Thumb Proprioception in Trapeziometacarpal Osteoarthritis

Joint mobility of the thumb was assessed by measuring active range of motion (ROM) of the trapeziometacarpal (TMC), metacarpophalangeal (MCP), and interphalangeal (IP) joints using a standard goniometer. For the TMC joint, abduction, adduction, flexion, extension, and opposition were evaluated. Flexion and extension ROM of the MCP and IP joints were also measured. All joint mobility values were recorded in degrees, with higher values indicating greater joint mobility.

Thumb opposition was additionally evaluated using the Kapandji opposition score, which grades the maximal opposition achieved by the thumb pulp on a 10-point scale. A score of 1 corresponds to contact with the radial side of the proximal phalanx of the index finger, whereas a score of 10 corresponds to contact with the distal palmar crease of the little finger.

Thumb re-opposition (reposition ability) was assessed as the minimal contact point reached during return from maximal opposition, recorded using the Kapandji opposition scale (0-10).

Generalized joint hypermobility was assessed using the Beighton Hypermobility Score. This nine-item scoring system evaluates joint laxity at multiple anatomical sites, yielding a total score ranging from 0 to 9. Higher scores indicate greater joint laxity, and individuals with a score of 4 or higher were classified as hypermobile.

Motor function of the thumb and hand was evaluated by assessing manual muscle strength and grip and pinch strength. Manual muscle testing was performed to evaluate the strength of the opponens pollicis, abductor pollicis brevis and longus, first dorsal interosseous, and flexor pollicis brevis and longus muscles. Muscle strength was graded according to the Lovett scale and the Medical Research Council (MRC) classification, with higher scores indicating greater muscle strength.

Hand grip strength will be assessed in the standardized position recommended by the American Society of Hand Therapists: seated, with the arm adducted and in neutral rotation, elbow flexed to 90°, forearm in mid-rotation, and wrist in neutral position. A Jamar hand dynamometer (Jamar; JLW Instruments, Chicago, IL) will be used to measure standard grip strength. The dynamometer handle will be set at the second position, and participants will be instructed to maintain the testing position and squeeze maximally. Three trials will be performed, and the mean value will be recorded in kilograms-force.

Lateral pinch strength will be assessed in the standardized position recommended by the American Society of Hand Therapists: seated, with the arm adducted and in neutral rotation, elbow flexed to 90°, forearm in mid-rotation, and wrist in neutral position. A pinch gauge (Pro Med Products, Atlanta, GA) will be used. Participants will be instructed to squeeze the pinch gauge maximally between the thumb pulp and the lateral aspect of the index finger while maintaining the testing position. Three trials will be performed, and the mean value will be recorded in kilograms-force.

Tripod pinch strength will be assessed in the standardized position recommended by the American Society of Hand Therapists: seated, with the arm adducted and in neutral rotation, elbow flexed to 90°, forearm in mid-rotation, and wrist in neutral position. A pinch gauge (Pro Med Products, Atlanta, GA) will be used. Participants will be instructed to squeeze the pinch gauge maximally between the thumb, index finger, and middle finger while maintaining the testing position. Three trials will be performed, and the mean value will be recorded in kilograms-force.

Tip pinch strength will be assessed in the standardized position recommended by the American Society of Hand Therapists: seated, with the arm adducted and in neutral rotation, elbow flexed to 90°, forearm in mid-rotation, and wrist in neutral position. A pinch gauge (Pro Med Products, Atlanta, GA) will be used. Participants will be instructed to squeeze the pinch gauge maximally between the thumb pulp and the index finger pulp while maintaining the testing position. Three trials will be performed, and the mean value will be recorded in kilograms-force.

Pain intensity at rest was evaluated using the Visual Analog Scale (VAS), scored from 0 (no pain) to 10 (worst imaginable pain), with higher scores representing greater pain intensity.

Pain intensity during activity was evaluated using the Visual Analog Scale (VAS), scored from 0 (no pain) to 10 (worst imaginable pain), with higher scores representing greater pain intensity.

Pain frequency and occurrence were classified using the Alnot classification according to the conditions under which pain occurs (0 = no pain, 1 = pain during intense exertion, 2 = pain during daily activities, 3 = spontaneous intermittent pain, 4 = continuous pain).

