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Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study
Musculoskeletal Science and Practice xxx (2017) 1e7
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Technical and measurement report
Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study Wan-Yu Du, MS. a, Tsun-Shun Huang, PhD. a, Kai-Chieh Hsu, MS. b, Jiu-Jenq Lin, PhD. a, c, * a b c
School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, 100 Taipei, Taiwan Department of Mechanical Engineering, College of Engineering, National Taiwan University, 100 Taipei, Taiwan Division of Physical Therapy, Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 May 2017 Received in revised form 10 August 2017 Accepted 12 August 2017
Background: Previous studies have proposed various ways to assess scapular dyskinesis. In clinic, assessment tools designed to measure the posterior displacement of the inferior angle of the scapula with reference to the posterior thoracic cage are needed. Objectives: A novel scapulometer was developed to measure scapular medial border and inferior angle prominence. Methods: A novel scapulometer was designed to measure the distance from the root of the spine (ROS) and the inferior angle (INF) of the scapula to the thorax wall in 29 participants with scapular dyskinesis bilaterally. Two raters measured the ROS and INF distance of the scapula 3 times bilaterally. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were calculated to determine the inter-rater and intra-rater reliability. Validity was based on correlations (convergent: ROS and internal/ external rotation, and INF and tilt; divergent: ROS/INF and upward rotation of the scapula) using a FASTRAK Polhemus 3-D motion tracking system assessing scapular tilt, internal/external rotation, and upward/downward rotation. Results: The average ROS and INF displacements were 13.7 ± 5.0 mm and 12.5 ± 6.3 mm, respectively. The results showed excellent intra-rater and inter-rater reliability, with ICC ¼ 0.88e0.99 and 0.95e0.99 (SEM ¼ 0.7e0.8 mm), respectively. Correlations were 0.35/0.19 (convergent validity) and 0.07/0.09 (divergent validity). Conclusions: The novel scapulometer has excellent reliability and fair validity to quantify medial border and inferior angle prominence of the scapula. Further research utilizing this instrument is recommended. © 2017 Published by Elsevier Ltd.
Keywords: Dyskinesis Scapulometer Reliability Validity
1. Introduction Scapular dyskinesis is defined as abnormal static scapular position and/or scapular motion during arm motion or in the resting position (Kibler and Sciascia, 2010). Types of scapular dyskinesis were established by a previous study where types I, II, III, and IV in addition to mixed patterns represent various abnormal resting scapula postures (Huang et al., 2015b). Prominence of the scapular medial border and inferior angle is a common characteristic in
* Corresponding author. School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taiwan. E-mail address: [email protected] (J.-J. Lin).
patients with scapular dyskinesis (Huang et al., 2015b). Altered scapular alignment and kinematics change the force transmission and may be associated with shoulder injuries, including shoulder impingement, rotator cuff disease, labral injury, clavicle fractures, AC joint pathology, and shoulder instability, with prevalence rates of 33e100% (Kibler et al., 2012, 2013; Ludewig and Reynolds, 2009). Thus, for patients with scapular dyskinesis, it is essential to assess scapular kinematics. Previous studies have proposed various ways to assess scapular dyskinesis. Laboratory instruments such as 3-D motion analysis systems provide quantitative data on movements of the scapula (Lin et al., 2006; Ludewig and Cook, 2000; Tate et al., 2009); however, such systems are impractical in clinical settings. Visionbased assessments for classifying scapular dyskinesis based on
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Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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scapular abnormal position/movement patterns have been proposed by several authors (Kibler et al., 2002; Tate et al., 2009; Uhl et al., 2009), and McClure classified scapular dyskinesis according to the severity of abnormal scapular motion (McClure et al., 2009). Neither method, however, has sufficient reliability (kappa coefficient ¼ 0.31e0.42 and 0.48e0.61, respectively). The lateral scapular slide test (LSST) was developed to determine the distance between the inferior angle of the scapula and the corresponding vertebra in various shoulder abduction positions (Kibler, 1998; Koslow et al., 2003; Odom et al., 2001; Ozunlu et al., 2011; Shadmehr et al., 2010). Scapular dyskinesis was identified if scapular asymmetry occurred. Although some studies reported reasonable reliability and agreement of the method (Odom et al., 2001; Shadmehr et al., 2010), the validity was insufficient (sensitivity 35e43%, specificity 26e56%) (Koslow et al., 2003; Odom et al., 2001). The clinical utility of the method is questionable because asymmetrical scapular positions were reported in both symptomatic and asymptomatic populations (Koslow et al., 2003; Ozunlu et al., 2011). Other assessment tools have been designed to measure the posterior displacement of the inferior angle of the scapula with reference to the posterior thoracic cage (Oliveira et al., 2015; Plafcan et al., 1997; Struyf et al., 2009; Weon et al., 2011). Plafcan et al. (1997) designed the Perry Tool to measure the posterior displacement angle between the frontal plane and a line joining the spinous process to the scapular inferior angle, while Weon et al. (2011) and Oliveira et al. (2015) designed a scapulometer to measure the posterior displacement of the scapular inferior angle relative to the thoracic cage. Both studies reported excellent intrarater and inter-rater results, ICC 0.97e0.99 and ICC 0.92e0.97, respectively. However, the validity of these measures of scapular dyskinesis was questioned. Measurement of the posterior displacement angle with the Perry Tool can be affected by the extent of scapular abduction. Additionally, measurement of the posterior displacement of the scapular inferior angle with Weon's and Oliveira's Tools, stationed bilaterally on the posterior thorax, can be affected by muscle mass asymmetry on the two sides (Lucki and Nicolay, 2007; Rogowski et al., 2008). Prominence of the scapular medial border and the inferior angle is common in patients with scapular dyskinesis (Huang et al.,
