridor for screw passage. A correlation exist between S1 and S2 corridors with Dmax ≥ 10 mm and the resulting increase in angular tolerance for safe passage of a transilioscral screw.

LEVEL OF EVIDENCE IV

Level Retrospective Cohort.

Posterior pelvic ring bone density with implications for percutaneous screw fixation

BACKGROUND

Although the second (S2) and third (S3) sacral segments have been established as potential osseous fixation pathways for screw fixation, the S2 body has been demonstrated to have inferior bone density when compared to the body of the first (S1) sacral segment. Caution regarding the use of iliosacral screws at this level has been advised as a result. As transiliac-transsacral screws traverse the lateral cortices of the posterior pelvis, they may be relying on bone with superior density for purchase, which could obviate this concern. The objective of this study was to compare the bone density of the posterior ilium and sacroiliac joint to that of the sacral body at the first (S1), second (S2), and third (S3) sacral levels.

MATERIALS AND METHODS

A retrospective case series was performed, reviewing the CT scans of 100 patients without prior pelvic trauma. Each CT was confirmed to have available osseous fixation pathways at the first (S1), second (S2), and third (S3) sacral segments. The bone density of the posterior ilium/sacroiliac joint (PISJ) and sacral body (SB) was measured using the embedded standardized Hounsfield units (HU) tool at each sacral level.

RESULTS

The average S2 PISJ bone density (320.1) was significantly higher than the S1 (286.5) and S3 (278.9) PISJ (p < 0.0001) and S1 and S3 PISJ was not statistically different. The S1 sacral body bone density (231.1) was significantly higher than the S2 (182.1) and S3 (126.8) bone density (p < 0.0001). The PISJ bone density is greater than the sacral body at every sacral level (p < 0.0001).

CONCLUSION

The S2 PISJ bone density is significantly greater than S1. The S1, S2, and S3 PISJ bone density is greater than the sacral body at all sacral levels, and the S1 body has higher bone density than the S2 and S3 bodies. These differences in bone density may have implications for the stability of posterior pelvic ring fixation constructs with regard to screw purchase.

LEVEL OF EVIDENCE

Level III-Case cohort series.

Bone density of first and second segments of normal and dysmorphic sacra

Background

Iliosacral screw fixation is safe and effective but can be complicated by loss of fixation, particularly in patients with osteopenic bone. Sacral morphology dictates where iliosacral screws may be placed when stabilizing pelvic ring injuries. In dysmorphic sacra, the safe osseous corridor of the upper sacral segment (S1) is smaller and lacks a transsacral corridor, increasing the need for fixation in the second sacral segment (S2). Previous evidence suggests that S2 is less dense than S1. The aim of this cross-sectional study is to further evaluate bone mineral density (BMD) of the S1 and S2 iliosacral osseous pathways through morphology stratification into normal and dysmorphic sacra.

Materials and methods

Pelvic computed tomography scans of 50 consecutive trauma patients, aged 18 to 50 years, from a level 1 trauma center were analyzed prospectively. Five radiographic features (upper sacral segment not recessed in the pelvis, mammillary bodies, acute alar slope, residual S1 disk, and misshapen sacral foramen) were used to identify dysmorphic characteristics, and sacra with four or five features were classified as dysmorphic. Hounsfield unit values were used to estimate the regional BMD of S1 and S2. Student’s t-test was utilized to compare the mean values at each segment, with statistical significance being set at p < 0.05. No change in clinical management occurred as a result of inclusion in this study.

Results

A statistical difference in BMD was appreciated between S1 and S2 in both normal and dysmorphic sacra (p < 0.0001), with 28.4% lower density in S2 than S1. Further, S1 in dysmorphic sacra tended to be 4% less dense than S1 in normal sacra (p = 0.047). No difference in density was appreciated at S2 based on morphology.

Conclusions

Our results would indicate that, based on BMD alone, fixation should be maximized in S1 prior to fixation in S2. In cases where S2 fixation is required, we recommend that transsacral fixation should be strongly considered if possible to bypass the S2 body and achieve fixation in the cortical bone of the ilium and sacrum.

Level of evidence

Level III.

Combined 3D Printed Template to Guide Iliosacral Screw Insertion for Sacral Fracture and Dislocation: A Retrospective Analysis

Objective

To evaluate the accuracy and safety of a combined 3D printed guide template (combined template) to assist iliosacral (IS) screw placement for sacral fracture and dislocation.

