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PHYS THER
Vol. 86, No. 4, April 2006, pp. 549-557
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Research Reports

Resting Position Variables at the Shoulder: Evidence to Support a Posture-Impairment Association

John D Borstad

JD Borstad, PT, PhD, is Assistant Professor, Physical Therapy Division, Ohio State University, 516 Atwell Hall, 453 W Tenth Ave, Columbus, OH 43210 (USA)

(borstad.1{at}osu.edu)


Submitted August 15, 2005; Accepted November 23, 2005


   Abstract
 
Background and Purpose.A relationship between posture and impairment at the shoulder is theorized, but not supported by evidence. It is proposed that posture and impairment are not directly related, but linked by movement dysfunction. The purpose of this analysis was to explore the relationships among posture, pectoralis minor muscle length, and movement alterations at the shoulder. Subjects. Subjects who were asymptomatic for shoulder pathology were divided into 2 groups of 25 subjects each based on normalized pectoralis minor muscle resting length. Methods. Scapula orientation, thoracic kyphosis, and pectoralis minor muscle lengths were measured, and ratios and indexes of postural variables were calculated. All variables were analyzed for correlations and group differences. Results. Significant group differences were demonstrated for several posture variables, including thoracic spine kyphosis and scapular internal rotation. The distance from the sternal notch to the coracoid process demonstrated the highest correlation with pectoralis minor muscle length. Discussion and Conclusion. The findings indicate a relationship between posture and pectoralis minor muscle length and support a proposed model linking posture, an anatomical variable, movement dysfunction, and impairment. [Borstad JD. Resting position variables at the shoulder: evidence to support a posture-impairment association. Phys Ther. 2006;86:549–557.]

Key Words: Biomechanics • Posture • Scapula • Shoulder


   Introduction
Top
 Abstract
 Introduction
Method
 Results
 Discussion and Conclusions
 References
 
Postural deviations, including forward head, forward shoulders (scapular protraction), humeral internal rotation, and increased thoracic kyphosis, have been implicated in the development of shoulder pain.1–4 The relationship between postural deviations and shoulder pain syndromes is based on the theory that with prolonged positional changes, soft tissues on one side of the joint will adaptively lengthen, while soft tissues on the opposite side of the joint will adaptively shorten.5,6 These soft tissue adaptations are presumed to alter active and passive forces acting at the shoulder joint during movement, in turn leading to biomechanical alterations and pain.7 As yet, however, a direct relationship between postural deviations and shoulder pain has not been demonstrated in controlled studies.2,3,8

One explanation for failing to find a relationship between postural deviations and shoulder pain is that these 2 entities are at the beginning and end, respectively, of a continuum, with movement alterations occurring between them. Sahrmann9 stated that biomechanical systems are similar to mechanical systems, making optimal alignment necessary for optimal movement. Postural deviations, therefore, may change the biomechanical system’s ability to produce precise movement, and, over time or with exposure to repetitive tasks, pain begins as a response to these imprecise movements.9 Based on this explanation, if a link between postural deviations and pain exists, it is unlikely to be determined without also examining the relationships between posture and movement and between movement and pain.

Several studies support a relationship between movement and pain because scapular kinematic alterations have been demonstrated in subjects with subacromial impingement syndrome.10–12 Increased scapular internal rotation,11 decreased scapular posterior tilting,10–12 and decreased scapular upward rotation11 have all been discovered in subjects with impingement compared with control subjects who were asymptomatic for shoulder pathology. These scapular motion alterations are believed to decrease the subacromial space by failing to move the acromion away from the humeral head during arm elevation,11,13–16 resulting in increased compressive loads on the tendons of the rotator cuff or long head of the biceps muscle. Figure 1 defines these 3-dimensional scapular rotations.


Figure 1
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  		Figure 1. Scapula axes (X, Y, Z) and 3-dimensional rotations. Upward and downward rotation occur around Y, internal and external rotation occur around Z, and anterior and posterior tilting occur around X.

