Proximal Femoral Growth Alterations Can Be Seen Prior to Treatment of Developmental Dysplasia of the Hip: A Multicenter Cohort Study

Abstract

Background: Avascular necrosis (AVN), better considered proximal femoral growth disturbance (PFGD), following treatment for developmental dysplasia of the hip (DDH) remains poorly defined. In addition to limited reliability, it has been our experience that some radiographic features attributed to AVN/PFGD may be present prior to surgery. The purpose of this study was to determine the baseline prevalence of radiographic features suggestive of PFGD in a diverse cohort of patients with surgically treated DDH.Methods: The prospectively collected database for an international multicenter study group was retrospectively queried for patients who underwent surgery for DDH with minimum 1-year radiographic and clinical follow-up. Preoperative radiographs were evaluated for findings typically used to define PFGD at follow-up. Development of actual AVN/PFGD was determined by consensus review of follow-up radiographs by three experts separate from this study. These experts (KM, CP, WS) were specifically selected by the study group to evaluate all patients in the database for development of AVN/PFGD. This occurred prior to the conception of this study.Results: 145 patients were evaluated, with median preoperative age of 16.8 months (IQR:10.7-25.60). The proportion of patients with initial International Hip Dysplasia Institute (IHDI) grades of 2, 3, or 4 was 18%, 32%, and 50%, respectively. Prior to surgery, 20 hips (14%) had a heterogenous or “fragmented” epiphysis. Eight of the 145 epiphyses (6%) were significantly ellipsoid in shape. Depending on the definition, between 5-10% of hips had a wider neck at baseline compared to the contralateral, normal hip. At final follow-up, 42% of the hips were determined to have PFGD based on consensus review. Of all the patients that were considered to have PFGD at follow-up, 59% of patients had one feature of PFGD at baseline, and 20% had two or more.Conclusions: The current study suggests that several factors used to define the development of PFGD following DDH surgery may be present prior to surgical intervention. Our data demonstrates that 20% of the patients who develop AVN have at least two markers of PFGD, per Salter criteria, prior to receiving any treatment. This suggests that some of these hips may not be morphologically “normal” at baseline and adds to the mounting body of evidence about the limitations of the Salter classification for AVN.Level of Evidence: Level 2 - Prospective cohort study Key Concepts•Avascular necrosis classification systems in infantile DDH historically have had limited reliability and can be better thought of as proximal femoral growth disturbance (PFGD).•Our study demonstrated that approximately 20% of the patients who were found to have postoperative PFGD/AVN actually had signs of proximal femoral growth disturbance prior to surgery.•These findings suggests that some hips undergoing surgery for DDH may not be morphologically “normal” at baseline and add to the mounting body of evidence about the limitations of the Salter classification for AVN.