Sternal micromotion following cardiac surgery via a median sternotomy: A 3-month prospective, observational study

Abstract

Introduction: The median sternotomy remains the most commonly used incision for cardiac surgery. A small, but significant proportion of patients develop postoperative sternal complications. In an attempt to prevent these complications, patientsworldwide are routinely prescribed sternal precautions that restrict upper limb and trunk movements. However, there is no evidence to support sternal precautions, with current recommendations drawn from cadaver/model studies. To date, the effects of upper limb and trunk use on sternal micromotion and healing remain unknown. The objective of this study was to measure the sternal micromotion that occurs during dynamic tasks involving the upper limbs and trunk using ultrasound. The reliability of ultrasound as an assessment tool was also determined. Methods: Seventy-five patients following cardiac surgery were recruited to a prospective, observational study. Sternal micromotion (vertical and horizontal directions) was measured in vivo using ultrasound, at rest and during five dynamic tasks (deep inspiration, cough, unilateral and bilateral upper limb elevation, and sit to stand) at three postoperative time points (T1:3-5 days, T2:6 weeks and T3:3 months), using the device proprietary software. Results: There was a significant decrease in both the separation of the sternal edges in the vertical direction (T1-T3:0.011 cm mean decrease) and overlap of the sternal edges in the horizontal direction (T1-T3:0.008 cm mean decrease) over time. This correlated with a decrease in sternal pain and an increase in postoperative function over time. Cough produced a significant increase in sternal pain and micromotion in the horizontal direction, compared to other tasks (0.014-0.016 cm mean increase in separation of the sternal edges). Five participants demonstrated sternal union on ultrasound at T3, at rest and during the dynamic tasks assessed. The intra and inter-observer reliability of the mean ultrasound measures for all tasks ranged from ICC (3,1) 0.990-0.997 and ICC (2,1) 0.994-0.998, respectively. Discussion: This study quantified the resultant sternal micromotion during dynamic tasks, in two planes. The results suggest that sternal precautionsmay be overly restrictive and not warranted in all patients. The low incidence of pulmonary complications may support caution with coughing as a routine intervention as this task resulted in the most sternal pain and micromotion. Patient-specific sternal care that focusses onmovement within comfort, and function that is informed by the assessment of risk for sternal complications may be more appropriate to facilitate recovery. Further investigation of the factors that affect sternal healing is warranted.