Long Term Results Of Avascular Necrosis Following Early Open Reduction And Salter Innominate Osteotomy In Development Dislocation Of The Hip

Objective:To retrospectively evaluate the long-term results of open reduction and Salter innominate osteotomy for the treatment of developmental dysplasia of the hip. To analysis the possible related factors with avascular necrosis of the femoral head after surgery and the long-term effect of the avascular necrosis.Materials and methods:From1992to2001, we performed82open reduction and Salter osteotomy (without proximal femur osteotomy) in64patients with developmental dysplasia of the hip. The contralateral side had undergone simultaneous open reduction and Chiari or Dega acetabuloplasty in seven patients who had bilateral involvement were excluded from this research. Five patients (seven hips) who had had prior conservative treatment and two patients (two hips) whose hip dysplasia were due to neuromuscular disease were not included as well.57cases (66hips) met the inclusion criteria,7patients (8hips) lost follow up, and6patients (7hips) had received reversion surgery due to residual dysplasia or hip subluxation.44patients (51hips) were evaluated in this research. All hips had had reached skeletal maturity at last follow up.The patients were divided into osteonecrosis-absent and osteonecrosis-present groups according to the radiographic results with criteria described by Bucholz-Ogden. Difference of preoperative parameters and surgical technique factors in two groups were analysed to find out the association between these factors with avascular necrosis of the femoral head after surgery. Preoperative parameters included age at operation, gender, laterality, unilateral or bilateral involvement, dislocation grade according to Tonnis classification. Surgical technique factors were Shenton’s line immediately after operation, obvious separation at ostotomy site, acetabular index before and after surgery. The final radiographs results such as center-edge angle (CE angle), Sharp angle, neck shaft angle and percentage acetabular head index were available for evaluation, as were the association with Severin radiographic classification results and functional results according to Mckay criteria.Results:The mean age at last follow up was15years and1month (range from13 years1month to22years4months). The mean duration of follow-up was12years and3months (range from10years3month to19years4months). Thirty patients (thirty-two hips) were classified as not having osteonecrosis (the osteonecrosis-absent group) and nineteen patients (nineteen hips) as having osteonecrosis (the osteonecrosis-present group). The age at surgery was29.2months and28.4months in the osteonecrosis-absent group and the osteonecrosis-present group respectively. In the osteonecrosis-absent group, there were six boys (seven hips) and twenty-four girls (twenty-five hips), eighteen had left involvement, unilateral and bilateral involvement was nineteen and eleven respectively. While in the osteonecrosis-present group, there were three boys (three hips) and sixteen girls (sixteen hips), eleven had left involvement, unilateral and bilateral involvement was eleven and nine respectively.Statistical analysis (chisquare test and t-test) of the preoperative parameters and surgical technique factors in two groups were performed and showed that there were no significant differences between the two groups in terms of preoperative parameters such as age, gender, laterality, Tonnis grade and surgical technique factors. Multivariable logistic regression analysis was used to evaluate the preoperative parameters and surgical technique factors with the final results and none preoperative or intraoperative parameters showed significant difference at p=0.05level when preoperative and intraoperative factors were analysed respectively. On the contrary, when preoperative and intraoperative factors were analysed as combined factors, none of preoperative parameters showed significant association at p=0.05level, but one intraoperative parameter acetabular index change (AI change) showed significant association with avascular necrosis of the femur head. The risk of avascular necrosis of the femur head after surgery was higher if AI change value was increased.Statistical analysis of the radiographic results at last follow up in two groups were performed and showed that there were no significant differences between two groups in terms of center-edge angle (CE angle), Sharp angle, neck shaft angle and percentage acetabular head index. Severin classification results and Mckay functional results had significant differences between two groups. Patient in osteonecrosis-absent group tended to have excellent or good radiographic and functional results while patients in osteonecrosis-present group tended to have fair or poor results.Conclusions:Our results showed no significant correlation between preoperative parameters such as gender, age, laterality, unilateral or bilateral involvement, Tonnis grade and the development of avascular necrosis of femur head after simultaneous open reduction and Salter innominate osteotomy. Intraoperative parameter acetabular index change (AI change) had significant correlation with the development of avascular necrosis of femur head. The risk of avascular necrosis of the femur head was higher if AI change value was increased, indicating that excessive reduction and hip joint contact pressure may play important role in the development of avascular necrosis of the femur head after surgery. Patient in osteonecrosis-present group tended to have worse radiographic and functional results.