This study aims to quantitatively evaluate thumb proprioception in individuals diagnosed with trapeziometacarpal (TMC) joint osteoarthritis (OA) and to compare the findings with healthy individuals. As a secondary aim, potential determinants that may influence proprioceptive function of the thumb joints will be examined systematically. In this context, relationships between thumb proprioception and participants' demographic characteristics (age, sex, body weight, occupational characteristics, and OA severity), motor functions (muscle strength of opponens pollicis, first dorsal interosseous, abductor pollicis brevis/longus, and flexor pollicis brevis/longus, as well as fine motor performance), sensory functions (pain, light touch/pressure sensation, and vibration sensation), and emotional status (fear of movement, anxiety, and depression) will be investigated. In addition, whether proprioceptive measures differ across radiographic severity levels will be evaluated within the TMC OA group.
The study is conducted using a cross-sectional case-control design. Individuals with TMC OA are compared with an healthy control group. In the TMC OA group, disease severity is classified based on radiographs according to the Eaton-Littler classification (Stages 1-4).
Thumb proprioception is assessed using two main outcomes: (1) joint position sense (JPS) error values for the TMC, metacarpophalangeal (MCP), and interphalangeal (IP) joints, and (2) pinch aperture proprioception error values. To evaluate the repeatability of pinch aperture proprioception measurement in individuals with TMC OA, an intra-rater test-retest approach is used; the same test is administered to 30 participants by the same assessor within one week.
Sample size is planned to support the primary hypothesis. For the primary group comparisons, at least 20 participants per group are targeted. To enable planned subgroup analyses by OA severity, the study aims to include 20 individuals for each Eaton-Littler stage (Stages 1-4) in the TMC OA group (total 80 individuals with TMC OA) and 20 healthy controls, resulting in a total target sample size of 100 participants.
Statistical analyses will be performed using SPSS for Windows version 22.0. Continuous variables will be reported as mean ± standard deviation or median (interquartile range), and categorical variables as frequency and percentage. Depending on data distribution, parametric or non-parametric methods will be used. Proprioceptive outcomes will be compared between the TMC OA group and the age-matched healthy control group using appropriate two-group comparison tests. Planned subgroup comparisons across radiographic severity levels (Eaton-Littler Stages 1-4) will be conducted within the TMC OA group. Associations between proprioceptive outcomes and demographic, motor, sensory, and emotional factors will be examined using correlation analyses and, where appropriate, multiple regression models. Statistical significance will be set at two-sided p \< 0.05, and effect sizes will be reported where applicable.
Ethics approval was obtained from the Hacettepe University Faculty of Physical Therapy and Rehabilitation Research Ethics Committee (Session date: 23 Oct 2025; Session number: 2025/22; Decision number: FTREK25/112; validity: 23 Oct 2025-23 Oct 2027). All participants received verbal and written information about the purpose and scope of the study, the assessments to be performed, potential discomfort, and their right to withdraw at any time without providing a reason; written informed consent was obtained prior to assessments. A safety approach was adopted such that measurements were discontinued if a participant reported discomfort during assessment. To ensure confidentiality, all participants were assigned a unique study code, and identifying information was stored separately from measurement data. Analyses were conducted using de-identified datasets. Data were stored in password-protected digital files, and any paper forms were kept in a locked cabinet with access restricted to the research team.
