Scapular Plane Research Articles

The biomechanical effect of injury and repair of the inferior glenohumeral ligament on glenohumeral stability: Contribution of the posterior band

BackgroundMany surgical procedures are proposed to manage shoulder instability with recurrent dislocation but there is still a high rate of failure or complications. Repairs are often limited to anterior part of inferior glenohumeral ligament but some authors are reporting better clinical results if its posterior band is also repaired. This biomechanical study aimed to investigate the impact of a supplementary posterior injury compared with an isolated anterior injury and to analyze the contribution of a posterior repair of the inferior glenohumeral ligament compared with an isolated anterior repair. MethodsSix fresh-frozen cadaveric shoulders were tested intact and after both anterior and posterior injuries and repairs of the inferior glenohumeral ligament. Shoulders were placed at 90° of humerothoracic elevation in scapular plane and 60° of external rotation. Joint stability was analyzed by successively applying anterior, posterior, inferior and superior glenohumeral displacements and measuring the resulting forces or by applying an anteroinferior loading and measuring three-dimensional head displacements. Maximal range of external rotation was also measured. FindingsCombined anterior and posterior injuries of the inferior glenohumeral ligament were necessary to obtain significant instabilities in anterior and inferior directions. A complementary repair of the posterior band improved the biomechanical stability of the glenohumeral joint compared to an isolated anterior repair when anterior and posterior bands are injured. No reduction of external rotation was observed after repairs compared to intact condition. InterpretationThese results show the biomechanical interest of this surgical procedure and contribute to document its relevance in clinical practice.

Time-course changes in active stiffness of the supraspinatus muscle after arthroscopic rotator cuff repair.

This study aimed to investigate the time-course changes in the active stiffness of the supraspinatus muscle after arthroscopic rotator cuff repair. Eight male patients (mean age 61.5 ± 9.4years) who underwent arthroscopic rotator cuff repair for small to medium tears were recruited for this study. Movement tasks included 30° shoulder isometric abduction and maximal voluntary isometric contraction of shoulder abduction in the scapular plane. The stiffness of the supraspinatus (anterior superficial, anterior deep, posterior superficial, and posterior deep regions), upper trapezius, and middle deltoid muscles in bilateral shoulders was recorded using ultrasound shear wave elastography. For each subject, the measurement was performed preoperatively and 3, 6, and 12months postoperatively. The stiffness of the affected anterior superficial region of the supraspinatus muscle 12months postoperatively was significantly higher than that measured preoperatively and 3months postoperatively (p < 0.05); it was significantly higher at 6months postoperatively than at 3months postoperatively (p < 0.05). Further, the maximal voluntary isometric contraction had significantly improved 12months postoperatively compared to that measured preoperatively and 3months postoperatively (p < 0.05). The stiffness of the affected upper trapezius and middle deltoid muscles 12months postoperatively was significantly lower than that preoperatively (p < 0.05). The maximal voluntary isometric contraction 12months postoperatively possibly increased because of improvement in the active stiffness of the anterior superficial region. Active stiffness of the anterior superficial region may improve 6months rather than 3months postoperatively because of the different stages of muscle force, structural repair tendon strength, and remodeling.

Human Dermal Allograft Superior Capsule Reconstruction With Graft Length Determined at Glenohumeral Abduction Angles of 20° and 40° Decreases Joint Translation and Subacromial Pressure Without Compromising Range of Motion: A Cadaveric Biomechanical Study

