Postural control in upper limb functional tasks during standing

This thesis is based on a project aimed at validating an innovative therapy for the treatment of upper limb lymphedema. Lymphedema is a debilitating disease with a slow and progressive course that may result in a loss of quality of life if appropriate therapy is not initiated early. Breast cancer is the most common cause of upper limb lymphedema. Increased arm volume can lead to gait and balance problems as a result of changes in postural control strategies. The objective of this thesis is to study postural control in upper limb functional tasks during standing by analyzing the Center of Pressure (CoP) signal. A group of 11 healthy women and 2 patients with lymphedema participated in this study and were asked to perform a series of tasks in an environment equipped with an optoelectronic system and a force platform. We analyzed balance maintenance during bilateral stance with open-eyes and closed-eyes, unilateral stance and several upper limb functional tasks. Since several repetitions were performed for each task, an algorithm was developed to analyze the movement of the markers placed on the participant's body in order to identify the start and end moments of the movement. In this way, the intervals of interest for the CoP analysis were found. The main parameters extracted from the CoP signal are the position parameters such as the oscillation ranges in the medio-lateral and antero-posterior direction, the confidence ellipse at 95%, the shift of the mean CoP with respect to an axis of symmetry and the dynamic parameters such as the sway path and the sway area. Some exercises proved to be more effective in evaluating a different postural control strategy between control group and patients with lymphedema: unilateral stance, frontal reaching and lateral reaching. In addition, the sway path parameter proved to be the most effective in discriminating between performing the exercise with eyes open and eyes closed. For lymphedema patients, worsening of proprioception may be a possible consequence of cancer treatment, so the proposed analysis may be useful in evaluating the effects of the therapy. In the future, a larger sample size is needed to validate our conclusions. Regarding the structure of this thesis, Chapter 1 explains in detail what lymphedema is and what treatments are conventionally performed. Furthermore, the methods reported in the literature to evaluate postural control starting from the CoP signal are presented. Subsequently, Chapter 2 describes the participants, the equipment used, the protocol to acquire the signals of interest and the data analysis algorithm. The latter is divided into two parts, analyzing the data coming from the optoelectronic system and the force platform, respectively. Chapter 3 reports the results obtained, Chapter 4 gives a discussion, and, finally, Chapter 5 summarizes the conclusions of this study.