2015b), so it is essential that a tool for clinical assessment be developed. To our knowledge, tools for scapular dyskinesis measurement with acceptable reliability and validity are unavailable. In this study, we aimed to develop an assessment tool for measuring the posterior displacement of the scapular medial border and inferior angle with reference to the posterior thoracic cage unilaterally. The reliability and validity of the assessment tool were examined in participants with scapular dyskinesis. 2. Methods Twenty-nine asymptomatic participants with scapular dyskinesis (23 ± 2.1 years old, 14 males, 26 right-handed) were recruited from a university hospital and through the local media. A physical therapist with a minimum of 3 years of clinical experience assessed the subjects for eligibility. Scapular dyskinesis was characterized as medial border and/or inferior angle prominence of the scapula at resting position with arms by side (Huang et al., 2015a). Participants were excluded if they (1) had a body mass index (BMI) of under 18 or over 24; (2) had difficulty maintaining a stable neutral position of the scapula; (3) had a diagnosis of long thoracic nerve or accessory nerve injury; or (4) had past or present musculoskeletal conditions affecting the cervical or thoracic spine, glenohumeral joint, or acromioclavicular joints. All recruited subjects signed consent forms approved by the institutional review board. The scapulometer in this study was modified from the Weon tool (Weon et al., 2011). The modified scapulometer was stationed at one side to measure the distance from the root of the spine (ROS) and the inferior angle (INF) of the scapula to the thoracic wall, respectively. For the measurement, right and left scapulometers were made for each side. This modified scapulometer had two parts: a digital caliper (HANLIN 1052, Taiwan) and a ruler body. The digital caliper, designed for up to 150 mm linear measurements with minimum measurement error of 1 mm, was perpendicularly attached at the distal end of a 15-cm ruler body. Additionally, an inclinometer was attached to the ruler body to maintain the orientation of the scapulometer (Fig. 1). Before conducting the test, two anatomic landmarks, ROS and INF, were identified and marked. Then two parallel landmarks on the same
Fig. 1. Modified scapulometer, with ruler A and digital caliper C designed to measure prominence of the scapular medial border and inferior angle. An inclinometer B was attached to the body to maintain scapulometer orientation.
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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level of the ROS and INF, approximately 1 cm medial to the scapular medial border, were marked. To measure scapular dyskinesis (prominence of the scapular medial border and inferior angle), one rater stood behind the subject and placed the ruler body of the modified scapulometer on the anatomic landmark and the digital caliper on the parallel landmark (Fig. 2). Holding the modified scapulometer in place with one hand on the ruler body, the first rater slid the digital caliper anteriorly toward the parallel landmark until firm contact. Posterior displacement of the scapula was recorded by the second rater based on the digital caliper. Stabilizing the modified scapulometer on only one side of the scapular medial border prevents the tool from tipping sideways. This modification of the tool further prevents muscle asymmetry from influencing measurement results. During the measurement, an inclinometer attached to the ruler body was monitored to maintain the orientation of the scapulometer. All measurements were performed with the subject in a relaxed sitting position with arms by side. The subjects were not instructed to alter their
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posture alignment. During the measurements, both raters were blinded to the results. Both raters were physical therapists with a minimum of 3 years of clinical experience. The intra-rater reliability of the measurement was assessed for one of the raters. Measurements were repeated 3 times on both sides in randomized order. The scapular dyskinesis measurement was taken as described in the previous section. Two raters were involved in assessing interrater reliability. One rater assessed the scapular dyskinesis as outlined in the methods section. The second rater then repeated the measure on the same scapula within 20 min. Both raters were blinded to the results of the measurements. Before conducting a measurement, a pressure meter (Force Ten FDX, Wagner, USA) placed on the parallel landmarks was used as a practice guide to calibrate the pressure applied to the participant between the 2 raters. The FASTRAK Polhemus 3-D (Polhemus Inc., Colchester, VT, USA) motion tracking system with Motion Monitor software was used to capture scapular kinematics as a standard measurement for validation. It has been reported by the manufacturer that the system has an accuracy of 0.8 mm and 0.15 . Excellent reliability (ICC 0.62e0.81) was reported, and validation of this method was established with correlations of the movement of pins in the scapula (Jordan et al., 2000; Karduna et al., 2001). The device has been used in many validity studies (Ha et al., 2013; Ribeiro et al., 2011). Sensors were attached to the sternum, flat surface of the acromion, and distal humerus, and local coordinate systems were marked with a stylus by an experienced physical therapist. Raw kinematic data were lowpass filtered at a 6-Hz cutoff frequency and converted into anatomically defined rotations. In general, the ISB guidelines were followed for constructing a shoulder joint coordinate system (Wu et al., 2005). The scapular orientation relative to the thorax was described using a Euler angle sequence of rotation about Zs (internal/external), rotation about Y's (downward/upward rotation), and rotation about X00 s (posterior/anterior tipping) (Fig. 3). The therapist guided the participant's scapula from resting to neutral position (disappearance of prominence) (Kibler et al., 2002). The differences in scapular position between dyskinesis (resting position) and neutral position were calculated, including tilt, internal/external rotation, and upward rotation of the scapula. Intraclass correlation coefficients (ICC (3.1)) were calculated based on a repeated measure analysis of variance to determine inter-rater reliability. The ICC (3.3) was calculated for intra-rater reliability. An ICC of greater than 0.75 indicates good reproducibility; one of less than 0.75, poor reproducibility (Portney and Watkins, 2000). Additionally, the standard error of measurement (SEM) was used to determine the measurement error. Pearson correlation between ROS and internal/external rotation and between INF and anterior/posterior tilt were calculated to represent convergent validity. Pearson correlations between ROS/ INF and upward rotation of the scapula represented divergent validity. 3. Results
Fig. 2. Landmarks and scapulometer measurement, a: rear view; b: superior view. The ruler was placed on the anatomic landmark while the digital caliper was placed on the parallel landmark. Posterior displacement of the scapula was measured by sliding the digital caliper toward the thorax until firm contact. A: Root of spine of scapular landmark. B: Parallel landmark at the same level of root of spine of scapula 1 cm medially to the scapular medial border.
