A computed tomographic anatomical study of the upper sacrum. Application for a user guide of pelvic fixation with iliosacral screws in adult spinal deformity

Comparative Morphometry of the Sacrum and Its Clinical Implications: A Retrospective Study of Osteometry in Dry Bones and CT Scan Images in Patients Presenting With Lumbosacral Pathologies

Background

Morphometric measurement of the sacrum is crucial due to its active involvement in the instrumentation for lumbar pathologies. From screw placement to stabilization procedures for the spine, the sacrum remains a site of surgical importance. Thus, the purpose of this study was to generate baseline data by comparing two techniques, namely, osteometry in dry bones and CT scan imaging.

Methodology

In this study, 30 dry, fully ossified, disarticulated sacra were studied for osteometry, and 60 CT scan reports of patients with lumbar pathologies were retrospectively evaluated. In both cases, similar parameters were measured. The mean values were determined, the two methods were compared, and statistical analysis was performed.

Results

Among the 30 dry bone samples, 33.3% (10 out of 30) were males, while 55% of the CT scan group were males. Correlation between the different measurements in the CT scan group suggested that the vertebral body maximum width of S1 had a significant positive correlation with the vertebral body height of S1, sacral height, sacral breadth, transverse diameter of auricular surface, and vertical diameter of auricular surface. Statistically significant higher values (P < 0.001) were observed for the vertebral body mid diameter of S1, vertebral body height of S1, pedicle width, and pedicle depth measurements in the dry bone group compared to the CT scan group.

Conclusions

The efficiency of anaesthetic blocks can be increased if the parameters are evaluated beforehand. Moreover, sexual dimorphism of the bone can account for the varied results of the parameters, indicating the necessity to conduct gender-based studies in a wider population.

Optimal ilio-sacral screw trajectory in paediatric patients : a computed tomography study

Pelvic fixation during procedures performed to treat spinal deformities in paediatric patients remains challenging. No computed tomography studies in paediatric have assessed the optimal trajectory of ilio- sacral screws to prevent screw malposition. We used pelvic computed tomography from 80 children divided into four groups : females <10 and ≥10 years and males <10 and ≥10 years. A secure triangular corridor parallel to the upper S1 endplate was delineated based on three fixed landmarks. The optimal screw insertion angle was subtended by the horizontal and the line bisecting the secure corridor. Student’s t test was applied to determine whether the optimal screw insertion angle and/or anatomical parameters were associated with age and/or sex. Mean optimal angle was 32.3°±3.6°, 33.8°±4.7°, 30.2°±5.0°, and 30.4°±4.7° in the younger females, younger males, older females, and older males, respectively. The mean optimal angle differed between the two age groups (p=0.004) but not between females and males (p=0.55). Optimal mean screw length was 73.4±9.9 mm. Anatomical spinal canal parameters in the transverse plane varied with age (p=0.02) and with sex in the older children (p=0.008), and those in the sagittal plane varied with sex (p=0.04). Age affected ilio-sacral screw positioning, whereas sex did not. Several anatomical spinal canal parameters varied with age and sex. These results should help to ensure safe and easy ilio-sacral screw placement within a secure corridor.

Ilio-sacral screw pelvic fixation when correcting spinal deformities with or without pelvic obliquity: our experience over 40 years

Ilio-sacral screw fixation for treatment of spinal deformities with pelvic obliquity was used from more than 40 years in our department of pediatric orthopedics. Despite trying all the other systems published in the literature, the authors came back to iliosacral screw to address the pelvic fixation. Keeping the same anatomical and biomechanical principles, with no damage of the SI joint, they improve the technology over time, to allow an easy use. The fear about the precise insertion necessary to prevent any root irritation is now greatly reduced thanks to the modern navigation. The history of the establishment and the advantages of this technique are explained based on more than 250 cumulative cases with an excellent correction of the pelvic obliquity, without any case of complete pull out of the ilio-sacral screw. A very low rate of nonunion thanks to the 3D adaptation of the balance in erect standing or sitting posture of the patient, thanks to the motion of the intact SI joint, and the small sagittal motion existing in the linkage screw/connector. All this comparing favorably to the other techniques published in the current literature.

Anatomical considerations of safe drilling corridor upper sacral segment screw insertion

The upper segment of sacrum is an important for screw insertions of unstable lumbosacral spine. Measurements of the S1-S2 as sacral wings, pedicles, sacral foraminas and sacral canal were taken from 87 sacrums. The mean depths of S1 pedicle and sacral wing were estimated as 25.8 ± 2.3 mm and 50.1 ± 1.7 mm, respectively. Angles screw trajectory of sacral pedicle anteromedial and sacral wing were measured as 29.6 ± 0.9° and 29.7 ± 2.1°, respectively. To avoid injury to the vascular structures anteriorly and nerve roots medially, depth and angle of screw trajectory is important for the entrance off pedicular screw placement to the S1.

