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Effect of improved thoracic kyphosis on forward shoulder posture after mobilization in individuals with thoracic hyperkyphosis

  • Sung-hoon Jung
    Affiliations
    Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, College of Health Science, Yonsei University, Wonju, South Korea
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  • Ui-jae Hwang
    Affiliations
    Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, College of Health Science, Yonsei University, Wonju, South Korea
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  • Jun-Hee Kim
    Affiliations
    Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, College of Health Science, Yonsei University, Wonju, South Korea
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  • Gyeong-Tae Gwak
    Affiliations
    Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, College of Health Science, Yonsei University, Wonju, South Korea
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  • Oh-yun Kwon
    Correspondence
    Corresponding author at: 234 Maeji-ri, Heungeup-Myeon, Wonju, Kangwon-Do 26493, South Korea.
    Affiliations
    Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, College of Health Science, Yonsei University, Wonju, South Korea
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Open AccessPublished:June 17, 2022DOI:https://doi.org/10.1016/j.clinbiomech.2022.105707

      Highlights

      • Thoracic mobilization for 8 weeks proved forward shoulder posture.
      • The cutoff change ratio in kyphosis for improving forward shoulder posture was >13.8%.
      • Thoracic mobilization recommended in shoulder rehabilitation to improve shoulder posture.

      Abstract

      Background

      Thoracic hyperkyphosis structurally alters the position of the scapula to cause forward shoulder posture. However, the effect of improved thoracic hyperkyphosis on forward shoulder posture is unclear. The objective of this study was to determine the effect of eight weeks of thoracic mobilization on improving thoracic hyperkyphosis and forward shoulder posture and determine the cutoff change ratio in kyphosis for improving forward shoulder posture using the decision tree method.

      Method

      This study included 19 participants with thoracic hyperkyphosis who underwent thoracic mobilization for eight weeks. Forward shoulder posture (acromion-to-the-wall index) and thoracic kyphosis were measured before and after thoracic mobilization.

      Findings

      The intervention significantly improved thoracic kyphosis and forward shoulder posture. The cutoff change ratio in kyphosis for improving forward shoulder posture was >13.79%. In the subgroup analysis of participants with a change ratio of kyphosis >13.79% (seven cases), all patients showed improved forward shoulder posture. In contrast, in the subgroup with a change ratio of kyphosis ≤13.79% (12 cases), eight cases showed improved forward shoulder posture, while four cases showed no improvement.

      Interpretation

      Thoracic mobilization can be recommended in shoulder rehabilitation programs to improve forward shoulder posture to manage and prevent scapular malalignment in individuals with thoracic hyperkyphosis. We suggest that a high probability of improvement in forward shoulder posture can be expected when kyphosis is improved by >13.79%.

