| Objective:Developmental dislocation of the hip(DDH) is one of the most common diseases in department of pediatric orthopedics. The reported incidence rate of DDH throughout the world varies substantially from 0.1% to >10%.Some risk factors, including female sex, genetic factors, firstborn child, and breech presentation, have been identified; However, the actual cause of the disease is still unknown. Arthrochalasis is related to DDH,with the fact that DDH children generally suffer different degrees of joint laxity. Joint capsule is mainly composed of collagen and a small amount of fibroblasts. The major comprising collagens of the capsule are collagen type I and III, and noticeably the former makes up 83% of the collagen present. Collagen type I is located in tissues requiring high levels of mechanical strength, and increases at sites where new fibrosis and connective tissue proliferation occurs. Collagen type III is involved in the development and differentiation of mesenchymal tissue, and is present in large quantities in tissues requiring high levels of mechanical compliance. The determination of collagen types I and III expression levels is of value in assessing whether the changes in the capsule of a joint developing arthrochalasis. This experiment is aimed to explore the correlation between the expression of collagen I and III in capsule of developmental dislocation of the hip(DDH) and the grade of dislocation by detecting the expression of collagen types I and III in hip joint capsule. Methods:In our hospital, there were 120 children with late-diagnosed DDH who were diagnosed after 18 months of age. 155 cases of the hip joint capsule with DDH for specimens biopsy were taken during the surgery in 120 patients from September 2012 to June 2014.In the 120 patients(155hips), the mean age is 3.2 years(range: 1.5–7years), 95 patients with125 hips are female and 25 patients with 30 hips are male; 85 cases are unilateral DDH and 35 bilateral; 98 specimens come from left and 57 from right. The patients were divided into three groups according to age: Group I: 1.5–2.5 years; Group II: 2.5–3.5years; and Group III : 3.5-7years. The degree of dislocation was evaluated by Tonnis’ classification before operation. Then they were divided into three groups by Tonnis standard according to their preoperative X-ray films, with 24 ones with acetabular dysplasia,48 ones with hip subluxation and 83 ones with hip dislocation.All specimens were studied with morphologic observation, histological stain,immunohistochemistry and RT-PCR. The immunohistochemical technique(Two-step method) was applied to demonstrate the expression of type I、III collagen of the hip joint capsule, combined with computer imaging analysis to calculate the positive expression,then compared the change of collagen type I、III expression in semiquantitative between individual groups. Meanwhile, m RNA expression of type I、III collagen in hip joint capsule was extracted and assessed by RT-PCR. The detected data was analysed by the SPSS16.0 statistical software, P<0.05 viewed as statistically significant. Results:The general Morphology and histology observed: The hip joint capsule of DDH was elongated as gourd-shape; Thickness of the joint capsule was uneven; The thickening of osterolateral joint capsule was obvious, but the anteromedial stretched thin, and the higher the degree of dislocation,the more significant the change. Hip capsule includes synovial membrane,synovial lower and fiber layer. Synovial membrane is densely arranged collagen fibers without blood vessels and significant difference between groups. Fibroblasts and collagen fibers around were found in Fiber layer, amongst which there were visible capillaries. Fibroblasts of each group were distributed unevenly with relatively different sizes of shape. Immunohistochemistry and RT-PCR: There was no statistical significance in expression of both immunohistochemistry and RT-PCR of collagen III(P>0.05). The expression of Type I collagen immunohistochemistry and RT-PCR became significantly lower in hip dislocation group(P<0.05). There was no statistical significance between the different age groups, different gender groups, left and right groups, unilateral and bilateral groups(P>0.05). The number of patients with high degree of dislocation reduced with age, which showed negative correlation(P<0.05). There were no statistical significance between the different gender groups, left and right groups, unilateral and bilateral groups(P>0.05). Conclusions:The hip joint capsule of DDH was elongated as gourd-shape with uneven thickness of the joint capsule, obvious thickening of posterolateral joint capsule, but the anteromedial stretched thin, which is related to the degree of dislocation. It could be caused by the long-term repeated pulling stimulate of caput femoris on joint capsule. Type I collagen expression was reduced in the group with high level of dislocation. This may be one of the causes of the relaxation of hip joint capsule and hip dislocation. The number of children with high level of hip dislocation decreased dramatically, which is considered to be caused by the fact that exacerbation of limping gait of children with DDH caused family’s attention so that the children would accept active treatments... |
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