Neurovascular Relationships of S2AI Screw Placement: Anatomic Study

Abdul-Jabbar, Amir; Yılmaz, Emre; Iwanaga, Joe; Tawfik, Tamir; O'Lynnger, Thomas M; Schildhauer, Thomas A.; Oskouian, Rod J.; Tubbs, R. Shane

doi:10.1016/j.wneu.2018.04.095

Cited by 26 publications

(18 citation statements)

References 29 publications

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“…Patients with sagittal deformity demonstrate a cascade of compensatory mechanisms to maintain an upright posture, including increased pelvic tilt (pelvic retroversion) and decreased sacral slope [19] , [20] , [21] , [22] , [23] , [24] , [25] . Variations of sacropelvic anatomy could affect the ideal screw trajectory and an accurate trajectory is critical as the S2AI corridor traverses near several vital neurovascular structures [ 28 , 29 ]. Although the placement of these screws has been demonstrated to be safe and effective without fluoroscopic guidance and equally as safe as robotic assisted placement [ 15 , 17 ], the relationship of pelvic parameters and screw trajectory had yet to be studied.…”

Section: Discussionmentioning

confidence: 99%

“…Anatomical studies have elucidated the proximate relationship of the screw corridor and several soft tissue structures within the pelvis. These vital structures include the abdominal and pelvic viscera anteromedially, the internal iliac vessels, obturator nerve, lumbosacral trunk, and sacral plexus medially [ 28 , 29 ]. Immediately inferior of the screw corridor lies the sciatic notch which contains a plethora of structures including the superior gluteal neurovasculature just superior to the piriformis muscle, sciatic nerve, internal pudendal vessels, and pudendal nerve [33] .…”

Section: Discussionmentioning

confidence: 99%

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Pelvic parameters directly influence ideal S2 alar-iliac (S2AI) screw trajectory

Vivace

Laratta

Gum

et al. 2020

North American Spine Society Journal (NASSJ)

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Background: The utilization of the S2 Alar-Iliac (S2AI) screw provides an optimal method of spinopelvic fixation. The free-hand placement of these screws obviates the use of intra-operative fluoroscopy and relies heavily on sacropelvic anatomy; variations of this anatomy could alter the ideal screw trajectory. The S2AI corridor is near several neurovascular structures, thus an accurate trajectory is critical. The reported angles of trajectory vary within the literature and a paucity of data exists on how patient morphometry influences ideal screw trajectory. We sought to examine the relationship between ideal screw trajectory and pelvic parameters. Methods: The records of 99 consecutive patients with degenerative thoracolumbar pathology were reviewed and pelvic parameters including sacral slope, pelvic tilt, and pelvic incidence were measured with preoperative standing radiographs. Using 3-dimensional computed tomography (CT) reconstructions, an ideal S2AI trajectory was defined and anteroposterior (horizontal) and cephalocaudal (sagittal) angles were recorded. Results: Pelvic tilt was found to have a moderate inverse correlation with cephalocaudal screw trajectory (r =-0.467, p-value = 0.006). Pelvic incidence and sacral slope had weaker correlations with cephalocaudal screw angle. In subgroup analysis, patients with high pelvic tilt (> 20°) had a significantly lower cephalocaudal screw trajectory (24.9 ± 3.7°versus 29.8 ± 2.8°, p-value = < 0.001) compared to those with a normal pelvic tilt (≤ 20°). Conclusions: This study found an inverse relationship between pelvic tilt and cephalocaudal S2AI screw trajectory. Therefore, the sagittal angle of insertion becomes increasingly more perpendicular to the floor (less caudally orientated) as pelvic tilt increases in reference to a patient positioned prone on an operating table parallel to the floor. This may bolster safety and efficacy when utilizing the free-hand technique for placement of the S2AI screw as it allows the surgeon to plan a more ideal trajectory by accounting for pelvic parameters.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Pelvic parameters directly influence ideal S2 alar-iliac (S2AI) screw trajectory

Vivace

Laratta

Gum

et al. 2020

North American Spine Society Journal (NASSJ)

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“…There are four advantages for 3D-printed template in assisting sacral-iliac screw insertion compared with traditional X-ray-assisted surgery as follows: (1) improving the accuracy and security in screw insertion (2) shortening the time for surgery procedure (3) decreasing the radiation exposure for both doctor and patient (4) enhancing the communication between doctor and patient. The sacroiliac joint complex is featured with complicated anatomy and surrounded by dense vessels and nerves [2,14]. So it is dangerous to insert sacral-iliac screw percutaneous with the risk of vessel and nerve injury, which makes it a difficulty and challenge for the surgeon.…”

Section: The Advantage Of 3d-printed Template In Assisting Sacral-ilimentioning

confidence: 99%

Comparative study of sacroiliac screw placement guided by 3D-printed template technology and X-ray fluoroscopy