Correction of adult spinal deformity with a minimally invasive fusionless bipolar construct: Preliminary results

INTRODUCTION

Fusion in adult spinal deformity has a high rate of complications. Fusionless constructs in children and percutaneous fixation in adults are now being used routinely. The aim of this study was to evaluate the preliminary results of a minimally invasive fusionless surgical technique used to correct adult spinal deformity.

MATERIALS AND METHODS

Thirty-eight patients with an average age of 45 years (15-76) with major spinal deformity requiring extensive arthrodesis from the upper thoracic region to the pelvis were operated consecutively and followed prospectively. Two hooks were implanted at the top and two iliosacral screws at the bottom. Two large rods connected by dominos to two small rods joined the upper hooks to the lower screws. The surgical data (operative time and bleeding), the radiological findings (Cobb angle, sagittal parameters, C7-plumbline AP and lateral), the complication rate and the morbidity were evaluated at the last follow-up visit.

RESULTS

The primary curvature was reduced by 40% from a mean of 58.5° (26-146) to 35.2° (3-109) (p<0.001). A clear decrease in operating time (270min) and blood loss (50cc/level) were observed. The length of hospitalization averaged 18 days (6-66), including an 8-15 day long preoperative traction period for 11 patients. We found 7 infectious complications, 11 early mechanical complications and one case of paraplegia due to severe kyphoscoliosis.

CONCLUSION

The corrections obtained are comparable to those reported in the literature for standard constructs. Most patients had an uneventful postoperative course. The early complications observed led us to very carefully select the indications. Long-term follow-up is essential.

Comparison between posterior sacral plate stabilization versus minimally invasive transiliac-transsacral lag-screw fixation in fractures of sacrum: a single-centre experience

PURPOSE

The sacrum is a mechanical nucleus working as the base for the spinal column, as well as the keystone of the pelvic ring. Thus, injuries of the sacrum can lead to biomechanical instability and nerve conduction abnormality.

METHODS

The common classification is the Denis classification, but these fractures are often part of a lesion of the posterior pelvic ring and therefore the Tile classification is very useful. The goals of operative intervention are to reduce fracture fragments, protect neurological structures, and provide adequate stability for early mobilization.

RESULTS

The stabilization of these injuries can be difficult even in a patient with adequate bone stock and concomitant medical comorbidities. The posterior-ring tension-band metallic plate and sacroiliac joint screw are two commonly used methods for posterior internal fixation of the pelvis.

CONCLUSIONS

In this study, we evaluate the differences, in the treatment of sacral fractures, between the two techniques, revising the literature and our experience.

Computational analysis on the feasibility of transverse iliosacral screw fixation for different sacral segments

PURPOSE

To evaluate the feasibility of transverse iliosacral (TIS) screw placement in different segments of the sacrum and measure the parameters of the unilateral iliosacral (IS) screw in the case that cannot be inserted the TIS screw.

METHODS

This study used 100 pelvic continuous computed tomography images. Mimics (Materialise Interactive Medical Image Control System) was used to reconstruct the three-dimensional pelvis model. All sacrums were divided into the normal group and dysmorphic group. Any difference in osseous fixation pathway (OFP) diameter in the first two segments between both groups was investigated. In dysmorphic sacrums, the optimal inserting angle and length of the unilateral S1 screw were measured. The number of foramen in every sacrum was recorded.

RESULTS

Thirty-two sacrums had sacral dysmorphism. The OFP diameter for the S2 TIS screw in the dysmorphic group was larger than that in the normal group (p = 0.02). Receiver operating characteristic curve analysis indicated the cutoff values as 20.55 mm and 15.18° for the S1 front edge height and S1S2 angle, respectively. In the dysmorphic case, the unilateral S1 IS screw should be inserted with a cephalad incline angle of 36.14 ± 5.97° and a ventrally incline angle of 37.33 ± 4.64°. S3 TIS screw placement rate was 53.1% in the dysmorphic group.

CONCLUSIONS

The most common cause of sacral dysmorphism is the fusion of the L5 to the true S1. In dysmorphic sacrums, the unilateral IS screw should be placed obliquely in the S1 segment, and the S2 segment usually has a sufficient OFP for the TIS screw. Using S3 TIS screw and two TIS screws in the first segment technique is not recommended because of a high risk.