Bio-Medical Materials and Engineering 24 (2014) 453–458 DOI 10.3233/BME-130830 IOS Press
453
Inter-tester and Intra-tester Reliability of Ultrasound Imaging Measurements of Abdominal Muscles in Adolescents with and without Idiopathic Scoliosis: A Casecontrolled Study Hoe S. Yanga ,Ji W. Yoob ,Bo A. Leeb,Chang K. Choic,Joshua H. Youb∗ a
Department of Physical Therapy, Cheongam College, Sunchen City, Jeollanam-do, Republic of South Korea b Department of Physical Therapy, Yonsei University, Wonju City, Kangwon-do, Republic of South Korea c Choi Physical Medicine and Rehabilitation Clinic, Kurae Koon, Jeollanam-do, Republic of South Korea
Abstract. The present study established inter-tester and intra-tester reliabilities of ultrasound imaging and diagnostically differentiated muscle imbalances in lateral abdominal muscle sizes between normal adolescents and adolescents with idiopathic scoliosis(AIS). Fifteen adolescents with AIS were age- and gender-matched with 15 normal adolescents. There was no significant difference between bilateral abdominal muscles in normal adolescents, but there was a significant difference between bilateral abdominal muscles in adolescents with AIS (P< 0.05). Overall, inter-tester and intra-tester reliabilities in normal and AIS adolescents ranged from 0.801 - 0.984. This novel study shows that using ultrasound imaging to measure lateral abdominal muscle thickness is: (1) highly reliable between and within the testers; and (2) capable of distinguishing between subjects with and without pathological muscle morphology due to AIS. Keywords: Muscle thickness, Ultrasound imaging, Adolescent idiopathic scoliosis, Reliability
1. Introduction Ultrasound imaging techniques have recently gained widespread acceptance for its accuracy of diagnosing morphological muscle size changes and associated pathology [5, 6, 7, 13]and measuring progressive changes associated with rehabilitation and movement performance[4- 6]. Muscle size or ∗ Corresponding Author: Joshua (Sung) H. You, PT, PhD. 1) Professor, Department of Physical Therapy, Yonsei University; Director of Movement Healing Lab, 2) Mailing Address: 1 YonseidaeKil, Wonju City, Kangwon-do, Republic of South Korea 220-710 , 3) Tel: 033-760-2476; FAX: 033-760-2496; E-mail:[email protected] 0959-2989/14/$27.50 © 2014 – IOS Press and the authors. All rights reserved
454
H.S. Yang et al. / Inter-tester and Intra-tester reliability of ultrasound imaging measurements
thickness has been recognized as a critical biomarker for understanding pathogenesis of musculoskeletal impairments [4, 11] in adolescents with idiopathic scoliosis (AIS) [13]. AIS is a common, progressive, and three-dimensional musculoskeletal deformity in thoracic and/or lumbar spine in young adults [13] or athletes [10]. It is often associated with muscle imbalance in thickness and strength [13].Asymmetrical paraspinal muscle size in ultrasound imaging was found in AIS [11].More specifically, muscles were smaller on the concave side of the thoracic spine curvature and on the contralateral to the concavity in the lumbar or thoracolumbar spine curvature [11]. Nevertheless, it remains unknown whether such morphological imbalance exists in AIS. Therefore, the present investigation attempts to establish inter- and intra-tester reliability while ultrasound measurements are used to determine muscle thickness in the internal oblique (IO), external oblique (EO), and transverse abdominis (TrA) muscles in normal adolescents and adolescents with AIS. 2. Materials and methods 2.1. Participants A convenience sample of 30 female adolescents (15 healthy adolescents, mean age, 17.3 ± 0.4 years and 15 adolescents with idiopathic scoliosis, mean age, 17.5 ± 0.6 years) was recruited from a local co-mmunity high school. All participants provided written consent with procedures approved by the Institutional Review Board prior to their participation. AIS subjects were included according to Cobbs angles which is a scoliosis curve of 10°-15° or greater, or if the origins of scoliosis were related to musculoskeletal system impairment. AIS subjects were excluded if they had congenital or neuromuscular disorders (i.e. polio, muscular dystrophy, and cerebral palsy), current pregnancy, back pain, medication, integumentary and joint pathology (i.e., rheumatoid arthritis), brace, and a history of surgery, tumor, or kyphosis [13]. Healthy subjects were included if they were between 15-18 years old and determined to be healthy based on history and physical examination. Subjects were excluded if there were any significant structural abnormalities in spine, which may confound the results of the present experiment. 2.2. Imaging technique A real-time ultrasound SonoAce X4 was used with a 5-9 MHz convex linear array transducer (Medison Ltd, Seoul, Korea). HS and CK were the examiners, both of whom have 5-10 years of experience in ultrasound imaging. Neither of the examiners was blinded to the condition of the participants. Each participant was positioned in a relaxed hook-lying position [1]. The transducer head was transversely positioned 25 mm antero-medial to the midpoint between the 12thrib and the iliac crest [8, 9] so as to obtain the best image of all the lateral abdominal muscles (EO, IO, and TrA) [3]. To control for the potential influence of respiration on muscle thickness, images were consistently acquired at the end of the exhalation phase as determined by visual inspection of the ultrasound imaging [8]. The vertical marking line positioned 5 cm from the left musculofascial junction of the TrA muscle was consistently used to re-measure thickness for each muscle [8]. The vertical distance between the musculofascial layers represented individual thickness of EO, IO, and TrA muscles. Aiming to ensure the consistency in the ultrasound measurement, the same experimental protocol was utilized when re-measuring muscle thickness. Fig. 2 clearly illustrates the methods used to measure EO, IO, and TrA muscle thickness independently. An immediate readout of muscle thickness images
H.S. Yang et al. / Inter-tester and Intra-tester reliability of ultrasound imaging measurements
455
and data was presented on the computer screen and stored for further analysis. Inter-tester reliability was tested by comparing muscle thickness data of the same subject collected respectively by tester 1 (HS) and tester 2 (CK) using standardized ultrasound measurements at the same time of day .Intratester reliability was tested by examining repeatability for investigator HS across two repeated trials on the same day using ultrasound measurements previously described in the methods section.
