Pseudoparalysis and pseudoparesis of the shoulder

Background Clinical presentation of massive rotator cuff tears range from pain to loss of active range of motion. Pseudoparalysis and pseudoparesis are defined inconsistently in the literature, but both include limited active with maintained passive range of motion. Objective This article aims to provide a consistent definition of pseudoparalysis and pseudoparesis of the shoulder and show structural and biomechanical differences between these two types of rotator cuff tear with their implications for treatment. Methods A literature review including key and basic papers discussing clinical symptoms, biomechanical differences, and their impact on therapeutic options for pseudoparalysis and pseudoparesis was performed. Results Biomechanically, structural differences between pseudoparalysis (active scapular plane abduction <45°) and pseudoparesis (active scapular plane abduction 45–90°) exist. For massive posterosuperior rotator cuff tears, the integrity of the inferior subscapularis tendon is the most predictive factor for active humeral elevation. Patients with pseudoparalysis have a higher grade of subscapularis tendon involvement (>50%) and fatty infiltration of the subscapularis muscle. Treatment options depend on the acuteness and repairability of the tear. Rotator cuff repair can reliably reverse the active loss of active range of motion in acute and reparable rotator cuff tears. In chronic and irreparable cases reverse total shoulder arthroplasty is the most reliable treatment option in elderly patients. Conclusion The most concise definition of pseudoparalysis is a massive rotator cuff tear that leads to limited active (<45° shoulder elevation) with free passive range of motion in the absence of neurologic deficits as the reason for loss of active elevation. The integrity of the subscapularis tendon is the most important difference between a pseudoparalytic and pseudoparetic (active shoulder elevation 45–90°) shoulder. Decision-making for surgical options depends more on reparability of the tendon tear and patient age than on differentiation between pseudoparalysis and pseudoparesis.

Maximizing Muscle Function in Cuff-Deficient Shoulders: A Rehabilitation Proposal for Reverse Arthroplasty

Purpose The purpose of this review is to describe the role of altered joint biomechanics in reverse shoulder arthroplasty and to propose a rehabilitation protocol for a cuff-deficient glenohumeral joint based on the current evidence. Methods and Materials: The proposed rehabilitation incorporates the principles of pertinent muscle loading while considering risk factors and surgical complications. Results In light of altered function of shoulder muscles in reverse arthroplasty, scapular plane abduction should be more often utilized as it better activates deltoid, teres minor, upper trapezius, and serratus anterior. Given the absence of supraspinatus and infraspinatus and reduction of external rotation moment arm of the deltoid in reverse arthroplasty, significant recovery of external rotation may not occur, although an intact teres minor may assist external rotation in the elevated position. Conclusion Improving the efficiency of deltoid function before and after reverse shoulder arthroplasty is a key factor in the rehabilitation of the cuff deficient shoulders. Performing exercises in scapular plane and higher abduction angles activates deltoid and other important muscles more efficiently and optimizes surgical outcomes.

Chronic Pseudoparalysis Needs to Be Distinguished From Pseudoparesis: A Structural and Biomechanical Analysis

Background: Chronic pseudoparalysis is generally defined as the inability to actively elevate the arm above 90° with free passive range of motion and no neurological deficits. It has been suggested that this arbitrary cutoff needs to be refined. Purpose: To analyze whether there are structural and biomechanical differences in patients with chronic pseudoparalysis and those with chronic pseudoparesis. Study Design: Case-control study; Level of evidence, 3. Methods: In this retrospective study, 50 patients with chronic massive rotator cuff tears (mRCTs; ≥2 tendons) and free passive and active scapular plane abduction <90° were divided into 2 groups: pseudoparalysis group (n = 24; active scapular plane abduction, <45°) and pseudoparesis group (n = 26; active scapular plane abduction, >45° and <90°). Radiographic measurements included the critical shoulder angle, acromiohumeral distance, posterior acromial tilt, anterior and posterior acromial coverages, and posterior acromial height on outlet views. Measurements on magnetic resonance imaging (MRI) included fatty infiltration of the rotator cuff muscles, anterior (subscapularis) and posterior (infraspinatus/teres minor) tear extensions, and global (anterior + posterior) tear extension in the parasagittal plane. A published musculoskeletal model was used to simulate the effect of different mRCTs on the muscle force required for scapular plane abduction. Results: Plain radiographs revealed no differences between patients with chronic pseudoparalysis and those with pseudoparesis. MRI assessment showed significant differences between patients with chronic pseudoparalysis and those with pseudoparesis with respect to fatty infiltration of the subscapularis (2.9 vs 1.6; P < .001) and infraspinatus (3.6 vs 3.0; P < .001) muscles, and anterior (−23° vs 4°; P < .001), posterior (−23° vs −14°; P = .034), and global rotator cuff (225° vs 190°; P < .001) tear extensions. The anterior tear extension in patients with chronic pseudoparalysis always involved more than 50% of the subscapularis, which was associated with an odds ratio of 5 for inability to actively abduct more than 45°. The biomechanical model was unable to find a combination of muscles that could balance the arm in space when the tear extended beyond the supraspinatus and the cranial subscapularis. Conclusion: This study confirms that chronic pseudoparalysis and pseudoparesis are associated with different structural lesions. In the setting of a chronic mRCT, involvement of more than 50% of the subscapularis tendon with fatty infiltration of stage 3 is associated with pseudoparalysis of active scapular plane abduction <45°. The key function of the subscapularis was confirmed in the biomechanical model.

