**1. Introduction**

Scoliosis is a three-dimensional spinal deformity with a lateral curvature in excess of 10°. Adult scoliosis refers to scoliosis after skeletal maturity. It can arise from a wide range of conditions, including neuromuscular diseases, metabolic diseases, trauma, etc. Most commonly, the condition includes adult idiopathic scoliosis and degenerative lumbar scoliosis (DLS) [1–3], which are discrete conditions. Sometimes they coexist and are difficult to distinguish.

Adult scoliosis is increasing in importance in recent years, as its prevalence is increasing, as a result of increased life expectancy of the population [2, 3]. Adult scoliosis with thoracolumbar and lumbar curves is associated with a higher prevalence of low back pain. Also, they tend to progress. Many adult AIS patients consult because of the progression of their curves or of symptoms that decrease their quality of life inducing functional impairment [4]. Thoracolumbar curves receive the highest percentage of surgical treatment among adult coronal deformities; it accounted for 32.6% of all surgeries for adult scoliosis [5].

Apart from causing low back pain, thoracolumbar and lumbar curves tend to progress. Weinstein and Ponseti showed that 68% of the AIS curves progressed after skeletal maturity, especially when the Cobb angle exceeds 30° [6, 7]. In a retrospective study on progression of adult scoliosis, Marty-Poumarat et al. found that curves in adult AIS as well as DLS patients' progress, irrespective of the initial Cobb angle [8]. The rate of progression for lumbar or thoracolumbar single curve was 0.82°/year (0.34–1.65°) for adult AIS patients and 1.64°/year (0.77–3.82°) for DLS patients, respectively. Similarly, Iida et al. reported that AIS patients with thoracolumbar and lumbar curves (Lenke 5C) with a Cobb angle over 30° have a high risk of progression [9].

Symptomatic adult scoliosis patients are generally treated conservatively by NSAIDs, analgesics, manipulation, acupuncture, and electrotherapy [10]. These conservative treatments have not been found to be effective [11]. Everett and Patel found a low level of evidence in support of conservative treatment. They identified level IV evidence for physical therapy, chiropractic care, and bracing and level III evidence for steroid injections [11]. Similarly, Glassman et al. assessed the cost associated with nonsurgical treatment of adult scoliosis and found that despite the substantial mean cost of US\$10,815 per patient, there was no improvement in any HRQOL (Health-Related Quality of Life) measure over 2-year follow-up [12].

The unsatisfactory outcome of the treatment approach is possibly due to the fact that it targets at the symptoms of the adult scoliosis, but not the spinal deformities which are the one of the causes of the symptoms. The present study attempts to investigate whether Schroth best practice (SBP) exercises, which have been found to improve curves in AIS patients [13–18], do affect thoracolumbar and lumbar curves in adult scoliosis patients.