Fig. 1. The Cobbs method was used to determine the degree of scoliosis on the anteroposterior radiograph.
Fig. 2. Ultrasound imaging illustrates compelling evidence for a distinct difference between bilateral external oblique (EO), internal oblique (IO), and transverse abdominal (TrA) muscles in adolescents with idiopathic scoliosis.
2.3. Data analysis Standard statistical analysis included calculating means, standard deviations, and intraclass correlation coefficients (ICC), as well as an independent sample t-test [12]. The minimum number
of measurements (N) which was needed to produce an ICC of 0.8 or 0.9 were computed using the Spearman-Brown formula, expressed as N= [ICCpredicted/expected (1-ICCobserved)] / [ICCobserved (1-ICCobserved)]. The computed ICCs of the measured EO, IO, and TrA muscle thickness
456
H.S. Yang et al. / Inter-tester and Intra-tester reliability of ultrasound imaging measurements
ranged from 0.85 to 0.98 and hence the minimum number of muscle thickness measurements was estimated to be “1” to adequately produce an ICC of 0.8 to 0.9. The 95% confidence interval (CI)and standard error of measurement(SEM)were computed for inter-tester reliability (ICC2.1) and intra-tester reliability(ICC3.1)using the ICC module in SPSS version 12.0 for Windows. P
453
Inter-tester and Intra-tester Reliability of Ultrasound Imaging Measurements of Abdominal Muscles in Adolescents with and without Idiopathic Scoliosis: A Casecontrolled Study Hoe S. Yanga ,Ji W. Yoob ,Bo A. Leeb,Chang K. Choic,Joshua H. Youb∗ a
Department of Physical Therapy, Cheongam College, Sunchen City, Jeollanam-do, Republic of South Korea b Department of Physical Therapy, Yonsei University, Wonju City, Kangwon-do, Republic of South Korea c Choi Physical Medicine and Rehabilitation Clinic, Kurae Koon, Jeollanam-do, Republic of South Korea
Abstract. The present study established inter-tester and intra-tester reliabilities of ultrasound imaging and diagnostically differentiated muscle imbalances in lateral abdominal muscle sizes between normal adolescents and adolescents with idiopathic scoliosis(AIS). Fifteen adolescents with AIS were age- and gender-matched with 15 normal adolescents. There was no significant difference between bilateral abdominal muscles in normal adolescents, but there was a significant difference between bilateral abdominal muscles in adolescents with AIS (P< 0.05). Overall, inter-tester and intra-tester reliabilities in normal and AIS adolescents ranged from 0.801 - 0.984. This novel study shows that using ultrasound imaging to measure lateral abdominal muscle thickness is: (1) highly reliable between and within the testers; and (2) capable of distinguishing between subjects with and without pathological muscle morphology due to AIS. Keywords: Muscle thickness, Ultrasound imaging, Adolescent idiopathic scoliosis, Reliability
1. Introduction Ultrasound imaging techniques have recently gained widespread acceptance for its accuracy of diagnosing morphological muscle size changes and associated pathology [5, 6, 7, 13]and measuring progressive changes associated with rehabilitation and movement performance[4- 6]. Muscle size or ∗ Corresponding Author: Joshua (Sung) H. You, PT, PhD. 1) Professor, Department of Physical Therapy, Yonsei University; Director of Movement Healing Lab, 2) Mailing Address: 1 YonseidaeKil, Wonju City, Kangwon-do, Republic of South Korea 220-710 , 3) Tel: 033-760-2476; FAX: 033-760-2496; E-mail:[email protected] 0959-2989/14/$27.50 © 2014 – IOS Press and the authors. All rights reserved
454
H.S. Yang et al. / Inter-tester and Intra-tester reliability of ultrasound imaging measurements
thickness has been recognized as a critical biomarker for understanding pathogenesis of musculoskeletal impairments [4, 11] in adolescents with idiopathic scoliosis (AIS) [13]. AIS is a common, progressive, and three-dimensional musculoskeletal deformity in thoracic and/or lumbar spine in young adults [13] or athletes [10]. It is often associated with muscle imbalance in thickness and strength [13].Asymmetrical paraspinal muscle size in ultrasound imaging was found in AIS [11].More specifically, muscles were smaller on the concave side of the thoracic spine curvature and on the contralateral to the concavity in the lumbar or thoracolumbar spine curvature [11]. Nevertheless, it remains unknown whether such morphological imbalance exists in AIS. Therefore, the present investigation attempts to establish inter- and intra-tester reliability while ultrasound measurements are used to determine muscle thickness