The functional assessment of myoelectric control algorithms by persons with amputation promotes the overarching goal of the field of prosthetic limb design: to replace what was lost. However, many studies use experimental paradigms with virtual interfaces and able-bodied subjects that do not capture the challenges of a clinical implementation with an amputee population. A myoelectric control system must be robust to variable physiology, loading effects of the prosthesis on the limb, and limb position effects during dynamic tasks. Here persons with transradial limb loss performed activities of daily living using a postural controller and multi-functional prosthetic hand in order to verify that the postural controller was robust to these clinical challenges. The Southampton Hand Assessment Procedure was performed by persons with limb loss and able-bodied subjects. The results indicate that persons with limb loss and able-limbed subjects achieved the same performance and therefore that the clinical challenges were overcome. Persons with limb loss achieved 55% of physiological hand function on average. Also, the postural controller is compared to other state of the art myoelectric controllers and prosthetic hands previously tested. This work confirms that the postural controller is potentially a clinically-viable method to control myoelectric multi-functional prosthetic hands.