To compare the biomechanical effects of superior capsule reconstruction (SCR) graft fixation length determined at 20° and 40° of glenohumeral (GH) abduction. Humeral translation, rotational range of motion (ROM), and subacromial contact pressure were quantified at 0°, 30°, and 60° of GH abduction in the scapular plane in 6 cadaveric shoulders for the following states: intact, massive rotator cuff tear, SCR with dermal allograft fixed at 20° of GH abduction (SCR 20), and SCR with dermal allograft fixed at 40° of GH abduction (SCR 40). Statistical analysis was conducted using a repeated-measures analysis of variance and a paired t test (P < .05). A massive cuff tear significantly increased total ROM compared with the intact state at 0° and 60° of abduction. SCR 20 or SCR 40 did not affect ROM. Compared with the intact state, the massive cuff tear model significantly increased superior translation by an average of 4.6 ± 0.5 mm in 9 of 12 positions (P ≤ .002). Both SCR 20 and SCR 40 reduced superior translation compared with the massive cuff tear model (P < .05); however, SCR 40 significantly decreased superior translation compared with SCR 20 at 0° of abduction (P≤ .046). Peak subacromial pressure for the massive cuff tear model increased by an average of 486.8 ± 233.9 kPa relative to the intact state in 5 of 12 positions (P ≤ .037). SCR 20 reduced peak subacromial pressure in 2 of 12 positions (P ≤ .012), whereas SCR 40 achieved this in 6 of 12 positions (P ≤ .024). SCR with dermal allograft fixed at 20° or 40° of GH abduction decreases GH translation and subacromial pressure without decreasing ROM. With an increasing abduction angle for graft fixation, the medial-to-lateral graft length is decreased and the graft tension is effectively increased. Surgeons may increase shoulder stability without restricting ROM by fixing the graft at higher abduction angles. However, surgeons should remain cognizant of potential graft failure due to increased tension.

Changes in shoulder muscle activities and glenohumeral motion after rotator cuff repair: an assessment using ultrasound real-time tissue elastography.

Although rotator cuff repair is performed to restore the function of the rotator cuff muscles and glenohumeral (GH) joint motion, little has been known regarding the recovery process. The purpose of this study was (1) to investigate changes over time in activities of the supraspinatus and deltoid muscles assessed by ultrasound real-time tissue elastography (RTE) after rotator cuff repair and (2) to determine contributions of the activities of these muscles to the GH joint motion. Twenty patients after rotator cuff repair and 13 control participants were enrolled in this study. Elasticity of the supraspinatus and middle deltoid muscles were measured at rest and 30° of humerothoracic elevation in the scapular plane (scaption) by using RTE. The elasticity at 30° of scaption was normalized to that at rest in each muscle to quantify their muscle activities. In addition, the supraspinatus-to-middle deltoid (SSP/MD) ratio for the normalized elasticity was calculated. The GH elevation angle was measured with a digital inclinometer, which was calculated by subtracting the scapular upward rotation angle from 30° of scaption. For patients after rotator cuff repair, all measurements were performed at 6 weeks, 8 weeks, 3 months, and 6 months after surgery. Rotator cuff integrity was examined with magnetic resonance imaging at 6 months after surgery. Fifteen of 20 patients who remained intact at 6 months after surgery completed this study. The supraspinatus activity at 6 weeks was significantly smaller than that at 3 months (P = .006) and 6 months (P = .010). There was no significant difference in the supraspinatus activity between the patients at 3 months and the control participants (P = .586). The middle deltoid activity at 6 weeks was significantly greater than that at 6 months (P = .003). There was positive correlation between GH elevation angle and the activity of the supraspinatus relative to the deltoid at 6 weeks (r = 0.75, P = .001) and 8 weeks (r = 0.53, P = .041). The supraspinatus activity increased from 6 weeks to 3 months after surgery. The supraspinatus activity at 3 months after surgery was the same level as that in healthy individuals. On the other hand, the deltoid activity decreased from 6 weeks to 6 months after surgery. The increase in activity of the supraspinatus relative to the deltoid was likely to be related to the increase in GH elevation during postoperative at 8 weeks.

Muscle Activity Before and After Subacromial Injection.

Shoulder muscle activation in patients with subacromial impingement is highly cited and variable in the literature. Differences between studies could be due to artifacts introduced by normalization practices in the presence of pain. Ultimately, this lack of knowledge pertaining to pathogenesis limits the clinical treatment and restoration of muscular function. A total of 21 patients with stage 2 subacromial impingement and 21 matched controls were recruited for EMG testing of their affected shoulder during an arm elevation task. The patients were tested before and after receiving an injection to their subacromial bursa. The EMG from 7 shoulder muscles were measured before and after treatment during humeral motion in the scapular plane. Our findings indicate an increase in anterior deltoid, middle deltoid, and upper trapezius activity following the injection; further, this trend extended to the controls. The control subjects had a greater activation of the latissimus dorsi at peak arm elevation when compared with the patient group postinjection. Our results indicate that a reduction in subacromial pain is associated with changes in shoulder muscle recruitment, primarily of the deltoid. This change in deltoid activity may lend evidence to rotator cuff function in patients without rotator cuff tears.

