Effects of Upper Extremity Movements on Sternal Skin Stress

Abstract

Purpose: Sternal precautions given to patients following median sternotomy are based on expert opinion. Although specific limits are often stated within different versions of sternal precautions, no evidence exists to support any specific cut-off values. The purpose is to determine whether evidence exists for lifting restrictions and transfer methods given as sternal precautions. Methods: 22 healthy subjects (18 female, 4 male), ages 40-69 (mean 53) were instrumented with a Doppler blood flow probe to measure acceleration of skin overlying the sternum. Participants performed 3 trials each of 4 lifting tasks (arm only, 12-ounce can, 1-liter bottle and gallon jug from countertop to shelf). Sit-to-stand and supine-to-sit were each performed two different ways. Sternal skin stress was recorded while subjects performed transfer techniques taught by therapists to minimize upper extremity use and when using transfers that allow pushing up on the hands. Doppler shift caused by skin acceleration was recorded during each procedure. Results: Sternal skin stress during each lifting task was significantly different from all others (p < 0.001, repeated measures ANOVA, Tukey post-hoc tests). Sternal skin stress during transfers as taught by therapists was significantly less than that recorded during typical patient-selected transfer technique (paired t-tests, p = .007 for sit-to-stand and p = 0.015 for supine-to-sit). Conclusions: Lifting heavier objects causes more sternal skin stress than lighter objects. Transfer techniques taught as sternal precautions cause less sternal skin stress than commonly used transfer techniques. Although sternal precautions may be based on real differences in sternal skin stress within subjects during movements involving the upper extremities, the large variation among subjects in sternal skin stress suggests that no clear cut off for activities can be supported.