There lack biomechanical studies of different Iliosacral screw (ISS) techniques in treating Tile C1.3 pelvic fracture. This study aimed to evaluate the biomechanical effects of five ISS techniques at two angles of sacral slope (SS). Six cadaveric Tile C1.3 pelvic fracture specimens were subjected to 500 N compressive force in two-leg stance at 30° and 40° SS. They were fixed randomly with S1 ISS, S1 trans-iliac-trans-sacral screw (TITSS), S2 TITSS, S1 ISS + S2 TITSS, and S1 TITSS + S2 TITSS. Displacement and rotation were measured and analyzed. The S1 TITSS reduced the total, lateral and vertical displacement compared with the S1 ISS, and provided more vertical stability than the S2 TITSS. The S1 TITSS + S2 TITSS ensured more vertical stability than the S1 ISS + S2 TITSS, whereas it did not improve the pelvic stability compared to the single S1 TITSS. The S1 ISS + S2 TITSS enhanced total, lateral and vertical stability compared to single S1 ISS. The vertical displacement at 40° SS tended to be greater than that at 30° SS. This study demonstrated biomechanical advantages of different ISS and potential effect of SS on pelvic stability, which may help making ideal clinical choices.
Article
Biomechanical comparison of five iliosacral screw fixation techniques for Tile C1.3 pelvic fracture under two-legged standing load: a cadaver study
https://doi.org/10.21203/rs.3.rs-4005527/v1
This work is licensed under a CC BY 4.0 License
Version 1
posted
You are reading this latest preprint version
Biomechanical study
lliosacral screw
Pelvic fracture
Sacral slope
Tile C1.3 pelvic fracture is common fracture that cause vertical and rotational instability, desiderating early surgical treatment to reduce such long-term complications as fracture nonunion, neurological dysfunction, and gait abnormalities1. Common open surgery and internal fixation include lumbopelvic fixation and plate-screw fixation, but they can easily cause neurovascular lesion, infection, and poor surgical wound healing2.
Percutaneous iliosacral screw (ISS) fixation was first reported in 19893, which causes less iatrogenic injury, shortens operation time, reduces wound infection, and has gradually become an ideal treatment for pelvic fracture 4. The ISS fixation is considered as “central fixation”5 and has strong resistance to vertical shear and torsion 3. The most widely used osseous fixation pathways (OFP) are the first sacral vertebrae (S1) and the second one (S2). The S1 include the standard ISS and trans-iliac-trans-sacral screw (TITSS)6, while the S2 always include TITS7. Different ISS are combined to treat Tile C1.3 pelvic fractures clinically. Researchers developed in vitro pelvis models with one-legged stance 8 or two-legged ones 9 to evaluated posterior pelvic ring fixation. However, there are no study that compare the above fixation with in-vitro biomechanical experiments under two-legged standing load.
The sacral slope (SS) plays a significant role in spinal sagittal balance and equals to pelvic incidence minus pelvic tilt. With a larger SS, the sacrum experiences more vertical shear, and this may affect the stability of different ISS fixations 10. Unfortunately, the biomechanical effect of the SS on different ISS fixation has not been well studied.
This study developed an in vitro and SS-adjustable biomechanical model in two-legged stance. Motion at ipsilateral S1 anterior foramen was measured under 500N force. The aims of this study were to evaluate the biomechanical stability of five ISS fixation methods for Tile C1.3 pelvic fractures, and the effect of the SS on ISS fixation. This study may provide a meaningful reference to the use of iliosacral screw fixations for Tile C1.3 pelvic fracture in clinical practice with consideration of the SS.