Methods

A total of 37 patients, 24 men and 13 women, age from 22 to 68 years old, diagnosed with a sacral fracture and dislocation were involved in this study for retrospective analysis from January 2016 to February 2018. There were 19 patients in the template group (42 screws) and 18 patients in the conventional group (31 screws). In the combined template group, IS screw placement was assisted by a combined 3D printed template; in the conventional group, the IS screws were placed freehand under fluoroscopy. The accuracy of the IS screw placement was evaluated by comparing the screw angle and the location of the screw entry point between the actual and the simulated screw in the combined template group. The safety of the IS screw placement was evaluated by comparing the quality of the reduction, the grading of the screws, the operation time, and radiation exposure times between groups.

Results

A total of 73 pedicle screws were placed in 37 patients: 42 screws (30 S1, 12 S2) in the combined template group and 31 screws (23 S1, 8 S2) in the conventional group. In the conventional group, 1 patient developed symptoms of L5 nerve stimulation. In the combined template group, the average operative time of each screw was 25.01 ± 2.90 min, with average radiation exposure times of 12.05 ± 4.00. In the conventional group, the average operative time of each screw was 46.24 ± 9.59 min, with an average radiation exposure time of 56.10 ± 6.75. There were significant differences in operation and radiation exposure times between groups. The rate of screw perforation was lower in the combined template group (2 of 42 screws, 0 at grade III and 2 at grade II) than in the conventional group (5 of 38 screws, 2 at grade III and 3 at grade III). In the combined template group, the mean distance between the entry points of the actual and simulated screws was 1.4 ± 0.9 mm, with a mean angle of deviation of 2.1° ± 1.6°. All patients were followed up once every 3 months and were followed for 3 to 12 months.

Conclusion

Using the combined template to assist with the insertion of IS screws delivered good accuracy, less fluoroscopy and shorter operation time, and avoided neurovascular injury as a result of screw malposition.

Feasibility of iliosacral screw placement in patients with upper sacral dysplasia

Background

Exact 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.

Methods

Pelvic 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.

Results

The 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%.

Conclusions

The 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.

Anatomical considerations of safe drilling corridor upper sacral segment screw insertion

The upper segment of sacrum is an important for screw insertions of unstable lumbosacral spine. Measurements of the S1-S2 as sacral wings, pedicles, sacral foraminas and sacral canal were taken from 87 sacrums. The mean depths of S1 pedicle and sacral wing were estimated as 25.8 ± 2.3 mm and 50.1 ± 1.7 mm, respectively. Angles screw trajectory of sacral pedicle anteromedial and sacral wing were measured as 29.6 ± 0.9° and 29.7 ± 2.1°, respectively. To avoid injury to the vascular structures anteriorly and nerve roots medially, depth and angle of screw trajectory is important for the entrance off pedicular screw placement to the S1.

Symptomatic Iliosacral Screw Removal After Pelvic Trauma-Incidence and Clinical Impact

OBJECTIVE

To calculate the incidence of symptomatic iliosacral (SI) screw removal following pelvic trauma and to determine the clinical impact of the secondary intervention.

DESIGN

Retrospective chart review.

SETTING

Level 1 and Level 2 trauma centers.

PATIENTS

Four hundred seventy-one consecutive patients undergoing percutaneous posterior pelvic fixation over 10 years, with 7 excluded for spinopelvic fixation,and 7 excluded due to age <16 year old.

INTERVENTION

Implant removal.

MAIN OUTCOME MEASUREMENT

Secondary intervention.

RESULTS

A total of 25/457 patients underwent screw removal (5.4%). Two patients were lost to follow-up, leaving 23 for analysis. There were 13 male patients and 10 female patients. There were 13 SI and 10 trans-sacral screws removed. Four screws were loose before removal (17%). Average time to screw removal was 10.7 months (4-26 minutes). Fifteen (83.3%) patients had subjective improvement, and 3 (16.7%) had no notable improvement.

