Changes in acetabular component alignment due to screw fixation in patients with hip dysplasia.

INTRODUCTION: Adequate initial stability of the acetabular cup is essential for total hip arthroplasty (THA). However, changes in the alignment of the acetabular component caused by screw fixation are concerning in patients with inadequate bone stock. This study aimed to investigate the effects of screw fixation on the alignment of the acetabular component in THA patients with hip dysplasia. METHODS: We retrospectively examined 256 hips (range 28-87 years) that underwent THA using a navigation system. Patients were divided into 2 groups based on the presence or absence of changes in the alignment of the intraoperative acetabular cup, and univariate and multivariate analyses were performed to identify factors that were predictive of changes in acetabular component alignment after screw fixation in 2 dimensions: inclination and anteversion. RESULTS: Screw fixation led to a mean change in inclination of 1.6° (range 0-10°) and a mean change in anteversion of 1.4° (range 0-14°). The Crowe classification, the presence of bone cysts, and the use of an inferior quadrant screw were identified as factors that correlated with acetabular cup alignment changes in inclination (odds ratios, 6.01, 5.94 and 0.03, respectively). Only the Crowe classification was identified as a factor that correlated with intraoperative alignment changes in anteversion (odds ratio, 2.08). CONCLUSIONS: Screw fixation altered the acetabular cup alignment. The inclination changes were related to the extent of the dysplasia, and the risk was reduced when the inferior quadrant screw was used. Surgeons should use caution during screw fixation in THAs performed on severely dysplastic hips.

Predicting acetabular growth in developmental dysplasia of the hip following open reduction after walking age.

BACKGROUND: Acetabular dysplasia of the hip following open reduction can complicate the treatment of developmental dysplasia of the hip (DDH). The purposes of this retrospective study were to investigate the long-term results of open reduction performed via an extensive anterolateral approach for DDH after walking age and to predict acetabular development using postoperative radiographs and arthrograms. METHODS: From 1973 to 2001, we performed open reduction for 131 hips in 119 pediatric patients with DDH after failed closed reduction. Of these, 85 hips of 73 patients who underwent arthrography at 5 years old were followed-up radiologically until skeletal maturity. Mean age at the time of surgery was 17 ± 4.6 months (range, 10-33 months), and mean age at final survey was 19 ± 5.7 years (range, 14-33 years). Mean follow-up time was 17.7 ± 5.8 years (range, 13-32 years). Groups with satisfactory outcomes (66 hips) and unsatisfactory outcomes (19 hips) according to the Severin classification were compared. Factors predicting acetabular development were identified using univariate and multiple logistic analyses. RESULTS: Univariate analysis showed a significant between-group difference in acetabular index (AI) at 2 months postoperatively, and in center-edge (CE) angle, cartilaginous AI (CAI), and cartilaginous CE angle at 5 years old (p < 0.05 each). In multiple logistic regression analysis, CAI at 5 years old represented a predictor of acetabular development after open reduction for DDH (odds ratio, 1.81; 95% confidence interval (CI), 1.04-3.13; p < 0.05). Area under the receiver operating characteristic curve for CAI at 5 years old was 0.93 (95%CI, 0.85-1.0), and the optimal cut-off was 10° (81.8% sensitivity, 92% specificity). CONCLUSIONS: A CAI ≥10° on hip arthrograms at 5 years old may offer a useful indicator of the need for corrective surgery following open reduction after walking age.

Accuracy of Cup Positioning With the Computed Tomography-Based Two-dimensional to Three-Dimensional Matched Navigation System: A Prospective, Randomized Controlled Study.

BACKGROUND: The accuracy of various navigation systems used for total hip arthroplasty has been described, but no publications reported the accuracy of cup orientation in computed tomography (CT)-based 2D-3D (two-dimensional to three-dimensional) matched navigation. METHODS: In a prospective, randomized controlled study, 80 hips including 44 with developmental dysplasia of the hips were divided into a CT-based 2D-3D matched navigation group (2D-3D group) and a paired-point matched navigation group (PPM group). The accuracy of cup orientation (absolute difference between the intraoperative record and the postoperative measurement) was compared between groups. Additionally, multiple logistic regression analysis was performed to evaluate patient factors affecting the accuracy of cup orientation in each navigation. RESULTS: The accuracy of cup inclination was 2.5° ± 2.2° in the 2D-3D group and 4.6° ± 3.3° in the PPM group (P = .0016). The accuracy of cup anteversion was 2.3° ± 1.7° in the 2D-3D group and 4.4° ± 3.3° in the PPM group (P = .0009). In the PPM group, the presence of roof osteophytes decreased the accuracy of cup inclination (odds ratio 8.27, P = .0140) and the absolute value of pelvic tilt had a negative influence on the accuracy of cup anteversion (odds ratio 1.27, P = .0222). In the 2D-3D group, patient factors had no effect on the accuracy of cup orientation. CONCLUSION: The accuracy of cup positioning in CT-based 2D-3D matched navigation was better than in paired-point matched navigation, and was not affected by patient factors. It is a useful system for even severely deformed pelvises such as developmental dysplasia of the hips.

