| Background and objectives:Bone marrow lesions(BMLs)is a signal alteration of subchondral area detected by Magnetic resonance imaging(MRI).On MRI,the signal alterations are characterized by low signal intensity on T1-weighted(T1WI)images and high signal intensity on T2-weighted(T2WI)and short tau inversion recovery(STIR)images.The signal alterations are common in patients with knee osteoarthritis(OA)and have been found to associated with clinical symptoms like pain and some structural abnormalities.So many researchers have carried on some research on BMLs associated with OA.However,the signal alterations of BMLs are nonspecific,and a number of traumatic and nontraumatic pathologies may show similar imaging characteristics.Research about the pathophysiology,clinical significance,progression and prognosis of subchondral BMLs is still limited but has been increasing quickly in recent years.The subchondral bone is adjacent to articular surface.As foundation of hyaline cartilage and calcified zone,many researchers have regarded the haline cartilage,calcified zone and subchongdral bone as a functional unit as a whole.In the occurrence and development of OA,their relationship is closely.BMLs is not present under all the surface of OA,and there is no OA appear at some surface of BMLs.So just when BMLs appears in the position with OA or cartilage lesions,it may be associated with OA or cartilage lesions.When the cartilage at the surface of BMLs is complete,there may be another reason for it.The pathological changes of the lesions in BMLs are very important for understanding the diagnosis,cause and prognosis of the disease.To make clear the histopathological changes of BMLs is important for understanding the diagnosis,cause and prognosis of the disease.But at present,there are few literatures about pathology of BMLs and almost all the literatures focused on the lesions in the area of wearing.There is no pathological study about the lesions in the non bearing area.Non traumatic focal BMLs in the area of non bearing like patellofemoral joint,posterior femoral condyle is common in the clinical work.In these patients,there is no sign of OA in the area,the range is limited and the boundary is relatively regular.Because this kind of disease usually did not undergo the surgery or biopsy,its basic pathology,diagnosis is not clear,the treatment was lack of pertinence.This study aimed at the pathological research of BMLs in the non weight-bearing area like patellofemoral joint and posterior femoral condyle.So we choose the OA patients with BMLs in the non weight-bearing area as subjects.We got the specimens through total knee arthroplasty(TKA),then performed the pathological observation,got some pathological results to provide a theoretical basis for clarifying the diagnosis and pathological characteristics of the disease,and the further study for pathogenesis and treatment.Materials and methods:1.Case selection:115 patients(age 40-70y)who suffering from knee OA were selected in center of joint surgery,southwest hospital.Rheumatoid arthritis,trama,infection,tumor and anyother diseases.All the patients took MRI examination before surgery.10 subchondral focal BMLs in the area of non-weight bearing were detected.The patients included 3 males and 7 famales.The specimens were voluntarily donated by the patients.2.Obtaining specimens:5 specimens were obtained from 2 males and 3 famales with an average age of 61years(range,53-67),The mean disease duration was 6.2 years(range,4-12years).5 BMLs were located at 2 patella,2 anterior femoral condyle and 1 posterior femoral condyle.3.Gross observation:5 specimens with BMLs were taken from the TKA.The appearance,colour,integrity,malacia,ulcers,chap of the cartilage were observed by naked eye.The lesions degree of the cartilage were evaluated.The shape,density,cyst,granulation tissue,fibrosis focus of the bone marrow were observed too.4.Histological observation: Specimens were fixed,decalcified,paraffin embedded and sectioned.Then they were stained with HE,safranin O/fast green in order to observe the pathologic characteristics of the BMLs and adjacent control area,and make clear the pathological changes of different types of abnormal tissue in the HE stained sections.5.Tissue composition analysis and measurement of trabecular bone:The boundary of all kinds of abnormal pathological tissue in BMLs in the HE stained sections.the percentage of the area was analysed and calculated by Pro Plus Image 6 image analysis software.Bone volume/ total bone volume(BV/TV)was measured in the safranin O/fast green stained sections in accordance with the method of bone tissue morphology.6.Statistical analysis:Measurement data was represented by mean.A paired t test was used to evaluate the differences of mean percentage areas in lesion and control regions.A P value of less than 0.05 was considered to indicate a significant difference.Results:1.Gross observation: Ⅰ-Ⅳ°lesions of the cartilage existed in all the 5 specimens with BMLs.1 case of patellar lesions was cystic changes and the surrounding bone tissue was complete.The remaining 4 cases of the lesion area were cancellous bone without obvious necrosis.2.Histological observation: 1 case of patellar BMLs lesions was cystic changes with bone trabecular destruction,absorption,and a large number of infiltration liquid with fibrous granulation tissue formation.In the surrounding area,the bone trabecular morphology was relatively normal,and the medullary cavity was filled with inflammatory exudation.The other 4 cases contained normal tissue(fatty marrow 53.6%,intact trabeculae 23.0%,blood vessels 0.3%)and abnormal tissue(bone marrow edema 3.2%,bone marrow necrosis 12.9%,bone marrow fibrosis 1.6%,bone marrow bleeding 1.7%,abnormal trabeculae 3.7%).Compared with the control regions,significant differences were found for bone marrow necrosis(P=0.029)and trabeculae abnormalities(P=0.028)but not for bone marrow edema(P=0.052),bone marrow fibrosis(P=0.182),and bone marrow bleeding(P =0.128).3.Measurement of trabecular bone: BV/TV of lesion regions was 26.7% and lower than the value of control regions(36.4%)with statistical significance(P=0.008).It was also significantly lower than previously reported values of subchondral bone of normal or OA.Conclusions:1.The BMLs lesions in the non load bearing area of the knee showed some nonspecific abnormal histological features,and the normal tissues still accounted for the main.2.The abnormal tissue of this kind of BMLs lesion showed some common features,such as different degrees of cartilage injury,low proportion of bone marrow edema and not obvious evidence of avascular necrosis.3.BV/TV of lesion regions decreased significantly,which indicated that the bone mass was decreased with significantly different from OA region. |
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