Background Patients with Ehlers Danlos(hypermobility type)(EDS-HT) are characterized by connective tissue laxity which is associated with joint pain and muscle weakness, potentially leading to activity impairment. An important goal during rehabilitation is to reduce activity limitations by increasing muscle strength. However, evidence supporting this rationale is scarce. Muscle strength might be an important determinant of activity limitations; still, the relationship between muscle strength and activity limitations remains unknown. This association might be influenced by other factors, like proprioception. Recent studies have established that proprioception is reduced in patients with EDS-HT, still no studies have investigated its influence on activity impairment as its importance for muscle strength.
Objectives To establish the association between muscle strength and activity impairments controlled for proprioception in patients with EDS-HT.
Methods 25 patients with EDS-HT, were compared to 25 controls. Activity impairments (dependend variable) were quantified according to the Health Assessment Questionaire(HAQ), Six Minute Walktest(6MWT) and chair rise test(CRT). Muscle strength (Handheld dynamometry) and (knee)proprioception(movement detection) were used as independent variables. Pain(Visual Analog Scale), fatigue(Checklist Individual Strength) and demographics(age, BMI) were inserted as confounders. Inter-variable associations were established by Pearson coefficients. Consecutively multivariate models were constructed, for each dependent variable, by Generalized Equation Estimates(GEE).
Results Univariate analysis showed significant associations between all measures of activity impairments and muscle strength (HAQ: r=-.557, p=<.0001, 6MWT: r=.557, p=<.0001, CRT: r=.664 p=<.0001), proprioception (HAQ: r=-.456, p=.001, 6MWT: r=-.400, p=.004, CRT: r=-.552 p=<.0001) and between muscle strength and proprioception (r=-.488, p=<.0001). Multivariate analysis revealed associations between muscle strength and CRT (B:.334(.13), p=.007), 6MWT (B:.366(.03), p=<.0001) and HAQ (B: -.267(.04), p=<.0001). Indicating that muscle weakness is associated with activity impairments. Proprioception was associated with activity impairment but only when quantified by CRT (B: -.381(.14), p=.005). Interaction effects were found between muscle strength and proprioception which contributed independently to activity impairment (CRT: B: -.175(.06), p=.006, HAQ: B:-.144(.05), p=.002).
Conclusions Muscle strength is an important factor related to activity impairments in patients with EDS-HT. Activities that require more motor control, such as transfers, are more dependent on proprioceptive information. However, with regard to functional ability, controlling muscle force seems to be dependent on the amount of proprioceptive information available rather than being the product of only muscle power.
References Rombaut L, De Paepe A, Malfait F et al. Joint position sense and vibratory perception sense in patients with Ehlers-Danlos syndrome type III. Clin Rheum. 2010;29(3):289-95.
Rombaut L, Malfait F, De Wandele I et al. Muscle mass, muscle strength, functional performance, and physical impairment in women with the hypermobility type of Ehlers-Danlos syndrome. Arth Care Res. 2012;64(10):1584-92.
Disclosure of Interest None Declared