CONCLUSION

The incidence of symptomatic SI screws necessitating removal is low (5.4%). When removed, there is a high likelihood (83%) that the secondary intervention will result in subjective symptomatic improvement. Routine screw removal is unnecessary because most patients tolerate the implants without symptoms necessitating subsequent surgery.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

A novel technique for sacropelvic fixation using image-guided sacroiliac screws: a case series and biomechanical study

In this study, we sought to assess the safety and accuracy of sacropelvic fixation performed with image-guided sacroiliac screw placement using postoperative computed tomography and X-rays. The sacroiliac screws were placed with navigation in five patients. Intact specimens were mounted onto a six-degrees-of-freedom spine motion simulator. Long lumbosacral constructs using bilateral sacroiliac screws and bilateral S1 pedicle and iliac screws were tested in seven cadaveric spines. Nine sacroiliac screws were well-placed under an image guidance system (IGS); one was placed poorly without IGS with no symptoms. Both fixation techniques significantly reduced range of motion (P<0.05) at L5–S1. The research concluded that rigid lumbosacral fixation can be achieved with sacroiliac screws, and image guidance improves its safety and accuracy. This new technique of image-guided sacroiliac screw insertion should prove useful in many types of fusion to the sacrum, particularly for patients with poor bone quality, complicated anatomy, infection, previous failed fusion and iliac harvesting.

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

STUDY DESIGN

This is a retrospective data analysis.

OBJECTIVE

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.

SUMMARY OF BACKGROUND DATA

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.

MATERIALS AND METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Intra- and interrater reliabilities and a method comparison of 2D and 3D techniques in cadavers to determine sacroiliac screw loosening

Sacroiliac (SI) screw loosening may indicate persistent instability, non-union and contribute to pain. Yet, there is no reliable objective measurement technique to detect and monitor SI screw loosening. In 9 cadaveric pelvises one of two SI screw was turned back approximately 20 mm and subsequently assessed by optical measurement, fluoroscopy and a 3D scan using an image intensifier. CTs were segmented and a contour-based registration of the 3D models and the fluoroscopies was performed to measure SI backing out (X-ray module). Three independent observers performed measurements with three repetitions. Deviation of the measurement techniques to the 3D scan, intra- and interrater reliabilities and method equivalence to the 3D scan were assessed. The X-ray module and two fluoroscopic measurement techniques yielded a difference less than 5 mm compared to the 3D scan and equivalence to the 3D scan. Intrarater reliability was for two observers and almost all techniques very good. Three fluoroscopic measurement techniques and optical measurements displayed a very good interrater reliability. The 3D scan and X-ray module yielded the most precise values for SI screw loosening but only the fluoroscopic measurement of the inlet lateral loosening displayed a good reliability and equivalence to the 3D scan.

Patient Weight-bearing after Pelvic Fracture Surgery-A Systematic Review of the Literature: What is the Modern Evidence Base?

Background

Little attention in the literature appears to have been paid to the issue of postoperative weight-bearing protocols for different injury patterns after pelvic fracture surgery. The primary aim of this study is to review the currently available literature to define the level of available evidence used to inform surgical decisions on weight-bearing after pelvic fracture surgery. Secondary aims are to assess the published methods of fracture classification, surgical management, and assessment or reporting of patient outcomes.

Methods

A systematic review of the English language literature from 1990 to 2016 was undertaken. Eligible papers were all papers reporting minimum 6-month outcomes following surgery for pelvic fractures in adults. Exclusion criteria included pathological fractures or those resulting from penetrating injury, solely osteoporotic fractures, or series with less than 6 months of follow-up data.

Results

There is very little published scientific data to inform the treating surgeon on postoperative weight-bearing protocols after pelvic fracture surgery, with no randomized trials and only 1 paper out of 122 stating this as a primary aim. More than half of the papers published did not state what postoperative protocol was employed. There is no standardization of outcome measures, with less than 20% of papers using the most common validated outcome scoring system; in contrast, there is good agreement on the use of either the Tile (75%) or Burgess and Young (20%) classification.

Limitations

Due to the lack of published studies looking at the topic of postoperative weight-bearing after pelvic fractures, no specific recommendations are possible. As large numbers of papers were included, they were not individually assessed for bias.

Conclusion

A review of postoperative weight-bearing regimes reveals a nonexistent scientific evidence base from which to make recommendations, although a consensus strategy has been identified. Future research needs to be directed at this topic, as has already been the case in numerous other fracture areas, since the advantages of early mobility are potentially significant. The reported methodology for assessing and reporting patient outcomes after pelvic fracture surgery reveals no consistent standards, and the majority of papers use no specific outcome scoring system.

