Biomechanical comparison of augmented versus non-augmented sacroiliac screws in a novel hemi-pelvis test model

Cerclage augmentation of S1-S2 transsacral screw fixation in osteoporotic posterior pelvis ring injuries: A biomechanical feasibility study

Injuries of the posterior pelvic ring are predominantly associated with osteoporosis. Percutaneously placed screws transfixing the sacroiliac joint have become the gold standard for their treatment. However, screw cut-out, backing-out, and loosening are common complications. One promising option could be cerclage reinforcement of cannulated screw fixations. Therefore, the aim of this study was to evaluate the biomechanical feasibility of posterior pelvic ring injuries fixed with S1 and S2 transsacral screws augmented with cerclage. Twenty-four composite osteoporotic pelvises with posterior sacroiliac joint dislocation were stratified into four groups for S1-S2 transsacral fixation using either (1) fully threaded screws, (2) fully threaded screws with cable cerclage, (3) fully threaded screws with wire cerclage, or (4) partially threaded screws with wire cerclage. All specimens were biomechanically tested under progressively increasing cyclic loading until failure. Intersegmental movements were monitored by motion tracking. The transsacral partially threaded screw fixation with wire cerclage augmentation resulted in significantly less combined angular intersegmental movement in the transverse and coronal plane versus its fully threaded counterpart (p = 0.032), as well as in significantly less flexion versus all other fixations (p ≤ 0.029). Additional cerclage augmentation could be performed intraoperatively to improve the stability of posterior pelvic ring injuries treated with S1-S2 transsacral screw fixation. Further investigations should follow to consolidate the current results on real bones and possibly consider execution of a clinical study.

Substitutional semi-rigid osteosynthesis technique for treatment of unstable pubic symphysis injuries: a biomechanical study

BACKGROUND/PURPOSE

The surgical fixation of a symphyseal diastasis in partially or fully unstable pelvic ring injuries is an important element when stabilizing the anterior pelvic ring. Currently, open reduction and internal fixation (ORIF) by means of plating represents the gold standard treatment. Advances in percutaneous fixation techniques have shown improvements in blood loss, surgery time, and scar length. Therefore, this approach should also be adopted for treatment of symphyseal injuries. The technique could be important since failure rates, following ORIF at the symphysis, remain unacceptably high. The aim of this biomechanical study was to assess a semi-rigid fixation technique for treatment of such anterior pelvic ring injuries versus current gold standards of plate osteosynthesis.

METHODS

An anterior pelvic ring injury type III APC according to the Young and Burgess classification was simulated in eighteen composite pelvises, assigned to three groups (n = 6) for fixation with either a single plate, two orthogonally positioned plates, or the semi-rigid technique using an endobutton suture implant. Biomechanical testing was performed in a simulated upright standing position under progressively increasing cyclic loading at 2 Hz until failure or over 150,000 cycles. Relative movements between the bone segments were captured by motion tracking.

RESULTS

Initial quasi-static and dynamic stiffness, as well as dynamic stiffness after 100,000 cycles, was not significantly different among the fixation techniques (p ≥ 0.054).). The outcome measures for total displacement after 20,000, 40,000, 60,000, 80,000, and 100,000 cycles were associated with significantly higher values for the suture technique versus double plating (p = 0.025), without further significant differences among the techniques (p ≥ 0.349). Number of cycles to failure and load at failure were highest for double plating (150,000 ± 0/100.0 ± 0.0 N), followed by single plating (132,282 ± 20,465/91.1 ± 10.2 N), and the suture technique (116,088 ± 12,169/83.0 ± 6.1 N), with significantly lower values in the latter compared to the former (p = 0.002) and no further significant differences among the techniques (p ≥ 0.329).

CONCLUSION

From a biomechanical perspective, the semi-rigid technique for fixation of unstable pubic symphysis injuries demonstrated promising results with moderate to inferior behaviour compared to standard plating techniques regarding stiffness, cycles to failure and load at failure. This knowledge could lay the foundation for realization of further studies with larger sample sizes, focusing on the stabilization of the anterior pelvic ring.

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.

Clinical Guidelines for the Diagnosis and Treatment of Fragility Fractures of the Pelvis

BACKGROUND

Fragility fractures of the pelvis (FFPs) are osteoporotic pelvic fractures or insufficiency pelvic fractures caused by the low energy injury or stress fracture in daily livings in the elderly more than 60 years, which the incidence is increasing with the aging population in our country. FFPs result in considerable morbidity and mortality and as well as massive financial burden on the already strained health systems throughout the world.

METHODS

This clinical guideline was initiated by the Trauma Orthopedic Branch of Chinese Orthopedic Association; the External Fixation and Limb Reconstruction Branch of Chinese Orthopedic Association; the National Clinical Research Center for Orthopedics, Sports Medicine & Rehabilitation; Senior Department of Orthopedics of Chinese PLA general hospital; the Third Hospital of Hebei Medical University. The grading of recommendations assessment, development and evaluation (GRADE) approach and the reporting items for practice guidelines in healthcare (RIGHT) checklist were adopted.

RESULTS

22 evidence based recommendations were formulated based on 22 most concerned clinical problems among orthopedic surgeons in China.

CONCLUSION

Understanding these trends through this guideline will facilitate better clinical care of FFP patients by medical providers and better allocation of resources by policy makers.

