Assessing the treatment response of lateral elbow tendinopathy using time-dependent ultrasonography, Doppler imaging, and elastography.

OBJECTIVE: To investigate the structural alterations, neovascularity, and elasticity of tendons and the relationship between elasticity and the Patient Rated Tennis Elbow Evaluation score after undergoing US-guided fenestration or surgery in patients with chronic lateral elbow tendinopathy. METHODS: Participants from the per-protocol population of a randomized trial conducted between October 2016 and June 2020 were included. The surgery and fenestration groups included 24 (mean age, 50 ± 7 years [standard deviation], 10 men) and 29 (47 ± 8 years, 18 men) participants, respectively. Ultrasound exams were performed at baseline, 6 months, and 12 months. Statistical analyses included linear mixed effects and generalized equation estimation models. RESULTS: Fenestration had no significant impact on tendon thickness (p = 0.46). Conversely, surgery significantly increased tendon thickness at 6 months (p < 0.0001) and remained elevated at 12 months (p = 0.04). Tendon echostructure exhibited a group effect (p = 0.03), indicating a higher proportion of pathological scores in the surgery group post-intervention compared to the fenestration group. Both groups showed a similar reduction in neovascularity from 6 to 12 months postintervention (p = 0.006). Shear-wave velocity increased in the fenestration group at 6 months (p = 0.04), while the surgery group experienced a nonsignificant decrease at 6 months, with some improvement at 12 months (p = 0.08). Changes in shear-wave velocity did not correlate with clinical outcome. CONCLUSIONS: Fenestration and surgery reduced tendon neovascularity over time. Unlike surgery, fenestration did not impact tendon size while improving tendon echostructure and elasticity. CRITICAL RELEVANCE STATEMENT: Fenestration and surgery equally alleviated symptoms and decreased tendon neovascularity in lateral elbow tendinopathy; however, fenestration did not alter tendon thickness and improved echostructure and shear-wave velocity, suggesting shear-wave velocity's potential for quantitatively monitoring tendon elasticity during healing. KEY POINTS: Reliable markers for monitoring healing response and informing treatment protocols in elbow tendinopathy are lacking. Fenestration and surgery reduced tendon neovascularity, while fenestration improved tendon echostructure and shear-wave velocity. Shear-wave velocity may provide quantitative measures to monitor tendon elasticity in response to treatment.

Treatment of chronic lateral epicondylosis: a randomized trial comparing the efficacy of ultrasound-guided tendon dry needling and open-release surgery.

OBJECTIVE: Evaluate the efficacy of ultrasound-guided dry needling and open-release surgery in reducing pain and improving function in workers with lateral epicondylosis refractory to at least 6 months of nonsurgical management. METHODS: We randomly assigned participants in a 1:1 ratio to receive dry needling or surgery. The primary outcome was the Patient Rated Tennis Elbow Evaluation (PRTEE) score at 6 months. Secondary outcome measures examined the impact of these techniques on professional activity, grip strength, and Global Rating of Change and Satisfaction scales. Statistical analyses included mixed-effects models and Fisher's exact tests. RESULTS: From October 2016 through June 2019, we enrolled 64 participants. Two participants were excluded, and data from 62 participants (48 ± 8 years, 33 men) with a mean duration of symptoms of 23 ± 21 months were analyzed. Baseline characteristics were similar in both groups. In the intention-to-treat analysis, no treatment-by-time interaction was observed (F(4,201) = 0.72; p = .58). The least-squares mean difference from baseline in PRTEE scores at 6 months was 33.4 (CI 25.2 - 41.5) in the surgery group and 26.9 (CI 19.4 - 34.4) in the dry needling group (p = .25). The proportion of successful treatment was 83% (CI 63 - 95%) and 81% (CI 63 - 93%) in the surgery and dry needling groups, respectively (p = 1.00). Changes in secondary outcomes were in the same direction as those of the primary outcome. No adverse event occurred. CONCLUSIONS: Ultrasound-guided dry needling resulted in comparable improvement in outcome scores on scales of pain, physical function, and global assessment of change and satisfaction than open-release surgery. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02710682 KEY POINTS: • In patients with chronic lateral epicondylosis, ultrasound-guided tendon dry needling provides comparable therapeutic efficacy to open-release surgery. • Ultrasound-guided tendon dry needling allows for an earlier return to work and may be less costly than open-release surgery. • Care management guidelines should recommend treatment by ultrasound-guided tendon dry needling before open-release surgery.

