3D-CT used to determine an optimal combined anteversion angle of femoral neck-acetabulum in total hip arthroplasty for adult hip developmental dysplasia

Objective To investigate how 3D-CT was used to determine an optimal combined an-teversion angle of femoral neck-acetabulum in total hip arthro (THA) for adult developmental dysplasia of the hip(DDH). Methods 3D-CT was used in 21 adult patients(21 hips) with DDH who had been treated by THA from March 2011 to March 2014. They were 5 men and 16 women, 30 to 78 years of age (average, 55.3 years). By the Crowe classification, there were 6 cases of type Ⅱ, 11 cases of type Ⅲ, and 4 cases of type Ⅳ. After all the patients underwent thin slice CT scanning, their primary 2-dimentional data were imported into M3D visual digitization software for 3-dimentional reconstruction. The 3D-CT images were used before each THA to find an optimal combined anteversion angle of femoral neck-acetabulum for the surgery. After surgery, the 3D-CT images were used to evaluate bony coverage of the acetabulum cup and the agreement between the combined anteversion angle of femoral neck-acetabulum determined preoperatively and the postoperative one. Harris scores were used to evaluate the efficacy of THA. Results The 21 patients were followed up for an average of 12.8 months (range, from 3 to 36 months). The Harris scores at the last follow-up revealed 17 excellent cases and 4 good ones. The preoperative Harris scores (46.2±5.3) increased significantly to 86.3±4.3 at the last follow-up (P<0.05). All the patients obtained bony coverage of the acetabulum cup of more than 70% . The agreement between the combined anteversion angle of femoral neck-acetabulum de-termined preoperatively and the postoperative one reached 95% . All the postoperative combined anteversion angles of femoral neck-acetabulum were in a safe range. No anterior dislocation was observed. Conclusions In a preoperative rehearsal of THA, 3D-CT reconstruction can be used to find an optimal combined an-teversion angle of femoral neck-acetabulum which may lead to the best bony coverage, the most initial sta-bility, the best match between the femoral head and the acetabulum, reduced prosthesis dislocation and in-creased prosthesis survival. Key words: Acetabulum; Arthroplasty, replacement, hip; Imaging, three-dimensional