Reliability and accuracy of distance measurements between shoulder bony landmarks evaluated by ultrasound in asymptomatic subjects

Duerr, Marion
Hing, Wayne
White, Steve
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Master of Philosophy
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Auckland University of Technology
Background: Assessment of the glenohumeral (GH) joint is an integral part of clinical physiotherapy practice. Changes of normal GH joint kinematics occur frequently in individuals with GH joint disorders. Faulty GH kinematics can involve abnormal resting position of the humeral head and abnormal translation of the humeral head on the glenoid in the superior-inferior and/or anterior-posterior direction. Ultrasound imaging (USI) is a versatile imaging technique, which is becoming increasingly available for clinical use in physiotherapy. USI allows for assessment of distances between the humeral head and scapular landmarks, such as the acromion and the glenoid in various shoulder positions. Currently, only a small number of studies have applied USI for the assessment of distances between the humeral head and scapular landmarks, and humeral head translation occurring GH movement. Well-described methodologies are scarce and there is insufficient evidence for the reliability of USI assessing distances and humeral head translation. Objective: The main objective was to determine the intra-rater reliability and accuracy of USI distance measurements between the humeral head and scapular landmarks, i.e. the acromion and the glenoid in a neutral shoulder position and in passive and active GH joint abduction. Further objectives were to determine normal values of these distances in the three shoulder positions in healthy individuals, and to assess the distance changes that occur with GH joint movement. Another objective was to compare measurements between genders and between the dominant and non-dominant side, as well as to examine the relationships between participants’ characteristics and distance values. Study Design: Intra-rater (single assessor) reliability study using same individuals repeated measures test-retest design. Methods and Measurement: The USI methodology was developed in a pilot study. In the main study, 40 healthy subjects without a history of shoulder pain or injury were recruited. In the superior-inferior direction, the acromiohumeral distance (AHD) and the distance between the acromion and the greater tuberosity (AGTD) were measured using a superior USI view. In the anterior-posterior direction, the humeroglenoid distance (HGD) was measured using a posterior transverse USI view. AHD, AGTD and HGD were determined in a neutral shoulder position. In addition, AHD and HGD were measured at 60º passive and active GH joint abduction. Two consecutive measurements of each distance were taken by one examiner in two sessions, which were five to seven days apart. Statistical analysis included the intraclass correlation coefficient (ICC) for single measures for assessing the within- and between-sessions intra-rater reliability, and a Bland-Altman analysis. Measurement error and accuracy were calculated using the standard error of the measurement (SEM) and the smallest real difference (SRD). Independent samples t-tests were used to compare differences between mean values of the AHD and HGD in the three shoulder positions; between men and women; and between the dominant and non-dominant side. Correlations between distance measurements and participants’ characteristics, such as body weight, height, age and overhead sports activities were analysed using regression analysis. Results: ICC values were high to excellent for all distance measurements. ICC values were lower between sessions than within sessions, particularly for the HGD measurement. Measurement errors were small for all measurements, including SRD values of 0.12 cm for the AGTD, 0.09 cm for the AHD and 0.05 cm for the HGD in the neutral shoulder position, and 0.05 cm for the AHD and 0.14 cm for the HGD in abducted shoulder positions. In session 1, mean values (± SD) of the AGTD and AHD were 1.45 (± 0.28) cm and 1.07 (± 0.18) cm respectively in the neutral shoulder position. In 60º passive and active abduction, mean values of AHD were 0.81 (± 0.21) cm and 0.78 (± 0.19) cm respectively. In neutral, 60º passive and active abduction, mean values of HGD were 1.34 (± 0.38) cm, 1.20 (± 0.41) cm and 1.08 (± 0.40) cm respectively. Distances in Session 2 were comparable. AHD and HGD mean values decreased significantly when the arm was moved from the neutral position into abduction, while distances did not change significantly between passive and active abduction. Distances were found to be smaller in women compared to men, but no difference was detected between the dominant and non-dominant side. Body weight was significantly correlated with AHD and HGD. Moreover, HGD measurements were correlated with height and age. Participation in overhead sports activities had no effect on measured distances. Conclusion: The results show that the USI method that was developed and applied in this research is highly reliable for the repeated application by one examiner. Furthermore, the low measurement errors suggest that this USI method is accurate enough to detect a small difference between two measurements, which may well be clinically important. Of the two measurements used in the superior USI view, the AHD showed higher quality, as it proved applicable in both the neutral and the abducted position, whereas the AGTD was not useable in shoulder abduction. The significant reduction of the AHD and HGD with 60º abduction indicates that the humeral head translates in an anterior-superior direction with abduction in healthy shoulders. This research has developed a reliable and accurate USI method, which uses reproducible anatomical landmarks visible on the USI image, functionally relevant shoulder positions for acromio-humeral and gleno-humeral distance measurements in both the superior-inferior and anterior-posterior direction, and is achievable for inexperienced examiners. Future studies are warranted to establish the reliability of the USI method between several examiners and in other shoulder populations, and to further examine the role of these measurements in shoulder disorders.
Ultrasound imaging , Reliability , Accuracy , Humeral head translation , Distance measurement , Acromiohumeral distance
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