Glenohumeral joint translation and muscle activity in patients with symptomatic rotator cuff pathology: An ultrasonographic and electromyographic study with age-matched controls

Abnormal Wrist Sagittal Kinematics in Gymnasts With Dorsal Wrist Pain: A New Syndrome

BACKGROUND

The pathology of dorsal wrist pain in gymnasts without abnormal radiographic findings remains unclear.

PURPOSE/HYPOTHESIS

The purpose of this study was to identify abnormal wrist sagittal kinematics in gymnasts with dorsal wrist pain. It was hypothesized that gymnasts with dorsal wrist pain would show abnormal sagittal kinematics with reversible hypermobility of the intercarpal joint.

STUDY DESIGN

Controlled laboratory study.

METHODS

Participants included 19 wrists in male gymnasts with dorsal wrist pain, 18 wrist in male gymnasts without wrist pain, and 20 adult men without a history of wrist pain. Magnetic resonance imaging (T2-weighted sagittal images) findings at 0°, 30°, 60°, and 90° of wrist extension were used in kinematic analysis. The angles and translations of the radiolunate, capitolunate, and third carpometacarpal joint were measured and compared between the 3 groups.

RESULTS

At 90° of wrist extension, gymnasts with dorsal wrist pain had a significantly lower radiolunate joint angle (28.70°± 6.28° vs 36.19°± 7.81°; P = .020) and a significantly higher capitolunate joint angle (57.99°± 6.15° vs 50.50°± 6.98°; P = .004) and distal translation (1.17 ± 0.50 mm vs 0.46 ± 0.62 mm; P = .002) than gymnasts without dorsal wrist pain.

CONCLUSION

Gymnasts with dorsal wrist pain showed abnormal wrist sagittal kinematics. These novel findings may facilitate understanding of dorsal wrist pain, which can be recognized as a new syndrome termed "gymnast's lunate dyskinesia."

Mechanical characteristic of supraspinatus muscle changes independent of its size and intramuscular fat in patient with rotator cuff repair

PURPOSE

This study aimed i) to investigate the mechanical, morphological, and compositional characteristics of the supraspinatus muscle after rotator cuff repair by using ultrasound shear wave elastography (SWE) and B-mode imaging, and ii) to determine whether the morphological or compositional characteristics are associated with the mechanical characteristic of the supraspinatus during contraction.

METHODS

Using SWE and B-mode imaging, active and passive shear moduli, muscle thickness, and echo intensity of the supraspinatus were measured from the repaired and contralateral control shoulders of 22 patients with rotator cuff repair. The shear modulus, muscle thickness, and echo intensity were compared between the repaired and control shoulders. The association between the active shear modulus and the other variables was determined.

RESULTS

While the active and passive shear moduli were lower in the repaired shoulder compared to the control, the muscle thickness and echo intensity did not vary between them. Interestingly, the passive shear modulus was positively correlated with the active shear modulus only in the control shoulder.

CONCLUSION

The mechanical characteristic of supraspinatus remains impaired, even without degenerative changes in the morphological and compositional characteristics after rotator cuff repair. Furthermore, the association between contractile and elastic characteristics in the supraspinatus was deteriorated in control shoulder.

Effects of Different Orthoses on Neuromuscular Activity of Superficial and Deep Shoulder Muscles during Activities of Daily Living and Physiotherapeutic Exercises in Healthy Participants

BACKGROUND

This study aimed to investigate the effects of different shoulder orthoses on the neuromuscular activity of superficial and deep shoulder muscles during activities of daily living (ADL) and physiotherapeutic exercises.

METHODS

Ten participants with healthy shoulders (31 ± 3 years, 23.1 ± 3.8 kg/m²) were randomized to receive a "shoulder sling", an "abduction pillow" and a "variably adjustable orthosis" on the dominant side. With each orthosis, they completed seven ADL with and four physiotherapeutic exercises without wearing the orthoses. An electromyographic system was used to record the neuromuscular activity of three superficial (trapezius, deltoid, pectoralis major) and two deep shoulder muscles (infraspinatus, supraspinatus) using surface and intramuscular fine-wire electrodes.

