TOUGHNESS OF THE STERNUM Selthofer R, Nikolić V, Radić R, Lekšan I... University J. J. Strossmayer in Osijek, School of Medicine

1. INTRODUCTION sternum (the breastbone) is a flat bone situaded vertically in the median and anterior part of the thoracic skeleton it has a great clinical significance, considering that median sternotomy is the most common surgical approach used in cardiac surgery when applying this surgical intervention, the sternum is cut through in midline from the jugular notch to the xiphoid process and thus access to the anterior mediastinal organs, especially to the heart and major blood vessels is gained

1. INTRODUCTION dehiscence of the sternotomy closure and consequential separation of the sternum halves as well as development of deep mediastinitis is a relatively rare but a serious complication incidence rate is between 0.5 – 2.5%, but some studies show that it can be higher, even up to 8% suture dehiscences may be influenced by various factors, such as suture technique, osteoporosis level, sex, comorbidity, various perioperative and postoperative factors and many others

only good mineralised bone, which is enough tough can avoid fracture 1. INTRODUCTION investigation of the sternum toughness was part of more complex study which included also morphometric analysis and analysis of the sternum mineral density by various methods (radiographic apsorptiometry, dual energy apsorptiometry and determining real density by ashing of defined volumes of sternum bones) here we are focused on sternum toughness, which is important factor in defining osteoporosis definition of osteoporosis include both,bone mineral density and bone toughness only good mineralised bone, which is enough tough can avoid fracture

to investigate sternum toughness 2. AIMS OF THE STUDY to investigate sternum toughness to determine regional sternum toughness to detect sex and age differences to find out what is the role of the sternum toughness in occurence suture dehiscence after cardiac surgery median sternotomy

materials consisted of 93 cadaveric sternums 3. MATERIALS AND METHODS prospective study materials consisted of 93 cadaveric sternums 38 female and 55 male bones average age was 65, it varies between 18-90 years all bones were fixed in formalin for the three months

3. MATERIALS AND METHODS in order to determine regional sternum toughness, each sternum was divided into six pieces

3. MATERIALS AND METHODS toughness of each sternum sample was determined by Charpy pendulum method energy nedded for cutting sternum sample (J) was divided with cross-sectional area of each sample (cm2)

there are great varieties in sternum toughness, independent on sex 4. RESULTS there are great varieties in sternum toughness, independent on sex sternum toughness varies in great range from 12 to 40 J/cm2

4. RESULTS there are no significant statistical sex differences, inspite average toughness value for male samples is great than female (J/cm2) female ± SD male T p MANUBRIUM A 22,39±10,71 24,52±9,08 -0,82 0,41 B 20,11±8,63 20,68±6,84 -0,30 0,77 C 22,59±7,66 24,15±8,27 -0,71 0,48 BODY OF THE CORPUS a 17,23±8,27 19,28±7,47 -0,99 0,33 b 17,65±9,36 17,11±8,55 0,22 0,83 c 16,39±7,49 19,05±8,59 -1,25

Map of regional sternum toughness 4. RESULTS Map of regional sternum toughness 255 g/cm3 FEMALE –there are no significant differences between specimens, inspite manubrium has great average toughness MALE- significantly, manubrium has great toughneess than body, also median part of the manubrium is tougheer than laterals 1 g/cm3 FEMALE MALE

4. RESULTS these hystological specimens clearly show differences between good and pour mineralised (osteoporotic) sternums demineralisation and process of deterioration of sternum toughness by aging for most specimens are parallel processes in some rare cases we found inproperly hypermineralised sternums with low toughness, very rare were the specimens with low mineral density rate which had good toughness 0,352 g/cm3 0,120g/cm3

5. CONCLUSION sternum strength determined by toughness is important factor in estimating the risk of sternal dehiscence after cardio-surgical sternotomy new findings of regional differences in sternum toughness can help in discovering optimal techniques of sternum circlage after median sternotomy

15. FURTHER STUDY All those I mentioned of sternum structure and strength is for better understanding and for helping constructing optimal technique for sternum closure after median sternotomy, so we investigated further...

We constructed special machine for dynamic testing of different sternum closures

circlage after median sternotomy with steel wires, prepared for testing

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