| ObjectiveTreatment of bone defect is a great challenge in orthopedic diseases. As the processof bone defect healing of infectious osteomyelitis goes very slowly, long-term clinicalobservation and follow-up visits are necessary. X-ray radiography combined with clinicalexperiences is often considered as the traditional methods to evaluate the process of bonedefect healing. However, X-ray radiography could not reveal internal strength and qualityof callus. In the aim of realizing effective evaluation of the callus growth and fracturehealing, this experiment was designed to use Dual Energy X-ray Absorptiometry (DEXA)to monitor the Bone Mineral Density (BMD) changes and to evaluate the correlation ofBMD and biomechanical testing results. The whole experiment were composed of twomain parts:1. Use New Zealand rabbits to establish the animal model of bone defect, discuss thefeasibility of using DEXA method to evaluate callus biomechanical properties and optimize evaluation index to improve the reliability of evaluation.2. Evaluate the reliability of DEXA method in the treatment for osteomyelitis fromthe clinical trials, set a new effective quantified method for evaluation of the callus growthand fracture healing.Method1. Animal experimentTwenty New Zealand rabbits were used to establish the animal models of bone defectfor the experiment. Rabbits were randomly divided into4w,8w,10w and12w groups.After4,8,10and12weeks X-ray investigation, Bone mineral Density (BMD)measurement, biomechanical testing and histologic examination were made to comparethe results.2. Clinical trialThe criteria for inclusion and exclusion were based on the results of chronicosteomyelitis treatment.26patients of osteomyelitis with large section of cortical bonedefect were selected. Examination of bone callus quantity as compared with thecontralateral area by DEXAwas given at4,6,8and10months post operation respectively.At the same time, X-ray radiography and Enneking score were used to evaluate thecondition of bone healing and limb function recovery.Results1. Animal experiment: No animals were infected or died during the experiment.1.1X-ray investigation: After4weeks, the areas of bone defect are still clear, with asmall amount of callus forming; after8weeks, content of callus increased obviously in thebone graft area, especially the callus surrounding the bone defect; after10weeks, thedefect area became fuzzy with dense callus formation; after12weeks, callus in the bonegraft area became more dense and the recanalization of the medullary cavity appeared.1.2BMD measurement: The BMDs of samples at each time point were different fromeach other(P <0.05). However, no obvious difference from each other was found in thecontrasted groups (P>0.05). The BMD ratios at each time point were significantlydifferent from each other(P <0.05). 1.3Biomechanical Testing: The maximum bending loads of samples at each timepoint were different from each other(P <0.05). However, no obvious difference fromeach other was found in the contrasted groups (P>0.05). The maximum bending loadratios at each time point were significantly different from each other(P <0.05).1.4Histologic Investigation: After4weeks: a mass of bone cells, osteoblasts andbone matrix appeared in the graft area; after8weeks, bone trabecula increased graduallyand more mature bone trabecular can be seen in the callus; after10weeks, bone callus hadgrown into mature bone, cortical bone was restored; after12weeks: Numerous maturebone trabecular and cortical bone can be seen in the callus and medullary cavity wasrebuilded.1.5Correlation between BMD and biomechanical testing: The data of the BMD andthe maximum bending loads are positive correlated, and the correlation coefficient is0.753(P <0.05).The data of the BMD and the maximum bending loads ratios are positivecorrelated, and the correlation coefficient is0.835(P <0.05).The data of the BMD ratiosand the maximum bending loads are positive correlated, and the correlation coefficient is0.851(P <0.05).The data of the BMD ratios and the maximum bending loads ratios arepositive correlated, and the correlation coefficient is0.953(P <0.05).2. Clinical trial: after10months,21cases of patients can walk in the weight-bearingsituation, achieving clinical healing;5patients can’t walk in the weight-bearing situation.2.1X-ray investigation: After4months, the areas of bone defect were still clear, withsparse callus passing through and a small amount of callus forming; after6months,content of callus increased obviously in the bone graft area, especially of the callussurrounding the bone defect;8months later, the defect area became fuzzy with densecallus formation. The callus surrounding the bone defect reduced gradually. By10months,callus in the bone graft area became more dense and the recanalization of the medullarycavity appeared.2.2Enneking score: The scores of samples at each time point were different fromeach othe(rP <0.05). The the at each time point were different from each othe(rP <0.05).The mean of final percentage of function at10month is95.4%. 2.3BMD measurement：The BMDs of graft area at each time point were different\from each othe(rP <0.05). However, no obvious difference from each other was found inthe contrasted groups (P>0.05). The ratios of two sides at each time point were differentfrom each othe(rP <0.05). The BMD measurements of two sides were different from eachother at4,6and8months post the operation (P <0.05). However, no obvious differencewas found between the two groups at10months post operation (P>0.05), which showedthat the BMD of callus of draft area had basically reached the contralateral normal level at10months post operation, and the average BMD ratio is96.7%.2.4Using the Pearson correlation test between the BMD ratio and percentage offunction change, the result showed these two groups of data are positive correlating, andthe correlation coefficient is0.948(P <0.05).ConclusionDEXA is an effective quantitative method for evaluation of the biomechanicalproperties of the callus and results are reliable. DEXAcan be used to assess callus growthand fracture healing clinically.2. While the average BMD ratio is96.7%, the percentageof function achieved95.4%at10months post-operation, and patients could walk on fullyload-bearing. |
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