Is a Washer a Mandatory Component in Young Trauma Patients with S1-S2 Iliosacral Screw Fixation of Posterior Pelvis Ring Injuries? A Biomechanical Study

Background and purpose: Cannulated screws are standard implants for percutaneous fixa-tion of posterior pelvis ring injuries. The choice of whether to use these screws in combination with a washer is still undecided. The aim of this study was to evaluate the biomechanical competence of S1-S2 sacroiliac (SI) screw fixation with and without using a washer across three different screw designs. Material and Methods: Twenty-four composite pelvises were used and an SI joint injury type APC III according to the Young and Burgess classification was simulated. Fixation of the posterior pelvis ring was performed using either partially threaded short screws, fully threaded short screws, or fully threaded long transsacral screws. Biomechanical testing was performed under progressively increasing cyclic loading until failure, with monitoring of the intersegmental and bone-implant movements via motion tracking. Results: The number of cycles to failure and the corresponding load at failure (N) were significantly higher for the fully threaded short screws with a washer (3972 ± 600/398.6 ± 30.0) versus its counterpart without a washer (2993 ± 527/349.7 ± 26.4), p = 0.026. In contrast, these two parameters did not reveal any significant differences when comparing fixations with and without a washer using either partially threaded short of fully threaded long transsacral screws, p ≥ 0.359. Conclusions: From a biomechanical perspective, a washer could be optional when using partially threaded short or fully threaded long transsacral S1-S2 screws for treatment of posterior pelvis ring injuries in young trauma patients. Yet, the omission of the washer in fully threaded short screws could lead to a significant diminished biomechanical stability.

Evaluation of Cannulated Compression Headless Screw (CCHS) as an alternative implant in comparison to standard S1-S2 screw fixation of the posterior pelvis ring: a biomechanical study

BACKGROUND/PURPOSE

Posterior pelvis ring injuries represent typical high-energy trauma injuries in young adults. Joint stabilization with two cannulated sacroiliac (SI) screws at the level of sacral vertebrae S1 and S2 is a well-established procedure. However, high failure- and implant removal (IR) rates have been reported. Especially, the washer recovery can pose the most difficult part of the IR surgery, which is often associated with complications. The aim of this biomechanical study was to evaluate the stability of S1-S2 fixation of the SI joint using three different screw designs.

METHODS

Eighteen artificial hemi-pelvises were assigned to three groups (n = 6) for SI joint stabilization through S1 and S2 corridors using either two 7.5 mm cannulated compression headless screws (group CCH), two 7.3 mm partially threaded SI screws (group PT), or two 7.3 mm fully threaded SI screws (group FT). An SI joint dislocation injury type III APC according to the Young and Burgess classification was simulated before implantation. All specimens were biomechanically tested to failure in upright standing position under progressively increasing cyclic loading. Interfragmentary and bone-implant movements were captured via motion tracking and evaluated at four time points between 4000 and 7000 cycles.

RESULTS

Combined interfragmentary angular displacement movements in coronal and transverse plane between ilium and sacrum, evaluated over the measured four time points, were significantly bigger in group FT versus both groups CCH and PT, p ≤ 0.047. In addition, angular displacement of the screw axis within the ilium under consideration of both these planes was significantly bigger in group FT versus group PT, p = 0.038. However, no significant differences were observed among the groups for screw tip cutout movements in the sacrum, p = 0.321. Cycles to failure were highest in group PT (9885 ± 1712), followed by group CCH (9820 ± 597), and group FT (7202 ± 1087), being significantly lower in group FT compared to both groups CCH and PT, p ≤ 0.027.

CONCLUSION

From a biomechanical perspective, S1-S2 SI joint fixation using two cannulated compression headless screws or two partially threaded SI screws exhibited better interfragmentary stability compared to two fully threaded SI screws. The former can therefore be considered as a valid alternative to standard SI screw fixation in posterior pelvis ring injuries. In addition, partially threaded screw fixation was associated with less bone-implant movements versus fully threaded screw fixation. Further human cadaveric biomechanical studies with larger sample size should be initiated to understand better the potential of cannulated compression headless screw fixation for the therapy of the injured posterior pelvis ring in young trauma patients.

Biomechanical investigation of S2 alar-iliac screw and S1 pedicle screw fixation in the treatment of Denis type II sacral fractures

Although S2 alar-iliac screw technique has been widely used in spinal surgery, its applicability to pelvic fractures is largely unknown. This study aimed to evaluate the biomechanical stability of S2 alar-iliac screw and S1 pedicle screw fixation in the treatment of Denis II sacral fractures. Twenty-eight artificial pelvic fracture models were treated with unilateral lumbopelvic fixation, sacroiliac screw fixation, S2 alar-iliac screw and S1 pedicle screw fixation, and S2 alar-iliac screw and contralateral S1 pedicle screw fixation (Groups 1-4, respectively; N = 7 per group). Each model was cyclically tested under increasing axial compression. Optical motion-tracking was used to assess relative displacement and gap angle, and the number of failure cycles. Relative displacement was significantly smaller in Group 3 than in Groups 1 (p = 0.004) and 4 (p < 0.001) but not significantly different between Groups 3 and 2 (p = 0.290). The gap angle in Group 3 was significantly smaller than that in Group 1 (p = 0.009) on the sagittal plane but significantly larger than that in Group 4 (p = 0.006) on the horizontal plane. A number of failure cycles was significantly higher in Group 3 than in Groups 1 (p = 0.002) and 4 (p = 0.004) but not significantly different between Groups 3 and 2 (p = 0.910). From a biomechanical perspective, S2 alar-iliac screw and S1 pedicle screw fixation can provide good stability in the treatment of Denis II sacral fractures.

[Cement augmentation and bone graft substitutes-Materials and biomechanics]

BACKGROUND

Materials with different characteristics are used for cement augmentation and as bone graft substitutes.

OBJECTIVE

Cement augmentation and bone graft substitutes are the subject of current research. The evaluation of new knowledge allows its specific application.

MATERIAL AND METHODS

Selective literature search and outline of experimental research results on cement augmentation and bone graft substitutes.

RESULTS

Augmentation and bone graft substitutes are essential components of current trauma surgical procedures. Despite intensive research all materials have specific disadvantages. Cement augmentation of implants enhances not only the anchorage but also influences the failure mode.

CONCLUSION

Cement augmentation has large potential especially in osteoporotic bone. In load-bearing regions acrylic-based cements remain the standard of choice. Ceramic cements are preferred in non-load-bearing areas. Their combination with resorbable metals offers still largely unexplored potential. Virtual biomechanics can help improve the targeted application of cement augmentation.

