Stability Of Glenohumeral Joint Research Articles

A cadaveric study of the posterior band of the inferior glenohumeral ligament of the shoulder and its dynamic behaviour in different arm positions.

The inferior glenohumeral ligament (IGHL) is composed of three parts: the anterior branch or band (AB), the axillary pouch and the posterior band (PB). The latter has rarely been studied. We aim to describe the PB of the IGHL and its dynamic behaviour in different arm positions. Twelve fresh cadaveric shoulders were used and the two bands (AB and PB) of the IGHL were dissected and isolated, taking away all muscle, ligaments and capsule. Characteristics of the bands were studied in five positions: maximum external rotation (ER1), abduction (ABD), internal rotation (IR), ABD external rotation (ER2) and anterior elevation-adduction-IR (Hawkins-Kennedy test position). Progressive and randomized sectioning of the bands and capsule with a scalpel was performed to study its impact on mobility and translation of the glenohumeral joint. The bands that tensioned first werein ER1, the AB at 97 ± 9° (80-110); in ER2, the AB at 81 ± 19° (30-100); in IR, the PB at 64 ± 9° (50-80); and in ABD, the PB at 87 ± 10° (70-105). Isolated sectioning of the AB had no effect on ABD, whilst isolated sectioning of the PB allowed greater ABD. In ER2, the AB limited anterior translation. After sectioning the AB, anterior translation remained limited by the PB, which wrapped around the humeral head and locked the joint by pressing the two joint surfaces tightly together. In Hawkins-Kennedy position anterior elevation-adduction-IR, the AB is the first constraint and the posterior translation was limited by the PB alone only in four cases. When the IGHL is isolated, ligament limitation of glenohumeral ABD seems to be uniquely dependent on the PB. In the Hawkins and Kennedy position, the AB is the first constraint. In the case of an isolated lesion to the AB, the PB participates in anterior stabilization of the shoulder by wrapping around the humeral head that cannot dislocate. These findings confirm the role of the PB in glenohumeral joint stability. Level IV.

Effect of subscapularis repair on joint contact forces based on degree of posterior-superior rotator cuff tear severity in reverse shoulder arthroplasty.

Massive irreparable rotator cuff tears (RCTs) affect the clinical outcomes of reverse shoulder arthroplasty (RSA). However, the effects of subscapularis repair on the outcomes of RSA, based on the degree of posterior-superior RCTs, are unclear. This study aimed to examine the effect of subscapularis repair on three-dimensional joint contact forces (JCFs) based on the degree of posterior-superior RCT severity in RSA. Ten human in vivo experimental data were used as input to the musculoskeletal model. A six-degrees-of-freedom (DOF) anatomical shoulder model was developed and validated against three-dimensional JCFs. The 6-DOF musculoskeletal shoulder model of RSA was then developed by importing the reverse shoulder implant into the validated anatomical shoulder model. Based on the various types of posterior-superior RCT severity, inverse dynamic simulations of subscapularis-torn and subscapularis-repaired models of RSA were performed: from isolated supraspinatus tears to partial or massive tears of the infraspinatus and teres minor. The intact rotator cuff model of RSA was also simulated for comparison with the different types of models. Our results showed that the more posterior-superior RCTs progressed in RSA, the more superior JCFs were observed at 90°, 105°, and 120° abduction in the subscapularis-torn model. However, subscapularis repair decreased the superior JCF at those angles sufficiently. In addition, the teres minor muscle-tendon force increased as infraspinatus bundle tears progressed in both the subscapularis-torn and -repaired models, in order to compensate for the reduced force during abduction. However, the teres minor muscle-tendon force was not as high as that of the infraspinatus muscle-tendon, which could result in muscle force imbalance between repaired subscapularis and teres minor. Therefore, our results suggest that repairing the subscapularis and the repairable infraspinatus during RSA can improve glenohumeral joint stability in the superior-inferior direction by restoring muscle force balance between the anterior cuff (i.e., subscapularis) and posterior cuff (i.e., infraspinatus and teres minor). The findings of this study can help clinician decide whether to repair the rotator cuff during RSA to enhance joint stability.

Biomechanical Evaluation of the 2 Different Levels of Coracoid Graft Positions in the Latarjet Procedure for Anterior Shoulder Instability.