      Keywords

      1. Introduction

      Thoracic kyphosis, an anteroposterior curve of the thoracic spine in the sagittal plane, is defined using the Cobb angle (
      • Jung S.H.
      • Hwang U.J.
      • Kim J.H.
      • Ha S.M.
      • Kwon O.Y.
      Correlation among non-radiological measurements for thoracic kyphosis.
      ;
      • Neumann D.A.
      Kinesiology of the Musculoskeletal System-e-Book: Foundations for Rehabilitation.
      ). When the Cobb angle is >40°, it is defined as thoracic hyperkyphosis (
      • Fon G.T.
      • Pitt M.J.
      • Thies Jr., A.C.
      Thoracic kyphosis: range in normal subjects.
      ;
      • Katzman W.B.
      • Wanek L.
      • Shepherd J.A.
      • Sellmeyer D.E.
      Age-related hyperkyphosis: its causes, consequences, and management.
      ;
      • Vaughn D.W.
      • Brown E.W.
      The influence of an in-home based therapeutic exercise program on thoracic kyphosis angles.
      ). Thoracic hyperkyphosis is often accompanied by malalignment of the shoulder and muscle imbalance in the surrounding joints (
      • Lee J.H.
      • Cynn H.S.
      • Yi C.H.
      • Kwon O.Y.
      • Yoon T.L.
      Predictor variables for forward scapular posture including posterior shoulder tightness.
      ;
      • Page P.
      • Frank C.C.
      • Lardner R.
      Assessment and Treatment of Muscle Imbalance: The Janda Approach.
      ;
      • Sahrmann S.
      Movement System Impairment Syndromes of the Extremities, Cervical and Thoracic Spines.
      ). The muscle imbalance in thoracic hyperkyphosis is characterized by tightness of the upper trapezius and pectoralis muscles and weakness of the cervical flexors and lower trapezius (
      • Page P.
      • Frank C.C.
      • Lardner R.
      Assessment and Treatment of Muscle Imbalance: The Janda Approach.
      ) and can increase shoulder joint pain (
      • Grimsby O.
      • Gray J.
      Interrelation of the spine to the shoulder girdle.
      ;
      • Page P.
      • Frank C.C.
      • Lardner R.
      Assessment and Treatment of Muscle Imbalance: The Janda Approach.
      ;
      • Seidi F.
      • Bayattork M.
      • Minoonejad H.
      • Andersen L.L.
      • Page P.
      Comprehensive corrective exercise program improves alignment, muscle activation and movement pattern of men with upper crossed syndrome: randomized controlled trial.
      ).
      Thoracic hyperkyphosis structurally alters the position of the shoulder to protraction and anterior tilting (
      • Ayub E.
      Posture and the upper quadrant.
      ;
      • Finley M.A.
      • Lee R.Y.
      Effect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors.
      ;
      • Grimsby O.
      • Gray J.
      Interrelation of the spine to the shoulder girdle.
      ;
      • Ha S.M.
      • Kwon O.Y.
      • Cynn H.S.
      • Lee W.H.
      • Park K.N.
      • Kim S.H.
      • Jung D.Y.
      Comparison of electromyographic activity of the lower trapezius and serratus anterior muscle in different arm-lifting scapular posterior tilt exercises.
      ;
      • Kebaetse M.
      • McClure P.
      • Pratt N.A.
      Thoracic position effect on shoulder range of motion, strength, and three-dimensional scapular kinematics.
      ), which causes shoulder malalignment, such as forward shoulder posture (
      • Lee J.H.
      • Cynn H.S.
      • Yi C.H.
      • Kwon O.Y.
      • Yoon T.L.
      Predictor variables for forward scapular posture including posterior shoulder tightness.
      ;
      • Neumann D.A.
      Kinesiology of the Musculoskeletal System-e-Book: Foundations for Rehabilitation.
      ). Anterior tilting of the scapula due to a forward shoulder posture may cause shoulder impingement by narrowing the subacromial space (
      • Gumina S.
      • Di Giorgio G.
      • Postacchini F.
      • Postacchini R.
      Subacromial space in adult patients with thoracic hyperkyphosis and in healthy volunteers.
      ;
      • Lee J.H.
      • Cynn H.S.
      • Yi C.H.
      • Kwon O.Y.
      • Yoon T.L.
      Predictor variables for forward scapular posture including posterior shoulder tightness.
      ). In addition, the forward shoulder posture is accompanied by shoulder muscle imbalance, which causes thoracic outlet syndrome and shoulder joint dysfunction (
      • Fathollahnejad K.
      • Letafatkar A.
      • Hadadnezhad M.
      The effect of manual therapy and stabilizing exercises on forward head and rounded shoulder postures: a six-week intervention with a one-month follow-up study.
      ;
      • Singla D.
      • Veqar Z.
      Association between forward head, rounded shoulders, and increased thoracic kyphosis: a review of the literature.
      ).
      Thoracic mobilization improves thoracic hyperkyphosis (
      • Bautmans I.
      • Van Arken J.
      • Van Mackelenberg M.
      • Mets T.
      Rehabilitation using manual mobilization for thoracic kyphosis in elderly postmenopausal patients with osteoporosis.
      ;
      • Jung S.H.
      • Hwang U.J.
      • Ahn S.H.
      • Kim J.H.
      • Kwon O.Y.
      Effects of manual therapy and mechanical massage on spinal alignment, extension range of motion, back extensor electromyographic activity, and thoracic extension strength in individuals with thoracic hyperkyphosis: a randomized controlled trial.
      ;
      • Kamali F.
      • Shirazi S.A.
      • Ebrahimi S.
      • Mirshamsi M.
      • Ghanbari A.
      Comparison of manual therapy and exercise therapy for postural hyperkyphosis: a randomized clinical trial.
      ), and it is a technique that applies pressure to the thoracic spine in the posterior-anterior direction to improve thoracic kyphosis, extension angle, and thoracic strength (
      • Jung S.H.
      • Hwang U.J.
      • Ahn S.H.
      • Kim J.H.
      • Kwon O.Y.
      Effects of manual therapy and mechanical massage on spinal alignment, extension range of motion, back extensor electromyographic activity, and thoracic extension strength in individuals with thoracic hyperkyphosis: a randomized controlled trial.
      ;
      • Kamali F.
      • Shirazi S.A.
      • Ebrahimi S.
      • Mirshamsi M.
      • Ghanbari A.
      Comparison of manual therapy and exercise therapy for postural hyperkyphosis: a randomized clinical trial.
      ). Previous studies have also investigated the effect of thoracic mobilization on shoulder dysfunction by assessing the articulation of the thoracic spine with the shoulder joint (
      • Cho J.
      • Lee E.
      • Lee S.
      Upper thoracic spine mobilization and mobility exercise versus upper cervical spine mobilization and stabilization exercise in individuals with forward head posture: a randomized clinical trial.
      ;
      • Lenker C.
      • Larocca N.
      • Lee J.
      • Tucker P.
      The use of thoracic mobilization with movement to treat shoulder impingement in older adults: a case study.
      ;
      • Otoshi K.
      • Takegami M.
      • Sekiguchi M.
      • Onishi Y.
      • Yamazaki S.
      • Otani K.
      • Shishido H.
      • Kikuchi S.
      • Konno S.
      Association between kyphosis and subacromial impingement syndrome: LOHAS study.
      ;
      • Park S.J.
      • Kim S.H.
      • Kim S.H.
      Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
      ).
      • Park S.J.
      • Kim S.H.
      • Kim S.H.
      Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
      reported that thoracic mobilization improved the range of motion of the shoulder joint and upper trapezius muscle tone, as well as thoracic kyphosis (
      • Park S.J.
      • Kim S.H.
      • Kim S.H.
      Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
      ). Additionally, thoracic mobilization decreased shoulder pain and disability index (
      • Lee S.B.
      The effect of scapular stabilization exercise and thoracic joint mobilization on the scapular function in adults with scapular dysfunction.
      ;
      • Park S.J.
      • Kim S.H.
      • Kim S.H.
      Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
      ), and increased the strength of the scapular muscles (
      • Liebler E.J.
      • Tufano-Coors L.
      • Douris P.
      • Makofsky H.W.
      • McKenna R.
      • Michels C.
      • Rattray S.
      The effect of thoracic spine mobilization on lower trapezius strength testing.
      ).
      While many studies have assessed thoracic kyphosis and the shoulder joint (
      • Barrett E.
      • O’Keeffe M.
      • O’Sullivan K.
      • Lewis J.
      • McCreesh K.
      Is thoracic spine posture associated with shoulder pain, range of motion and function? A systematic review.
      ;
      • Cho J.
      • Lee E.
      • Lee S.
      Upper thoracic spine mobilization and mobility exercise versus upper cervical spine mobilization and stabilization exercise in individuals with forward head posture: a randomized clinical trial.
      ;
      • Park S.J.
      • Kim S.H.
      • Kim S.H.
      Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
      ), the effect of thoracic mobilization on shoulder alignment when thoracic hyperkyphosis is improved is unclear. Assessment of thoracic mobilization of the shoulder in individuals with thoracic hyperkyphosis may allow clarification of the effect of improvement in thoracic hyperkyphosis on shoulder alignment. Therefore, this study evaluated the effect of eight weeks of thoracic mobilization for thoracic hyperkyphosis on forward shoulder posture and determined a cutoff change ratio in kyphosis to improve forward shoulder posture based on the decision tree method.