Morphologic and radiologic parameters correlating to shoulder function at diagnosis for patients with rotator cuff tear.

BACKGROUND: The magnetic resonance imaging (MRI) parameters used to diagnose rotator cuff tears are weakly correlated to shoulder function. Our hypothesis was that adding 3-dimensional morphologic parameters resulting from biplanar radiographs (3DXR parameters) to the MRI parameters would improve this correlation. METHODS: We assessed 52 patients with rotator cuff tears with an EOS Imaging radiographic examination, MRI study, and clinical evaluation of the shoulder, as well as the Constant score. The bones of the 52 shoulders were reconstructed 3-dimensionally, and eleven 3DXR parameters were automatically extracted. First, the trueness and reliability of these parameters were evaluated. Then, bivariate correlations between each parameter and the Constant score were made. A linear regression model was subsequently built to correlate the 11 parameters and 5 MRI findings with shoulder function at diagnosis, as assessed by the Constant score. RESULTS: The parameters showed good trueness and reliability of most 3DXR parameters. Supraspinatus tear extension, muscle atrophy, and the distance between the greater and deltoid tuberosities were the only parameters with a statistically significant correlation to a lower Constant score (P < .05) in the bivariate study. These correlations were either weak or negligible. A regression model was successfully built with one MRI parameter and four 3DXR parameters. Correlation to function increased from 16.7% to 43.3% with this model. CONCLUSION: For patients with rotator cuff tears, the combination of MRI and 3DXR parameters of the shoulder in a linear regression model improves the correlation with the Constant score (shoulder function) at diagnosis.

Ultrasound-guided tendon fenestration versus open-release surgery for the treatment of chronic lateral epicondylosis of the elbow: protocol for a prospective, randomised, single blinded study.

INTRODUCTION: Chronic lateral epicondylosis (CLE) of the elbow is a prevalent condition among middle-aged people with no consensus on optimal care management but for which surgery is generally accepted as a second intention treatment. Among conservative treatment options, ultrasound (US)-guided fenestration has shown encouraging results that should be explored before surgery is considered. The primary objective of this study is to compare the efficacy of US-guided fenestration with open-release surgery in patients with failure to improve following a minimum 6 months of conservative treatment. METHODS AND ANALYSIS: This study protocol entails a two-arm, single-blinded, randomised, controlled design. Sixty-four eligible patients with clinically confirmed CLE will be assigned to either US-guided fenestration or open-release surgery. Fisher's exact test will be used to compare the proportion of patients reporting a change of 11/100 points or more in the Patient Rated Tennis Elbow Evaluation score at 6 months, according to an intention-to-treat analysis. Secondary analyses will compare the two treatment groups in terms of pain and disability, functional limitations at work, pain-free grip strength, medication burden, patients' global impression of change and level of satisfaction at 6 weeks, 3, 6 and 12 months, using mixed linear models for repeated measures or Fisher's exact test, as appropriate. Finally, recursive partitioning analyses will investigate US and elastography parameters as predictors of treatment success at 6 and 12 months. This data will contribute to evidence-based treatment guidelines for CLE and explore the value of imaging biomarkers to improve risk stratification plans and assist clinicians. ETHICS AND DISSEMINATION: The study has been approved by the Research Ethics Board of our institution on 23 March 2016 (REB 15.327). In case of important protocol modifications, a new version of the protocol with appropriate amendments will be submitted to the REB for approval. Study results will be published in peer-reviewed journals and presented at local, national and international conferences. TRIAL REGISTRATION NUMBER: NCT02710682.

