Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Analysis of insertion torque of pedicle screw using penetrating endplate screw technique for L5-S1 interbody fusion. (#71)

Masaru Hatano 1 2 , Keishi Maruo 1 2 , Fumihiro Arizumi 2 , Masakazu Toi 2 , Tomoyuki Kusukawa 2 , Hayato Oishi 2 , Tetsuto Yamaura 2 , Kazuma Nagao 2 , Shoji Nishio 1 , Yoshiteru Nakamura 1 , Toshiya Tachibana 2
  1. Orthopaedic Surgery, Daiwa cyuo hospital, Osaka, Japan
  2. Hyogo Medical University, Nishinomiya, Hyogo, Japan

Introduction

The sacral pedicle screw (S1 PS) is weak due to the anatomical characteristics of the sacral vertebrae. Therefore, it is recommended to use bicortical or tricortical techniques. However, the S1 percutaneous pedicle screw (PPS) fixation technique remains challenging because there is a risk of vascular injury associated with the use of the guidewire. Recently, we employed the modified penetrating endplate screw (mPES) technique, a percutaneous approach utilizing a curved hollow probe. The mPES technique, through penetrating the sacral endplate, has the potential to enhance fixation strength. The objective of this investigation was to analyze the insertion torque using the mPES technique. 

Methods

A total of 20 consecutive patients who underwent posterior or transforaminal lumbar interbody fusion at L5-S1 with S1 PPS insertion using the mPES technique were included. L5 PPS were inserted by traditional trajectory. The mPES technique is a variation of PPS procedure, involving the penetration of the sacral endplate targeting its anterior 1/3 and medial angle of 20 degree. Age, BMI, bone mineral density (BMD), screw size, Hounsfield unit (HU) values at L5 and S1 vertebral body, and insertion torque values were investigated. The torque during screw insertion was measured using torque meter (DTK-CN, Nakamura Co.). The maximum insertion torque recorded during the final phase was considered for analysis. In the mPES group, the insertion torque at S1 and L5 were compared. Additionally, 32 patients who underwent spinal corrective fusion surgery for adult spinal deformity and had the S1 PS insertion using the traditional trajectory (traditional group) were juxtaposed with 9 patients following a propensity score matching process based on age, sex, BMI, and BMD. The insertion torque at S1 were compared between the mPES group and the traditional group.

Results

This study enrolled 20 patients, including 14 males and 6 females, with a mean age of 68.0 years. In the mPES group, the HU values were significantly higher in S1 than L5 (164.3±53.9 vs 140.7±47.0 at L5, p<0.001). The PS insertion torque were significantly higher at S1 than L5 (394.0±104.8 Ncm vs 308.8±77.7 Ncm, p=0.001).In a comparative analysis using propensity score matching between the mPES and traditional group, no significant differences were discerned in age, sex, BMI, BMD, or HU values. However, the mPES technique demonstrated significantly higher insertion torque than the traditional group (388.5 ± 111.3 Ncm vs 165.4 ± 77.2 Ncm, p<0.001).

Discussion

The mPES technique provided 2.3 times higher insertion torque than the traditional technique in S1 PS. The mPES technique is a safe method that reduces the risk of vascular injury through the insertion of the guidewire into the disc via inward trajectory. In addition, the mPES technique demonstrated favorable initial fixation in lumbosacral fusion in this study and could emerge as a prominent procedure for preventing postoperative pedicle screw loosening and non-union.

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