Zhou

Tian

Liu

et al. 2019

Arch Orthop Trauma Surg

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Objective To compare the clinical effect of 3D-printed template technology with X-ray fluoroscopy in assisting surgery for sacroiliac screws placement. Design Institutional review board-approved retrospective analysis. Patients The clinical data of 31 cases of sacroiliac complex injury between January 2015 and December 2016 were analyzed. There were 16 patients, males 11 and females 5, who underwent surgery assisted by 3D-printed template in template group, and that of contemporaneous 15 patients, males 11 and females 4, who underwent traditional surgery were gathered as fluoroscopy group. All those patients were followed up for more than 6 months. Main outcome measures The operation time and X-ray fluoroscopy times for each screw placement, and the Matta and Majeed score were analyzed and the difference between the two group was tested. Results All cases were followed up for 6-20 months, average 11.4 ± 0.6 months. In template group, 19 screws were implanted. Each screw spent 25-38 min, average 27.2 ± 5.3 min, and need 2-5 times fluoroscopy, average 2.7 ± 0.5. The fracture reduction quality was evaluated by Matta score scale: excellent 10, well 4, fair 2, good rate 87.5%; and pelvic function were evaluated by Majeed score scale: excellent 11, well 3, fair 2, and good rate 87.5%. In fluoroscopy group, 17 screws were implanted. Each screw spent 45-70 min, average 60.3 ± 5.8 min, and needs 11-23 times fluoroscopy, average 15.4 ± 3.5. The fracture reduction quality was evaluated by Matta score scale: excellent 7, well 6, fair 2, and good rate 86.7%; and pelvic function was evaluated by Majeed score scale: excellent 6, well 6, fair 3, and good rate 80.0%. The difference in operation time, X-ray fluoroscopy times between template group and fluoroscopy group had statistical significance. But the Matta and Majeed score had no difference between two groups. Conclusion Compared with traditional surgery, 3D-printed template technology-assisted surgery for sacroiliac screws placement in sacroiliac complex injury patients possesses advantage such as shortened operation time and reduced X-ray exposure times. This technology improves the safety profile of this operation and should be further studied in future clinical applications.

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“…However, the breach rate of S2AI screw placement using free-hand was 8%, even in robotic-guided S2AI screw placement, there still had a breach rate of 4.3% [ 13 , 14 ]. When a breach happens intraoperatively, neurovascular structures including the superior gluteal artery, the internal iliac vein and artery, the sciatic nerve, the obturator nerve and the lumbosacral plexus are potentially at risk for injury [ 19 ]. Hence, to avoid injury, measurement of the mandatory parameters for the ideal S2AI trajectory on CT imaging before surgery is necessary.…”

Section: Introductionmentioning

confidence: 99%

Does the thoracolumbar kyphosis secondary to ankylosing spondylitis affect the iliac trajectory of S2AI screw?

Zhong

Qian

Huang

et al. 2022

BMC Musculoskelet Disord

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Background The study aimed to evaluate the influence of thoracolumbar kyphosis secondary to ankylosing spondylitis (AS) on parameters of S2AI trajectory and to compare the ideal S2AI trajectory with those of the non-deformity patients with AS, sagittal deformity patients without AS, and the normal population reported in literatures. Methods Sagittal parameters including global kyphosis (GK), pelvic tilt (PT) and sacral slope (SS) were measured. Besides, according to the simulated ideal S2AI trajectory on the CT images, trajectory parameters were measured including Sag angle, Tsv angle, Max-length, Sacral distance and Iliac width. Starting-point parameters were also measured including PSIS distance, Skin distance, Iliac wing and S2 midline. Results Ninety-four AS-related thoracolumbar kyphosis patients were included. After adjusting the age and gender, twenty non-deformity patients with AS and 20 sagittal deformity patients without AS were selected to compare with patients with AS-related thoracolumbar kyphosis, respectively. Sag angle in deformity patients with AS was smaller than other two groups (P < 0.001). No difference was found in Tsv angle and Sacral distance between AS patients with and without deformity. However, these two parameters were shown significant differences between deformity patients with AS and without AS. In deformity patients with AS, no significant differences were found in all parameters between genders Furthermore, there were strong correlations between PT and the bilateral Sag angle (P < 0.001). Conclusions The thoracolumbar kyphosis secondary to AS affects the Sag angle of the ideal S2AI trajectory which was approximately 20° smaller than that in non-deformity patients with AS, sagittal deformity patients without AS, and the normal population. Additionally, the Tsv angle and the Sacral distance in AS patients with thoracolumbar kyphosis were about 10° and 10 mm larger than those in sagittal deformity patients without AS, and the normal population reported in literatures.

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Neurovascular Relationships of S2AI Screw Placement: Anatomic Study

Cited by 26 publications

References 29 publications

Pelvic parameters directly influence ideal S2 alar-iliac (S2AI) screw trajectory

Pelvic parameters directly influence ideal S2 alar-iliac (S2AI) screw trajectory

Comparative study of sacroiliac screw placement guided by 3D-printed template technology and X-ray fluoroscopy

Does the thoracolumbar kyphosis secondary to ankylosing spondylitis affect the iliac trajectory of S2AI screw?

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