In the Latarjet procedure, the ideal placement of the coracoid graft in the medial-lateral position is flush with the anterior glenoid rim. However, the ideal position of the graft in the superior-inferior position (sagittal plane) for restoring glenohumeral joint stability is still controversial. To compare coracoid graft clockface positions between the traditional 3 to 5 o'clock and a more inferior (for the right shoulder) 4 to 6 o'clock with regard to glenohumeral joint stability in the Latarjet procedure. Controlled laboratory study. A total of 10 fresh-frozen cadaveric shoulders were tested in a dynamic, custom-built robotic shoulder model. Each shoulder was loaded with a 50-N compressive load while an 80-N force was applied in the anteroinferior axes at 90° of abduction and 60° of shoulder external rotation. Four conditions were tested: (1) intact, (2) 6-mm glenoid bone loss (GBL), (3) Latarjet procedure fixed at 3- to 5-o'clock position, and (4) Latarjet procedure fixed at 4- to 6-o'clock position. The stability ratio (SR) and degree of lateral humeral displacement (LHD) were recorded. A 1-factor random-intercepts linear mixed-effects model and Tukey method were used for statistical analysis. Compared with the intact state (1.77 ± 0.11), the SR was significantly lower after creating a 6-mm GBL (1.14 ± 0.61, P = .009), with no significant difference in SR after Latarjet 3 to 5 o'clock (1.51 ± 0.70, P = .51) or 4 to 6 o'clock (1.55 ± 0.68, P = .52). Compared with the intact state (6.48 ± 2.24 mm), LHD decreased significantly after GBL (3.16 ± 1.56 mm, P < .001) and Latarjet 4 to 6 o'clock (5.48 ± 3.39 mm, P < .001). Displacement decreased significantly after Latarjet 3 to 5 o'clock (4.78 ± 2.50 mm, P = .04) compared with the intact state but not after Latarjet 4 to 6 o'clock (P = .71). The Latarjet procedure in both coracoid graft positions (3-5 and 4-6 o'clock) restored the SR to the values measured in the intact state. A more inferior graft position (fixed at 4-6 o'clock) may improve shoulder biomechanics, but additional work is needed to establish clinical relevance. An inferior coracoid graft fixation, the 4- to 6-o'clock position, may benefit in restoring normal shoulder biomechanics after the Latarjet procedure.

Does enforcing glenohumeral joint stability matter? A new rapid muscle redundancy solver highlights the importance of non-superficial shoulder muscles.

The complexity of the human shoulder girdle enables the large mobility of the upper extremity, but also introduces instability of the glenohumeral (GH) joint. Shoulder movements are generated by coordinating large superficial and deeper stabilizing muscles spanning numerous degrees-of-freedom. How shoulder muscles are coordinated to stabilize the movement of the GH joint remains widely unknown. Musculoskeletal simulations are powerful tools to gain insights into the actions of individual muscles and particularly of those that are difficult to measure. In this study, we analyze how enforcement of GH joint stability in a musculoskeletal model affects the estimates of individual muscle activity during shoulder movements. To estimate both muscle activity and GH stability from recorded shoulder movements, we developed a Rapid Muscle Redundancy (RMR) solver to include constraints on joint reaction forces (JRFs) from a musculoskeletal model. The RMR solver yields muscle activations and joint forces by minimizing the weighted sum of squared-activations, while matching experimental motion. We implemented three new features: first, computed muscle forces include active and passive fiber contributions; second, muscle activation rates are enforced to be physiological, and third, JRFs are efficiently formulated as linear functions of activations. Muscle activity from the RMR solver without GH stability was not different from the computed muscle control (CMC) algorithm and electromyography of superficial muscles. The efficiency of the solver enabled us to test over 3600 trials sampled within the uncertainty of the experimental movements to test the differences in muscle activity with and without GH joint stability enforced. We found that enforcing GH stability significantly increases the estimated activity of the rotator cuff muscles but not of most superficial muscles. Therefore, a comparison of shoulder model muscle activity to EMG measurements of superficial muscles alone is insufficient to validate the activity of rotator cuff muscles estimated from musculoskeletal models.

Bone formation of the coracoid bone graft after the Bristow procedure assessed using three-dimensional computed tomography