Rotator Cuff Tear Morphologic Parameters at Magnetic Resonance Imaging: Relationship With Muscle Atrophy and Fatty Infiltration and Patient-Reported Function and Health-Related Quality of Life.

OBJECTIVE: The aim of this study was to determine the relationship between rotator cuff tear (RCT) morphologic parameters and muscle atrophy and fatty infiltration, and patient-reported outcome measures, in patients with symptomatic full-thickness RCT. METHODS: Rotator cuff tear location, length, width, thickness, and musculotendinous junction position were assessed in 57 magnetic resonance imaging scans and correlated to the outcome measures using multivariate regression analysis. RESULTS: Supraspinatus tendon tear length (odds ratio [OR], 2.218; 95% confidence interval [CI], 1.460-3.370), supraspinatus musculotendinous junction position (OR, 2.037; 95% CI, 1.322-3.137), and infraspinatus tendon tear width (OR, 2.371; 95% CI, 1.218-4.615) were identified as the strongest determinants of supraspinatus muscle atrophy, supraspinatus muscle fatty infiltration, and infraspinatus muscle fatty infiltration, respectively. CONCLUSIONS: The extent of supraspinatus tendon and musculotendinous junction retraction influences the development of supraspinatus muscle atrophy and fatty infiltration, whereas the extent of infraspinatus tendon tear width influences the development of infraspinatus muscle fatty infiltration. Morphologic parameters defining RCT at magnetic resonance imaging did not correlate with clinical shoulder function scores.

Effects of Prosthetic Mismatch and Subscapularis Tear on Glenohumeral Contact Patterns in Total Shoulder Arthroplasty: A Numerical Musculoskeletal Analysis.

Prosthetic components' mismatch and subscapularis (SC) tear are determining factors for glenoid failure complication in nonconforming total shoulder arthroplasty (NC-TSA). Risk factors are linked to glenoid prosthetic loading. However, the mechanisms underlying the clinical observations remain unclear. This study assessed the combined impact of mismatch and subscapularis tear on glenoid loading. It was assumed that adequate glenoid loading was associated with minimal, but non-null, humeral head translations and contact pressure, as well as with maximal glenoid contact area, and that the center of pressure (COP) on the glenoid would have a centered displacement pattern. A numerical model was used to achieve two objectives. The first was to verify whether an optimum mismatch existed, for which failure risk would be minimal. The second was to explore the effect of subscapularis tear on the position of applied forces on the glenoid. A shoulder AnyBody musculoskeletal model was adapted to the arthroplasty context by introducing humeral head translations and contact between implants. Ten simulations were computed to compare combinations of varying mismatches (1.4 mm, 3.4 mm, 6.4 mm, 8.6 mm, and 9 mm) with two shoulder conditions (intact-muscle or subscapularis tear). Humeral head translations, center-of-pressure, contact area, contact pressure, and glenohumeral joint contact forces were numerically estimated. Mismatches between 3.4 mm and 6.4 mm were associated with the most minimal humeral translations and contact pressure, as well as with maximal contact area. Center of pressure displacement pattern differed according to shoulder condition, with an outward anterior tendency in presence of tear.

Sonographic Visualization of the Rotator Cable in Patients With Symptomatic Full-Thickness Rotator Cuff Tears: Correlation With Tear Size, Muscular Fatty Infiltration and Atrophy, and Functional Outcome.

