Research reported in this publication was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases under award number R01AR051912. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health (NIH).

Prior to data collection, the participant provided written informed consent. The investigation was approved by Henry Ford Health System&#39;s Institutional Review Board.
Protocols for acquiring, processing, and analyzing biplane radiographic motion data are highly dependent upon the imaging systems, data processing software, and outcome measures of interest. The following protocol was specifically designed to track the scapula, humerus, and the third and the fourth ribs during scapular-plane o...

The authors have no conflicts of interest.

The technique described here overcomes several disadvantages associated with conventional techniques for assessing shoulder motion (i.e., cadaveric simulations, 2D imaging, static 3D imaging, video-based motion capture systems, wearable sensors, etc.) by providing accurate measures of 3D joint motion during dynamic activities. The accuracy of the protocol described herein was established for the glenohumeral joint against the gold standard of radiostereometric analysis (RSA) to be &#177;0.5&#176; and &#177;0.4 mm<sup cla...

The shoulder is one of the human body&#39;s most complex joint systems, with motion occurring through the coordinated actions of four individual joints, multiple ligaments, and approximately 20 muscles. The shoulder also has the greatest range of motion of the body&#39;s major joints and is often described as a compromise between mobility and stability. Unfortunately, shoulder pathologies are common, resulting in substantial pain, disability, and decreased quality of life. For example, rotator cuff tears affect about 40% of the population over age 601,2,3, with approximately 250,000 rotator cuff repairs performed annually4, and an estimated economic burden of $3-5 billion per year in the United States5. Additionally, shoulder dislocations are common and are often associated with chronic dysfunction6. Lastly, glenohumeral joint osteoarthritis (OA) is another significant clinical problem involving the shoulder, with population studies indicating that roughly 15%-20% of adults over the age of 65 have radiographic evidence of glenohumeral OA7,8. These conditions are painful, impair activity levels, and decrease quality of life.
Although the pathogeneses of these conditions are not fully understood, it is generally accepted that altered shoulder motion is associated with many shoulder pathologies9,10,11. Specifically, abnormal joint motion may contribute to the pathology9,12, or that the pathology may lead to abnormal joint motion13,14. Relationships between joint motion and pathology are likely complex, and subtle alterations in joint motion may be important in the shoulder. For example, although angular motion is the predominant motion occurring at the glenohumeral joint, joint translations also occur during shoulder motion. Under normal conditions these translations likely do not exceed several millimeters15,16,17,18,19, and therefore may be below the level of in-vivo accuracy for some measurement techniques. While it may be tempting to assume that small deviations in joint motion may have little clinical impact, it is important to also recognize that the cumulative effect of subtle deviations over years of shoulder activity may exceed the individual&#39;s threshold for tissue healing and repair. Furthermore, in-vivo forces at the glenohumeral joint are not inconsequential. Using custom instrumented glenohumeral joint implants, previous studies have shown that raising a 2 kg weight to head height with an outstretched arm can result in glenohumeral joint forces that can range from 70% to 238% of body weight20,21,22. Consequently, the combination of subtle changes in joint motion and high forces concentrated over the glenoid&#39;s small load-bearing surface area may contribute to the development of degenerative shoulder pathologies.
Historically, the measurement of shoulder motion has been accomplished through a variety of experimental approaches. These approaches have included the use of complex cadaveric testing systems designed to simulate shoulder motion23,24,25,26,27, video-based motion capture systems with surface markers28,29,31, surface-mounted electromagnetic sensors32,33,34,35, bone pins with reflective markers or other sensors attached36,37,38, static two-dimensional medical imaging (i.e., fluoroscopy39,40,41 and radiographs17,42,43,44,45), static three-dimensional (3D) medical imaging using MRI46,47, computed tomography48, and dynamic, 3D single plane fluoroscopic imaging49,50,51. More recently, wearable sensors (e.g., inertial measurement units) have gained popularity for measuring shoulder motion outside the laboratory setting and in free-living conditions52,53,54,55,56,57.
In recent years, there has been a proliferation of biplane radiographic or fluoroscopic systems designed to accurately measure dynamic, 3D in-vivo motions of the shoulder58,59,60,61,62. The purpose of this article is to describe the authors&#39; approach for measuring shoulder motion using a custom biplanar videoradiography system. The specific objectives of this article are to describe the protocols to acquire biplanar videoradiographic images of the shoulder complex, acquire CT scans, develop 3D bone models, locate anatomical landmarks, track the position and orientation of the humerus, scapula, and torso from the biplanar radiographic images, and calculate kinematic outcome measures.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Calibration cube</td>
			<td>Built in-house</td>
			<td>N/A</td>
			<td>10 cm Lucite box with a tantalum bead in each corner and four additional beads midway along the box&#8217;s vertical edges (12 beads total). The positions of each bead are precisely known relative to a corner of the box that serves as the origin of the laboratory coordinate system.</td>
		</tr>
		<tr>
			<td>Distortion correction grid</td>
			<td>Built in-house</td>
			<td>N/A</td>
			<td>Lucite sheet that covers the entire face of the 16 inch image intensifier and contains an orthogonal array of tantalum beads spaced at 1 cm.</td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>National Institutes of Health</td>
			<td>N/A</td>
			<td>Image processing software used to prepare TIFF stack of bone volumes.</td>
		</tr>
		<tr>
			<td>Markerless Tracking Workbench</td>
			<td>Custom, in house software</td>
			<td>N/A</td>
			<td>A workbench of custom software used to digitize anatomical landmarks on 3D bone models, constructs anatomical coordinate systems, uses intensity-based image registration to perform markerless tracking, and calculates and visualize kinematic outcomes measures.</td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>Mathworks, Inc</td>
			<td>N/A</td>
			<td>Computer programming software. For used to perform data processing and analysis.</td>
		</tr>
		<tr>
			<td>Mimics (version 20)</td>
			<td>Materialise, Inc</td>
			<td>N/A</td>
			<td>Image processing software used to segment humerus, scapula, and ribs from CT scan.</td>
		</tr>
		<tr>
			<td>Open Inventor</td>
			<td>Thermo Fisher Scientific</td>
			<td>N/A</td>
			<td>3D graphics program used to visualize bones</td>
		</tr>
		<tr>
			<td>Phantom Camera Control (PCC) software (version 3.4)</td>
			<td></td>
			<td>N/A</td>
			<td>Software for specifying camera parameters, and acquiring and saving radiographic images</td>
		</tr>
		<tr>
			<td>Pulse generator (Model 9514)</td>
			<td>Quantum Composers, Inc.</td>
			<td>N/A</td>
			<td>Syncs the x-ray and camera systems and specifies the exposure time</td>
		</tr>
		<tr>
			<td>Two 100 kW pulsed x-ray generators (Model CPX 3100CV)</td>
			<td>EMD Technologies</td>
			<td>N/A</td>
			<td>Generates the x-rays used to produce radiographic images</td>
		</tr>
		<tr>
			<td>Two 40 cm image intensifiers (Model P9447H110)</td>
			<td>North American Imaging</td>
			<td>N/A</td>
			<td>Converts x-rays into photons to produce visible image</td>
		</tr>
		<tr>
			<td>Two Phantom VEO 340 cameras</td>
			<td>Vision Research</td>
			<td>N/A</td>
			<td>High speed cameras record the visible image created by the x-ray system</td>
		</tr>
	</tbody>
</table>

