A novel clinically practical upper limb model is introduced that has been developed through clinical use in children and adults with neurological conditions to guide surgery to the elbow and wrist. This model has a minimal marker set, minimal virtual markers, and no functional joint centres to minimise the demands on the patient and duration of data collection. The model calculates forearm supination independently from the humerus segment, eliminating any errors introduced by poor modelling of the shoulder joint centre. Supination is calculated by defining the forearm segment twice, from the distal and proximal ends: first, using the ulna and radial wrist markers as a segment defining line and second using the medial and lateral elbow markers as a segment defining line. This is comparable to the clinical measurement of supination utilising a goniometer and enables a reduced marker set, with only the elbow, wrist, and hand markers to be applied when only the wrist and forearm angles are of interest. A sensitivity analysis of the calculated elbow flexion-extension angles to the position of the glenohumeral joint centre is performed on one healthy female subject, aged 20 years, during elbow flexion and a forward reaching task. A comparison of the supination angles calculated utilising the novel technique compared to the rotation between the humeral and forearm segments is also given. All angles are compared to a published kinematic model that follows the recommendations of the International Society of Biomechanics.

Purpose: Dyssynergic defecation is a common functional defecation disorder in children with four known types. Compared to adults, paediatric dyssynergic defecation is not as well characterised. We sought to better define patients with Type I and II paediatric dyssynergia as this may facilitate future management strategies. Methods: The demographic profile, detailed medical history and treatments were obtained from 26 patients diagnosed with Type I and II dyssynergic defecation at the Evelina London Children’s Hospital from April 2019 to November 2021. Results: Twenty patients were diagnosed with Type I dyssynergia (average age 9.9 years, standard deviation (SD) of 2.6). Six patients were diagnosed with Type II dyssynergia (average age 10.8 years, SD of 3.7). The major subset of the patient cohort had significant gastrointestinal symptoms including 20 (77%) experiencing soiling and 19 (73%) displaying withholding. Many patients had a number of comorbidities (including respiratory, neurological and genitourinary). There were also notable psychological, social and developmental conditions (73%) including anxiety, autism and cerebral palsy. 22 patients were taking at least one laxative as treatment. 21 of the 26 patients required disimpaction treatment. None of these patients required surgical intervention. Conclusions: Our results show that a high proportion of patients with dyssynergic defecation have significant psychosocial conditions. This may contribute to the development and progression of this condition by shaping the cognitive schemas which lead to voluntary withholding. Management of these patients should therefore include a comprehensive psychosocial assessment in addition to managing the symptoms of defective defecation.

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