OBJECTIVES: To assess the prevalence of sonographic visualization of the rotator cable in patients with symptomatic full-thickness rotator cuff tears and asymptomatic controls and to correlate rotator cable visualization with tear size, muscular fatty infiltration and atrophy, and the functional outcome in the patients with rotator cuff tears. METHODS: Fifty-seven patients with rotator cuff tears and 30 asymptomatic volunteers underwent shoulder sonography for prospective assessment of the rotator cable and rotator cuff tear and responded to 2 functional outcome questionnaires (shortened Disabilities of the Arm, Shoulder, and Hand [QuickDASH] and Constant). In the patients with rotator cuff tears, appropriate tests were used to correlate rotator cable visualization with the tear size, functional outcome, muscular fatty infiltration, and atrophy. RESULTS: The patients with rotator cuff tears included 25 women and 32 men (mean age,57 years; range, 39-67 years), and the volunteers included 13 women and 17 men (mean age, 56 years; range, 35-64 years). The rotator cable was identified in 77% (23 of 30) of controls and 23% (13 of 57) of patients with rotator cuff tears. In the patients, nonvisualization of the rotator cable correlated with larger tears (P < 0.001) and higher grades of supraspinatus atrophy (P = .049) and fatty infiltration (P = .022). There was no significant correlation with functional outcome scores (QuickDASH, P = .989; Constant, P = .073) or infraspinatus fatty infiltration (P = .065). CONCLUSIONS: Nonvisualization of the rotator cable was more prevalent in patients with symptomatic rotator cuff tears than asymptomatic controls and was associated with a larger tear size and greater supraspinatus fatty infiltration and atrophy. Diligent assessment of the supraspinatus muscle should be done in patients with rotator cuff tears without a visible rotator cable, as the integrity of these anatomic structures may be interdependent.

Scapulohumeral rhythm relative to active range of motion in patients with symptomatic rotator cuff tears.

BACKGROUND: Some patients with rotator cuff tears feel pain without functional limitation, whereas others show a decrease in range of motion. To investigate this distinction, the scapulohumeral rhythm was used to conduct a functional evaluation of shoulder joints' coordination. The objective was to characterize patients according to their active range of motion without pain and their scapulohumeral rhythm compared with healthy individuals. MATERIALS AND METHODS: Fourteen patients with rotator cuff tears and 14 healthy individuals were set up with 35 reflective markers on the trunk and upper limb tracked by an optoelectronic system to measure the scapulohumeral rhythm. Five scapular plane maximal arm elevations were executed without pain. Patients were separated by maximal arm elevation of 85° (category A) and 40° (category B). Three-way mixed-design analysis of variance with factors of group (patients and healthy), arm elevation, and motion direction was applied to the scapulohumeral rhythm. RESULTS: A main effect of group (P = .032) was observed in patients in category A, who showed inferior scapulohumeral rhythm. An interaction between group and arm elevation (P = .044) was observed for patients in category B, where their scapulohumeral rhythm increased more during arm elevation than in the healthy individuals. CONCLUSIONS: Patients who reached at least 85° compensated for the loss of glenohumeral motion by increased scapulothoracic contribution, suggesting that structural damage interferes with motion mechanics. In contrast, patients who reached less range of motion underused the scapulothoracic joint, which is likely to create subacromial impingement at low arm elevation. A patient's maximal range of motion without pain may indicate a pattern of scapulohumeral rhythm alteration.

Investigation of 3D glenohumeral displacements from 3D reconstruction using biplane X-ray images: Accuracy and reproducibility of the technique and preliminary analysis in rotator cuff tear patients.

Rotator cuff (RC) tears may be associated with increased glenohumeral instability; however, this instability is difficult to quantify using currently available diagnostic tools. Recently, the three-dimensional (3D) reconstruction and registration method of the scapula and humeral head, based on sequences of low-dose biplane X-ray images, has been proposed for glenohumeral displacement assessment. This research aimed to evaluate the accuracy and reproducibility of this technique and to investigate its potential with a preliminary application comparing RC tear patients and asymptomatic volunteers. Accuracy was assessed using CT scan model registration on biplane X-ray images for five cadaveric shoulder specimens and showed differences ranging from 0.6 to 1.4mm depending on the direction of interest. Intra- and interobserver reproducibility was assessed through two operators who repeated the reconstruction of five subjects three times, allowing defining 95% confidence interval ranging from ±1.8 to ±3.6mm. Intraclass correlation coefficient varied between 0.84 and 0.98. Comparison between RC tear patients and asymptomatic volunteers showed differences of glenohumeral displacements, especially in the superoinferior direction when shoulder was abducted at 20° and 45°. This study thus assessed the accuracy of the low-dose 3D biplane X-ray reconstruction technique for glenohumeral displacement assessment and showed potential in biomechanical and clinical research.