A biomechanical in-vitro study on an alternative fixation technique of the pubic symphysis for open book injuries of the pelvis

PURPOSE

Implant failure rates remain high after plate fixation in pelvic ring injuries. The aim of this study was to compare an alternative fixation technique with suture-button devices and anterior plate fixation in partially stable open-book injuries.

MATERIAL AND METHODS

We acquired 16 human fresh frozen anatomic pelvic specimens. The sacrospinous, sacrotuberous, and anterior sacroiliac ligaments were bilaterally released, and the pubic symphysis transected to simulate a partially stable open-book (AO/OTA 61-B3.1) injury. The specimens were randomly assigned to the two fixation groups. In the first group two suture-button devices were placed in a criss-crossed position through the symphysis. In second group a six-hole plate with standard 3.5 unlocked bicortical screws was used for fixation. Biomechanical testing was performed on a servo-hydraulic apparatus simulating bilateral stance, as described by Hearn and Varga. Cyclic compression loading with a progressively increasing peak load (0.5 N/cycle) was applied until failure. The failure mode, the load and the number of cycles at failure and the proximal and distal distance of the symphysis during testing were compared.

RESULTS

There was no implant failure in either of the two groups. Failures occurred in nine pelvises (56.2%) at the fixation between the sacrum and the mounting jig and in seven pelvises (43.8%) in the sacroiliac joint. Neither the ultimate load nor the number of cycles at failure differed between the surgical techniques (p = 0.772; p = 0.788, respectively). In the suture button group the mean ultimate load was 874.5 N and the number of cycles at failure was 1907.9. In the plate group values were 826.1 N and 1805.6 cycles, respectively. No significant differences at proximal and distal diastasis of the symphysis were monitored during the whole loading process.

CONCLUSION

The fixation with suture button implants showed comparable results to anterior plate fixation in open-book injuries of the pelvis.

Midterm follow-up of elderly patients with fragility fractures of the pelvis: A prospective cohort-study comparing operative and non-operative treatment according to a therapeutic algorithm

INTRODUCTION

The treatment of fragility fractures of the pelvis (FFP) is a challenge. The variations of non-operative- and of operative treatment are manifold and a structured treatment algorithm is lacking. The purpose of this study was to evaluate the outcome of elderly patients with a FFP who were treated with a therapeutic algorithm based on the FFP-classification.

PATIENTS AND METHODS

In a prospective cohort study 154 patients (mean age: 81.8 ±.61 (65-96); female: (86.8%; 131/154). BMI: 23.7 ±.34 (15-43)) with a FFP after inadequate mono trauma were treated according to a strict therapeutic algorithm between 04/2016 and 12/2018. According to a classification based on CT-scans either a standardized operative treatment or conservative therapy was induced and the outcome regarding objective measurements of mobility, pain, need for analgesics and mortality during hospital stay and after one year was analyzed.

RESULTS

82/154 participants (53.2%) were assigned to the conservative treatment group and 72 participants (46.8%) to the operative treatment group. The overall one-year survival rate was 78.1% (118/151). The survival of the operative treatment group was 90.7% (49/54) and significantly higher than the survival of the conservative treatment group (74.7%; 56/75; p=.023). The one-year follow up showed a high dispersion of the pain level in the operatively treated patients and a significantly higher mean in comparison to conservatively treated patients. Both treatment groups showed increasing numbers of patients with unlimited mobilization but also immobile patients. Overall in 31.0% (18/58) of the operative participants and in 14.9% (14/93) of the non-operatively treated participants complications occurred (p=.04).

CONCLUSION

The strict compliance to the presented treatment algorithm of FFP with an operative strategy starting from FFP IIc leads to a significantly lower mortality within one year in comparison to the conservatively treated patients. The worst outcome and the highest mortality was seen in patients who refused the recommendation of operative stabilization. The results of this study justify to proceed with the strict classification dependent treatment algorithm and also support the early switch-over to operative treatment of patients with failed conservative therapy in FFP I to FFP IIb.

Local bone quality measure and construct failure prediction: a biomechanical study on distal femur fractures

INTRODUCTION

The aim of this investigation was to better understand the differences in local bone quality at the distal femur and their correlation with biomechanical construct failure, with the intention to identify regions of importance to optimize implant anchorage.

MATERIALS AND METHODS

Seven fresh-frozen female femurs underwent high-resolution peripheral quantitative computed tomography (HR-pQCT) to determine bone mineral density (BMD) within three different regions of interest (distal, intermedium, and proximal) at the distal femur. In addition, local bone quality was assessed by measuring the peak torque necessary to break out the trabecular bone along each separate hole of a locking compression plate (LCP) during its instrumentation. Finally, biomechanical testing was performed using cyclic axial loading until failure in an AO/OTA 33 A3 fracture model.

RESULTS

Local BMD was highest in the distal region. This was confirmed by the measurement of local bone quality using DensiProbe^™. The most distal holes represented locations with the highest breakaway torque resistance, with the holes on the posterior side of the plate indicating higher values than those on its anterior side. We demonstrated strong correlation between the cycles to failure and local bone strength (measured with DensiProbe^™) in the most distal posterior screw hole, having the highest peak torque.

CONCLUSION

The local bone quality at the distal femur indicates that in plated distal femur fractures the distal posterior screw holes seem to be the key ones and should be occupied. Measurement of the local bone strength with DensiProbe^™ is one possibility to determine the risk of construct failure, therefore, thresholds need to be defined.

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.

Is cement-augmented sacroiliac screw fixation with partially threaded screws superior to that with fully threaded screws concerning compression and pull-out force in fragility fractures of the sacrum? - a biomechanical analysis

Background

Providing a stable osteosynthesis in fragility fractures of the pelvis can be challenging. Cement augmentation increases screw fixation in osteoporotic bone. Generating interfragmentary compression by using a lag screw also improves the stability. However, it is not known if interfragmentary compression can be achieved in osteoporotic sacral bone by cement augmentation of lag screws.

