الفهرس 
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Abstract
The study was done on 20 patients undergoing open heart surgery in the Cardiothoracic Surgery Department, Alexandria Main University Hospital. The age of the participants
ranged from 28 to 77 years old with an average of 53. Seven patients were excluded from this study, of whom 5 were due to mortality and 2 were due to non-compliance with follow up. Of the 20 patients, only 4 patients were females. Preoperative risk factors were taken into consideration where 30 % of patients were diabetic, 55 % had chronic obstructive pulmonary disease (COPD) and the average body mass index in this study was 29.4 with a standard deviation of 2.4. Most of the operations done were CABG (55%) where all LIMAs harvested were skeletonized. There was only one redo sternotomy included amongst other sternotomies. The mean operative time (in minutes) was 350.7 minutes ± 58.1. Three patients (15%) were re-explored due to post operative bleeding in the first 24 hours. Clinical examinations were done, and ultrasound measurements were taken on day 2 postoperatively in different situations, namely bilateral limb elevations, inspiration, expiration and sagittal views with a mean of 3 mm ± 2.7 mm, 2.3 mm ± 1.8 mm, 1.7 mm ± 1.7 mm &1mm ± 1.3 mm respectively. Five patients (25%) showed sternal instability on the sixth week postoperatively in which 4 of them had deep infections, where infections subsided with Vacuum assisted wound closure and antibiotic treatments according to culture and sensitivity. One patient out of the five patients had sternal instability on day 2 post operatively, rewiring was done yet the patient developed deep sternal infection with mediastinitis, and sternal instability detected at 6 weeks. (Tables 1-4)
Table (1): Categorical variables
No. (%)
Female 4 (20)
DM 6 (30)
COPD 11 (55)
LIMA 11 (45)
Re-do 1 (5)
Lateralization 4 (20)
Robiscek 4 (20)
Re-exploration 3 (15)
Instability (2nd day) 1 (5)
Instability (6 weeks) 5 (25)
Superficial infection 1 (5)
Deep infection 4 (20)
Table (2): Continuous variables
Range Mean +/- SD Median
Age (years) 28 – 77 53.7 +/- 13.4 56.5
BMI 23.8 – 33.2 29.4 +/- 2.4 30
Operative time (min.) 220 – 453 350.7 +/- 58.1 342
Mechanical ventilation time (h) 0.8 – 6.1 3 +/- 1.5 3.1
VAS day 2 4 – 8 5.8 +/- 1 6
VAS week 6 0 – 8 2.25 +/- 2 2
Table (3): Operations
No. (%)
CABG 11 (55)
MVR 4 (20)
AVR 3 (15)
DVR 1 (5)
CABG + MVR 1 (5)
Table (4): Ultrasound measurements
Range Mean +/- SD Median 25th percentile 75th percentile
Limb elevation (mm) 0.8 - 13 3 +/- 2.7 2 1.6 3.4
Inspiration (mm) 0.8 – 8 2.3 +/- 1.8 1.7 1.3 2.5
Expiration (mm) 0.6 – 8 1.7 +/- 1.7 1 0.9 2.1
Sagittal (mm) 0 - 5 1 +/- 1.3 0.5 0.2 1
A paired T test was done to measure the differences among the different conditions of sternal ultrasonographic measurements, where the differences were taken between the inspiration & expiration, inspiration & limb elevations, and expiration & limb elevation. The P values were statistically significant in the 3 pairs. (Table 5)
Table (5): Paired differences of ultrasound measurements
Mean Std. Deviation Std. Error Mean 95% Confidence Interval of the Difference p
Lower Upper
Pair 1 Expiration -
Inspiration -0.58 0.62 0.138 -0.863 -0.287 <0.001
Pair 2 Expiration - Limb elevation -1.25 1.12 0.251 -1.771 -0.719 <0.001
Pair 3 Inspiration - Limb elevation -0.67 1.1 0.245 -1.183 -0.158 0.007
The effect of lateralization (20% of all cases) was measured against the centralized cases where the difference in ultrasound measurements was also statistically significant. (Table 6)
Table (6): Effects of lateralization
Lateralized Centralized P
Expiration (mm) 3.20 +/- 3.35 1.36 +/- 0.81 0.024
Limb elevation (mm) 5.85 +/- 5.23 2.26 +/- 1.08 0.007
Inspiration (mm) 4.38 +/- 3.14 1.79 +/- 0.8 0.003
Sagittal (mm) 2.35 +/- 1.94 0.62 +/- 0.82 0.005
On the sixth week postoperatively, it was found that 5 patients out of the 20 (25%) had sternal instability. There was a statistically significant difference in ultrasound measurements when comparing the stable and unstable patients (Figure 8). High BMI, LIMA harvest, and deep infections seemed to be consistent with instability which was even seen by ultrasonography (Figures 9 & 10). On the other hand, age, operative time, and mechanical ventilation time did not have any statistical impact. (Table 7 & 8)
Figure (8): Ultrasound measurements
Figure (9): Ultrasound image showing separated sternal edges consistent with sternal instability.