      2. Material and methods

      2.1 Participants

      Participants were recruited through internet advertising from July 2018 to August 2019. The following inclusion criteria determined study participation: age 18–50 years, asymptomatic (no pain symptoms in the spine), and thoracic kyphosis angle >40° measured using a Spinal Mouse for screening hyperkyphosis (Idiag AG, Fehraltorf, Switzerland). The exclusion criteria were presence of scoliosis or a history of spinal column fracture, spinal tumors and related malignancies, congenital spinal anomalies, cancer, or rheumatoid arthritis (
      • Kamali F.
      • Shirazi S.A.
      • Ebrahimi S.
      • Mirshamsi M.
      • Ghanbari A.
      Comparison of manual therapy and exercise therapy for postural hyperkyphosis: a randomized clinical trial.
      ). Twenty participants were eligible for the study, and one participant discontinued the study for personal reasons. The ethics committee of Yonsei University approved the study, and all participants provided written informed consent before inclusion. The study was approved by the institutional review board of Yonsei University (1041849-201901-BM-019-01). Based on a pilot study, the required sample size was calculated by a priori power analysis using G*Power 3.1 (G*Power Software Inc., Kiel, Germany). The α level was set at 0.05 using the effect size calculation for thoracic kyphosis. The results of a pilot study with three participants showed that a minimum sample size of 16 was required for a power of 0.95.

      2.2 Research procedures

      Among the volunteers for this study, participants with a thoracic kyphosis of 40° or higher, as measured using a device called Spinal Mouse, were recruited. After recruitment was complete, the participants were initially assessed for thoracic kyphosis using radiography and forward shoulder posture was measured using length measurement. The participants were initially assessed for thoracic kyphosis and forward shoulder posture (before mobilization). They were also instructed regarding the use of mechanical devices to provide mobilization. The participants self-applied the intervention at home for a total of 24 mobilizations over eight weeks. Within one week after the last session, the participants equally measured thoracic kyphosis and forward shoulder posture (after mobilization).

