Mechanical analysis of total hip replacement with cup of different diameters in patients with developmental dysplasia of hip / 中国组织工程研究

ABSTRACT

BACKGROUND:The anatomical structure of acetabulum is different for the developmental dysplasia of the hip, which is smal and shal ow, with abundant cal us and scar tissue. It is difficult to determine the diameter of cup and instal ation of the cup during arthroplasty. Loosening and survival of postoperative prosthesis were influenced by local mechanical changes. OBJECTIVE:Using the three-dimensional finite element analysis, the stress distribution in acetabular cup-bone interface after implanting cups with different diameters was studied during total hip replacement in treating the dysplasia of hip. METHODS:Pelvis of developmental dysplasia of the hip patients was selected in this study. Acetabulum in the dysplasia was scanned by spiral CT. The computer simulation technology was applied to reconstruct the three-dimensional model of the pelvic for observing the dysplasia of hip from CT scan picture. Implanting cups with different diameters were simulated. Then the pelvis and acetabular cup model were meshed. The mechanics analysis tool was used to analyze three-dimensional model. RESULTS AND CONCLUSION:For the developmental dysplasia, we chose cup with smal diameter that could lead to better bone bed inclusion of cup during total hip replacement. Smal diameter cup induced a smal contact area and increased unit area stress. On the other hand, with implanting the larger cup and increasing degree of acetabular grinding, the acetabular wal bone breaks more obvious, so that the stress (compressive stress and shearing force) concentration at the top of the acetabulum and uneven stress in the rest were apparent increasingly. Thus, in clinical practice, under the premise of the bone bed inclusion, a large diameter cup is helpful to good distribution of stress during total hip replacement, but the perforation of acetabular wal induced by enlarged bone bed should be avoided or minimized.