Adolescent idiopathic scoliosis (AIS) is a three-dimensional complex deformity of the spine characterized by lateral deviation of 10 degrees or more in the frontal plane, rotation in the transverse plane and hypokyphosis in the sagittal plane. It has been reported that in the presence of scoliosis, there is a change in muscle strength of people compared to their healthy peers due to the deterioration of their postural balance. There are many studies in the literature that evaluate the muscle strength of cases diagnosed with scoliosis with objective devices. Among these objective devices, reliability studies on hand dynamometry devices, which are easy to use, portable and cheaper than other devices, have been conducted for different populations. However, no reliability study of the handheld dynamometer device in patients with AIS has been found in the literature. Therefore, the aim of our study is to study the intra-rater and inter-rater reliability and validity of the trunk flexion, extension and lateral flexion muscle strengths of the hand dynamometer device in cases with AIS, which are known to have changes in muscle strength compared to their peers as a result of the change in spinal alignment. After obtaining the demographic information of the cases that meet the inclusion criteria within the scope of the study, the isometric muscle strength of the trunk flexor, extensor and right-left lateral flexor muscles will be evaluated by two different evaluators using a Lafayette hand dynamometer. To avoid systematic error, each participant will perform the isometric handheld dynamometer protocol in a random testing order. In order to determine interobserver reliability, on the first day of the test, the same hand dynamometer protocol will be applied to each participant by two different evaluators, after a 1-hour rest to prevent fatigue. To determine intraobserver reliability and compliance, participants will be re-evaluated by the same researchers at the same protocol, place and day period, 1 week apart to prevent learning effects. This study will reveal the intraobserver and interobserver reliability and validity of the handheld dynamometer device, which can be used in the evaluation of trunk muscle strength for clinicians working with AIS.

Adolescent Idiopathic Scoliosis (AIS) is a three-dimensional complex deformity of the spine characterized by lateral deviation of 10 degrees or more in the frontal plane, rotation in the transverse plane and hypokyphosis in the sagittal plane, and is an important public health problem with a global prevalence of 0.47-5.2%. Muscle strength is an important factor in maintaining postural balance in AIS, and it is observed that both clinicians and researchers evaluate the muscle strength of cases with AIS using different objective devices. Objective muscle strength assessment methods include electromyography, hand dynamometry and isokinetic dynamometry. Electromyography devices and isokinetic dynamometers are expensive and their use in the clinic is limited because they are not easily portable. Therefore, it has been shown to be a valid and reliable method to evaluate trunk muscle strength in different populations and pathologies such as healthy adults, healthy athletic individuals, chronic low back pain or hemiplegic patients; The handheld dynamometer device, which has the advantage of being cheaper and more portable than other devices, appears as a suitable option for clinicians to evaluate trunk isometric muscle strength. No reliability studies of hand dynamometer devices have been found in the AIS population. Therefore, our aim in the study is to study the intra-observer and inter-observer reliability and validity of the trunk flexion, extension and lateral flexion muscle strengths of the hand dynamometer device in patients with AIS, who are known to have changes in muscle strength compared to their peers as a result of the change in spinal alignment. This study will reveal the validity of the hand dynamometer device that can be used in the evaluation of trunk muscle strength for clinicians working with AIS.

Inclusion Criteria:

• Being between the ages of 10-18
• Having been diagnosed with Adolescent Idiopathic Scoliosis by an orthopedic specialist
• Ability to understand instructions
• Volunteering to participate in the study

Exclusion Criteria:

• History of traumatic trunk or pelvic injury
• History of acute, subacute or chronic low back pain or neurological disease
• Having had spinal surgery
• Participating in heavy physical activity at least one day before the test days
• Having experienced any acute situation that could affect muscle strength between the two tests (within 7 days)

Adolescent idiopathic scoliosis patients