Objective: To investigate the microhardness distribution of cancellous bone in the proximal tibia and its clinical significance. Methods: Three fresh tibias were obtained and examined by X-ray and CT to exclude skeletal pathologies, such as osteoporosis, osteoarthritis. According to the Heim's square, the proximal tibias were cut off. Each of the proximal tibias was divided into three parts, the medial condyle, the intercondylar area and the lateral condyle. Each part was divided into three sections, proximal, middle and distal sections. Each of the proximal tibias was divided into 9 regions. Bone specimens with a thickness of 3 mm were taken from each region using a high precision low-speed saw and fixed on flat sheets. The microhardness of the bone tissue was measured using a Vickers microhardness tester after polish. Ten effective micro-indentation tests were conducted in each region. After measurement the diagonal length of the indentations, the microhardness values were calculated via software provided by the hardness tester. Analysis of variance and Tukey method were used to compare the microhardness values of different parts, sections and regions of cancellous bone. The microhardness distribution of the proximal tibia was analyzed. Results: A total of 270 effective indentations were made in the specimens, and the microhardness values were obtained. The average microhardness of the three proximal tibias was 40.98±3.44, 34.92±4.64 and 39.49±3.86 HV, respectively. There was a significant difference among the groups (F=55.87, P=0.000). The microhardness distribution of bone tissue in the three proximal tibias was similar. In the comparison of different parts, the microhardness of medial condyle was greater than that of the lateral condyle, which was larger than that of the intercondylar area. The difference between the parts was statistically significant (F=18.42, 8.236, 10.877; P=0.000, 0.001, 0.000). In the comparison of different sections, the microhardness of the distal section was greater than that of the proximal section, which was larger than that of the middle section. The difference between the sections was statistically significant (F=8.720, 17.140, 6.142; P=0.000, 0.000, 0.003). The microhardness distribution was similar among different regions. The region with the highest microhardness is the medial condyle of the distal section with microhardness of 44.87±3.25 HV (range 39.2-49.7 HV). The lowest microhardness was in the intercondylar area of the middle section with hardness of 29.41±4.53 HV (range 24.8-36.2 HV). Conclusion The microhardness value of cancellous bone near the articular surface at the proximal tibia was smaller, which could disperse the load and protect the fragile of articular cartilage. Furthermore, the microhardness of the transition zone is larger. The microhardness value of the cancellous bone in medial tibia condyle is the greatest, which is related to load-bearing.

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 (proximal: 3 layers; midshaft: 7 layers; distal: 5 layers), and each layer was divided into four directions: superior, 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)The average hardness of cancellous bone was (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.