How to cite this article

Rickman M, Link B-C, Solomon LB. Patient Weight-bearing after Pelvic Fracture Surgery-A Systematic Review of the Literature: What is the Modern Evidence Base? Strategies Trauma Limb Reconstr 2019;14(1):45-52.

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

Background

Pelvic ring–comminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure.

Objective

Our 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.

Methods

3D 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).

Results

The 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.

Conclusion

Inclusion of external fixation improved resistance only to torsional loading.

Translational Potential of this Article

Patients with comminuted transforaminal sacral–ipsilateral rami fractures benefit from this fixation.

Safe Zone Quantification of the Third Sacral Segment in Normal and Dysmorphic Sacra

OBJECTIVE

To quantify the osseous anatomy of the dysmorphic third sacral segment and assess its ability to accommodate internal fixation.

DESIGN

Retrospective chart review of a trauma database.

SETTING

University Level 1 Trauma Center.

PATIENTS

Fifty-nine patients over the age of 18 with computed tomography scans of the pelvis separated into 2 groups: a group with normal pelvic anatomy and a group with sacral dysmorphism.

MAIN OUTCOME MEASUREMENTS

The sacral osseous area was measured on computed tomography scans in the axial, coronal, and sagittal planes in normal and dysmorphic pelves. These measurements were used to determine the possibility of accommodating a transiliac transsacral screw in the third sacral segment.

RESULTS

In the normal group, the S3 coronal transverse width averaged 7.71 mm and the S3 axial transverse width averaged 7.12 mm. The mean S3 cross-sectional area of the normal group was 55.8 mm. The dysmorphic group was found to have a mean S3 coronal transverse width of 9.49 mm, an average S3 axial transverse width of 9.14 mm, and an S3 cross-sectional area of 77.9 mm.

CONCLUSIONS

The third sacral segment of dysmorphic sacra has a larger osseous pathway available to safely accommodate a transiliac transsacral screw when compared with normal sacra. The S3 segment of dysmorphic sacra can serve as an additional site for screw placement when treating unstable posterior pelvic ring fractures.

Is S3 a Viable Osseous Fixation Pathway?

OBJECTIVES

To report the incidence of patients with a third sacral segment (S3) osseous fixation pathway (OFP) that could accommodate a transiliac-transsacral screw.

DESIGN

Retrospective case series.

SETTING

Regional Level 1 Trauma Center.

PATIENTS/PARTICIPANTS

A total of 250 patients without pelvic trauma from January 2017 to February 2017 were included.

INTERVENTION

The axial and sagittal reconstruction images of each patient's computed abdomen and pelvis tomography (CT) scans were reviewed.

MAIN OUTCOME MEASUREMENTS

Each CT was evaluated for the presence of sacral dysmorphism and whether an S3 OFP that could accommodate an intraosseous transiliac-transsacral screw exists.

RESULTS

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.

CONCLUSIONS

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.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Use of the S3 Corridor for Iliosacral Fixation in a Dysmorphic Sacrum: A Case Report

CASE

The S1 and S2 corridors are the typical osseous pathways for iliosacral screw fixation of posterior pelvic ring fractures. In dysmorphic sacra, the S1 screw trajectory is often different from that in normal sacra. We present a case of iliosacral screw placement in the third sacral segment for fixation of a complex lateral compression type-3 pelvic fracture in a patient with a dysmorphic sacrum.

CONCLUSION

In patients with dysmorphic sacra and unstable posterior pelvic ring fractures or dislocations, the S3 corridor may be a feasible osseous fixation pathway that can be used in a manner equivalent to the S2 corridor in a normal sacrum.