Specimens and Tile C1.3 Pelvic Fracture Model
This study used six fresh-frozen male cadaveric pelvises (mean age 40.5 years, range 25–65 years) from the Department of Anatomy. Use of cadaveric specimens in this study was approved by the Third Affiliated Hospital of Southern Medical University ethics committee under the code 2021-Ethical-Review-008. The procedures performed in this study were carried out in accordance with relevant guidelines and regulations. Informed consent of the donor's next of kin was obtained. The lumbar vertebrae were detached, and the main pelvic ligaments were preserved, such as the sacroiliac joint ligaments, the sacrospinous ligament and the sacrotuberous ligaments. X-rays of each specimen in anteroposterior, inlet and outlet view were performed to rule out any tumor, fracture, congenital anomalies, and severe osteoporosis. The specimens were kept at -20℃ and thawed at room temperature 12 hours prior to testing. Saline was sprayed to the surface during the tests to maintain the soft tissue hydration. An oscillating saw blade was employed to create a trans-obturator pubic osteotomy and a posterior ring osteotomy from the left first and second sacral foramen to the left sacral ala, in order to construct a Tile C1.3 pelvic fracture. (Fig. 1)
Fracture Fixation
For each specimen, the anterior pelvic ring was fixed with an internal fixator (INFIX) (Double Medical Technology, Inc., Xiamen, China), while the sacral fracture was fixed with five different lumbopelvic fixation (Weihai Weigao MEDICAL Devices Co., Weihai, China) in random order. X-ray examination was performed to verify proper reduction and fixation. The five fixation methods of the posterior pelvic ring were (1) S1 ISS (Group 1, Fig. 2A-C); (2) S1 TITSS (Group 2, Fig. 2D-F); (3) S2 TITSS (Group 3, Fig. 2G-I); (4) S1 ISS combined with S2 TITSS (Group 4, Fig. 2J-L); (5) S1 TITSS combined with S2 TITSS (Group 5, Fig. 2M-O). The screws used for the fixations were ϕ7.3 mm cannulated half-threaded screws. Fracture fixation was performed by the same skillful surgeon. Anteroposterior, inlet and outlet view of pelvic X-rays of different fixation were shown in Fig. 2.
In vitro Pelvic Loading Model (Fig. 3)
The upper part of the S1 body was drilled with 4 to 5 short screws and embedded with dental plaster in a PVC casting mold, keeping the S1 superior endplate horizontal. The end of the loading structure is spherical, which was matched smoothly with the upper part of the plaster and allowed the pelvic specimen to rotate and move during loading.
Based on the CT scan data of healthy male volunteers, two metal 3D printed femoral heads were fabricated, with a femoral neck-shaft angle of 130° and an anteversion angle of 15°. The metal femoral heads were inserted into the acetabulum of the pelvic specimen and fixed to the platform of the material testing machine.
The 2.5-mm-diameter steel cables were attached to the anterior superior iliac spines of the pelvic specimen on both sides and connected by two pulleys that were fixed to the platform of the material testing machine. By adjusting the length of the cables, the whole specimen could rotate around the hip joints and the sacral slope could be changed. These cables mimicked the function of the hip flexors and kept the pelvic balance under loading.
Biomechanical Testing
Parallel to the S1 endplate, a 1.0 mm Kirschner wire was inserted for the measurement of the sacral slope. The displacement and rotation between fracture ends at the ipsilateral S1 foramen were measured for each fixation under loading at two sacral slopes of 30° and 40° (Fig. 4). An axial compressive force ranging from 50 N to 500 N at a rate of 5 N/s was applied to the S1 vertebrae via the loading fixture by a servo electromagnetic material testing machine (E10000Puls, Instron Ltd., Norwood, MA, US) for three cycles.
Five 2.0 mm Kirschner wires were drilled into the bilateral sacral alar, bilateral iliac bones, and the upper pubic ramus between the pubic symphysis and the fracture line. Each Kirschner wire was attached with four infrared LED markers. Three-dimensional motion of the markers was measured by an optotrack camera system (Certus, NDI, Waterloo, CAN), with data sampling frequency set at 20 Hz.
Data Analysis
At the lower edge of anterior foramen, a virtual point at the sacral fracture line was set as the origin of a three-dimensional coordinate system (Fig. 1). The displacement and rotation between fragment consisted the displacement Tx in the left-right direction, Ty in the up-down direction, and Tz in the anterior-posterior direction, as well as flexion-extension Rx, axial-rotation Ry, and lateral-bending Rz based on the conventional spinal motion analysis, respectively. Using the following formula, total displacement (Ttotal) was also calculated:
$${T}_{total}=\sqrt{{T}_{x}^{2}+{T}_{y}^{2}+{T}_{z}^{2}}$$
All data analyses were performed using STATISTICA software (v.7, Dell, TX, USA). Results are presented as means with standard deviations. Analysis of variance with repeated measures in a generalized linear model was used to analyze the effects of five ISS fixation techniques in Tile C1.3 pelvic fractures at different sacral slope. Student-Newman-Keuls (SNK) test was used to analyze the differences between groups, provided that the effects of the factors were significant. The significance level was placed at p < 0.05.