The effects of plane and arc of elevation on electromyography of shoulder musculature in patients with rotator cuff tears.

BACKGROUND: Arm elevations in different planes are commonly assessed in clinics and are included in rehabilitation protocols for patients with rotator cuff pathology. The aim of this study was to quantify the effect of plane and angle of elevation on shoulder muscles activity in patients with symptomatic rotator cuff tear to be used for rehabilitation purposes. METHODS: Eight symptomatic patients with rotator cuff tears were assessed by using EMG (11 surface and 2 fine wire electrodes) synchronized with a motion analysis. The subjects completed five elevations in full can position (arm externally rotated and thumb up) in frontal, scapular and sagittal planes. Muscle activity in three elevation arcs of 20° (from 0° to 60°) was presented as the percentage of mean activity. Data were analyzed by mixed linear models (α=0.003), and Tuckey Post-hoc comparisons for significant effects (α=0.05). FINDINGS: The effect of plane was significant for supraspinatus, middle trapezius, anterior, middle, and posterior deltoid, triceps, and pectoralis major (P<0.001). Supraspinatus was more active during abduction than scaption and flexion (P<0.05), and its activity did not increase significantly after 40° of elevation (P>0.05). Infraspinatus had similar activity pattern in the three planes of elevation (P>0.003) with increasing trend in accordance with the elevation angle. INTERPRETATION: In any rehabilitation protocol, if less activity of supraspinatus is desired, active arm elevation should be directed toward flexion and scaption and postponed abduction to prevent high level of activity in this muscle.

Adaptation of the AnyBody™ Musculoskeletal Shoulder Model to the Nonconforming Total Shoulder Arthroplasty Context.

Current musculoskeletal inverse dynamics shoulder models have two limitations to use in the context of nonconforming total shoulder arthroplasty (NC-TSA). First, the ball and socket glenohumeral (GH) joint simplification avoids any humeral head translations. Second, there is no contact at the GH joint to compute the contact area and the center of pressure (COP) between the two components of NC-TSA. In this paper, we adapted the AnyBody™ shoulder model by introducing humeral head translations and contact between the two components of an NC-TSA. Abduction in the scapular plane was considered. The main objective of this study was to adapt the AnyBody™ shoulder model to a NC-TSA context and to compare the results of our model (translations, COP, contact area, GH joint reaction forces (GH-JRFs), and muscular forces) with previous numerical, experimental, and clinical studies. Humeral head translations and contact were successfully introduced in our adapted shoulder model with strong support for our findings by previous studies.

Electromyographic activity in the shoulder musculature during resistance training exercises of the ipsilateral upper limb while wearing a shoulder orthosis.

BACKGROUND: Resistance training is usually postponed until 3 months after rotator cuff surgery to prevent the damaging effects of high muscle stress on the repaired tendon. After upper limb immobilization, noninjured muscles as well as the repaired muscles are affected by long-term inactivity. Exercises with minimal cuff activity may be appropriate in the early postoperative period, so we aimed to quantify the effect of resistance exercises on the muscle activity of a semi-immobilized upper limb. METHOD: Fifteen shoulder muscles of the dominant limb of 14 healthy subjects were evaluated by electromyography, with 11 surface electrodes and 4 fine-wire electrodes in the rotator cuff muscles. While wearing an orthosis, the subjects completed resistance tests including elbow and wrist flexion/extension with 3 loads, maximal squeezing, and shoulder adduction against 3 different foams. The peak activity of each muscle was normalized to maximal voluntary contraction (% MVC). RESULTS: Shoulder muscles were activated less than 20% MVC during elbow and wrist flexion/extension with 2-lb (907-g) and 4-lb (1814-g) loads. In the maximal squeezing test, rotator cuff activity exceeded 20% MVC in some cases. During shoulder adduction tests, subscapularis, latissimus dorsi, triceps, and pectoralis major had the highest activation levels; supraspinatus and infraspinatus were minimally activated. CONCLUSION: Supported elbow and wrist flexion/extension in the horizontal plane, with weights of up to 4 lb (1814 g), minimally activates the rotator cuff muscles while potentially preventing muscle disuse of other upper limb musculature. Resisted shoulder adduction cannot be considered safe for all rotator cuff injuries. LEVEL OF EVIDENCE: Basic science study, electromyography

Electromyographic activity in the immobilized shoulder musculature during ipsilateral elbow, wrist, and finger movements while wearing a shoulder orthosis.

