| With the development of the 3D printing technique and the orthopaedics inner fixing apparatus,3D printing can print bone model as the same appearance of real bone.However it not reflect bone biomechanics property.Bone hardness is a comprehensive biomechanics index which contain elastic deformation?plastic deformation and resistance to penetration.The distribution of bone hardness provide basic data to bone module of 3D printing.the biomechanics property of bone model as the same as real bone,which supply the theoretical basis of making the inner fixing apparatus with the same biomechanics property of real bone.Bone hardness have the features of being resistance to penetration and come to a permanent indentation,which is mainly corrected with the bone composition and the structure.It is commonly believed that bone tissue morphological structure changes in response to mechanical loading.The difference of different anatomical sites with in the human skeleton mechanical loading maybe lead to bone hardness different.At present,the internal fixation is the same thickness material,the bone hardness and elastic module is different vary with different regions of anatomy.The mismatching maybe result to internal fixation fracture,so we should adopt the internal fixation which match the hardness and elastic module of the bone,decrease the internal fixation fracture rate.The study will provide the theoretical basic of individualization precise internal fixation treat.In this study,the distribution of radial and ulnar bone hardness and the relationship between radial bone hardness and screw extraction force were studied to provide theoretical basis and numerical support for the clinical application of bone hardness?Ulnar and radial fractures account for 6.3% of total body fractures,proximal ulnar and radial fractures account for 0.84% of total body fractures,ulnar and radial shafts fractures account for 1.47% of total body fractures,and distal ulnar and radial fractures account for 3.99% of total body fractures.Proximal ulnar and radial fractures accounted for 13.32% of ulnar and radial fractures,23.31% of ulnar and radial shafts fractures,and 63.38% of ulnar and radial fractures?According to the epidemiological survey of ulnar and radial bones in the third hospital of hebei medical university from 2003 to 2007,ulnar and radial fractures were more common in males than females and more in the left side than the right side.The most common age was 11 to 20 for men and 51 to 60 for women.The ulna and radius together form the bony structure of the forearm.The proximal end of the forearm is formed by the ulnar joint of the brachium and the brachio-radial joint,while the distal end of the forearm is formed by the ulnar wrist joint and the radial wrist joint area.The ulnar and radial bones are connected by the interosseous membrane,which runs diagonally from the lower part of the ulna to the upper part of the radius.When the arm is in the neutral position,the interosseous membrane is in a state of tension,while when the arm is in the rotating position,the interosseous membrane is in a state of relaxation.The proximal end of ulna was mainly composed of olecranon,coronoid process and ulna tuberosity,while the distal end of ulna was mainly composed of ulnar styloid process.The proximal end of the radius is mainly composed of the radial head,the radial stem and the radial trochanter.The distal radius is mainly composed of the styloid process of the radius.The rotation of the forearm was dominated by the radius around the rotation of the two,ulna relatively straight,nearly period of coarse,far fine,on radial section of fine,the period of coarse,outward form an arc,a radial bows,the existence of the radial bow is done of the anatomical basis of spins the forearm,and ulna to bear more of the torsional stress,due to the length of the radius is fixed,complex movement in the forearm,involves the elbow and forearm rotation of wrist joint flexion and extension,as the rotation of the radius under stress and tension is balanced.Distal radius,where cancellous bone and cortical bone were meet,is relatively weak,which is likely to lead to distal radius fracture.When a distal radius fracture shortens,the load to the ulna increases and a fracture is likely to occur.In addition to the ulna and radius,the maintenance of the longitudinal stability of the forearm is also related to the structure of the interosseous membrane.The tendinous part of the interosseous membrane bears most of the stress transferred between the radius and ulna.The most important factor of ulnar and radial fractures is fall trauma,followed by diseases that affect bone quality,such as osteoporosis.The distal ulnar and radial bones are one of the main bone density measurement sites.Among the patients with distal ulnar and radial fractures,the proportion of osteoporosis patients is significantly higher than that of normal people.The incidence of fractures in the distal radius is far higher than that in the ulnar and radial diaphysis.In addition to the injury mode,it may also be related to the lower hardness of the distal radius than the radial diaphysis.Bone quality is one of the important factors affecting fracture,and anisotropy of bone has a very important effect on the fracture site.At present commonly used biomechanical experiments,such as compression test,tensile test,bending test is applied to the whole radius,and assuming bone material and structure is uniform,used to study the biomechanical properties of the bone,not good