LAUSR

With interest I read the article by Le Huec and Hasegawa [1] describing a meticulous study in which they used EOS low-dose full spine X-rays (EOS Imaging, Paris, France) to provide 3D information about standing spinopelvic reference values in Caucasian and Japanese subjects without back pain. Such novel methods, employing 3D radiography (very low X-ray dose, real size of the images, standing position, 3D and 2D clinical parameters, which are automatically calculated from 3D models), allow overcoming some limitations of previous similar studies. The comparison of Le Huec’s regression models with previously published models showed that calculation of lumbar lordosis (LL) based on pelvic incidence (PI) from Schwab’s equation was similar for subjects with low PI; nevertheless when PI was medium or high, the model of Schwab overestimated the LL [2]. The regression model from Legaye showed an overestimated LL also in subjects with low PI [3]. These differences could be related to the heterogeneity of Le Huec’s study population. The sagittal spinopelvic alignment of patients with hip disorders has been reported in a few studies [4–8]. Everyone agrees that any pathological changes in the spine, pelvis or legs modified the normal alignment. For this reason spine–pelvic–leg pathologies must always be excluded if the aim of the study is to provide information about reference values. Patients with HOA (hip osteoarthritis) have more anteverted pelvis, forward inclined spine and flexed hip joints, and a significantly greater risk of severe unbalance of sagittal spinal–pelvic alignment [9]. When the osteoarthritis (OA) is present, its grading is another important factor to consider. Patients with pre/early stage OA showed comparable lumbar lordosis and sagittal pelvic alignment, with a trend of greater anterior pelvic inclination [10]; patients with severe OA also had significantly anterior inclined pelvis (larger sacral slope) and hyperlordotic lumbar spine (larger lumbar lordosis) [11, 12]. Le Huec and Hasegawa do not consider the above observations recruiting patients between 18 and 76 years old without back pain while exclusion criteria must be ‘‘spine, pelvic, hip or lower limb disorders’’. In similar studies, subjects with a history of pain in the low back or hip for a minimum of 3 consecutive months were always excluded. At same time, it is hard to hypothesis that 20 and 60-year-old persons have the same hip function. Also spinal parameters differ through the aging; lumbar lordosis tends to decrease with aging process, as pelvic incidence remains constant for a given human being [13]. According to these considerations, data must always be ageand gender-matched to determine the theoretical ideal parameters. As such, these points are highlighted in the interest of other readers or researchers who may be interested to replicate the study in the near future. & Andrea Piazzolla [email protected]