Biomechanical analysis of four supports for the subluxed hemiparetic shoulder.

External support systems, such as slings and lapboards, may reduce shoulder subluxation in individuals with hemiplegia. However there is controversy among occupational therapists concerning the most appropriate method to support the affected arm. The purpose of the present paper is to report the biomechanical analysis of four support systems; two shoulder support systems, a Bobath axillary roll, and a laptray. Two dimensional static biomechanical analyses determine the mechanical characteristics of each of these four support systems. The results of the analyses demonstrate the magnitude of the shoulder loading and the effectiveness of the various components of each of the systems. The effect of changing some of the characteristics of the slings is demonstrated. Slings with straps over the unaffected shoulder provide continuous support for the flaccid extremity. The Bobath axillary roll may introduce an unwanted lateral force. Lapboards must be maintained at an appropriate distance from the subluxed shoulder to be effective. This theoretical analysis of supports systems will provide therapists information to help them understand effective supports for subluxation.