Investigation of the Effect of Thoracic Kyphosis Proprioception

Although the negative effect of increased thoracic kyphosis in elderly individuals has been reported in the literature, the effect of the thoracic kyphosis angle on trunk and foot proprioception in young individuals has not been investigated. The aim of this study was to investigate the effect of the thoracic kyphosis on posture, proprioception and perception of postural appearance in young individuals.

The term kyphosis is defined as an increase in the anterior curvature of the spine in the sagittal plane. Along with cosmetic deformity, individuals may experience pain with movement, increased forward head posture, unequal shoulder levels and fatigue. Kyphosis occurs when people with insufficient general muscle strength are in an upright position and high external stress is applied to the spine. Kyphosis is frequently seen in young people and children due to the demands of their school programmes and prolonged and non-ergonomic sitting positions. The prevalence of thoracic kyphosis has been reported to be 15.3% in children aged 11 years, 35% in individuals aged 20-64 years, and 38% in individuals aged 20-50 years.

The ability to perceive body positions in space without visual inputs is determined by the proprioceptive sense. Proprioceptive data from muscles, ligaments and joints contribute to the awareness of the relative orientation of the functional units of the spine at rest and in motion, enabling the control of posture and balance. Since proprioception is fundamental for movement, posture and balance, joint position sensory information from the trunk is essential for the production of synchronised muscle contractions during spinal movements. Therefore, a decrease in proprioception information may lead to an increase in the degree of kyphosis. In the literature, a negative relationship between joint position sense and the angle of kyphosis of the thoracic region has been reported in elderly individuals with thoracic kyphosis. It has been suggested that alignment problems of the spine may be related to the lack of position sense.

Over time, young people may become accustomed to inappropriate postures and poor postural awareness. Changes in posture can lead to differences in the sense of touch. These differences consist of posture-related changes in the structural properties of the skin. When dorsal skin tension increases with spinal flexion, the tactile sensitivity threshold, the longitudinal spatial acuity threshold and the transversal stretch sensitivity threshold increase. In addition, the dorsal skin decreased the sensitivity threshold to longitudinal stretch stimuli, again due to spinal flexion-induced skin tension. This suggests that sensitivity to skin stretching in a direction parallel to the spine increases as individuals move from a normal position to flexion. Changes in the flexion and extension positions of the spine produce large changes in skin stiffness, tension and thickness.

Changes in posture affect the load distribution of the foot function. A shift in the body axis away from the midline causes asymmetric loading of the extremities and affects the disproportion of the postural muscles, thus shifting the centre of gravity. Changes in the position of the trunk with deviations in the centre of gravity cause changes in the plantar load distribution with the hip and ankle. Pressure in the plantar region stimulates receptors in that region. Sensory feedback from the plantar region is important for perceiving changes in postural position and controlling postural oscillations. Feedback from cutaneous mechanoreceptors contributes functionally to proprioception of postural position and support status. However, there is a relationship between the magnitude of the kyphosis angle and the distribution of lower extremity ground reaction forces. In this context, the distribution of plantar pressure affects the sensory sensitivity of the sole of the foot.

In the forward head posture, the flexion moment of the spine is increased by maintaining the weight of the head in front of the gravity line. There is a functional and mechanical correlation between kyphosis and a forward-head posture. This position of the head can lead to further postural deviations in the body, such as rounded shoulders and increased thoracic kyphosis, in order to compensate for the deviated gravity line. This leads to a vicious circle of further deformity. The angle of the shoulder and the craniovertebral angle are negatively correlated with the forward head position and positively correlated with the sagittal head angle.

Although the negative effect of increased thoracic kyphosis in elderly individuals has been reported in the literature, the effect of the thoracic kyphosis angle on trunk and foot proprioception in young individuals has not been investigated. The aim of this study was to investigate the effect of the thoracic kyphosis on posture, proprioception and perception of postural appearance in young individuals.

Eligibility Criteria:
Inclusion Criteria:

* Between 18 and 25 years of age
* Not being treated for kyphosis in the last 6 months

Exclusion Criteria:

* Those diagnosed with scoliosis and/or structural spinal deformity
* Those with any neurological deficit
* Those with concomitant disorders such as Scheuermann's disease, genetic diseases such as Beckwith-Wiedemann Syndrome or metabolic diseases that may affect body axis disorders
* Those with lower limb deformities
* Those with a history of spinal fracture and/or surgery and/or shoulder joint injury
* Those with mental disorders and intellectual disabilities.