 
The mechanisms responsible for the scapular alterations demonstrated in subjects with impingement have not been clearly defined, but one potential mechanism is an adaptively short pectoralis minor muscle.5,7,10–12 Forward shoulder posture, defined as a sagittal-plane or transverse-plane scapular resting position change, is theorized to result in adaptive shortening of the pectoralis minor muscle by approximating the muscles’ insertion sites on the coracoid process and ribs 3, 4, and 5.5,7 Decreased pectoralis minor muscle resting length would result in an increase in the muscles’ passive tension during arm elevation, restricting normal scapular upward rotation, posterior tipping, and external rotation. This potential effect of pectoralis minor muscle resting length on scapular kinematics has been examined between groups of subjects who were asymptomatic for shoulder pathology.17 A group of subjects with a relatively shorter pectoralis minor muscle resting length demonstrated increased scapular internal rotation during arm elevation and decreased scapular posterior tilting at higher arm elevation angles (90° and 120°) when compared with a group of subjects with a relatively longer pectoralis minor muscle resting length.17 These scapular motion alterations are consistent with those previously demonstrated by subjects with impingement.10–12

The kinematic study17 described above provides evidence for a relationship between pectoralis minor muscle length variability and altered scapular movement. Demonstrating a relationship between postural alignment and pectoralis minor muscle length would provide another connection in a proposed posture-impairment chain (Fig. 2), based on Sahrmann’s9 suggestion of how these variables are linked. Motivated by this potential connection, postural variables were measured in addition to the pectoralis minor muscle resting length prior to the kinematic study.17 The purposes of this article are to report the results of the postural measurements as they relate to pectoralis minor muscle resting length and scapular biomechanics and to discuss the relevance of the findings to the posture-impairment relationship.


Figure 2
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  		Figure 2. A proposed model linking alignment deviations and impairment.

 

   Method
Top
 Abstract
 Introduction
 Method
Results
 Discussion and Conclusions
 References
 
Subjects

This study formed part of a comprehensive cross-sectional study examining the effect of pectoralis minor muscle resting length on scapular kinematics. To find resting angular differences of 5 degrees between groups, a sample size estimate with a significance level of .05 and a power of 0.8 was calculated to be 25 subjects per group. A sample size estimate for the correlation analysis planned in this component of the study determined that 18 subjects were needed. Therefore, the larger number of subjects was targeted, resulting in a total of 50 subjects for the analysis.

Subjects were required to be asymptomatic for shoulder pathology and between 18 and 40 years of age to ensure full musculoskeletal development while avoiding joint degenerative changes associated with aging, both of which may affect normal biomechanics. A clinical screening examination ruled out impingement, instability, or laxity and ensured normal arm elevation range of motion. Because current pain, impingement, or instability could alter movement, subjects were excluded if they had a positive impingement test (Neer, Hawkins-Kennedy, Jobe, or Yocum), apprehension test, or sulcus sign.18 Volunteers were recruited by personal contact and advertising on campus. All subjects voluntarily signed both an institutionally approved informed consent form and a Health Insurance Portability and Accountability Act (HIPAA) form before entering the study.

Procedure

Several variables were measured using a Flock of Birds* electromagnetic motion capture system consisting of a high-frequency electromagnetic transmitter and 4 receivers. The receivers are placed on the subjects’ skin over the segments to be analyzed, and data indicating their orientation and position relative to the transmitter are conveyed back to a personal computer with MotionMonitor* software. The software converts the orientation and position from the transmitter reference system to a local reference system. The stated accuracy for this system is 0.5 degree root-mean-square for segment orientation and 1.8 mm root-mean-square for position. Reliability and validity of measurements of shoulder kinematic variables obtained using electromagnetic systems have been demonstrated in previous studies.11,19,20

For the pectoralis minor muscle measurement, receivers were taped to the skin over the sternum and acromion and secured to a thermoplastic cuff strapped to the humerus. The fourth receiver was secured to a stylus for digitizing palpable landmarks on the thorax, scapula, and humerus. Digitizing creates local orthogonal axis systems on each segment, which are subsequently used to describe the position of one segment relative to an adjacent segment. The inferomedial aspect of the coracoid process and the caudal edge of the fourth rib adjacent to the sternum also were digitized to represent the origin and insertion of the pectoralis minor muscle. The software then calculates the position of each landmark relative to its local sensor and determines the vector distance between the landmarks. The use of this method was validated by stabilizing 11 fresh cadavers in an upright sitting position, performing the measurement using palpation of landmarks as described above, and then dissecting through the skin to repeat the measurement using the visualized muscle attachments. The palpation method was determined to yield valid measurements with an intraclass correlation coefficient (3,1) of .96.