The average ROS and INF displacements were 13.7 ± 5.0 mm and 12.5 ± 6.3 mm, respectively. The results of intra-rater and interrater reliability were ICC ¼ 0.88e0.99 and 0.95e0.99 (SEM ¼ 0.7e0.8 mm), respectively (Table 1). The convergent validity correlations were 0.35 (p ¼ 0.05) and 0.19 (p ¼ 0.86) for ROS/ internal rotation and INF/anterior tilt (Fig. 4), respectively, while the divergent validity correlations were 0.07 (p ¼ 0.661) and 0.09 (p ¼ 0.629) for ROS/upward rotation and INF/upward rotation, respectively (Table 2).
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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Fig. 3. Scapular orientation relative to the proposed scapular dyskinesis, prominence of medial border or inferior angle. RS: root of spine of scapula; IA: inferior angle of scapula.
and a standard error of measurement of 1.7 mm. Using a scapular medial border posterior displacement measurement device, Hong et al. (2011). found ICC values close to or above 0.90, with a standard error of measurement of 1.5e1.6 mm. Similarly, a scapulometer proposed by Weon et al. (2011). and Oliveira et al. (2015). presented values of 0.89e0.97 and 1 mm for reliability and standard error, respectively. However, these studies did not distinguish different types of dyskinesis, focusing only on the medial border, nor did they count mass asymmetry on both sides. Measuring the prominence of the scapular medial border and inferior angle specific to dyskinesis types, the modified scapulometer in the current study achieved excellent ROS and INF displacement reliability. The validity outcomes for objective measurement tools from previous studies are unknown or uncertain (Odom et al., 2001; Oliveira et al., 2015; Plafcan et al., 1997; Shadmehr et al., 2010; Weon et al., 2011). While some studies did not test the validity (Odom et al., 2001; Plafcan et al., 1997), others (Oliveira et al., 2015; Shadmehr et al., 2010; Weon et al., 2011) did not distinguish different type of dyskinesis. In the present study, in addition to distinguishing different types of dyskinesis, we used a 3-D motion capture system as a standard device to validate the measurement of the modified scapulometer. In theory, scapular dyskinesis with excessive scapular internal rotation (medial border prominence)
4. Discussion The present study aimed to assess a newly-developed instrument for measuring the posterior displacement of the scapular medial border and inferior angle with reference to the posterior thoracic cage unilaterally. The intra-rater and inter-rater reliability and the convergent and divergent validity of the measure were evaluated. Our results showed that the modified scapulometer had excellent reliability and good convergent/divergent validity, with fair correlations for ROS/internal rotation and INF/ anterior tilt. This supports our proposed kinematics between scapular internal rotation and medial border prominence, as well as that between scapular anterior tilt and inferior angle prominence (Fig. 3). Regarding reliability, the modified scapulometer had excellent intra-rater and inter-rater ICCs, with values above 0.88 and a standard error of 0.7e0.8 mm. These results are indicative of sufficiently good reliability for clinical use. Previous studies (Hong et al., 2011; Oliveira et al., 2015; Struyf et al., 2009; Weon et al., 2011) that examined and quantified the displacement of the scapula also showed good to excellent reliability values. Measuring the distance between the posterior border of the acromion and the thoracic wall with the modified lateral scapular slide test, Strufy et al (Struyf et al., 2009). found ICC values of 0.72
Table 1 Intra-rater and inter-rater reliability of scapular posterior displacement measurement. Raters Rater 1 Rater 2 Inter-rater ICC (3,3) a b c
Landmarks b
ROS (mm) INFc (mm) ROS (mm) INF (mm) ROS INF
Trial 1 13.8 12.5 13.4 12.6
± ± ± ±
Trial 2 5.2 6.4 5.1 6.4
13.7 12.5 13.3 12.6
± ± ± ±
Trial 3 4.9 6.2 5.3 6.3
13.8 12.5 13.5 12.5
± ± ± ±
Intra-rater ICC (3,1)a
Mean 4.9 6.3 5.3 6.3
13.8 12.5 13.4 12.6
± ± ± ±
5.0 6.3 5.1 6.3
0.97e0.98 0.97e0.99 0.88e0.97 0.97e0.98 0.95 0.99
ICC Intra-class correlation. ROS: Root of spine of scapula posterior displacement. INF: Scapular inferior angle posterior displacement.
