title: Development of a 4-axis load cell used for lumbar interbody load measurements.
abstract: Numerous studies have assessed lumbar interbody fusion, but little data from direct interbody load measurements exists. This manuscript describes an interbody fusion cage with integrated 4-axis load cell that can simulate implant heights of 13, 15, 17, 19 and 21 mm. The calibrated load cell was accurate to within 7.9% for point compressive loads over the central 8 mm x 8 mm region, but up to 26.8% for eccentric loads on the outer 16 mm x 16 mm rim of the device (although typically errors were less than half). Anterior-posterior shear and lateral shear loads did not affect compressive load measurement (<1.0% and <3.5%, respectively). Moments calculated from 4 load sensing corner pillars demonstrated errors below 2.3% in lateral bending and 2.1% in flexion-extension. Although this device does not have the accuracy of other much larger corpectomy implants, it incorporates four channels of load and simulates multiple implant heights, making for a favorable comparison in this restricted space. This device has immediate use in cadaveric testing, providing data previously not attainable, and serves as a novel technological step towards an implantable interbody device with multi-axis load sensing capability. As per the authors' knowledge, no such device has previously been described.
authors.affiliation: Gehring Center for Biomechanics and Implant Analysis, William Beaumont Hospital, Royal Oak, MI 48067, USA. ckd.biomed@gmail.com
authors.forename: Constantine K
authors.initials: CK
authors.lastname: Demetropoulos
authors.forename: Craig R
authors.initials: CR
authors.lastname: Morgan
authors.forename: Dilip K
authors.initials: DK
authors.lastname: Sengupta
authors.forename: Harry N
authors.initials: HN
authors.lastname: Herkowitz
mesh_terms: D001696:Biomechanical Phenomena; D002138:Calibration; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology* / Q000601:surgery; D008422:Materials Testing / Q000295:instrumentation* / Q000379:methods; D008954:Models, Biological; D019736:Prostheses and Implants; D013123:Spinal Fusion; D016474:Weight-Bearing