Each subject was eligible to be placed into 1 of 2 groups based on a normalization index calculated from the resting length of their pectoralis minor muscle and their height using the equation: [(pectoralis minor muscle length/height) x 100]. Based on pilot data (n=6, Formula=8.13, SD=0.48), cut points were set at ±1 standard deviation from the mean (<7.65 for the subjects with short pectoralis minor muscle resting lengths, >8.61 for the subjects with long pectoralis minor muscle resting lengths), with subjects falling within ±1 standard deviation of the mean excluded from the analysis. Data on a total of 81 subjects were collected before the target number of 25 subjects per group was achieved. All subjects then performed active arm elevation and lowering in the sagittal, scapular, and frontal planes in a standing position. Three-dimensional scapular kinematics at specific angles of arm elevation were analyzed for differences between the 2 groups,17 with the remaining 31 subjects excluded from the analysis.

Several postural measurements were taken on each subject. In a standing position, the subject’s thoracic spine curvature and resting scapular position were measured. The curve of the thoracic spine was determined by locating the T1 and T12 vertebrae by palpation, marking these spinous processes with a pen, and placing a flexible ruler along the contour of the spine between these landmarks. The ruler was then marked at T1 and T12 before removing it from the subject. The depth of the curve divided by the height of the curve determined a Thoracic Kyphosis Index to quantify the curve of the thoracic spine.21 The resting position of the scapula was determined by measuring the distance from the midpoint of the sternal notch (SN) to the medial aspect of the coracoid process (CP) and the horizontal distance from the posterolateral angle of the acromion (PLA) to the thoracic spine (TS) with a soft tape measure (Fig. 3). The Scapula Index also was calculated as a potential clinical measurement indicating pectoralis minor influence on scapular position, using the equation: [(SN to CP/PLA to TS) x 100].


Figure 3
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  		Figure 3. Scapula Index measurement. Top: sternal notch to coracoid process distance. Bottom: posterolateral angle of scapula to thoracic spine distance.

 
Three-dimensional scapular orientation relative to the trunk in the standing resting position was determined using the electromagnetic motion capture system. Three-dimensional orientation of the scapula was determined using Euler angle sequences recommended by the International Society of Biomechanics.22 In the absence of movement, measurement error due to sensor-skin movement on each segment is virtually eliminated. The scapular orthogonal axis system and rotations about these axes are shown in Figure 1.

In an effort to avoid conscious postural correction, subjects were not told that the measurements were related to alignment or posture, and they were asked to stand in their normal, relaxed position during measurements. Normalized pectoralis minor muscle length group assignment was made after the analysis, so was blinded to group assignment during the posture measurements.

Finally, a supine measurement of the pectoralis minor muscle was taken based on the method of Kendall et al.5 This method quantifies the distance between the treatment table and the PLA. This measurement was taken in 3 different arm positions: with the humerus externally rotated and forearm supinated (ER), with the palm facing the subject’s side (neutral), and with the humerus internally rotated and forearm pronated (IR). A clear plastic ruler with 1-mm increments and the same standard treatment plinth were used for these measurements.

Data Analysis

Calculated means and standard deviations for subject demographics, posture measures and indexes, and the Kendall pectoralis minor muscle measures were tested for differences between pectoralis minor muscle resting length groups using a t test, with statistical significance set at P<.05. Sex was tested for group differences using chi-square analysis, with statistical significance set at P<.05. The strength of the relationship between the posture and pectoralis minor muscle length measures was examined with a Pearson product moment correlation analysis.