Effects of shoulder abduction on the stiffness of supraspinatus muscle regions in rotator cuff tear.

This study aimed to compare the effect of the load of the upper limb on the stiffness of supraspinatus muscle regions during isometric shoulder abduction in the scapular plane in healthy individuals and patients with a rotator cuff tear. Thirteen male patients were scheduled for arthroscopic rotator cuff repair, and 13 healthy male individuals were recruited. The movement task involved 30° isometric shoulder abduction in the scapular plane. The tasks included passive abduction, abduction with half‐weight of the upper limb (1/2‐weight), and full weight of the upper limb (full‐weight). The stiffness of the supraspinatus muscle (anterior superficial, anterior deep, posterior superficial, and posterior deep regions) was recorded using ultrasound shear‐wave elastography. The stiffness of the anterior superficial region on the affected side was significantly lower than that on the control side for the 1/2‐weight and full‐weight tasks. The stiffness of the anterior deep, posterior superficial, and posterior deep regions was not affected. This is the first study that investigated the mechanical effects of different loads on different supraspinatus muscle regions in rotator cuff tear patients. Our results indicate that the anterior superficial region in rotator cuff tear patients was mainly responsible for reduced active stiffness. This might be because this region contributes to force exertion and exhibits atrophy in rotator cuff tears. Hence, the anterior superficial region could be a focal point of quantitative dysfunction evaluation of the supraspinatus muscle in the case of a rotator cuff tear.

A Matlab toolbox for scaled-generic modeling of shoulder and elbow

There still remains a barrier ahead of widespread clinical applications of upper extremity musculoskeletal models. This study is a step toward lifting this barrier for a shoulder musculoskeletal model by enhancing its realism and facilitating its applications. To this end, two main improvements are considered. First, the elbow and the muscle groups spanning the elbow are included in the model. Second, scaling routines are developed that scale model’s bone segment inertial properties, skeletal morphologies, and muscles architectures according to a specific subject. The model is also presented as a Matlab toolbox with a graphical user interface to exempt its users from further programming. We evaluated effects of anthropometric parameters, including subject’s gender, height, weight, glenoid inclination, and degenerations of rotator cuff muscles on the glenohumeral joint reaction force (JRF) predictions. An arm abduction motion in the scapula plane is simulated while each of the parameters is independently varied. The results indeed illustrate the effect of anthropometric parameters and provide JRF predictions with less than 13% difference compared to in vivo studies. The developed Matlab toolbox could be populated with pre/post operative patients of total shoulder arthroplasty to answer clinical questions regarding treatments of glenohumeral joint osteoarthritis.

Elasticity of baseball players’ posterior shoulder capsule during internal rotation stretching at 30 degrees of scaption

Previous cadaveric studies have identified effective stretching positions for the posterior shoulder capsules; however, it is unknown whether these stretching positions are also effective in overhead athletes. This study aimed to investigate whether passive tension was generated in the posterior shoulder capsules in baseball players during stretching positions identified in previous cadaveric studies. Fifteen male baseball players without prior shoulder injuries or surgeries participated in this study. We measured the shear moduli of the middle and inferior posterior capsules of the dominant shoulder in the resting (neutral shoulder internal/external rotation at 30 degrees of flexion) and stretching (maximal shoulder internal rotation at 30 degrees of scapular plane elevation (scaption)) positions using ultrasound shear wave elastography. The shear moduli of the middle posterior capsule were significantly higher in the stretching position than in the resting position (resting vs stretching: 20.9 vs 34.6 kPa, P < .001); however, there was no significant difference in the shear moduli between both positions in the inferior posterior capsule (22.3 vs 29.5 kPa, P = .120). Our results revealed that a large amount of passive tension is generated in the middle posterior capsule during shoulder internal rotation stretching at 30 degrees of scaption in overhead athletes.