      2.2.1 Thoracic kyphosis

      Digital lateral thoracic spine radiographs were obtained using a collimator and an MC-D computed radiographic system (Medien International, Co., Ltd., Gyeonggi-do, South Korea) to measure thoracic kyphosis. Each participant stood at a distance of 100 cm so that the left side of the body faced the X-ray beam and the beam was centered at T7 of the thoracic spine (
      • Edmondston S.J.
      • Christensen M.M.
      • Keller S.
      • Steigen L.B.
      • Barclay L.
      Functional radiographic analysis of thoracic spine extension motion in asymptomatic men.
      ;
      • Gallagher K.M.
      • Sehl M.
      • Callaghan J.P.
      A radiographic assessment of lumbar spine posture in four different upright standing positions.
      ). All image analyses were performed by one radiology technologist with >5 years of experience. The radiographic images were analyzed on a personal computer using ImageJ (National Institutes of Health, Bethesda, MD, USA). Thoracic kyphosis was analyzed using the Cobb angle of the sagittal plane. The Cobb angle of the sagittal plane is the angle between the superior end plate of the 4th thoracic vertebra body and the inferior end plate of the 12th thoracic vertebra body (
      • Katzman W.B.
      • Parimi N.
      • Gladin A.
      • Poltavskiy E.A.
      • Schafer A.L.
      • Long R.K.
      • Fan B.
      • Wong S.S.
      • Lane N.E.
      Sex differences in response to targeted kyphosis specific exercise and posture training in community-dwelling older adults: a randomized controlled trial.
      ). If the superior end plate of the 4th thoracic vertebra body was not identified, the inferior end plate of the 4th thoracic vertebra body was analyzed. To investigate the rate of change in thoracic kyphosis before and after mobilization intervention, the change ratio in kyphosis was calculated as follows:
      Change ratio in kyphosis=Thoracic kyphosis before mobilizationThoracic kyphosis after mobilizationThoracic kyphosis before mobilization×100


      2.2.2 Forward shoulder posture

      Forward shoulder posture was defined based on the acromion-to-the-wall index, which was defined as the alignment of the shoulder relative to the frontal plane (
      • Carvalho L.A.
      • Aquino C.F.
      • Souza T.R.
      • Anjos M.T.S.
      • Lima D.B.
      • Fonseca S.T.
      Clinical measures related to forward shoulder posture: a reliability and correlational study.
      ;
      • Laudner K.G.
      • Moline M.T.
      • Meister K.
      The relationship between forward scapular posture and posterior shoulder tightness among baseball players.
      ). The participants stood against a wall with the hip and knees slightly flexed. The end of the ruler was fixed to the wall, while the square of the ruler was placed at the tip of the anterior portion of the acromion process of the measured shoulder (Fig. 1). The distance between the wall and acromion was defined as the length of the acromion-to-the-wall index. The acromion-to-the-wall index was measured twice for the right and left sides and then averaged. The intra-rater reliability (ICC) was good to excellent (ICC = 0.84–0.92) (
      • Carvalho L.A.
      • Aquino C.F.
      • Souza T.R.
      • Anjos M.T.S.
      • Lima D.B.
      • Fonseca S.T.
      Clinical measures related to forward shoulder posture: a reliability and correlational study.
      ;
      • Laudner K.G.
      • Moline M.T.
      • Meister K.
      The relationship between forward scapular posture and posterior shoulder tightness among baseball players.
      ;
      • Lee J.H.
      • Cynn H.S.
      • Yi C.H.
      • Kwon O.Y.
      • Yoon T.L.
      Predictor variables for forward scapular posture including posterior shoulder tightness.
      ). Improved forward shoulder posture was defined as the odds of the acromion-to-the-wall index after mobilization/acromion-to-the-wall index before mobilization of 100% or more; in contrast, a not-improved posture was defined as a value <100%.
      Fig. 1
      Fig. 1Measurement of forward shoulder posture (acromion to the wall index).

      2.2.3 Thoracic mobilization

      Equal mobilization was applied to all participants using a mechanical device (Pookjam Factorial Inc., Seoul, South Korea) validated in previous studies (
      • Jung S.H.
      • Hwang U.J.
      • Ahn S.H.
      • Kim J.H.
      • Kwon O.Y.
      Effects of manual therapy and mechanical massage on spinal alignment, extension range of motion, back extensor electromyographic activity, and thoracic extension strength in individuals with thoracic hyperkyphosis: a randomized controlled trial.
      ). The bed-type mechanical device had two circular rollers with a diameter of 5 cm each, which massaged the erector spinae muscles while simultaneously mobilizing the spine in the direction of extension (Fig. 2). This study used the thoracic mode of the device to improve thoracic hyperkyphosis. In this mode, the roller moved from the head to the thoracic spine at 0.4 cm/s, moving up and down three times in 25 min. The participants applied thoracic mobilization in the home three times weekly for eight weeks. Cell phone messages were used to check whether the participants had performed thoracic mobilization.
      Fig. 2
      Fig. 2Mobilization procedure using mechanical device.

