Three-dimensional Digital Anatomical Measurement of Modified Sacroiliac Screws

Purpose To rebuild a model of the pelvis and effectively simulate the trajectory of modified sacroiliac screws, we measured the parameters of each screw and screw channel and assessed the safety and feasibility of the parameters in adults.Method and materials One hundred (50 males and 50 females) normal adult pelvic CT (computed tomography) images were randomly selected and imported into Mimics software to rebuild the three-dimensional pelvis model. In these models, each ideal channel of modified screws was simulated, and then we obtained the precise parameters of screws and channels using Mimics and Three-matic software.Results The results of the comparison (right vs. left) showed that there were no significant differences in any of the angles, radius or M1SI parameters (the first modified sacroiliac). However, one parameter (BS) of M2SI (the second modified sacroiliac), two parameters (AP and BS) of M3SI (the third modified sacroiliac), and three parameters (AP、BS、L) of M4SI (the fourth modified sacroiliac) were statistically significant (P < 0.05). The result of comparison (between genders) showed that there were no significant differences in M1SI and M2SI; in contrast, the radius, length and the α angle of M3SI and M4SI were significantly different between genders (P < 0.05), and the radius of M4SI required special attention. If the radius of the limiting screw channel was >3.50 mm, 52 cases (52%, 24 males and 28 females) could not complete the M4SI screw placement among 100 samples. If the radius of the limiting screw channel was >3.0 mm, a total of 10 cases (10%, 2 males and 8 females) could not complete the M4SI screw placement.Conclusion Through the measurement of 100 healthy adult real three-dimensional pelvic models, we obtained the parameters of each modified sacroiliac screw and measured the three angles of each screw based on international coordinates for the first time, which can instruct clinical application.

Clinical Analysis of Single and Double Sacroiliac Screws in the Treatment of Tile C1 Pelvic Fracture

We investigated the difference between fixation of single and double sacroiliac screws in the treatment of Tile C1 pelvic fractures. The data of 54 patients with Tile C1 pelvic fractures who were admitted to the trauma center of the Red Society Hospital Affiliated to Xi’an Jiaotong University between August 2016 and August 2020 were retrospectively analyzed. All patients with posterior pelvic ring injuries underwent fixation with sacroiliac screws assisted by a percutaneous robotic navigation system. The operative time, amount of intraoperative blood loss, and postoperative follow-up time between the two groups (single sacroiliac and double sacroiliac screw groups) were compared. The Matta and Majeed scores at the last follow-up were compared between the groups to evaluate fracture reduction and functional recovery. Forty-nine patients were followed up for 17.2 (±4.5) months and 16.2 (±3.4) months in the single and double sacroiliac screw groups, respectively. All patients had excellent fracture reduction immediately after surgery, according to the Matta score. All fractures healed without complications. There was no statistically significant difference in preoperative general information, amount intraoperative blood loss, intraoperative anterior ring fixation method, and postoperative follow-up time between the two groups ( P > 0.05 ). The operative time of the single sacroiliac screw group was shorter than that of the double sacroiliac screw group ( P < 0.05 ). At the last follow-up, the Matta score of the double sacroiliac screw group was significantly better than that of the single sacroiliac screw group ( P < 0.05 ), and there was no statistically significant difference in the Majeed functional scores ( P > 0.05 ). For Tile C1 pelvic fractures, double sacroiliac screw fixation of posterior ring injuries can provide a more stable treatment with no statistically significant difference in functional recovery.

Biomechanical study of Tile C3 pelvic fracture fixation using an anterior internal system combined with sacroiliac screws

Background How to perform minimally-invasive surgery on Tile C pelvic fractures is very difficult, and it is also a hot topic in orthopedic trauma research. We applied minimally-invasive treatment using an anterior internal fixator combined with sacroiliac screws. Objectives To compare the biomechanical properties of different fixation models in pelvic facture specimens, using an internal fixation system or a steel plate combined with sacroiliac screws. Methods Sixteen fresh adult cadaver pelvic specimens were randomly separated into four groups named A, B, C, and D. The four groups were respectively stabilized using a two-screwed, three-screwed, or four-screwed anterior internal fixator or a steel plate with sacroiliac screws. All models were tested in both standing and sitting positions. Vertical loads of 600 N were applied increasingly. Shifts of bilateral sacroiliac joints and pubis rupture were measured. Results The shifts in sacroiliac joints and pubis rupture in the standing position were all less than 3.5 mm, and the shifts in the sitting position were all less than 1 mm. In the standing position, the results of shifts in the sacroiliac joints were group C < group D < group B < group A. For comparisons between A:B and C:D, P > 0.05. For comparisons between A, B:C, and D, P < 0.05. The results of shifts in pubis ruptures were group D < group C < group B < group A. In the comparison between C:D, P > 0.05; for comparisons between A:B, A:C, A:D, B:C, and B:D, P < 0.05. In the sitting posture, the results of shifts in the sacroiliac joints were group C < group D < group B < group A, and the shifts in the pubis ruptures were group D < group C < roup B < group A. For comparison between C:D, P > 0.05. For comparisons between A:B, A:C, A:D, B:C, and B:D, P < 0.05. Conclusion Use of an anterior internal fixator combined with sacroiliac screws effectively stabilized Tile C3 pelvic fractures. The stability of specimens increased as the number of screws in the internal fixator increased.

