Measuring humeral head translation using fluoroscopy: A validation study

The linear intra-articular motions of the temporomandibular joint in individuals with severe forward head posture: A cross-sectional study

BACKGROUND

The cervical vertebrae and the temporomandibular joint (TMJ) may be linked through their common muscles.

OBJECTIVES

The aim of the present study was to compare the linear intra-articular motions of the TMJ between individuals with the normal craniocervical posture (CCP) and severe forward head posture (FHP).

DESIGN

Cross-sectional study.

METHODS

Volunteers (N = 38) were equally assigned to either the severe FHP group or the normal CCP group according to their craniovertebral angle (CVA). The CVA angles greater than 49° were considered as the normal CCP while angles between 44 and 40° were regarded as the severe FHP. The TMJ was imaged at the closed, median, and maximum open positions of the mouth using an ultrasound machine with a 7.5 MHz linear transducer in the sitting position. The best-fitting curve in the contour registration method was employed to measure displacement of the mandibular condyle on the transverse and vertical axes.

RESULTS

The forward displacement of the mandibular condyle in the severe FHP group was significantly (p-value = 0.037) reduced compared to the normal CCP group at maximum open position of the mouth, while no significant difference was revealed at closed (p-value = 0.937) or median open (p-value = 0.699) positions. The perpendicular displacement of the mandibular condyle exhibited no significant (p-value>0.107) difference between groups at any mouth position.

DISCUSSION

The current study demonstrated, for the first time, that severe FHP may impact the intra-articular motion of the TMJ. This study presumed that individuals with severe FHP may encounter a force imbalance in the anterior-posterior direction.

Fluoroscopic measurements of the glenohumeral joint position and space in true anteroposterior and axillary views – a reliability study

Two-dimensional (2D) fluoroscopy has been used in shoulder pathologies to estimate the humeral head position (HHP) in the true anteroposterior (AP) view. However, there is a lack of evidence regarding the reliability estimating it in the axillary view and in measuring the shoulder joint space width (JSW). True AP view images (n=36) of subjects with adhesive capsulitis were taken in supine in multiple arm abduction positions. The axillary view images (n=48) were taken in supine and prone in 75° of abduction. The HHP was assessed in the glenoid reference frame. The position and radius of the humeral head along with the superior, inferior, anterior, posterior, and middle JSWs were measured in each image. All the images were coded and randomly presented twice to a physiotherapist at a gap of 48-72 h for intra-rater reliability and to 2 therapists and an orthopaedic surgeon for inter-rater reliability. Reliability was expressed using intraclass correlation coefficients (ICC) and standard error of measurement (SEM). In both the views, inter-rater, and intra-rater reliability was excellent for the radius of the humeral head (inter-rater – 0.95-0.97 and intra-rater -0.98)], moderate (ICC: 0.70 and 0.76), and excellent (ICC: 0.89 and 0.93) for HHP. The reliability for JSWs was moderate to good (ICC: 0.66-0.82) for inter-rater and good to excellent (ICC: 0.75-0.95) for intra-rater analysis. The SEM for HHP and JSWs were <0.4 mm for intra-rater analysis, and <0.7 mm for inter-rater reliability in both views. The study demonstrated that the glenohumeral arthrokinematic parameters can be measured with good to excellent levels of reliability when using 2 D fluoroscopy.

The study is part of a clinical trial (Clinical Trial Registry India: CTRI/2018/12/016657).

Errors in Measuring Glenohumeral Arthrokinematics With 2-Dimensional Fluoroscopy

Two-dimensional fluoroscopic imaging allows measurement of small magnitude humeral head translations that are prone to errors due to optical distortion, out-of-plane imaging, repeated manual identification of landmarks, and magnification. This article presents results from in vivo and in vitro fluoroscopy-based experiments that measure the errors and variability in estimating the humeral head translated position in true scapular plane and axillary views. The errors were expressed as bias and accuracy. The variability with repeated digitization was calculated using the intraclass correlation coefficient (ICC) and the standard error of measurement. Optical distortion caused underestimation of linear distances. The accuracy was 0.11 and 0.43 mm for in vitro and in vivo experiments, respectively, for optical distortion. The intrarater reliability was excellent for both views (ICC = .94 and .93), and interrater reliability was excellent (ICC = .95) for true scapular view but moderate (ICC = .74) for axillary views. The standard error of measurement ranged from 0.27 to 0.58 mm. The accuracy for the humeral head position in 10° out of true scapular plane images ranged from 0.80 to 0.87 mm. The current study quantifies the magnitude of error. The results suggest that suitable measures could be incorporated to minimize errors and variability for the measurement of glenohumeral parameters.

The effects of a conservative rehabilitation program for multidirectional instability of the shoulder

BACKGROUND

Conservative management is commonly recommended as the first-line treatment for multidirectional instability (MDI) of the shoulder. Despite this, the evidence for efficacy of treatment is limited, and until recently, guidance for clinicians on conservative rehabilitation programs has been inadequate. This study evaluated the effectiveness of a physiotherapy-led exercise program for participants with MDI.

