Post-operative radiograph assessment of children undergoing closed reduction and spica cast immobilization for developmental dysplasia of the hip: does experience matter?

Purpose: Closed reduction and spica cast immobilization are routinely used for young patients with developmental dysplasia of the hip with reducible hips. Our primary objective was to assess the interpretation quality of immediate post-operative pelvis radiographs after treatment. Methods: A series of 28 randomly selected patients (30 hips) with pre- and post-operative pelvis radiographs and post-operative magnetic resonance imaging were included. Each was presented twice with an interval of two weeks, in alternating orders. Raters with different experience and specialties from different institutions rated the quality of reduction (hip in or out) after treatment. Results: Thirteen surgeons and three radiologists evaluated 30 hips (28 patients). Agreement was not satisfactory (κ = 0.12). Experienced clinicians demonstrated similar agreement to inexperienced raters (κ = 0.04). Consistency at a two week interval was moderate (κ = 0.48, percent of agreement at 82%). The mean number of errors from the two ratings were 8.6 ± 2.5 and 8.9 ± 2.7, respectively (P = 0.72). There was no significant difference between surgeons with different levels of experience; radiologists did better than surgeons, but the difference was insignificant. Raters from different institutions had similar performance in poor judgment. Conclusions: Our results show poor concordance between observers and ratings. Post-operative radiographs are unreliable for assessing the quality of hip reduction. The level of experience, subspecialty, and geographical origin do not impact the radiographic assessment. Based on the present findings, we recommend performing post-operative magnetic resonance imaging rather than anteroposterior pelvis radiograph to assess the hip. Compared to standard radiographs, magnetic resonance imaging allows more reliable interpretation while decreasing radiation exposure.