Biomechanical comparison of open Bankart repair vs. conjoint tendon transfer in a 10% anterior glenoid bone loss shoulder instability model.

BACKGROUND: The treatment of shoulder instability in patients with subcritical glenoid bone loss poses a difficult problem for surgeons as new evidence supports a higher failure rate when a standard arthroscopic Bankart repair is used. The purpose of this study was to compare a conjoint tendon transfer (soft-tissue Bristow) to an open Bankart repair in a cadaveric instability model of 10% glenoid bone loss. METHODS: Eight cadaveric shoulders were tested using a custom testing system that allows for a 6-degree-of-freedom positioning of the glenohumeral joint. The rotator cuff muscles were loaded to simulate physiologic muscle conditions. Four conditions were tested: (1) intact, (2) Bankart lesion with 10% bone loss, (3) conjoint tendon transfer, and (4) open Bankart repair. Range of motion, glenohumeral kinematics, and anterior-inferior translation at 60° of external rotation with 20 N, 30 N, and 40 N were measured in the scapular and coronal planes. Glenohumeral joint translational stiffness was calculated as the linear fit of the translational force-displacement curve. Force to anterior-inferior dislocation was also measured in the coronal plane. Repeated measures analysis of variance with a Bonferroni correction was used for statistical analysis. RESULTS: A Bankart lesion with 10% bone loss increased the range of motion in both the scapular (P = .001) and coronal planes (P = .001). The conjoint tendon transfer had a minimal effect on the range of motion (vs. intact P = .019, .002), but the Bankart repair decreased the range of motion to intact (P = .9, .4). There was a significant decrease in glenohumeral joint translational stiffness for the Bankart lesion compared with intact in the coronal plane (P = .021). The conjoint tendon transfer significantly increased stiffness in the scapular plane (P = .034), and the Bankart repair increased stiffness in the coronal plane (P = .037) compared with the Bankart lesion. The conjoint tendon transfer shifted the humeral head posteriorly at 60° and 90° of external rotation in the scapular plane. The Bankart repair shifted the head posteriorly in maximum external rotation in the coronal plane. There was no significant difference in force to dislocation between the Bankart repair (75.8 ± 6.6 N) and the conjoint tendon transfer (66.5 ± 4.4 N) (P = .151). CONCLUSION: In the setting of subcritical bone loss, both the open Bankart repair and conjoint tendon transfer are biomechanically viable options for the treatment of anterior shoulder instability; further studies are needed to extrapolate these data to the clinical setting.

Native Glenoid Depth and Hill-Sachs Lesion Morphology in Traumatic Anterior Shoulder Instability.

BACKGROUND: Although Hill-Sachs lesions (HSLs) are assumed to be influenced by glenoid characteristics in the context of bipolar bone loss, little is known about how glenoid concavity influences HSL morphology. PURPOSE: To investigate the relationship between the native glenoid depth and HSL morphological characteristics. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Computed tomography images of bilateral shoulders from 151 consecutive patients with traumatic unilateral anterior shoulder instability were retrospectively reviewed. Patients were categorized into flat (<1 mm), moderate (1-2 mm), and deep (>2 mm) groups based on the native glenoid depth measured from the contralateral unaffected shoulder. The HSL morphological characteristics included size (depth, width, length, and volume), location (medial, superior, and inferior extent), and orientation (rim and center angle). The glenoid characteristics included diameter, depth, version, and bone loss. The patient, glenoid, and HSL morphological characteristics were compared among the 3 depth groups. Subsequently, the independent predictors of some critical HSL morphological characteristics were determined using multivariate stepwise regression. RESULTS: After exclusion of 55 patients, a total of 96 patients were enrolled and classified into the flat group (n = 31), moderate group (n = 35), and deep group (n = 30). Compared with those in the flat group, patients in the deep group were more likely to have dislocation (38.7% vs 93.3%; P = .009) at the primary instability and had a significantly larger number of dislocations (1.1 ± 1.0 vs 2.2 ± 1.8; P = .010); moreover, patients in the deep group had significantly deeper, wider, larger volume, more medialized HSLs and higher incidences of off-track HSLs (all P≤ .025). No significant differences were detected among the 3 groups in HSL length, vertical position, and orientation (all P≥ .064). After adjustment for various radiological and patient factors in the multivariate regression model, native glenoid depth remained the strongest independent predictor for HSL depth (ß = 0.346; P < .001), width (ß = 0.262; P = .009), volume (ß = 0.331; P = .001), and medialization (ß = -0.297; P = .003). CONCLUSION: The current study sheds light on the association between native glenoid depth and the morphology of HSLs in traumatic anterior shoulder instability. Native glenoid depth was independently and positively associated with HSL depth, width, volume, and medialization. Patients with deeper native glenoids were more likely to have off-track HSLs and thus require more attention in the process of diagnosis and treatment.