The purpose of this study was to compare cement-augmented sacroiliac screw osteosynthesis using partially versus fully threaded screws in osteoporotic hemipelvises concerning compression of fracture gap and pull-out force.

Methods

Nine fresh-frozen human cadaveric pelvises with osteoporosis were used. In all specimens, one side was treated with an augmented fully threaded screw (group A), and the other side with an augmented partially threaded screw (group B) after generating a vertical osteotomy on both sides of each sacrum. Afterwards, first a compression test with fracture gap measurement after tightening of the screws was performed, followed by an axial pull-out test measuring the maximum pull-out force of the screws.

Results

The fracture gap was significantly wider in group A (mean: 1.90 mm; SD: 1.64) than in group B (mean: 0.91 mm; SD: 1.03; p = 0.028).

Pull-out force was higher in group A (mean: 1696 N; SD: 1452) than in group B (mean: 1616 N; SD: 824), but this difference was not statistically significant (p = 0.767).

Conclusions

Cement augmentation of partially threaded screws in sacroiliac screw fixation allows narrowing of the fracture gap even in osteoporotic bone, while resistance against pull-out force is not significantly lower in partially threaded screws compared to fully threaded screws.

Is Anterior Plating Superior to the Bilateral Use of Retrograde Transpubic Screws for Treatment of Straddle Pelvic Ring Fractures? A Biomechanical Investigation

Background: Fractures of the four anterior pubic rami are described as “straddle fractures”. The aim of this study was to compare biomechanical anterior plating (group 1) versus the bilateral use of retrograde transpubic screws (group 2). Methods: A straddle fracture was simulated in 16 artificial pelvises. All specimens were tested under progressively increasing cyclic loading, with monitoring by means of motion tracking. Results: Axial stiffness did not differ significantly between the groups, p = 0.88. Fracture displacement after 1000–4000 cycles was not significantly different between the groups, p ≥ 0.38; however, after 5000 cycles it was significantly less in the retrograde transpubic screw group compared to the anterior plating group, p = 0.04. No significantly different flexural rotations were detected between the groups, p ≥ 0.32. Moreover, no significant differences were detected between the groups with respect to their cycles to failure and failure loads, p = 0.14. Conclusion: The results of this biomechanical study reveal less fracture displacement in the retrograde transpubic screw group after long-term testing with no further significant difference between anterior plating and bilateral use of retrograde transpubic screws. While the open approach using anterior plating allows for better visualization of the fracture site and open reduction, the use of bilateral retrograde transpubic screws, splinting the fracture, presents a minimally invasive and biomechanically stable technique.

Instability of the posterior pelvic ring: introduction of innovative implants

BACKGROUND

Increasing numbers of posterior pelvic ring fractures, especially in elderly patients, demonstrate the need for soft tissue protecting surgical techniques. Standard of care is iliosacral screw osteosynthesis. This type of osteosynthesis has its limitations especially in patients with reduced bone properties. Therefore, the development of new and straightforward surgical techniques and implant designs is favorable.

METHODS

Introducing this modular system for the posterior pelvic ring, known complications of iliosacral screw osteosynthesis, such as implant loosening and malpositioning may be reduced, due to innovative mechanical characteristics.

RESULTS

The shown cases demonstrate the potential benefits of the system with a wide range of treatment options due to its modularity.

CONCLUSION

The modular implant system presented here can significantly facilitate and improve the stabilization of posterior pelvic ring instabilities.

Accuracy of screw stabilization of the dorsal pelvic ring using a hybrid operating room: 5 Year experience in a level 1 trauma center

INTRODUCTION

Accuracy for screw placement in the dorsal pelvic ring can be enhanced using intraoperative 3D navigation. Advances in intraoperative imaging lead to benefits for pelvic surgery. New c-arms are equipped with flat panel detectors, which have a larger detector and assure higher image quality with accompanying dose reduction. A hybrid OR is defined by a fixed imaging system in an operating room providing the benefit of the surgical environment in combination with advanced intraoperative imaging. Aim of our investigation was to analyze the accuracy of navigated sacroiliac (SI) and transsacral transiliac (TSTI) screws in the dorsal pelvic ring, which were implanted with a hybrid OR in the first five years of use.

MATERIAL AND METHODS

All percutaneous SI or TSTI screws implanted in the hybrid OR using intraoperative navigation in the first 5 years of utilization (between June 2012 to June 2017) were included. Intraoperative 3D-scans and postoperative computed tomography were examined for screw perforation.

RESULTS

210 SI and TSTI screws were implanted in 187 patients using intraoperative navigation in the hybrid-OR. 90.6 % of SI screws showed no cortical perforation. 6,3 % had a grade 1, 2.4 % a grade 2 and 0.8 % a grade 3 perforation. In 80.7 % of TSTI screws no perforation and in 13.3 % a grade 1 perforation was detected. 3.6 % showed a grade 2 and 2.4 % a grade 3 perforation. No significant difference between both screw types regarding the grade of cortical perforation could be seen. No significant relation between perforation rate and year of operation could be detected.

CONCLUSION

Intraoperative navigation in a hybrid OR ensures a high accuracy for SI screws. Due to the large field of view and high image quality TSTI screws can be safely implanted in S1 and S2. Utilization of a hybrid-OR is accompanied with a steep learning curve.

Biomechanical stability of sacroiliac screw osteosynthesis with and without cement augmentation

BACKGROUND

Percutaneous sacroiliac (SI) screw fixation is the standard operative treatment of traumatic disruptions to the posterior pelvic ring. The technique offers good outcomes and early postoperative mobilization, which is vital in elderly patients with fragility fractures of the pelvis. While a double-screw technique has been shown to provide optimal biomechanical stability compared to a single-screw construct, anatomic variations and patient-specific characteristics may prevent the safe insertion of two SI screws. We aimed to determine whether cement augmentation of a single SI screw would provide biomechanical stability comparable to that of the double-screw technique.