In this study, 5 types of fixation were tested for loading and motion in 6 specimens, and no significant screw loosening of anterior or posterior ring fixation, or destruction of the specimens was observed. The mean and standard deviation of the displacement and rotational motion of the fracture end of the left S1 foramen under 500 N of lumbar axial compressive force are given in Table. 1. The p-value of the SNK test results of lateral and vertical displacement of the fracture end under different SS were shown in Table. 2 and Table. 3.
The S1 TITSS significantly improved stability compared with S1 ISS. Specifically, the S1 TITSS fixation significantly reduced the total (p<0.001), left and right (p = 0.001) and vertical (p<0.001) displacement of the fracture fragments, and the largest reduction range was reduced from 1.52mm, 0.36mm, and 1.20mm to 0.85mm, 0.22mm, and 0.49mm, respectively. At the 30° SS, the vertical stability of the S1 TITSS combined with S2 TITSS was higher than that of the S1 ISS combined with S2 TITSS (0.36mm VS 0.57mm, p = 0.004). (Table. 1 to 3)
As can be seen from the tables, the S1 TITSS can significantly improve the vertical stability of the model compared to the S2 TITSS. At the 40° SS, the vertical displacement decreases from 0.67mm to 0.49mm (p = 0.008); at 30°SS, the vertical displacement decreases from 0.71mm to 0.45mm (p=<0.001). (Tables. 1 and 3)
S1 ISS combined with S2 TITSS significantly improved stability compared to S1 ISS. Specifically, the S1 ISS combined with S2 TITSS fixation significantly reduced the total (p = 0.002), left and right (p=<0.001) and vertical displacement (p=<0.001) of the fragments. The largest reduction ranged from 1.52mm, 0.36mm, 1.20mm to 0.87mm, 0.24mm, 0.54mm, respectively. Surprisingly, the S1 TITSS combined with S2 TITSS did not significantly improve the total, lateral and vertical stability of the model compared to the single S1 TITSS at both 30° and 40° SS. (Tables. 2 and 3)
There were no significant differences in the displacement and rotation at two SS in each ISS fixation. (Fig. 4). However, in most cases, the vertical displacement at 40° SS tended to be greater than that at 30° SS (Table. 1), indicating SS a role in the vertical stability.
Our aim was to evaluate the biomechanical effects of five ISS techniques at two angles of SS under two-legged stance. We found that the S1 TITSS provided sufficient pelvic stability compared to S1 ISS and S2 TITSS. For those without S1 TISS OFP, the combination of S1 ISS and S2 TISS was an ideal choice to maintain pelvic stability. The SS had potential effect on the vertical stability of different iliosacral screw fixation.
Treatment for Tile C1.3 pelvic fracture is challenging, in which the iliosacral screw fixation is gaining more favor in clinical practice11. Since the biomechanical stability of iliosacral screw fixations was affected by pelvic morphology (such as OFP and SS) and screw-bone purchase, there is no consensus on which one of fixations suits best for treating Tile C1.3 pelvic fracture.
The present study showed that in terms of single screw fixation for Tile C1.3 pelvic fracture, the S1 TITSS provided better overall pelvic stability than the S1 ISS, and stronger vertical stability than the S2 TITSS. Jonathan et al. found that the bone density of the S1 segment is significantly higher than that of S2 and S3, and the bone density of the sacroiliac joint is higher than that of the sacral body at the same level12. In the elderly pelvis, the sacrum bone mass is drastically reduced, typically in the sacral body13, but the sacroiliac joint shows signs of local sclerosis14. This illustrates the need for TITSS fixation in the treatment of pelvic fractures, as it allows screws to go through bilateral high-density area and thus enhances internal fixation stability. Theoretically, the S1 TITSS is more stable than the S1 ISS or the S2 TITSS, which is consistent with our experimental results. The sacral regions with the highest bone density are near the anterior 1/3 of the S1 body15 and the superior endplate of S116, while the central part of the S1 segment and sacral alar are mainly composed of cancellous bone, providing insufficient purchase for the screw fixation especially in the elderly17. In this study, the S1 ISS was drilled perpendicular to the fracture line, with the thread located in the center part of the S1 body, which was common in clinical practice.