   Results
Top
 Abstract
 Introduction
 Method
 Results
Discussion and Conclusions
 References
 
Twenty-five subjects were included in each group for a total of 50 subjects. Demographic characteristics of the subjects are given in Table 1. Sex and weight were significantly different between groups, with more male subjects in the group with long pectoralis minor muscle resting lengths and with that group being heavier than the group with short pectoralis minor muscle resting lengths by 9.16 kg. Descriptive statistics for the posture and resting position measures are given in Table 2. Variables that were significantly different between groups included scapular internal rotation at rest, SN to CP, and the Scapula Index. The supine pectoralis minor muscle measurements were not found to be significantly different between groups.


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  		Table 1. Demographic Variablesa

 

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  		Table 2. Postural and Resting Position Measurementsa

 
Table 3 shows the Pearson correlation outcome, with several of the variables significantly correlated. The SN to CP distance measurement demonstrated the highest correlation with normalized pectoralis minor muscle length (Pectoralis Minor Index) at r=.48. The supine pectoralis minor muscle measurements correlated poorly with the Pectoralis Minor Index.


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  		Table 3. Correlation Coefficients (r) Among Posture Measures and Normalized Pectoralis Minor Muscle Lengtha

 

   Discussion and Conclusions
Top
 Abstract
 Introduction
 Method
 Results
 Discussion and Conclusions
References
 
The purposes of this study were to determine the strength of the relationship between resting postural measurements and pectoralis minor muscle resting length and to investigate how these relationships affect the theorized posture-impairment connection. Several resting position measures were found to be related to normalized pectoralis minor muscle resting length, with resting scapular internal rotation, the Scapula Index, the SN to CP distance, and the Thoracic Kyphosis Index all significantly correlated. Scapular internal rotation, the Scapula Index, and the SN to CP distance also were found to be significantly different between groups separated by normalized pectoralis minor muscle resting length. The Thoracic Kyphosis Index was nearly statistically significant between groups with a probability level of .0504.

Sahrmann9 has proposed that rather than a direct link between alignment deviations and impairment, alignment deviations are likely to be linked to movement dysfunction and movement dysfunction subsequently leads to impairment. The findings of this investigation support this proposal by demonstrating a connection between alignment and an anatomic structure, the pectoralis minor muscle (Fig. 4). Normalized pectoralis minor muscle resting length has been associated with altered scapular kinematics,17 which, in turn, have been linked to pain and functional limitations due to impingement syndrome.10–12 The group of subjects with the short pectoralis minor muscle resting length exhibited increased scapular internal rotation and a shorter SN to CP distance at rest compared with the group of subjects with long pectoralis minor muscle resting lengths. The anatomic structure to pathomechanical alteration link of the model is supported by the kinematic analysis of these same subject groups, which demonstrated that the short pectoralis minor muscle group had increased scapular internal rotation and decreased scapular posterior tilting during arm elevation,17 similar to what has been reported in subjects with impingement.10–12


Figure 4
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  		Figure 4. The alignment-impairment model with supportive literature.

 
If the proposed model is robust for this particular set of variables at the shoulder, subjects with increased scapular internal rotation, relatively shorter pectoralis minor muscle resting lengths, and kinematic alterations may be at risk for developing impingement if exposed to an increase in work or leisure activities involving overhead reaching.23 The kinematic alterations are believed to decrease the available subacromial space, increasing compressive forces on the soft tissues as the acromion and humeral head approximate near 90 degrees of arm elevation.24,25 The findings of this study only support the proposed alignment-impairment model and should not be assumed to indicate a cause-and-effect relationship. In addition, all subjects were asymptomatic at the time of testing, so a direct relationship between resting alignment and impairment cannot be assumed. This analysis confirms only an alignment-anatomical variable relationship, but combined with the kinematic findings,17 it supports an alignment-pathomechanic alteration relationship. Concurrent exploration of the alignment measures, kinematics, and impairments at the shoulder will be necessary to provide further support for the model.