The effects of muscle fatigue on scapulothoracic joint position sense and neuromuscular performance

BackgroundFatigue of the scapular musculature might affect the sensorimotor system and neuromuscular control and therefore impair the dynamic alignment of the scapula. The purpose of this study was to investigate the effects of scapular muscle fatigue on joint position sense and the neuromuscular performance of the scapulothoracic joint. MethodsThirty healthy subjects were recruited. The joint position sense (measured as reposition errors during the scapular elevation and protraction task) of the scapulothoracic joint and scapular kinematics and muscle activation (% of maximum voluntary isometric contraction) during scaption, shoulder elevation in the scapular plane, before and after the fatigue task (modified push-up) were measured. The repeated measures analysis of variance (ANOVA) was used to assess the effects of fatigue on scapular reposition error and neuromuscular control. ResultsAlthough joint reposition sense did not change after fatigue, muscle activation of the serratus anterior increased significantly (18.5%–26.3%, p = 0.006, elevation task; 15.2%–27.4%, p = 0.037, protraction task). At 120° scaption, the scapula showed a decreased posterior tilt (13.8°–10.3°, p < 0.001), increased protraction (10.2°–13.3°, p = 0.004) and lateral rotation (52.8°–54.4°, p = 0.005). Muscle activation of the serratus anterior increased (65.9%–84.6%, p = 0.002) during 90°–120°scaption. ConclusionScapular muscle fatigue did not alter the scapulothoracic joint position sense, but increased serratus anterior activation and resulted in a more anteriorly tilted, protracted, and laterally rotated scapula during scaption. Whether or not these fatigue-related changes are linked to the development of shoulder problems needs to be investigated further.

Comparing invivo three-dimensional shoulder elevation kinematics between standing and supine postures.

BackgroundIt is often assumed that body posture, standing vs. supine, changes shoulder muscle activation and range of motion, but these altered shoulder mechanics have not been objectively assessed. We expected the supine posture might facilitate scapular rotation and change subacromial pressure. The purpose of this study is to evaluate the influence of body posture on shoulder kinematics during arm elevation.MethodsTen males and eight females with a mean age of 33 years participated in this study. Shoulder kinematics were assessed during scapular plane elevation in the standing and supine postures by using single-plane fluoroscopic images. Kinematics were measured using 3-dimensional to 2-dimensional model-image registration techniques: matching the 3-dimensional bone model derived from computed tomography onto each fluoroscopic image. Glenohumeral superior/inferior translation, acromiohumeral distance, and scapular rotations were compared between the postures. The effect of sex also was evaluated.ResultsWith the arm at the side position, the humeral head in the supine posture was located 0.5 mm superior compared to the standing posture (P < .001). During humeral elevation, the humeral head significantly shifted more inferiorly in the supine posture than in standing; the biggest mean difference was 0.6 mm, P = .003. But acromiohumeral distance during elevation was not significantly affected by the body posture (P = .05). Scapular upward rotation and posterior tilt were significantly different between the postures (P < .001). Sex had statistically significant, but quantitatively small, effects on shoulder kinematics.ConclusionsBody postures affect shoulder kinematics during humeral elevation. This knowledge will be useful to optimize rehabilitation exercises and for diagnostic insight.

Pseudoparalysis and pseudoparesis of the shoulder

Abstract 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 &lt;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 (&gt;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 (&lt;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.

Skin Strain Analysis of the Scapular Region and Wearables Design.

Monitoring scapular movements is of relevance in the contexts of rehabilitation and clinical research. Among many technologies, wearable systems instrumented by strain sensors are emerging in these applications. An open challenge for the design of these systems is the optimal positioning of the sensing elements, since their response is related to the strain of the underlying substrates. This study aimed to provide a method to analyze the human skin strain of the scapular region. Experiments were conducted on five healthy volunteers to assess the skin strain during upper limb movements in the frontal, sagittal, and scapular planes at different degrees of elevation. A 6 × 5 grid of passive markers was placed posteriorly to cover the entire anatomic region of interest. Results showed that the maximum strain values, in percentage, were 28.26%, and 52.95%, 60.12% and 60.87%, 40.89%, and 48.20%, for elevation up to 90° and maximum elevation in the frontal, sagittal, and scapular planes, respectively. In all cases, the maximum extension is referred to the pair of markers placed horizontally near the axillary fold. Accordingly, this study suggests interesting insights for designing and positioning textile-based strain sensors in wearable systems for scapular movements monitoring.