according to different anatomical parts of the bone of heterogeneity and anisotropy.Currently,bone mineral density and bone mass are used to evaluate bone strength.Studies have shown that bone mineral density can only reflect 60-70% changes in bone strength,and bone mass is related to bone mineral degree,bone tissue metabolic rate,bone microstructure and micro-fracture.Bone mass can predict and assess fracture risk,but bone mass is a comprehensive indicator,which is difficult to detect.Bone hardness is related to mineral content and microstructure of bone,and is an important index to evaluate bone quality.Therefore,bone hardness is of great significance in predicting fracture risk.Fracture is a partial or total destruction of bone continuity,which is the plastic deformation of bone.Bone hardness is also related to the plastic deformation of bone,so it is speculated that bone hardness may be correlated with fracture to some extent.Different bone hardness in different parts may be related to the incidence of fracture epidemiology in different parts.Currently,fracture internal fixators are all metal homogeneous,while bones are heterogeneous.The hardness of different parts of bones is different,and the hardness of internal fixators is the same,which may cause biomechanical mismatch.Bone hardness can reflect the heterogeneity of bone,and the different bone hardness in different parts may be correlated with the surgical method and the placement of internal fixators.In this study,the relationship between ulnar and radial bone hardness and the epidemiology of ulnar and radial fractures was studied by studying the distribution of ulnar and radial bone hardness.Previous studies used biomechanical methods to study the radius and ulna,but there was a lack of studies and comparisons on the biomechanical properties of different anatomical parts of the radius and ulna.In this experiment,vickers hardness was used to measure the bone hardness of different parts of the ulna and radius,to explore the distribution rule of the bone hardness,and the correlation between the ulna and the ulna fracture epidemiology,fracture surgical methods,3D printing of ulna and other implants and ulna.Postoperative fixation of fracture of radius and ulna is usually performed with plates and screws.The current plates are all homogeneous and of the same thickness,and the screws are also made of the same material.The anisotropy of bone is anisotropy of tissue,uniform plate and screw are not matched with the anisotropy of bone.Loosening of internal fixation caused by screw loosening is a serious complication after internal fixation of fracture.The pulling force of screw is an important factor for the stability of internal fixation.The stability of internal fixation is closely related to the performance of screw and bone.Screw properties such as screw length,diameter,thread,etc.,bone properties include bone volume,bone composition,and bone structure.Different parts of the radius and ulna had different bone hardness.The relationship between the bone hardness of the radius and the screw pulling force was discussed to provide a theoretical basis for the design of internal fixators with human biomechanical properties.At present,the 3D printed prosthesis or internal fixator are all homogeneous,while the bone is not.The different hardness of different parts of the radius and ulna can reflect the characteristics of bone heterogeneity,which can provide digital support for the 3D printed prosthesis that is close to the biological properties of bone.Part one The study of bone micro-hardness distribution in different parts of ulnaObjective:The study of micro-hardness distribution of ulna which the correlation with surgical procedures of ulnar fractures,the internal fixattor,the total elbow arthropolasty and the epidemiology of ulna fracture.Methods: The ulna were divided into proximal metaphysis,diaphysis,and distal metaphysis.The proximal metaphysis was divided into the olecranon and the metaphysis olecranon of ulna,and the disatal epiphysis included the head of ulna.The shaft of the ulna was divided equally into nine segments.Each ulna was sawed by a band saw into twelve parts,which were prepared for the micro-indention testing.The micro-indention testing samples precision cuts were done with a Buehler Isomet 11-1280-250 low speed diamond saw(Buehler,Ltd.,USA).Each micro-indention sample was cut 3mm thickness and fixed on glass sheet with epoxy resin.The samples surface was polished with progressive grades of sandpaper.Micro-indentation was performed on each bone sample surface using a vicker micro-hardness tester(Model KB5BVZ-Video,Germany),and the hardness value were measured as Hardness value((HV,1HV= kgf/mm2).Twenty indentions were randomly selected on each sample,which were equally divided into four quadrants(anterior,medial,posterior and lateral).Hence,a total of 720 microindentations were performed on the three ulna.Before indention,each sample was controlled under the optical microscope where the bone surface was intact and not damaged.The micro-indentations were performed on each sample with a load of 50 gf.The indentation time was set to 12 s.Hardness value(HV/0.05)was computed for each indentation.The lengths of the diagonals were measured under reflected light microscopy,and the Vickers hardness value was calculated.Indentations in which one diagonal was 10% longer or more than the other were ignored,and the indention was repeated.These preliminary data were used to determine the appropriate sample