Objective: The study proposes a method to obtain anatomically- and functionally-personalised orthotics for the dynamic postural control of the upper limb.

Background: The orthotic treatment of secondary dystonia and dyskinesia is not well characterised in the literature. Some studies suggest that limiting the range of motion of some joints in the limb kinematic chain may improve overall functional performance. Personalisation of the orthosis action seems essential in order to prevent excessive constraint, hypertone and guarantee comfort, but the necessary biometric and functional assessment of the patients is often prevented by the involuntary motion caused by Movement Disorders (MD).

Methods: Five children (12.2±5.6 years old) with MD pictures comprising secondary dystonia and dyskinesia took part in the study. As conventional laser-scanning methods and direct moulding are difficult to use for patients with MD, due to the continual involuntary body motion, we developed a topologically structured 105-maker set-up and employed optoelectronic photogrammetry as a means to acquire upper-limb and chest wall geometry. One timeframe (0.017 ms) is sufficient to obtain the required data. Incidentally, arm kinematics is available to identify the most affected arm degrees of freedom. The marker point cloud was converted into a meshed geometry, and a positive model of the limb was obtained by milling, upon which the thermoplastic orthosis shells were shaped. Personalised fixtures were 3D-printed to hold nonlinear springs of Ni-Ti alloy, which provide a mild patient-specific dynamic joint constraint.

Results: The method is robust. The digital and physical arm models reproduce the main features of the limb and are smooth enough to allow orthosis shell moulding without any need for manual correction. The personalised fixtures and alloy characteristics endow the device with a patient-specific dynamic action (spring force and direction). Patients found the orthoses comfortable and were wearing them in excess of 6 hours a day for a month.

Conclusions: The method was found to be very useful to build personalised orthotic devices for children with extreme involuntary movements. The all-in-one-frame capture of limb surface and the orthosis processing that can be carried out almost without involving the patient, make this technique very acceptable and more time-efficient for children with dystonia or dyskinesia.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/design-and-personalisation-of-new-upper-limb-dynamic-orthoses-for-dystonia-and-dyskinesia/