Morphological and Mechanical Property Differences in Trapeziometacarpal Ligaments of Healthy and Osteoarthritic Female Joints

To identify changes in morphological and mechanical properties in the volar ligament complex (VLC), dorsoradial ligaments (DRL), and posterior oblique ligaments (POL) in healthy and osteoarthritic female trapeziometacarpal (TMC) joints. Twenty-four fresh-frozen female cadaveric TMCs were separated into (1) younger healthy/early-stage osteoarthritic, (2) elder healthy/early-stage osteoarthritic, and (3) advanced-stage osteoarthritic groups based on age and Eaton-Littler grading. Stress relaxation and load-to-failure testing were performed to characterize mechanical tensile properties. Light imaging and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) were performed to further assess enthesis structural integrity. The VLC in advanced-stage osteoarthritic TMCs had attenuated mechanical properties in stress relaxation experiments compared to the elder healthy/early-stage osteoarthritic specimens: Young's modulus at 20% strain (P = 0.044), instantaneous (P = 0.023), relaxed (P = 0.017) moduli. VLCs in advanced-stage osteoarthritic TMCs also had significantly lower properties in the load-to-failure experiments compared to the younger healthy/early-stage osteoarthritic specimens: stiffness (P = 0.048), ultimate load (P = 0.017), toughness (P = 0.003). Light and SEM/EDS imaging revealed partial detachment and loss of enthesis mineral gradient at VLC metacarpal insertion in advanced-stage osteoarthritic specimens. There were no mechanical or structural changes in the DRL and POL between experiment groups. VLC morphological and mechanical properties deteriorate across progressively severe osteoarthritis classifications while the DRL and POL remain unchanged. The attenuated mechanical properties of VLCs in advanced-stage osteoarthritic TMCs can be explained by ligament degradation as evidenced by partial detachment and loss of mineral gradient at the metacarpal insertion.