Effect of Arthroscopic Stabilization on In Vivo Glenohumeral Joint Motion and Clinical Outcomes in Patients With Anterior Instability

Three-dimensional kinematics in patients with anterior shoulder instability - A systematic review with meta-analysis

Anterior Shoulder Instability (ASI) is a common orthopedic condition often resulting in altered shoulder kinematics. Understanding the biomechanics of the unstable shoulder is critical to determine the most appropriate treatment. This study aims to conduct the first systematic review and meta-analysis of three-dimensional (3D) shoulder kinematic studies in ASI patients. A broad search was conducted within PubMed, Scopus, and Cochrane Library following the PRISMA guidelines. All cross-sectional or longitudinal studies with 3D motion analysis describing shoulder kinematics in patients with ASI were included. The quality of each study was assessed using the MINORS criteria. Qualitative and quantitative analyses were performed. Nine studies were included in the qualitative analysis and two in the meta-analysis. The qualitative review detected conflicting evidence for some parameters. The humeral head had a greater anterior translation in unstable shoulders in three of the studies analyzed, while the difference was not significant in one and another found higher variability for global humeral translation for instability patients. Two studies showed decreased rotation range of motion for unstable shoulders while one did not find significant differences. Conflicting results were also found regarding changes in scapulohumeral rhythm and scapular orientation. The meta-analysis indicated a greater scapulohumeral rhythm on the coronal plane for the instability group, suggesting a relatively greater contribution of motion at the glenohumeral joint compared with the scapulothoracic joint for arm abduction, and reduced glenohumeral peak angles for unstable shoulders. Identifying and quantifying kinematic changes associated with ASI are vital for refining treatment interventions.

Glenohumeral joint kinematics during apprehension-relocation test in patients with anterior shoulder instability and glenoid bone loss

Aims

This study aimed to quantify the shoulder kinematics during an apprehension-relocation test in patients with anterior shoulder instability (ASI) and glenoid bone loss using the radiostereometric analysis (RSA) method. Kinematics were compared with the patient's contralateral healthy shoulder.

Methods

A total of 20 patients with ASI and > 10% glenoid bone loss and a healthy contralateral shoulder were included. RSA imaging of the patient's shoulders was performed during a repeated apprehension-relocation test. Bone volume models were generated from CT scans, marked with anatomical coordinate systems, and aligned with the digitally reconstructed bone projections on the RSA images. The glenohumeral joint (GHJ) kinematics were evaluated in the anteroposterior and superoinferior direction of: the humeral head centre location relative to the glenoid centre; and the humeral head contact point location on the glenoid.

Results

During the apprehension test, the centre of the humeral head was 1.0 mm (95% CI 0.0 to 2.0) more inferior on the glenoid for the ASI shoulder compared with the healthy shoulder. Furthermore, the contact point of the ASI shoulder was 1.4 mm (95% CI 0.3 to 2.5) more anterior and 2.0 mm (95% CI 0.8 to 3.1) more inferior on the glenoid compared with the healthy shoulder. The contact point of the ASI shoulder was 1.2 mm (95% CI 0.2 to 2.6) more anterior during the apprehension test compared to the relocation test.

Conclusion

The humeral head centre was located more inferior, and the GHJ contact point was located both more anterior and inferior during the apprehension test for the ASI shoulders than the healthy shoulders. Furthermore, the contact point displacement between the apprehension and relocation test revealed increased joint laxity for the ASI shoulder than the healthy shoulders. These results contribute to existing knowledge that ASI shoulders with glenoid bone loss may also suffer from inferior shoulder instability.

Anterior-posterior glenohumeral translation in shoulders with traumatic anterior instability: a systematic review of the literature

Background

Reports of glenohumeral translation in shoulders with traumatic anterior instability have been presented. The aim of this systematic review was to investigate anterior-posterior translation in shoulders with traumatic anterior instability.

Methods

This systematic review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies including patients aged ≥15 years with previous traumatic anterior shoulder dislocation or subluxation were included. The outcome was anterior-posterior glenohumeral translation. A search of PubMed, Embase, and Cochrane library was performed on July 17, 2022. Two reviewers individually screened titles and abstracts, reviewed full text, extracted data, and performed quality assessment.

Results

Twenty studies (582 unstable shoulders in total) of varying quality were included. There was a lack of standardization and unity across studies. Radiography, ultrasound, computed tomography, magnetic resonance imaging, motion tracking, instrumentation, and manual testing were used to assess the glenohumeral translation. The glenohumeral translation in unstable shoulders ranged from 0.0 ± 0.8 mm to 11.6 ± 3.7 mm, as measured during various motion tasks, arm positions, and application of external force. The glenohumeral translation was larger or more anteriorly directed in unstable shoulders than in stable when contralateral healthy shoulders or a healthy control group were included in the studies. Several studies found that the humeral head was more anteriorly located on the glenoid in the unstable shoulders.

