Do Osteophytes Alter Thumb Carpometacarpal Biomechanics? A Preliminary in Vitro Study

Osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint is prevalent and debilitating, marked by substantial loss of range of motion (ROM) and overall function. CMC OA is associated with osteophyte growth, but the impact of this growth on CMC ROM has not been systematically characterized. Our goal was to determine whether osteophytes decrease CMC ROM and, if so, whether these decreases are direction-dependent. A robotic musculoskeletal simulation system was used to manipulate 18 CMC specimens with a range of joint health following three test protocols: (1) Rotational ROM in flexion, extension, abduction, adduction, and 20 combined directions, (2) Internal/External Rotation (IR/ER), and (3) Translational ROM in volar, dorsal, radial, ulnar, and 4 combined directions. Osteophyte volume (OV) was computed in total and by volar, dorsal, radial, and ulnar quadrants, and correlations with ROM were computed by direction and in total. We found that an increase in overall trapezial OV was associated with a reduction in overall rotational ROM and IR/ER, but not with translational ROM. We found decreased extension was associated with increased ulnar, volar, and radial OV, and decreased abduction was associated with increased volar OV. Decreased internal rotation was associated with increased ulnar, volar, and radial OV. The proposed method and findings of this pilot study will lay the groundwork for a larger investigation into the relationship between pathological structure and function in the CMC joint.