Orthoses and other assistive devices regularly play an important role in conservative treatment of neurological disorders. For example, up to 85% of children with cerebral palsy (CP) use at least one orthotic device, with nighttime ankle-foot orthoses (AFOs), at 43.6%, being the most common. The need to wear such a device is a consequence of the associated foot deformities and pathological gait patterns in 93% of these individuals. Beyond the isolated example of CP, AFOs are the devices most commonly used in patients with underlying neurological disorders in general. In the basic indication for orthoses, a distinction can be made between preventive and functional-supportive therapeutic goals. Ankle-foot orthoses basically aim to support foot structure and to correct or at least stabilize deformities, avoiding further deterioration. Positive effects on walking speed, stride length, cadence, oxygen consumption, and kinematics of the ankle, knee, and hip joint have been reported. Positive effects like an improvement in spatiotemporal parameters, general walking ability, and gait quality due to orthoses were also described in addition to surgical interventions.

Depending on the level of involvement and the severity of motor impairment, for example, as measured by the Gross Motor Function Classification System (GMFCS), a higher level of support may be provided by knee-ankle-foot orthoses (KAFOs). Crossing the knee joint heightens the anatomical level of the lower limb and embeds another essential joint of the lower-limb functional chain into the orthotic fence and thus increases the support of the lower limb by providing additional stabilization and guidance.

Different manufacturing techniques make it possible to combine the aforementioned designs in a modular way, such that the properties or the degree of support of an orthotic device can be dynamically adapted to changes in individual requirements of daily living but also during the course of the rehabilitation process.

The use of orthoses in particular is a critical aspect. Derived from the clinical experience of the authors, medical health professionals are uncertain about the extent to which the orthoses are worn during activities of daily living. In general, relatively little is known about factors influencing adherence to therapy and in particular about wearing times for orthopedic aids. The influence of age, severity of disease, degree of disability, and benefit or positive evaluation of assistive devices has been described in different indications. Detailed investigations in which therapists analyzed the actual wearing time of orthopedic aids concerned corsets in idiopathic scoliosis therapy. Different research methods such as temperature or force transducers and surveys14 were used to address this particular question. It could be demonstrated that compliance regarding wearing time was between 27% and 47% and decreased with a higher recommended daily use. However, study results also demonstrated, using the example of scoliosis, that there is a clear negative correlation between the time in brace and the likelihood of surgery. Unfortunately, our knowledge about therapy adherence for lower-limb orthoses is only rudimentary. It is believed, however, that the clinical benefit of orthosis therapy depends significantly on the wearing time too. Maas et al. described temperature sensor-based wearing times of KAFOs that deviated significantly from information received from the parents of the users. Compared with AFOs, though, KAFOs account for only a very small proportion (0.7%) of the total of all assistive devices. Recently, Schwarze et al. reported in a descriptive analysis of a small cohort of patients with CP that there might be differences in wearing time between different modular components of an orthosis. Furthermore, differences between weekdays and weekends were found.

To the best of our knowledge, further information about the acceptance and the wearing time of lower-limb orthoses is not available. However, this information represents a fundamental prerequisite for studying and discussing the effects of such aids. It can be assumed that adherence to therapy essentially depends on the design of the orthoses (modularity, embedded anatomical level of the lower limb [described below as "anatomic height"], etc.). The aim of this study was therefore to evaluate the wearing time of lower-limb orthoses depending on the design (modular vs. nonmodular) and anatomic height. Furthermore, it is not known how secondary factors such as daily routines influence therapy adherence. In particular, it is of interest whether there is a difference between the wearing time on weekdays and the weekends because it can be assumed that the level of activity, individual requirements, and also peer influences differ.

We hypothesized that the daily wearing time (1) depends on modularity and (2) differs between weekdays and weekends. Furthermore, we hypothesized that (3) anatomic height influences the daily wearing time as well.