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.

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.

Does Laterality Matter? The Effect of Unilateral v. Bilateral Sacroiliac Screw Fixation on Personal Hygiene

Study Design: Retrospective comparative analysis of prospective cohort. Objective: To determine whether sacroiliac (SI) screw fixation ipsilateral to hand dominance compared to bilateral fixation impacts personal hygiene (wiping) after toileting. Methods: Inclusion criteria were adult spinal deformity (ASD) patients with long arthrodesis (≥T12-pelvis) who had undergone primary unilateral or bilateral SI fixation with a minimum of 2-years-follow-up. Results: 117 consecutive patients were included and separated into 2 groups: bilateral SI fixation (BL, n = 61) and unilateral SI fixation (UNI, n = 56), with no difference in age. Of UNI patients, 10.7% (6) performed personal hygiene with a different hand after surgery, compared to 6.6% (4) of patients who received BL fixation ( P = 0.422). All UNI patients who switched hands were right-hand dominant, and 5/6 received right-sided fixation. There was no statistical difference found between number of levels fused (<8, 9-11, or >11 levels) and changes in personal hygiene habits. Over a third of patients from both groups had difficulty performing personal hygiene after fusion (UNI = 39.3% BL = 36.1%, P = 0.719). Conclusion: SI screws increase the difficulty of performing personal hygiene; yet, the side of unilateral screws does not significantly change personal hygiene habits when compared to bilateral screw placement. Moreover, the length of the construct does not have a significant impact on ability to perform personal hygiene, cause changes in habits, or require the assistance of another individual. However, among our sample of individuals, bilateral fixation did result in a higher rate of revision instrumentation.

Feasibility study of transfacet sacroiliac screw fixation based on Mimics

Background Sacroiliac screw (SIS) has become an effective internal fixation method for sacral fracture and sacroiliac joint dislocation. However, classic placement of SIS has some defects such as possibility of nerve injury with a learning curve and contraindications. An alternative to the classic placement of SIS is expected Objective To explore the feasibility of transfacet sacroiliac screw (TFSIS), so as to provide an alternative to the classic placement of SIS. Methods CT scan data of pelvis in 60 healthy adults including 30 males and 30 females with an average age of 45 years (range 20-70 years), were transferred into a PC. The anatomical parameters of screw channel of TFSIS were measured by simulating the placement of TFSIS by Mimics 16.0 software on the PC. Secondly, according to the anatomical parameters of each pelvis, 5.0 mm and 6.0 mm screws were used respectively to simulate the placement of TFSIS in 30 pelvises to observe the effect of placement. Results The length of screw channel was (10.84 ± 0.93) cm, the distance between the insertion point and the center of the superior facet of S1 was (1.14 ± 0.93) mm, the distance between the exit point and the upper -posterior border of acetabulum was (5.73 ± 2.57) mm, the anteversion angle between the central axis of the screw channel and the line parallel to the upper endplate of S1 was (53.96±3.94) °, the outward angle between the central axial of the screw channel and the longitudinal axis of the trunk was (47.4 7± 5.13)°, the safety angle in sagittal plane was (13.91 ± 2.92) °, the safety angle in coronal plane was (8.57 ± 1.63) °, the height was (11.91 ± 1.47) mm, and the width was (7.75 ± 0.89) mm. Within the channel for 5.0mm and 6.0mm screws accounted for 100%. Conclusions Placement of TFSIS with a diameter of 5.0-6.0 mm and a length of 90 mm is safe and feasible, which may be used as an alternative to the classic placement of SIS.

Feasibility Study of Transfacet Sacroiliac Screw Fixation Based on Mimics

Background: Sacroiliac screw (SIS) has become an effective internal fixation method for sacral fracture and sacroiliac joint dislocation. However, classic placement of SIS has some defects such as possibility of nerve injury with a learning curve and contraindications. An alternative to the classic placement of SIS is expected.Objective: To explore the feasibility of transfacet sacroiliac screw (TFSIS), so as to provide an alternative to the classic placement of SIS.Methods：CT scan data of pelvis in 60 healthy adults including 30 males and 30 females with an average age of 45 years (range 20-70 years), were transferred into a PC. The anatomical parameters of screw channel of TFSIS were measured by simulating the placement of TFSIS by Mimics 16.0 software on the PC. Secondly, according to the anatomical parameters of each pelvis, 5.0 mm and 6.0 mm screws were used respectively to simulate the placement of TFSIS in 30 pelvises to observe the effect of placement.Results： The length of screw channel was (10.84 ± 0.93) cm, the distance between the insertion point and the center of the superior facet of S1 was (1.14 ± 0.93) mm, the distance between the exit point and the upper -posterior border of acetabulum was (5.73 ± 2.57) mm, the anteversion angle between the central axis of the screw channel and the line parallel to the upper endplate of S1 was (53.96±3.94) °, the outward angle between the central axial of the screw channel and the longitudinal axis of the trunk was (47.4 7± 5.13)°, the safety angle in sagittal plane was (13.91 ± 2.92) °, the safety angle in coronal plane was (8.57 ± 1.63) °, the height was (11.91 ± 1.47) mm, and the width was (7.75 ± 0.89) mm. Within the channel for 5.0mm and 6.0mm screws accounted for 100%. Conclusions： Placement of TFSIS with a diameter of 5.0-6.0 mm and a length of 90 mm is safe and feasible, which may be used as an alternative to the classic placement of SIS.