However, due to the high variability of sacrum morphology, 20%~25% of patients do not have osseous pathway for S1 TITSS18. Routt et al.19 first described the qualitative features of superior sacral dysplasia, where they reported six key characteristics to define sacral dysmorphism. The incidence of sacrum deformity in adults is about 30–40%20, and the safe area of the upper part of the metamorphotic sacra is 36% smaller than normal ones21. The misshaped upper foramina and increased alar slope are the main risk factors for screw dislocation, which limits the insertion of S1 TITSS and can lead to the "in-out-in" phenomenon and cause damage to blood vessels and nerves in front of the sacrum22. When the S1 TITSS pathway is not available, only S1 ISS can be inserted. However, our study shows that the stability of S1 ISS is the weakest of the five experimental groups. The S1 ISS combined with S2 TITSS can significantly reduce total, lateral, and vertical displacement of the fracture fragments compared to the S1 ISS. Therefore, we do not recommend using S1 ISS only to fix the Tile C1.3 pelvic fractures, and that additional iliosacral screw shall be added.
Although some scholars showed that compared with the S1 segment, the trans-iliac trans-sacral osseus pathway of the S2 segment was shorter and the safe space for nailing was smaller, but the incidence of structural variation was lower23. Vivek et al. reported that up to 68.6% of patients had the S2 TITSS pathway24. Jonathan et al. confirmed through computed tomography (CT) that the bone density of the posterior ilium/sacroiliac joint (PISJ) was higher than that of the sacrum body in the same segment level12. Based on the facts mentioned above, internal fixation that involved the S2 segment were all TITSS to ensure basic pelvic stability in this study. This study proves that the total biomechanical stability of S2 TITSS was higher than that of the S1 ISS, but its vertical stability is weaker than that of S1 TITSS. Our analysis is that taking the perpendicular line of the center of gravity as a reference, the sagittal position of S2 is on the backward compared to S1, and when S2 is fixed solely, the force arm of the upper limb and trunk weight increases, and the S2 screw is subjected to greater vertical shear force, resulting in the increase of the vertical displacement of the bone at both ends of the fracture line. Worse still, the bone mineral density of the S2 is lower than the S117 and the S2 pathway is shorter, making it unsafe to fix the S2 segment solely by a single TITSS. We recommend that when using S2 sacroiliac screw fixation, surgeons should try to penetrate the screws through bilateral sacroiliac joint, which is also consistent with the findings of Joseph et al7. After fixing with the S2 TITSS, it is recommended to insert another S1 iliosacral screw.
Some studies showed that for patients with Tile C-type pelvic injury, two screws in different planes should be inserted to strengthen rotational resistance and overall stability of the pelvic specimens25. However, our experimental results showed S1 TITSS combined with S2 TITSS did not improve the stability when compared with S1 TITSS alone. Given that S1 TITSS insertion is not suitable for all patients, we recommended using two screws of different segments when upper sacral deformity prevents penetration of the S1 TITSS. That is, an S2 TITSS is inserted on the basis of the S1 ISS. If the patient has the S1 TITSS OFP, drilling in only one S1 TITSS is rigid enough to maintain the pelvis stability. There is no need to insert an additional S2 screw, which help reduce the surgical time, radiation exposure, and incidence of iatrogenic vascular nerve injury in the gluteal area.
