Comparing in vivo three-dimensional shoulder elevation kinematics between standing and supine postures

In Vivo 3-Dimensional Dynamic Evaluation of Shoulder Kinematics After the Latarjet Procedure: Comparison With the Contralateral Healthy Shoulder

Background

Researchers have attempted to understand the underlying mechanism of the Latarjet procedure; however, its effects on shoulder kinematics have not been well studied.

Purpose/Hypothesis

The purpose was to analyze shoulder kinematics after the Latarjet procedure. It was hypothesized that the nonanatomic transfer of the coracoid process during the procedure would affect normal shoulder kinematics.

Study Design

Controlled laboratory study.

Methods

The study included 10 patients (age range, 20-52 years) who underwent the modified Latarjet procedure between June 2016 and November 2021. Computed tomography and fluoroscopy were conducted on both shoulder joints of all patients, and 3-dimensional models were reconstructed. The 3-dimensional coordinates were encoded on the reconstructed models, and shoulder kinematics were analyzed through a 3-dimensional-2-dimensional model-image registration technique. Scapular rotation parameters (scapular upward rotation, posterior tilt, external rotation, and scapulohumeral rhythm) were compared between the Latarjet and the nonsurgical contralateral sides during humeral abduction, as was anteroposterior (AP) translation relative to the glenoid center during active humeral external rotation.

Results

The Latarjet side displayed significantly higher values of scapular upward rotation at higher degrees of humeral elevation (130°, 140°, and 150°) compared with the nonsurgical side (P = .027). Posterior tilt, external rotation, and scapulohumeral rhythm were not significantly different between sides. AP translation at maximal humeral rotation was not significantly different between sides (Latarjet, -0.06 ± 5.73 mm vs nonsurgical, 5.33 ± 1.60 mm; P = .28). Interestingly, on the Latarjet side, AP translation increased until 40° of humeral rotation (4.27 ± 4.64 mm) but began to decrease from 50° of humeral rotation.

Conclusion

The Latarjet side demonstrated significant changes in scapular upward rotation during higher degrees of humeral elevation compared with the contralateral shoulder. Posterior movement of the humeral head at >50° of humeral rotation could be the desired effect of anterior stabilization; however, researchers should evaluate long-term complications such as osteoarthritis.

Clinical Relevance

Analysis of shoulder kinematics after the Latarjet procedure could provide information regarding long-term outcomes and whether the procedure would affect the daily activities of patients.

Joint Track Machine Learning: An Autonomous Method of Measuring Total Knee Arthroplasty Kinematics From Single-Plane X-Ray Images

BACKGROUND

Dynamic radiographic measurements of 3-dimensional (3-D) total knee arthroplasty (TKA) kinematics have provided important information for implant design and surgical technique for over 30 years. However, current methods of measuring TKA kinematics are too cumbersome, inaccurate, or time-consuming for practical clinical application. Even state-of-the-art techniques require human-supervision to obtain clinically reliable kinematics. Eliminating human supervision could potentially make this technology practical for clinical use.

METHODS

We demonstrate a fully autonomous pipeline for quantifying 3D-TKA kinematics from single-plane radiographic imaging. First, a convolutional neural network (CNN) segmented the femoral and tibial implants from the image. Second, those segmented images were compared to precomputed shape libraries for initial pose estimates. Lastly, a numerical optimization routine aligned 3D implant contours and fluoroscopic images to obtain the final implant poses.

RESULTS

The autonomous technique reliably produces kinematic measurements comparable to human-supervised measures, with root-mean-squared differences of less than 0.7 mm and 4° for our test data, and 0.8 mm and 1.7° for external validation studies.

CONCLUSION

A fully autonomous method to measure 3D-TKA kinematics from single-plane radiographic images produces results equivalent to a human-supervised method, and may soon make it practical to perform these measurements in a clinical setting.

Glenoid Track Width Is Smaller Under Dynamic Conditions: An In Vivo Dual-Fluoroscopy Imaging Study

BACKGROUND

The glenoid track concept has been widely used to assess the risk of instability due to bipolar bone loss. The glenoid track width was commonly used as 83% of the glenoid width to determine if a lesion was on-track or off-track. However, the value was obtained under static conditions, and it may not be able to reflect the actual mechanism of traumatic dislocation during motion.

PURPOSE

To compare the glenoid track width under dynamic and static conditions using a dual-fluoroscopic imaging system.

STUDY DESIGN

Controlled laboratory study.

METHODS

In total, 40 shoulders of 20 healthy volunteers were examined for both dynamic and static tests within a dual-fluoroscopic imaging system at 5 different arm positions: 30°, 60°, 90°, 120°, and 150° of abduction, keeping the shoulder at 90° of external rotation. The participants performed a fast horizontal arm backswing for dynamic tests while keeping their arm in maximum horizontal extension for static tests. Computed tomography scans were used to create 3-dimensional models of the humerus and scapula for 2-dimensional to 3-dimensional image registration. Magnetic resonance imaging scans were obtained to delineate the medial margin of the rotator cuff insertion. The glenoid track width was measured as the distance from the anterior rim of the glenoid to the medial margin of the rotator cuff insertion and compared between static and dynamic conditions.

RESULTS

The mean glenoid track widths at 30°, 60°, 90°, 120°, and 150° of abduction were significantly smaller under dynamic conditions (88%, 81%, 72%, 69%, and 68% of the glenoid width) than those under static conditions (101%, 92%, 84%, 78%, and 77% of the glenoid width) (all P < .001). The glenoid track width significantly decreased with the increasing abduction angles in the range of 30° to 120° under static conditions (all P < .003) and 30° to 90° under dynamic conditions (all P < .001).

CONCLUSION

A smaller dynamic-based value should be considered for the glenoid track width when distinguishing on-track/off-track lesions. Clinical evidence is needed to establish the superiority of the dynamic-based value over the static-based value as an indicator for augmentation procedures.

CLINICAL RELEVANCE

Some off-track lesions might be misclassified as on-track lesions when the original commonly used static-based value of 83% is used as the glenoid track width.