Oral Presentation ANZBMS-MEPSA-ANZORS 2022

Functional group differences in the biomechanical and biochemical properties of human hand tendons (#14)

Carina Blaker 1 , Dylan Ashton 1 , Samantha Hefferan 1 , Yolanda Liu 2 , David Chang 3 , Richard Lawson 3 , Christopher Little 2 , Elizabeth Clarke 1
  1. Murray Maxwell Biomechanics Laboratory, Institute of Bone and Joint Research, Kolling Institute, University of Sydney, Sydney, NSW, Australia
  2. Raymond Purves Bone and Joint Research Laboratories, Institute of Bone and Joint Research, Kolling Institute, University of Sydney, Sydney, NSW, Australia
  3. Department of Hand Surgery, Royal North Shore Hospital, Northern Sydney Local Health District, Sydney, NSW, Australia

Traumatic injury is common in hand tendons, with variable long-term outcomes in different tendons1,2. Understanding variations in tendon properties is critical for improving treatments designed to restore functional capacity. The aim of the study was to measure the biomechanical and biochemical properties of upper limb tendons and compare differences between functional groups.

Twenty-four different hand/wrist tendons (grouped by function, Fig1a) were sourced from 8 fresh-frozen human cadavers (3 female, 5 male; 49-65years). Tendons were tested to failure under tension (5% strain/s). Biomechanical outcomes included cross-sectional area (CSA), maximum load, ultimate tensile strength (UTS), and elastic modulus. A mid-region sample was papain digested to measure glycosaminoglycan and hydroxyproline contents. Differences between tendon groups were analysed using mixed-effects linear regression models (covariates: sex and interactions with age). Group comparisons were evaluated at the mean age (56y), and Benjamini-Hochberg used for multiple comparisons.

Wrist flexors and extensors had the greatest maximum loads (1018.2±501.4N; 1162.2±327.7N) and CSA (12.9±7.0mm2; 13.2±4.3mm2) while digital extensors had the lowest (load: 486.0±146.8N; CSA: 5.0±1.4mm2). After normalising by CSA, there were fewer significant differences between tendon groups for UTS and modulus (Fig1b,c). Digital extensors were significantly stronger than wrist (P=0.0004) and digital (P≤0.0082) flexors. Thumb extensors had significantly higher moduli than both wrist flexors and extensors (P≤0.0005), and digital flexors (P≤0.0048). Glycosaminoglycan content was similar across extensors and significantly lower in most flexors (P≤0.0201) except for deep digital (Fig1d). There were many between group differences in hydroxyproline content (P≤0.0054; Fig1e) and it was lowest in digital extensor tendons (77.6±7.7ug/mg).

The results of this study highlight unique mechanical and compositional differences between tendon functional groups in the human hand. Improved understanding of unique, normal tendon properties assists the development of more precise benchmark targets for the development and selection of graft materials and bench testing of responses to new therapeutics.

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  1. Newport ML, Tucker RL. New Perspectives on Extensor Tendon Repair and Implications for Rehabilitation. J Hand Ther. 2005;18(2):175-181
  2. Dy CJ, Daluiski A, Do HT, Hernandez-Soria A, Marx R, Lyman S. The Epidemiology of Reoperation After Flexor Tendon Repair. The Journal of Hand Surgery. 2012;37(5):919-924