      2.3 Statistical analysis

      Kolmogorov–Smirnov tests were used to assess the homogeneity of all variances (p > 0.05). To compare the effects before and after thoracic mobilization, paired t-tests were used. All statistical analyses were performed using IBM SPSS Statistics for Windows, version 20.0 (IBM Corp., Armonk, NY), with the level of statistical significance set to p < 0.05. A decision tree was used to determine the cutoff value of the change ratio in kyphosis to predict the improvement in forward shoulder posture. The predictive decision tree in SPSS based on the criteria in Table 1 used the classification and regression tree approach. The dependent variable was the probability of the acromion-to-the-wall index. The factors that affected the scores are listed under the independent variable as the change ratio in kyphosis.
      Table 1Model summary.
      SpecificationsGrowing methodClassification and regression tree Odds of the acromion to the wall
      Dependent variableChange ratio in kyphosis
      Independent variableNone
      Validation5
      Maximum tree depth15
      Minimum cases in the parent node5
      Minimum cases in the child node
      ResultsIndependent variables includedChange ratio in kyphosis
      Number of nodes3
      Number of terminal nodes2
      Depth1

      3. Results

      This study included 19 participants (age: 33.37 ± 6.56 years; height: 170.32 ± 7.92 cm; weight: 69.77 ± 14.70 kg; body mass index: 23.83 ± 3.66 kg/m2). The thoracic kyphosis angle improved significantly after thoracic mobilization (before = 43.43 ± 6.76; after = 39.11 ± 6.74; t = 3.416, p < 0.01). Significant differences in acromion-to-the-wall index were also observed (before = 14.57 ± 1.84; after = 14.09 ± 1.90; t = 2.275, p = 0.035, Fig. 3).
      Fig. 3
      Fig. 3Acromion to the wall index values before and after thoracic mobilization.
      Fig. 4 shows the classification tree for improving the forward shoulder posture, which has two terminal nodes. The classification tree for improving forward shoulder posture showed a change ratio in kyphosis. Each node label showed a subgroup (improved forward shoulder posture or no improvement). Below each node label was a number showing how many subgroups were observed in the node. Within the overall study population (19 cases), 15 cases showed improved forward shoulder posture, while four cases showed no improvement. The cutoff value of the change ratio in kyphosis for improving forward shoulder posture was >13.79%. In the subgroup with a change ratio of kyphosis >13.79% (seven cases), all patients showed improved forward shoulder posture. In contrast, in the subgroup with a change ratio of kyphosis ≤13.79% (12 cases), eight cases showed improved forward shoulder posture, while four cases did not.
      Fig. 4
      Fig. 4Classification tree for improving forward shoulder posture. Values are presented as number/total number.
      AWI: acromion to the wall index.