Roussouly et al.26 analyzed 160 adult volunteers who underwent X-rays of the spine in a standard standing position, and the mean SS was 39.9 ± 8.2°. Moreover, Zhou et al.27 reported the mean sacral slope was 34.0 ± 7.1°. The SS is an important parameter of spinal sagittal balance. Larger SS exposes the pelvis to more vertical shear, and thus affect the stability of different ISS fixations. Therefore, two angles of 30° and 40° were set in the present study to analyze the effect of sacral slope on iliosacral screw fixation was appropriate. However, this study did not reflect the effect of SS on the ISS fixations. We hypothesized that it might be possible that ISS belongs to central fixation, which has high mechanical stability, and the difference of ten degrees is not enough to induce significant change in pelvic instability. This also reflects the fact that the sacroiliac screws can fix the Tile C1.3 pelvic fractures rigidly. This study simulated no bilateral fractures but unilateral ones, which also failed to induce obvious instability. Later, we will further induce a more unstable state of the pelvis by increasing the SS in a reasonable section, using the Tile C3 pelvic fracture models, and using non-central fixation such as plates or lumbo-pelvic fixation to verify the effect of SS on the biomechanical properties of iliosacral screw fixation.
The biomechanical model used in this study, originally developed by Hearn et al.9, has been widely accepted and utilized by numerous studies to evaluate the effectiveness of pelvic fixation28. Specifically designed for assessing pelvic fractures, the two-legged standing model accurately replicates the physiological loading on the pelvis. In this study, two metal femoral heads are employed to support the bilateral acetabulum, ensuring minimal interference with pelvic motion during loading. Steel cables, anchored to the anterior superior iliac spine anterior to the center of the femoral head, adjust the SS and simulate the action of the hip flexors29. This setup effectively maintains pelvic balance under loading conditions.
This study had several limitations. First, the number of specimens in this study was small and sex differences were not considered. Second, even though the frozen pelvic specimens could better reflect the in vivo conditions with the key ligaments reserved30, the individual differences of them were large compared with the artificial pelvic model31. A repeated-measures study-design was used in this study, which reduced the effect of individual differences to some extent but still reflected the effects of different factors. Third, changing internal fixations during testing may affect the strength of the bone-screw interface, especially the trans-iliac-trans-sacral OFP. In this study, an experienced clinician placed the screws as close as possible to the original screw trajectory and achieved similar screw purchase during instrumentation. Also, the 500 N axial compressive load was used and should not damage the bone-screw interface based on previous studies32. Finally, the effects of flex-extension, axial rotation and lateral bending torque on fixation stability were not considered in this study during the loading test.
Iliosacral screws are ideal fixation in treating Tile C1.3 pelvic fractures. In this study, we developed an in vitro Tile C1.3 pelvic fractures model under two-legged standing load, which proved that the S1 trans-iliac-trans-sacral screw enhance the overall and vertical stability of the pelvis compared to the S1 iliosacral screw and S2 trans-iliac-trans-sacral screw. If the patient has an S1 trans-iliac-trans-sacral screw osseous pathway, sufficient pelvic stability can be achieved by drilling only one S1 trans-iliac-trans-sacral screw, and other iliosacral screws are not needed. If not, the placement of S1 iliosacral screw combined with an S2 trans-iliac-trans-sacral screw could enhance the overall stability. Due to the low bone density of the S2 segment, it is recommended to add an S1 iliosacral screw when we use S2 trans-iliac-trans-sacral screw. Our study also indicated the potential effect of sacral slope on the vertical stability of different iliosacral screw fixation.
Competing interests
The authors declare that they have no competing interests.
Author Contribution
Shicai Fan and Yingze Zhang designed the study. Sheqiang Chen and Haibo Xiang performed experiments. Qiguang Mai, Zhiyong Hou and Wei Chen collected the data. Shicai Fan and Qingan Zhu drafted the manuscript. Zhenhua Zhu and Yuhui Chen analyzed and interpreted the data. Yingze Zhang and Qingan Zhu revised the manuscript and provided final approval of the submitted version. All authors read and approved the final manuscript.
Acknowledgements
We would like to thank the following people for their efforts and help in the completion of this study: Zhiping Huang for testing, Fuming Huang, Xiangyuan Wen, Yuancheng Liu, Wenquan Xu and Jiacheng Li for the specimen preparation.
Data availability
Raw data is not publicly available but can be shared with the editors or referees upon request.