BACKGROUND: Shoulder immobilization after rotator cuff surgery is usually prescribed to protect the repaired tendons; however, shoulder orthoses often also immobilize the elbow and wrist joints. There is insufficient evidence to support that elbow and wrist movements can affect repair integrity by highly activating the rotator cuff muscles. The aim of this study was to quantify the electromyographic activity of immobilized shoulder muscles during elbow, wrist, and finger movements. METHODS: Fifteen shoulder muscles of the dominant limb of 14 healthy subjects were evaluated by use of electromyography with 11 surface electrodes and 4 fine-wire electrodes in the rotator cuff muscles. While wearing a custom orthosis, the subjects completed tests involving elbow, wrist, and finger movements of the ipsilateral limb. The peak activity of each muscle was normalized to maximum voluntary contraction (percent MVC) and averaged across the subjects. RESULTS: Rotator cuff muscles were activated to less than 10% MVC in both slow and fast elbow flexions. The mean peak activations of all muscles during wrist and finger movements were less than 5% MVC. In daily activities such as writing, typing, clicking a computer mouse, and holding a box or bag, rotator cuff muscle activity did not exceed 11% MVC, but sudden movements such as grasping a bottle could show higher levels of activity, which in some individuals exceeded 20% MVC. CONCLUSION: Elbow, wrist, and finger movements could minimally activate the rotator cuff muscles when the shoulder is immobilized with an orthosis.

Optimal shoulder immobilization postures following surgical repair of rotator cuff tears: a simulation analysis.

BACKGROUND: There is a high incidence of retear following surgical repair of rotator cuff tears. Postoperative shoulder immobilization is commonly prescribed to protect the repair; but there is no consensus on the best immobilization postures. METHODS: A generic musculoskeletal model of the shoulder was used to simulate postoperative immobilization of full thickness rotator cuff tears involving the supraspinatus only and the supraspinatus concomitantly with the infraspinatus or subscapularis. Optimal immobilization postures, which simultaneously minimized the stresses in the repaired tendons and the angle of humerus elevation, were obtained. RESULTS: For isolated supraspinatus tears, elevation of the humerus in planes close to the scapular plane was suggested. When the infraspinatus was also involved, planes posterior to the scapular plane were suggested; while, if the subscapularis was also involved, planes anterior to the scapular plane and internal rotation were suggested. The required thoracohumeral elevation angles ranged from 58° to 109°, depending on the tear length and the muscles involved. The optimal postures reduced the stresses in the repaired tendons by between 29% and 90%. CONCLUSION: Prescription of immobilization posture for a patient should be based on the conditions of the tear repaired. Appropriate choice of immobilization posture will reduce the stress in the repair, and as such has the potential to reduce retear rates.

Mechanical analysis of cuff tear arthropathy during multiplanar elevation with the AnyBody shoulder model.

BACKGROUND: This numerical study analysed the mechanics of cuff tear arthropathy with the AnyBody shoulder model. METHODS: The model simulated three frequent characteristics of cuff tear arthropathy: A supero-posterior massive rotator cuff tear, a proximal and static migration of the humeral head, and a contact between the humeral head and the scapula (glenoid & acromion) with friction. The mechanics of the cuff tear arthropathy with and without friction were studied by analysing: the mechanics of the deltoid (i.e. length & strength), the gleno-humeral and acromio-humeral contact forces, the friction moment, and the maximum elevation angle. Elevations in the frontal, scapular and sagittal planes were simulated. FINDINGS: Compared to an intact condition, the cuff tear arthropathy model without friction estimated a deltoid strength of -18% (frontal=-13%, scapular=-17%, sagittal=-25%), a gleno-humeral contact force of -34% (frontal=-60%, scapular=-46%, sagittal=+5%), estimated an acromio-humeral contact force of 240 N (frontal=213 N, scapular=184 N, sagittal=324 N) and a maximum elevation angle of 77° (frontal=80°, scapular=87°, sagittal=65°). Contact friction enhanced this behaviour, decreasing even more the gleno-humeral contact force and the maximum elevation angle, while increasing the acromio-humeral contact force. INTERPRETATION: This novel cuff tear arthropathy model suggests that friction and plane of elevation greatly influence the mechanics of the shoulder with cuff tear arthropathy. It also shows that the AnyBody simulation tool may be useful to study musculoskeletal pathologies and not only normal conditions.