An Analysis of the Characteristics and Improved Use of Newly Developed CT-based Navigation System in Total Hip Arthroplasty.

We developed a surface matching-type computed tomography (CT)-based navigation system for total hip arthroplasty (the N-navi; TEIJIN NAKASHIMA MEDICAL, Okayama, Japan). In the registration step, surface matching was performed with digitizing points on the pelvic bone surface after coarse paired matching. In the present study, we made model bones from the CT data of patients whose acetabular shapes had various deformities. We measured the distances and angles after surface matching from the fiducial points and evaluated the ability to correct surface-matching registration on each pelvic form, using several areas and numbers of points. When the surface-matching points were taken on the superior area of the acetabulum, the correction was easy for the external direction, but it was difficult to correct for the anterior and proximal directions. The correction was difficult for external and proximal directions on the posterior area. Each area of surface-matching points has particular directions that are easily corrected and other directions that are difficult to correct. The shape of the pelvis also affected the correction ability. Our present findings suggest that checking the position after coarse paired matching and choosing the surface-matching area and points that are optimal to correct will improve the accuracy of total hip arthroplasty and reduce surgical times.

Residual Femoral Deformity and Femoroacetabular Impingement after Intertrochanteric Osteotomy for Slipped Capital Femoral Epiphysis.

We retrospectively reviewed 29 hips in which intertrochanteric osteotomies were performed for severe slipped capital femoral epiphyses. Mean age at surgery: 12.6 years. Mean follow-up period: 6 years. At the final follow-up evaluation, one patient had coxalgia, and six hips showed a limited range of motion. A pistol-grip deformity was observed in 13 hips, osteoarthritis in two hips, and a bump existed in 19 hips on the latest radiographs. Gradual remodeling of the bumps was observed post-operatively in 22 hips. The mean α and ß angles and offset α and ß improved over time. The remodeling proceeded rapidly for 1 year post-surgery. We compared hips classified as ß angles of ≥ 63° to < 63° at the final follow-up evaluation, the mean ß angle 1 year post-surgery, and the mean ratio of improvement of the ß angle per year from 1 year post-surgery to the final follow up, which differed significantly. Nearly all of the patients who underwent intertrochanteric osteotomies had residual morphologic abnormalities, but few had clinical symptoms. The ß angle 1 year post-surgery and the ratio of remodeling of the bump from 1 year post-surgery to the final follow-up can be regarded as a potential predictor of morphologic results after intertrochanteric osteotomy.

Acetabular development after open reduction to treat dislocation of the hip after walking age.

BACKGROUND: Treatment of hip dislocation diagnosed after walking age is often difficult. We report the surgical treatment of these patients by open reduction with a soft tissue surgical procedure without osteotomy. METHODS: Thirty-eight children (43 hips) diagnosed with complete dislocation of the hip after walking age were included in this study. We radiographically analysed postoperative hip joint development up to 6 years of age. To assess the predictors of acetabular development, we evaluated the radiographs, using an acetabular index of ≤35° and a centre-edge angle of >5° at 6 years of age as satisfactory outcomes, and evaluated the advance of acetabular development over time. RESULTS: AI on the affected side was improved with time after open reduction. The diameter of the capital femoral ossific nucleus on the affected side was almost equivalent to that on the unaffected side at 6-12 months after surgery, after which the centre-edge angle improved gradually from one year after surgery. We compared hips classified as satisfactory to unsatisfactory at 6 years of age, and found that the centre-edge angle at one year after open reduction was significantly associated with acetabular development (P = 0.044). The cut-off value was -2° with sensitivity of 0.909 and specificity of 0.677. CONCLUSIONS: The results of the current study suggest that initial development of the capital femoral ossific nucleus after open reduction would be followed by improved joint congruity, and that this would facilitate acetabular development. The centre-edge angle at one year after surgery could be regarded as a potential predictor of acetabular development in open reduction surgery for late-diagnosed developmental dysplasia of the hip cases.