METHODS

In a single-group study design, 43 participants (16 male, 27 female; mean age, 19.8 years, standard deviation, 4.9 years) diagnosed with MDI undertook a 12-week exercise program. Primary outcome measures were the Melbourne Instability Shoulder Score, Western Ontario Shoulder Instability Index, and Oxford Shoulder Instability Score. Secondary outcomes were strength and scapular position. All measures were taken at baseline and repeated at the conclusion of the program. Test differences before and after rehabilitation were evaluated with dependent t tests and single-group effect size calculations (standardized mean difference [SMD]) to provide a measure of the magnitude of the difference.

RESULTS

Large effects were found between pre- and postrehabilitation scores on all functional instability questionnaires, with the Western Ontario Shoulder Instability Index demonstrating the largest effect (SMD, -3.04). Scapular upward rotation improved significantly in the early ranges of abduction (0°-60°), with moderate to large effects (SMDs, 0.54-0.95). All strength measures significantly improved, with large differences identified (SMDs, 0.69-2.08).

CONCLUSION

The identified improvement in functional status, shoulder muscle strength, and scapular positioning after rehabilitation allows greater confidence in the value of conservative management of MDI and informs further research by way of clinical trials in the area.

Glenohumeral and scapulohumeral kinematic analysis of patients with traumatic anterior instability wearing a shoulder brace: a prospective laboratory study

PURPOSE

To assess the effectiveness of a novel glenohumeral joint immobilizer, the S2 Shoulder Stabilizer^®, by evaluating shoulder kinematics with a stereophotogrammetry system.

METHODS

Participants in this prospective laboratory study were recruited from patients with anterior traumatic instability awaiting arthroscopic glenohumeral stabilization. Glenohumeral and scapulohumeral kinematic data (arm abduction-adduction and internal-external rotation, and scapular pronation-retraction and mediolateral rotation) were collected twice, without and with the brace, using a VICON™ motion capture system, and processed with MATLAB^® software.

RESULTS

The tests showed a significantly lower joint angle during abduction-adduction (p = 0.0022) and external rotation (p = 0.0076) and a significantly lower (p = 0.0022) mediolateral scapular rotation angle in the limbs wearing the immobilizer. Humeral head translation during abduction-adduction and internal-external rotation was also lower in the patients wearing the brace.

CONCLUSIONS

The immobilizer significantly limited joint excursion in all planes of movement except internal rotation. The narrower humeral head translation with respect to the trunk, measured in the tests with the brace, demonstrates that the immobilizer achieves the goal of preserving joint stability in the movements that are at risk of dislocation.

Glenohumeral translation in ABER position during muscle activity in patients treated with Latarjet procedure: an in vivo MRI study

PURPOSE

The Latarjet procedure is frequently performed when treating traumatic anteroinferior shoulder instability. This procedure is supposed to have a triple effect: osseous, muscular and ligamentous. The main stabilizing mechanism in cadaver studies on fresh-frozen shoulders seems to be the sling effect produced by the subscapularis and the conjoint tendon. It has been hypothesized that muscle contraction in ABER position (abduction-external rotation) is able to translate the humeral head posteriorly and superiorly due to the sling effect. The aim of this study was to analyse the humeral head translation relative to the glenoid with the arm in ABER position with and without muscle contraction.

METHODS

Twenty-one subjects divided into two groups (Group A: after Latarjet; Group B: healthy subjects) were examined with an open MRI system with the shoulder in abduction-external rotation (ABER) position to analyse humeral head translation during muscle activity.

RESULTS

In normal shoulders, there was no significant difference in anteroposterior or superoinferior translation between the rest position and the muscle-activated state. In subjects after the Latarjet procedure, the difference was significant and was also significant between both groups of subjects for posterior translation, but not for superior translation.

CONCLUSION

In patients treated with Latarjet procedure, there are significant changes in glenohumeral translation during muscular activity when in ABER position, with the humeral head going more posteriorly, in comparison with normal shoulders. This study confirms the stabilizing sling effect of the transposed conjoint tendon in the ABER position.

LEVEL OF EVIDENCE

Retrospective case-control study, Level III.

Glenohumeral translations during range-of-motion movements, activities of daily living, and sports activities in healthy participants

BACKGROUND

Glenohumeral translations have been mainly investigated during static poses while shoulder rehabilitation exercises, activities of daily living, and sports activities are dynamic. Our objective was to assess glenohumeral translations during shoulder rehabilitation exercises, activities of daily living, and sports activities to provide a preliminary analysis of glenohumeral arthrokinematics in a broad range of dynamic tasks.

METHODS

Glenohumeral translations were computed from trajectories of markers fitted to intracortical pins inserted into the scapula and the humerus. Two participants (P1 and P2) performed full range-of-motion movements including maximum arm elevations and internal-external rotations rehabilitation exercises, six activities of daily living, and five sports activities.