Critical dimensions of trans-sacral corridors assessed by 3D CT models: Relevance for implant positioning in fractures of the sacrum

Trans-sacral implants can be used alternatively to sacro-iliac screws in the treatment of osteoporosis-associated fragility fractures of the pelvis and the sacrum. We investigated trans-sacral corridor dimensions, the number of individuals amenable to trans-sacral fixation, as well as the osseous boundaries and shape of the S1 corridor. 3D models were reconstructed from pelvic CT scans from 92 Europeans and 64 Japanese. A corridor of <12 mm was considered critical for trans-sacral implant positioning, and <8 mm as impossible. A statistical model of trans-sacral corridor S1 was computed. The limiting cranio-caudal diameter was 11.6 mm (±5.4) for S1 and 14 mm (±2.4) for S2. Trans-sacral implant positioning was critical in 52% of cases for S1, and in 21% for S2. The S1 corridor was impossible in 26%, with no impossible corridor in S2. Antero-superiorly, the S1 corridor was limited not only by the sacrum but in 40% by the iliac fossa. The statistical model demonstrated a consistent oval shape of the trans-section of corridor S1. Considering the variable in size and shape of trans-sacral corridors in S1, a thorough anatomical knowledge and preoperative planning are mandatory using trans-sacral implants. In critical cases, S2 is a veritable alternative. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2577-2584, 2017.

Can the possibility of transverse iliosacral screw fixation for first sacral segment be predicted preoperatively? Results of a computational cadaveric study

OBJECTIVES

The purpose of this study was to predict the possibility of transverse iliosacral (TIS) screw fixation into the first sacral segment (S₁) and introduce practical anatomical variables using conventional computed tomography (CT) scans.

MATERIALS AND METHODS

A total of 82 cadaveric sacra (42 males and 40 females) were used for continuous 1.0-mm slice CT scans, which were imported into Mimics^® software to produce a three-dimensional pelvis model. The anterior height (BH) and superior width (BW) of the elevated sacral segment was measured, followed by verification of the safe zone (SZ_S1 and SZ_S2) in a true lateral view. Their vertical (VD_S1 and VD_S2) and horizontal (HD_S1 and HD_S2) distances were measured. VD_S1 less than 7mm was classified as impossible sacrum, since the transverse fixation of 7.0 mm-sized IS screw could not be done safely.

RESULTS

Fourteen models (16.7%; six females, eight males) were assigned as the impossible sacrum. There was no statistical significance regarding gender (p=0.626) and height (p=0.419). The average values were as follows: BW, 31.4mm (SD 2.9); BH, 16.7mm (SD 6.8); VD_S1, 13.4mm (SD 6.1); HD_S1, 22.5mm (SD 4.5); SZ_S1, 239.5mm² (SD 137.1); VD_S2, 15.5mm (SD 3.0); HD_S2, 18.3mm (SD 2.9); and SZ_S2, 221.1mm² (SD 68.5). Logistic regression analysis identified BH (p=0.001) and HD_S1 (p=0.02) as the only statistically significant variables to predict the possibility. Receiver operating characteristic curve analysis established a cut-off value for BH and HD_S1 of impossible sacrum of 20.6mm and 18.6mm, respectively.

CONCLUSION

BH and HD_S1 could be used to predict the possibility of TIS screw fixation. If the BH exceeds 20.6mm or HD_S1 is less than 18.6mm, TIS screw fixation for S₁ should not be undertaken because of narrowed SZ.

A Useful Preoperative Planning Technique for Transiliac-Transsacral Screws

Stabilization of posterior pelvic ring injuries is increasingly performed using percutaneously placed iliosacral and transiliac-transsacral screws. Understanding the unique and specific anatomical variations present in each patient is paramount. Multiple methods of evaluating potential osseous fixation pathways for screw placement exist, but many require specific imaging protocols, specialized software, or modification of data. Not all surgeons and institutions have access to these options for a variety of reasons. A simple technique to preoperatively plan for safe transiliac-transsacral screws is proposed.

Transsacral Osseous Corridor Anatomy Is More Amenable To Screw Insertion In Males: A Biomorphometric Analysis of 280 Pelves

BACKGROUND

Percutaneous iliosacral screw placement is the standard procedure for fixation of posterior pelvic ring lesions, although a transsacral screw path is being used more frequently in recent years owing to increased fracture-fixation strength and better ability to fix central and bilateral sacral fractures. However, biomorphometric data for the osseous corridors are limited. Because placement of these screws in a safe and effective manner is crucial to using transsacral screws, we sought to address precise sacral anatomy in more detail to look for anatomic variation in the general population.

QUESTIONS/PURPOSES

We asked: (1) What proportion of healthy pelvis specimens have no transsacral corridor at the level of the S1 vertebra owing to sacral dysmorphism? (2) If there is no safe diameter for screw placement in the transsacral S1 corridor, is an increased and thus safe diameter of the transsacral S2 corridor expected? (3) Are there sex-specific differences in sacral anatomy and are these correlated with known anthropometric parameters?