size of micro-indentation to be performed on each bone segment.SPSS 19.0 statitical software was used for statitical analyis.The one-way ANOVA analysis was used to compare the difference of bone micro-hardness values in different parts,and P<0.05 was statistically significant.Results: The hardest part of the ulna is the lower ulna,the value of micro-hardness is 47.77 HV,The least hard part is the head of ulna,,the value of micro-hardness is 29.64 HV.The proximal metaphysis hardness value is 34.39 HV,the shaft hardness value is 43.47 HV,the distal metaphysis hardness value is29.64 HV.The hardness was higher in diaphysis than metaphysis in the ulna with statistical significance(P<0.001).There was no statistically significant difference in the hardness of ulna anterior,medial,posterior and lateral quadrant.Conclusions:It demonstrated that the shaft of ulna is a significant higher bone micro-hardness value than the two methaphysisees of ulna.The micro-hardness value difference was not significant among the anterior,medial,posterior and lateral quadrant.This study revealed the distribution rule of micro-hardness of ulna and provided data support for the total elbow arthropolasty with human physiological characteristics through 3D printing.Part two The study of bone micro-hardness in different parts of radiusObjective: By measuring the micro-bone hardness of different anatomical parts of 3 fresh radial bone specimens,To analysis the distribution characteristics of bone micro-hardness in different parts of the radius,.our study discusses its relationship between the bone hardness of the radius and the anatomical structure of each part of the radius and the epidemiology of the fracture of the radius.Methods: The 3 fresh radial specimens used in this study were adopted from the right radius of 3 fresh cadavers,Two specimens were male and one female,aged 62,58 and 45,respectively.Before the experiment,all the 3 radial bones were examined by X-ray and CT to exclude systemic diseases affecting the quality of the radial bones,such as osteoporosis,bone tuberculosis and bone tumors.Specimens of the right radius were taken from three fresh cadavers,Carefully remove the soft tissue that surrounds the outside of the radius.According to AO anatomical rules,the radius was divided into three parts: proximal radius,shaft of radius,and distal radius.Then,the radius was cut into 14 parts according to its anatomical location with a miniature table saw.Three specimens of the radial head,radial neck and radial tuberosity rwere cut at the proximal end of the radius.A total of 9 specimens from 1-9 of the radial diaphysis were cut on average.Two specimens of distal radius and styloid process were cut from distal radius.Then,with the American standard music model buehler11-1280-250 high-precision slow speed saw,3 mm thick bone tissue sections were cut from each anatomical part perpendicular to the radius with a micro-table saw to measure the bone hardness.In order to prevent denaturation of bone tissue surface caused by excessive temperature during specimen cutting,In the process of cutting specimens with a slow saw,condensate was used to flush the surface of the radial specimen in all processes to reduce the temperature increase caused by cutting.So as to avoid secondary injury of bone tissue section.The bone tissue specimen was cut and fixed on the slide according to the anatomical position,The name of the anatomical sites and the four directions were marked,The surface of each specimen of the radius was then smoothed by sand paper with silicon carbide particles of different purposes.After placed in the refrigerator-20 ?,for bone hardness measurement using.Before the microhardness of the radial bone was measured,Sections of the radius were removed from the refrigerator,reheated at room temperature,and soaked in normal saline for 1 h,so as to recover the bone tissue dehydration caused by the placement of the radial specimen in the refrigerator.In this experiment,the German kb-5 micro-vickers hardness tester was used for bone hardness measurement.The indenter head of the hardness tester is pressed on the surface of the radial section specimen under a certain load,After unloading the load,a permanent diamond indentation is formed on the surface of the skeleton.Then measure the length of the two diagonal lines of the indentation under the microscope,and then calculate the hardness value of the indentation according to the formula.The measurement unit of bone micro-hardness is expressed by HV or KGF /mm2?Section marked on every part of the radial specimens before?after?internal and external orientations,each orientaion area was randomly selected five site measurement.According to the experimental method of previous similar studies,th the hardness value was measured by 50 g force loaded for 12 s..The data with a difference of more than 10% between the two diagonal lengths of each indentation will be removed It shall be retested in the same area,and the average hardness value of this area and this part shall be calculated according to 5 effective hardness values for each area and 20 effective hardness values for each part?SPSS19.0 was used for statistical analysis of the data.First,the normal test and homogeneity of variance test were performed.The distribution of the micro-bone hardness values of each part of the radius was in line with the normal distribution.Univariate anova was used to compare the differences in microbone hardness values of each anatomical part of the radius,and multiple