      4. Discussion

      Thoracic mobilization reduces shoulder dysfunction in individuals with shoulder malalignment (
      • Park S.J.
      • Kim S.H.
      • Kim S.H.
      Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
      ). The thoracic mobilization applied in this study provides posteroanterior pressure force to facilitate extension at the thoracic segment (
      • Jung S.H.
      • Hwang U.J.
      • Ahn S.H.
      • Kim J.H.
      • Kwon O.Y.
      Effects of manual therapy and mechanical massage on spinal alignment, extension range of motion, back extensor electromyographic activity, and thoracic extension strength in individuals with thoracic hyperkyphosis: a randomized controlled trial.
      ). The results of this study confirmed that eight weeks of thoracic mobilization improved not only thoracic kyphosis, but also forward shoulder posture. Forward shoulder posture causes shoulder muscle imbalance and is a risk factor for shoulder dysfunction (
      • Yoo W.G.
      Comparison of shoulder muscles activation for shoulder abduction between forward shoulder posture and asymptomatic persons.
      ). Thus, thoracic mobilization can change shoulder alignment, which may affect shoulder dysfunction (
      • Cho J.
      • Lee E.
      • Lee S.
      Upper thoracic spine mobilization and mobility exercise versus upper cervical spine mobilization and stabilization exercise in individuals with forward head posture: a randomized clinical trial.
      ;
      • Land H.
      • Gordon S.
      • Watt K.
      Effect of manual physiotherapy in homogeneous individuals with subacromial shoulder impingement: a randomized controlled trial.
      ;
      • Park S.J.
      • Kim S.H.
      • Kim S.H.
      Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
      ).
      The decrease in the index of the acromion to the wall indicated improved shoulder alignment (
      • Borstad J.D.
      Resting position variables at the shoulder: evidence to support a posture-impairment association.
      ;
      • Do Y.L.
      • Nam C.W.
      • Sung Y.B.
      • Kim K.
      • Lee H.Y.
      Changes in rounded shoulder posture and forward head posture according to exercise methods.
      ;
      • Laudner K.G.
      • Moline M.T.
      • Meister K.
      The relationship between forward scapular posture and posterior shoulder tightness among baseball players.
      ;
      • Lee J.H.
      • Cynn H.S.
      • Yi C.H.
      • Kwon O.Y.
      • Yoon T.L.
      Predictor variables for forward scapular posture including posterior shoulder tightness.
      ). Thoracic hyperkyphosis causes overactivation of the pectoralis and weakening of the lower trapezius, which affects humerus and scapula alignment, consequently increasing the forward shoulder posture (
      • Lee J.H.
      • Cynn H.S.
      • Yi C.H.
      • Kwon O.Y.
      • Yoon T.L.
      Predictor variables for forward scapular posture including posterior shoulder tightness.
      ;
      • Page P.
      • Frank C.C.
      • Lardner R.
      Assessment and Treatment of Muscle Imbalance: The Janda Approach.
      ). Thoracic mobilization improved thoracic hyperkyphosis (
      • Jung S.H.
      • Hwang U.J.
      • Ahn S.H.
      • Kim J.H.
      • Kwon O.Y.
      Effects of manual therapy and mechanical massage on spinal alignment, extension range of motion, back extensor electromyographic activity, and thoracic extension strength in individuals with thoracic hyperkyphosis: a randomized controlled trial.
      ;
      • Kamali F.
      • Shirazi S.A.
      • Ebrahimi S.
      • Mirshamsi M.
      • Ghanbari A.
      Comparison of manual therapy and exercise therapy for postural hyperkyphosis: a randomized clinical trial.
      ) and increased middle trapezius activation and lower trapezius strength (
      • Liebler E.J.
      • Tufano-Coors L.
      • Douris P.
      • Makofsky H.W.
      • McKenna R.
      • Michels C.
      • Rattray S.
      The effect of thoracic spine mobilization on lower trapezius strength testing.
      ;
      • Muth S.
      • Barbe M.F.
      • Lauer R.
      • McClure P.
      The effects of thoracic spine manipulation in subjects with signs of rotator cuff tendinopathy.
      ). Improvements in the middle and lower trapezius prevent excessive scapular protraction (
      • Muscolino J.E.
      The Muscular System Manual-E-Book: The Skeletal Muscles of the Human Body.
      ) to improve forward shoulder posture, as observed in the present study.
      Previous studies on the improvement of thoracic kyphosis after mobilization reported kyphosis change ratios of 7% (45.7 → 40.6) (
      • Kamali F.
      • Shirazi S.A.
      • Ebrahimi S.
      • Mirshamsi M.
      • Ghanbari A.
      Comparison of manual therapy and exercise therapy for postural hyperkyphosis: a randomized clinical trial.
      ), 7.87% (44.5 → 41.0) (
      • Park S.J.
      • Kim S.H.
      • Kim S.H.
      Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
      ), and 5% (52.5 → 49.1) (
      • Bautmans I.
      • Van Arken J.
      • Van Mackelenberg M.
      • Mets T.
      Rehabilitation using manual mobilization for thoracic kyphosis in elderly postmenopausal patients with osteoporosis.
      ). Although thoracic kyphosis is positively correlated with forward shoulder posture (
      • Lee J.H.
      • Cynn H.S.
      • Yi C.H.
      • Kwon O.Y.
      • Yoon T.L.
      Predictor variables for forward scapular posture including posterior shoulder tightness.
      ), the relationship between the change ratio in kyphosis and improvement in forward shoulder posture is unclear (
      • Barrett E.
      • O’Keeffe M.
      • O’Sullivan K.
      • Lewis J.
      • McCreesh K.
      Is thoracic spine posture associated with shoulder pain, range of motion and function? A systematic review.
      ). Therefore, this study used a decision tree to analyze the change ratio in kyphosis and also the cutoff values for the odds of the acromion-to-the-wall index. The cutoff change ratio in kyphosis for the odds of the acromion to the wall index was 13.8%. The results of this study suggested an increased probability of the forward shoulder posture for kyphosis improvements in individuals with hyperkyphosis of 13.8% or more.
      This study had several limitations. First, no control group was included. In future studies, a control group is needed to investigate the causes of improved shoulder alignment after thoracic mobilization. Second, in this study, forward shoulder posture was measured, however, shoulder dysfunction was not measured. In subsequent studies, it will be necessary to measure shoulder dysfunction in order to confirm the effect of mobilization on shoulder dysfunction. Third, our study included subjects aged 20–50 years, with a mean age of the final participants of 33.37 ± 6.56 years. Since we did not include patients aged >50 years, our findings cannot be generalized to the elderly population. Additionally, though cell phone messages were used to ensure compliance to the three-time weekly application of self-thoracic mobilization, no provision was made to prevent over-treatment. Lastly, the angle of thoracic kyphosis in the study participants was 43.43° ± 6.76°. Because we did not include participants with severe hyperkyphosis, our findings cannot be generalized to more severe types of thoracic hyperkyphosis.

      5. Conclusions

      We observed an improved acromion-to-the-wall index following eight weeks of thoracic mobilization. Thus, thoracic mobilization can be recommended in shoulder rehabilitation programs to improve forward shoulder posture for the management and prevention of shoulder malalignment in individuals with thoracic hyperkyphosis. The cutoff change ratio in kyphosis for improving forward shoulder posture was >13.8%. Therefore, we suggest that a high probability of improvement in forward shoulder posture can be expected when kyphosis is improved by >13.8%.

      IRB approval

      This study was approved by the Yonsei University Wonju Institutional Review Board (1041849-201901-BM-019-01).

      Clinical trial registration number

      This study was registered by the Korea Clinical Research Information Service (KCT0004527; Registered 07 December 2019, https://cris.nih.go.kr/cris/en/search/search_result_st01.jsp?seq=15268).