METHODS

CT scans of pelves of 280 healthy patients acquired exclusively for medical indications such as polytrauma (20%), CT angiography (70%), and other reasons (10%), were segmented manually. Using an advanced CT-based image analysis system, the mean shape of all segmented pelves was generated and functioned as a template. On this template, the cylindric transsacral osseous corridor at the level of the S1 and S2 vertebrae was determined manually. Each pelvis then was registered to the template using a free-form registration algorithm to measure the maximum screw corridor diameters on each specimen semiautomatically.

RESULTS

Thirty of 280 pelves (11%) had no transsacral S1 corridor owing to sacral dysmorphism. The average of maximum cylindrical diameters of the S1 corridor for the remaining 250 pelves was 12.8 mm (95% CI, 12.1-13.5 mm). A transverse corridor for S2 was found in 279 of 280 pelves, with an average of maximum cylindrical diameter of 11.6 mm (95% CI, 11.3-11.9 mm). Decreasing transsacral S1 corridor diameters are correlated with increasing transsacral S2 corridor diameters (R value for females, -0.260, p < 0.01; for males, -0.311, p < 0.001). Female specimens were more likely to have sacral dysmorphism (defined as a pelvis without a transsacral osseous corridor at the level of the S1 vertebra) than were male specimens (females, 16%; males, 7%; p < 0.003). Furthermore female pelves had smaller-corridor diameters than did male pelves (females versus males for S1: 11.7 mm [95% CI, 10.6-12.8 mm] versus 13.5 mm [95% CI, 12.6-14.4 mm], p < 0.01; and for S2: 10.6 mm [95% CI, 10.1-11.1 mm] versus 12.2 mm [95% CI, 11.8-12.6 mm ], p < 0.0001).

CONCLUSIONS

Narrow corridors and highly individual, sex-dependent variance of morphologic features of the sacrum make transsacral implant placement technically demanding. Individual preoperative axial-slice CT scan analyses and orthogonal coronal and sagittal reformations are recommended to determine the prevalence of sufficient-sized osseous corridors on both levels for safe screw placements, especially in female patients, owing to their smaller corridor diameters and higher rate of sacral dysmorphism.

The Effect of Transiliac-Transsacral Screw Fixation for Pelvic Ring Injuries on the Uninjured Sacroiliac Joint

OBJECTIVE

To evaluate the functional outcomes and pain in patients with unilateral posterior pelvic ring injuries treated with transiliac-transsacral screw fixation compared with unilateral iliosacral screw fixation.

DESIGN

Retrospective comparative study.

SETTING

Three academic level 1 trauma centers.

PATIENTS/PARTICIPANTS

From a group of 866 patients with pelvic ring injuries treated surgically, 86 patients with unilateral pelvic ring injuries treated with transiliac-transsacral screws and 97 patients treated with unilateral iliosacral screws were identified. Thirty-six patients treated with transiliac-transsacral fixation and 26 patients treated with unilateral iliosacral screws met the inclusion criteria and participated.

INTERVENTION

Patients were treated surgically for unstable pelvic ring injuries with either unilateral iliosacral screws or transiliac-transsacral screws at the discretion of the treating surgeon.

MAIN OUTCOME MEASUREMENT

Majeed Pelvic Score.

RESULTS

There was no significant difference in Majeed Pelvic Scores between patients treated with transiliac-transsacral screws and those treated with unilateral iliosacral screws (72.8 ± 23.7 vs. 70.4 ± 19.0, P = 0.66). There was no difference in side-specific Numeric Rating Scale pain scores between patients treated with transiliac-transsacral screws and those treated with unilateral iliosacral screws on the injured side (2.5 ± 3.1 vs. 2.0 ± 2.4, P = 0.46) or the uninjured side (1.7 ± 2.8 vs. 0.8 ± 1.7, P = 0.12). Mean follow-up was greater than 3 years with no difference between the groups (mean 1270 vs. 1242 days, P = 0.84).

CONCLUSIONS

Treatment of unilateral pelvic ring injuries with transiliac-transsacral screws does not adversely affect or improve patient outcomes or subjective pain scores when compared with those treated with unilateral iliosacral screws.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.