Finite Element Analysis of 3 Posterior Fixation Techniques in the Lumbar Spine

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FEATURE ARTICLE 

Finite Element Analysis of 3 Posterior Fixation Techniques in the Lumbar Spine

Zhiqiang Gong, MM; Zixian Chen, MD; Zhenzhou Feng, MD; Yuanwu Cao, MM; Chun Jiang, MD; Xiaoxing Jiang, MD

• Orthopedics
• May 2014 - Volume 37 · Issue 5: e441-e448
• DOI: 10.3928/01477447-20140430-54

Abstract

This study compared the biomechanics of 3 fixation techniques: bilateral pedicle screw (BPS) fixation, unilateral pedicle screw (UPS) fixation, and UPS supplemented with translaminar facet screw (UPS+TLFS) fixation. The study was conducted in an L3–L5 finite element model. Three different finite element models were created by adopting different fixation techniques after removal of the left L3–L4 and L4–L5 facet joints. A 500-N compressive preload combined with 8-NM moment were applied in 3 finite element models with 3 fixation techniques during different movements. Angular displacement and stress distribution were recorded. As described in this article, the UPS model had the most variation in angular displacement, the BPS model was intermediate, and the UPS+TLFS model had the least mobility. Most of the stress accumulated on the body and tail of the pedicle screws and the connecting rods in the UPS and BPS models, but stress accumulated on the rods and the part of the facet joint pierced by the TLFS in the UPS+TLFS model. The middle part of the pedicle screw endured little stress compared with the upper and lower parts. The maximum stress on the fixation devices was highest in the UPS model. The maximum stress in the UPS+TLFS model was the lowest among the 3 models. Biomechanically, UPS+TLFS fixation is superior to either UPS fixation or BPS fixation in improving stability and reducing stress. Bilateral pedicle screw fixation is intermediate, and UPS fixation is inferior.

The authors are from the Department of Orthopedic Surgery, Zhongshan Hospital affiliated with Fudan University, Shanghai, China.

Drs Gong and Chen contributed equally to this work and should be considered as equal first authors.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Xiaoxing Jiang, MD, Department of Orthopedic Surgery, Zhongshan Hospital affiliated with Fudan University, 180 Fenglin Rd, Xuhui District, Shanghai 200032, China ( chenzixianspine@163.com).

Received: September 17, 2013

Accepted: November 08, 2013