Distribution characteristics and clinical significance of clavicle microindentation hardness / 中华创伤杂志

ABSTRACT

Objective To investigate the distribution characteristics and significance of bone hardness in different segments and layers of clavicle. Methods The right clavicles of three fresh Chinese corpses were taken and then divided into proximal, middle and distal segments according to Allman's classification. The clavicles were cut with diamond saw in the vertical of long axis equidistant exactly into 15 layers ( proximal3 layers; midshaft7 layers; distal5 layers ) , and each layer was divided into four directionssuperior, inferior, anterior, and posterior. The bone hardness were measured by Vickers microindentation, HV ( kgf/mm2 ) . The distribution of bone hardness was recorded and analyzed. Results A total of 180 parts of cortical bone were measured, generating 900 measurements. Meanwhile, a total of 45 parts of cancellous bone were measured, generating 225 measurements. We found that(1)The average hardness of cortical bone was (35.9 ±8.1)HV, and the midshaft segment[(41.3 ±6.8)HV] was harder than the proximal segment [(33.8 ±6.1)HV] and the distal segment [(29.7±5.4)HV](P<0.05);(2)Theaveragehardnessofcancellousbonewas(30.7±6.2)HV, and there were significant differences among the midshaft segment [(34. 5 ± 5. 5)HV], the proximal segment [(29.2±2.9)HV] and the distal segment [(26.3 ±5.1)HV](P<0.05);(3)for cortical bone, the hardest segment was the fifth layer of the midshaft segment [(44. 8 ± 8. 6)HV] while the most soft segment was the fourth layer of the distal segment [(28. 0 ± 3. 5)HV](P<0. 05);(4)for cancellous bone, the hardest segment was the fifth layer of the midshaft segmnet [(36. 8 ± 5. 1)HV] while the most soft was the fifth layer of the distal segment [(23. 0 ± 4. 4) HV] (P<0. 05);(5) There were no statistically significant differences among four directions of segments(P >0. 05). Conclusion The microindentation hardness varies greatly among different segments and layers of the clavicles. The cortical bone and cancellous bone have consistent hardness changes, which shows that the middle segment is obviously harder than the proximal and distal segments with a gradually gradient decreasing trend from the middle to both ends. The data can be used to guide the design of 3D printing implants that conform to the stress conduction characteristics of the clavicle under physiological conditions, and provide good data support for the modeling and finite element analysis of the clavicle under simulated physiological conditions.