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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Fig. 4. Correlation between scapulometer measurement and scapula kinematics. A. Correlation of scapula internal rotation and ROS (r ¼ 0.35). B. Correlation of scapula anterior tilt and INF. ROS: root of spine; INF: inferior angle of scapula.
and anterior tipping (inferior angle prominence) are related to posterior displacement of the root of the spine and the inferior angle of the scapula, respectively (Kibler et al., 2013). Our convergent and divergent correlation results support this proposition; we found fair correlations between ROS/internal rotation, and no correlations between ROS/upward rotation and INF/upward rotation.
Thus, our measurement provides quantification of impairment of the internal rotation of the scapula by the root of spine prominence in subjects with dyskinesis. The amount of impairment is important to consider during rehabilitation for symptomatic dyskinesis subjects, which is highly related to decreased subacrominal space
Table 2 Validity between scapulometer measurement and 3-D motion measurements. Items Convergent validity ROSa * int/extb INFc * ant/postd Divergent validity ROSa * ure INFc * ur a b c d e
Scapulometer measurement
Three-dimensional measurement
Correlation
13.4 ± 5.1 mm 12.6 ± 6.3 mm
7.5 ± 3.1 1.9 ± 1.4
0.35 (p ¼ 0.05) 0.18 (p ¼ 0.86)
13.4 ± 5.1 mm 12.6 ± 6.3 mm
2.4 ± 2.1 2.4 ± 2.1
0.07 (p ¼ 0.661) 0.09 (p ¼ 0.629)
ROS: Root of spine of scapula posterior displacement. int/ext: scapular internal/external rotation. INF: Scapular inferior angle posterior displacement. ant/post: scapular anterior/posterior tilt. ur: scapular upward rotation.
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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impingement syndrome (Lukasiewicz et al., 1999; McClure et al., 2006; Solem-Bertoft et al., 1993). The measurement validity of the modified scapulometer can be influenced by several factors. First, the neutral positions for dyskinesis measurement are not standardized. The “neutral” position was determined subjectively by a therapist, who actively guided the scapula back to the rib cage to minimize any bony prominence of the scapula. However, the “neutral” position of the scapula may be influenced by the thickness of the subject's subcutaneous tissue or contraction of scapular muscles. Thus, subjective judgment may under-estimate the degree of scapular dyskinesis. Second, subjects who have excessive scapular anterior tilt may be unable to actively place their scapula in the “neutral” position due to tightness of the anterior shoulder tissue (i.e., pectoralis minor muscle), which is a common cause of scapular dyskinesis (Ludewig and Reynolds, 2009). Participants with anterior shoulder tightness, who being unable to maintain the scapula in the neutral position, were not included in the study. Thus, the validity may have been under or over-estimated. Third, a three-dimensional electromagnetic device was used as a comparison standard in this study. The correlations between scapular internal rotation/anterior tipping and ROS/INF were fair to poor. These modest results may be related to the standard chosen in the present study. The sensors for scapular motion capture were placed on the flat surface of the acromion. During motion, the sensor may be influenced by the movement of the skin beneath the sensor. Therefore, it may not be the most suitable device for validating the modified scapulometer. Although imaging such as x-ray or MRI may provide more direct access to the direction of scapular posterior prominence with reference to the posterior thoracic cage, no standard positions or views for scapular dyskinesis imaging have been established to date. In addition, imaging examination increases the risk of radiation exposure for participants. Given the above concerns, we chose the 3-D electromagnetic device as a substitute comparison standard. There are some limitations of this study that need to be considered. First, the results of this study are not generalizable to symptomatic participants with scapular dyskinesis. Second, measurement was applied to dyskinesis subjects with medial border and/or inferior angle prominence, the tool may not be applicable to those who have excessively abducted scapulae dyskinesis. Third, this tool is designed to measure two-dimensional scapular orientation in the resting position; therefore, it may not be applicable to dynamic or functional use. Future studies with symptomatic and various type of dyskinesis subjects should be conducted to investigate whether the amount of posterior displacement can be detected for classification of symptomatic dyskinesis. 5. Conclusion In clinical practice, it is important to consider that the current tool, which measures common prominence of the scapular medial border and inferior angle, could provide advantages by eliminating the need for expensive equipment, maintenance, and software for data analysis. The modified scapulometer is inexpensive and easily accessible. Having excellent reliability and fair validity to quantify prominence of the scapular medial border and inferior angle, this instrument is recommended for use in evaluation and in measurement of treatment outcomes for patients with symptomatic dyskinesis. Further research utilizing this instrument is recommended. Acknowledgments This study was supported by the Ministry of Science and Technology, 104-2314-B-002-026-MY3, Taiwan.
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Weon, J.H., Kwon, O.Y., Cynn, H.S., Lee, W.H., Kim, T.H., Yi, C.H., 2011. Real-time visual feedback can be used to activate scapular upward rotators in people with scapular winging: an experimental study. J. Physiother. 57 (2), 101e107. Wu, G., van der Helm, F.C., Veeger, H.E., Makhsous, M., Van Roy, P., Anglin, C., et al., 2005. ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motionePart II: shoulder, elbow, wrist and hand. J. Biomech. 38 (5), 981e992.