BackgroundThe Bristow procedure has been shown to be a reliable method to prevent recurrent anterior shoulder instability by compensating for glenoid bone loss and producing the sling effect. The degree of postoperative morphological change in the coracoid bone graft is speculated to influence glenohumeral joint stability; however, the details of these changes after the Bristow procedure remain unknown. This study was performed to quantify the postoperative change in the coracoid bone graft volume as assessed by three-dimensional computed tomography (3D-CT). MethodsThe Bristow procedure was performed on 17 shoulders in 17 patients from August 2018 to January 2020. All patients were men, and their mean age at surgery was 17.9 years. The mean follow-up duration was 21.4 months. Within the first week after the operation (Time 0) and at the final follow-up, 3D-CT was used to determine the total coracoid bone graft volume. The clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) shoulder score, the University of California Los Angeles (UCLA) shoulder score, and the Western Ontario Shoulder Instability Index (WOSI). ResultsThe mean volume of the total coracoid bone graft was 1.26 ± 0.29 cm3 at Time 0 and 1.90 ± 0.36 cm3 at the final follow-up (p < 0.0001). The mean JOA score, UCLA score, and WOSI were significantly better at the final follow-up than preoperatively (p < 0.001). No postoperative infection, neurovascular injury, or recurrent instability of the glenohumeral joint occurred. ConclusionsIn the Bristow procedure, the volume of the total coracoid bone graft as shown by 3D-CT was significantly greater at the final follow-up than at Time 0, and bone formation of the coracoid bone graft was found after the Bristow procedure.

A study of the correlation between glenohumeral joint congruence and stability in recurrent shoulder dislocations

To investigate the correlation between glenohumeral joint congruence and stability in recurrent shoulder dislocations. Eighty-nine patients (89 sides) with recurrent shoulder dislocation admitted between June 2022 and June 2023 and met the selection criteria were included as study subjects. There were 36 males and 53 females with an average age of 44 years (range, 20-79 years). There were 40 cases of left shoulder and 49 cases of right shoulder. The shoulder joints dislocated 2-6 times, with an average of 3 times. The three-dimensional models of the humeral head and scapular glenoid were reconstructed using Mimics 20.0 software based on CT scanning images. The glenoid track (GT), inclusion index, chimerism index, fit index, and Hill-Sachs interval (HSI) were measured, and the degree of on/off track was judged (K value, the difference between HSI and GT). Multiple linear regression was used to analyze the correlation between the degree of on/off track (K value) and inclusion index, chimerism index, and fit index. Multiple linear regression analysis showed that the K value had no correlation with the inclusion index ( P>0.05), and was positively correlated with the chimerism index and the fit index ( P<0.05). Regression equation was K=-24.898+35.982×inclusion index+8.280×fit index, R 2=0.084. Humeral head and scapular glenoid bony area and curvature are associated with shoulder joint stability in recurrent shoulder dislocations. Increased humeral head bony area, decreased scapular glenoid bony area, increased humeral head curvature, and decreased scapular glenoid curvature are risk factors for glenohumeral joint stability.

Fully automatic algorithm for detecting and tracking anatomical shoulder landmarks on fluoroscopy images with artificial intelligence

ObjectivePatients with rotator cuff tears present often with glenohumeral joint instability. Assessing anatomic angles and shoulder kinematics from fluoroscopy requires labelling of specific landmarks in each image. This study aimed to develop an artificial intelligence model for automatic landmark detection from fluoroscopic images for motion tracking of the scapula and humeral head.Materials and methodsFluoroscopic images were acquired for both shoulders of 25 participants (N = 12 patients with unilateral rotator cuff tear, 6 men, mean (standard deviation) age: 63.7 ± 9.7 years; 13 asymptomatic subjects, 7 men, 58.2 ± 8.9 years) during a 30° arm abduction and adduction movement in the scapular plane with and without handheld weights of 2 and 4 kg. A 3D full-resolution convolutional neural network (nnU-Net) was trained to automatically locate five landmarks (glenohumeral joint centre, humeral shaft, inferior and superior edges of the glenoid and most lateral point of the acromion) and a calibration sphere.ResultsThe nnU-Net was trained with ground-truth data from 6021 fluoroscopic images of 40 shoulders and tested with 1925 fluoroscopic images of 10 shoulders. The automatic landmark detection algorithm achieved an accuracy above inter-rater variability and slightly below intra-rater variability. All landmarks and the calibration sphere were located within 1.5 mm, except the humeral landmark within 9.6 mm, but differences in abduction angles were within 1°.ConclusionThe proposed algorithm detects the desired landmarks on fluoroscopic images with sufficient accuracy and can therefore be applied to automatically assess shoulder motion, scapular rotation or glenohumeral translation in the scapular plane.Clinical relevance statementThis nnU-net algorithm facilitates efficient and objective identification and tracking of anatomical landmarks on fluoroscopic images necessary for measuring clinically relevant anatomical configuration (e.g. critical shoulder angle) and enables investigation of dynamic glenohumeral joint stability in pathological shoulders.Key Points• Anatomical configuration and glenohumeral joint stability are often a concern after rotator cuff tears.• Artificial intelligence applied to fluoroscopic images helps to identify and track anatomical landmarks during dynamic movements.• The developed automatic landmark detection algorithm optimised the labelling procedures and is suitable for clinical application.

