measuring-3d-vivo-shoulder-kinematics-using-biplanar

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, ...

The purpose of this study was to determine the accuracy of a radiographic model-based tracking technique that measures the three-dimensional in vivo motion of the tibio-femoral joint during running. Tantalum beads were implanted into the femur and tibia of three subjects and computed tomography (CT) scans were acquired after bead implantation. The subjects ran 2.5m/s on a treadmill positioned within a biplane radiographic system while images were acquired at 250 frames per second. Three-dimensional implanted bead locations were determined and used as a "gold standard" to measure the accuracy of the model-based tracking. The model-based tracking technique optimized the correlation between the radiographs acquired via the biplane X-ray system and digitally reconstructed radiographs created from the volume-rendered CT model. Accuracy was defined in terms of measurement system bias, precision and root-mean-squared (rms) error. Results were reported in terms of individual bone tracking and in terms of clinically relevant tibio-femoral joint translations and rotations (joint kinematics). Accuracy for joint kinematics was as follows: model-based tracking measured static joint orientation with a precision of 0.2 degrees or better, and static joint position with a precision of 0.2mm or better. Model-based tracking precision for dynamic joint rotation was 0.9+/-0.3 degrees , 0.6+/-0.3 degrees , and 0.3+/-0.1 degrees for flexion-extension, external-internal rotation, and ab-adduction, respectively. Model-based tracking precision when measuring dynamic joint translation was 0.3+/-0.1mm, 0.4+/-0.2mm, and 0.7+/-0.2mm in the medial-lateral, proximal-distal, and anterior-posterior direction, respectively. The combination of high-speed biplane radiography and volumetric model-based tracking achieves excellent accuracy during in vivo, dynamic knee motion without the necessity for invasive bead implantation.

Validation of three-dimensional model-based tibio-femoral tracking during running.

Joint morphology has a significant influence on joint motion and may contribute to the development of rotator cuff pathology, but the relationships between glenohumeral joint (GHJ) morphology and in-vivo GHJ motion are not well understood. The objectives of this study were to assess measures of joint morphology and their relationship with in-vivo joint motion in two populations: shoulders with intact rotator cuffs (n=48) and shoulders with rotator cuff pathology (n=36, including 5 symptomatic tears, 9 asymptomatic tears and 22 repaired tears). GHJ morphology was measured from CT-based three-dimensional models of the humerus and scapula. In-vivo GHJ motion was measured during shoulder abduction using biplane x-ray imaging. Associations between GHJ morphology and motion were assessed with univariate and best subsets regression. The only morphological difference identified between the populations was the critical shoulder angle (intact: 34.5 ± 4.7°, pathologic: 36.9 ± 5.0°, p=0.03), which is consistent with previous research. In intact shoulders, the superior/inferior (S/I) position of the humerus on the glenoid during shoulder abduction was significantly associated with the glenoid's S/I radius of curvature (p<0.01), conformity index (p<0.01), and stability angle (p<0.01). Furthermore, the S/I position of the humerus on the glenoid was negatively associated with the critical shoulder angle (p=0.04), which contradicts previous research. No significant associations between GHJ morphology and GHJ motion were detected in shoulders with rotator cuff tears. It is unknown if rotator cuff pathology compromises the relationships between GHJ morphology and motion, or if the absence of this relationship is a pre-existing condition that increases the likelihood of pathology.

Associations between in-vivo glenohumeral joint motion and morphology.

Measures of scapulothoracic motion are dependent on accurate imaging of the scapula and thorax. Advanced radiographic techniques can provide accurate measures of scapular motion, but the limited 3D imaging volume of these techniques often precludes measurement of thorax motion. To overcome this, a thorax coordinate system was defined based on the position of rib pairs and then compared to a conventional sternum/spine-based thorax coordinate system. Alignment of the rib-based coordinate system was dependent on the rib pairs used, with the rib3:rib4 pairing aligned to within 4.4 ± 2.1 deg of the conventional thorax coordinate system. 

Measuring Three-Dimensional Thorax Motion Via Biplane Radiographic Imaging: Technique and Preliminary Results.

Physical therapy (PT) is often prescribed for patients with rotator cuff tears. The extent to which PT influences strength, range of motion (ROM), and patient-reported outcomes has been studied extensively, but the effect of PT on in vivo joint kinematics is not well understood.