The effectiveness of EMG-driven neuromusculoskeletal model calibration is task dependent

Calibration of neuromusculoskeletal models using functional tasks is performed to calculate subject-specific musculotendon parameters, as well as coefficients describing the shape of muscle excitation and activation functions. The objective of the present study was to employ a neuromusculoskeletal model of the shoulder driven entirely from muscle electromyography (EMG) to quantify the influence of different model calibration strategies on muscle and joint force predictions. Three healthy adults performed dynamic shoulder abduction and flexion, followed by calibration tasks that included reaching, head touching as well as active and passive abduction, flexion and axial rotation, and submaximal isometric abduction, flexion and axial rotation contractions. EMG data were simultaneously measured from 16 shoulder muscles using surface and intramuscular electrodes, and joint motion evaluated using video motion analysis. Muscle and joint forces were calculated using subject-specific EMG-driven neuromusculoskeletal models that were uncalibrated and calibrated using (i) all calibration tasks (ii) sagittal plane calibration tasks, and (iii) scapular plane calibration tasks. Joint forces were compared to published instrumented implant data. Calibrating models across all tasks resulted in glenohumeral joint force magnitudes that were more similar to instrumented implant data than those derived from any other model calibration strategy. Muscles that generated greater torque were more sensitive to calibration than those that contributed less. This study demonstrates that extensive model calibration over a broad range of contrasting tasks produces the most accurate and physiologically relevant musculotendon and EMG-to-activation parameters. This study will assist in development and deployment of subject-specific neuromusculoskeletal models.

Comparison of two-dimensional manual and three-dimensional SurgiCase and BLUEPRINT planning software measurements of glenoid version, inclination, and humeral subluxation

IntroductionVirtual planning for shoulder arthroplasty using preoperative computed tomography (CT) has been gaining popularity, and it is imperative for surgeons to recognize any differences in measurements that may exist amongst software platforms. The purpose of this study is to compare measurements of glenoid version, inclination, and humeral head subluxation between a manual approach and two varying automated software platforms using either a best-fit sphere technique (Wright-Medical BLUEPRINT) or an anatomic landmarks technique (Materalise SurgiCase). MethodsA case control study of 289 CT images from patients preoperatively planned for a total shoulder arthroplasty or reverse shoulder arthroplasty using SurgiCase (v3.0.110.5) were also successfully analyzed by BLUEPRINT (v2.1.6). Glenoid version, inclination, and subluxation were measured manually in a blind fashion by two separate investigators using axial and coronal images oriented to the scapular plane; interobserver and intraobserver reliabilities were measured using intraclass correlation coefficients (ICCs). Concordance correlation coefficients (CCCs), mean differences, and clinically relevant agreement in measurements between the software platforms and with the manual technique were compared. The impact of greater glenoid retroversion on the differences in measurements between the software platforms was further studied by correlation analysis. ResultsThe mean differences between SurgiCase and BLUEPRINT were + 0.5° for glenoid inclination (P = .064; CCC = 0.84), -0.9° for glenoid version (P < .001; CCC = 0.92), and -1.4% for humeral subluxation (P = .002; CCC = 0.88). Agreement within 5 units was 78.9% for inclination, 89.3% for version, and 64.1% for subluxation. Glenoid retroversion had no relation with the degree of variation in measured inclination (P = .59) or version (P = .56). There were significant differences between manual and 3D software measurements for glenoid inclination, version, and subluxation (P < .001). Both software measurements were more inferiorly inclined (average difference, SurgiCase -3.2° and BLUEPRINT -3.9°), more retroverted (average difference, SurgiCase -4.0° and BLUEPRINT -3.2°), and more posteriorly subluxated (average difference, SurgiCase + 3.4% and BLUEPRINT + 4.8%). ConclusionThe SurgiCase and BLUEPRINT preoperative planning software yield clinically similar measurements for glenoid version, inclination, and subluxation. The degree of glenoid retroversion does not impact the variability of inclination or version between the landmark and best-fit sphere software techniques. Compared to the 2D manual technique, both 3D software programs reported greater inferior inclination, retroversion, and posterior subluxation. Level of evidenceLevel III; Retrospective Diagnostic Study

Motor Control Evaluation as a Significant Component in Upper Limb Function Assessment in Female Breast Cancer Patients after Mastectomy.

