Kinematics of Trapeziometacarpal Joint During First Dorsal Interosseous Maneuver in Osteoarthritic Patients: An Imaging Study Using Real-Time Magnetic Resonance Imaging and Ultrasonography.

Abstract

Purpose: First dorsal interosseous (FDI) exercise is a dynamic stability exercise recommended for patients with trapeziometacarpal osteoarthritis (TMC-OA), although its biomechanical efficacy has only been examined in healthy subjects. This study used real-time magnetic resonance imaging (MRI) and ultrasonography to elucidate the kinematic effects of the FDI maneuver used for the treatment of TMC-OA.

Methods: Using a real-time MRI protocol developed for continuous imaging of TMC movements, TMC joints were examined in 10 end-stage patients with TMC-OA and 10 thumbs of five healthy volunteers while performing FDI maneuvers. Changes in translation and tilt of the first metacarpal (MC1) were evaluated using sagittal and coronal images, and FDI volume was analyzed. Based on TMC joint kinematics determined according to dynamic ultrasound observations, the subjects were classified into three groups. Patients with TMC-OA received hand therapy with orthosis and FDI exercise for a period of 1 month.

Results: Magnetic Resonance Imaging analyses of the TMC-OA patients demonstrated that radial translation and ulnar/dorsal tilt of the MC1 were significantly greater, whereas FDI volume was significantly lower than healthy thumbs. Results of ultrasound analyses showed increased dorsal subluxation of the TMC joint in six patients with TMC-OA. These values were decreased in six healthy thumbs and unchanged in the remaining thumbs. All of the patients with TMC-OA demonstrated significantly improved pain intensity and pinch strength following implementation of the therapy program, although no direct correlations with MC1 kinematic alterations of were noted.

Conclusions: Thumbs in patients with TMC-OA and healthy thumbs have different kinematics during FDI maneuvers. An atrophic FDI may not be an efficient dynamic stabilizer for TMC-OA. In patients with a subluxated TMC-OA, the FDI maneuver was ineffective or caused exacerbation, contradicting previous findings. For a goal of improving dynamic stability in patients with TMC-OA, FDI exercise should be avoided.

Type of study/level of evidence: Therapeutic Ⅳ.