In Vivo Graft Elongation After Arthroscopic Dermal Superior Capsular Reconstruction.

Superior capsular reconstruction (SCR) is a procedure purported to restore stability of the glenohumeral joint after an irreparable rotator cuff tear, but the in vivo behavior of the graft is unknown. Previous work has not evaluated the relationship between graft deformation, kinematics, and healing. To (1) determine regional graft elongation after SCR, (2) determine if graft elongation is related to graft healing, and (3) identify associations between graft elongation and changes in kinematics from presurgery to postsurgery. Case series; Level of evidence, 4. Ten patients who underwent SCR performed abduction and shoulder rotation with the arm at 90° of humerothoracic abduction before and 1 year after surgery while biplane radiographs were collected at 50 images per second. Kinematics was determined with submillimeter accuracy by matching patient-specific digitally reconstructed radiographs of the humerus and scapula to the biplane radiographs using a validated volumetric tracking technique. Graft elongation was calculated using motion of the graft anchors that were identified on postoperative magnetic resonance imaging. Differences in elongation between anterior and posterior regions of the graft, as well as associations between graft elongation, graft healing, and kinematics, were analyzed. Peak graft elongation ranged from a 3% decrease in the anterior region during rotation to up to a 171% increase in the anterior region during abduction and the posterior region during rotation. Grafts that were healed at both anterior anchors reached the intraoperative length at lower abduction angles (60°) than grafts that were not healed at 1 or both of the anterior anchors (87°) (P = .005). The posterior anchor graft origin to insertion distances were 2.1 mm farther apart after surgery compared with before surgery during both abduction and rotation. SCR dermal allografts are stretched well beyond their intraoperative length in vivo. Graft healing appears to be associated with less graft elongation. The posterior portion of the SCR graft does not appear to improve glenohumeral joint stability 1 year after surgery. Improved clinical outcomes after dermal allograft SCR may be because of the spacer effect of the graft rather than improved glenohumeral joint stability 1 year after surgery.

Arthroscopic Latarjet procedure: current concepts and surgical techniques.

The Latarjet procedure is a surgical procedure that can effectively restore glenohumeral stability, especially in patients with anterior shoulder instability and glenoid bone loss. Many studies have shown comparable clinical outcomes between patients undergoing the arthroscopic Latarjet procedure and those undergoing traditional open methods or other glenohumeral joint stabilization procedures. However, the arthroscopic Latarjet procedure is a challenging technique due to the unfamiliar portal placements, proximity of neurovascular structures, and serious postoperative complications. The arthroscopic Latarjet procedure has not yet been widely applied, and a clear understanding of the anatomical structure and the precise methods is required prior to operation performance. Satisfactory clinical outcomes can be achieved by thorough preoperative planning and proper implant fixation methods.

Latarjet’s muscular alterations increase glenohumeral joint stability: A theoretical study

The surgical Latarjet procedure aims to stabilise the glenohumeral joint following anterior dislocations. Despite restoring joint stability, the procedure introduces alterations of muscle paths which likely modify the shoulder dynamics. Currently, these altered muscular functions and their implications are unclear. Hence, this work aims to predict changes in muscle lever arms, muscle and joint forces following a Latarjet procedure by using a computational approach.Planar shoulder movements of ten participants were experimentally assessed. A validated upper-limb musculoskeletal model was utilised in two configurations, i.e., a baseline model, simulating normal joint, and a Latarjet model simulating its related muscular alterations. Muscle lever arms and differences in muscle and joint forces between models were derived from the experimental marker data and static optimisation technique.Lever arms of most altered muscles, hence their role, were substantially changed after Latarjet. Altered muscle forces varied by up to 15% of the body weight. Total glenohumeral joint force increased by up to 14% of the body weight after Latarjet, mostly due to increase in compression force.Our simulation indicated that the Latarjet muscular alterations lead to changes in the muscular recruitment and contribute to the stability of the glenohumeral joint by increasing compression force during planar motions.

