Anatomical parameters alter the biomechanical responses of adjacent segments following lumbar fusion surgery: Personalized poroelastic finite element modelling investigations

March 3, 2023

. 2023 Feb 13;11:1110752.

doi: 10.3389/fbioe.2023.1110752.

eCollection 2023.

Affiliations

¹ School of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
² Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan.
³ Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
⁴ Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
⁵ Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
⁶ Division of Emergency and Critical Care Radiology, Chang Gung Memorial Hospital, Linkou, Taiwan.
⁷ Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Linkou, Taiwan.

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Mohammad Nikkhoo et al.

Front Bioeng Biotechnol.

2023.

. 2023 Feb 13;11:1110752.

doi: 10.3389/fbioe.2023.1110752.

eCollection 2023.

Affiliations

¹ School of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
² Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan.
³ Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
⁴ Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
⁵ Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
⁶ Division of Emergency and Critical Care Radiology, Chang Gung Memorial Hospital, Linkou, Taiwan.
⁷ Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Linkou, Taiwan.

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Abstract

Introduction: While the short-term post-operative outcome of lumbar fusion is satisfying for most patients, adjacent segment disease (ASD) can be prevalent in long-term clinical observations. It might be valuable to investigate if inherent geometrical differences among patients can significantly alter the biomechanics of adjacent levels post-surgery. This study aimed to utilize a validated geometrically personalized poroelastic finite element (FE) modeling technique to evaluate the alteration of biomechanical response in adjacent segments post-fusion. Methods: Thirty patients were categorized for evaluation in this study into two distinct groups [i.e., 1) non-ASD and 2) ASD patients] based on other long-term clinical follow-up investigations. To evaluate the time-dependent responses of the models subjected to cyclic loading, a daily cyclic loading scenario was applied to the FE models. Different rotational movements in different planes were superimposed using a 10 Nm moment after daily loading to compare the rotational motions with those at the beginning of cyclic loading. The biomechanical responses of the lumbosacral FE spine models in both groups were analyzed and compared before and after daily loading. Results: The achieved comparative errors between the FE results and clinical images were on average below 20% and 25% for pre-op and post-op models, respectively, which confirms the applicability of this predictive algorithm for rough pre-planning estimations. The results showed that the disc height loss and fluid loss were increased for the adjacent discs in post-op models after 16 h of cyclic loading. In addition, significant differences in disc height loss and fluid loss were observed between the patients who were in the non-ASD and ASD groups. Similarly, the increased stress and fiber strain in the annulus fibrosus (AF) was higher in the adjacent level of post-op models. However, the calculated stress and fiber strain values were significantly higher for patients with ASD. Discussion: Evaluating the biomechanical response of pre-op and post-op modeling in the non-ASD and ASD groups showed that the inherent geometric differences among patients cause significant variations in the estimated mechanical response. In conclusion, the results of the current study highlighted the effect of geometrical parameters (which may refer to the anatomical conditions or the induced modifications regarding surgical techniques) on time-dependent responses of lumbar spine biomechanics.

Keywords:

adjacent segment disease; finite element analysis; personalized modeling; posterior lumbar fusion; spine biomechanics.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

**FIGURE 1**

Methodology of personalized pre-operative finite element (FE) modeling of the lumbosacral spine form from lateral and anterior posterior (AP) X-ray radiographs. **(A)** Parameters extraction, **(B)** Development of the vertebrae, **(C)** Development of the FE model.

**FIGURE 2**

Loading scenario of the daily cyclic loading (Flexion, extension, lateral bending, and axial rotation moments of 10 N m were applied at points 1 and 2).

**FIGURE 3**

A schematic sample of comparison between the finite element results and the functional X-ray images in the neutral position, flexion, and extension for **(A)** pre-operative and **(B)** post-operative models.

**FIGURE 4**

Intersegmental motion patterns for non-ASD and ASD group FE models in the **(A)** upper and **(B)** lower adjacent level for different directions.

**FIGURE 5**

Calculated intradiscal pressure for non-ASD and ASD group FE models in the **(A)** upper and **(B)** lower adjacent level for different directions.

**FIGURE 6**

Calculated facet joint forces for non-ASD and ASD group FE models in the **(A)** upper and **(B)** lower adjacent level for different directions.

**FIGURE 7**

Disc height loss and fluid loss for post-operative non-ASD and ASD group FE models for the **(A)** upper and **(B)** lower adjacent levels.

**FIGURE 8**

Increased axial stress in AF matrix for post-operative non-ASD and ASD group FE models for the **(A)** upper and **(B)** lower adjacent levels.

**FIGURE 9**

Increased collagen fiber strain in AF matrix for post-operative non-ASD and ASD group FE models for the **(A)** upper and **(B)** lower adjacent levels.

References

1. Argoubi M., Shirazi-Adl A. (1996). Poroelastic creep response analysis of a lumbar motion segment in compression. J. Biomechanics 29 (10), 1331–1339. 10.1016/0021-9290(96)00035-8
  
  –
  
  DOI
  
  –
  
  PubMed
1. Beckmann A., Nicolini L. F., Grevenstein D., Backes H., Oikonomidis S., Sobottke R., et al. (2020). Biomechanical in vitro test of a novel dynamic spinal stabilization system incorporating polycarbonate urethane material under physiological conditions. J. Biomechanical Eng. 142 (1), 011005. 10.1115/1.4044242
  
  –
  
  DOI
  
  –
  
  PubMed
1. Chiang M. F., Zhong Z. C., Chen C. S., Cheng C. K., Shih S. L. (2006). Biomechanical comparison of instrumented posterior lumbar interbody fusion with one or two cages by finite element analysis. Spine (Phila Pa 1976) 31 (19), E682–E689. 10.1097/01.brs.0000232714.72699.8e
  
  –
  
  DOI
  
  –
  
  PubMed
1. Dreischarf M., Rohlmann A., Bergmann G., Zander T. (2012). Optimised in vitro applicable loads for the simulation of lateral bending in the lumbar spine. Med. Eng. Phys. 34 (6), 777–780. 10.1016/j.medengphy.2012.04.002
  
  –
  
  DOI
  
  –
  
  PubMed
1. Dreischarf M., Rohlmann A., Bergmann G., Zander T. (2011). Optimised loads for the simulation of axial rotation in the lumbar spine. J. Biomech. 44 (12), 2323–2327. 10.1016/j.jbiomech.2011.05.040
  
  –
  
  DOI
  
  –
  
  PubMed

Grant support

The authors acknowledge the funding supported by the National Science and Technology Council of Taiwan (111-2221-E-182-009-MY3), the Chang Gung Memorial Hospital Research Program (CMRPD1L0181, CMRPD1L0182, CMRPG3M0481), and the Healthy Aging Research Center, Chang Gung University, Taoyuan, Taiwan (EMRPD1M0411).