Effect of glenoid implant design on glenohumeral stability: an experimental study.

BACKGROUND: Though several glenoid implants were developed over the past years, a high rate of glenoid loosening remains. This complication is linked to the glenohumeral stability, defined as humeral head translation. In an intact shoulder, this concept is ensured by all active and passive elements, particularly the labrum. Two features of a glenoid implant can be adjusted to improve the stability, or, in other words, to decrease the translations: the first is the mismatch, defined as the difference of curvature between the prosthetic head and glenoid; the second is the shape of the glenoid component. Therefore, the objective of this study was to compare the performance of 2 glenoid components (Ceraver, Roissy, France): (1) a standard design and (2) a design named "labrum design" with a superior part simulating the anatomic labrum. METHODS: An experimental device was developed to evaluate forces and kinematics. The device simulated active, dynamic and continuous abduction of an entire arm. It reproduced the Scapulo-Humeral Rhythm. The labrum design was installed first. To evaluate the effect of mismatch on the glenohumeral stability, 3 humeral heads were tested, corresponding to the ones recommended by the company. The experiment was repeated for the standard design. FINDINGS: The results obtained show a general decrease of the prosthetic head translation with the labrum design compared to the standard design. No noticeable effect of mismatch was found. INTERPRETATION: A proof of concept of the interest of the artificial labrum was provided since it improved the glenohumeral stability.

Analysis of humeral head displacements from sequences of biplanar X-rays: repeatability study and preliminary results in healthy subjects.

This work presents an accurate method to measure gleno-humeral translations in a controlled pseudo-kinematic environment. Low-dose biplanar X-rays were acquired from nine healthy subjects at three elevations of the arm in the scapular plane. On each set of images, shoulder bony landmarks were manually located in 3D using a dedicated software. Intra-observer and inter-observer repeatability of landmark identification, as well as humeral head center (GH) translations, were studied. Repeatability for the identification of GH in the global coordinate system (CS) was good with 95% confidence intervals (CIs) ranging from 0.57 to 2.25 mm. Scapular landmark CIs ranged from 0.80 to 12 mm. Gleno-humeral translations of small amplitude ( < 6 mm) were detected in seven out of nine subjects. The results obtained here confirm that calibrated low-dose stereo-radiography is a promising tool for the functional analysis of the shoulder.

Passive contribution of the rotator cuff to abduction and joint stability.

PURPOSE: The purpose of this study is to compare shoulder joint biomechanics during abduction with and without intact non-functioning rotator cuff tissue. METHODS: A cadaver model was devised to simulate the clinical findings seen in patients with a massive cuff tear. Eight full upper limb shoulder specimens were studied. Initially, the rotator cuff tendons were left intact, representing a non-functional rotator cuff, as seen in suprascapular nerve paralysis or in cuff repair with a patch. Subsequently, a massive rotator cuff tear was re-created. Three-dimensional kinematics and force requirements for shoulder abduction were analyzed for each condition using ten abduction cycles in the plane of the scapula. RESULTS: Mediolateral displacements of the glenohumeral rotation center (GHRC) during abduction with an intact non-functioning cuff were minimal, but massive cuff tear resulted in significant lateral displacement of the GHRC (p < 0.013). Similarly, massive cuff tear caused increased superior migration of the GHRC during abduction compared with intact non-functional cuff (p < 0.01). From 5 to 30° of abduction, force requirements were significantly less with an intact non-functioning cuff than with massive cuff tear (p < 0.009). CONCLUSION: During abduction, an intact but non-functioning rotator cuff resulted in decreased GHRC displacement in two axes as well as lowered the force requirement for abduction from 5 to 30° as compared with the results following a massive rotator cuff tear. This provides insight into the potential biomechanical effect of repairing massive rotator cuff tears with a biological or synthetic "patch," which is a new treatment for massive cuff tear.