- Salari, P., Moed, B. R. & Bledsoe, J. G. Supplemental S1 fixation for type C pelvic ring injuries: biomechanical study of a long iliosacral versus a transsacral screw. J Orthop Traumatol 16, 293–300, doi:10.1007/s10195-015-0357-8 (2015).
- Wakayama, Y. et al. Clinical utility of minimally invasive posterior internal fixation within the pelvic ring using S2 alar iliac screws for unstable pelvic ring fracture. Injury 53, 3371–3376, doi:10.1016/j.injury.2022.08.035 (2022).
- Matta, J. M. & Saucedo, T. Internal fixation of pelvic ring fractures. Clin Orthop Relat Res, 83–97 (1989).
- Liu, F. et al. Iliosacral screw fixation of pelvic ring disruption with tridimensional patient-specific template guidance. Orthop Traumatol Surg Res 108, 103210, doi:10.1016/j.otsr.2022.103210 (2022).
- Collinge, C., Coons, D. & Aschenbrenner, J. Risks to the superior gluteal neurovascular bundle during percutaneous iliosacral screw insertion: an anatomical cadaver study. J Orthop Trauma 19, 96–101, doi:10.1097/00005131-200502000-00005 (2005).
- Maslow, J. & Collinge, C. A. Risks to the Superior Gluteal Neurovascular Bundle During Iliosacral and Transsacral Screw Fixation: A Computed Tomogram Arteriography Study. J Orthop Trauma 31, 640–643, doi:10.1097/bot.0000000000000996 (2017).
- Radley, J. M. et al. Bone density of first and second segments of normal and dysmorphic sacra. J Orthop Traumatol 21, 6, doi:10.1186/s10195-020-00545-9 (2020).
- Jordan, M. C. et al. The Anterior Subcutaneous Pelvic Ring Fixator: No Biomechanical Advantages Compared with External Fixation. J Bone Joint Surg Am 101, 1724–1731, doi:10.2106/jbjs.18.01363 (2019).
- Varga, E., Hearn, T., Powell, J. & Tile, M. Effects of method of internal fixation of symphyseal disruptions on stability of the pelvic ring. Injury 26, 75–80, doi:10.1016/0020-1383(95)92180-i (1995).
- Laouissat, F., Sebaaly, A., Gehrchen, M. & Roussouly, P. Classification of normal sagittal spine alignment: refounding the Roussouly classification. Eur Spine J 27, 2002–2011, doi:10.1007/s00586-017-5111-x (2018).
- Rommens, P. M. et al. Safety and efficacy of 2D-fluoroscopy-based iliosacral screw osteosynthesis: results of a retrospective monocentric study. Eur J Trauma Emerg Surg 47, 1687–1698, doi:10.1007/s00068-020-01362-9 (2021).
- Eastman, J. G., Shelton, T. J., Routt, M. L. C., Jr. & Adams, M. R. Posterior pelvic ring bone density with implications for percutaneous screw fixation. European journal of orthopaedic surgery & traumatology: orthopedie traumatologie 31, 383–389, doi:10.1007/s00590-020-02782-4 (2021).
- Wagner, D. et al. Fragility fractures of the sacrum occur in elderly patients with severe loss of sacral bone mass. Arch Orthop Trauma Surg 138, 971–977, doi:10.1007/s00402-018-2938-5 (2018).
- Ha, K. Y., Lee, J. S. & Kim, K. W. Degeneration of sacroiliac joint after instrumented lumbar or lumbosacral fusion: a prospective cohort study over five-year follow-up. Spine (Phila Pa 1976) 33, 1192–1198, doi:10.1097/BRS.0b013e318170fd35 (2008).
- Kim, J. W. et al. The incidence of and factors affecting iliosacral screw loosening in pelvic ring injury. Arch Orthop Trauma Surg 136, 921–927, doi:10.1007/s00402-016-2471-3 (2016).
- Ziran, N., Collinge, C. A., Smith, W. & Matta, J. M. Trans-sacral screw fixation of posterior pelvic ring injuries: review and expert opinion. Patient Saf Surg 16, 24, doi:10.1186/s13037-022-00333-w (2022).