Repair of a Reverse HAGL: A 2-Portal Technique

Background: Glenohumeral joint stability is reliant on a combination of static and dynamic constraints. Humeral avulsion of the posterior band of the inferior glenohumeral ligament (HAGL) is an exceedingly rare injury. These injuries can be difficult to diagnose and can lead to continued pain, dysfunction, and recurrent instability. There is a paucity of literature regarding surgical management of reverse HAGL lesions. Indications: Many intrasubstance reverse HAGL lesions can be managed nonoperatively with rehabilitation focused on improving shoulder stability. Although the incidence of recurrent instability in patients with reverse HAGL lesions is unknown, the acute detached humeral lesions in athletes are often treated surgically to restore normal shoulder. Technique Description: The patient was placed in a standard beach chair position, and the standard portals were made for a diagnostic shoulder arthroscopy. The anterior portal was the primary viewing portal. Using the initial posterior skin incision, instruments were introduced through the defect from the retracted posterior band of the inferior glenohumeral ligament. Using a combination of the 30° and 70° arthroscope, the HAGL was mobilized from the infraspinatus musculature. Two knotless suture devices (1.8-mm suture anchor, 2.6-mm suture anchor) were used to reduce the reverse HAGL lesion to an anatomical position, and the posterior capsule was closed thereafter. Results: Only case studies and a single case series have been published pertaining to reverse HAGL repair techniques and related outcomes. When diagnosed and treated appropriately, arthroscopic repairs yield promising results with a high percentage of patients returning to prior level of activity or returning to prior participation level in sport. However, outcome data are limited given the rare occurrence of this injury pattern. Discussion/Conclusion: Reverse HAGL pathology can be treated effectively with arthroscopic surgical repair to restore the normal capsular anatomy and prevent recurrent instability and persistent posterior shoulder pain. Using a 2-portal approach with posterior capsular closure is a minimally invasive operation that allows for appropriate management of these rare injuries. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

INFLUENCE OF CARTILAGE LOSS ON SHOULDER INSTABILITY: A BIOMECHANICAL STUDY

Glenohumeral joint injuries frequently result in shoulder instability. However, the biomechanical effect of cartilage loss on shoulder stability remains unknown. The aim of the current study was to investigate biomechanically the effect of two severity stages of cartilage loss in different dislocation directions on shoulder stability. Joint dislocation was provoked for 11 human cadaveric glenoids in seven different dislocation directions between 3 o'clock (anterior) to 9 o'clock (posterior) dislocation. Shoulder stability ratio (SSR) and concavity gradient were assessed in intact condition, and after 3 mm and 6 mm simulated cartilage loss. The influence of cartilage loss on SSR and concavity gradient was statistically evaluated. Between intact state and 6 mm cartilage loss, both SSR and concavity gradient decreased significantly in every dislocation direction (p≤0.038), except the concavity gradient in 4 o'clock dislocation direction (p=0.088). Thereby, anterior-inferior dislocation directions were associated with the highest loss of SSR and concavity gradient of up to 59.0% and 49.4%, respectively, being significantly higher for SSR compared to all other dislocation directions (p≤0.04). The correlations between concavity gradient and SSR for pooled dislocation directions were significant for all three conditions of cartilage loss (p&lt;0.001). From a biomechanical perspective, articular cartilage of the glenoid contributes significantly to the concavity gradient, correlating strongly with the associated loss in glenohumeral joint stability. The highest effect of cartilage loss was observed in anterior-inferior dislocation directions, suggesting that surgical intervention should be considered for recurrent shoulder dislocations in the presence of cartilage loss.

Effect of intraarticular pressure on glenohumeral kinematics during a simulated abduction motion: a cadaveric study

BackgroundThe current understanding of glenohumeral joint stability is defined by active restrictions and passive stabilizers including naturally-occurring negative intraarticular pressure. Cadaveric specimens have been used to evaluate the role of intraarticular pressure on joint stability, although, while the shoulder’s negative intraarticular pressure is universally acknowledged, it has been inconsistently accounted for.HypothesisDuring continuous, passive humeral abduction, releasing the native intraarticular pressure increases joint translation, and restoring this pressure decreases joint translations.Study designDescriptive Laboratory Study.MethodsA validated shoulder testing system was used to passively abduct the humerus in the scapular plane and measure joint translations for seven (n = 7) cadaveric specimens. The pressure within the glenohumeral joint was measured via a 25-gauge needle during passive abduction of the arm, which was released and subsequently restored. During motion, the rotator cuff muscles were loaded using stepper motors in a force feedback loop and electromagnetic sensors were used to continuously measure the position of the humerus and scapula. Joint translation was defined according to the instant center of rotation of the glenohumeral head according to the recommendations by the International Society of Biomechanics.ResultsArea under the translation versus abduction angle curve suggests that releasing the pressure within the capsule results in significantly less posterior translation of the glenohumeral head as compared to intact (85–90˚, p < 0.05). Posterior and superior translations were reduced after 70˚ of abduction when the pressure within the joint was restored.ConclusionWith our testing system employing a smooth continuous passive motion, we were able to show that releasing intraarticular pressure does not have a major effect on the path of humeral head motion during glenohumeral abduction. However, both violating the capsule and restoring intraarticular pressure after releasing alter glenohumeral translations. Future studies should study the effect of simultaneous external rotation and abduction on the relationship between joint motion and IAP, especially in higher degrees of abduction.Clinical relevanceThoroughly simulating the glenohumeral joint environment in the cadaveric setting may strengthen the conclusions that can be translated from this setting to the clinic.

