Grimes et al. (2022)

The Posterior Standing Overhead Arm Reach test as a measure of functional hip extension range of motion

The SOAR test measures closed chain standing hip extension

As this test uses a goniometer and a tape indication on the floor, it is a relatively easy way to measure hip ROM

The first step in reliability assessment was taken, indicating good intrarater outcomes which should be further assessed

Introduction

In this study, a novel test to examine functional hip extension range of motion was examined for its reliability and validity. The Posterior Standing Overhead Arm Reach (SOAR) test was developed as a measure of closed chain hip extension. With this test, hip extension can be objectivated in a more functional manner than the commonly used prone hip extension measure. As this test was only recently developed, the authors first examined it in a voluntary sample.

 

Methods

Asymptomatic volunteers between the ages of 18-30 years were recruited. They had no complaints of low back or lower extremity pain within the last 3 months, surgery, fractures, or neurological pathology and had a BMI below 30.

Hip extension was measured with a goniometer by two blinded examiners in a standardized test position. First, a sticker was placed on the floor just in front of the first foot when the patient was in a tandem stance. Then the subject was instructed to stand with the feet shoulder-width apart and the heel of the non-test leg on the sticker. The participant raised both arms overhead and lifted the front forefoot of the ground so that only the heel was in contact with the floor and the body weight was placed upon the test leg. It was then asked to push the hips forward and reach the arms posteriorly as far as they could.

functional hip extension range of motion
From: Grimes et al., Musculoskelet Sci Pract (2022)

 

The placement of the goniometer was standardized: the fulcrum was placed over the greater trochanter, the proximal arm was placed on a line perpendicular to the line connecting the ASIS and PSIS, while the distal arm was placed in line with the midline of the femur.

functional hip extension range of motion
From: Grimes et al., Musculoskelet Sci Pract (2022)

 

Three attempts were made to reach maximal hip extension and each leg was tested thrice, alternating between both legs. These measurements were then compared to determine the interrater and intrarater reliability of the SOAR test. The validity of the test was determined by comparing the goniometric outcomes to the results of a 3D motion capture.

Interrater and intrarater reliability was assessed using the intraclass correlation coefficient (ICC) where values < 0.4 were interpreted as poor, 0.40-0.59 as fair, 0.60-0.74 as good, and ⋝ 0.75 as excellent reliability. For validity, Pearson correlation coefficients were interpreted.

 

Results

Twenty-five subjects with a mean age of 24 years participated in the study. In total, 50 hips were examined. The intrarater reliability for both examiners was 0.77 (0.64-0.86) and 0.80 (0.68-0.88), showing excellent reliability. The interrater reliability was 0.65 (0.36-0.80), which indicated good reliability between two independent examiners.

The standard error of the measure was 2.5° and 3° for each of the assessors and the minimal detectable change was 3.5° and 4.2°. When the results were compared against the 3D motion capture to assess validity, it became clear that the measurements were low to moderately associated.

 

Questions and thoughts

Daily activities mostly require closed-chain hip movements and this test was an excellent measure to gain more insights here. In 2010, van Trijffel and colleagues did a systematic review investigating measures of lower extremity passive motion and found inadequate reliability for measuring hip extension. Generally, these measurements are taught in a non-weight-bearing position with the patient prone, but this neglects the influence of a standing weight-bearing position on the measurement outcome. In some cases, this prone measurement is difficult to obtain, especially when the examiner’s hand is not able to grasp the leg of the subject. This SOAR test may be a good option to counter these limitations.

As this SOAR test only needs a tape measurement and a goniometer, it is widely applicable in clinical practice and does not require expensive equipment. By using the tape measure indication, the test can be standardized so that over time, measurements are only slightly influenced by positional changes. Together with the goniometric measurement, the ASIS and PSIS were palpated and the line in between indicated where to place the upper arm of the goniometer perpendicular to it. This way, the test accounted for the influence of pelvic tilt.

The 3D motion capture measurements yielded a greater functional hip extension range of motion about 70% of the time. The authors state that it may be possible that a learning curve caused this difference. Also, the movement of the trunk may have caused the skin under the markers to move, thereby possibly attenuating the difference. So is this really a valid?

The 3D motion capture measurements yielded a greater functional hip extension range of motion in about 70% of the time. The authors state that it may be possible that a learning curve caused this difference. Also, the movement of the trunk may have caused the skin under the markers to move, thereby possibly attenuating the difference. So is this really a valid measurement? Based upon these results possibly not. However, taking into account the authors’ comments, with medical imaging in future studies, this conclusion may be changed.

 

Talk nerdy to me

The lower limits of the 95% confidence intervals indicate that the intrarater reliability was good. The mean ICC and upper limits display excellent intrarater reliability. For the interrater reliability, the mean ICC was good, but the lower limit of the confidence interval was only poor, while the upper limit shows excellent reliability. It thus seems that much greater accuracy is seen when the measurement is performed by only 1 examiner (as the confidence interval of intrarater reliability is more narrow) . The comparison between different examiners yields a much wider confidence interval and therefore, this direct comparison may have limitations.

Good aspects we note are the randomized order of measurements, and the independent assessment by both examiners who were also blinded to the outcome (as an additional investigator read and recorded the goniometer results).

A relevant side note I have with these results is that the minimal important difference appears to be small. However, you should take into account that hip extension ROM is a small movement, with approximately 30° of total ROM. So a minimally important difference of 3-4° seems small but relative to the total hip extension ROM it means more than 10%. Therefore, you should already obtain a 10% change in this measure to be able to interpret the outcome.

 

Take home messages

Rather than comparing these results between independent examiners, it seems that the SOAR test is able to produce consistent results when used by one examiner. Therefore it seems that this test may serve as a relevant longitudinal measure of closed-chain hip extension, measuring changes over time. A minimally important difference of 3-4° should be noted and thus changes below do not reflect true changes in hip extension ROM. Future studies should investigate if this test really is a valid measure of functional hip extension range of motion as due to several issues, the validity measured in this study may be compromised.

 

Reference

Grimes J, Wager J, Goldfarb J, Bauer P, Ferraro P, Loken M, Lynch R, Stegmann T. A preliminary study of the reliability and validity of the Posterior Standing Overhead Arm Reach (SOAR) test as a measure of functional hip extension motion. Musculoskelet Sci Pract. 2022 May 25;61:102589. doi: 10.1016/j.msksp.2022.102589. Epub ahead of print. PMID: 35661575. 

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