Aims

This study aimed to evaluate the relationship between hip shape and mid-term function in Perthes’ disease. It also explored whether the modified three-group Stulberg classification can offer similar prognostic information to the five-group system.

We will report the clinical and radiographical results of a comparison between conservative and surgical treatment of Perthes disease after an average period of 25 years. All the children were observed at Orthopaedic and Traumatologic Center (CTO) of Florence between 1962 and 1989. Patients and Methods: Nineteen patients (20 hips) treated surgically using femoral and/or pelvic osteotomies and twenty patients (21 hips) treated conservatively with pelvi-podalic casts and no weight bearig were clinically (Harris Hip Score) and radiographically (Mose, Sharp, Stulberg criteria) evaluated after an average period of 25 years (16 to 43 years), by usig an A-P hip and pelvic view and a frog-leg view of both hips. All the children were radiographically evaluated using Catterall’s and Herring’s criteria. In the “surgical group” there were 10% of cases in the I, 30% in the II, 25% in the III and 35% in the IV group of Catterall classification. In the “conservative group” these percentages were 28%, 19%, 34% and 19% respectively. Results: In the surgical group 13 patients had an eccellent clinical result (100 to 90 points), 4 good (89 to 80), 1 fair (79 to 70) and 2 poor (< 70 points), with an average Harris Hip Score of 89,8 (57 to 100). In the conservative group there were 16 eccellent, 2 good, and 3 poor results, with an average Harris Hip Score of 98,5 (55 to 100). Using Stulberg’s criteria we had good results (I and II class) in 86% of the cases in the “conservative group” and 70% in the “surgical group”. Discussion: We correlated clinical and radiographical signs to find out if any of these sign can be predictive and we found that the most important factor was the age of symptom’s beginning. When symptoms started before 5 years old, 95% of the hips were in I and II class of Stulberg. After 5 years this percentage was only 64%. However we will report even the other clinical-radiographical correlations

The deformity index is a new radiological measurement of the degree of deformity of the femoral head in unilateral Perthes’ disease. Its values represent a continuous outcome measure of deformity incorporating changes in femoral epiphyseal height and width compared with the unaffected side. The sphericity of the femoral head in 30 radiographs (ten normal and 20 from patients with Perthes’ disease) were rated blindly as normal, mild, moderate or severe by three observers. Further blinded measurements of the deformity index were made on two further occasions with intervals of one month.

There was good agreement between the deformity index score and the subjective grading of deformity. Intra- and interobserver agreement for the deformity index was high. The intraobserver intraclass correlation coefficient for each observer was 0.98, 0.99 and 0.97, respectively, while the interobserver intraclass correlation coefficient was 0.98 for the first and 0.97 for the second set of calculations.

We also reviewed retrospectively 96 radiographs of children with Perthes’ disease, who were part of a multicentre trial which followed them to skeletal maturity. We found that the deformity index at two years correlated well with the Stulberg grading at skeletal maturity. A deformity index value above 0.3 was associated with the development of an aspherical femoral head. Using a deformity index value of 0.3 to divide groups for risk gives a sensitivity of 80% and specificity of 81% for predicting a Stulberg grade of III or IV.

We conclude that the deformity index at two years is a valid and reliable radiological outcome measure in unilateral Perthes’ disease.