Multidirectional Instability of Shoulder Joint: A Review

Introduction: The biomechanics of the shoulder joint are complex. To allow a functional range of motion, stability is sacrificed. Glenohumeral joint stability is maintained by static and dynamic stabilizers. Static stabilizers are non-contractile structures including capsulolabral structures and bony glenoid while dynamic stabilizers are contractile structures including rotator cuff, conjoint tendon, and long head of the bicep. The objective of this review is to elaborate on multidirectional instability (MDI) of the shoulder joint and the management of this disorder. Review: Laxity can be affected by hereditary and genetic factors. This can be seen for example in generalized joint laxity which often manifests in the shoulder as MDI. Mutations in collagen genes can cause altered collagen structure, mostly in collagen Type I, resulting in smaller and longer collagen cells. Abnormalities could be found in mRNA synthesis or amino acid transcription for collagen protein, resulting in amino acid content variation. Alterations in fine-tuning mechanism, cleavage process, ionic interaction, cross-linking and metabolism could also result in collagen quality variation. Genetic factors could also cause elastin overproduction rate or amount. Elastin amino acid content alterations could also be affected genetically. These alterations produced a looser static stabilizer. Even so, shoulder joint have multiple static stabilizers and the individual having hereditary laxity does not always have problems related to joint laxity. If the laxity caused problems, it is usually in the form of pain, discomfort, or disruption in shoulder joint function. To compensate for the loose static stabilizer, rehabilitation should be optimized on the contractile, musculature structure of the glenohumeral joint. Besides rehabilitation, capsular shift procedure could also be performed as management of the affected joint by open surgery, arthroscopic capsular plication, or arthroscopic thermal capsulorrhaphy. Conclusion: Based on the review conducted, reoperation rates for open surgery, arthroscopic technique, and thermal technique were approximately 10%, 5%, and 15% subsequently. This should be considered when choosing the appropriate surgery method for MDI management if rehabilitation on contractile structures does not improve patients’ condition.

Arthroscopic Superior Capsular Reconstruction

Background: Limited options exist for young patients with massive, irreparable rotator cuff tears. While several treatment options exist, superior capsular reconstruction (SCR) was developed to restore glenohumeral joint stability by preventing superior humeral head migration during glenohumeral motion. Indications: Arthroscopic SCR is indicated in young patients with a massive, irreparable rotator cuff tear. Patients require a functioning deltoid muscle with minimal to no glenohumeral joint arthritis. In addition, patients should have Hamada grade 2 or less and should have an intact or repairable subscapularis tendon. Technique Description: The patient is positioned in the beach chair position. Standard anterior, posterior, and mid-lateral portals are established. An accessory posterior-superior lateral portal is used for visualization. Three 3.0 mm knotless anchors are placed in the glenoid through lateral percutaneous incisions. Two 4.75 mm anchors are placed adjacent to the humeral articular cartilage for medial row fixation. The graft dimensions are measured using the distance between the anchors. The graft is prepared using a gown card as a template with 5 mm added to the medial, posterior, and anterior graft dimensions, and 10 mm added to the lateral dimension. Sutures are passed through the graft in an inverted horizontal mattress for the glenoid anchors to diminish friction and allow appropriate suture passage through the knotless mechanism of the anchor. The graft is then shuttled into the joint through a lateral PassPort button cannula. Two lateral row anchors are used to secure the lateral graft on the humerus. Native rotator cuff tissue is repaired to the graft using sutures from the medial row anchors as well as free SutureTape. Results: Outcomes following SCR have demonstrated improvements in clinical outcomes and shoulder range of motion. Similar outcomes have been identified between the use of allograft and autograft. Patients generally are able to return to light recreational activities and work. Discussion/Conclusion: Arthroscopic SCR yields favorable results in the setting of a massive, irreparable rotator cuff tear. Meticulous surgical technique is needed to avoid intraoperative surgical complications. The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Ultrasonographic Assessment of Glenohumeral Joint Stability Immediately After Arthroscopic Bankart-Bristow Procedure.

