Hypothesis about an existent biomechanical cause-effect relationship between Schëuermann's kyphosis and scoliosis.

Schëuermanńs kyphosis is usually observed with a mild idiopathic scoliosis, and there is parity between these two diseases. The aim of this work is to establish a hypothesis about the existence of a biomechanical causal relationship between Schëuermann's kyphosis and scoliosis. To achieve this, a literature review was conducted. A simple mechanical model of the passive thoracolumbar subsystem was created to support part of the discussion. This mechanical model describes the passive thoracolumbar subsystem under ideal conditions of equilibrium. After giving consideration to the system under these conditions, some of the geometrical changes that may be found in Schëuermanńs kyphosis are considered. Next, this work discusses the evolution of the spine, taking into account its relationship with stable equilibrium, which the passive subsystem tends toward. We hypothesized about the postural response of the body to compensate for possible situations of imbalance. In conclusion, it can be found that a change in the alignment of the spine may occur due to the postural adaptation of the body to an inadequate mechanical situation that may lead to scoliotic deformity of the spine.