The Application of Double Elastic Band Exercise in the 90/90 Arm Position for Overhead Athletes

Background: Traditional exercises performed with the shoulder in the position of 90° abduction and external rotation with elbow flexion (90/90) while using a single elastic band showed moderate activity of both the lower trapezius (LT) and infraspinatus (IS) muscle. The purpose of this study was to investigate activity of the teres minor (TMi) and the LT muscles during standing external rotation exercise with the shoulder in the 90/90 position with 2 elastic bands in both the frontal and the scapular plane. Hypothesis: TMi, IS, and LT muscle activities will vary depending on whether the shoulder is positioned in the frontal or scapular plane with the application of 2 elastic bands. Also, the serratus anterior (SA) and teres major (TMa) muscles will produce different muscular activity patterns during exercises performed with 2 elastic bands in the frontal plane compared with the TMi and LT muscles. Study Design: Controlled laboratory study Level of Evidence: Level 4. Methods: A total of 21 collegiate baseball players volunteered to participate. The electromyography (EMG) activities of the TMi, IS, LT, SA, TMa, middle deltoid (MD), posterior deltoid, and upper trapezius (UT) muscles were measured with the 90/90 arm position during both isometric and oscillation resistance exercises with 2 elastic bands oriented in the frontal and scapular planes. Results: A significant difference was observed in EMG activity of both the TMi and the LT muscles between single and double elastic band applications in the frontal plane ( P < 0.05). In contrast, EMG activity of the IS, SA, and TMa muscles was significantly increased in the scapular plane compared with the frontal plane ( P < 0.05). Conclusion: The standing 90/90 position effectively increased both TMi and LT muscle EMG activity with the double elastic band in the frontal plane while minimizing UT and MD muscle activity. EMG activity of the IS, SA, and TMa muscles increased with exercise in the scapular plane as compared with the frontal plane. Clinical Relevance: Oscillation movement under double elastic band application differentiated external rotator muscle and scapular muscle activities between the frontal and scapular plane during the 90/90 exercise in the frontal plane compared with the scapular plane. Clinicians can utilize each of the scapular and frontal positions based on their desired focus for muscular activation.

Scapular Morphologic Characteristics and Rotator Cuff Tear Pattern Are Independently Associated With Chronic Pseudoparalyis: A Matched-Pair Analysis of Patients With Massive Rotator Cuff Tears

Background: It is unclear which structural parameters determine the development or the absence of chronic pseudoparalysis (PP) in patients with massive rotator cuff tears (mRCTs). Purpose: To determine whether scapular morphologic characteristics and extent of rotator cuff tearing are independent factors associated with chronic PP. Study Design: Case-control study; Level of evidence, 3. Methods: In this retrospective case-control study, 50 patients with chronic mRCT (≥2 fully detached tendons) and active scapular plane abduction less than 90° (PP group) were age- and sex-matched with a cohort of 50 patients with chronic mRCT and an active scapular plane abduction greater than 90° (non-PP; NPP group). Analysis of standardized, plain radiographs included measurement of the critical shoulder angle (CSA) and the acromiohumeral distance (ACHD) on anteroposterior views and measurement of posterior acromial tilt, anterior and posterior acromial coverage, and posterior acromial height on standardized outlet views. Measurements on magnetic resonance imaging included fatty muscle infiltration, anterior (subscapularis) and posterior (infraspinatus/teres minor) tear extension, and global tear extension (anterior + posterior tear extension) in the parasagittal plane. Results: Overall, no significant difference was found in patients’ demographic characteristics ( P > .05). Univariate analyses confirmed significant differences between the PP and NPP groups in active scapular plane abduction (51°± 22° vs 135°± 29°; P < .001). Multivariate analyses revealed independent factors associated with PP compared with the NPP group: CSA (38.2°± 4.6° vs 35.2°± 3.7°; P = .001); ACHD (4.7 ± 2.2 vs 7.3 ± 2.6 mm; P < .001); posterior acromial height (22 ± 10 vs 17 ± 7 mm; P = .005); and anterior (–9°± 21° vs 25°± 12°; P < .001) and posterior (–18°± 14° vs 2°± 14°; P < .001) tear extension. The NPP group had significantly less involvement and fatty infiltration of the subscapularis (1.4 ± 0.6) compared with the PP group (2.2 ± 0.9) ( P < .001). Conclusion: This study confirms that global RCT extension and the quality of the inferior half of the subscapularis are significantly associated with chronic pseudoparalysis. The study further shows that acromial morphologic characteristics are relevant in the development of pseudoparalysis. Patients with pseudoparalysis have a larger CSA, less ACHD, and a higher positioned acromion in the sagittal plane.