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Technical and measurement report
Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study Wan-Yu Du, MS. a, Tsun-Shun Huang, PhD. a, Kai-Chieh Hsu, MS. b, Jiu-Jenq Lin, PhD. a, c, * a b c
School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, 100 Taipei, Taiwan Department of Mechanical Engineering, College of Engineering, National Taiwan University, 100 Taipei, Taiwan Division of Physical Therapy, Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 May 2017 Received in revised form 10 August 2017 Accepted 12 August 2017
Background: Previous studies have proposed various ways to assess scapular dyskinesis. In clinic, assessment tools designed to measure the posterior displacement of the inferior angle of the scapula with reference to the posterior thoracic cage are needed. Objectives: A novel scapulometer was developed to measure scapular medial border and inferior angle prominence. Methods: A novel scapulometer was designed to measure the distance from the root of the spine (ROS) and the inferior angle (INF) of the scapula to the thorax wall in 29 participants with scapular dyskinesis bilaterally. Two raters measured the ROS and INF distance of the scapula 3 times bilaterally. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were calculated to determine the inter-rater and intra-rater reliability. Validity was based on correlations (convergent: ROS and internal/ external rotation, and INF and tilt; divergent: ROS/INF and upward rotation of the scapula) using a FASTRAK Polhemus 3-D motion tracking system assessing scapular tilt, internal/external rotation, and upward/downward rotation. Results: The average ROS and INF displacements were 13.7 ± 5.0 mm and 12.5 ± 6.3 mm, respectively. The results showed excellent intra-rater and inter-rater reliability, with ICC ¼ 0.88e0.99 and 0.95e0.99 (SEM ¼ 0.7e0.8 mm), respectively. Correlations were 0.35/0.19 (convergent validity) and 0.07/0.09 (divergent validity). Conclusions: The novel scapulometer has excellent reliability and fair validity to quantify medial border and inferior angle prominence of the scapula. Further research utilizing this instrument is recommended. © 2017 Published by Elsevier Ltd.
Keywords: Dyskinesis Scapulometer Reliability Validity
1. Introduction Scapular dyskinesis is defined as abnormal static scapular position and/or scapular motion during arm motion or in the resting position (Kibler and Sciascia, 2010). Types of scapular dyskinesis were established by a previous study where types I, II, III, and IV in addition to mixed patterns represent various abnormal resting scapula postures (Huang et al., 2015b). Prominence of the scapular medial border and inferior angle is a common characteristic in
* Corresponding author. School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taiwan. E-mail address: [email protected] (J.-J. Lin).
patients with scapular dyskinesis (Huang et al., 2015b). Altered scapular alignment and kinematics change the force transmission and may be associated with shoulder injuries, including shoulder impingement, rotator cuff disease, labral injury, clavicle fractures, AC joint pathology, and shoulder instability, with prevalence rates of 33e100% (Kibler et al., 2012, 2013; Ludewig and Reynolds, 2009). Thus, for patients with scapular dyskinesis, it is essential to assess scapular kinematics. Previous studies have proposed various ways to assess scapular dyskinesis. Laboratory instruments such as 3-D motion analysis systems provide quantitative data on movements of the scapula (Lin et al., 2006; Ludewig and Cook, 2000; Tate et al., 2009); however, such systems are impractical in clinical settings. Visionbased assessments for classifying scapular dyskinesis based on
http://dx.doi.org/10.1016/j.msksp.2017.08.004 2468-7812/© 2017 Published by Elsevier Ltd.
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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scapular abnormal position/movement patterns have been proposed by several authors (Kibler et al., 2002; Tate et al., 2009; Uhl et al., 2009), and McClure classified scapular dyskinesis according to the severity of abnormal scapular motion (McClure et al., 2009). Neither method, however, has sufficient reliability (kappa coefficient ¼ 0.31e0.42 and 0.48e0.61, respectively). The lateral scapular slide test (LSST) was developed to determine the distance between the inferior angle of the scapula and the corresponding vertebra in various shoulder abduction positions (Kibler, 1998; Koslow et al., 2003; Odom et al., 2001; Ozunlu et al., 2011; Shadmehr et al., 2010). Scapular dyskinesis was identified if scapular asymmetry occurred. Although some studies reported reasonable reliability and agreement of the method (Odom et al., 2001; Shadmehr et al., 2010), the validity was insufficient (sensitivity 35e43%, specificity 26e56%) (Koslow et al., 2003; Odom et al., 2001). The clinical utility of the method is questionable because asymmetrical scapular positions were reported in both symptomatic and asymptomatic populations (Koslow et al., 2003; Ozunlu et al., 2011). Other assessment tools have been designed to measure the posterior displacement of the inferior angle of the scapula with reference to the posterior thoracic cage (Oliveira et al., 2015; Plafcan et al., 1997; Struyf et al., 2009; Weon et al., 2011). Plafcan et al. (1997) designed the Perry Tool to measure the posterior displacement angle between the frontal plane and a line joining the spinous process to the scapular inferior angle, while Weon et al. (2011) and Oliveira et al. (2015) designed a scapulometer to measure the posterior displacement of the scapular inferior angle relative to the thoracic cage. Both studies reported excellent intrarater and inter-rater results, ICC 0.97e0.99 and ICC 0.92e0.97, respectively. However, the validity of these measures of scapular dyskinesis was questioned. Measurement of the posterior displacement angle with the Perry Tool can be affected by the extent of scapular abduction. Additionally, measurement of the posterior displacement of the scapular inferior angle with Weon's and Oliveira's Tools, stationed bilaterally on the posterior thorax, can be affected by muscle mass asymmetry on the two sides (Lucki and Nicolay, 2007; Rogowski et al., 2008). Prominence of the scapular medial border and the inferior angle is common in patients with scapular dyskinesis (Huang et al.,