The changes in glenohumeral joint stability after surgery in a clinical setting are yet unknown. This study aimed to compare the anterior humeral head translation between pre- and postsurgical conditions using ultrasonography. It was hypothesized that ultrasonographic assessment would reveal decreased anterior translation. Case series; Level of evidence, 4. A total of 27 patients (24 male, 3 female; mean age, 24.1 ± 9.7 years) with anterior shoulder instability were studied prospectively. All the patients underwent the arthroscopic Bankart-Bristow procedure under general anesthesia, and ultrasonographic evaluation was performed before and immediately after surgery. The forearm was fixed with an arm positioner in the beach-chair position, and the ultrasonographic transducer was located at the posterior part of the shoulder to visualize the humeral head and glenoid rim at the level of interval between the infraspinatus tendon and teres minor tendon. The upper arm was drawn anteriorly with a 40-N force at 0°, 45°, and 90° of shoulder abduction with neutral rotation. The distance from the posterior edge of the glenoid to that of the humeral head was measured using ultrasonography with and without anterior force. Anterior translation was defined by subtracting the distance with anterior force from the distance without anterior force. The humeral head position was translated posteriorly immediately after surgery in all patients. Anterior translation decreased significantly after surgery at 45° (7.7 ± 4.3 vs 5.8 ± 2.0 mm; P = .031) and 90° (8.9 ± 3.4 vs 6.1 ± 2.2 mm; P < .001) of abduction, whereas there was no difference between pre- and postsurgical translation at 0° of abduction (4.9 ± 2.3 vs 4.0 ± 2.1 mm, P = .089). Ultrasonographic assessment immediately after a Bankart-Bristow procedure showed the humeral head was translated posteriorly relative to the glenoid at 0°, 45°, and 90° of abduction. The surgery also decreased anterior translation in response to an anteriorly directed force at 45° and 90° of abduction.

Biomechanical Analysis of Posterior Open-Wedge Osteotomy and Glenoid Concavity Reconstruction Using an Implant-Free, J-Shaped Iliac Crest Bone Graft

Background: Posterior open-wedge osteotomy and glenoid reconstruction using a J-shaped iliac crest bone graft showed promising clinical results for the treatment of posterior instability with excessive glenoid retroversion and posteroinferior glenoid deficiency. Purpose: To evaluate the biomechanical performance of the posterior J-shaped graft to restore glenoid retroversion and posteroinferior deficiency in a cadaveric shoulder instability model. Study Design: Controlled laboratory study. Methods: A posterior glenoid open-wedge osteotomy was performed in 6 fresh-frozen shoulders, allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At each of these 3 preset angles of glenoid retroversion, the following conditions were simulated: (1) intact joint, (2) posterior Bankart lesion, (3) 20% posteroinferior glenoid deficiency, and (4) posterior J-shaped graft (at 0° of retroversion). With the humerus in the Jerk position (60° of glenohumeral anteflexion, 60° of internal rotation), stability was evaluated by measuring posterior humeral head (HH) translation (in mm) and peak translational force (in N) to translate the HH over 25% of the glenoid width. Glenohumeral contact patterns were measured using pressure-sensitive sensors. Fixation of the posterior J-graft was analyzed by recording graft micromovements during 3000 cycles of 5-mm anteroposterior HH translations. Results: Reconstructing the glenoid with a posterior J-graft to 0° of retroversion significantly increased stability compared with a posterior Bankart lesion and posteroinferior glenoid deficiency in all 3 preset degrees of retroversion (P < .05). There was no significant difference in joint stability comparing the posterior J-graft with an intact joint at 0° of retroversion. The posterior J-graft restored mean contact area and contact pressure comparable with that of the intact condition with 0° of retroversion (222 vs 223 mm2, P = .980; and 0.450 vs 0.550 MPa, P = .203). The mean total graft displacement after 3000 cycles of loading was 43 ± 84 µm, and the mean maximal mediolateral graft bending was 508 ± 488 µm. Conclusion: Biomechanical analysis of the posterior J-graft demonstrated reliable restoration of initial glenohumeral joint stability, normalization of contact patterns comparable with that of an intact shoulder joint with neutral retroversion, and secure initial graft fixation in the cadaveric model. Clinical Relevance: This study confirms that the posterior J-graft can restore stability and glenohumeral loading conditions comparable with those of an intact shoulder.

Correlation between superior humeral head migration and proximal long head of biceps tendon pathology in patients with and without rotator cuff tears using magnetic resonance imaging and radiography.