      Funding

      This research was funded by the Yonsei University Research Fund ( 2021–51-0093 and 2021–52-0091 ) and the “Brain Korea 21 FOUR Project”, the Korean Research Foundation for Department of Physical Therapy in the Graduate School of Yonsei University.

      Declaration of Competing Interest

      The authors declare that they have no potential conflicts of interest with respect to the research, authorship, and publication of this article. The results are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation.

      Acknowledgements

      This study was supported by the “Brain Korea 21 FOUR Project”, the Korean Research Foundation for Department of Physical Therapy in the Graduate School of Yonsei University.

      References

        • Ayub E.
        Posture and the upper quadrant.
        in: Donatelli R.A. Physical Therapy of the Shoulder. 2nd ed. Churchill Livingston, New York1997: 81 (Chapter 4)
        • Barrett E.
        • O’Keeffe M.
        • O’Sullivan K.
        • Lewis J.
        • McCreesh K.
        Is thoracic spine posture associated with shoulder pain, range of motion and function? A systematic review.
        Man. Ther. 2016; 26: 38-46
        • Bautmans I.
        • Van Arken J.
        • Van Mackelenberg M.
        • Mets T.
        Rehabilitation using manual mobilization for thoracic kyphosis in elderly postmenopausal patients with osteoporosis.
        J. Rehabil. Med. 2010; 42: 129-135
        • Borstad J.D.
        Resting position variables at the shoulder: evidence to support a posture-impairment association.
        Phys. Ther. 2006; 86: 549-557
        • Carvalho L.A.
        • Aquino C.F.
        • Souza T.R.
        • Anjos M.T.S.
        • Lima D.B.
        • Fonseca S.T.
        Clinical measures related to forward shoulder posture: a reliability and correlational study.
        J. Manipulative Physiol. Ther. 2019; 42: 141-147
        • Cho J.
        • Lee E.
        • Lee S.
        Upper thoracic spine mobilization and mobility exercise versus upper cervical spine mobilization and stabilization exercise in individuals with forward head posture: a randomized clinical trial.
        BMC Musculoskelet. Disord. 2017; 18: 1-10
        • Do Y.L.
        • Nam C.W.
        • Sung Y.B.
        • Kim K.
        • Lee H.Y.
        Changes in rounded shoulder posture and forward head posture according to exercise methods.
        J. Phys. Ther. Sci. 2017; 29: 1824-1827
        • Edmondston S.J.
        • Christensen M.M.
        • Keller S.
        • Steigen L.B.
        • Barclay L.
        Functional radiographic analysis of thoracic spine extension motion in asymptomatic men.
        J. Manipulative Physiol. Ther. 2012; 35: 203-208
        • Fathollahnejad K.
        • Letafatkar A.
        • Hadadnezhad M.
        The effect of manual therapy and stabilizing exercises on forward head and rounded shoulder postures: a six-week intervention with a one-month follow-up study.
        BMC Musculoskelet. Disord. 2019; 20: 1-8
        • Finley M.A.
        • Lee R.Y.
        Effect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors.
        Arch. Phys. Med. Rehabil. 2003; 84: 563-568
        • Fon G.T.
        • Pitt M.J.
        • Thies Jr., A.C.
        Thoracic kyphosis: range in normal subjects.
        Am. J. Roentgenol. 1980; 134: 979-983
        • Gallagher K.M.
        • Sehl M.
        • Callaghan J.P.
        A radiographic assessment of lumbar spine posture in four different upright standing positions.
        Clin. Biomech. 2016; 37: 131-136
        • Grimsby O.
        • Gray J.
        Interrelation of the spine to the shoulder girdle.
        Phys. Therapy Should. 1997; 3: 95-129
        • Gumina S.
        • Di Giorgio G.
        • Postacchini F.
        • Postacchini R.
        Subacromial space in adult patients with thoracic hyperkyphosis and in healthy volunteers.
        La Chirurgia Degli Org. Movimento. 2008; 91: 93-96
        • Ha S.M.
        • Kwon O.Y.
        • Cynn H.S.
        • Lee W.H.
        • Park K.N.
        • Kim S.H.
        • Jung D.Y.
        Comparison of electromyographic activity of the lower trapezius and serratus anterior muscle in different arm-lifting scapular posterior tilt exercises.
        Phys. Therapy Sport. 2012; 13: 227-232
        • Jung S.H.
        • Hwang U.J.
        • Ahn S.H.
        • Kim J.H.
        • Kwon O.Y.
        Effects of manual therapy and mechanical massage on spinal alignment, extension range of motion, back extensor electromyographic activity, and thoracic extension strength in individuals with thoracic hyperkyphosis: a randomized controlled trial.
        Evid. Based Complement. Alternat. Med. 2020; 23: 6526935
        • Jung S.H.
        • Hwang U.J.
        • Kim J.H.
        • Ha S.M.
        • Kwon O.Y.
        Correlation among non-radiological measurements for thoracic kyphosis.
