Measuring 3D In-vivo Shoulder Kinematics using Biplanar Videoradiography
March 12th, 2021
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.
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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Overview
Biplane videoradiography provides a highly accurate method for quantifying shoulder kinematics. This protocol focuses on tracking the scapula, humerus, and ribs during planar humeral elevation.
Key Study Components
Area of Science
- Neuroscience
- Biomechanics
- Radiography
Background
- Participants in studies are exposed to radiation.
- High accuracy is crucial due to the small margin for error.
- Joint motion quantification is essential for advanced research questions.
- Proper positioning and safety measures are necessary for participant comfort and protection.
Purpose of Study
- To share a protocol for using biplane videoradiography.
- To enhance the accuracy of joint motion analysis.
- To facilitate research that requires precise kinematic data.
Methods Used
- Positioning the chair in the biplane imaging volume.
- Adjusting chair position based on participant's anthropometrics.
- Securing a lead-lined protective vest for safety.
- Collecting data on scapula, humerus, and rib movements.
Main Results
- Accurate tracking of shoulder kinematics was achieved.
- Protocol allows for detailed analysis of joint motion.
- Demonstrated the feasibility of using this technology in research.
- Highlighted the importance of participant safety during data collection.
Conclusions
- Biplane videoradiography is a valuable tool for kinematic analysis.
- Accuracy in data collection is critical for research integrity.
- Future studies can benefit from this protocol to explore complex questions.
Frequently Asked Questions
Executive Industry Relevance
Accurate quantification of joint kinematics is essential for understanding the biomechanical basis of musculoskeletal disorders and evaluating therapeutic interventions. Biplanar videoradiography provides high-precision 3D motion tracking, enabling mechanistic de-risking in preclinical target validation for shoulder-related pathologies. This capability supports predictive confidence in lead identification by linking functional outcomes to structural changes in disease models.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses by quantifying altered joint motion as a functional readout of target engagement.
- Operational Value: Provides reproducible, quantitative biomechanical data to clarify pathophysiological mechanisms in disease models.
- Predictive Value: Supports portfolio triage by correlating kinematic changes with target modulation efficacy.
Screening & Assay Development
- Scientific Value: Generates validated, standardized biomechanical endpoints for screening compounds that modify joint function.
- Operational Value: Ensures assay reproducibility through synchronized biplane imaging and motion-triggered acquisition protocols.
- Translational Value: Delivers quantitative, continuous kinematic outputs suitable for dose-response and time-course analyses.
Translational & Preclinical Research
- Scientific Value: Bridges discovery and preclinical stages by providing disease-relevant, 3D joint motion data from intact systems.
- Operational Value: Facilitates longitudinal tracking of joint kinematics to assess progression or recovery in preclinical models.
- Risk Mitigation: Reduces mechanistic ambiguity in target validation by directly measuring functional consequences of pathway modulation.
Pipeline & Workflow Integration
The method integrates into the discovery continuum from target validation through preclinical evaluation, where precise kinematic phenotyping informs go/no-go decisions.
- Discovery Biology: Supports hypothesis testing by quantifying joint motion as a functional biomarker of target activity in disease-relevant models.
- Screening: Enables assay readiness through standardized acquisition parameters and motion synchronization for reliable compound screening.
- Analytics: Delivers continuous kinematic readouts (e.g., elevation angles, rotation, subacromial distance) for quantitative comparison across experimental conditions.
- Translational Research: Connects to preclinical continuity by providing 3D motion data that aligns with functional outcomes in joint disease models.
- Enterprise Reuse: Establishes a reusable biomechanical phenotyping platform applicable across multiple joint targets and disease areas.
Operational & Enterprise Impact
- Scientific Value: Predictive confidence in target validation through direct measurement of functional joint mechanics.
- Operational Value: Standardization and reproducibility via synchronized biplane acquisition and motion-triggered imaging.
- Strategic Value: Improved go/no-go decisions by reducing biological uncertainty in mechanistic studies.
- Portfolio Impact: Risk-adjusted prioritization based on quantitative, mechanism-linked functional outcomes.
Implementation Considerations
- Expertise in biomechanics, radiography safety, and 3D motion analysis is required.
- Biplanar videoradiography system, CT scanner, and 3D modeling software are essential infrastructure components.
- Standardized participant positioning and motion scripting are necessary for cross-study consistency.
- Adaptation to different joint models requires recalibration of imaging planes and tracking algorithms.
- Radiation safety protocols must be strictly followed due to ionizing exposure during acquisition.
