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.

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.

Clinical application of anterior ring internal fixator system combined with sacroiliac screw fixation in Tile C pelvic fracture treatment

Background How to perform minimally invasive surgery for Tile C pelvic fracture is a major problem in clinical practice. We performed minimally invasive surgery for Tile C pelvic fracture using anterior ring internal fixator systems combined with sacroiliac screw fixation. Objective To investigate the advantages and efficacy of anterior ring internal fixator systems combined with sacroiliac screw fixation in the treatment of Tile C pelvic fracture. Methods From May 2017 to May 2020, 27 patients with Tile C pelvic fracture who underwent anterior ring internal fixator system combined with sacroiliac screw fixation (group A) and 21 patients with Tile C pelvic fracture who underwent plate-screw system combined with sacroiliac screw fixation (group B) were retrospectively analyzed. Results All 48 patients were followed up for more than 12 months, all fractures healed within 3–6 months. The operative time, intraoperative bleeding volume, blood transfusion volume, incision length, hospital stay, complication rate and Majeed score were 63.5 ± 10.7 min, 48.3 ± 27.9 ml, 0 ml, 4.5 ± 0.8 cm, 10.2 ± 2.7 d, 3.7% and 89.7 ± 4.6 points, respectively, in group A and 114.8 ± 19.1 min, 375 ± 315.8 ml, 266.7 ± 326.6 ml, 9.2 ± 3.9 cm, 20.9 ± 5.7 d, 23.8% and 88.7 ± 4.9 points, respectively, in group B. Combined excellent and good rates of the Matta evaluation and Majeed score were 100% in both groups. There were no significant differences in the Matta evaluation or Majeed score between the two groups (both P > 0.05), whereas the operative time, intraoperative bleeding volume, blood transfusion volume, incision length and hospital stay were significantly less in group A (all P < 0.05). Conclusion An anterior ring internal fixator system combined with sacroiliac screw fixation can effectively treat Tile C pelvic fracture, and has advantages, including minimal invasiveness, simple operation, short operative time, safe and reliable features, fewer complications, short hospital stay and a good curative effect.

ANATOMICAL STUDY OF THE IDEAL POSITIONING OF THE S2 ILIAC SCREW

ABSTRACT Objective: To evaluate the morphometry of the pelvis to determine the safe trajectory for the insertion of the S2-iliac screw, and to correlate it with studies reported in the literature for other populations. Method: The computed tomography (CT) pelvic exams of 36 Brazilian patients without congenital malformations, tumors, pelvic ring fractures or dysplasias were selected from the database of a radiological clinic. To define the ideal trajectory of the S2-iliac screw, the following variables were measured: 1- maximum sacroiliac screw length; 2- thickness of the iliac dipole for planning the choice of screw dimensions (length and diameter); 3 - distance between the insertion point of the iliac S2 screw and the posterior sacral cortex; 4 - angulation for insertion of the screw in the mediolateral direction, representing the angle formed between the “iliac line” and the anatomical sagittal plane; 5- Angulation for insertion of the screw in the craniocaudal direction. The Pearson's chi squared and student's t tests were used for statistical analysis. Results: The sample consisted of 36 patients, 50% (18/36) of whom were women. The mean age was 63.7 years, ranging from 23 to 96 years. All the pelvic morphometric variables analyzed presented values similar to those described in the literature for other populations. Conclusion: Prior evaluation of the tomography exams was important for preoperative planning, and there was a statistically significant difference between the sexes only in relation to the variables left craniocaudal and length of the left internal table. Level of evidence III; Observational cross-sectional study.

Computed Tomographic Evaluation of the Accuracy of Minimally Invasive Sacroiliac Screw Fixation in Cats

Objectives The aim of this study was to report the use of computed tomography (CT) for postoperative evaluation of the accuracy of sacroiliac reduction and minimally invasive screw fixation in a series of five cats. Materials and Methods Medical records between January 2016 and March 2017 of cats presenting to the author's institution were reviewed. Included were cats that had undergone minimally invasive sacroiliac screw fixation with a complete medical record and pre- and postoperative radiographs. Screw size was obtained from the medical records. CT images were acquired prospectively and evaluated to assess joint reduction, relative screw size and screw positioning. Results Six sacroiliac luxations and 6 screws were available. Fixation was achieved with either a 2.4 (n = 1) or 2.7 mm (n = 5), 316L stainless steel, cortical bone screw. Mean screw size as a proportion of sacral diameter was 47.7%. Sacroiliac reduction >90% in the craniocaudal plane and sacral screw purchase >60% of the sacral width were achieved in 3/5 cases. Mean dorsoventral screw angulation was 1.6 degrees (range: −9.7 to 11.7 degrees) and craniocaudal angulation was −4.5 degrees (range: −16.6 to 6.6 degrees). Complications included screw loosening in the one case of bilateral repair and penetration of the neural canal in one case which was not detected with postoperative radiographic evaluation. Clinical Significance CT evaluation provides a useful method for the assessment of sacroiliac reduction and the accuracy of screw placement.

Applicable safety analysis and biomechanical study of iliosacral triangular osteosynthesis

Background The aim of this study was to investigate the applicable safety and biomechanical stability of iliosacral triangular osteosynthesis (ITO) through 3D modeling and finite element (FE) analysis. Methods Pelvic CT imaging data from 100 cases were imported into Mimics software for the construction of 3D pelvic models. The S2-alar-iliac (S2AI) screws and S2 sacroiliac screws were placed in the S2 segment with optimal distribution and their compatibility rate on the S2 safe channel was observed and analyzed. In the FE model, the posterior pelvic ring was fixed with two transsacral screws (TTS), triangular osteosynthesis (TO) and ITO, respectively. Four different loading methods were implemented in sequence to simulate the force in standing, flexion, right bending, and left twisting, respectively. The relative displacement and change in relative displacement of the three fixing methods were recorded and analyzed. Results The theoretical compatibility rate of S2AI screw and S2 sacroiliac screw in S2 segment was 94%, of which 100% were in males and 88% in females. In the FE model, in terms of overall relative displacement, TTS group showed the smallest relative displacement, the ITO group showed the second smallest, and the TO group the largest relative displacement. The change in relative displacement of the TTS group displayed the smaller fluctuations in motion. The change in relative displacement of the TO group under right bending and left twisting displayed larger fluctuations, while the ITO group under flexion displayed larger fluctuations. Conclusions The simultaneous placement of S2AI screw and S2 sacroiliac screw in the S2 segment is theoretically safe. Although the biomechanical stability of ITO is slightly lower than TTS, it is better than TO, and can be used as a new method for the treatment of posterior pelvic ring injuries.

Sacroiliac Separation that Can be Diagnosed After Pelvic Fixation During Surgery: A Case Report and Review of Literature

Introduction: Sacroiliac joint separation is a life-threatening serious condition in pelvic injuries. It should be diagnosed early and treated properly. Although these injuries can often be detected by imaging methods, in some cases, it is not diagnosed. Case presentation: We report a rare case of pelvic injury with sacroiliac separation during surgery, while the sacroiliac joint was completely normal on X-ray and CT and no pelvic binder was used in the patient. The sacroiliac separation noticed during the operation was fixed with a sacroiliac screw. Conclusion: Pelvic injuries, especially ligament injuries, may not be detected on both physical examination, direct radiography, and CT.