Conclusion

This systematic review provides an overview of the current literature on glenohumeral translation in traumatic anterior shoulder instability. It was not able to identify a threshold for abnormal translation in unstable shoulders, due to the heterogeneity of data. The review supports that not only the range of translation but also the direction hereof as well as the location of the humeral head on the glenoid seem to be part of the pathophysiology. Technical development and increased attention to research methodology in recent years may provide more knowledge and clarity on this topic in the future.

Empirical joint contact mechanics: A comprehensive review

Empirical joint contact mechanics measurement (EJCM; e.g. contact area or force, surface velocities) enables critical investigations of the relationship between changing joint mechanics and the impact on surface-to-surface interactions. In orthopedic biomechanics, understanding the changes to cartilage contact mechanics following joint pathology or aging is critical due to its suggested role in the increased risk of osteoarthritis (OA), which might be due to changed kinematics and kinetics that alter the contact patterns within a joint. This article reviews and discusses EJCM approaches that have been applied to articulating joints such that readers across different disciplines will be informed of the various measurement and analysis techniques used in this field. The approaches reviewed include classical measurement approaches (radiographic and sectioning, dye staining, casting, surface proximity, and pressure measurement), stereophotogrammetry/motion analysis, computed tomography (CT), magnetic resonance imaging (MRI), and high-speed videoradiography. Perspectives on approaches to advance this field of EJCM are provided, including the value of considering relative velocity in joints, tractional stress, quantification of joint contact area shape, consideration of normalization techniques, net response (superposition) of multiple input variables, and establishing linkages to regional cartilage health status. EJCM measures continue to provide insights to advance our understanding of cartilage health and degeneration and provide avenues to assess the efficacy and guide future directions of developing interventions (e.g. surgical, biological, rehabilitative) to optimize joint's health and function long term.

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

Background:

The changes in glenohumeral joint stability after surgery in a clinical setting are yet unknown.

Purpose/Hypothesis:

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.

Study Design:

Case series; Level of evidence, 4.

Methods:

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.

Results:

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).

Conclusion:

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.

Effect of Anterior Glenoid Chondrolabral Defects on Anterior Glenohumeral Stability: A Biomechanical Study

Background:

It is well known that glenoid osseous defects >13.5% of the glenoid width critically destabilize the shoulder, as do labral tears. Chondrolabral defects often occur with anterior dislocation of the shoulder. It is unclear whether glenoid chondrolabral defects contribute to shoulder stability and, if so, at what size they become critical.

Purpose/Hypothesis:

The purpose of this study was to determine the effect of incremental chondrolabral defect sizes on anterior shoulder stability in the setting of labral deficiency. The hypothesis was that chondrolabral defects ≥13.5% of the glenoid width will decrease anterior shoulder stability.

Study Design:

Controlled laboratory study.

Methods:

This controlled laboratory study tested 12 fresh-frozen shoulders. Specimens were attached to a custom testing device in abduction and neutral rotation with 50-N compression applied to the glenoid. The humeral head was translated 10 mm anterior, anteroinferior, and anterosuperior with the conditions of intact cartilage and labrum and anterior full-thickness chondrolabral defects of 3-, 6-, and 9-mm width. Translation force was measured continuously. Peak translation force divided by 50-N compressive force defined the stability ratio. Data were analyzed using analysis of variance.

Results:

The anterior stability ratio decreased between the intact state (36% ± 7%) and all defects ≥3 mm (≤32% ± 8%; P ≤ .023). The anteroinferior stability ratio decreased between the intact state (52% ± 7%) and all defects ≥3 mm (≤47% ± 7%; P ≤ .006). The anterosuperior stability ratio decreased between the intact state (36% ± 4%) and all defects ≥6 mm (≤33% ± 4%; P ≤ .006). A 3-mm defect equated to 10% of the glenoid width. There were moderate to strong negative correlations between chondrolabral defect size and stability ratio in the anterior, anteroinferior, and anterosuperior directions (r = –0.79, –0.63, and –0.58, respectively; P ≤ .001). There were moderate to strong negative correlations between the percentage of glenoid chondrolabral defect size to the glenoid width and the stability percentage in all directions (r = –0.81, –0.63, and –0.61; P ≤ .001).

Conclusion:

An anterior glenoid chondrolabral defect ≥3 mm (>10% of the glenoid width) significantly decreased anterior and anteroinferior stability. Chondrolabral defect size negatively correlated with stability.

Clinical Relevance:

To fully restore glenohumeral stability, in addition to labral repair, it may be necessary to reconstruct chondrolabral defects as small as 3 mm (10% of the glenoid width).

