Abstract

Background: Cardiac surgery performed by median sternotomy provides optimal access to the heart and mediastinum and is associated with excellent outcomes globally. However, sternal complications including sternal instability present a burden on the patient and the healthcare system in a small but significant number of patients globally. The aim of this study was to investigate the validity and reliability of the Sternal Instability Scale (SIS) as an outcome measure for the diagnosis, screening and monitoring of sternal instability.
Methods: Blinded, randomized within-participant experimental study with 8 assessors rating participants (n=60) when blind to sternal instability diagnosis by Ultrasound. The Sternal Instability Scale (SIS), a 4-point manual test was utilized to grade sternum stability from 0 (stable sternum with no detectable motion) to 3 (completely separated sternum with marked increase in motion of the sternal edges).
Findings: Validity: patients diagnosed with sternal instability were rated higher on the SIS with a significant mean difference of 2.35 SIS grade points over those not diagnosed. The inter-rater reliability for all 8 assessors over the two occasions of testing 60 patients yielded an ICC (2, 1) mean value of 0.88. Intra-rater reliability estimates for manual sternal assessment in the patient group gave ICC (2, 1) values between 0.92 and 0.99.
Conclusions: The SIS is a noninvasive, feasible, physical assessment tool that can be administered reliably by medical and health professionals following a median sternotomy. Manual assessment of the sternum promotes the early detection of sternal instability to enable optimal and timely management, better monitoring of patients with sternal instability throughout their postoperative recovery, as well as providing an objective platform for the development of individualized guidelines for activity, exercise and rehabilitation.