RESULTS

The neuromuscular activity differs between the orthoses during ADL (p ≤ 0.045), whereby the "variably adjustable orthosis" mostly showed the highest activation levels associated with the worst subjective wearing comfort rated on a visual analog scale. In addition, differences exist between the physiotherapeutic exercises (p ≤ 0.006) demonstrating the highest activations of the infra- and supraspinatus muscles for assistive elevation and wipe across a table, middle for pendulum and lowest for continuous passive motion exercises.

CONCLUSIONS

The neuromuscular activity of superficial and deep shoulder muscles differs between the orthoses during ADL and also between the physiotherapeutic exercises.

Muscle Contraction Has a Reduced Effect on Increasing Glenohumeral Stability in the Apprehension Position

PURPOSE

Glenohumeral instability accounts for 23% of all shoulder injuries among collegiate athletes. The apprehension position-combined shoulder abduction and external rotation-commonly reproduces symptoms in athletes with instability. Rehabilitation aims to increase glenohumeral stability by strengthening functional positions. However, it is unclear how much glenohumeral stability increases with muscle contraction in the apprehension position. The purpose of this study was to determine whether the ability to increase translational glenohumeral stiffness, a quantitative measure of glenohumeral stability, with muscle contraction is reduced in the apprehension position.

METHODS

Seventeen asymptomatic adults participated. A precision-instrumented robotic system applied pseudorandom, anterior-posterior displacements to translate the humeral head within the glenoid fossa and measured the resultant forces as participants produced isometric shoulder torques. Measurements were made in neutral abduction (90° abduction/0° external rotation) and apprehension (90° abduction/90° external rotation) positions. Glenohumeral stiffness was estimated from the relationship between applied displacements and resultant forces. The ability to increase glenohumeral stiffness with increasing torque magnitude was compared between positions.

RESULTS

On average, participants increased glenohumeral stiffness from passive levels by 91% in the neutral abduction position and only 64% in the apprehension position while producing 10% of maximum torque production. The biggest decrease in the ability to modulate glenohumeral stiffness in the apprehension position was observed for torques generated in abduction (49% lower, P < 0.001) and horizontal abduction (25% lower, P < 0.001).

CONCLUSION

Our results demonstrate that individuals are less able to increase glenohumeral stiffness with muscle contraction in the apprehension position compared with a neutral shoulder position. These results may help explain why individuals with shoulder instability more frequently experience symptoms in the apprehension position compared with neutral shoulder positions.

Biomechanical comparison of zoned-conformity glenoid versus standard glenoid in total shoulder arthroplasty: impact on rotator cuff strain and glenohumeral translation

BACKGROUND

Current standard total shoulder arthroplasty glenoid implants allow for high levels of glenohumeral mismatch and associated high levels of humeral head translation to improve range of motion and reduce rim stresses on the glenoid. However, high levels of glenohumeral mismatch could also increase glenoid edge loading, eccentric wear, and rotator cuff strain. A zoned-conformity glenoid may be able to reduce the forces on the rotator cuff and glenoid. We compared rotator cuff strain and glenohumeral translation between a standard glenoid (SG) with moderate glenohumeral mismatch and a zoned-conformity glenoid (conforming glenoid [CG]) that limits mismatch. We hypothesized that the CG would have lower levels of strain on the rotator cuff and lower levels of humeral head translation compared with the SG.

METHODS

Eight fresh frozen cadaveric shoulders, aged 72 years (range, 67-76 years), were used in this biomechanical study. The specimens were first tested in the intact state. We cycled them 3 times from 0° to 60° of abduction and measured the superiorly-inferiorly and anteriorly-posteriorly directed forces at the joint, compressive forces applied to the glenoid, and humeral head translation. The specimens were then implanted with a standard press-fit humeral component and a polyethylene glenoid with 3 peripherally cemented pegs and a central press-fit peg. Testing was repeated. Finally, the SG was removed, the CG was implanted, and each specimen was tested a third time.

