Structural and clinical disease severity in thumb osteoarthritis: A pilot study integrating imaging analysis and pain mechanisms.

Abstract

Background: We sought to explore pain mechanisms in thumb carpometacarpal osteoarthritis using imaging-based biomarkers and clinical pain evaluation techniques, and to identify potential pain phenotypes among patients with thumb carpometacarpal osteoarthritis that may be useful for designing more targeted research and intervention strategies.

Study design: Pilot case-control study.

Methods: Participants (n=9 healthy; n=9 thumb osteoarthritis) underwent static CT scans of the hand and wrist, accompanied by a calibration phantom with known densities. Participants completed patient-reported outcome measures targeting different pain mechanisms. Average subchondral volumetric bone mineral density was analyzed in the first metacarpal and third metacarpal at three depths (0-2.5, 2.5-5.0, and 5.0-7.5 mm), while the trapezium was studied at five depths (0-1.25, 1.25-2.5, 2.5-3.75, 3.75-5.0, and 5.0-6.25 mm). Joint contact area of first metacarpal and trapezium was averaged for all participants. All patient-reported outcome measures were analyzed separately using conceptualized thresholds to characterize pain mechanisms.

Results: Post hoc power was low (26%). The thumb osteoarthritis cohort showed statistically significant lower bone density than the healthy cohort (p<0.05), save for the trapezium's top layer. Effect sizes ranged from 1.06-1.77, with the largest effect in the trapezium's third layer (d=1.77), favoring the healthy cohort. Nociceptive pain was the dominant pain phenotype, suggesting peripheral pain mechanisms in this sample.

Conclusions: Despite limited generalizability due to small sample size, these preliminary findings suggest biological contributors---such as local bone density loss and nociceptive pain dominance---to clinical disease severity in thumb osteoarthritis.