Morphology of Glenoid Cartilage Defects in Anteroinferior Glenohumeral Instability

Background:

Glenoid cartilage defects may contribute to anterior shoulder instability recurrence and progression to osteoarthritis, but their morphology remains unknown.

Purpose/Hypothesis:

The purpose was to determine the shape, size, and location of glenoid cartilage defects and the prevalence and risk factors for cartilage defects in the setting of anterior glenohumeral instability. It was hypothesized that glenoid cartilage defects would be common, would be associated with recurrence of dislocation, and would share similar morphology with glenoid osseous defects.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

In this retrospective study, all patients who underwent arthroscopic surgical treatment for anterior glenohumeral instability between January 2012 and May 2019 were included; excluded were patients with documented posterior or multidirectional instability or previous glenohumeral surgery. For each patient, the operative report, arthroscopic images, and preoperative magnetic resonance imaging (MRI) scans were reviewed to determine the prevalence of cartilage injury. For those patients with an Outerbridge grade 3 or 4 defect, the cartilage surfaces on the MRI scans were segmented to make 3-dimensional (3-D) segmentations. From these 3-D segmentations, we measured length, width, and surface area of the glenoid and defect, and the orientation of the defect relative to the superior and inferior poles of the glenoid. A multivariable analysis was conducted to determine correlates with cartilage damage.

Results:

In 322 patients treated operatively for anterior glenohumeral instability, 38% had a concomitant cartilage defect. The mean cartilage defect was located directly anteriorly at the 3:07 clockface position (range, 2:10-4:05) and encompassed 6.5% ± 3.5% of the glenoid surface area. However, defects ranged up to >56% of glenoid length and up to 27% of glenoid width, and the largest defect encompassed 19.5% of the glenoid cartilage surface area. Patients with a cartilage defect were more likely to be male (P = .031) and to have undergone a concomitant posterior labral repair (P = .018).

Conclusion:

Cartilage defects were common in patients with operatively treated anterior glenohumeral instability, occurring in 38% of patients. These defects were located directly anteriorly at 3:07, similar to osseous glenoid defects. Future prospective studies with cartilage-specific MRI sequences should be conducted.

The impact of age on 30-day complications following shoulder instability surgery

HYPOTHESIS

The purpose of this study was to evaluate short-term outcomes including medical complications, overnight admission, and 30-day readmission with regard to patient age at the time of shoulder instability surgery.

METHODS

Patients undergoing surgery for glenohumeral instability were collected from the National Surgical Quality Improvement Program between the years of 2005 and 2016. These patients were separated into cohorts of younger than 25 years, 25-34 years, and older than 34 years. Medical complications, hospital admission, and 30-day readmission were compared using multivariate analysis.

RESULTS

Of the 5449 patients included, there were 2035 (37.0%) patients younger than 25 years, 1815 (33.0%) between 25 and 34 years, and 1649 (30.0%) 35 and older. Overall, 81.7% of patients underwent an arthroscopic Bankart repair, 12.6% of patients underwent an open Bankart repair, and 5.7% of patients underwent a Latarjet-Bristow procedure. The risk of 30-day readmission increased with age, ranging from 0.24% for <25 years old to 0.92% for 35 years and older (P = .040). Operative duration greater than 60 minutes (odds ratio [OR] 1.76; P = .001), duration greater than 90 minutes (OR 3.58; P < .001), and American Society of Anesthesiologists class III and IV (OR 1.80; P = .001) were associated with increased risk of overnight hospital stay. Compared with arthroscopic Bankart repair, the Latarjet-Bristow procedure was associated with increased total complications (OR 3.30; P = .021), overnight hospital stay (OR 4.64; P < .001), and 30-day readmission (OR 3.39; P = .013).

CONCLUSION

This study demonstrates that even in the relatively young and healthy shoulder instability patient cohort, patients older than 25 years are almost 4 times more likely to experience a complication. Additionally, Latarjet-Bristow procedures are 3-4 times more likely to experience a complication or readmission than other shoulder instability procedures.

Incidence of and Risk Factors for Glenohumeral Osteoarthritis After Anterior Shoulder Instability: A US Population-Based Study With Average 15-Year Follow-up

Background:

The rate of osteoarthritis (OA) in patients with a history of previous anterior shoulder instability (ASI) varies within the literature, with the majority of studies investigating rates after surgical stabilization. ASI appears to lead to increased rates of OA, although risk factors for developing OA in cohorts treated nonoperatively and operatively are not well-defined.

Purpose:

To determine the incidence of clinically symptomatic OA and identify potential risk factors for the development of OA in patients younger than 40 years with a known history of ASI.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

An established, geographically based database was used to identify patients in the United States who were younger than 40 years and were diagnosed with ASI between 1994 and 2014. Patient information, including demographic, imaging, and surgical details, was collected. Comparative analysis was performed between groups with and without OA at final follow-up as well as between patients who underwent surgical and nonsurgical management.

