Oral teeth image segmentation plays an important role in teeth orthodontic surgery and implant surgery. As the tooth roots are often surrounded by the alveolar, the molar’s structure is complex and the inner pulp chamber usually exists in tooth, it is easy to over-segment or lead to inner edges in teeth segmentation process. In order to further improve the segmentation accuracy, a segmentation algorithm based on local Gaussian distribution fitting and edge detection is proposed to solve the above problems. This algorithm combines the local pixels’ variance and mean values, which improves the algorithm’s robustness by incorporating the gradient information. In the experiment, the root is segmented precisely in cone beam computed tomography (CBCT) teeth images. Segmentation results by the proposed algorithm are then compared with the classical algorithms’ results. The comparison results show that the proposed method can distinguish the root and alveolar around the root. In addition, the split molars can be segmented accurately and there are no inner contours around the pulp chamber.
ObjectiveTo investigate the application value of acetabular centralization technology for correction of leg-length inequality in total hip arthroplasty (THA). MethodsBetween June 2001 and January 2012, 147 cases of abnormal acetabular center were treated. Of them, 68 cases underwent routine THA (control group), and 79 cases underwent acetabular reconstruction by fossae ovalis oriented centralized technology in THA (test group). There was no significant difference in gender, age, side, pathogeny, acetabular rotation center indexs, difference of relative and absolute leg-length, and Harris score between 2 groups before operation (P>0.05). The hip joint function was evaluated by Harris score; the difference of relative leg-length was measured by tape; the difference of absolute leg-length and the horizontal and vertical distances of actual and true rotation center were also measured on the X-ray films by software. ResultsThe patients were followed up 8-26 months (mean, 8.3 months) in the test group, and 6-33 months (mean, 9.7 months) in the control group. Sciatic nerve injury occurred in 2 cases (1 in each group, respectively), lower extremity deep venous thrombosis in 7 cases (3 in test group and 4 in control group), and hip joint dislocation in 2 cases (control group); the other patients had no related complications. The difference of relative leg-length and Harris score in test group were significantly better than in control group (P<0.05), and significant difference was also found when compared with preoperative one in 2 groups (P<0.05). The horizontal and vertical distances of actual and the true rotation center in test group was significantly better than those in control group at immediate after operation on the X-ray films (P<0.05); and significant differences were also found when compared with preoperative ones in 2 groups (P<0.05). At 6 months after operation, the absolute leg-length difference in test group was significantly better than that in control group (P<0.05); and significant difference was also found when compared with preoperative one in 2 groups (P<0.05). ConclusionThe fossae ovalis oriented acetabular centralized technology in THA can significantly correct abnormal hip center of rotation, thus reduce the relative and absolute leg-length inequality and improve the life quality of the patients.