Though the pathogenesis of Legg-Calve-Perthes disease (LCPD) is unknown, repetitive microtrauma resulting in deformity has been postulated. The purpose of this study is to trial a novel upright MRI scanner, to determine whether any deformation occurs in femoral heads affected by LCPD with weightbearing. Children affected by LCPD were recruited for analysis. Children received both standing weightbearing and supine scans in the MROpen upright MRI scanner, for coronal T1 GFE sequences, both hips in field of view. Parameters of femoral head height, width, and lateral extrusion of affected and unaffected hips were assessed by two independent raters, repeated at a one month interval. Inter- and intraclass correlation coefficients were determined. Standing and supine measurements were compared for each femoral head.Aims
Methods
This pilot study aims to investigate the utility and feasibility of a unique upright MR scan for imaging hips affected by Legg-Calve-Perthes Disease (LCPD) with patient standing up, in comparison to the standard supine scans. Protocol development using this unique upright MRI included healthy adult and child volunteers. Optimum patient positioning in a comparable way between supine to standing was assessed. The balance between shorter scan time (to what a child can tolerate) and longer scan time (for better image acquisition). The study protocol has begun in 2 children with LCPD. Patient recruitment continues. Early results indicate a dynamic deformity of the femoral head in early stage LCP disease. Femoral epiphysis height decreased on standing (7.8 to 6.8mm), width increased on standing (16.6 to 20.9mm) and lateral extrusion increased (3.5 to 4.1mm). Overall epiphyseal shape changed from trapezoidal (LCP femoral head when supine) to flattened triangular (LCP femoral head when standing). Differences were thus demonstrated in all parameters of bony epiphyseal height, width, extrusion and shape of a femoral head with LCP Disease when the child stood and loaded the affected hip. Satisfactory image acquisition was possible with Coronal T1 GFE sequences, with both hips in the Field of View. 2.5min scans were performed with the child standing first, then supine. Hip position was comparable when standing and supine. Longer scans were not tolerated by younger children, more so those with LCP disease. To our knowledge this is the first reported use of standing MRI in LCPD. A dynamic deformity has been demonstrated, with flattening, widening and worsened lateral extrusion when the child is standing compared to supine. This proof of concept investigation demonstrates the feasibility of upright MRI scanning and may demonstrate previously undetected deformity.
We studied the natural history of Perthes’ disease in 62 children in whom the onset of symptoms was in adolescence. Three patterns of disease were noted, namely, late-onset pattern, segmental collapse, or destructive with failure of revascularisation. In the late-onset pattern, the disease followed the sequence of healing seen in younger children, but adequate epiphyseal remodelling did not occur. Consequently, the femoral head was never spherical after revascularisation. With segmental collapse, early and irreversible collapse of part of the epiphysis occurred with gross deformation of the femoral head. The destructive pattern was characterised by a failure of revascularisation and repair of the avascular epiphysis. The radiological outcome was poor in all three patterns. The poorest clinical results were found in the destructive type which was frequently associated with incapacitating pain requiring arthrodesis or excision arthroplasty within three years of onset of the disease.