in the internal oblique (IO), external oblique (EO), and transverse abdominis (TrA) muscles in normal adolescents and adolescents with AIS. 2. Materials and methods 2.1. Participants A convenience sample of 30 female adolescents (15 healthy adolescents, mean age, 17.3 ± 0.4 years and 15 adolescents with idiopathic scoliosis, mean age, 17.5 ± 0.6 years) was recruited from a local co-mmunity high school. All participants provided written consent with procedures approved by the Institutional Review Board prior to their participation. AIS subjects were included according to Cobbs angles which is a scoliosis curve of 10°-15° or greater, or if the origins of scoliosis were related to musculoskeletal system impairment. AIS subjects were excluded if they had congenital or neuromuscular disorders (i.e. polio, muscular dystrophy, and cerebral palsy), current pregnancy, back pain, medication, integumentary and joint pathology (i.e., rheumatoid arthritis), brace, and a history of surgery, tumor, or kyphosis [13]. Healthy subjects were included if they were between 15-18 years old and determined to be healthy based on history and physical examination. Subjects were excluded if there were any significant structural abnormalities in spine, which may confound the results of the present experiment. 2.2. Imaging technique A real-time ultrasound SonoAce X4 was used with a 5-9 MHz convex linear array transducer (Medison Ltd, Seoul, Korea). HS and CK were the examiners, both of whom have 5-10 years of experience in ultrasound imaging. Neither of the examiners was blinded to the condition of the participants. Each participant was positioned in a relaxed hook-lying position [1]. The transducer head was transversely positioned 25 mm antero-medial to the midpoint between the 12thrib and the iliac crest [8, 9] so as to obtain the best image of all the lateral abdominal muscles (EO, IO, and TrA) [3]. To control for the potential influence of respiration on muscle thickness, images were consistently acquired at the end of the exhalation phase as determined by visual inspection of the ultrasound imaging [8]. The vertical marking line positioned 5 cm from the left musculofascial junction of the TrA muscle was consistently used to re-measure thickness for each muscle [8]. The vertical distance between the musculofascial layers represented individual thickness of EO, IO, and TrA muscles. Aiming to ensure the consistency in the ultrasound measurement, the same experimental protocol was utilized when re-measuring muscle thickness. Fig. 2 clearly illustrates the methods used to measure EO, IO, and TrA muscle thickness independently. An immediate readout of muscle thickness images
H.S. Yang et al. / Inter-tester and Intra-tester reliability of ultrasound imaging measurements
455
and data was presented on the computer screen and stored for further analysis. Inter-tester reliability was tested by comparing muscle thickness data of the same subject collected respectively by tester 1 (HS) and tester 2 (CK) using standardized ultrasound measurements at the same time of day .Intratester reliability was tested by examining repeatability for investigator HS across two repeated trials on the same day using ultrasound measurements previously described in the methods section.
Fig. 1. The Cobbs method was used to determine the degree of scoliosis on the anteroposterior radiograph.
Fig. 2. Ultrasound imaging illustrates compelling evidence for a distinct difference between bilateral external oblique (EO), internal oblique (IO), and transverse abdominal (TrA) muscles in adolescents with idiopathic scoliosis.
2.3. Data analysis Standard statistical analysis included calculating means, standard deviations, and intraclass correlation coefficients (ICC), as well as an independent sample t-test [12]. The minimum number
of measurements (N) which was needed to produce an ICC of 0.8 or 0.9 were computed using the Spearman-Brown formula, expressed as N= [ICCpredicted/expected (1-ICCobserved)] / [ICCobserved (1-ICCobserved)]. The computed ICCs of the measured EO, IO, and TrA muscle thickness
456
H.S. Yang et al. / Inter-tester and Intra-tester reliability of ultrasound imaging measurements
ranged from 0.85 to 0.98 and hence the minimum number of muscle thickness measurements was estimated to be “1” to adequately produce an ICC of 0.8 to 0.9. The 95% confidence interval (CI)and standard error of measurement(SEM)were computed for inter-tester reliability (ICC2.1) and intra-tester reliability(ICC3.1)using the ICC module in SPSS version 12.0 for Windows. P
