Clima

As identified in the preceding section, task complexity presented

significant challenges to reliable 3D-ULMA kinematic measurement. The lack of a cyclical nature in upper limb function complicates the assessment of reliability of a measurement tool as the inherent variability of task

performance can result in unreliable findings. The motivation for this research was to enhance the clinical service provision for children with OBPP. In recognition of the importance of efficient functional ability, the tasks chosen for analysis were based on a valid and reliable clinical measure routinely used to assess functional performance in children with OBPP. The six tasks of the modified Mallet scale (Abzug et al., 2010) are divided into three gross movements and three functional tasks. No task demonstrated consistent reliability across all joints and rotation axes. This highlighted that no one task, from simple to complex, can provide reliable data on all joint kinematics of the upper limb in children with OBPP. The following paragraphs identify the salient points from the overall reliability of

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these tasks and where possible, compare with existing findings in the literature.

The Abduction Task was the simplest to measure as the main movement occurred in one plane, the scapular plane (TH POE 45⁰(±24⁰)). Analysis of planar movements has been found to be easier and more reliable than the more complex, combined movement patterns typical of upper limb function (Lempereur et al., 2012, Vanezis et al., 2015). The acceptable reliability of this task was similar to previous research where a comparable task, reach sideways, was analysed in TDC and children with HCP (Jaspers et al., 2011b, Jaspers et al., 2011c). These studies reported similarly high ICCs of >0.75 with SEMs of 3⁰ to 9⁰ in nearly all rotation axes with the exception of poor reliability in ST A/P tilt in children with HCP and ST M/L rotation in TDC.

No studies in the literature assessed tasks similar to the pure External and Internal Rotation Tasks examined in this study. The principal movement of these tasks should be in the plane of GH AR. While neither task is complex to perform per se, active rotation is a recognised challenge for all children with OBPP with a lack of external rotation a characteristic feature of all levels of the NC (Hale et al., 2010, Breton et al., 2012, Heise et al., 2015). The External Rotation Task was the least reliable task; two variables demonstrating acceptable reliability, GH elevation and ST M/L rotation at PTA. This may reflect compensatory strategies adopted in the absence of pure active GH external rotation. The Internal Rotation Task had somewhat better reliability in the TH/GH joints. Acceptable reliability was found in TH/GH POE/elevation at PTA and GH AR (ROM). No ST joint rotation axis achieved acceptable reliability limits in the Internal Rotation Task.

As both tasks were performed in the same session this suggests that the variable reliability cannot be solely due to replacement of the markers or axis definition error. It questions the ability of the model to reliably track the External Rotation Task. An alternative position than arm by the side, as used in the modified Mallet scale, may be appropriate as this position is

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associated with the mathematical problem of gimbal lock due to two axes being aligned in the same orientation (Rundquist et al., 2003, Šenk and Chèze, 2006, Jaspers et al., 2011c). Furthermore, the chosen reliability coefficient may have influenced results. As the ICC is dependent on the variation in task performance amongst participants, a lower ICC may have been generated due to the poor functional ability of participants during the External Rotation Task, in contrast with the better ability to complete the Internal Rotation Task during the sessions.

Of the three functional tasks, Hand-to-Neck had the poorest reliability. As previously discussed (Section 4.8.3.1) this task was the most complex. It is difficult to achieve in the presence of limited elevation and external rotation, both of which are limited in children with OBPP. No task was comparable in the existing literature. Different strategies were observed in the participants with OBPP as they attempted to complete the task, with frustration noted in some children. This may have influenced inherent reliability of task performance with different strategies being adopted to better achieve the task in each trial. The two other functional tasks, Hand- to-Spine and Hand-to-Mouth which are less complex, had better, but still varied levels of reliability with the TH/GH joints at PTA the most

consistently reliable variables. Reliability of gross movements within functional tasks e.g. TH elevation, was greater than those less defined for task completion e.g. elbow supination, ST motion. This concurred with the conclusion by Vanezis et al. (2015) that the gross movement of TH

elevation was more reliable than the more refined motions of elbow P/S in which higher errors were observed.

Elbow joint kinematic data were only evaluated in the functional tasks as it was considered crucial to their successful completion. Only one variable, elbow F/E (ROM) in the Hand-to-Mouth Task (ICC 0.77; SEM 8.3⁰)

achieved acceptable reliability. Altered head and trunk positon in addition to variability in task performance may have influenced the degree of elbow F/E required. They are not reported in this research. Elbow P/S had consistently poor reliability in this study. Contrasting results were found for the Hand-to-Mouth Task in previous studies with acceptable reliability

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found for both rotation axes in TDC (Jaspers et al., 2011c) and for elbow F/E in children with HCP (Jaspers et al., 2011b). In this research, for the Hand-to-Spine and Hand-to-Neck Tasks marker view of forearm cluster was a problem which contributed to poor reliability. Increasing the number of cameras used is recommended for future studies to enhance marker visibility.

These findings highlighted the challenges in selecting appropriate tasks for examination both due to: limitations of the model in tracking planar and combined movements; the impact of the particular population’s

impairments on task performance. The modified Mallet scale was chosen as it is routinely used in clinical practice and the objective was to inform clinical management of this cohort. However, it was evident from these results that the poor reliability of the tasks negates the benefits of using a recognised clinical scale. Careful selection of tasks based on the clinical questions but recognising limitations of the model is crucial. Based on the results of this research the Abduction Task was the only one that achieved an acceptable level of reliability across all joints while the Internal

Rotation, Hand-to-Mouth and Hand-to-Spine Tasks achieved acceptable reliability in at least two of the TH/GH joint rotation axes. Further work on the dynamic tracking of the upper limb during functional activities in this cohort is required prior to clinical application.