measuring 3d in-vivo shoulder kinematics using biplanar videoradiography

The shoulder is one of the human body's most complex joint systems, with motion occurring through the coordinated actions of four individual joints, multiple ligaments, and approximately 20 muscles. Unfortunately, shoulder pathologies (e.g., rotator cuff tears, joint dislocations, arthritis) are common, resulting in substantial pain, disability, and decreased quality of life. The specific etiology for many of these pathologic conditions is not fully understood, but it is generally accepted that shoulder pathology is often associated with altered joint motion. Unfortunately, measuring shoulder motion with the necessary level of accuracy to investigate motion-based hypotheses is not trivial. However, radiographic-based motion measurement techniques have provided the advancement necessary to investigate motion-based hypotheses and provide a mechanistic understanding of shoulder function. Thus, the purpose of this article is to describe the approaches for measuring shoulder motion using a custom biplanar videoradiography system. The specific objectives of this article are to describe the protocols to acquire biplanar videoradiographic images of the shoulder complex, acquire CT scans, develop 3D bone models, locate anatomical landmarks, track the position and orientation of the humerus, scapula, and torso from the biplanar radiographic images, and calculate the kinematic outcome measures. In addition, the article will describe special considerations unique to the shoulder when measuring joint kinematics using this approach.

A 52-year-old asymptomatic female (BMI = 23.6 kg/m2) was recruited as part of a previous investigation and underwent motion testing (coronal plane abduction) on her dominant (right) shoulder65. Prior to data collection, the participant provided written informed consent. The investigation was approved by Henry Ford Health System&#39;s Institutional Review Board. Data collection was performed using the protocol previously described (Figure 3).
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Measuring 3D In-vivo Shoulder Kinematics using Biplanar Videoradiography

Biplane videoradiography can quantify shoulder kinematics with a high degree of accuracy. The protocol described herein was specifically designed to track the scapula, humerus, and the ribs during planar humeral elevation, and outlines the procedures for data collection, processing, and analysis. Unique considerations for data collection are also described.