2015b), so it is essential that a tool for clinical assessment be developed. To our knowledge, tools for scapular dyskinesis measurement with acceptable reliability and validity are unavailable. In this study, we aimed to develop an assessment tool for measuring the posterior displacement of the scapular medial border and inferior angle with reference to the posterior thoracic cage unilaterally. The reliability and validity of the assessment tool were examined in participants with scapular dyskinesis. 2. Methods Twenty-nine asymptomatic participants with scapular dyskinesis (23 ± 2.1 years old, 14 males, 26 right-handed) were recruited from a university hospital and through the local media. A physical therapist with a minimum of 3 years of clinical experience assessed the subjects for eligibility. Scapular dyskinesis was characterized as medial border and/or inferior angle prominence of the scapula at resting position with arms by side (Huang et al., 2015a). Participants were excluded if they (1) had a body mass index (BMI) of under 18 or over 24; (2) had difficulty maintaining a stable neutral position of the scapula; (3) had a diagnosis of long thoracic nerve or accessory nerve injury; or (4) had past or present musculoskeletal conditions affecting the cervical or thoracic spine, glenohumeral joint, or acromioclavicular joints. All recruited subjects signed consent forms approved by the institutional review board. The scapulometer in this study was modified from the Weon tool (Weon et al., 2011). The modified scapulometer was stationed at one side to measure the distance from the root of the spine (ROS) and the inferior angle (INF) of the scapula to the thoracic wall, respectively. For the measurement, right and left scapulometers were made for each side. This modified scapulometer had two parts: a digital caliper (HANLIN 1052, Taiwan) and a ruler body. The digital caliper, designed for up to 150 mm linear measurements with minimum measurement error of 1 mm, was perpendicularly attached at the distal end of a 15-cm ruler body. Additionally, an inclinometer was attached to the ruler body to maintain the orientation of the scapulometer (Fig. 1). Before conducting the test, two anatomic landmarks, ROS and INF, were identified and marked. Then two parallel landmarks on the same
Fig. 1. Modified scapulometer, with ruler A and digital caliper C designed to measure prominence of the scapular medial border and inferior angle. An inclinometer B was attached to the body to maintain scapulometer orientation.
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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level of the ROS and INF, approximately 1 cm medial to the scapular medial border, were marked. To measure scapular dyskinesis (prominence of the scapular medial border and inferior angle), one rater stood behind the subject and placed the ruler body of the modified scapulometer on the anatomic landmark and the digital caliper on the parallel landmark (Fig. 2). Holding the modified scapulometer in place with one hand on the ruler body, the first rater slid the digital caliper anteriorly toward the parallel landmark until firm contact. Posterior displacement of the scapula was recorded by the second rater based on the digital caliper. Stabilizing the modified scapulometer on only one side of the scapular medial border prevents the tool from tipping sideways. This modification of the tool further prevents muscle asymmetry from influencing measurement results. During the measurement, an inclinometer attached to the ruler body was monitored to maintain the orientation of the scapulometer. All measurements were performed with the subject in a relaxed sitting position with arms by side. The subjects were not instructed to alter their
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posture alignment. During the measurements, both raters were blinded to the results. Both raters were physical therapists with a minimum of 3 years of clinical experience. The intra-rater reliability of the measurement was assessed for one of the raters. Measurements were repeated 3 times on both sides in randomized order. The scapular dyskinesis measurement was taken as described in the previous section. Two raters were involved in assessing interrater reliability. One rater assessed the scapular dyskinesis as outlined in the methods section. The second rater then repeated the measure on the same scapula within 20 min. Both raters were blinded to the results of the measurements. Before conducting a measurement, a pressure meter (Force Ten FDX, Wagner, USA) placed on the parallel landmarks was used as a practice guide to calibrate the pressure applied to the participant between the 2 raters. The FASTRAK Polhemus 3-D (Polhemus Inc., Colchester, VT, USA) motion tracking system with Motion Monitor software was used to capture scapular kinematics as a standard measurement for validation. It has been reported by the manufacturer that the system has an accuracy of 0.8 mm and 0.15 . Excellent reliability (ICC 0.62e0.81) was reported, and validation of this method was established with correlations of the movement of pins in the scapula (Jordan et al., 2000; Karduna et al., 2001). The device has been used in many validity studies (Ha et al., 2013; Ribeiro et al., 2011). Sensors were attached to the sternum, flat surface of the acromion, and distal humerus, and local coordinate systems were marked with a stylus by an experienced physical therapist. Raw kinematic data were lowpass filtered at a 6-Hz cutoff frequency and converted into anatomically defined rotations. In general, the ISB guidelines were followed for constructing a shoulder joint coordinate system (Wu et al., 2005). The scapular orientation relative to the thorax was described using a Euler angle sequence of rotation about Zs (internal/external), rotation about Y's (downward/upward rotation), and rotation about X00 s (posterior/anterior tipping) (Fig. 3). The therapist guided the participant's scapula from resting to neutral position (disappearance of prominence) (Kibler et al., 2002). The differences in scapular position between dyskinesis (resting position) and neutral position were calculated, including tilt, internal/external rotation, and upward rotation of the scapula. Intraclass correlation coefficients (ICC (3.1)) were calculated based on a repeated measure analysis of variance to determine inter-rater reliability. The ICC (3.3) was calculated for intra-rater reliability. An ICC of greater than 0.75 indicates good reproducibility; one of less than 0.75, poor reproducibility (Portney and Watkins, 2000). Additionally, the standard error of measurement (SEM) was used to determine the measurement error. Pearson correlation between ROS and internal/external rotation and between INF and anterior/posterior tilt were calculated to represent convergent validity. Pearson correlations between ROS/ INF and upward rotation of the scapula represented divergent validity. 3. Results
Fig. 2. Landmarks and scapulometer measurement, a: rear view; b: superior view. The ruler was placed on the anatomic landmark while the digital caliper was placed on the parallel landmark. Posterior displacement of the scapula was measured by sliding the digital caliper toward the thorax until firm contact. A: Root of spine of scapular landmark. B: Parallel landmark at the same level of root of spine of scapula 1 cm medially to the scapular medial border.
