Freehand S2-Alar-Iliac Screw Placement Technique in Lumbosacral Spinal Tumors: A Preliminary Study

Abstract

Objective: S2-alar-iliac (S2AI) screw technique is widely used in spinal surgery, but it is rarely seen in the field of spinal tumors. The aim of the study is to report the preliminary outcomes of the freehand S2AI screw fixation after lumbosaral tumor resection.

Methods: The records of patients with lumbosacral tumor who underwent S2AI screw fixation between November 2016 to November 2020 at our center were reviewed retrospectively. Outcome measures included operative time, blood loss, complications, accuracy of screws, screw breach, and overall survival. Mean ± standard deviation or range was used to present continuous variables. Kaplan-Meier curve was used to present postoperative survival.

Results: A total of 23 patients were identified in this study, including 12 males and 11 females, with an average age of 47.3 ± 14.5 (range,15-73). The mean operation time was 224.6 ± 54.1 (range, 155-370 min). The average estimated blood loss was 1560.9 ± 887.0 (600-4000 ml). A total of 46 S2AI screws were implanted by freehand technique. CT scans showed three (6.5%) screws had penetrated the iliac cortex, indicating 93.5% implantation accuracy rate. No complications of iatrogenic neurovascular or visceral structure were observed. The average follow-up time was 31.6 ± 15.3 months (range, 13-60 months). Two patients' postoperative plain radiography showed lucent zone around the screw. One patient underwent reoperation for wound delayed infection. At the latest follow-up, eight patients had tumor-free survival, 11 had survival with tumor, and four died of disease.

Conclusion: The freehand S2AI screw technique is reproducible, safe, and reliable in the management of lumbosacral spinal tumors.

Keywords: S2-alar-iliac screw; freehand; lumbosacral fixation; lumbosacral spine; tumor.

Fig. 1

(A) Entry point (EP) of S2AI screw is 2 mm lateral to the midpoint between the S1 and S2 dorsal foramen. The trajectory direction was 20°–30° caudally in the sagittal plane (B) and approximately 40° horizontally in the axial plane (C), pointing to the anterior inferior iliac spine (AIIS). (D) Anteroposterior diagram of the postoperative reconstruction of lumbo‐pelvis with S2AI screws after tumor resection. (E) Lateral diagram showed the sagittal effect after lumbopelvic reconstruction

Fig. 2

Case 15. Giant cell tumor of bone at L5 in a 30‐year‐old woman. (A) Sagittal T2‐weighted magnetic resonance imaging showed the tumor involving L5 vertebral body. Coronal (B) and axial (C) T1‐weighted enhanced magnetic resonance imaging demonstrated the extent of the tumor with spinal canal compromise. (D) Axial computed tomographic scan demonstrated the tumor with osteolytic destruction. Anteroposterior (E) and lateral (F) radiographs showed a stable construct at 2 years postoperatively. (G) Postoperative computed tomographic scan demonstrated no breach of the screws

Fig. 3

Postoperative computed tomographic scan on axial slice showed an anterior breach of S2AI screw on the right side

Fig. 4

Kaplan–Meier survival curve