Perioperative interscalene block versus intra-articular injection of local anesthetics for postoperative analgesia in shoulder surgery.

BACKGROUND AND OBJECTIVES: Up to 70% of patients report moderate to severe pain after shoulder surgery, which can compromise early rehabilitation and functional recuperation. Postoperative shoulder pain control is improved with both interscalene block and intra-articular local anesthetic injection. The present study hypothesized that perioperative interscalene analgesia would offer pain control superior to perioperative intra-articular local anesthetics over the first 24 hours after surgery. METHODS: Sixty patients undergoing shoulder surgery were randomly assigned to 1 of 2 groups: group IS had interscalene block with catheter installation, while group IA received intra-articular local anesthetic, also with catheter installation. All patients received 3 local anesthetic injections: 0.25 mL/kg of 2% lidocaine with epinephrine 2.5 microg/mL immediately before and after surgery, and 0.25 mL/kg of 0.5% bupivacaine with epinephrine 2.5 microg/mL 1 hour after the end of surgery, after which the catheters were removed, and no further local anesthetics were administered. Postoperative pain at rest was evaluated in the postanesthesia care unit (PACU), 3 hours, 6 hours and 24 hours after surgery. The area under the 24 hour pain over time curve was calculated. Hydromorphone consumption in the PACU and over 24 hours was recorded. RESULTS: Pain scores (IS: 0.4 +/- 2 vs. IA: 4 +/- 3, P < .0001) and opioid consumption (IS: 0.7 mg +/- 1.4 vs. IA: 1.5 mg +/- 1.2, P = .02) were significantly higher in the PACU for group IA. However, neither the mean pain scores over the first day after surgery (IS: 5 +/- 2 vs. IA: 5 +/- 3; P = .4) nor 24-hour opioid consumption (IS: 4.4 mg +/- 2.8 vs. IA: 4.2 mg +/- 2.6; P = .4) were significantly higher in group IA. CONCLUSIONS: PACU measurements of immediate postoperative pain and narcotic consumption favor perioperative interscalene analgesia over intra-articular analgesia. This benefit does not translate into lower overall pain for the first 24 hours after surgery.

The effect of axis alignment on shoulder joint kinematics analysis during arm abduction.

BACKGROUND: A joint coordinate system allows coherence between the performed movement, its mathematical representation and the clinical interpretation of the kinematics of joint motion. In 2005, the International Society of Biomechanics (ISB) defined a joint coordinate system for the shoulder. To improve kinematics interpretation, the ISB suggested aligning the coordinate systems of the humerus and the scapula. Therefore, the aim of this research project was to determine how the alignment of the joint coordinate system axes can influence the interpretation of shoulder joint kinematics. More precisely, we wanted to investigate if mathematical alignment of the reference and moving coordinate system axes could facilitate the kinematic interpretation of a simple abduction movement without introducing additional coupled motion. METHODS: An experiment was carried out on eight shoulder cadaveric specimens. Elevation of the arm in the scapular plane (abduction) was recorded using an electromagnetic tracking device. Three-dimensional angular displacements of the arm during elevation in the scapular plane were described using the standard ISB joint coordinate system, and using a modified joint coordinate system for which the axes were mathematically aligned. FINDINGS: The results obtained revealed a difference in the interpretation of the starting angles between the ISB joint coordinate system and the aligned coordinate system. No difference was found in the interpretation of the angular range of motion (P<0.01). INTERPRETATION: The aligned coordinate system provided a standardized starting angle of elevation that allows an easier clinical interpretation of shoulder kinematics.