Thumb Muscle Activation During First Dorsal Interosseous Exercise in Thumb Base Osteoarthritis

Official title

A Between-Group Comparison of First Dorsal Interosseous and Abductor Pollicis Longus Muscle Activation During First Dorsal Interosseous Exercise in Individuals With and Without Thumb Base Osteoarthritis

Overview

The aim of this study is to investigate whether there are differences in muscle activation of the First Dorsal Interosseous (FDI) and the Abductor Pollicis Longus (APL) between individuals with and without trapeziometacarpal osteoarthritis (TMC OA) of the thumb. The study also seeks to identify which exercises are most effective for activating these muscles, in order to inform rehabilitation strategies for patients. The FDI has been defined as a key stabilizer of the thumb TMC joint. However, the literature reports various protocols for FDI activation and limited information on APL behavior during these exercises. OA TMC of the thumb can cause pain, decreased thumb strength, impaired hand function, and difficulty performing activities of daily living (ADLs). Appropriate rehabilitation is essential to maintain muscle function, limit joint degeneration, and improve hand performance; however, the exercises that optimally activate the FDI and APL muscles are not yet established. Participants will perform a series of standardized exercises and functional tasks designed to activate the FDI and APL muscles. Exercises include FDI strengthening with elastic bands in different hand positions (palmar and ulnar support), as well as exercises with the thumb in greater abduction. Functional tasks simulating everyday activities (e.g., turning a key, picking up a coin, writing, squeezing a tube of toothpaste, and holding a glass of water) will also be performed. Muscle activity will be recorded using surface electromyography (sEMG) during all tasks. Adults aged 40 years and older, both men and women, with TMC osteoarthritis and healthy controls without osteoarthritis will be invited to participate. Researchers will measure the activation patterns of the FDI and APL muscles during the exercises and functional tasks. The study aims to identify exercises that optimally activate these muscles, providing evidence to guide the rehabilitation of patients with thumb base osteoarthritis.

Detailed description

Trapeziometacarpal osteoarthritis (OA TMC) of the thumb is a chronic and progressive degenerative disease characterized by loss of articular cartilage, subchondral sclerosis, capsuloligamentous laxity, and osteophyte formation in the first metacarpal. Patients typically present with pain and muscle weakness, which impair hand function and limit activities of daily living (ADLs), resulting in a considerable personal and social burden, including reduced quality of life and work disability. Previous studies have highlighted the clinical importance of thumb TMC joint stabilizers. Research has demonstrated that the first dorsal interosseous (FDI) functions as the main stabilizer of the TMC joint, whereas the abductor pollicis longus (APL) acts as a primary destabilizer. These findings suggest that rehabilitation programs should focus on strengthening the FDI to improve joint stability. However, despite the clinical importance of targeting these muscles, the literature reports varied exercise protocols for FDI activation and limited information on how the APL behaves during the same exercise.

The aim of this study is to investigate whether there are differences in muscle activation of the FDI and APL between individuals with and without thumb OA TMC and to identify which exercises are most effective or activating these muscles in order to inform rehabilitation strategies. Various activities of daily living will also be analyzed to assess FDI and APL activation during functional tasks. Adequate rehabilitation is essential for maintaining muscle function, slowing the progression of joint degeneration, and improving hand performance, yet it remains unclear which exercises and tasks optimally engage the FDI and APL muscles.

This is a cross-sectional observational comparative study with both within-subject and between-group analyses. The study includes two groups: adults aged 40 years and older, both men and women, with a clinical diagnosis of OA TMC and healthy controls without musculoskeletal or neurological disorders affecting the hand. Exclusion criteria include sensory disturbances such as numbness or tingling, cardiac pacemaker implantation, upper limb entrapment neuropathies or cervical radiculopathy, neuromuscular diseases, systemic conditions including diabetes or hypothyroidism, history of cancer, rheumatoid arthritis, anticoagulation therapy, chemotherapy, exposure to neurotoxins, or recent upper limb trauma or surgery.

Surface electromyography (sEMG) is used to record muscle activity of the FDI and APL. Skin is prepared by shaving if necessary and cleaning with alcohol to reduce impedance and ensure optimal adherence of surface electrodes. Bipolar surface electrodes with a diameter of 20 millimeters and an inter-electrode distance of 20 millimeters are placed according to SENIAM guidelines. For the FDI, electrodes are positioned over the dorsal belly of the muscle aligned with fiber direction, with one electrode in the distal ulnar region between the first and second metacarpals. For the APL, electrodes are placed approximately five centimeters distal to the wrist, medial to the radius, longitudinally aligned and transversely away from adjacent muscles. Electrode placement is verified by palpation and selective activation tasks.

Participants perform a series of twelve standardized exercises and functional tasks commonly used in conservative rehabilitation of OA TMC. The first six tasks are exercises designed to activate the FDI and include variations of index finger abduction with ulnar support, elastic resistance with ulnar support, elastic resistance with palmar support using a ball, palmar support without resistance, elastic resistance with palmar support, and elastic resistance with maximal palmar abduction of the thumb. The remaining six tasks simulate ADLs and include turning a key toward the ulnar side, turning a key toward the radial side, picking up a coin, writing a word with a pen, squeezing a full tube of toothpaste, and holding a glass of water while performing a drinking gesture. Each task is performed in three consecutive three-second isometric repetitions with a thirty-second rest between repetitions to minimize fatigue.