Does glenoid bone loss accompany posterior shoulder instability with only labral tear? A magnetic resonance imaging-based study.

BACKGROUND: The primary aim of this study was to investigate bone loss in the glenoid with magnetic resonance imaging in posterior shoulder instability with only a labral tear. METHODS: A total of 76 patients operated on because of posterior and anteroposterior shoulder instability only with a labral tear between 2006 and 2019 (n = 40 and n = 36, respectively) were included in this study. The instability type, a presence of an additional superior labrum anteroposterior (SLAP) lesion, the number of dislocations, and the magnetic resonance imaging-based measurements (the glenoid diameter and the bone defect size in the glenoid, the Hill-Sachs lesion [HSL] and the reverse HSL [rHSL] length, the angle and the arc length of HSL and rHSL, and the humerus head diameter and its area) were analyzed. RESULTS: The size of the anterior glenoid defect, the rHSL measurements (length, angle, and arc length), and the ratio of the anterior glenoid defect size to the glenoid diameter were significantly higher for anteroposterior instability (P < .01) cases. There was no significant difference (P = .49, .64, and .82, respectively) for the presence of an additional SLAP pathology, the glenoid diameter, the posterior glenoid defect, and the ratio of the posterior glenoid defect size to the glenoid diameter in posterior and anteroposterior instability groups. The increased number of dislocations was associated with increased rHSL length and total arc length (P = .04 and .03, respectively). An additional SLAP lesion in posterior shoulder instabilities was not associated with the bone defect size (P = .29). CONCLUSION: Although the posterior shoulder instability with only a labral tear is likely to cause a bone defect, we have shown that the instability is not expected to be caused by the bone defect. Therefore, this study points out that only soft tissue repair without considering the bone defect could be promising in this patient group.

Predictors of Bone Loss in Anterior Glenohumeral Instability.

BACKGROUND: Anterior shoulder instability can result in bone loss of both the anterior glenoid and the posterior humerus. Bone loss has been shown to lead to increased failure postoperatively and may necessitate more complex surgical procedures, resulting in worse clinical outcomes and posttraumatic arthritis. HYPOTHESIS/PURPOSE: The purpose of this study was to investigate predictors of glenoid and humeral head bone loss in patients undergoing surgery for anterior shoulder instability. It was hypothesized that male sex, contact sport participation, traumatic dislocation, and higher number of instability events would be associated with greater bone loss. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 892 patients with anterior shoulder instability were prospectively enrolled in the Multicenter Orthopaedic Outcomes Network (MOON) Shoulder Instability cohort. The presence and amount of anterior glenoid bone loss and accompanying Hill-Sachs lesions were quantified. Descriptive information and injury history were used to construct proportional odds models for the presence of any bone defect, for defects >10% of the anterior glenoid or humeral head, and for combined bony defects. RESULTS: Anterior glenoid bone loss and Hill-Sachs lesions were present in 185 (20.7%) and 470 (52.7%) patients, respectively. Having an increased number of dislocations was associated with bone loss in all models. Increasing age, male sex, and non-White race were associated with anterior glenoid bone defects and Hill-Sachs lesions. Contact sport participation was associated with anterior glenoid bone loss, and Shoulder Actitvity Scale with glenoid bone loss >10%. A positive apprehension test was associated with Hill-Sachs lesions. Combined lesions were present in 19.4% of patients, and for every additional shoulder dislocation, the odds of having a combined lesion was 95% higher. CONCLUSION: An increasing number of preoperative shoulder dislocations is the factor most strongly associated with glenoid bone loss, Hill-Sachs lesions, and combined lesions. Early surgical stabilization before recurrence of instability may be the most effective method for preventing progression to clinically significant bone loss. Patients should be made aware of the expected course of shoulder instability, especially in athletes at high risk for recurrence and osseous defects, which may complicate care and worsen outcomes. REGISTRATION: NCT02075775 (ClinicalTrials.gov identifier).