Internal rotation of the scapula at rest was demonstrated to be significantly different between pectoralis minor muscle groups, and was significantly correlated with normalized pectoralis minor muscle length. It also has been found to be increased at rest in throwing athletes, a group with high rates of subacromial impingement.26 Solem-Bertoft et al13 demonstrated a subacromial space decrease in subjects placed into scapular protraction in the plane of the scapula. Scapular protraction in their study was a combination of scapular internal rotation and lateral translation.13 The increased scapular internal rotation demonstrated by the short pectoralis minor muscle group in the current study was found in relaxed standing, which cannot be assumed to also indicate movement dysfunction. However, the relatively short pectoralis minor muscle group also demonstrated significantly increased internal rotation dynamically.17 This finding may indicate that subjects who demonstrate scapular medial border winging or excessive protraction at rest also will display increased scapular internal rotation during arm elevation. Further analysis of the consistency of this alignment-movement dysfunction relationship is indicated.

As scapular internal rotation and pectoralis minor muscle length were measured with an electromagnetic motion capture system that is not readily available in most clinics, clinical posture measurements that similarly capture scapular orientation would be beneficial. A literature search for posture measures at the shoulder resulted in conflicting evidence regarding the validity and reliability of data obtained with currently available measures,27–30 and the measures were not demonstrated to be correlated with movement or impairment. In addition, these measures capture primarily linear distances of the scapula relative to the trunk or a global reference, rather than scapular orientation. The Scapula Index was developed as a new measure, intended to capture primarily the transverse-plane orientation of the scapula. An increase in protraction or internal rotation at rest should result in a decreased SN to CP distance, an increased TS to PLA distance, and a smaller Scapula Index. This measure is thought to have 2 advantages: the measurement is taken with the person in a standing position, which accounts for the normal effect of gravity on the individual, and it is a normalized value, not influenced by a person’s stature.

The current study supports the Scapula Index as useful for measuring scapular alignment because it is moderately correlated with scapular internal rotation as measured with the Flock of Birds. The SN to CP measure also correlates with scapular internal rotation and is more highly correlated with the Pectoralis Minor Index. It may be a simple measure to help identify an impingement risk factor; however, the stature of the individual will influence this measure. An exploration of validity and reliability for both the Scapula Index and the SN to CP distance and, if indicated, development of normative values should occur before widespread clinical use of these measures commences. In addition, the group differences demonstrated in this analysis must not be interpreted to mean that all subjects with increased scapular internal rotation or lower Scapula Index values also will have scapular kinematic alterations.

The results do not support the use of supine measurements5 for determining pectoralis minor muscle resting length because these measures were poorly correlated with the Pectoralis Minor Index and were not determined to be different between groups separated by pectoralis minor muscle length. Furthermore, the measures systematically increased with increased amounts of humerus internal rotation. Potential reasons for the failure to demonstrate differences between groups are the influence of the table on the position of the scapula, the alteration in the effect of gravity on the shoulder complex, and the lack of normalization to remove the influence of a person’s stature. The findings of the current study, therefore, question the validity of measurements of pectoralis minor muscle length taken with the individual positioned supine.

Previous investigators2,3 have attempted to find a direct link between alignment deviations and shoulder impairment. Griegel-Morris et al3 attempted to determine theincidence and severity of postural abnormalities in subjects who were healthy and to determine whether postural abnormalities were associated with pain. They found no significant differences between age groups in incidence of postural faults and no relationship between severity of postural abnormality and pain frequency or pain severity. Greenfield et al2 attempted to determine the relationship of posture and function between patients with overuse injuries of the shoulder and age- and sex-matched subjects who were asymptomatic for overuse injuries of the shoulder. Both groups were compared for differences and symmetry of postural variables, with demonstrated differences noted between groups only for forward head position in the patient group.

A recent analysis indicates that a change in resting posture can influence impairment. Lewis and colleagues31 examined shoulder range of motion and pain in subjects with and without subacromial impingement before and after applying a taping technique aimed at normalizing posture. Subjects with impingement demonstrated increased pain-free range of shoulder flexion and scapular-plane abduction after postural taping; however, pain measurements did not significantly change in these subjects when tested immediately.

