Effect of a semi-rigid backpack type thoracolumbar orthosis on thoracic kyphosis angle and muscle performance in older adults with hyperkyphosis: a randomized controlled trial

Abstract

Purpose: To investigate the effect of a semi-rigid backpack type thoracolumbar orthosis (TLO) on thoracic kyphosis angle (TKA) and potentially contributing factors of hyperkyphosis, including position sense and back muscle strength and endurance.

Method: This randomized, controlled trial was conducted on 48 older adults with hyperkyphosis, randomly allocated to an experimental or control group. The experimental group wore a semi-rigid TLO for 3 consecutive months. The control group received no external support or exercise. Thoracic kyphosis angle (TKA), joint position sense, back muscle strength and endurance were evaluated at the baseline and at the end of week 6 and week 12.

Results: The two-way (group × time) interactions were significant in terms of TKA (F = 37.88, p ≤ 0.001, η_p² = 0.45), muscle strength (F = 26.005, p ≤ 0.001, η_p² = 0.36), muscle endurance measured via load cell (F = 3.417, p = 0.039, η_p² = 0.06), and endurance holding time of Ito test (F = 3.629, p = 0.045, η_p² = 0.07). A further analysis using one-way repeated measures of ANOVA showed that TKA, muscle strength and endurance were significantly improved in the experimental group. Also, two-way interactions were significant for absolute error and variable error of trunk neutral repositioning test from a trunk flexed and/or extended position for global components and horizontal components trunk repositioning test.

Conclusion: Wearing a semi-rigid backpack type TLO even from an unknown brand for short periods during the day (e.g., 2-4 h) over 3 months not only modifies kyphotic posture but also can enhance back muscle performance in older adults with hyperkyphosis. IMPLICATIONS FOR REHABILITATIONPrescription of a semi-rigid backpack type thoracolumbar orthosis for older adults has no adverse effects such as muscle weakness if it is applied for short periods during the day.A semi-rigid backpack thoracolumbar orthosis can prevent position sense degradation in older adults with hyperkyphosis.A semi-rigid backpack type thoracolumbar orthosis may counteract trunk flexion and kyphotic posture by applying the biomechanical principles of the three-point pressure system.Improvement in spinal alignment resulting from wearing thoracolumbar orthosis should not occur in exchange for muscle deconditioning.

Keywords: Hyperkyphosis; back muscles; muscle strength; position sense; postural deformity; proprioception; spinal orthosis.