comparisons were made afterwards.As the hardness values of each anatomical part of the radius met the standard of homogeneity of variance,Tukey test was used for the comparison between groups,and P < 0.05 was used for the difference with statistical significance.Results: In this experiment,14 anatomical sites of 3 radial specimens were cut.Respectively: the radial head,neck and trochanter of the radial well segment;Radial diaphysis 1-9 of the radial diaphysis;The distal end of the radius and the styloid process of the radius were divided into 14 parts.A total of 42 radial specimens were sectioned and microhardness measurements were made at 840 sites.The distribution characteristics of microhardness of each part of radius were obtained:The mean overall hardness of each anatomical part of the radius was between 19.10 HV and 60.40 HV,and the mean hardness was 39.70 HV,In each anatomical part of the radius,the maximum hardness value is radial shaft 8,which hardness value was 43.82 5.20 HV,while the minimum hardness value is radial head,its hardness value was 33.30 HV.Among the total hardness of the three radial specimens,the micro bone hardness of the radial diaphysis was the highest,and the hardest part was located in the lower part of the radial diaphysis.The micro-hardness values of the proximal and distal radii were similar,both of which were lower than those of the radial diaphysis.The micro-bone hardness of the radial diaphysis is the highest,its 42.54 HV,much higher than the hardness of the proximal radius,34.15 HV,and the hardness of the distal radius,35.24 HV.The hardness values of the shaft radial,proximal and distal ends of the radius were statistically significant(P < 0.001).The bone hardness values of the proximal and distal radii were compared,The difference was not statistically significant?The hardness values of the proximal,diaphysis,and distal of the anterior,posterior,medial,and lateral portions of the radius were compared.The difference was not statistically significant.Conclusions: The distribution of radial microhardness was obtained in this experiment.The microhardness of the radial diaphysis was the highest,and the hardest part was located in the lower part of the radial diaphysis.The microhardness of the proximal and distal ends of the radius were similar,both of which were less than the bone hardness of the radial diaphysis.The high incidence of fractures at the distal radius is related not only to the anatomical morphology and injury mechanism,but also to the sudden decrease of the hardness value here.The influence of bone hardness should also be considered as one of the factors.This experiment revealed the distribution pattern of microhardness of each anatomical part of the radius,and discussed the relationship between bone hardness and the epidemiology of fracture of the radius,providing data support for the 3D printing of the radial microcephaly prosthesis that is more consistent with the biomechanical characteristics of the human bodyPart three Study of the relationship between in different parts of radius bone hardness and biomechanical properties of screwsObjective: This study aims to investigate the bone hardness of different anatomical regions in human radius and its impact on pullout stength of screws.Methods: Fresh radius were obtained from three donated cadavers.The radius were divided into three parts: proximal metaphysis,shaft and distal metaphysis.The proximal metaphysis contains head,neck and radial tuberosity.The distal metaphysis includes palmaris radius and styloid process of radius.The shaft of radius were divided into nine segments with equal length.Bone hardness of three radiuses,one from each cadaver,was measured by Vickers micro-indentation hardness tests,and screws pullout strength by Materials Testing Machine in the other three radiuses.The trend between radius hardness and pullout strength was analyzed by ANOVA randomized block design.Pearson correlation analysis were calculated in order to evaluate the linear correlation between bone hardness and pullout strength of human radius.Result: Mean hardness value ranged from 33.30 HV(the head)to 43.82 HV(the diaphysis).The hardest part of the radius is the shaft,the hardness vaule is 42.54±5.59 HV.The proximal metaphysis hardness value is 34.15± 6.48 HV,the distal metaphysis hardness value is 35.24±5.17 HV.It was found that the shaft is harder 23.5% than the proximal metaphysis and harder 20% than the distal metaphysis.The micro-hardness test demonstrated that bone hardness value of the diaphysis is significantly higher than both proximal and distal metaphysis of radius(both P<0.05).Mean pullout strength value ranged from 552N(the distal metaphysis)to 2296 N(the diaphysis).The biggest pullout strength part of the radius is the shaft,the pullout strength value is 1727.96±111.44 N.The proximal metaphysis pullout strength value is 726.33±236.39 N,the distal metaphysis pullout strength value is 590.67± 36.30 N.It was found that the pullout strength value of the shaft bigger 138% than the proximal metaphysis and bigger 190% than the distal metaphysis.The pullout strength in the diaphysis of radius is also higher than both ends of radius(both P<0.05).A positive correlation was found between bone hardness and pullout strength(R=0.927,P<0.001).Conclusions: Bone hardness and screws pullout strength is higher in diaphysis of radius than both ends.Pullout strength is positively related with bone hardness in the human radius. |
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