The shoulder is one of the human body's most complex joint systems, with motion occurring through the coordinated actions of four individual joints, ...

We believe it's important to share our protocol and what we've learned using this technology in our research, because the participants in these studies are exposed to radiation and therefore, the margin for error is very small. The main advantage of this technique is the accuracy with which the joint motion can be quantified, which allows researchers to pursue questions that otherwise, would not be possible. Before beginning an analysis, position the chair in the biplane imaging volume so that the shoulder to be tested is centered at approximately the point where the biplane x-ray beams intersect.Ask the participant to be seated in a comfortable, upright posture with arms at their sides. Adjust the preliminary chair position based on the participant's anthropometrics, the motion to be tested, and the bones to be tracked. And secure a lead-lined protective vest across the participant's torso to cover the abdomen and contralateral shoulder and chest.Turn on the light within the x-ray source of the system and raise the system until the shadow cast onto the image intensifier is at the level of the participant's axilla. Gently move the participant on the chair within the biplane image volume while watching the shadow on the intensifier. Once the participant's position is set for both systems keeping the light source on, ask the participant to perform the motion that will be tested during the procedure.The participant's shoulder should remain within the radiographic field. To verify the participant's position in the control room set the x-ray control panel to low fluoroscopy mode and the pulse generator to a 0.25-second acquisition. Have an assistant explain the process to the participant including warning the participant about any sounds they might hear during the imaging.Before starting the imaging, the assistant should put on a lead-lined protective vest and move away from the x-ray sources while maintaining a clear line of sight and communication with the participant. To acquire an image, start the cameras and prime the X-ray control panel. When the system is ready, instruct the assistant to begin acquiring the radiographic images using a handheld remote trigger.Inspect the images after they have been acquired to determine whether the participant's position was satisfactory for visualizing all of the necessary bones. For static image acquisition set the optimized radio technique on the x-ray control panel as determined from the preliminary imaging and have the assistant ask the participant to sit upright with their arms resting at their sides. After acquiring an image in this position, inspect the image for quality, bone of interest visibility, and technical condition.When an optimal image has been acquired, save the trial from each camera. For dynamic image acquisition, using the same parameters, but with the pulse generator set to a two-second exposure, have the assistant practice the motion to be performed with a participant, using a verbal cue, paced so that the motion is performed in two seconds. When the participant is ready, start the cameras and prime the control panel as demonstrated and notify the assistant that the system is ready.Have the assistant ask whether the participant is ready before giving the verbal cue, Ready and go, so that the participant performs the motion as the assistant triggers the x-ray system to acquire a dynamic image. When good quality images for all the motion trials have been acquired, save the trials from each camera. In this representative analysis a 52-year-old asymptomatic female underwent motion testing on her dominant shoulder as demonstrated.CT scan images of the shoulder joint were also obtained in the coronal, sagittal and transverse planes to include the entire scapula, humorous and ribcage. These radiographic images illustrate the complexity of acquiring biplane radiographs of the shoulder at lower angles of humeral elevation, the lateral acromion and distal clavicle appear overexposed in the green view, but are well visualized in the red view, due to the lower volume of soft tissue within the area. However, as the arm elevates, the bulk of the deltoid becomes projected over the area resulting in a better radiographic exposure.As observed in this kinematics analysis, the glenohumeral motion consisted of elevation and a slight external rotation and was generally in-plane posterior to the scapula. The scapula thoracic motion consisted of an upward rotation with a posterior tilt and a slight internal-external rotation. During the motion trial, the minimum subacromial distance decreased until approximately 90 degrees humoral thoracic elevation, at which point the distance began to increase.The average subacromial distance followed a similar trajectory. The minimum subacromial distance followed a complimentary trajectory to the surface area metric, such that the minimum distance tended to be smaller when the surface area was larger. Having the participant practice the motion is critical to ensuring that they understand the procedure and that they can perform the desired motion with the correct pace and timing.

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2.8K Views.  Henry Ford Health System. We believe it's important to share our protocol and what we've learned using this technology in our research, because the participants in these studies are exposed to radiation and therefore, the margin for error is very small. The main advantage of this technique is the accuracy with which the joint motion can be quantified, which allows researchers to pursue questions that otherwise, would not be possible. Before beginning an analysis, position the chair in the biplane imaging volume so tha...