BackgroundThe biomechanical role of the proximal long head of the biceps tendon (PLHB) in glenohumeral joint stability remains controversial. This retrospective study aims to correlate between humeral head migration and PLHB pathology in patients with and without rotator cuff tendon tears using imaging.MethodsSeventy-nine patients who underwent 3T magnetic resonance imaging of the shoulder were retrospectively reviewed. Imaging findings were documented by a fellowship-trained musculoskeletal radiologist. PLHB tendon diameter change, contour irregularity, and signal intensity change were assessed. Rotator cuff status was given a binary assignment of intact vs. torn. Radiographs were used for measurement of the acromiohumeral distance and a cutoff value of 7 mm was set as a lower limit of normal.ResultsIn the cohort of 79 shoulders, 41.8% (33/79) of patients had intact PLHB tendon and rotator cuff, 26.6% (21/79) demonstrated isolated PLHB tendon pathology, 13.9% (11/79) demonstrated isolated rotator cuff tears, and 17.7% (14/79) demonstrated concomitant PLHB tendon pathology and rotator cuff tears. Acromiohumeral distance was preserved in 97.0% (32/33) of patients with intact PLHB tendon and rotator cuff, 28.6% (6/21) of patients with isolated PLHB tendon pathology, 81.8% (9/11) of patients with isolated rotator cuff tears, and 14.3% (2/14) of patients with concomitant PLHB tendon pathology and rotator cuff tears (P < .0001).ConclusionResults of this study have shown that a statistical correlation was present between superior humeral head migration and PLHB tendon pathology with or without rotator cuff tears, compared to rotator cuff pathology alone. Findings suggest that intact PLHB tendon plays an important role in glenohumeral stability.

Glenoid bony morphology along long diameter is associated with the occurrence of recurrent anterior shoulder dislocation: a case-control study based on three-dimensional CT measurements.

The purpose of our study is to compare the anatomic parameters of proximal humerus, glenoid, and glenohumeral joint between patients with recurrent anterior shoulder dislocation (RASD) and patients without RASD with the assistance of three-dimensional (3D) CT scans. Sixty patients were included in the study and divided into group RASD and group control. 3D-CT models of shoulder joint for each included patient were reconstructed and multiple anatomic parameters were measured. There were no statistically significant differences between the two groups in morphological parameters of humerus and glenohumeral joints. Long diameter of glenoid was 3.50 ± 0.34cm for patients in group RASD and 3.31 ± 0.32cm in group control (p = 0.039). There was a statistically significant difference in the ratio of long to short diameter of glenoid (p < 0.001). Ratio of humeral head height to glenoid long diameter (Hhh/Gld) was 1.02 ± 0.07 in group RASD, significantly lower than 1.09 ± 0.08 in group control (p = 0.001). Longitudinal depth of glenoid was significantly higher in group RASD (p = 0.013). The glenoid morphology along long diameter is closely correlated with the stability of glenohumeral joint, including glenoid long diameter and glenoid longitudinal depth. It is especially noteworthy that the value of Hhh/Gld decreases in patients with RASD. The difference of Hhh/Gld between the two groups reminds us that the correlation of bony structure along long diameter between glenoid and humeral head plays an important role in RASD.

Cartilage decisively shapes the glenoid concavity and contributes significantly to shoulder stability

PurposeGlenohumeral joint injuries frequently result in shoulder instability. However, the biomechanical effect of cartilage loss on shoulder stability remains unknown. The aim of the current study was to investigate biomechanically the effect of two severity stages of cartilage loss in different dislocation directions on shoulder stability.MethodsJoint dislocation was provoked in 11 human cadaveric glenoids for 7 different directions between 3 o'clock (anterior) and 9 o'clock (posterior). Shoulder stability ratio (SSR) and concavity gradient were assessed in three states: intact, 3 mm and 6 mm simulated cartilage loss. The influence of cartilage loss on SSR and concavity gradient was statistically evaluated.ResultsBoth SSR and concavity gradient decreased significantly between intact state and 6 mm cartilage loss in every dislocation direction (p ≤ 0.038), except concavity gradient in 4 o'clock direction. Thereby, anterior–inferior dislocation directions were associated with the highest decrease in both SSR and concavity gradient of up to 59.0% and 49.4%, respectively, being significantly bigger for SSR compared with all other dislocation directions (p ≤ 0.040). Correlations between concavity gradient and SSR for pooled dislocation directions were significant in each separate specimen's state (p < 0.001).ConclusionFrom a biomechanical perspective, articular cartilage of the glenoid contributes significantly to the concavity gradient, correlating strongly with the associated loss in glenohumeral joint stability. The biggest effect of cartilage loss is observed in the most frequently occurring anterior–inferior dislocation directions, suggesting that surgical interventions to restore cartilage's surface and concavity should be considered for recurrent shoulder dislocations in presence of cartilage loss.