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

Purpose: 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.

Methods: 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.

Results: 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.

Conclusion: 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.