Measurement Of Acetabular Index Research Articles

The Assessment of Acetabular Index

This is a series of 7 children (14 hips) with a mean age of 7.3 years (range, 3.3-10.5 years) and an underlying diagnosis of developmental dysplasia of the hips and no previous open-hip surgery who underwent plain radiographic and magnetic resonance imaging (MRI) measures of bony acetabular index. There was a significant correlation between the measurement of acetabular index using plain radiography and MRI, with a Spearman correlation coefficient of 0.88 (95% confidence interval, 0.61-0.96; P<0.001) and a mean difference between the 2 measures of 0.36+/-6.5 degrees. Furthermore, the bony and cartilaginous acetabular indexes as measured by MRI had a significant correlation with a Spearman correlation coefficient of 0.88 (95% confidence interval, 0.80-0.98; P<0.001). We suggest that plain radiography is still an appropriate tool for follow-up for the nonoperated hip with developmental dysplasia and may be a good indicator of hip cartilaginous development.

Arthroscopic-Assisted Surgical Treatment for Developmental Dislocation of the Hip

Treatment of developmental dislocation of the hip (DDH) includes surgical management in older children or in those who cannot be treated conservatively. However, complication rates of surgical treatment are quite high. The purpose of this report is to introduce our new surgical technique that can eliminate existing pathologic changes in DDH. A small case series. We performed arthroscopic-assisted surgical treatment in 4 hips of 4 female children who had DDH and no previous treatment. Their ages ranged from 11 to 14 months. Closed reduction under general anesthesia was tried just before the surgical intervention, but it failed in all of them. Tightness of the iliopsoas tendon was released followed by dissection of capsular adhesions using an anterolateral mini-incision. Excision of the hypertrophic ligamentum teres, transverse acetabular ligament, and pulvinar tissue was carried out using a double-portal arthroscopic procedure. We performed percutaneus adductor tenotomies in 2 cases. A spica cast and abduction splint were used for 12 to 17 weeks postoperatively. The follow-up of the patients was a minimum of 1 year. Although a 1-year follow-up period is adequate to evaluate the short-term results, it has been considered that there is a need for further studies that include long-term follow-up. We used the acetabular index and Shenton's line for preoperative and postoperative radiologic evaluation. Also, the cases were evaluated postoperatively in respect to range of motion restriction and the leg length discrepancy. The mean follow-up was 13.7 months (range, 12 to 16 months). Acetabular index measurements of the cases in the preoperative/postoperative periods were as follows: in the first case, 34 degrees/27 degrees; in the second case, 35 degrees/22 degrees; in the third case, 52 degrees/39 degrees; and in the fourth case, 40 degrees/28 degrees. Hip joint restriction and leg length discrepancy were not observed postoperatively. All the intra-articular structures (hypertrophic ligamentum teres, transverse acetabular ligament, and pulvinar tissue) in the acetabulum that impede the reduction of the femoral head have been eliminated by using the arthroscopic technique. The arthroscopic-assisted surgical treatment of DDH is successful in the short-term follow-up period. Level IV, Case Series.

The 'true' acetabular index in children with cerebral palsy

The acetabular index is a measurement used to determine whether or not an acetabular osteotomy may be required at the time of hip reconstruction in children. A retrospective analysis of pre- and postoperative values of the acetabular index was carried out on two groups of children. One group of children had an acetabuloplasty and the other did not during hip reconstruction, the decision being made at the time of open reduction, based on lack of hip congruity. When the pre-operative acetabular index measurements were reviewed, the mean difference between the two groups was only 7 degrees. Range of measurements was similar between the two groups. The acetabular index is difficult to measure in some children with cerebral palsy. The bony landmarks are difficult to standardise. This may explain the similar pre-operative values between the two groups of children in this study. We, therefore, recommend that before hip reconstruction in children with cerebral palsy, the measurement of the acetabular index should be abandoned. Decisions as to whether to undertake an acetabuloplasty or not should be made at the time of open reduction.

Ultrasonographic evaluation of the state of the hip joints in newborns

Two hundred fifty newborns (110 girls and 140 boys) were examined with ultrasonography. The method of acetabular index measurement was used to assess the hip joint status. High efficacy of sonography in differentiation of true and false-positive Marks-Ortholani symptom was noted. High correlation between sonography data and radiography ones was detected. Absence of irradiation, possibility of examination in real time and repeated examinations make sonography one of the main methods for hip joint screening.

Variability in Measurement of Acetabular Index in Normal and Dysplastic Hips, Before and After Reduction

This study examined the variability in the measurement of the acetabular index (AI) in normal and dysplastic hips, both before and after reduction. This variability for dysplastic hips is greater than that of normal hips. The variability is greater before an open or closed reduction than after reduction, and the variability after an open reduction is nearly 3 times greater than after a closed reduction. The 95% confidence interval of the AI is 10.1 degrees intraobserver and 21.9 degrees interobserver for all hips. The AI is most accurate in the situation in which it is most useful, after a closed reduction of a dysplastic hip. A 95% confidence interval of 5.1 degrees in this selected population supports the use of the AI for monitoring acetabular remodeling after closed reductions in accordance with previous clinical recommendations.

Errors in measurement of acetabular index.

Errors in determining the acetabular index can be induced either by incorrectly positioning the child for radiographs or by inter- or intraobserver errors. From postmortem radiographic studies, we have determined the magnitude of these errors. The error caused by pelvic rotation is +/- 3 degrees if the obturator foramina ratio is kept within 0.5 to 2. If pelvic flexion/extension is confined to +/- 10 degrees, the error induced by flexion/extension is +/- 3 degrees. The intraobserver error was +/- 2 degrees, and the interobserver error was +/- 3 degrees. Under these circumstances, the total error is +/- 5 degrees. We have not been able to find a satisfactory way of limiting the flexion/extension to +/- 10 degrees. In some circumstances, particularly if a child is distressed, the flexion/extension may be 20 degrees from neutral; under these circumstances, errors as large as 10 degrees can occur. Surgeons should be aware that very large errors can occur when the acetabular index is measured.

Dislocation of the hip in cerebral palsy. Natural history and predictability

To determine the natural history of dislocation of the hip in cerebral palsy, and to evolve methods to predict dislocation, the notes and radiographs of 462 patients with cerebral palsy were reviewed. Dislocation occurred in 10% of patients by progressive migration and subluxation of the proximal femur in the presence of acetabular dysplasia. Statistical analysis identified the radiographic features that helped to predict dislocation. Measurement of acetabular index, by a method that allows for rotation of the acetabulum, was the most powerful single predictor. Measurement of this index at two and four years of age could identify patients who would dislocate unless effective treatment was undertaken, those at risk of dislocation only if scoliosis developed, and those who would not dislocate. On the basis of this method of screening for dislocation, a logical system of surgical prophylaxis is proposed.

Reliability of radiological measurements in the assessment of the child's hip.

We investigated the reproducibility of the various radiological methods of assessment of hip dysplasia by making 474 assessments of hips and quantifying the inter-observer and intra-observer variation. There was a wide range of variability between the readings made by different observers and by one observer on two occasions. A measurement of acetabular index has to be given a range of +/- 6 degrees in order to be 95% confident of including the true measurement. We found the most helpful measurements to be the acetabular index, up to the age of eight years; the centre-edge angle, over the age of five years; and Smith's c/b ratio and neck-shaft angle. We feel, however, that the change in value over a series of radiographs in the same child is much more valuable. Single readings of all the radiological measurements investigated in this study were unreliable.