Fig. 3

Anteroposterior view of a pelvic X-ray is a mirror reflecting different condition of hip-spine complex. A Bilateral femoral avascular necrosis with a normal pelvis orientation and physiological hip-spine relation, which constitutes low risk in THA. B Bilateral hip dislocation and osteoarthritis resulted from DDH with an extremely anteverted pelvis and hypermobile hip-spine relation, which constitutes high risks of instability, dislocation and mechanical loosening in THA. C Hip involvement of ankylosing spondylitis with an extremely retroverted pelvis and stiff hip-spine relation, which constitutes high risk of impingement, wear failure, and dislocation in THA. D Hip osteoarthritis secondary to degenerative lumbar disease with moderately retroverted pelvis and stiff hip-spine relation, which constitutes high risk of impingement, dislocation and abnormal gait in THA. E An illustrative manifestation of pelvis in lateral view showing neutral, retroverted and anteverted pelvis in above hip pathologies