Arthroscopic findings of the glenohumeral joint in symptomatic anterior instabilities: comparison between overhead throwing disorders and traumatic shoulder dislocation.

BACKGROUND: The term shoulder instability refers to a variety of mechanisms and clinical presentations. One of the common pathologies of throwing disorders is internal impingement with anterior instability. Most throwing athletes with symptomatic internal impingement with anterior instability exhibit positive apprehension and relocation test results, whereas those with recurrent anterior shoulder instability display positive apprehension test results. While the glenoid labrum-inferior glenohumeral ligament complex is a significant critical stabilizer for the prevention of anterior shoulder dislocation, the characteristics of the essential lesion in internal impingement with anterior instability have not been determined yet. This study aimed to compare the intra-articular lesion of athletes with internal impingement related to the overhead throwing motion in athletes with a traumatic shoulder dislocation. METHODS: Sixty-one athletes (all men; mean age, 25.2 ± 12.6 yr) who underwent an arthroscopic procedure were divided into 2 groups: 25 in the throwing group and 36 in the dislocation group. All shoulders had subtle glenohumeral instability defined by a positive anterior apprehension test and a relocation test. Those with voluntary and multidirectional instability and large glenoid bone loss (more than 25%) were excluded from the current study. All shoulders were evaluated for the following evidence: rotator cuff injury, superior labrum tear anterior and posterior lesions, labral pathologies including Bankart lesions, osteochondral lesions to the humeral head, biceps tendon fraying or rupture, and inferior glenohumeral ligament and middle glenohumeral ligament (MGHL) conditions. RESULTS: Arthroscopic findings of the throwing group showed more supraspinatus injuries (92% and 25%, P < .001), type II superior labrum tear anterior and posterior lesions (60% and 3%, P < .001), posterosuperior labral lesions (92% and 39%, P < .001), and hypoplastic MGHLs (56% and 6%, P < .001) and lesser Bankart lesions (8% and 92%, P < .05) than those of the dislocation group. CONCLUSIONS: These results indicate that the characteristic lesions of internal impingement with anterior instability in throwing athletes include partial thickness rotator cuff tears, superior labrum tear anterior and posterior lesions, posterosuperior labral tears, and hypoplastic MGHLs. As expected, the physiopathology of internal impingement with anterior instability in throwing athletes may be related to the dysfunction of the anterosuperior glenohumeral capsular ligament, including the MGHL, rather than the inferior glenohumeral ligament as in traumatic anterior shoulder dislocations. These findings would be useful for defining treatment strategies for internal impingement with anterior instability in overhead throwing athletes.

An assessment of SLAP type 5 lesions using proton density oblique sagittal imaging in magnetic resonance arthrography.

BACKGROUND: Bankart lesions accompany superior labrum anteroposterior (SLAP) lesions; these are called SLAP type 5. PURPOSE: To compare SLAP type 5 lesions using routine magnetic resonance arthrography (MRA) and thin-slice oblique sagittal proton density (PDW) sequences and correlation operation results. MATERIAL AND METHODS: In total, 181 patients were admitted with shoulder instability. The study was completed with 44 patients. The presence or absence of isolated Bankart and SLAP type 5 lesions in routine MRA and PDW oblique sagittal images were evaluated separately. Absence of rupture scored 0 points, suspected ruptures scored 1 point, and apparent ruptures scored 2 points. The two scores were compared with the shoulder arthroscopy findings. RESULTS: According to the findings in the shoulder arthroscopy, 40 patients had Bankart lesions and 17 patients had accompanying SLAP type 5 lesions. To detect a Bankart lesion, there was no significant difference between routine MRA sequences and PDW oblique sagittal images (P = 0.061). Routine MRA sensitivity was 95%, specificity 25%, positive predictive value (PPV) 92%, negative predictive value (NPV) 33%, while for PDW oblique sagittal images, sensitivity was 75%, specificity 100%, PPV 100%, and NPV 28.5%. In 8/17 type 5 SLAP lesions, routine MRA detected sensitivity 47%, specificity 92.6%, PPV 80%, and NPV 73.5%; in 14/17 SLAP type 5 lesions, PDW oblique sagittal images detected sensitivity 82%, specificity 100%, PPV 100%, and NPV 90% (P = 0.015). CONCLUSION: The PDW oblique sagittal images may play a significant role in assessing the anterior and superior extent of the tears.