Breast cancer is the most prevalent malignancy among women. Conservative and operative treatment methods are associated with a risk of side effects pertaining to the shoulder complex. The surgery complications including chronic pain, upper limb and chest lymphedema, range of motion limitations, and motor control deficiencies may lead to upper limb function impairment and affect the quality of life negatively. Twenty-three women were examined in the tested group and twenty-two women in the control group. The motor control was assessed with dissociation tests as defined by Comerford and Mottram. In order to assess patient-perceived upper limb disability, the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire was used. The test of glenohumeral (GH) abduction control in frontal plane and in scapular plane and medial rotation control outcomes were found to be statistically significant. It pertains to both: Comparison between groups and analysis within the tested group—body sides comparison. The DASH questionnaire results analysis indicates that there was a higher degree of subjectively perceived disability of upper limb in the tested group. Surgical interventions in the breast cancer treatment and other medical procedures affect the level of motor control and perceived disability of upper limb negatively in this group of patients. Movement faults are statistically more prevalent in the tested group. Movement faults are more prevalent on the operated side in the tested group.

Effects of Internal Fixation for Mid-Shaft Clavicle Fractures on Shoulder Kinematics During Humeral Elevations.

BackgroundMid-shaft clavicle fractures account for 35 to 44% of injuries to the shoulder girdle. There is increasing evidence to support surgical repair, but poor functional outcomes have been reported, and associated factors remain unclear.MethodsThe three-dimensional poses of the shoulder bones during arm elevations were measured in 15 patients treated for mid-shaft clavicle fractures by open reduction and internal fixation, and in 15 healthy controls.Results and ConclusionNo significant between-side differences were found in the clavicle length after surgery (p > 0.05). The patients showed increased scapular protraction at lower elevation angles and reduced scapular retraction at higher elevation angles during frontal-plane elevations, with significantly reduced clavicle retraction (p < 0.05), with unaltered scapular rotation and tilt. The ranges of the observed changes were reduced to arm elevations at 60° and 90° in the scapular and sagittal planes. Similar changes were also found on the unaffected side, suggesting symmetrical bilateral compensation. The results suggest that shoulder kinematics in multi-plane arm elevations should be monitored for any signs of compromised bone motions following surgical treatment, and that rehabilitative training may be needed on both sides to improve the bilateral movement control of the shoulder complex.

Improved Outcomes Following Arthroscopic Superior Capsular Reconstruction May Not Be Associated With Changes in Shoulder Kinematics: An In Vivo Study

To determine the invivo effects of superior capsule reconstruction (SCR) on glenohumeral kinematics during abduction and to compare those kinematics results with patient-reported outcomes, range of motion, and strength. Dynamic biplane radiography was used to image 10 patients with irreparable rotator cuff tears while performing scapular plane abduction pre- and 1-year post-surgery. Shoulder kinematics were determined by matching subject-specific computed tomography-based bone models to the radiographs using a validated tracking technique. No change was detected in static acromiohumeral distance (-0.7 ± 2.1 mm; P= .35); however, average dynamic acromiohumeral distance decreased (2.7 ± 1.2 mm to 2.3 ± 1.0 mm; P= .035) from pre- to 1-year post-surgery, respectively. The humeral head position was 0.5 ± 0.5 mm more superior 1-year post-surgery compared with pre-surgery (P= .01). Glenohumeral abduction increased from pre-surgery (150 ± 20°) to 1-year post-surgery (165 ± 10°) (P= .04) and all patient-reported outcomes improved from pre-surgery to 1-year post-surgery (all P < .002). A more posterior shift in humeral head position was associated with improved American Shoulder and Elbow Surgeons Shoulder Score from pre-surgery to 1-year post-surgery (r= 0.71, P= .02). These data suggest that SCR may not depress the humeral head during functional abduction, as previously postulated, and postoperative improvements in subjective and clinical outcomes may be affected by mechanisms other than changes in shoulder kinematics. Invivo kinematics changes after SCR are small and do not correspond to previously postulated changes.

