Liu Chang-zheng1, Ma Xue-hai2, Zheng Jin2, Zheng Sheng-nai3, Yao Qing-qiang3, Tang Cheng3, Huang Hao3, Xu Yan3

1Department of Orthopaedics, Suzhou Municipal Hospital, Suzhou  234000, Anhui Province, China; 2Department of Orthopaedics, Chuzhou Hospital, Huaian  223200, Jiangsu Province, China; 3Department of Orthopaedics, Nanjing First Hospital, Nanjing Medical University, Nanjing  210006, Jiangsu Province, China

Liu Chang-zheng, Associate chief physician, Department of Orthopaedics, Suzhou Municipal Hospital, Suzhou  234000, Anhui Province, China

Ma Xue-hai, Associate chief physician, Department of Orthopaedics, Chuzhou Hospital, Huaian  223200, Jiangsu Province, China

Liu Chang-zheng and Ma Xue-hai contributed equally to this paper.

Correspondence to: Zheng Sheng-nai, Doctor, Associate chief physician, Department of Orthopaedics, Nanjing First Hospital, Nanjing Medical University, Nanjing  210006, Jiangsu Province, China

Abstract
BACKGROUND: Spinous process and interspinous internal fixation can share the pressure between the disc and zygapophyseal joints and retain physical activity, but the specific biomechanical mechanism need further research.
OBJECTIVE: To measure load sharing and stress distribution of zygapophyseal joints with different distractions.
METHODS: Six cadaver intact lumbar specimens (L2–5) were loaded in flexion, neutral, and extension using ZWICK-Z010/BIXI electronic universal testing machine to exert 700 N?m. Pressure measuring films measured the zygapophyseal joints load during each of the three positions. Inter-spinous process stabilization device (IPD) with different spacer heights (10, 12, 14, 16, 18,
20 mm) was placed.
RESULTS AND CONCLUSION: The IPD with 10 mm spacer height could not share the zygapophyseal joints load significantly. The 12 mm implant could share zygapophyseal joints load only in extension. The 14 mm implant could significant decrease the zygapophyseal joints load. The 16 mm and 20 mm implants could basically eliminate the zygapophyseal joints load. Spacer height of IPD is equal to or slightly greater than the neutral position of interspinous height can share the load of zygapophyseal joints reasonable.

Liu CZ, Ma XH, Zheng J, Zheng SN, Yao QQ, Tang C, Huang H, Xu Y. In vitro effects of a new shape-memory alloy interspinous process device on zygapophyseal joints pressures distribution.Zhongguo Zuzhi Gongcheng Yanjiu yu Linchuang Kangfu. 2011;15(48): 8989-8992.     [http://www.crter.cn  http://en.zglckf.com]

Tables and figures

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