Biomechanical Study of Tile C3 Pelvic Fracture Fixation Using an Anterior Internal System Combined With Sacroiliac Screws

BackgroundThis study aimed to investigate the effectiveness of different methods of fixation of Tile C3 pelvic fractures. We applied minimally-invasive treatment using an anterior internal fixator combined with sacroiliac screws. ObjectivesTo compare the biomechanical properties of different fixation models in pelvic facture specimens, using an internal fixation system or a steel plate combined with sacroiliac screws. MethodsSixteen fresh adult cadaver pelvic specimens were randomly separated into four groups named A, B, C and D. The four groups were respectively stabilized using a two-screwed, three-screwed, or four-screwed anterior internal fixator or a steel plate with sacroiliac screws. All models were tested in both standing and sitting positions. Vertical loads of 600 N were applied increasingly. Shifts of bilateral sacroiliac joints and pubis rupture were measured. ResultsThe shifts in sacroiliac joints and pubis rupture in the standing position were all less than 3.5 mm and the shifts in the sitting position were all less than 1 mm. In the standing position, the results of shifts in the sacroiliac joints were: Group C < Group D < Group B < Group A. For comparisons between A:B and C:D, P > 0.05. For comparisons between A, B:C, D, P < 0.05. The results of shifts in pubis ruptures were: Group D < Group C < Group B < Group A. In the comparison between C:D, P > 0.05, for comparisons between A:B, A:C, A:D, B:C, and B:D, P < 0.05. In the sitting posture, the results of shifts in the sacroiliac joints were: Group C < Group D < Group B < Group A, the shifts in the pubis ruptures were: Group D < Group C < Group B < Group A. For comparison between C:D, P > 0.05. For comparisons between A:B, A:C, A:D, B:C, and B:D, P < 0.05. ConclusionUse of an anterior internal fixator combined with sacroiliac screws effectively stabilized Tile C3 pelvic fractures. Among the options tested, a two-screwed internal fixator combined with sacroiliac screws was easier to operate. The stability of specimens increased as the number of screws in the internal fixator increased.

Biomechanical Modeling of Options for Internal Fixation of Unilateral Fractures of the Sacrum

Relevance. Currently, the stability of various options for the fixation of sacral fractures by the finite element method has not been sufficiently studied.Purpose — the biomechanical characteristics of two variants of internal fixation of unilateral sacral fractures by various implants and the localization of the line of its fracture with respect to the articular facet of the L5-S1 vertebrae were studied.Materials and Methods. Using the finite element method, we studied the biomechanical characteristics of two options for fixing a one-sided longitudinal fracture of the sacrum with different localization of the line of its fracture: outside, inside and directly on the joint facet L5-S1. Two fixation options are considered: cannulated sacroiliac screws and a similar option in combination with a bilateral lumbar-pelvic transpedicular system.Results. The stresses in implants and bone under compression load and torso forward or backward are almost the same in all models. In the model of fixation with a sacroiliac screw of a one-sided longitudinal sacral fracture, the line of which passes through the articular process S1 of the vertebra (Isler II type), the greatest stress in the screws under compression load and bending moment was 619.7 MPa, which exceeds the yield strength of the titanium alloy and can damage the implants. In all models where the transpedicular system additionally acted as fixing structures, a decrease of 42–77% of maximum displacements was noted, by 28–79% of equivalent stresses in implants under all types of loads, while the equivalent stresses in the bone structures did not differ significantly. In models where the transpedicular system was additionally applied, a decrease of 42–77% of maximum displacements was noted, by 28-79% of stresses in implants under all types of loads, while the stresses in the bones did not differ much.Conclusion. In all cases of localization of the line of unilateral fracture of the sacrum, the use of a transpedicular system in combination with sacroiliac screws is more stable from the point of view of biomechanics. The most unstable is a one-sided longitudinal fracture of the sacrum passing through the facet L5-S1.