Motion, and Patient-Reported Outcomes

Objectives:Patients with irreparable rotator cuff tears (RCT) exhibit functional limitations believed to be caused by superior migration of the humerus1,2. One viable treatment is superior capsule reconstruction (SCR). SCR has been shown to restore stability of the glenohumeral (GH) joint in cadavers1, but its effectiveness at controlling in vivo humeral motion is unknown. Outcomes are typically evaluated through standard clinical radiographs to assess acromial-humeral distance (AHD), and patient-reported outcomes (PROs) such as ASES and Visual Analog Scale3. Reported changes in AHD are inconsistent, with some studies reporting an increase in AHD of 2.6 to 3.2 mm4,5, while other studies reported no significant change in AHD after SCR6,7. Additionally, AHD does not account for anterior-posterior translations of the humeral head and clinical radiographs cannot assess dynamic translation of the humerus during arm abduction. The aim of this study was to determine the in vivo effect of SCR on in vivo glenohumeral arthrokinematics during scapular abduction, and to compare these results to PROs. We hypothesized that static and dynamic AHD would increase, humeral head location on the glenoid would be more inferior at corresponding abduction angles after SCR, and changes in humeral head translation or AHD would correlate with increased GH abduction range of motion and improved PROs.Methods:Ten patients (8M, 2F, age 63 ± 7 years) with irreparable RCT provided informed consent to participate in this prospective IRB-approved study. ASES, DASH, and WORC surveys were completed before (PRE) and 1-year (1YR-POST) after SCR. Synchronized biplane radiographs of the shoulder were collected PRE and 1YR-POST at 50 images/s while patients performed 3 trials of scapular plane arm abduction. Biplane radiographs were also collected during a static neutral trial where the participants placed their hand on their lap. Six degree of freedom GH and scapular kinematics were determined with sub-millimeter accuracy by matching subject-specific CT-based bone models of the humerus and scapula to radiographs using a validated volumetric tracking technique8. AHD was calculated as the minimum distance between the acromion and the humerus at 10° increments of GH abduction and averaged throughout the motion. Humeral head translation, defined as the relative translation of the center of the humeral head compared to the center of the glenoid, was calculated at 10° increments of GH abduction and expressed as averages in the superior/inferior (SI) and anterior/posterior (AP) directions. Differences between PRE and 1YR-POST static AHD, average dynamic humeral head location, PROs, and maximum GH abduction were evaluated using a paired t-test. A Pearson correlation was used to determine associations between static AHD and average humeral head location, and both PROs and maximum GH abduction. Significance was set at p < 0.05 for all tests.Results:There was no difference in static AHD from PRE (5.3±1.6mm) to 1YR-POST (4.6±1.6mm) while the average dynamic AHD during GH abduction decreased from 2.7±1.2mm PRE to 2.3±1.0mm 1YR-POST (Figure 1). Static AHD was larger than the average dynamic AHD both PRE and 1YR-POST (Figure 1). The average position of the humeral head during abduction moved 1.5% of the glenoid height superior from PRE to 1YR-POST and 1.7% of the glenoid width anterior from PRE to 1YR-POST (Figure 2). ASES, WORC, and DASH scores significantly improved from PRE to 1YR-POST and maximum GH abduction significantly increased from PRE (78.1±23.1°) to 1YR-POST (93.9±12.3°) (Table 1). Interestingly, there was a positive correlation between the AP humeral head location and DASH score PRE such that a higher DASH score was associated with the humeral head being more anterior (R = 0.767). No other associations were found between either average humeral head locations or AHD and either PROs or maximum GH abduction at both time points as well as the changes in those measures between time points (all R < 0.67).Conclusions:Static AHD, as measured clinically, may not be a good representation of dynamic AHD during scapular abduction given the differences between the static and dynamic AHD measurements at similar abduction angles. Additionally, our in vivo kinematics findings are not consistent with prior results of a cadaver-based biomechanical study of SCR as we found were minute changes in the SI humeral head position, with a 0.4mm more superior humeral head position following SCR. Regardless, patient-reported qualitative outcomes and maximum GH abduction all improved significantly. This suggests clinical outcomes after SCR may be influenced by mechanisms other than restoration of humeral head translation. Future in vivo studies are needed to evaluate the kinematic mechanisms behind improved PROs after SCR.