METHODS

Three sacroiliac screw osteosynthesis configurations were tested on 10 human cadaveric pelvis specimens: a single cannulated screw; two cannulated screws; and a single, cement-augmented cannulated screw. Displacement and stiffness of the anterior and posterior pelvic ring after fixation with each technique were measured under axial load. Results where compared using linear regression and paired t-tests.

RESULTS

A single uncemented screw offered significantly worse stability in the anterior pelvis compared to a double-screw technique (P < 0.05) and to a single cement-augmented screw technique (P < 0.05). There was no significant difference in anterior pelvic ring stability between the single cement-augmented screw technique and the double-screw technique (P > 0.05). There was no significant difference in the stability of the posterior pelvic ring between the three techniques (P > 0.05).

CONCLUSIONS

A single cement-augmented cannulated sacroiliac screw provides biomechanical stability similar to that of a non-augmented double-screw technique in the treatment of posterior pelvic ring fractures.

Biomechanical Comparison of Five Fixation Techniques for Unstable Fragility Fractures of the Pelvic Ring

Background: Incidence of pelvic ring fractures has increased over the past four decades, especially after low-impact trauma—classified as fragility fractures of the pelvis (FFP). To date, there is a lack of biomechanical evidence for the superiority of one existing fixation technique over another. An FFP type IIc was simulated in 50 artificial pelvises, assigned to 5 study groups: Sacroiliac (SI) screw, SI screw plus supra-acetabular external fixator, SI screw plus plate, SI screw plus retrograde transpubic screw, or S1/S2 ala–ilium screws. The specimens were tested under progressively increasing cyclic loading. Axial stiffness and cycles to failure were analysed. Displacement at the fracture sites was evaluated, having been continuously captured via motion tracking. Results: Fixation with SI screw plus plate and SI screw plus retrograde transpubic screw led to higher stability than the other tested techniques. The S1/S2 ala–ilium screws were more stable than the SI screw or the SI screw plus external fixator. Conclusions: In cases with displaced fractures, open reduction and plate fixation provides the highest stability, whereas in cases where minimally invasive techniques are applicable, a retrograde transpubic screw or S1/S2 ala–ilium screws can be considered as successful alternative treatment options.

[Trends in the surgical treatment of fractures of the pelvic ring : A nationwide analysis of operations and procedures code (OPS) data between 2005 and 2017]

AIM

The aim of this study was to analyze the epidemiological trends and incidences in inpatient pelvic surgery in the period from 2005 to 2007.

METHOD

Approximately 194 million anonymized diagnosis-related groups (DRG) inpatient records were collected by the German Federal Statistical Office between 2005 and 2017. These data were screened for pelvic procedures, gender and age of the patients. Statistical testing was performed using the χ²-test and Mann-Whitney U-test (p < 0.05).

RESULTS

Between 2005 and 2017 the number of closed reduction and internal fixation of the pelvic ring with screw fixation increased by +1116%. The use of screw fixation for closed reduction and internal fixation of the sacroiliac joint increased by +800%. The number of cases of open reduction and internal fixation of fractures of the pelvic ring and pelvic rim increased by +185% and reposition with external fixator increased by +188%. In 2005 more surgical procedures were undertaken in male inpatients, whereas more surgical procedures were undertaken in female inpatients in 2017. In general, a large increase in the number of pelvic procedures was observed in the group of patients >50 years old.

CONCLUSION

There was an increase in the number of all analyzed pelvic procedures between 2005 and 2017. Especially the use of screw fixation increased. The introduction of new techniques (e.g. screw fixation of the sacroiliac joint) and progress and innovation in the field of three-dimensional navigation techniques, the demographic trend, greater mobility and higher demands on functionality of older patients might explain this increase in pelvic procedures.

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.

Development and first biomechanical validation of a score to predict bone implant interface stability based on clinical qCT scans

Sufficient implant anchoring in osteoporotic bone is one major challenge in trauma and orthopedic surgery. In these cases, preoperative planning of osteosynthesis is becoming increasingly important. This study presents the development and first biomechanical validation of a bone-implant-anchorage score based on clinical routine quantitative computer tomography (qCT) scans. 10 pairs of fresh frozen femora (mean age 77.4 years) underwent clinical qCT scans after placing 3 referential screws (for matching with the second scan). Afterwards, three 4.5 mm cortical screws (DePuy Synthes, Zuchwil, Switzerland) were placed in each distal femur in the dia-metaphyseal transition followed by the second CT scan. The femur was segmented using thresholding and its outer shape was visualized as a surface model. A 3D model of the cortex screw in STL format was used to model the screw surface precisely. For each femur, the 3 cortex screw models were exactly positioned at the locations previously determined using the second CT scan. The BMD value was calculated at the center of each triangle as an interpolation from the measured values at the three vertices (triangle corners) in the CT. Scores are based on the sum of all the triangles’ areas multiplied by their BMD values. Four different scores were calculated. A screw pull-out test was performed until loss of resistance. A quadratic model adequately describes the relation between all the scores and pull-out values. The square of the best score explains just fewer than 70% of the total variance of the pull-out values and the standardized residual which were approximately normally distributed. In addition, there was a significant correlation between this score and the peak pull-out force (p < 0.001). The coefficient of determination was 0.82. The presented score has the potential to improve preoperative planning by adding the mechanical to the anatomical dimension when planning screw placement.

Safety, Effect and Feasibility of Percutaneous SI-Screw with and without Augmentation-A 15-Year Retrospective Analysis on over 640 Screws

BACKGROUND

Minimally invasive sacroiliac-screw (SI-screw) fixation of the pelvis is used in energy trauma (Arbeitsgemeinschaft für Osteosynthesefragen (AO) classified) and fragility fractures (Fragility Fracture of the Pelvis (FFP) classified). However, available clinical data are based on small case series and biomechanical data seem to be contradictory.

