Development Of A New Sternal Fixation Device; An Uncalcined Hydroxyapatite Poly-l-lactide Corrugated Sheet
Hidehito Kuroki1, Smith Srisont2, Hirokuni Arai1.
1Tokyo Medical and Dental University, Tokyo, Japan, 2Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
OBJECTIVE: Wire cerclage is the most frequently used sternotomy closure technique after median sternotomy. However, wire cerclage sometimes has insufficient fixation effect on the sternotomy halves. Bioabsorbable uncalcined hydroxyapatite poly-l-lactide (uHA/PLLA) sternal pins (Takiron Co., Ltd., Osaka, Japan) are inserted in the sternal bone marrow to prevent displacement of the sternum. However, the sternal pins do not provide an adequate fixation effect in older patients, whose bone marrow is too fragile to retain the pin in the same position. Thus, we developed a new sternal fixation device.
METHODS: The new sternal fixation device is a corrugated sheet which is made of uHA/PLLA (length 30mm × width 21mm) and designed to be easily inserted in the bone marrow. In 18 cadavers, insertion feasibility of the device was assessed in relation to the hardness of bone marrow. Following insertion of the device, device position was evaluated by CT scan in 6 cadavers. In three cadavers, shear force to displace the cerclaged sternal halves were measured with or without the device.
RESULTS: The upper limit of sternal bone marrow hardness that could accept the device was 0.85 Megapascals. Accordingly, application of the device was feasible in 10 of the 18 cadavers, whose mean age was 65 ± 10 (48 - 80) years. The mean age of the rest of 8 cadavers was 42 ± 14 (21 - 66) years. CT scan showed proper positioning of the device in all 6 cadavers. The shear force of sternum displacement was significantly higher when device was implanted (5.6 ± 1.0 kgf) in comparison with that without the device (2.8 ± 0.3, p<0.05).
CONCLUSIONS: This new sternal fixation device would provide stronger fixation of the sternum than simple wire cerclage, especially in the old patients with fragile bone marrow.
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