The Relationship between Scapular Upward Rotation and Shoulder Internal and External Rotation Isokinetic Strength in Professional Baseball Pitchers.

This study aims to assess the relationship between scapular upward rotation (SUR) across varying humeral-elevation angles (HEAs) and shoulder isokinetic strength and ratio in professional baseball pitchers. The subjects were professional baseball pitchers (n = 16) without a history of shoulder injury in the last six months. The subject’s SUR angles were measured with the humerus elevated at HEAs of 0° (at rest), 60°, 90°, and 120° to the scapular plane. Shoulder isokinetic strength was evaluated for shoulder internal rotation (IR) and external rotation (ER) strength (PT%BW and TW%BW), and the ER/IR strength ratios were determined at 60, 120 and 180°/s using an isokinetic dynamometer. The SUR angle at an HEA of 0° was positively correlated with IR strength at 120°/s (r = 0.535) and 180°/s (r = 0.522). The SUR angle at an HEA of 60° was negatively correlated with the ER/IR strength ratios at 60°/s (r = −0.505) and 120°/s (r = −0.500). The SUR angle at an HEA of 90° was negatively correlated with the ER/IR strength ratios at 60°/s (r = −0.574; r = −0.554) and 120°/s (r = −0.521; r = −0.589) as well as with ER strength at 180°/s (r = −0.591, r = −0.556). The SUR angle at an HEA of 120° was negatively correlated with ER strength at 60°/s (r = −0.558), 120°/s (r = −0.504; r = −0.524), and 180°/s (r = −0.543) and the ER/IR strength ratio at 60°/s (r = −0.517). In this study, we found that the ratio of isokinetic strength between ER and IR became closer to the normal range on increasing the SUR angle. In particular, an HEA of 90°, which resembles the pitching motion, showed a clear relationship between SUR, shoulder ER, and the ratio of ER/IR isokinetic strength in professional baseball pitchers.

Does fluoroscopy improve baseplate position compared to conventional technique in reverse shoulder arthroplasty? A preliminary study.

Accurate placement of glenoid component in reverse shoulder arthroplasty remains a challenge for surgeons of all levels of expertise; however, no studies have evaluated the utility of fluoroscopy as a surgical assistance method. Prospective comparative study of 33 patients undergoing primary reverse shoulder arthroplasty during a 12-month period. Fifteen patients had a baseplate placed using the conventional "free hand" technique (control group), and 18 patients using intraoperative fluoroscopy assistance group, in a case-control design. Postoperative glenoid position was evaluated on postoperative Computed Tomography (CT) scan. The mean deviation of version and inclination for fluoroscopy assistance vs. control group was 1.75° (0.675-3.125) vs. 4.2° (1.975-10.45) (p = .015), and 3.85° (0-7.225) vs. 10.35° (4.35-18.75) (p = .009). The distance from the central peg midpoint to the inferior glenoid rim (fluoroscopy assistance 14.61 mm/control 4.75 mm, p = .581) and the surgical time (fluoroscopy assistance 1.93 ± 0.57/control 2.18 ± 0.44 h, p = .400) showed no differences, with an average radiation dose of 0.45 mGy and fluoroscopy time of 14 s. Accurate axial and coronal scapular plane positioning of glenoid component is improved with intraoperative fluoroscopy at the cost of a greater radiation dose and without differences in surgical time. Comparative studies are needed to determine whether their use in relation to more expensive surgical assistance systems result in similar effectiveness.L evel of evidence : Level III, therapeutic study.