- Salazar, D. et al. Investigation of bone quality of the first and second sacral segments amongst trauma patients: concerns about iliosacral screw fixation. J Orthop Traumatol 16, 301–308, doi:10.1007/s10195-015-0354-y (2015).
- Osterhoff, G. et al. Cement Augmentation in Sacroiliac Screw Fixation Offers Modest Biomechanical Advantages in a Cadaver Model. Clin Orthop Relat Res 474, 2522–2530, doi:10.1007/s11999-016-4934-9 (2016).
- Routt, M. L., Jr., Kregor, P. J., Simonian, P. T. & Mayo, K. A. Early results of percutaneous iliosacral screws placed with the patient in the supine position. J Orthop Trauma 9, 207–214, doi:10.1097/00005131-199506000-00005 (1995).
- Routt, M. L., Jr., Simonian, P. T., Agnew, S. G. & Mann, F. A. Radiographic recognition of the sacral alar slope for optimal placement of iliosacral screws: a cadaveric and clinical study. J Orthop Trauma 10, 171–177, doi:10.1097/00005131-199604000-00005 (1996).
- Gardner, M. J., Morshed, S., Nork, S. E., Ricci, W. M. & Chip Routt, M. L., Jr. Quantification of the upper and second sacral segment safe zones in normal and dysmorphic sacra. J Orthop Trauma 24, 622–629, doi:10.1097/BOT.0b013e3181cf0404 (2010).
- Berger-Groch, J. et al. Accuracy of navigated and conventional iliosacral screw placement in B- and C-type pelvic ring fractures. Eur J Trauma Emerg Surg 46, 107–113, doi:10.1007/s00068-018-0990-z (2020).
- Fu, S. et al. Comparison of the risk of breakage of two kinds of sacroiliac screws in the treatment of bilateral sacral fractures. Eur Spine J 23, 1558–1567, doi:10.1007/s00586-014-3313-z (2014).
- Trikha, V., Gaba, S., Kumar, A., Mittal, S. & Kumar, A. Safe corridor for iliosacral and trans-sacral screw placement in Indian population: A preliminary CT based anatomical study. J Clin Orthop Trauma 10, 427–431, doi:10.1016/j.jcot.2018.01.007 (2019).
- Zhang, R. et al. Percutaneous sacroiliac screw versus anterior plating for sacroiliac joint disruption: A retrospective cohort study. Int J Surg 50, 11–16, doi:10.1016/j.ijsu.2017.12.017 (2018).
- Roussouly, P., Gollogly, S., Berthonnaud, E. & Dimnet, J. Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position. Spine (Phila Pa 1976) 30, 346–353, doi:10.1097/01.brs.0000152379.54463.65 (2005).
- Zhou, S., Sun, Z., Li, W., Zou, D. & Li, W. The Pelvic Incidence Stratified Sagittal Spinopelvic Alignment in Asymptomatic Chinese Population With Different Age Groups. Global Spine J 12, 1821–1826, doi:10.1177/2192568221989647 (2022).
- Moed, B. R., O'Boynick, C. P. & Bledsoe, J. G. Locked versus standard unlocked plating of the symphysis pubis in a Type-C pelvic injury: a cadaver biomechanical study. Injury 45, 748–751, doi:10.1016/j.injury.2013.11.017 (2014).
- Ponsen, K. J., Joosse, P., Van Dijke, G. A. & Snijders, C. J. External fixation of the pelvic ring: an experimental study on the role of pin diameter, pin position, and parasymphyseal fixator pins. Acta Orthop 78, 648–653, doi:10.1080/17453670710014347 (2007).
- Comstock, C. P., van der Meulen, M. C. & Goodman, S. B. Biomechanical comparison of posterior internal fixation techniques for unstable pelvic fractures. J Orthop Trauma 10, 517–522, doi:10.1097/00005131-199611000-00001 (1996).
- Vigdorchik, J. M., Esquivel, A. O., Jin, X., Yang, K. H. & Vaidya, R. Anterior internal fixator versus a femoral distractor and external fixation for sacroiliac joint compression and single stance gait testing: a mechanical study in synthetic bone. Int Orthop 37, 1341–1346, doi:10.1007/s00264-013-1890-9 (2013).
