Partial-Hand Prosthesis Users Show Improved Reach-to-Grasp Behaviour Compared to Transradial Prosthesis Users with Increased Task Complexity

Abstract

Purpose: Approaches to improve outcomes after upper-extremity amputation remain poorly understood. Different levels of amputation may affect prosthetic device acceptance, function, and use. Examining differences in behavioural and functional performance for different levels of prosthesis use may provide vital information about unique motor control challenges across levels of amputation.

Materials and methods: Participants without amputation completed simple and complex goal-directed reach-to-grasp motor actions using either a transradial or partial-hand prosthesis simulator. We hypothesised that participants using a partial-hand device would show greater functional adaptation compared to participants using a transradial device, measured by (1) lower movement duration, (2) lower reach duration, (3) higher reach peak velocity, and (4) lower placement error. Second, we hypothesised that increased task complexity would lead to greater functional adaptation, particularly in partial-hand users.

Results: In the complex task, partial-hand users demonstrated variable grasp approaches, an effect not seen in the simple task or in transradial users. Partial-hand users showed significantly higher reach peak velocities compared to transradial users, regardless of grasp strategy in the complex but not the simple task. All groups showed decreases in movement duration over time in the complex task, but only partial-hand users improved in the simple task.

Conclusion: There is a gap in our understanding of how people adapt to amputations of different levels. This work clarifies how device and environmental constraints contribute to unique action outcomes, and influence motor learning, which is crucial for optimising rehabilitation.