Intraoperative measurement of hinge reaction force using strain gauge and predictability of postoperative hinge fracture in open-door cervical laminoplasty: a prospective study with mid-term follow-up.

Authors

Shigeo Ueda, Nobuaki Naito, Hokuto Yamashita, Jiro Ohara, Atsuhiko Toyoshima, Miyuki Fukuda, Nobuhiro Sasaki, Masayuki Kuroda, Minoru Hoshimaru

Published in

Journal of spine surgery (Hong Kong). Volume 12. Issue 6. Pages 93. Jun 30, 2026. Epub Jun 25, 2026.

Abstract

Open-door cervical laminoplasty relies on greenstick fracture at the hinge side to maintain laminar elevation. The hinge reaction force secures hydroxyapatite (HA) spacers without additional fixation, but has never been quantitatively measured. This study aimed to quantify hinge reaction force using a strain gauge system, to identify factors correlated with it, to evaluate its predictive value for early postoperative hinge fracture, and to investigate mid-term bone healing of fractured hinges.
This prospective study included 50 patients (173 laminae) who underwent open-door laminoplasty with stand-alone HA spacers [2015-2017]. Hinge reaction force was measured using a strain gauge-equipped Penfield dissector. Computed tomography (CT) images were evaluated at postoperative day 1 and delayed phase (mean 2.5 years).
Mean hinge reaction force was 0.70 kgf (6.87 N). Early hinge fracture occurred in 24/173 laminae (13.9%). The fracture group showed significantly lower force than the non-fracture group (0.46 vs. 0.74 kgf, P<0.001). Receiver operating characteristic (ROC) analysis revealed area under the curve (AUC) of 0.798 with optimal cutoff of 0.59 kgf. At delayed phase, 62% of early fractures (13/21) demonstrated bone healing, and the overall fracture rate decreased to 8.2%. No lamina showed subsidence exceeding 1 mm. Neither Japanese Orthopaedic Association (JOA) recovery rate (P=0.63) nor postoperative pain visual analog scale (VAS) scores differed between groups.
This study provides the first quantitative characterization of greenstick fracture reaction force in cervical laminoplasty. The established force benchmarks and predictive threshold (0.59 kgf) offer foundational biomechanical data for developing simplified clinical assessment devices, force-guided selective fixation strategies, and objective surgical training standards.

PMID:
42434578
Bibliographic data and abstract were imported from PubMed on 11 Jul 2026.

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