METHODS

The present single center retrospective cohort study investigated percutaneous SI-screw fixation and augmentation over 15 years. Groups were compared concerning the general epidemiological data, mobilization, complication rates, duration of stay, and safety of SI-screw insertion. Multivariable analyses were performed using logistic regression.

RESULTS

Between 2005 and March 2020, 448 patients with 642 inserted SI-screws were identified. Iatrogenic neurological impairment was documented in 2.47% and correlated with screw misplacement. There was an increased complication risk in patients with AO type C over patients with AO type B and in FFP II over FFP III/IV patients. Cement-augmented FFP patients showed a 25% reduced stay in hospital and a reduced complication risk. Cement-associated complications were seen in 22% without correlation to neurologic impairment.

CONCLUSIONS

The present study confirms the safety and usability of percutaneous SI-screw fixation, despite specific risks. Cement augmentation seems to reduce the complication risk in FFP patients and shorten hospital stay for some reasons, without increased specific complications or correlated neurological impairment.

[Application of anterior subcutaneous internal fixator combined with posterior plate in treatment of unstable pelvic fractures]

Objective

To investigate the effectiveness of anterior subcutaneous internal fixator combined with posterior plate in the treatment of unstable pelvic fractures.

Methods

Between January 2015 and January 2019, 26 cases of unstable pelvic fractures were treated with anterior subcutaneous internal fixator combined with posterior plate. There were 16 males and 10 females, with an average age of 42.8 years (range, 25-66 years). According to the Tile classification, 9 of them belonged to type B2, 6 to type B3, 7 to type C1, 3 to type C2, 1 to type C3. The injury severity score (ISS) was 6-43 (mean, 18.3). Four cases combined with brain injury, 7 with limb fractures, 3 with hemopneumothorax, 1 with sciatic nerve injury. The time from injury to operation was 4-12 days (mean, 6.4 days). The intraoperative blood loss, operation time, and the complications were recorded. The fracture reduction and the postoperative function of patients were evaluated.

Results

All patients were followed up 12-26 months (mean, 16.8 months). The operation time was 65-142 minutes (mean, 72.5 minutes) and the intraoperative blood loss was 42-124 mL (mean, 64.2 mL). There were 2 cases of unilateral lateral femoral cutaneous nerve stimulation, 1 case of femoral nerve paralysis, and 1 case of superficial infection of incision, which were cured after corresponding treatment. X-ray films showed that all fractures healed at 3 months after operation. At last follow-up, according to Matta criteria for fracture reduction, the results were excellent in 8 cases, good in 15 cases, fair in 2 cases, and poor in 1 case, with an excellent and good rate of 88.5%. According to Majeed scoring system for pelvic function, the results were excellent in 10 cases, good in 12 cases, and fair in 4 cases, with an excellent and good rate of 84.6%.

Conclusion

For unstable pelvic fractures, the anterior subcutaneous internal fixator combined with posterior plate has fewer operative complications, high security, and achieve good effectiveness.

The S2-Alar-Iliac Screw for Pelvic Trauma

Percutaneous sacro-iliac screw osteosynthesis is considered to be standard of care for most posterior pelvic ring fractures. However, special situations require alternative strategies for sufficient stabilization. In these cases, stabilization can often be achieved using posterior instrumentation e.g. using SIPS-screws (spina-iliaca-posterior-superior screws). However, this often leads to implant-related aggravation of the sometimes already critical soft tissue conditions after pelvic trauma. S2-Ala-Ilium screws (S2AI screws) are a suitable alternative. The starting point lies medial of the posterior superior iliac spine below the iliac level. It is almost in line with a potential spinal instrumentation and therefore usually causes fewer soft tissue problems. Although this technique has been widely used in spinal surgery in recent years, its use in orthopaedic traumatology is largely unknown. The possibilities but also the limitations of this technique for the treatment of injuries to the pelvis are illustrated by this retrospective case series.

Biomechanics of Osteoporotic Fracture Fixation

PURPOSE OF REVIEW

Fractures of osteoporotic bone in elderly individuals need special attention. This manuscript reviews the current strategies to provide sufficient fracture fixation stability with a particular focus on fractures that frequently occur in elderly individuals with osteoporosis and require full load-bearing capacity, i.e., pelvis, hip, ankle, and peri-implant fractures.

RECENT FINDINGS

Elderly individuals benefit immensely from immediate mobilization after fracture and thus require stable fracture fixation that allows immediate post-operative weight-bearing. However, osteoporotic bone has decreased holding capacity for metallic implants and is thus associated with a considerable fracture fixation failure rate both short term and long term. Modern implant technologies with dedicated modifications provide sufficient mechanical stability to allow immediate weight-bearing for elderly individuals. Depending on fracture location and fracture severity, various options are available to reinforce or augment standard fracture fixation systems. Correct application of the basic principles of fracture fixation and the use of modern implant technologies enables mechanically stable fracture fixation that allows early weight-bearing and results in timely fracture healing even in patients with osteoporosis.

Augmented Fixation for Fractures of the Appendicular Skeleton

Despite advances in technology such as locked plating, osteoporotic bone and bone defects remain challenging complications for orthopaedic surgeons. The concept of augmented fixation is useful in these settings. Augmented fixation can be described as improving construct strength and stability by enhancing the surrounding environment. By understanding and using the techniques of alternative fixation strategies, endosteal or medullary support, structural grafting, or the use of bone graft substitutes in combination with standard or integrated fixation, surgeons can improve the chances of success when treating difficult fractures. The purpose of this article is to introduce the reader to the concept of augmented fixation, review strategies for its application, and review applicable published results.

[Fragility fractures of the pelvis]

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

Comparative Study of Percutaneous Sacroiliac Screw with or without TiRobot Assistance for Treating Pelvic Posterior Ring Fractures

Objectives

To analyze the curative effect of TiRobot surgical robotic navigation and location system‐assisted percutaneous sacroiliac screw fixation and percutaneous sacroiliac screw by traditional fluoroscopy, and to summarize the safety and benefits of TiRobot.

