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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. Our purpose was to determine the baseline prevalence of radiographic features suggestive of PFGD in a diverse population with surgically-treated DDH.
Methods: The prospectively collected database for an international multicenter study group was retrospectively queried for patients undergoing surgery for DDH with minimum one-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.
Results: 145 patients were evaluated, with median preoperative age of 16.8 months (IQR:10.7-25.60). The proportion of patients with initial 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.