        J. Musculoskel. Sci. Technol. 2020; 4: 1-5
        • Kamali F.
        • Shirazi S.A.
        • Ebrahimi S.
        • Mirshamsi M.
        • Ghanbari A.
        Comparison of manual therapy and exercise therapy for postural hyperkyphosis: a randomized clinical trial.
        Physiother. Theory Pract. 2016; 32: 92-97
        • Katzman W.B.
        • Wanek L.
        • Shepherd J.A.
        • Sellmeyer D.E.
        Age-related hyperkyphosis: its causes, consequences, and management.
        J. Orthop. Sports Phys. Ther. 2010; 40: 352-360
        • Katzman W.B.
        • Parimi N.
        • Gladin A.
        • Poltavskiy E.A.
        • Schafer A.L.
        • Long R.K.
        • Fan B.
        • Wong S.S.
        • Lane N.E.
        Sex differences in response to targeted kyphosis specific exercise and posture training in community-dwelling older adults: a randomized controlled trial.
        BMC Musculoskelet. Disord. 2017; 18: 1-11
        • Kebaetse M.
        • McClure P.
        • Pratt N.A.
        Thoracic position effect on shoulder range of motion, strength, and three-dimensional scapular kinematics.
        Arch. Phys. Med. Rehabil. 1999; 80: 945-950
        • Land H.
        • Gordon S.
        • Watt K.
        Effect of manual physiotherapy in homogeneous individuals with subacromial shoulder impingement: a randomized controlled trial.
        Physiother. Res. Int. 2019; 24e1768
        • Laudner K.G.
        • Moline M.T.
        • Meister K.
        The relationship between forward scapular posture and posterior shoulder tightness among baseball players.
        Am. J. Sports Med. 2010; 38: 2106-2112
        • Lee J.H.
        • Cynn H.S.
        • Yi C.H.
        • Kwon O.Y.
        • Yoon T.L.
        Predictor variables for forward scapular posture including posterior shoulder tightness.
        J. Bodyw. Mov. Ther. 2015; 19: 253-260
        • Lee S.B.
        The effect of scapular stabilization exercise and thoracic joint mobilization on the scapular function in adults with scapular dysfunction.
        J. Indus. Converg. 2021; 19: 83-90
        • Lenker C.
        • Larocca N.
        • Lee J.
        • Tucker P.
        The use of thoracic mobilization with movement to treat shoulder impingement in older adults: a case study.
        Topics Geriat. Rehabil. 2012; 28: 195-200
        • Liebler E.J.
        • Tufano-Coors L.
        • Douris P.
        • Makofsky H.W.
        • McKenna R.
        • Michels C.
        • Rattray S.
        The effect of thoracic spine mobilization on lower trapezius strength testing.
        J. Manual Manipul. Therapy. 2001; 9: 207-212
        • Muscolino J.E.
        The Muscular System Manual-E-Book: The Skeletal Muscles of the Human Body.
        Elsevier Health Sciences., 2016
        • Muth S.
        • Barbe M.F.
        • Lauer R.
        • McClure P.
        The effects of thoracic spine manipulation in subjects with signs of rotator cuff tendinopathy.
        J. Orthop. Sports Phys. Ther. 2012; 42: 1005-1016
        • Neumann D.A.
        Kinesiology of the Musculoskeletal System-e-Book: Foundations for Rehabilitation.
        Elsevier Health Sciences, 2016
        • Otoshi K.
        • Takegami M.
        • Sekiguchi M.
        • Onishi Y.
        • Yamazaki S.
        • Otani K.
        • Shishido H.
        • Kikuchi S.
        • Konno S.
        Association between kyphosis and subacromial impingement syndrome: LOHAS study.
        J. Shoulder Elb. Surg. 2014; 23: e300-e307
        • Page P.
        • Frank C.C.
        • Lardner R.
        Assessment and Treatment of Muscle Imbalance: The Janda Approach.
        Human Kinetics, 2010
        • Park S.J.
        • Kim S.H.
        • Kim S.H.
        Effects of thoracic mobilization and extension exercise on thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.
        Healthcare. 2020; 8: 316
        • Sahrmann S.
        Movement System Impairment Syndromes of the Extremities, Cervical and Thoracic Spines.
        Mosby, 2011
        • Seidi F.
        • Bayattork M.
        • Minoonejad H.
        • Andersen L.L.
        • Page P.
        Comprehensive corrective exercise program improves alignment, muscle activation and movement pattern of men with upper crossed syndrome: randomized controlled trial.
        Sci. Rep. 2020; 10: 1-11
        • Singla D.
        • Veqar Z.
        Association between forward head, rounded shoulders, and increased thoracic kyphosis: a review of the literature.
        J. Chiropract. Med. 2017; 16: 220-229
        • Vaughn D.W.
        • Brown E.W.
        The influence of an in-home based therapeutic exercise program on thoracic kyphosis angles.
        J. Back Musculoskel. Rehabil. 2007; 20: 155-165
        • Yoo W.G.
        Comparison of shoulder muscles activation for shoulder abduction between forward shoulder posture and asymptomatic persons.
        J. Phys. Ther. Sci. 2013; 25: 815-816