Methods

A total of 91 patients with pelvic posterior ring fractures from December 2015 to February 2018 were included in this study. According to the surgical methods selected by the patients, the patients were divided into a TiRobot surgical robotic navigation and location system group (TiRobot group) and a percutaneous sacroiliac screw fixation group (traditional group). Statistical indicators included the number of sacroiliac screws, the time of planning the sacroiliac screw path, fluoroscopy frequency, fluoroscopy time, operation time, length of incision, blood loss, anesthesia time, the healing process of skin incisions, and fracture healing time. Fracture reduction was evaluated according to the maximum displacement degree at the inlet and outlet view X‐ray or CT. Matta standard was used to evaluate fracture reduction. At the last follow‐up, the Majeed function system was used to evaluate the function.

Results

All patients were followed up for 8 to 32 months. A total of 66 sacroiliac screws were implanted in the TiRobot group. A total of 43 sacroiliac screws were implanted in the traditional group. There were statistically significant differences in terms of fluoroscopy frequency, fluoroscopy time, operation time, incision length, anesthesia time, and blood loss between the two groups; the TiRobot group was superior to the traditional group. The healing time of the TiRobot group and the traditional group was 4.61 ± 0.68 months (range, 3.5–6.3 months) and 4.56 ± 0.78 months (range, 3.4–6.2 months), respectively, and there was no statistical difference. Postoperatively, by Matta standard, the overall excellent and good rate of fracture reduction was 89.28% and 88.57%, respectively. At the last follow‐up, by Majeed function score, the overall excellent and good rate was 91.07% and 91.43%. There was no statistical difference between the two groups.

Conclusion

Sacroiliac screw implantation assisted by TiRobot to treat the posterior pelvic ring fractures has the characteristics of less trauma, shorter operation time, and less blood loss. TiRobot has the characteristics of high safety and accuracy and has great clinical application value.

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.

A novel computer navigation method for accurate percutaneous sacroiliac screw implantation: A technical note and literature review

The purpose of this study was to assess the accuracy of percutaneous sacroiliac screw (PSS) placement assisted by screw view model of navigation system for treatment of sacroiliac fractures.Data pertaining to 18 consecutive patients with posterior pelvic ring fracture who received sacroiliac screw fixation between January 2015 and July 2018 at the Second Hospital of Jilin University were retrospectively analyzed. Kirschner wires were placed under the guidance of navigation's screw view mode. The position of the screws was evaluated by computed tomography (CT) scan postoperatively. Fracture dislocation of sacroiliac joint was measured in axial, sagittal, and coronal views of 3 dimensional (3D) CT images preoperatively, postoperatively and at the last follow-up visit. The duration of trajectory planning, guide wire implantation time, screw placement time, intraoperative blood loss, and incidence of screw loosening and clinical complications were also assessed.A total of 27 screws were placed unilaterally or bilaterally into segments S1 or S2. Screw placement was rated as excellent for 88.9% of screws (n = 24), good for 7.4% (n = 2), and poor for 3.7% (n = 1). Preoperatively, the average fracture dislocation of sacroiliac joint on axial, sagittal, and coronal views was 14.3 mm, 9.6 mm, and 7.4 mm, respectively, and the corresponding postoperative figures were 5.6 mm, 3.2 mm, 4.1 mm, respectively. The corresponding correction rates were 60.8%, 66.7%, and 44.6%, respectively. The mean duration of trajectory planning was 6.5 min (2.7-8.9 min). Mean screw implantation time was 32 min (range, 20-53 min), and the mean guide wire implantation time was 3.7 min (range, 2.1-5.3 min). No clinical complications such as neurovascular injury, infection or screw loosening were observed on follow-up.The PSS placement under guidance of screw view model of navigation is a convenient, safe and reliable method.

Cement-augmented sacroiliac screw fixation with cannulated versus perforated screws - A biomechanical study in an osteoporotic hemipelvis model

INTRODUCTION

Cement-augmentation is a well-established way to improve the stability of sacroiliac screw fixation in osteoporosis-associated fragility fractures of the posterior pelvic ring. However, to date little is known about the influence of different techniques of cement augmentation on construct stability. The aim of this study was to evaluate the primary stability of cement-augmented sacroiliac screw fixation with cannulated versus perforated screws under cyclic loading.

MATERIALS AND METHODS

A total of eight fresh-frozen human cadaveric hemipelvis specimens with osteoporosis were used. After generating ventral osteotomies on both sides of the sacrum, each specimen was treated using a cement-augmented cannulated screw on one side and a cement-augmented perforated screw on the other side. Afterwards, axial cyclic loading was performed.

RESULTS

No statistically significant difference was found between cannulated and perforated screws concerning maximum load (356.25 N versus 368.75 N, p = 0.749), plastic deformation (1.95 mm versus 1.43 mm, p = 0.798) and stiffness (27.04 N/mm versus 40.40 N/mm, p = 0.645).

CONCLUSIONS

Considering the at least equivalent results for perforated screws, cement augmentation via perforated screws might be an interesting option in clinical practice because of potential advantages, e.g. radiological control before cement application, reduced risk of cement displacement and time saving.

Fragility fractures of the sacrum occur in elderly patients with severe loss of sacral bone mass

INTRODUCTION

Patients suffering from osteoporosis-associated fragility fractures of the sacrum (FFS; also termed sacral insufficiency fractures) are increasingly observed. They have typical fracture patterns with fracture lines located in the sacral ala. When treating these patients operatively, iliosacral screw loosening is not uncommon. We aimed to study the sacral bone mass in patients presenting with a FFS using 3D statistical models.

MATERIALS AND METHODS

3D models of averaged Hounsfield units (HU) were generated based on CT scans from 13 patients with a unilateral FFS (mean age 79.6 years; 11 females, 2 males). The control group without fractures consisted of 28 males and 32 females (mean age of 68.3 years). A virtual bone probe along the trans-sacral corridors S1 and S2 was taken.