It is hypothesized that individuals with thumb TMC osteoarthritis will demonstrate altered activation patterns of the FDI and APL compared with healthy controls, and that specific exercises and functional tasks will elicit greater FDI activation, supporting targeted interventions to enhance joint stability and hand function in patients with thumb base osteoarthritis.

Primary outcome measures

• Surface electromyographic amplitude of the First Dorsal Interosseous muscle. [Time frame: During performance of the 12 standardized exercises and functional tasks]
• Surface electromyographic amplitude of the Abductor Pollicis Longus muscle [Time frame: During performance of the 12 standardized exercises and functional tasks]

Eligibility criteria

Inclusion criteria for the TMC OA group:

\- Clinical diagnosis of thumb TMC osteoarthritis.

Inclusion criteria for the healthy group:

\- Participants with no history of musculoskeletal or neurological disorders affecting the dominant hand were included.

Exclusion criteria

• Presence of numbness, tingling, or other sensory disturbances
• Cardiac pacemaker implantation
• Upper limb entrapment neuropathy or cervical radiculopathy
• History of neuromuscular disease, polyneuropathy, or plexopathy
• Systemic diseases such as diabetes, hypothyroidism, or chronic liver or kidney disease
• History of cancer, rheumatoid arthritis, active anticoagulation therapy, chemotherapy, or exposure to neurotoxins
• Recent upper limb soft tissue or bone injury (trauma, fracture, or surgery of the arm or neck).

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Observational model

Case-crossover

Study locations

Spain · 1 center

• Universidad de Málaga — Málaga

Publications

• McGee C, O'Brien V, Van Nortwick S, Adams J, Van Heest A. First dorsal interosseous muscle contraction results in radiographic reduction of healthy thumb carpometacarpal joint. J Hand Ther. 2015 Oct-Dec;28(4):375-80; quiz 381. doi: 10.1016/j.jht.2015.06.002. Epub 2015 Jun 27. PMID 26209165
• Bertozzi L, Valdes K, Vanti C, Negrini S, Pillastrini P, Villafane JH. Investigation of the effect of conservative interventions in thumb carpometacarpal osteoarthritis: systematic review and meta-analysis. Disabil Rehabil. 2015;37(22):2025-43. doi: 10.3109/09638288.2014.996299. Epub 2015 Jan 5. PMID 25559974
• Ahern M, Skyllas J, Wajon A, Hush J. The effectiveness of physical therapies for patients with base of thumb osteoarthritis: Systematic review and meta-analysis. Musculoskelet Sci Pract. 2018 Jun;35:46-54. doi: 10.1016/j.msksp.2018.02.005. Epub 2018 Feb 21. PMID 29510316
• Tossini NB, Melo CS, Braz de Oliveira MP, Moreira RFC, Serrao PRMDS. Effect of physical therapy interventions in individuals with primary thumb carpometacarpal osteoarthritis: a systematic review and meta-analysis. Disabil Rehabil. 2024 Dec;46(26):6251-6265. doi: 10.1080/09638288.2024.2325652. Epub 2024 Mar 7. PMID 38450686
• Deveza LA, Hunter DJ, Wajon A, Bennell KL, Vicenzino B, Hodges P, Eyles JP, Jongs R, Riordan EA, Duong V, Min Oo W, O'Connell R, Meneses SR. Efficacy of combined conservative therapies on clinical outcomes in patients with thumb base osteoarthritis: protocol for a randomised, controlled trial (COMBO). BMJ Open. 2017 Jan 12;7(1):e014498. doi: 10.1136/bmjopen-2016-014498. PMID 28082368
• McVeigh KH, Kannas SN, Ivy CC, Garner HW, Barnes CS, Heckman MG, Brushaber DE, Murray PM. Dynamic stabilization home exercise program for treatment of thumb carpometacarpal osteoarthritis: A prospective randomized control trial. J Hand Ther. 2022 Jul-Sep;35(3):435-446. doi: 10.1016/j.jht.2021.06.002. Epub 2021 Jul 24. PMID 34312043
• Osteras N, Hagen KB, Grotle M, Sand-Svartrud AL, Mowinckel P, Kjeken I. Limited effects of exercises in people with hand osteoarthritis: results from a randomized controlled trial. Osteoarthritis Cartilage. 2014 Sep;22(9):1224-33. doi: 10.1016/j.joca.2014.06.036. Epub 2014 Jul 5. PMID 25008206
• Cantero-Tellez R, Algar LA, Valdes KA, Naughton N. Clinical effects of proprioceptive thumb exercise for individuals with carpometacarpal joint osteoarthritis: A randomized controlled trial. J Hand Ther. 2022 Jul-Sep;35(3):358-366. doi: 10.1016/j.jht.2022.06.009. Epub 2022 Aug 23. PMID 36008246

Identifiers

NCT: NCT07421089 · UMA-AOTMC-2026-001

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