title: In vivo strain in the deep and superficial regions of the human patellar tendon.
abstract: This study investigated strain differences within the patellar tendon (PT) mid-region using an ultrasound-based digital image correlation (DIC) method. Six healthy young participants performed six knee extensions to 60% of maximal voluntary isometric contraction on 2 days. Sagittal ultrasound videos recorded during each contraction were analyzed using the DIC method to determine the strain-torque relationships of the superficial, deep, and whole PT mid-regions. Significantly greater strain was observed in the deep vs superficial layer of the PT mid-region for all contraction intensities, with peak strains of 5.8% (SD 1.7) and 4.5% (SD 1.5), respectively. DIC-based measures of peak tendon strain were repeatable within [intraclass coefficients (ICC) >0.97] and between sessions (ICCs >0.83) and agreed well with the conventional point-to-point method. This study confirmed that significant differences exist between deep and superficial layers of PT mid-region during ramped isometric extensions. These findings support the use of DIC to examine regional strain patterns within the PT mid-region that may be important in the context of tendon injury and adaptation.
authors.affiliation: School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Southport, Queensland, Australia.
authors.forename: D
authors.initials: D
authors.lastname: Lee
authors.affiliation: School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Southport, Queensland, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Barrett
authors.affiliation: School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Southport, Queensland, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Ryan
authors.affiliation: School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Southport, Queensland, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Saxby
authors.affiliation: School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Southport, Queensland, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Newsham-West
authors.affiliation: School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Southport, Queensland, Australia.
authors.forename: S J
authors.initials: SJ
authors.lastname: Obst
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D017847:Patellar Ligament / Q000000981:diagnostic imaging* / Q000502:physiology; D013314:Stress, Mechanical; D014463:Ultrasonography
keywords: Patellar; digital image correlation; imaging; tendon; ultrasound