[Biomechanical compensatory mechanisms of hips and spine : The essentials for spine and hip surgeons].

Spinal alignment changes with age and degeneration. Different compensatory mechanisms of the spine are necessary to preserve spinal balance. The capacity of compensation of the spine decreases with age. Thus, the pelvis and the lower limbs become involved in the compensatory mechanism. Concomitant osteoarthritis of the hip could impair this capacity. The biomechanical principles of compensation are described with respect to planning reconstructive hip and spine surgery.