Figure (10): Ultrasound image of a stable sternum.
Table (7): Univariable analysis for sternal instability at 6 weeks (continuous variables)
Unstable Stable P
Expiration 3.88 +/- 2.33 1.01 +/- 0.36 <0.001
Limb elevation 6.42 +/- 3.83 1.83 +/- 0.46 <0.001
Inspiration 4.7 +/- 2.26 1.51 +/- 0.36 <0.001
Sagittal 1.7 +/- 1.53 0.39 +/- 0.34 <0.001
Age 55.8 +/- 8.9 52.9 +/- 14.8 0.345
BMI 31.1 +/- 0.9 28.8 +/- 2.5 0.035
Operative time 367.4 +/- 54.8 345.1 +/- 60 0.237
Mechanical ventilation time 3.9 +/- 1 2.8 +/- 1.6 0.085
Table (8): Univariable analysis for sternal instability at 6 weeks (categorical variables)
Unstable (5) Stable (15) P
Unstable day 2 1 (20%) 0 (0%) 0.25
Female 0 (0%) 4 (26.6%) 0.282
DM 3 (60%) 3 (20%) 0.131
COPD 4 (80%) 7 (46.7%) 0.221
LIMA 5 (100%) 6 (40%) 0.03
Lateralization 2 (40%) 2 (13.3%) 0.249
Re-exploration 1 (20%) 2 (13.3%) 0.6
Superficial infection 0 (0%) 1 (6.7%) 0.75
Deep infection 4 (80%) 0 (0%) 0.001
Pain was assessed using the visual analogue scale (VAS) on day two and week six in the postoperative period. VAS was found to be positively correlated with the measured ultrasound distance. (Table 9 & Figure 11)
Table (9): Correlations between the ultrasound measurements and VAS
VAS day 2 VAS week 6
Pearson correlation P CI Pearson correlation P CI
Expiration 0.605 0.005 0.222 – 0.826 0.809 <0.001 0.571 – 0.922
Limb elevation 0.553 0.011 0.146 – 0.8 0.822 <0.001 0.597 – 0.927
Inspiration 0.54 0.014 0.128 – 0.793 0.871 <0.001 0.698 – 0.948
Sagittal 0.513 0.021 0.091 – 0.779 0.835 <0.001 0.623 – 0.933
Figure (11): Correlation between VAS on week 6 and Ultrasound measurements during inspiration.
The sample size was too small to calculate cut off points for ultrasonic measurements associated with sternal instability at 6 weeks. However, the following arbitrary cut off points would have very high sensitivity, specificity, positive and negative predictive values. (Table 10)
Table (10): The accuracy of the study carried out.
Cut off point Sensitivity Specificity +ve predictive value -ve predictive value
Expiration 2 100% 100% 100% 100%
Limb elevation 3 100% 100% 100% 100%
Inspiration 2.4 100% 100% 100% 100%
Sagittal 1 80% 100% 100% 93.8%