| Part One Study on the measurement of micro-hardness of Chinese human body using microindentation technologyObjective: To systematic and comprehensive evaluate the bone hardness distribution on different region of proximal humerus.Methods: Three healthy donors(age range 45 to 62 years)were included in this study.After removing the soft tissues,multi-layered specimens were taken from the whole body's axial bones and unilateral limb bones horizontally and vertically with their long axes.Vickers tests are performed on different areas of the sample surface using a micro-hardness tester(Model KB5BVZ-Video,Germany).The distribution of bone hardness was studied by statistical analysis.Results: A total of 5360 indentations were selected from 1072 sites of interest in each remains.The microbone hardness of axial bones and limb bones are different due to the different anatomical parts,but their distribution still has certain rules.The occipital hardness of the skull in the axial bones is the highest,with an average hardness of(47.29±7.31)HV;the sacrum has the lowest hardness of the vertebrae,with an average hardness of(24.44±2.66)HV,and the hardness of the lumbar spine(32.86 HV)is higher than that of the cervical spine(28.51 HV)and thoracic spine(29.01 HV).Secondly,in the limbs,the hardness value of the bone shaft is larger than that of the metaphysis,and the average hardness value of the proximal and distal ends is lower than that of the bone shaft(8.85%-40.39%);the tibia shaft is the hardest,with an average hardness(51.20±5.37)HV;In addition,the hardness value of the posterior iliac spine of the ilium is the lowest,with an average hardness of(22.97±4.55)HV.Under normal circumstances,the hardness of cortical bone is greater than that of cancellous bone,and in some anatomical parts,cortical bone is not harder than cancellous bone,such as the lumbar spine(cortical bone hardness value is 32.86 HV,cancellous bone hardness value is 31.25 HV).Conclusions: The distribution of Chinese human microbone hardness in the whole body bones has certain regularities;these distribution regularities can be used to predict the mechanical properties of different parts of the bone,and can provide accurate data support for a new 3D printing technology,and for different parts The choice of fracture internal fixation strategies and the research of new implant materials provide new prospects.Part Two Micro-hardness distribution of proximal humerus in human skeletonObjective: To systematic and comprehensive evaluate the bone hardness distribution on different region of proximal humerus.Methods: Three healthy donors(62years male.45 years female,58 years male)were included in this study.Proximal humeral bones were cut into3 mm horizontal samples.2 levels were chosen at glenoid level and 3 at surgical neck level.Each bone segment was cut perpendicular to the humeral axis by using a diamond saw.Then Vickers testing was performed on sample`s surface by using a micro-hardness tester(Model KB5BVZ-Video,Germany).Results: Measurements derived from 84 region of proximal humerus showed the average hardness value(37.62±8.82)HV,and highest hardness value(45.82±5.55)HV(medial surgical neck),which was significantly higher than other parts in proximal humerus.(P < 0.001)The lowest value(28.32±4.35)HV was measured at cancellous bone of the great tuberosity.From the anatomical region,hardness value of total surgical neck(44.07±6.45)HV was significantly higher than humeral head,great tuberosity and lesser tuberosity.(P<0.001)On the contrary,great tuberosity hardness value(29.56±5.68)HV was the lowest region.(P<0.01)The anterior humeral head was harder than posterior humeral head,lesser tuberosity was hard than great tuberosity.And anterior aspect of surgical neck was harder than other three direction regions.(P<0.05)Conclusions: We presented that bone hardness distribution among different regions of proximal humerus had similar trends.These regularities will mark a guideline for further internal fixation strategies.It`s also helpful to rationally design implants and assist 3D-pringting prosthesis coordinate with bone tissue physiological properties.Part Three Micro-hardness distribution of distal humerus in human skeletonObjective: The aim of this study was to explore the distribution characteristics of microbone hardness in different parts of the distal humerus and its clinical significance.Methods: This study included 3 fresh specimens of the distal end of the humerus,taken from the right humerus of 3 fresh frozen cadavers.After segmenting the medial condyle,trochlear,and lateral condyle with a mini-table saw,one slice was taken horizontally from the metaphysis of the distal humerus,and three slices of bone tissue were taken from the horizontal and vertical axis of the internal and external epicondyle.After being finely polished and fixed,the hardness value was measured on different areas of the specimen surface using a Vickers microhardness tester.Statistical analysis of the distribution of bone stiffness in different regions of the distal humerus.Results: A total of 84 parts of the distal humerus were measured.The average hardness of the distal humerus was(36.70±8.82)HV.Among them,the anterior part of the metaphysis of the distal humerus had the largest hardness(47.97±3.69)HV.31.83±6.40)HV,the difference was statistically significant(P<0.001).From anatomical point of view,the overall hardness of the metaphysis of the distal humerus(44.98±5.43)HV is greater than that of the inner and outer epicondyles of the humerus;the hardness of the metaphysis of the distal humerus(47.97±3.69)HV of the middle and outer epiphysis is greater than the hardness of the posterior(41.54±6.51)HV,P<0.05;internal humeral epicondyle hardness(38.59±9.05)HV > humeral trochlear hardness(35.02±8.67)HV > external humeral epicondyle hardness(32.24±8.52)HV,P <0.05.Conclusions: The distribution of bone microhardness in different regions of the distal radius has certain rules.It can provide data basis for the internal fixation strategy and individualized treatment for different types of fractures of the distal radius,and provide a basis for 3D printing of the distal radius and elbow joint bionic prosthesis.Part Four Study on the micro-hardness of different parts of the humerus and the biomechanical properties of the screwsObjective: Discuss the distribution law of micro-hardness in different parts of humerus,the distribution law of screw pullout strength in each part of humerus,and the relationship between humerus microbone hardness and screw pullout strength.Methods: In this experiment,6 humerus specimens from 3 fresh cadavers were divided into three parts: proximal humerus,humeral shaft,and distal humerus according to the principles of AO anatomy.And take two parts of the proximal humerus,the shoulder joint glenoid of the humerus and the surgical neck of the humerus;the humeral shaft is divided into 7segments,named humerus shaft 1-7 respectively;the distal humerus was located at the metaphysis of the distal humerus and the level of the medial and lateral condyle.Each humerus was divided into 11 sections by a micro table saw according to the selected parts.The bone hardness values of 11 parts of the right humerus were measured with a micro Vickers hardness tester,and 11 parts of the left humerus were measured with a biomechanical machine.The screw pull-out strength.The distribution of microscopic bone hardness and screw extraction force in the humerus was statistically analyzed by a randomized one-way variance test.The relationship between the biomechanical properties of screw extraction and bone hardness was statistically analyzed by Pearson correlation analysis.P<0.05 defined as a statistically significant difference.Results: The results of microhardness measurement showed that the bone hardness of humerus shaft was significantly higher than that of proximal and distal humerus,and the difference was statistically significant(P<0.05).The pull-out strength experiment showed that the pull-out force of the humeral shaft was significantly greater than that of the proximal and distal humerus.The distribution of humerus bone hardness and pull-out strength was similar,and there was a strong positive correlation between the pull-out strength of the humerus screw and the bone hardness value(R=0.818,P=0.002).Conclusions: This experimental study shows that the humeral bone hardness is positively correlated with the screw pulling strength,and the humeral bone hardness value and the screw pulling strength both show the distribution rule of large humeral shaft and small both ends of humerus.The microhardness of humerus bone was positively correlated with screw holding strength. |
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