Reaching higher: External scapula assistance can improve upper limb function in humans with irreversible scapula alata

Abstract

Background: Scapular dyskinesis, i.e., the deviant mobility or function of the scapula, hampers upper limb function in daily life. A typical sign of scapular dyskinesis is a scapula alata—a protrusion of the shoulder blade during arm elevation. While some reversible causes of scapula alata can be treated with therapy, other, irreversible causes require invasive surgical interventions. When surgery is not an option, however, severe limitations arise as standard approaches for assisting the scapula in daily life do not exist. The aim of this study was to quantify functional improvements when external, i.e., non-invasive, scapula assistance is provided. Methods: The study was designed as a randomized controlled crossover trial. Eight participants with a scapula alata due to muscular dystrophy performed arm elevations in shoulder flexion and abduction while unassisted (baseline), externally assisted by a trained therapist, and externally assisted by a novel, textile-based scapula orthosis. Results: With therapist assistance, average arm elevation increased by 17.3° in flexion (p < 0.001, 95% confidence interval of the mean CI95%=[9.8∘,24.9∘]), and by 11.2° in abduction (p < 0.01, CI95 %= [ 4. 7 ∘, 17. 7 ∘] ), constituting the potential of external scapula assistance. With orthosis assistance, average arm elevation increased by 6.2° in flexion (CI95 %= [ 0. 4 ∘, 11. 9 ∘] ) and by 5.8° in abduction (CI95 %= [ 3. 0 ∘, 8. 5 ∘] ). Remarkably, in three participants, the orthosis was at least as effective as the therapist. Moreover, orthosis assistance reduced average perceived exertion by 1.25 points (Borg Scale) when elevating a filled bottle during a simulated daily living task. Conclusion: These findings indicate a large potential for future advancements in orthotics. Already now, the textile-based scapula orthosis presented here is a feasible tool for leveraging the benefits of external scapula assistance when a therapist is unavailable, as encountered in daily life scenarios. Trial Registration ClincalTrials.gov (ID NCT04154098). Registered: November 6th 2019, https://clinicaltrials.gov/ct2/show/NCT04154098?term=scapula+orthosis&draw=2&rank=1 Graphic abstract: [Figure not available: see fulltext.]