Glenoid Bone Loss Directly Affects Hill-Sachs Morphology: An Advanced 3-Dimensional Analysis.

BACKGROUND: While the glenoid track concept presents a useful prediction for recurrent glenohumeral instability, little is known about the humeral head bony architecture as it relates to glenoid erosion in the setting of bipolar bone loss. PURPOSE: To (1) qualitatively and quantitatively analyze the interplay between glenoid bone loss (GBL) and Hill-Sachs lesions (HSLs) in a cohort of patients with anterior instability using 3-dimensional imaging software and (2) assess the relationships between GBL and HSL characteristics. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Patients were identified who had anterior shoulder instability with a minimum 5% GBL and evidence of HSL confirmed on computed tomography. Unilateral 3-dimensional models of the ipsilateral proximal humeral head and en face sagittal oblique view of the glenoid were reconstructed using MIMICS software (Materialise NV). GBL surface area, width, defect length, and glenoid track width were quantified. The volume, surface area, width, and depth of identified HSLs were quantified with their location (medial, superior, and inferior extent) on the humeral head. Severity of GBL was defined as percentage glenoid bone surface area loss and categorized as low grade (5%-10%), moderate grade (>10% to 20%), high grade (>20% to 30%), and extensive (>30%). Analysis of variance was then computed to determine significance (P < .05) between severity of GBL and associated HSL parameters. RESULTS: In total, 100 patients met inclusion criteria (mean age, 27.9 years; range, 18-43 years), which included 58 right shoulders and 42 left shoulders (84 male, 16 female). Among groups, there were 32 patients with low-grade GBL (mean GBL = 6.1%), 38 with moderate grade (mean GBL = 16.2%), 17 with high grade (mean GBL = 23.7%), and 13 with extensive (mean GBL = 34.0%), with an overall mean GBL of 18.1% (range, 5%-39%). Patients with 5%-10% GBL had significantly narrower HSLs (average and maximum width; P < .03) and deeper HSLs (average depth; P = .002) as compared with all other GBL groups, while greater GBL was associated with wider and shallower HSLs. GBL width, percentage width loss, defect length, and glenoid track width all significantly differed across the 4 GBL groups (P < .05). CONCLUSION: HSLs had significantly different morphological characteristics depending on the severity of GBL, indicating that GBL was directly related to the characteristics of HSLs. Patients presenting with smaller glenoid defects had significantly narrower and deeper HSLs with less humeral head surface area loss, while greater GBL was associated with wider and shallower HSLs.

Management of Complex and Revision Anterior Shoulder Instability.

Treatment of recurrent anterior shoulder instability has gained significant interest in recent years and involves evaluation of both glenoid and humeral sided bone loss. Decision making is more complex in patients with significant humeral or glenoid bone defects or in those who underwent previous instability surgery. Appropriate assessment of the glenoid track is necessary as "off track" lesions typically require treatments beyond arthroscopic labral repair alone. In those with significant humeral or glenoid sided bone loss, the authors recommend three-dimensional computed tomography in addition to magnetic resonance imaging for accurate evaluation. The Glenoid Track Instability Management Score is a useful guide to help direct treatment by using the glenoid track as well as other known risk factors for recurrence. In circumstances with significant glenoid bone loss, typically over 20%, a coracoid transfer such as the Latarjet is recommended. In patients that previously failed a coracoid transfer, the authors recommend a distal tibia allograft; however, distal clavicle and iliac crest autograft have also been reported to have high success rates. In those with large Hill-Sachs lesions, remplissage or bone grafting are recommended. An estimation of the postoperative glenoid track after glenoid bone augmentation is required for appropriate Hill-Sachs lesion treatment. The authors typically recommend against revision instability surgical treatment with arthroscopic repair alone.

Editorial Commentary: Recurrent Anterior Shoulder Instability With Glenoid Bone Loss Requires Restoring the Bone.

