Purpose or Case Report: SPICA MRI with gadolinium contrast administration is routinely performed after closed reduction for the treatment of developmental dysplasia of the hip (DDH). Quantifying the degree of femoral head enhancement and abduction angles are routinely performed to identify and stratify those patients who may be at risk for epiphyseal osteonecrosis. The purpose of our study is to evaluate predictors for epiphyseal osteonecrosis based on percentage enhancement and abduction angles evaluated based on SPICA MRI.
Methods & Materials: Retrospective descriptive study for all patients identified through text word query through our electronic medical record who underwent closed hip reduction for the treatment of DDH followed by gadolinium enhanced MRI between 7/11 and 11/14. Patient demographics were recorded and follow-up data inclusive of development of epiphyseal osteonecrosis and need for re-intervention after the initial reduction. MRI data recorded included hip abduction angles after the initial closed reduction and percentage of femoral head enhancement.
Results: 25 hips in 21 patients (16 female, 5 males, mean age 0.99 years, range 0.4-3.1 years) were included in our study. The mean follow-up period was 2.7 years (range 0.7-5.1 years). 8 of 25 hips (32%) went on to develop osteonecrosis. The development of epiphyseal osteonecrosis was more likely with <80% enhancement (sensitivity 87.5%, specificity 88.25%, positive predictive value 78%, negative predictive value 94%). The mean contrast enhancement for patients developing osteonecrosis compared to those who did not was 37.5% and 86.5% respectively; p=0.001. The development of epiphyseal osteonecrosis trended, but was not statistically significant when the abduction angle was greater than 55 degrees (P=0.1). The odds of osteonecrosis is 9% lower with every 1% increase of perfusion. There were 3 hips (12%) that underwent re-intervention based on the immediate post-reduction SPICA MRI results. For this subset, one (33%) went on to develop epiphyseal osteonecrosis.
Conclusions: Immediate post-SPICA MRI with gadolinium is a useful prognostic tool for determining future risk for epiphyseal osteonecrosis in children treated for DDH. Our data complements existing literature, and suggests that even in cases where there may be partial epiphyseal enhancement, epiphyseal osteonecrosis may still develop which has not been well explored in the literature. When epiphyseal enhancement is less than 80%, it is recommended that SPICA cast revision be considered.