Results:

The study population consisted of 154 patients with a mean follow-up of 15.2 years (range, 5.1-29.8 years). The mean age at initial instability event was 20.9 years (95% CI, 19.9-22.0 years). Overall, 22.7% of patients developed clinically symptomatic glenohumeral OA. Multivariate analysis revealed that current or former smokers (odds ratio [OR], 4.3; 95% CI, 1.1-16.5; P = .030), hyperlaxity (OR, 10.1; 95% CI, 1.4-72.4; P = .020), laborer occupation (OR, 6.1; 95% CI, 1.02-36.1; P = .043), body mass index (BMI) (OR, 1.2; 95% CI, 1.03-1.3; P = .012), and age at initial instability (OR, 1.1; 95% CI, 1.02-1.2; P = .013) as potential independent risk factors when accounting for other demographic and clinical variables.

Conclusion:

In a US geographic population of patients younger than 40 years with ASI, approximately one-fourth of patients developed symptomatic OA at a mean follow-up of 15 years from their first instability event. When accounting for differences in patient demographic and clinical data, we noted a potentially increased risk for the development of OA in patients who are current or former smokers, have hyperlaxity, are laborers, have higher BMI, and have increased age at initial instability event. Smoking status, occupation, and BMI are modifiable factors that could potentially decrease risk for the development of symptomatic OA in these patients.

Glenohumeral stabilizing roles of the scapulohumeral muscles: Implications of muscle geometry

Dynamic stability provided by muscles is integral for function and integrity of the glenohumeral joint. Although the high degree of inter-individual variation that exists in musculoskeletal geometry is associated with shoulder injuries, there is limited research associating the effects of muscle geometry on the potential stabilizing capacities of shoulder muscles. The purpose of this investigation was to evaluate the stabilizing functions of the scapulohumeral muscles using computational modeling and to quantify the sensitivity of muscle stabilizing roles to changes in muscle geometry. Muscle stability ratios in the superior/inferior and anterior/posterior directions were computed as the ratio between the muscle's shear components relative to compression throughout arm elevation in the scapular plane. Muscle attachment locations on the clavicle, scapula, and humerus were iteratively adjusted using Monte Carlo simulations. Consistent with previous experimental studies, the rotator cuff muscles were identified as the primary stabilizers of the glenohumeral joint; whereas the deltoids and coracobrachialis have a strong potential for superiorly translating the humerus at low elevation angles. Variations in the stability ratios due to altered muscle geometry were muscle- and angle-specific. In general, the highest variation was observed for the subscapularis and deltoids (at low elevation angles), while the remaining rotator cuff muscles largely maintained their capacity to provide compressive stabilizing forces at the glenohumeral joint. Changes in muscle stability ratios may affect dynamic stability of the humerus that could differentially predispose individuals to greater risk for injury.

Association Between Years of Competition and Shoulder Function in Collegiate Swimmers

BACKGROUND

Shoulder injuries are common among competitive swimmers, and the progression of shoulder pathology is not well understood. The objective of this study was to assess the extent to which years of competitive swim training were associated with physical properties of the supraspinatus muscle and tendon, shoulder strength, and self-reported assessments of shoulder pain and function.

HYPOTHESIS

Increasing years of competition will be associated with declining physical properties of the supraspinatus muscle/tendon and declining self-reported assessments of pain and function.

STUDY DESIGN

Descriptive epidemiology study.

LEVEL OF EVIDENCE

Level 4.

METHODS

After institutional approval, 18 collegiate female swimmers enrolled in the study. For each swimmer, supraspinatus tendon thickness was measured; tendinosis was assessed using ultrasound imaging, supraspinatus muscle shear wave velocity was assessed using shear wave elastography, isometric shoulder strength was measured using a Biodex system, and self-reported assessments of pain/function were assessed using the Western Ontario Rotator Cuff (WORC) score. All subjects were tested before the start of the collegiate swim season. Linear regression was used to assess the association between years of competition and the outcome measures.

RESULTS

Years of participation was positively associated with tendon thickness ( P = 0.01) and negatively associated with shear wave velocity ( P = 0.04) and WORC score ( P < 0.01). Shoulder strength was not associated with years of participation ( P > 0.39).

CONCLUSION

Long-term competitive swim training is associated with declining measures of supraspinatus muscle/tendon properties and self-reported measures of pain and function. Although specific injury mechanisms are still not fully understood, these findings lend additional insight into the development of rotator cuff pathology in swimmers.

CLINICAL RELEVANCE

Lengthy swimming careers may lead to a chronic condition of reduced mechanical properties in the supraspinatus muscle and tendon, thereby increasing the likelihood of rotator cuff pathology.