{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,2]],"date-time":"2025-10-02T11:10:27Z","timestamp":1759403427238,"version":"build-2065373602"},"reference-count":36,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,10,2]],"date-time":"2025-10-02T00:00:00Z","timestamp":1759363200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Bioeng. Biotechnol."],"abstract":"<jats:sec><jats:title>Objective<\/jats:title><jats:p>While lumbar spondylolysis has been biomechanically associated with subsequent spondylolisthesis and disc degeneration, its implications on cranial adjacent segments remain unclear. This <jats:italic>in vitro<\/jats:italic> experiment aims to quantify the segmental alterations in kinematics and contact mechanics at both L5\/S1 and L4\/L5 levels induced by L5 pars defects.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>Six fresh-frozen human lumbar cadaveric specimens (L1-S2) underwent pure moment loading (4 Nm) in flexion-extension, lateral bending, and axial rotation. Sequential testing compared intact specimens with simulated L5 bilateral spondylolysis models. Intervertebral kinematics were quantified using optical motion tracking, while L4\/L5 disc contact parameters were measured using Tekscan pressure sensors.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>L5\/S1 segmental mobility increased in lateral bending (1.66\u00b0, p = 0.002) and axial rotation (1.45\u00b0, p = 0.007) in spondylolysis models. Motion increases were observed at the cranial adjacent L4\/L5 segment: flexion-extension (1.89\u00b0, p &amp;lt; 0.001), lateral bending (2.15\u00b0, p = 0.002), and axial rotation (1.89\u00b0, p = 0.022). However, no significant differences were detected in the L4\/L5 disc contact parameters for peak contact pressure, contact area, and contact force.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>Isthmic defects induce segmental hypermobility at the cranial adjacent segment. This kinematic alteration may accelerate disc degeneration.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fbioe.2025.1653918","type":"journal-article","created":{"date-parts":[[2025,10,2]],"date-time":"2025-10-02T10:41:47Z","timestamp":1759401707000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["L5 spondylolysis increases segmental mobility at the cranial adjacent level without altering intervertebral disc contact pressure"],"prefix":"10.3389","volume":"13","author":[{"given":"Zhilin","family":"Ge","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bingde","family":"Zhao","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xu","family":"Xu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lin","family":"Chen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dongzhu","family":"Liang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qingyang","family":"Kang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zibo","family":"Gao","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Junhua","family":"Luo","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jiheng","family":"Zhan","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jianquan","family":"Chen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bo","family":"Zhang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2025,10,2]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"6739","DOI":"10.1038\/s41598-020-63784-0","article-title":"Prevalence of lumbar spondylolysis and spondylolisthesis in patients with degenerative spinal disease","volume":"10","author":"Aoki","year":"2020","journal-title":"Sci. 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