The average ROS and INF displacements were 13.7 ± 5.0 mm and 12.5 ± 6.3 mm, respectively. The results of intra-rater and interrater reliability were ICC ¼ 0.88e0.99 and 0.95e0.99 (SEM ¼ 0.7e0.8 mm), respectively (Table 1). The convergent validity correlations were 0.35 (p ¼ 0.05) and 0.19 (p ¼ 0.86) for ROS/ internal rotation and INF/anterior tilt (Fig. 4), respectively, while the divergent validity correlations were 0.07 (p ¼ 0.661) and 0.09 (p ¼ 0.629) for ROS/upward rotation and INF/upward rotation, respectively (Table 2).
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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Fig. 3. Scapular orientation relative to the proposed scapular dyskinesis, prominence of medial border or inferior angle. RS: root of spine of scapula; IA: inferior angle of scapula.
and a standard error of measurement of 1.7 mm. Using a scapular medial border posterior displacement measurement device, Hong et al. (2011). found ICC values close to or above 0.90, with a standard error of measurement of 1.5e1.6 mm. Similarly, a scapulometer proposed by Weon et al. (2011). and Oliveira et al. (2015). presented values of 0.89e0.97 and 1 mm for reliability and standard error, respectively. However, these studies did not distinguish different types of dyskinesis, focusing only on the medial border, nor did they count mass asymmetry on both sides. Measuring the prominence of the scapular medial border and inferior angle specific to dyskinesis types, the modified scapulometer in the current study achieved excellent ROS and INF displacement reliability. The validity outcomes for objective measurement tools from previous studies are unknown or uncertain (Odom et al., 2001; Oliveira et al., 2015; Plafcan et al., 1997; Shadmehr et al., 2010; Weon et al., 2011). While some studies did not test the validity (Odom et al., 2001; Plafcan et al., 1997), others (Oliveira et al., 2015; Shadmehr et al., 2010; Weon et al., 2011) did not distinguish different type of dyskinesis. In the present study, in addition to distinguishing different types of dyskinesis, we used a 3-D motion capture system as a standard device to validate the measurement of the modified scapulometer. In theory, scapular dyskinesis with excessive scapular internal rotation (medial border prominence)
4. Discussion The present study aimed to assess a newly-developed instrument for measuring the posterior displacement of the scapular medial border and inferior angle with reference to the posterior thoracic cage unilaterally. The intra-rater and inter-rater reliability and the convergent and divergent validity of the measure were evaluated. Our results showed that the modified scapulometer had excellent reliability and good convergent/divergent validity, with fair correlations for ROS/internal rotation and INF/ anterior tilt. This supports our proposed kinematics between scapular internal rotation and medial border prominence, as well as that between scapular anterior tilt and inferior angle prominence (Fig. 3). Regarding reliability, the modified scapulometer had excellent intra-rater and inter-rater ICCs, with values above 0.88 and a standard error of 0.7e0.8 mm. These results are indicative of sufficiently good reliability for clinical use. Previous studies (Hong et al., 2011; Oliveira et al., 2015; Struyf et al., 2009; Weon et al., 2011) that examined and quantified the displacement of the scapula also showed good to excellent reliability values. Measuring the distance between the posterior border of the acromion and the thoracic wall with the modified lateral scapular slide test, Strufy et al (Struyf et al., 2009). found ICC values of 0.72
Table 1 Intra-rater and inter-rater reliability of scapular posterior displacement measurement. Raters Rater 1 Rater 2 Inter-rater ICC (3,3) a b c
Landmarks b
ROS (mm) INFc (mm) ROS (mm) INF (mm) ROS INF
Trial 1 13.8 12.5 13.4 12.6
± ± ± ±
Trial 2 5.2 6.4 5.1 6.4
13.7 12.5 13.3 12.6
± ± ± ±
Trial 3 4.9 6.2 5.3 6.3
13.8 12.5 13.5 12.5
± ± ± ±
Intra-rater ICC (3,1)a
Mean 4.9 6.3 5.3 6.3
13.8 12.5 13.4 12.6
± ± ± ±
5.0 6.3 5.1 6.3
0.97e0.98 0.97e0.99 0.88e0.97 0.97e0.98 0.95 0.99
ICC Intra-class correlation. ROS: Root of spine of scapula posterior displacement. INF: Scapular inferior angle posterior displacement.