These studies provide examples of the difficulty in directly relating posture to impairment. Demonstrating a direct relationship between posture and impairment will likely be elusive for several reasons. First, there are a high number of posture variables in each of the cardinal planes that are considered to be important, making it difficult to isolate the specific variable causing impairment or to determine interactions among variables. Second, the degree of deviation that results in impairment is unknown and is likely to be different between individuals. Third, current posture measures may not be valid as most are linear distances attempting to describe 3-dimensional segment orientations. Fourth, the affect of time is not usually considered a variable. It is unknown how long an individual must sustain a specific alignment deviation before impairments begin.

Several limitations existed in the current study. The Scapula Index and its components (SN to CP distance and TS to PLA distance) have not been validated or tested for reliability, but were theoretically based. It is possible that subcutaneous tissue bulk could influence these measures, although it is unlikely that one group and not the other would be influenced by this variable. Psychometric testing of these variables is indicated. The study also was performed on subjects who were asymptomatic for shoulder pathology, and the results cannot be generalized to people with impingement of the shoulder. In addition, the findings are based on group data and therefore should not be applied to an individual without further testing to confirm the relationships among these variables. It is also possible that subjects were not in their normal resting posture during the time the measurements were made. This possibility would be assumed to be systematic, however, rather than occurring in one group only.

The proposed model is a theoretical framework intended to stimulate the examination of the posture-impairment relationship. The model uses resting posture variables, pectoralis minor muscle length, scapular kinematics, and pain or functional limitation as examples and may or may not be applicable to other body regions.


   Footnotes
 
* Innovative Sports Training Inc, 3711 North Ravenswood, Suite 150, Chicago, IL 60613. Back


   References
Top
 Abstract
 Introduction
 Method
 Results
 Discussion and Conclusions
 References
 