- Berber, O., Amis, A. A. & Day, A. C. Biomechanical testing of a concept of posterior pelvic reconstruction in rotationally and vertically unstable fractures. J Bone Joint Surg Br 93, 237–244, doi:10.1302/0301-620x.93b2.24567 (2011).
Table. 1 The mean and standard deviation of fragments motion of the S1 foramen under compressive force.
|
|
p a |
Sacro Slope |
S1 ISS |
S1TITSS |
S2 TITSS |
S1 ISS +S2 TITSS |
S1 TITSS +S2 TITSS |
|
Tx (mm) |
0.031 |
40° |
0.36±0.15 |
0.22±0.04 |
0.24±0.08 |
0.24±0.06 |
0.21±0.03 |
|
30° |
0.31±0.12 |
0.23±0.05 |
0.23±0.04 |
0.24±0.08 |
0.22±0.04 |
||
|
Ty (mm) |
0.010 |
40° |
1.20±0.88 |
0.49±0.25 |
0.67±0.43 |
0.54±0.38 |
0.44±0.21 |
|
30° |
1.14±0.82 |
0.45±0.28 |
0.71±0.39 |
0.57±0.42 |
0.36±0.22 |
||
|
Tz (mm) |
0.909 |
40° |
0.75±0.33 |
0.62±0.28 |
0.63±0.11 |
0.60±0.16 |
0.60±0.23 |
|
30° |
0.73±0.29 |
0.69±0.25 |
0.71±0.18 |
0.65±0.19 |
0.72±0.48 |
||
|
Rx (°) |
0.055 |
40° |
0.96±0.89 |
0.71±0.46 |
1.05±0.84 |
0.88±0.83 |
0.64±0.42 |
|
30° |
0.95±0.64 |
0.77±0.47 |
1.09±0.79 |
0.94±0.82 |
0.58±0.41 |
||
|
Ry (°) |
0.285 |
40° |
1.13±1.41 |
0.48±0.18 |
0.74±0.96 |
0.70±0.90 |
0.34±0.09 |
|
30° |
1.18±1.33 |
0.46±0.22 |
0.81±1.02 |
0.82±1.08 |
0.42±0.18 |
||
|
Rz (°) |
0.063 |
40° |
0.66±0.37 |
0.32±0.14 |
0.42±0.33 |
0.37±0.27 |
0.28±0.12 |
|
30° |
0.61±0.34 |
0.31±0.12 |
0.44±0.33 |
0.31±0.18 |
0.26±0.13 |
a The p-value of the fixation methods at both 40° and 30° SS according to the repeated measures analysis of variance.
Table. 2 The p-value of the comparison results of left-and-right displacement of fragments under different SS.
|
|
S1 ISS |
S1TITSS |
S2 TITSS |
S1 ISS+ S2 TITSS |
S1 TITSS+ S2 TITSS |
|
S1 ISS |
|
0.042 |
0.039 |
0.041 |
0.038 |
|
S1 TITSS |
0.001 |
|
0.904 |
0.938 |
0.963 |
|
S2 TITSS |
＜0.001 |
0.968 |
|
0.828 |
0.980 |
|
S1 ISS+ S2 TITSS |
＜0.001 |
0.987 |
0.777 |
|
0.972 |
|
S1 TITSS+ S2 TITSS |
＜0.001 |
0.919 |
0.932 |
0.971 |
|
Table. 3 The p-value of the comparison results of vertical displacement of fragments under different SS.
|
|
S1 ISS |
S1TITSS |
S2 TITSS |
S1 ISS+ S2 TITSS |
S1 TITSS+ S2 TITSS |
|
S1 ISS |
|
＜0.001 |
＜0.001 |
＜0.001 |
＜0.001 |
|
S1 TITSS |
＜0.001 |
|
＜0.001 |
0.092 |
0.172 |
|
S2 TITSS |
＜0.001 |
0.008 |
|
0.018 |
＜0.001 |
|
S1 ISS+ S2 TITSS |
＜0.001 |
0.337 |
0.037 |
|
0.004 |
|
S1 TITSS+ S2 TITSS |
＜0.001 |
0.545 |
0.002 |
0.204 |
|
No competing interests reported.