Lumbar segment-dependent soft tissue artifacts of skin markers during in vivo weight-bearing forward-Backward bending

Xin Xi; Zhi Ling; Cong Wang; Chunya Gu; Xuqiang Zhan; Haixin Yu; Siqi Lu; Tsung-Yuan Tsai; Yan Yu; Liming Cheng

doi:10.3389/fbioe.2022.960063

Lumbar segment-dependent soft tissue artifacts of skin markers during in vivo weight-bearing forward-Backward bending

Front Bioeng Biotechnol. 2022 Aug 17:10:960063. doi: 10.3389/fbioe.2022.960063. eCollection 2022.

Authors

Xin Xi^{1

2}, Zhi Ling³, Cong Wang³, Chunya Gu⁴, Xuqiang Zhan^{1

2}, Haixin Yu⁵, Siqi Lu^{1

2}, Tsung-Yuan Tsai^{3

6}, Yan Yu^{1

2}, Liming Cheng^{1

2}

Affiliations

¹ Department of Spine Surgery, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China.
² Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration, Ministry of Education, Department of Spine Surgery, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China.
³ School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
⁴ Department of Spinal Rehabilitation, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China.
⁵ Department of Orthopedic Surgery, Yangpu Hospital, School of Medicine, Tongji University, Shanghai, China.
⁶ TAOiMAGE Medical Technologies Corporation, Shanghai, China.

Abstract

Traditional optical motion capture (OMC) with retroreflective markers is commonly used to measure joint kinematics but was also reported with unavoidable soft tissue artifacts (STAs) when quantifying the motion of the spine. Additionally, the patterns of the STA on the lumbar spine remain unclear. This study aimed to 1) quantify the in vivo STAs of the human lower back in three-dimensional directions during weight-bearing forward-backward bending and 2) determine the effects of the STAs on the calculated flexion angles between the upper and lower lumbar spines and adjacent vertebrae by comparing the skin marker (SM)- and virtual bone marker (VM)-based measurements. Six healthy volunteers were imaged using a biplanar radiographic system, and thirteen skin markers were mounted on every volunteer's lower back while performing weight-bearing forward-backward bending. The STAs in the anterior/posterior (AP), medial/lateral (ML), and proximal/distal (PD) directions were investigated. The flexion angles between the upper and lower lumbar segments and adjacent intervertebral segments (L2-L5) throughout the cycle were calculated. For all the participants, STAs continuously increased in the AP direction and exhibited a reciprocal trend in the PD direction. During flexion, the STA at the lower lumbar region (L4-L5: 13.5 ± 6.5 mm) was significantly higher than that at the upper lumbar (L1-L3: 4.0 ± 1.5 mm) in the PD direction (p < 0.01). During extension, the lower lumbar (L4-L5: 2.7 ± 0.7 mm) exhibited significantly less STAs than that exhibited by the upper lumbar region (L1-L3: 6.1 ± 3.3 mm) (p < 0.05). The STA at the spinous process was significantly lower than that on both sides in the AP direction (p < 0.05). The present results on STAs, based on dual fluoroscopic measurements in healthy adult subjects, presented an anatomical direction, marker location, and anatomic segment dependency, which might help describe and quantify STAs for the lumbar spine kinematics and thus help develop location- and direction-specific weighting factors for use in global optimization algorithms aimed at minimizing the effects of STAs on the calculation of lumbar joint kinematics in the future.

Keywords: dual fluoroscopy; forward–backward bending; in vivo kinematics; lumbar spine; soft tissue artifacts.