RESULTS

The bone mass distribution in the fractured sacra was similar to the control group, however, with overall lower HU. Large zones of negative HU were located in the sacral ala. In the fractured sacra, the HU in the sacral ala was significantly lower on the non-injured side when comparing to the fractured side (p < 0.001) as well as compared to the non-fractured group (p < 0.001). Low bone mass was observed in sacral body S1 (40 HU) and S2 (20 HU).

CONCLUSIONS

The extensive area of negative HU may explain the fracture location in the sacral ala. The low HU in the sacral bodies advocates the use of trans-sacral implants or augmented iliosacral screws to enhance the strength of fracture fixation. The increased HU in the fractured ala could be explained by fracture-asssociated hemorrhage and can be used as a diagnostic tool.

[Traumatology in the elderly : Multimodal prevention of delirium and use of augmentation techniques]

Recent data show that 20-80% of surgery patients are affected by delirium during inpatient clinical treatment. The medical consequences are often dramatic and include a 20 times higher mortality and treatment expenses of the medical unit increase considerably. At the University Hospital of Münster a multimodal and interdisciplinary concept for prevention and management of delirium was developed: all patients older than 65 years admitted for surgery are screened by a specialized team for the risk of developing delirium and treated by members of the team if there is a risk of delirium. Studies proved that by this multimodal approach the incidence of delirium was lowered and therefore the quality of medical care improved.When surgical treatment of fractures in the elderly is required, limited bone quality as well as pre-existing implants can complicate the procedure. Secondary loss of reduction after osteosynthesis and avulsion of the implant in particular must be prevented. Augmentation of the osteosynthetic implant with bone cement can increase the bone-implant interface and therefore stability can be improved. Additional intraoperative 3D imaging can be necessary depending on the localization of the fracture. In biomechanical studies we could prove greater stability in the osteosynthesis of osteoporotic fractures of the distal femur when using additional bone cement; therefore, the use of bone cement is an important tool, which helps to prevent complications in the surgical treatment of fractures in the elderly. Nevertheless, special implants and technical skills are required and some safety aspects should be considered.

In-screw polymethylmethacrylate-augmented sacroiliac screw for the treatment of fragility fractures of the pelvis: a prospective, observational study with 1-year follow-up

BACKGROUND

The incidence of pelvic ring fractures in the elderly significantly increased. Because of persistent pain and immobilization associated with this injury, surgical treatment is recommended. To minimise comorbidities and surgical risk, percutaneous techniques are becoming more relevant. In-screw cement augmentation of sacroiliac screw fixation is a promising procedure; however, clinical follow-up data remain scarce. This study investigated the safety and possible complications of the procedure along with a 1-year follow-up.

METHODS

Thirty-four patients (treated with 43 screws) were prospectively included. Data on patients' age and sex, the mechanism of accident, fracture pattern, duration of hospital stay, surgery and adverse events were recorded. Data were obtained postoperatively on the reduction of pain and complications, such as infection, cement leakage and neurological deficits, and at 1-year follow-up on pain, quality of life according to the 12-Item Short Form Survey and mobility. Implant failure was defined as retraction or dislocation of screws and was also documented.

RESULTS

Screw-related complications occurred with 2 of 43 screws. None of these complications were related to cement augmentation. In-hospital adverse events occurred in 6 of 34 patients. Postoperative pain, measured by the visual analogue scale, was significantly reduced from 6.7 ± 1.4 preoperatively to 2.7 ± 1.0 postoperatively (p < 0.001). Although patients complained of pain at the 1-year follow-up, they reported a significant decline compared with pain at admission (3.4 ± 2.3; p < 0.001). Results on the quality of life were comparable with those for the age- and gender matched German population. All patients were mobile, and no implant failure was detected.

CONCLUSIONS

The results indicate that in-screw augmented sacroiliac screw fixation for fragility fractures of the pelvis is a safe technique. Pain was significantly reduced immediately after surgery compared to the preoperative state. Furthermore, significant pain reduction after one year compared to the preoperative state and quality of life was comparable to the age- and gender- matched German population. Thus, we recommend in-screw augmentation for screw fixation for sacral fragility fractures of the pelvis following failed conservative treatment.

Symphyseal fixation in open book injuries cannot fully compensate anterior SI joint injury-A biomechanical study in a two-leg alternating load model

INTRODUCTION

In open book injuries type Tile B1.1 or B1.2 also classified as APC II (anteroposterior compression), it remains controversial, if a fixation of the anterior ring provides sufficient stability or a fixation of the posterior ring should be included. Therefore the relative motion at the sacroiliac joint was quantified in a two-leg alternating load biomechanical pelvis model in the intact, the injured and the restored pelvis.

METHODS

Fresh-frozen intact (I) pelvises (n = 6) were subjected to a non-destructive cyclic test under sinosuidal axial two-leg alternating load with progressively increasing amplitude. Afterwards an open book injury (J) including the anterior ligament complex of the left sacroiliac joint, the sacrospinal and sacrotuberal ligaments (Tile B1.1) was created and the specimens were retested. Finally, the symphysis was stabilized with a modular fixation system (1-, 2- or 4-rod configuration) (R) and specimens were cyclically retested. Relative motion at the sacroiliac joint was captured at both sacroiliac joints by motion tracking system at two load levels of 170 N and 340 N during all tests.

RESULTS

Relative sacroiliac joint movements at both load levels were significantly higher in the J-state compared to the I-state, excluding superoinferior translational movement. With exception of the anteroposterior translational movement at 340N, the relative sacroiliac joint movements after each of the three reconstructions (1-, 2-, 4-rod fixation) were significantly smaller compared to the J-state and did not differ significantly to the I-state, but stayed above the values of the latter. Relative movements did not differ significantly in a direct comparison between the 1-rod, 2-rod and 4-rod fixations.

CONCLUSION

Symphyseal locked plating significantly reduces relative movement of the sacroiliac joint in open book injuries type Tile B1.1 or B1.2 (APC II) but cannot fully restore the situation of the intact sacroiliac joint.