Anatomical conditions and patient-specific locked navigation templates for TSS placement

Objective To analyse the anatomical conditions of transverse sacroiliac screws about the S1 and S2 segments in order to develop and validate a locked navigational template for transverse sacroiliac screw placement. Methods The CT data of 90 normal sacra were analysed. The long axis, short axis and lengths of transverse sacroiliac screw cancellous corridors were measured through 3D modelling. A patient-specific locked navigation template based on simulated screws was designed and 3D printed and then used to assist in transverse sacroiliac screw placement. The operative time, intraoperative blood loss, incision length, and radiation times were recorded. The Matta criteria and grading score were evaluated. The entry point deviation of the actual screw placement relative to the simulated screw placement was measured, and whether the whole screw was in the cancellous corridor was observed.Results S1 screws with a diameter of 7.3 mm could be inserted into 69 pelvises, and S2 screws could be inserted in all pelvises. The S1 cancellous corridor had a long axis of 25.44±3.32 mm in males and 22.91±2.46 mm in females, a short axis of 14.21±2.19 mm in males and 12.15±3.22 mm in females, a corridor length of 153.07±11.99 mm in males and 151.11±8.73 mm in females, and a proportional position of the optimal entry point in the long axis of the cancellous corridor of 35.96±10.31% in males and 33.28±7.2% in females. There were significant differences in the corridor long axis and corridor short axis between sexes (p<0.05), and there were no significant differences in corridor length and proportional position of the optimal entry point in the long axis of the cancellous corridor between sexes (p>0.05). The S2 cancellous corridor had a long axis of 17.58±2.36 mm in males and 16±2.64 mm in females, a short axis of 14.21±2.19 mm in males and 13.14±2.2 mm in females, a corridor length of 129.95±0.89 mm in males and 136.5±7.96 mm in females, and a proportional position of the optimal entry point in the long axis of the cancellous corridor of 46.77±9.02% in males and 42.25±11.95% in females. There were significant differences in the long axis, short axis and corridor length (p<0.05). There was no significant difference in the proportional position of the optimal entry point in the long axis of the cancellous corridor (p>0.05). A total of 20 transversal sacroiliac screws were successfully inserted into 10 patients with the assistance of locked navigation templates. Nineteen screws were grade 0, 1 screw was grade 1, and there were no postoperative complications of infection or nerve root injury. All screw entry point deviations were shorter than the short axis of the cancellous corridor, and all screws were located completely within the cancellous corridor.Conclusion Approximately 76% of males and females can accommodate screws with diameters of 7.3 mm in S1, and all persons can accommodate the same screw in S2. From the standard lateral perspective of the sacrum, the optimal entry point of the transverse screw is in the first 1/3 of the cancellous corridor for S1 and the centre of the cancellous corridor for S2. The patient-specific locked navigation template assisted in transverse sacroiliac screw placement with little trauma and fluoroscopy radiation and secure screw placement.

Posterior surgery assisted by three dimensional printing technology in the treatment of sacroiliac joint tuberculosis

Background Three-dimensional (3D) printing is becoming increasingly important in spinal surgery, and few literatures have reported the surgical management for sacroiliac joint tuberculosis assisted by three dimensional printing technology. Purpose The study aim to assess the efficacy and feasibility of surgical treatment in sacroiliac joint tuberculosis (SJT) by posterior sacroiliac screws fixation, debridement and fusion, which assisted by three dimensional printing technology. Method Twenty-six patients with sacroiliac joint tuberculosis treated by surgery in our department between January 2008 and December 2015 . All the patients were divided into two group base on three dimensional printing technology: 11 cases in Group A underwent posterior debridement, fusion and sacroiliac screws fixation, and 15 cases in Group B underwent posterior debridement, bone graft, sacroiliac screws fixation, and three dimensional printing technology. Clinical and radiographic results for the two groups were analyzed and compared. Results All patients were followed up with an average 33.8±7.9 months (24–48 months). The sacroiliac joint tuberculosis was completely cured and the grafted bones were fused in all 26 patients. No injured nerve or other severe complications occurred in both groups. Group B achieved much better results in time of operation, intra-operative blood loss, and number of intra-operative fluoroscopy than group A ( p < 0.05). There were no significant differences between the two groups in ESR, fusion time, and VAS score in the last follow-up ( p >0.05). Conclusions The three dimensional printing technology can achieve the better effect in the treatment of sacroiliac joint tuberculosis. Posterior surgery assisted by three dimensional printing technology in the treatment of sacroiliac joint tuberculosis has the characteristics of shorter operative time, less bleeding, and less number of intra-operative fluoroscopy.