ABSTRACT
Objective Based on the principle of uncemented stem design, the femoral anteversion in different CT planes before total hip arthroplasty (THA) and stem anteversion after THA was compared, so as to find out the preoperative measurement to estimate stem anteversion in patients with developmental dysplasia of the hip(DDH) after THA. Methods Twenty-one primary THA patients (28 hips) who were diagnosed with DDH between September 2007 and May 2013 in Shanghai Ninth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine were selected. Preoperative and postoperative CT scans were performed on all patients. The femoral anteversion angle was defined as the angle between the midcortical line between the anterior and posterior cortical line in five CT slices and the posterior condylar axis. The slice levels for the 4 femoral sites were selected，including the area just distal to the femoral head, the center of the lesser trochanter，1 cm height above center of the lesser trochanter, 2 cm height above center of the lesser trochanter (marked as femoral anteversion 1-4). Femoral anteversion 5 was defined as the midcortical line of the anterior cortical line in the slice of 2 cm height above center of the lesser trochanter and the posterior cortical line in the slice of 50% of the distance from the top of greater trochanter to the center of the lesser trochanter above the center of the lesser trochanter. The stem anteversion angle was defined as the angle formed by the stem neck major axis and the posterior aspect of the femoral condylar line. The cup version and stem alignment were also calculated. The difference value and correlation coefficients of femoral anteversion 1-5 and stem anteversion were compared. Results Femoral anteversion 1-5 was 17.70°±10.54°, 35.59°±7.21°, 31.09°±7.98°, 24.71°±9.11°, 21.94°±10.10°, respectively。Stem anteversion was 20.52°±10.90°. The difference value between stem anteversion and femoral anteversion 1-5 was 2.82°±6.27°, -15.08°±7.99°, -13.80°±15.68°, -4.19°±5.69°, -1.42°±4.07°, respectively. Cup anteversion was 25.60°±11.65°, and combined antevertion was 46.11°±13.28°，sagittal stem tilt was 1.13°±1.53°. There were statistically significant differences between femoral anteversion 1-4 and stem anteversion (P＜0.05), and no statistical difference was found between femoral anteversion 5 and stem anteversion. The correlation coefficients of femoral anteversion 1-5 and stem anteversion were 0.829, 0.681, 0.689, 0.853, 0.928, respectively. Conclusions Femoral anteversion 5 had a highly positive correlation with stem anteversion, which was an effective a substitute of stem anteversion before THA.
ABSTRACT
Objective Based on the principle of uncemented stem design, the femoral anteversion in different CT planes before total hip arthroplasty (THA) and stem anteversion after THA was compared, so as to find out the preoperative measurement to estimate stem anteversion in patients with developmental dysplasia of the hip(DDH) after THA. Methods Twenty-one primary THA patients (28 hips) who were diagnosed with DDH between September 2007 and May 2013 in Shanghai Ninth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine were selected. Preoperative and postoperative CT scans were performed on all patients. The femoral anteversion angle was defined as the angle between the midcortical line between the anterior and posterior cortical line in five CT slices and the posterior condylar axis. The slice levels for the 4 femoral sites were selected，including the area just distal to the femoral head, the center of the lesser trochanter，1 cm height above center of the lesser trochanter, 2 cm height above center of the lesser trochanter (marked as femoral anteversion 1-4). Femoral anteversion 5 was defined as the midcortical line of the anterior cortical line in the slice of 2 cm height above center of the lesser trochanter and the posterior cortical line in the slice of 50% of the distance from the top of greater trochanter to the center of the lesser trochanter above the center of the lesser trochanter. The stem anteversion angle was defined as the angle formed by the stem neck major axis and the posterior aspect of the femoral condylar line. The cup version and stem alignment were also calculated. The difference value and correlation coefficients of femoral anteversion 1-5 and stem anteversion were compared. Results Femoral anteversion 1-5 was 17.70°±10.54°, 35.59°±7.21°, 31.09°±7.98°, 24.71°±9.11°, 21.94°±10.10°, respectively。Stem anteversion was 20.52°±10.90°. The difference value between stem anteversion and femoral anteversion 1-5 was 2.82°±6.27°, -15.08°±7.99°, -13.80°±15.68°, -4.19°±5.69°, -1.42°±4.07°, respectively. Cup anteversion was 25.60°±11.65°, and combined antevertion was 46.11°±13.28°，sagittal stem tilt was 1.13°±1.53°. There were statistically significant differences between femoral anteversion 1-4 and stem anteversion (P＜0.05), and no statistical difference was found between femoral anteversion 5 and stem anteversion. The correlation coefficients of femoral anteversion 1-5 and stem anteversion were 0.829, 0.681, 0.689, 0.853, 0.928, respectively. Conclusions Femoral anteversion 5 had a highly positive correlation with stem anteversion, which was an effective a substitute of stem anteversion before THA.
ABSTRACT
PURPOSE: This study evaluated the effect of the implant position on a postoperative dislocation after total hip arthroplasty (THA) using computed tomography. MATERIALS AND METHODS: 1171 THAS were performed by one surgeon from March 1993 to September 1996, and from May 1998 to October 2004. There were 41 postoperative dislocations. Of these, 20 cases of the dislocated group and 20 cases of the control group were available for CT to check the acetabular and femoral anteversion of the implanted prostheses. Both groups were matched according to the type and size of the prosthesis, patient factors, and the surgical approach in order to eliminate the possible effect of these factors on a dislocation. All dislocations involved in this study occurred posteriorly. The cup anteversion, stem anteversion, acetabular inclination, vertical off-set, horizontal off-set and leg length discrepancy were measured using the CT and conventional radiographs on the PACS system. RESULTS: The cup anteversion was significantly lower in the dislocated group than in the non-dislocated group (p<0.001, chi-square test) respectively. The other variables were not different significantly in both groups. CONCLUSION: These findings suggests that among the variables of the implant positions, cup anteversion is the most important risk factor for a posterior dislocation after THA.