Effects of Rotator Cuff Pathology and Physical Therapy on In Vivo Shoulder Motion and Clinical Outcomes in Patients With a Symptomatic Full-Thickness Rotator Cuff Tear.

The incidence of asymptomatic rotator cuff tears has been reported to range from 15% to 39%, but the influence of asymptomatic rotator cuff pathology on shoulder function is not well understood. This study assessed the effects of asymptomatic rotator cuff pathology on shoulder kinematics, strength, and patient-reported outcomes.

Effects of asymptomatic rotator cuff pathology on in vivo shoulder motion and clinical outcomes.

We have developed a clinically viable method for measurement of direct, patient-specific intravertebral displacements using a novel digital tomosynthesis based digital volume correlation technique. These displacements may be used to calculate vertebral stiffness under loads induced by a patient's body weight; this is particularly significant because, among biomechanical variables, stiffness is the strongest correlate of bone strength. In this proof of concept study, we assessed the feasibility of the method through a preliminary evaluation of the accuracy and precision of the method, identification of a range of physiological load levels for which displacements are measurable, assessment of the relationship of measured displacements with microcomputed tomography based standards, and demonstration of the in vivo application of the technique.

Digital tomosynthesis based digital volume correlation: A clinically viable noninvasive method for direct measurement of intravertebral displacements using images of the human spine under physiological load.

The rotator cuff is theorized to contribute to force couples required to produce glenohumeral kinematics. Impairment in these force couples would theoretically result in impaired ball-and-socket kinematics. Although less frequently used than traditional kinematic descriptors (e.g., Euler angles, joint translations), helical axes are capable of identifying alterations in ball-and-socket kinematics by quantifying the variability (i.e., dispersion) in axis orientation and position during motion. Consequently, assessing glenohumeral helical dispersion may provide indirect evidence of rotator cuff function. The purpose of this exploratory study was to determine the extent to which rotator cuff pathology is associated with alterations in ball-and-socket kinematics. Fifty-one participants were classified into one of five groups based on an assessment of the supraspinatus using diagnostic imaging: asymptomatic healthy, asymptomatic tendinosis, asymptomatic partial-thickness tear, asymptomatic full-thickness tear, symptomatic full-thickness tear. Glenohumeral kinematics were quantified during coronal plane abduction using a biplane x-ray system and described using instantaneous helical axes. The degree to which glenohumeral motion coincided with ball-and-socket kinematics was described using the angular and positional dispersion about the optimal helical axis and pivot, respectively. No statistically significant difference was observed between groups in angular dispersion. However, symptomatic individuals with a full-thickness supraspinatus tear had significantly more positional dispersion than asymptomatic individuals with a healthy supraspinatus or tendinosis. These findings suggest that symptomatic individuals with a full-thickness supraspinatus tear exhibit impaired ball-and-socket kinematics, which is believed to be associated with a disruption of the glenohumeral force couples.

Article	Year
Validation of three-dimensional model-based tibio-femoral tracking during running. Medical engineering & physics\| PubMed ID: 18434230	2009
Associations between in-vivo glenohumeral joint motion and morphology. Journal of biomechanics\| PubMed ID: 26189094	2015
Measuring Three-Dimensional Thorax Motion Via Biplane Radiographic Imaging: Technique and Preliminary Results. Journal of biomechanical engineering\| PubMed ID: 26592901	2016
Effects of Rotator Cuff Pathology and Physical Therapy on In Vivo Shoulder Motion and Clinical Outcomes in Patients With a Symptomatic Full-Thickness Rotator Cuff Tear. Orthopaedic journal of sports medicine\| PubMed ID: 27734020	2016
Effects of asymptomatic rotator cuff pathology on in vivo shoulder motion and clinical outcomes. Journal of shoulder and elbow surgery\| PubMed ID: 28131679	2017
Digital tomosynthesis based digital volume correlation: A clinically viable noninvasive method for direct measurement of intravertebral displacements using images of the human spine under ph... Medical physics\| PubMed ID: 31381174	2019
Instantaneous helical axis estimation of glenohumeral kinematics: The impact of rotator cuff pathology. Journal of biomechanics\| PubMed ID: 32807327	2020

Roger Zauel

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