Advantages of flexible wrist units in arm prostheses.

Background:

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. 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).



Recently, two prosthetic wrists 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 patients has not been performed.



It is expected that wrists 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.



Aim:

The aim of this study is to explore the value and added value of a wrist that can be put in a flexion position (Flex-wrist, Otto Bock ®) and a wrist 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.



Study design:

The study will be a cross-over study, in which each patient uses two different wrist components of two different manufacturers for their prostheses. The period of study for each patient is three months. Each patient uses two different wrists. There is a pre-measurement, three interim measurements (at the changing of the wrist and/or hand) and a post-measurement. In addition, one month after completion of the wearing of the test hands a follow-up measurement takes place.



Measurements start with a general questionnaire and with a short evaluation of expectations. VAS (Visual Analogue Scale) scores are determined to assess expectations about functionality of 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. 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.



Population:

The population consists of eight patients with an arm amputation (from University Medical Center Groningen or Revant Rehabilitation Center Breda), either due to ULRD or ULA. In this research project, only patients with a below elbow amputation will be included. The results could potentially also apply to patients with a more proximal amputation level. To be able to estimate compensatory movements while performing the movement tasks, reference values will be gathered from eight healthy subjects of same age and gender.

The aim of this study is to explore the value and added value of a wrist that can be put in a flexion position (Flex-wrist, Otto Bock ®) and a wrist 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.

All parameters listed in 'secondary outcomes' are assesses at baseline, at 2, 4, 6, and 8 weeks (after using a wrist unit during a two-week period). One month after completing the test period of eight weeks, a telephonic interview takes place to ask patients for experienced advantages/disadvantages of the prosthetic wrists.

Eight patients use two different prosthetic wrists, either put in fixed or flexible position. Total duration of the test period is 8 weeks.

Eight healthy participants are used to gather reference values of movement trajectories of several activities of daily living.