Advantages of a flexible wrist unit compared to a static wrist unit in people using an arm prosthesis.

For the usage of the hand of an arm prosthesis, accurate positioning of the
hand is of high importance. Conventional prostheses are usually equipped with a
wrist unit that can only rotate, either passively or actively. This implies
that the position of the hand in space is mainly determined by the more
proximally located joints, i.e. the shoulder and elbow, and even the trunk.
Several studies reported that restriction of flexion/extension and/or
restriction of pronation/supination in the wrist both reveal compensatory
motions from more proximally located segments (Adams, Grosland, Murphy, &
McCullough, 2003; MacPhee, 2007; Carey, Jason Highsmith, Maitland, & Dubey,
2008; Bertels, Schmalz, & Ludwigs, 2009).

Besides this, it is clear that many ADL require a certain degree of flexion or
extension in the wrist, or a certain degree of rotation. For example, it is
described that eating requires 30 degrees flexion/extension and 30 degrees
radial/ulnar deviation (Heckathorne, 2004). For other activities, like driving
in a car, riding a bike, lifting objects, closing a zipper or buttons, or
handling tools, maximally 80 degrees of flexion/extension and 60 degrees of
radial/ulnar deviation is needed (Heckathorne, 2004).

Recently, two prosthetic wrist units that have more motion capabilities than
just rotation were put on the market: the Flex wrist of Otto Bock ® can be
fixed in different flexion/extension modes (-40, -20, 0, 20, 40), while the
Multiflex-wrist of Motion Control ®) can not only be secured in the
flexion/extension direction (-30, 0, 30), but also, in the neutral position (0)
the wrist can move freely in the flexion/extension direction and in the
radial/ulnar direction. Only very limited research has been performed to
establish the value and possible added value of such flexible wrist units
(Bertels, Fiedler, & Schmalz, 2008; Petersen, 2008; Kyberd, 2012). Importantly,
systematic research aiming to determine advantages in prostethic users has not
been performed.

It is expected that wrist units with more degrees of freedom contribute to a
higher experienced functionality and satisfaction with the prosthesis. Also,
movement patterns are expected to be more natural and to reveal less
compensatory movements.

The aim of this study is to explore the value and added value of a wrist unit
that can be put in a flexion position (Flex-wrist, Otto Bock ®) and a wrist
unit that can not only be put in a flexion position but can also move freely in
a neutral position (Multiflex wrist, Motion Control ®) compared to a rigid
wrist unit (Otto Bock ® and Motion Control ®, respectively), using a range of
tests covering all factors of the domains Functional Impairments and Activities
& Participation as described in the International Classification of Functioning
and Health.

The study will be a cross-over study, in which each participant uses two
different wrist components of two different manufacturers for their prostheses.
The period of study for each participant is three months. Each participant uses
two different prosthetic wrists of different manufacturers, in two different
states (passive and flex). After using a prosthetic wrist in a certain state, a
measurement takes place (M1 - M4). One month after completion of the wearing of
the test hands, a follow-up measurement takes place. Before starting the test
period, one measurement (M0) is conducted using the participants* own
prosthesis, to enable the participant to get used to the measurement
procedures, and to be able to check for individual differences between the
participants at baseline. The pre-measurement and interim measurements will
each take maximally 2.5 hours, including all questionnaires, equipping
participants with measurement instruments, appropriate number of breaks, etc.
Actual measurement time will be shorter.

Each participant will follow a test period of two blocks of four weeks (see
Table 1). Within a block a Flex wrist (Otto Bock ®) or a Multiflex-wrist
(Motion Control ®) is used for two weeks. Furthermore, the same hands but with
a rigid wrist unit are used for another two weeks in that same block. Within a
block four participants start with a flexion/extension wrist unit and four
participants start with a rigid wrist unit. Furthermore, four participants
start with the Otto Bock ® hands and four participants start with the Motion
Control ® hands. The exchange between the replacements will take place on one
day. The wrist units are equipped with a Quick-Disconnect system, which enables
to change very easy between the prosthetic hands. Before getting a new wrist
component, each participant is asked to fill out a very short questionnaire
assessing expectations with regard to functionality of the new device, because
registration of the expectations of the user is expected to be important to be
able to refer to, when drawing conclusions with regard to satisfaction.

Measurements start with a general questionnaire and with a short evaluation of
expectations. The other measurements take place within the domains Functional
Impairments and Activities & Participation of the ICF (International
Classification of Functioning and Health). VAS (Visual Analogue Scale) scores
are determined to assess expectations about the new prosthetic wrist, compared
to own prosthesis. During the execution of ADL (Activities of Daily Living)
tasks, movements of the trunk, shoulder and elbow are measured. By measuring
joint angles, compensatory movements from the elbow and shoulder joints that
are necessary in these tasks can be quantified. The pressure inside the socket
of the prosthesis will be measured with pressure sensors. To assess
functionality, the Box and Block test and Southhampton Hand Assessment
Procedure (SHAP) are used. Satisfaction of the patient is measured by
questionnaires, namely TAPES (Trinity Amputation and Prosthesis Experience
Scale) and OPUS (Orthotics and Prosthetics Users* Survey), and VAS scores. A
semi-structured telephonic interview is conducted at the end of the research to
ask the user about experienced advantages and disadvantages of the wrists.

N.A.

Prosthetic hands that are comparable with the own prosthetic hand of the
participant are used. Participants might only suffer from light muscle soreness
the next day due to the execution of the tests. Also, the pressure sensor that
is placed in the socket of the prosthesis can possibly cause light irritation
of the skin. The risks associated with participation in this study can be
considered negligible.