FINDINGS

During range-of-motion movements, maximum upward translation was 7.5mm (P1) and 4.7mm (P2). Upward translation during elevations was smaller with the arm internally (3.6mm (P1) and 2.9mm (P2)) than neutrally (4.2mm (P1) and 3.7mm (P2)) and externally rotated (4.3mm (P1) and 4.3mm (P2)). For activities of daily living and sports activities, only anterior translation during reach axilla for P1 and upward translation during ball throwing for P2 were larger than the translation measured during range-of-motion movements (108% and 114%, respectively).

INTERPRETATION

While previous electromyography-based studies recommended external rotation during arm elevation to minimize upward translation, measures of glenohumeral translations suggest that internal rotation may be better. Similar amplitude of translation during ROM movement and sports activities suggests that large excursions of the humeral head may be caused not only by fast movements, but also by large amplitude movements.

Coupling between 3D displacements and rotations at the glenohumeral joint during dynamic tasks in healthy participants

BACKGROUND

Glenohumeral displacements assessment would help to design shoulder prostheses with physiological arthrokinematics and to establish more biofidelic musculoskeletal models. Though displacements were documented during static tasks, there is little information on their 3D coupling with glenohumeral angle during dynamic tasks. Our objective was to characterize the 3D glenohumeral displacement-rotation couplings during dynamic arm elevations and rotations.

METHODS

Glenohumeral displacements were measured from trajectories of reflective markers fitted on intracortical pins inserted into the scapula and humerus. Bone geometry was recorded using CT-scan. Only four participants were recruited to the experiment due to its invasiveness. Participants performed dynamic arm abduction, flexion and axial rotations. Linear regressions were performed between glenohumeral displacements and rotations. The pin of the scapula of one participant moved, his data were removed from analysis, and results are based on three participants.

FINDINGS

The measurement error of glenohumeral kinematics was less than 0.15mm and 0.2°. Maximum glenohumeral displacements were measured along the longitudinal direction and reached up to +12.4mm for one participant. Significant couplings were reported especially between longitudinal displacement and rotation in abduction (adjusted R(2) up to 0.94).

INTERPRETATION

The proposed method provides the potential to investigate glenohumeral kinematics during all kinds of movements. A linear increase of upward displacement during dynamic arm elevation was measured, which contrasts with results based on a series of static poses. The systematic investigation of glenohumeral displacements under dynamic condition may help to provide relevant recommendation for the design of shoulder prosthetic components and musculoskeletal models.

Dynamic comparison of segmentary scapulohumeral rhythm between athletes with and without impingement syndrome

Background:

Patients who have shoulder pain usually have compensatory or contributory deviation of shoulder motion during arm elevation. In the traditional scapulohumeral rhythm, the share of the acromioclavicular (AC) and the sternoclavicular (SC) joint movements and also the role of AC internal rotation angle are unknown.

Objectives:

The main purpose of this study was to measure and compare the segmentary scapulohumeral rhythm (SSHR) during scapular arm elevation at a steady rotational speed in athletes with and without impingement syndrome.

Patients and Methods:

Using a speedometer, the maximum speed of arm elevation was measured in 21 men in each of the involved and uninvolved groups. Using fluoroscopy on the dominant side, SSHR during scapular arm elevation at a rotational speed equal to 1/30 of maximum speed was compared between the two groups. The ratio of glenohumeral (GH) elevation angle to AC rotation angle in the scapular plane was considered as SSHR.

Results:

The maximum speed of arm elevation between the two groups was significantly different (P < 0.001). The rhythm of the involved group significantly exceeded the rhythm of the uninvolved group in a part of the first quarter range of the arm elevation. SSHR during arm elevation in the uninvolved group did not change significantly (P = 0.845); however, it decreased significantly in the involved group (P = 0.024).

Conclusions:

Speed differences between the two groups were probably due to the pain in some ranges of arm elevation. SSHR in the involved group probably changed in order to compensate downward rotation of the scapula in the resting position. Study of the AC upward rotation range can be misleading; therefore, the study of scapulohumeral rhythm is recommended.

Humeral head translation after a suprascapular nerve block

Subacromial impingement syndrome is the most common shoulder disorder. Abnormal superior translation of the humeral head is believed to be a major cause of this pathology. The first purpose of the study was to examine the effects of suprascapular nerve block on superior translation of the humeral head and scapular upward rotation during dynamic shoulder elevation. The secondary purpose was to assess muscle activation patterns during these motions. Twenty healthy subjects participated in the study. Using fluoroscopy and electromyography, humeral head translation and muscle activation were measured before and after a suprascapular nerve block. The humeral head was superiorly located at 60 degrees of humeral elevation, and the scapula was more upwardly rotated from 30 to 90 degrees of humeral elevation after the block. The differences were observed during midrange of motion. In addition, the deltoid muscle group demonstrated increased muscle activation after the nerve block. The study's results showed a compensatory increase in humeral head translation, scapular upward rotation, and deltoid muscle activation due to the nerve block. These outcomes suggest that increasing muscular strength and endurance of the supraspinatus and infraspinatus muscles could prevent any increased superior humeral head translation. This may be beneficial in reducing shoulder impingement or rotator cuff tears over time.