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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Fig. 4. Correlation between scapulometer measurement and scapula kinematics. A. Correlation of scapula internal rotation and ROS (r ¼ 0.35). B. Correlation of scapula anterior tilt and INF. ROS: root of spine; INF: inferior angle of scapula.
and anterior tipping (inferior angle prominence) are related to posterior displacement of the root of the spine and the inferior angle of the scapula, respectively (Kibler et al., 2013). Our convergent and divergent correlation results support this proposition; we found fair correlations between ROS/internal rotation, and no correlations between ROS/upward rotation and INF/upward rotation.
Thus, our measurement provides quantification of impairment of the internal rotation of the scapula by the root of spine prominence in subjects with dyskinesis. The amount of impairment is important to consider during rehabilitation for symptomatic dyskinesis subjects, which is highly related to decreased subacrominal space
Table 2 Validity between scapulometer measurement and 3-D motion measurements. Items Convergent validity ROSa * int/extb INFc * ant/postd Divergent validity ROSa * ure INFc * ur a b c d e
Scapulometer measurement
Three-dimensional measurement
Correlation
13.4 ± 5.1 mm 12.6 ± 6.3 mm
7.5 ± 3.1 1.9 ± 1.4
0.35 (p ¼ 0.05) 0.18 (p ¼ 0.86)
13.4 ± 5.1 mm 12.6 ± 6.3 mm
2.4 ± 2.1 2.4 ± 2.1
0.07 (p ¼ 0.661) 0.09 (p ¼ 0.629)
ROS: Root of spine of scapula posterior displacement. int/ext: scapular internal/external rotation. INF: Scapular inferior angle posterior displacement. ant/post: scapular anterior/posterior tilt. ur: scapular upward rotation.
Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004
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impingement syndrome (Lukasiewicz et al., 1999; McClure et al., 2006; Solem-Bertoft et al., 1993). The measurement validity of the modified scapulometer can be influenced by several factors. First, the neutral positions for dyskinesis measurement are not standardized. The “neutral” position was determined subjectively by a therapist, who actively guided the scapula back to the rib cage to minimize any bony prominence of the scapula. However, the “neutral” position of the scapula may be influenced by the thickness of the subject's subcutaneous tissue or contraction of scapular muscles. Thus, subjective judgment may under-estimate the degree of scapular dyskinesis. Second, subjects who have excessive scapular anterior tilt may be unable to actively place their scapula in the “neutral” position due to tightness of the anterior shoulder tissue (i.e., pectoralis minor muscle), which is a common cause of scapular dyskinesis (Ludewig and Reynolds, 2009). Participants with anterior shoulder tightness, who being unable to maintain the scapula in the neutral position, were not included in the study. Thus, the validity may have been under or over-estimated. Third, a three-dimensional electromagnetic device was used as a comparison standard in this study. The correlations between scapular internal rotation/anterior tipping and ROS/INF were fair to poor. These modest results may be related to the standard chosen in the present study. The sensors for scapular motion capture were placed on the flat surface of the acromion. During motion, the sensor may be influenced by the movement of the skin beneath the sensor. Therefore, it may not be the most suitable device for validating the modified scapulometer. Although imaging such as x-ray or MRI may provide more direct access to the direction of scapular posterior prominence with reference to the posterior thoracic cage, no standard positions or views for scapular dyskinesis imaging have been established to date. In addition, imaging examination increases the risk of radiation exposure for participants. Given the above concerns, we chose the 3-D electromagnetic device as a substitute comparison standard. There are some limitations of this study that need to be considered. First, the results of this study are not generalizable to symptomatic participants with scapular dyskinesis. Second, measurement was applied to dyskinesis subjects with medial border and/or inferior angle prominence, the tool may not be applicable to those who have excessively abducted scapulae dyskinesis. Third, this tool is designed to measure two-dimensional scapular orientation in the resting position; therefore, it may not be applicable to dynamic or functional use. Future studies with symptomatic and various type of dyskinesis subjects should be conducted to investigate whether the amount of posterior displacement can be detected for classification of symptomatic dyskinesis. 5. Conclusion In clinical practice, it is important to consider that the current tool, which measures common prominence of the scapular medial border and inferior angle, could provide advantages by eliminating the need for expensive equipment, maintenance, and software for data analysis. The modified scapulometer is inexpensive and easily accessible. Having excellent reliability and fair validity to quantify prominence of the scapular medial border and inferior angle, this instrument is recommended for use in evaluation and in measurement of treatment outcomes for patients with symptomatic dyskinesis. Further research utilizing this instrument is recommended. Acknowledgments This study was supported by the Ministry of Science and Technology, 104-2314-B-002-026-MY3, Taiwan.
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Please cite this article in press as: Du, W.-Y., et al., Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study, Musculoskeletal Science and Practice (2017), http://dx.doi.org/10.1016/j.msksp.2017.08.004