Dynamic scapulohumeral rhythm: Comparison between healthy shoulders and those with large or massive rotator cuff tear

Introduction: Assessment of scapular kinematics and the dynamics of the scapulohumeral rhythm (SHR) would be important for understanding pathologies of the shoulder and to inform treatment. Our aim in this study was to evaluate the SHR and scapular kinematics in patients with a rotator cuff tear (RCT), compared to a control group with healthy shoulders using image-matching techniques. Materials and Methods: The shoulder kinematics of large or massive RCT patients were evaluated and compared to a control group with healthy shoulders. Radiographic surveillance was performed throughout the full range of external rotation and scapular plane abduction. Computed tomography imaging of the shoulder complex was performed, with three-dimensional image reconstruction and matching to the radiographs to measure three-dimensional positions and orientations. SHR and angular values of the scapula were measured. Results: Scapular external rotation in the late phase of external rotation movement was greater in the RCT group than in the control group ( p < 0.05), but with no difference in the SHR. During scapular plane abduction, there were significant differences in SHR, scapular posterior tilt and scapular upward rotation between the RCT and control group ( p < 0.05). Conclusions: Regarding clinical relevance, this study clarified the differences of SHR and angular values of the scapula between the RCT and control group. These results underline the importance of assessment the SHR and scapular kinematics in individuals with a RCT. RCT is associated with specific compensation in the kinematics of the scapula and SHR during external rotation and scapular plane abduction, which could inform treatment.

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.

Therapeutic Interventions for Scapular Kinematics and Disability in Patients With Subacromial Impingement: A Systematic Review

Context Impaired scapular kinematics are commonly reported in patients with subacromial impingement syndrome (SIS). Various therapeutic interventions designed to improve scapular kinematics and minimize pain and disability have been described in the literature. However, the short- and long-term benefits of these interventions are unclear. Objective To determine the effects of specific short- and long-term therapeutic interventions on scapular kinematics and disability in patients with SIS. Data Sources We searched PubMed, CINAHL, and SPORTDiscus databases from their origins to January 2018 using a combination of the key words scapular kinematics AND (shoulder dysfunction OR subacromial impingement) and conducted a manual search by reviewing the references of the identified papers. Study Selection Studies were included if (1) preintervention and postintervention measures were available; (2) patient-reported outcomes were reported; (3) scapular kinematics measures at 90° of ascending limb elevation in the scapular plane were included; (4) SIS was diagnosed in participants or participants self-reported symptoms of SIS; (5) they were original clinical studies published in English; and (6) the sample sizes, means, and measure of variability for each group were reported. Data Extraction Seven studies were found. Sample sizes, means, and standard deviations of scapular upward rotation, posterior tilt, and internal rotation at 90° of ascending limb elevation on the scapular plane and the Disabilities of the Arm, Shoulder and Hand scores were extracted. Data Synthesis Standardized mean differences between preintervention and postintervention measures with 95% confidence intervals (CIs) were calculated. We observed that the Disabilities of the Arm, Shoulder and Hand scores improved (mean difference = 0.85; 95% CI = 0.54, 1.16) but did not observe changes in scapular upward rotation (mean difference = −0.04; 95% CI = −0.31, 0.22), posterior tilt (mean difference = −0.09; 95% CI = −0.32, 0.15), or internal rotation (mean difference = 0.06; 95% CI = −0.19, 0.31). Conclusions The short- and long-term therapeutic interventions for SIS improved patient-reported outcomes but not scapular kinematics. The identified improvements in shoulder pain and function were not likely explained by changes in scapular kinematics.