Light touch and pressure sensation were assessed using the Semmes-Weinstein Monofilament (SWM) test (Baseline® Tactile™ Monofilament - 20-piece set). Sensory threshold was determined using graded nylon monofilaments, with a threshold value of 2.83 mg/cm² considered normal. Perception of monofilaments greater than 2.83 in any of the first three digits was interpreted as sensory impairment. Sensory performance was recorded based on the smallest monofilament perceived, with higher values indicating reduced cutaneous sensitivity.

Vibration sense was evaluated using a 128 Hz tuning fork applied to the radial styloid. The duration of perceived vibration was recorded in seconds, and values of 8 seconds or less were considered indicative of impaired vibration sense. Longer perception times reflected better vibration sensitivity.

Grip function was assessed across five commonly described grasp patterns in daily activities: power grip, key pinch, pinch grip, cylindrical grip, and precision grip. Functional difficulty for each grasp type was rated using a three-level Likert-type scale, with scores of 4 indicating no or mild difficulty, 2 indicating moderate difficulty, and 0 indicating severe difficulty or inability to perform the task. The total score ranged from 0 to 20, with lower scores reflecting poorer hand function. Individuals with a total score of 16 or less were classified as having moderate to poor hand function, defined by the inability to perform at least one grasp type and difficulty in at least two grasp patterns.

Functional sensory performance and manual dexterity were assessed using the Moberg Pick-Up Test. The test evaluates the ability to manipulate small objects using tactile input and fine motor control. Performance was quantified as the time required to complete the task, recorded in seconds. Mean completion time across repeated trials was used for analysis, with longer times indicating reduced functional performance.

Thumb-specific functional disability was assessed using the Thumb Disability Index (TDX), a patient-reported outcome measure consisting of 20 items across three domains: thumb-related functional activities, pain, and satisfaction with the affected thumb. Total and subscale scores were calculated and transformed to a 0-100 scale, where higher scores indicate greater functional limitation. TDX scores were not calculated when more than 10% of items were left unanswered.

Overall upper extremity function was evaluated using the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) questionnaire. This 11-item self-reported measure assesses symptoms and functional limitations related to upper extremity use. Total scores range from 0 to 100, with higher scores indicating greater disability. The Turkish version of the QuickDASH has demonstrated established validity and reliability.

Emotional status was assessed using the Hospital Anxiety and Depression Scale (HADS). The HADS is a 14-item self-report questionnaire consisting of two subscales that assess symptoms of anxiety (7 items) and depression (7 items). Each item is scored on a 4-point Likert scale ranging from 0 to 3, yielding subscale scores between 0 and 21. Higher scores indicate greater emotional distress. Scores of 0-7 are considered within the normal range, scores of 8-10 indicate possible emotional disturbance, and scores of 11 or higher suggest clinically relevant anxiety or depression. The HADS is intended as a screening tool rather than a diagnostic instrument and reflects emotional status over the previous week.

Fear of movement was evaluated using the Tampa Scale of Kinesiophobia (TSK). The TSK is a 17-item Likert-type questionnaire designed to assess fear of movement and re-injury associated with pain. Each item is scored from 1 (strongly disagree) to 4 (strongly agree), resulting in a total score ranging from 17 to 68. Four items are reverse scored, and higher total scores indicate greater levels of kinesiophobia. A total score above 37 is commonly used to indicate a high level of fear of movement. The Turkish version of the TSK has demonstrated acceptable validity and test-retest reliability.

Thumb joint positional awareness during pinch will be assessed in a quiet room under a passive (no-load) condition. The trapeziometacarpal (TMC), metacarpophalangeal (MCP), and interphalangeal (IP) joints will be evaluated. The examiner passively sets Kapandji position 3 (TMC and MCP 30° flexion; IP 20°), participants encode the position for approximately 30 seconds, and then reproduce the posture with eyes closed. Joint angles are measured with a manual goniometer (degrees). A practice trial precedes testing; each measure is taken 3 times and averaged, with 2-minute rest between trials.

Thumb joint positional awareness during pinch will be assessed in a quiet room under an active load-bearing condition. The trapeziometacarpal (TMC), metacarpophalangeal (MCP), and interphalangeal (IP) joints will be evaluated. The same target posture (Kapandji position 3: TMC and MCP 30° flexion; IP 20°) is set and encoded, then reproduced with eyes closed during maximal voluntary pinch on a pinch dynamometer. Joint angles are measured with a manual goniometer (degrees). A practice trial precedes testing; each measure is taken 3 times and averaged, with 2-minute rest between trials.