Quantitative Evaluation of Upright Posture by X-Ray and 3D Stereophotogrammetry With an Original Marker Placement Protocol in Late Onset Pompe Disease.

Background: Late Onset Pompe Disease (LOPD) is an autosomal recessive muscular disorder characterized by prevailing weakness of trunk and pelvic girdle muscles that causes ventilatory insufficiency and postural abnormalities. The most common myopathy phenotype described clinically in LOPD is the Limb Girdle and Diaphragmatic Pattern; spinal deformities, as hyperlordosis, hyperkyphosis and scoliosis diagnosed by x-Ray exam, have been reported in about a third of LOPD patients. The non-specific clinic onset, the similarity of the LOPD phenotypes with other myopathies, inter-individual heterogeneity and the lack of any disease hallmark, make early diagnosis challenging and, if enzyme replacement therapy does not begin timely, about 60% of patients develops severe motor and ventilatory disabilities.Aim of our study was to quantitatively assess the upright posture in a sibship of LOPD adults by x-Ray(xR) and 3D Stereophotogrammetry (St), considered the gold standard to measure spinal angles and whole-body posture respectively, in order to better identify specific alterations more likely to be present in a homogeneous group.Results: Statistical analysis of St parameters showed a larger ankle, knee, elbow, dorsal, S2-C7, heel-S2-C7, heel-S2-nasion angles and a lower sagittal vertical axis (SVA) than healthy controls. Moreover, xR analysis highlighted a lower occipito-cervical, C2-C7 cervical and Cobb dorsal angles, and a trend to lower lumbar lordosis and SVA compared to normal values. Pearson’s coefficient analysis was carried on in order to evaluate the correlation between xR and St sagittal spino-pelvic parameters and significant correlation was found in dorsal and lumbar angles calculated using xR markers placed on spiny apophysis, xR centre of vertebral bodies, Cobb method and St markers. Conclusions: This is the first study that quantitatively assesses standing whole-body alignment and postural abnormalities in LOPD. These postural alterations are not easily detectable during clinical examination and might be useful to early identify LOPD patients and to facilitate differential diagnosis with other proximal myopathies. Moreover, our St-mks placement protocol showed high reliability to assess any sagittal angles and, being non-invasive as compared to xR, is advisable to investigate and monitor the course of the disease and the response to treatment.