The association between muscle weakness and activity limitations in patients with Ehlers Danlos (Hypermobility Type): the impact of proprioception

s / Osteoarthritis and Cartilage 22 (2014) S57–S489 S201 Conclusions: These results show that illness perceptions are associated with disability cross-sectionally and also after short-term follow-up. Dimensions of illness perceptions that are of importance cross-sectionally are not the same as those that are associated with disability longitudinally. These results may imply that biopsychosocial interventions aiming at changing negative illness perceptions can contribute to better functional, psychological and social outcome. As such interventions produce positive effects on important outcome measures in patients with various chronic illnesses, psychological interventions in patients with hand OA are urgently called for. 349 THE ASSOCIATION BETWEEN MUSCLE WEAKNESS AND ACTIVITY LIMITATIONS IN PATIENTS WITH EHLERS DANLOS (HYPERMOBILITY TYPE): THE IMPACT OF PROPRIOCEPTION M.C. Scheper yz. yUniv. of Applied Sci.s Amsterdam, Education for Physical Therapy, Amsterdam, Netherlands; zAcademic Med. Ctr., Dept. of rehabilitation, Amsterdam, Netherlands Purpose: Patients diagnosed with Ehlers Danlos Syndrome Hypermobility Type (EDS-HT) are characterized by connective tissue laxity which is associated with chronic pain, fatigue, muscle weakness and potentially leading to activity limitations. When developing effective treatment for patients with EDS-HT it is essential to knowwhich factors are associated with activity limitations. In EDS-HT, a direct relationship between muscle strength and activity limitations has never been studied in detail. The association between limitations in activities and muscle strength might be moderated by other biomechanical factors, like proprioception. Recent studies have established that proprioception is reduced in patients with EDS-HT still no studies are available at this time which have investigated the impact of proprioception on the association between muscle strength and activity limitations in patients with EDS-HT. Therefore, the objective of the study was to establish the association between muscle strength and activity limitations and the impact of proprioception of the knee joint on this association in patients with EDS-HT. Methods: 25 subjects with EDS-HT were compared with 24 healthy controls. Activity limitations, both performance and capacity qualifiers, were quantified according to the Health Assessment Questionnaire (HAQ), the Six-Minute Walk test (6MWT) and the 30-second chair-rise test (30CRT). Muscle weakness was measured by handheld dynamometry (normalised over fat-free mass) and (knee) proprioception was measured by movement detection paradigm. Pain was measuredwith an Visual Analogue Scale, fatigue by the Checklist Individual Strength and subject demographics (age, BMI, disease duration) were questioned. Statistical analyses were performed in three stages. First, descriptions of the subjects and the measures of central tendency were calculated. All outcomes were transformed into z-scores in order to aid in meaningful interpretability. Healthy controls were used within statistical analyses as a contrast group in terms of disease severity as to the divergence from normality. Secondly, differences between groups were determined by independent Student t-test. Thirdly, the association between dependent and independent variables were performed, in order to determine the inter-variable relationship and to identify potential confounding factors. All significant factors were retained for multivariate analyses. In the final stage, the association of muscle strength with activity limitations was established, controlled for the moderation by proprioception, pain and fatigue and other potential confounders (age, BMI, disease duration). For each outcome of activity limitations, a two level (subjects and controls) mixed linear model was constructed in which activity limitations was the dependent variable and muscle strength and proprioception independent variables. This association was adjusted for the potential confounders: age, BMI, disease duration. In the adjusted model all independent variables were entered and consecutively a backward selection was applied in order to establish the final model. The independent factors were retained by default, whereas confounders and interaction effects were retained in the final model when a p-value of<.200 was present and the deletion of a variable resulted in a reduction of the Tsai-Hutch Criterion (AICC: Goodness of Fit). Results of the mixed linear models were presented in regression coefficients and corresponding standard errors (B(SE)) with 95% confidence intervals (95%CI). Results: Subjects with EDS-HT showed a higher degree of activity limitations, more pain and fatigue, muscle weakness and proprioceptive inaccuracy compared to the healthy controls (p < 0.05). Muscle weakness was correlated with lower scores on the 30CRT (r 1⁄4 .669, p < .0001), the 6MWT (r 1⁄4 .577, p 1⁄4 <.0001) and higher scores on the HAQ (r 1⁄4 .626, p 1⁄4 <.0001). Proprioceptive inaccuracy was associated with lower scores on the 30CRT (r 1⁄4 .552, p < .0001), the 6MWT (r 1⁄4 .400, p 1⁄4 .001) and higher scores on the HAQ (r 1⁄4 .456, p 1⁄4 .001). Muscle weakness was found to be the largest contributor to the variance in activity limitations. Proprioceptive inaccuracy, pain and fatigue had an impact on the association between muscle strength and activity limitations (p < .05). Conclusion: Muscle weakness was associated with an increase in activity limitations in subjects with EDS-HT. This association was moderated by joint proprioception, and should be recognised as an important factor when developing new treatment modalities which aim to reduce activity limitations.