Biomechanical influences of shoulder disarticulation prosthesis during standing and level walking

Abstract

BACKGROUND: Modern prosthetic systems with more degrees of freedom offer the patient clearly improved functions. However, the influence of functional arm prostheses on body posture and gait have never been quantified. OBJECTIVES: The purpose of this investigation was to observe the impact of a functional arm prosthesis on body posture and gait of shoulder disarticulation patients. STUDY DESIGN: Experimental, biomechanical. METHODS: Eight patients with unilateral shoulder disarticulation were enrolled. Static posture and gait analyses were conducted with and without using a functional arm prosthesis. Static posture analysis using the L.A.S.A.R. Posture device as well as kinematic and kinetic gait analysis using an optoelectronic camera system combined with force plates were conducted with and without prosthesis in eight unilateral shoulder disarticulation patients. RESULTS: Static analysis confirmed that an arm prosthesis improves body posture of amputees. Gait analysis revealed that compensatory movements during walking as well as external knee moments on the prosthetic side leg are significantly reduced when using a free swinging shoulder joint. CONCLUSIONS: An arm prosthesis does not only offer functional and cosmetic benefits. The results confirm that unilateral shoulder disarticulation patients benefit from a functional arm prosthesis with a free swinging shoulder joint in terms of optimized posture and gait dynamics. CLINICAL RELEVANCE: This study demonstrates that shoulder disarticulation patients benefit from a functional prosthesis with a free swinging shoulder joint. Such prosthesis significantly improves body posture and gait characteristics, reduces compensatory movements and relieves distress to the musculoskeletal system. This should be considered when prescribing a prosthesis for shoulder disarticulation amputees.