RESULTS

The average superiorly directed force at the glenohumeral joint was significantly lower in the intact and CG groups (18.1 ± 18.6 N and 19.8 ± 16.2 N, respectively) than in the SG group (29.3 ± 21.9 N, P = .024). The maximum force directed against the glenoid was also significantly lower in the CG group (87.6 ± 11.7 N) than in the SG (96.0 ± 7.3 N) and intact (98.9 ± 16.5 N) groups (P = .035). No difference was observed in humeral head translation in the anterior-posterior plane from 0° to 60° of abduction (P = .998) or in the superior-inferior plane (P = .999).

CONCLUSION

A zoned-conformity glenoid was associated with similar humeral head translation but significantly lower superior forces against the rotator cuff and a significantly lower maximum force against the glenoid compared with an SG implant. These biomechanical findings suggest that a zoned-conformity implant warrants further study in the effort to maintain humeral head translation while reducing rotator cuff and glenoid forces for successful outcomes of total shoulder arthroplasty.

Shoulder biomechanics in normal and selected pathological conditions

The stability of the glenohumeral joint depends on soft tissue stabilizers, bone morphology and dynamic stabilizers such as the rotator cuff and long head of the biceps tendon. Shoulder stabilization techniques include anatomic procedures such as repair of the labrum or restoration of bone loss, but also non-anatomic options such as remplissage or tendon transfers.

Rotator cuff repair should restore the cuff anatomy, reattach the rotator cable and respect the coracoacromial arch whenever possible. Tendon transfer, superior capsular reconstruction or balloon implantation have been proposed for irreparable lesions.

Shoulder rehabilitation should focus on restoring balanced glenohumeral and scapular force couples in order to avoid an upward migration of the humeral head and secondary cuff impingement. The primary goal of cuff repair is to be as anatomic as possible and to create a biomechanically favourable environment for tendon healing.

Cite this article: EFORT Open Rev 2020;5:508-518. DOI: 10.1302/2058-5241.5.200006

A comparison of glenohumeral joint translation between young and older asymptomatic adults using ultrasonography: a secondary analysis

Background: The rotator cuff muscles are subject to age-related changes, but the effect of aging on glenohumeral joint stability is poorly understood. Objectives: This study aimed to compare glenohumeral joint translation in asymptomatic young and older people. Methods: Twenty young (23.6 ± 5.3 years) and twenty older (66.5 ± 7.8 years) participants with no symptomatic shoulder pathology were recruited. Anterior and posterior glenohumeral joint translations were measured using real-time ultrasound in two positions: (1) shoulder neutral; and (2) shoulder at 90 degrees' abduction and four testing conditions: (1) rest; (2) passive accessory motion testing (PAMT) force alone; (3) PAMT with isometric internal rotation contraction; and (4) PAMT with external rotation contraction. Results: In both groups, there were significant differences between the amount of translation limited by anterior and posterior rotator cuff muscles in response to anterior and posterior PAMT force (p < 0.03), indicating rotator cuff activity-limited translation in a direction-specific manner. Young participants demonstrated increased passive posterior glenohumeral joint translation in the neutral shoulder position (p < 0.001) and their rotator cuff muscle contraction led to greater reductions in glenohumeral joint translation in the neutral shoulder position (p < 0.001), as compared with older participants. Conclusions: Rotator cuff contraction limits glenohumeral joint translation in a direction-specific manner in both young and older participants. However, younger age is associated with increased passive translation but greater ability to reduce glenohumeral joint translation with rotator cuff muscle contraction. Age-related changes should be considered when assessing and treating glenohumeral joint stability.