  1. Finley MA, Lee RY. Effect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors. Arch Phys Med Rehabil84 2003563–568[ISI][Medline]
  2. Greenfield B, Catlin PA, et al. Coats PW. Posture in patients with shoulder overuse injuries and healthy individuals. J Orthop Sports Phys Ther21 1995287–295[ISI][Medline]
  3. Griegel-Morris P, Larson K, Mueller-Klaus K, Oatis CA. Incidence of common postural abnormalities in the cervical, shoulder, and thoracic regions and their association with pain in two age groups of healthy subjects. Phys Ther72 1992425–431[Abstract/Free Full Text]
  4. Kebaetse M, McClure P, Pratt NA. Thoracic position effect on shoulder range of motion, strength, and three-dimensional scapular kinematics. Arch Phys Med Rehabil80 1999945–950[ISI][Medline]
  5. Kendall FP, McCreary EK, Provance PG. Muscles: Testing and Function 4th ed. Baltimore, Md: Williams & Wilkins 1993
  6. Novak CB, Mackinnon SE. Repetitive use and static postures: a source of nerve compression and pain. J Hand Ther10 1997151–159[Medline]
  7. Sahrmann SA. Diagnosis and Treatment of Movement Impairment Syndromes St Louis, Mo: Mosby; 2002
  8. Lewis JS, Green A, Wright C. Subacromial impingement syndrome: the role of posture and muscle imbalance. J Shoulder Elbow Surg14 2005385–392[ISI][Medline]
  9. Sahrmann SA. Does postural assessment contribute to patient care? J Orthop Sports Phys Ther32 2002376–379[ISI][Medline]
  10. Lukasiewicz AC, McClure P, Michener L, et al. Comparison of 3-dimensional scapular position and orientation between subjects with and without shoulder impingement. J Orthop Sports Phys Ther29 1999574–583[ISI][Medline]
  11. Ludewig PM, Cook TM. Alterations in shoulder kinematics and associated muscle activity in people with symptoms of shoulder impingement. Phys Ther80 2000276–291[Abstract/Free Full Text]
  12. Hebert LJ, Moffet H, McFadyen BJ, Dionne CE. Scapular behavior in shoulder impingement syndrome. Arch Phys Med Rehabil83 200260–69[ISI][Medline]
  13. Solem-Bertoft E, Thuomas KA, Westerberg CE. The influence of scapular retraction and protraction on the width of the subacromial space: an MRI study. Clin Orthop(296) 199399–103[Medline]
  14. Brossmann J, Preidler KW, Pedowitz RA, et al. Shoulder impingement syndrome: influence of shoulder position on rotator cuff impingement: an anatomic study. AJR Am J Roentgenol167 19961511–1515[Abstract/Free Full Text]
  15. Flatow EL, Soslowsky LJ, Ticker JB, et al. Excursion of the rotator cuff under the acromion. Patterns of subacromial contact. Am J Sports Med22 1994779–788[Abstract/Free Full Text]
  16. Lee SB, Itoi E, O’Driscoll SW. An KN, Contact geometry at the undersurface of the acromion with and without a rotator cuff tear. Arthroscopy17 2001365–372[ISI][Medline]
  17. Borstad JD, Ludewig PM. The effect of long versus short pectoralis minor resting length on scapular kinematics in healthy individuals. J Orthop Sports Phys Ther35 2005227–238[ISI][Medline]
  18. Magee DJ. Orthopedic Physical Assessment 4th ed. Philadelphia, Pa: WB Saunders Co; 2002
  19. Barnett ND, Duncan RD, Johnson GR. The measurement of three dimensional scapulohumeral kinematics: a study of reliability. Clin Biomech14 1999287–290[Medline]
  20. Karduna AR, McClure PW, Michener LA, Sennett B. Dynamic measurements of three-dimensional scapular kinematics: a validation study. J Biomech Eng123 2001184–190[ISI][Medline]
  21. Hinman MR. Interrater reliability of flexicurve postural measures among novice users. J Back Musculoskeletal Rehabil17 200333–36[ISI]
  22. Wu G, van der Helm FC, Veeger HE, et al. ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion, part II: shoulder, elbow, wrist and hand. J Biomech38 2005981–992[ISI][Medline]
  23. Soslowsky LJ, Thomopoulos S, Esmail A, et al. Rotator cuff tendinosis in an animal model: role of extrinsic and overuse factors. Ann Biomed Eng30 20021057–1063[ISI][Medline]
  24. Graichen H, Bonel H, Stammberger T, et al. Three-dimensional analysis of the width of the subacromial space in healthy subjects and patients with impingement syndrome. AJR Am J Roentgenol172 19991081–1086[Abstract/Free Full Text]
  25. Graichen H, Bonel H, Stammberger T, et al. Subacromial space width changes during abduction and rotation: a 3-D MR imaging study. Surg Radiol Anat21 199959–64[ISI][Medline]
  26. Myers JB, Laudner KG, Pasquale MR, et al. Scapular position and orientation in throwing athletes. Am J Sports Med33 2005263–271[Abstract/Free Full Text]
  27. Peterson DE, Blankenship KR, Robb JB, et al. Investigation of the validity and reliability of four objective techniques for measuring forward shoulder posture. J Orthop Sports Phys Ther25 199734–42[ISI][Medline]
  28. Plafcan DM, Turczany PJ, Guenin BA, et al. An objective measurement technique for posterior scapular displacement. J Orthop Sports Phys Ther25 1997336–341[ISI][Medline]
  29. Harrison AL, Barry-Greb T, Wojtowicz G. Clinical measurement of head and shoulder posture variables. J Orthop Sports Phys Ther23 1996353–361[ISI][Medline]
  30. Gibson MH, Goebel GV, Jordan TM, et al. A reliability study of measurement techniques to determine static scapular position. J Orthop Sports Phys Ther21 1995100–106[ISI][Medline]
  31. Lewis JS, Wright C, Green A. Subacromial impingement syndrome: the effect of changing posture on shoulder range of movement. J Orthop Sports Phys Ther35 200572–87[ISI][Medline]



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