The success of treating anterior glenohumeral instability relies on multiple factors, including glenoid bone loss. Subcritical bone loss (<13.5%) has proven again and again to be a critical consideration when treating this problem. This proves more challenging in a population that participates in contact sports. The importance of restoring native anatomy, including the glenoid bone, is critical in ensuring a successful outcome. This is especially true in the setting of a bony Bankart lesion, where merely repairing the soft tissues and ignoring the bony fragment leads to unfavorable results.

Editorial Commentary: Double-Pulley Remplissage Using Transtendon Anchors: Keep It Simple.

A large Hill-Sachs lesion that engages the glenoid rim and predisposes to recurrent anterior instability confers a substantial management challenge. Arthroscopic remplissage, either in isolation or combined with anterior labral repair, gives the arthroscopic surgeon a tool to stabilize the shoulder without reverting to more extensive open procedures or bone block reconstructions. In arthroscopic remplissage, the posterior capsule and infraspinatus are sutured into the humeral defect to limit such engagement between the HilleSachs lesion and the glenoid rim. The double-pulley technique using 2 transtendon anchors makes arthroscopic remplissage technically simpler, and potentially more reproducible, than earlier techniques. As we refine remplissage techniques, we need to further explore issues such as the optimal distance between the 2 anchors (and hence the resultant tendon bridge) as this distance-along with the pliability of the tendon-potentially determines how much compression against the bone can be achieved. Furthermore, as remplissage techniques are proven to be effective in restoring shoulder stability and conferring successful clinical function, there is even more need for high-quality comparative studies to define their role versus that of more extensive open stabilization procedures. Mechanistic studies are also needed to define the fill-effect versus the possible check-rein and neuromuscular control activation components of remplissage.

Glenoid erosion is a risk factor for recurrent instability after Hill-Sachs remplissage.

AIMS: The aim of this study was to identify risk factors for recurrent instability of the shoulder and assess the ability to return to sport in patients with engaging Hill-Sachs lesions treated with arthroscopic Bankart repair and Hill-Sachs remplissage (ABR-HSR). METHODS: This retrospective study included 133 consecutive patients with a mean age of 30 years (14 to 69) who underwent ABR-HSR; 103 (77%) practiced sports before the instability of the shoulder. All had large/deep, engaging Hill-Sachs lesions (Calandra III). Patients were divided into two groups: A (n = 102) with minimal or no (< 10%) glenoid bone loss, and B (n = 31) with subcritical (10% to 20%) glenoid loss. A total of 19 patients (14%) had undergone a previous stabilization, which failed. The primary endpoint was recurrent instability, with a secondary outcome of the ability to return to sport. RESULTS: At a mean follow-up of four years (1.0 to 8.25), ten patients (7.5%) had recurrent instability. Patients in group B had a significantly higher recurrence rate than those in group A (p = 0.001). Using a multivariate logistic regression, the presence of glenoid erosion of > 10% (odds ratio (OR) = 35.13 (95% confidence interval (CI) 8 to 149); p = 0.001) and age < 23 years (OR = 0.89 (0.79 to 0.99); p = 0.038) were associated with a higher risk of recurrent instability. A total of 80 patients (78%) could return to sport, but only 11 athletes (65%) who practiced high-risk (collision or contact-overhead) sports. All seven shoulders which were revised using a Latarjet procedure were stable at a mean final follow-up of 36 months (11 to 57) and returned to sports at the same level. CONCLUSION: Patients with subcritical glenoid bone loss (> 10%) and younger age (≤ 23 years) are at risk of failure and reoperation after ABR-HSR. Furthermore, following this procedure, one-third of athletes practicing high-risk sports are unable to return at their pre-instability level, despite having a stable shoulder. Cite this article: Bone Joint J 2021;103-B(4):718-724.

The Bony Bankart: Clinical and Technical Considerations.

Fractures of the anteroinferior aspect of the glenoid rim, known as a bony Bankart lesions, can occur frequently in the setting of traumatic anterior shoulder dislocation. If these lesions are large and are left untreated in active patients, then recurrent glenohumeral instability due to glenoid bone deficiency may occur. Therefore, the clinician must recognize these lesions when they occur and provide appropriate treatment to restore physiological joint stability. This article aims to provide an overview focusing on clinical and technical considerations in the diagnosis and treatment of bony Bankart lesions.

Mechanism and patterns of bone loss in patients with anterior shoulder dislocation.

BACKGROUND: Bony defects are common injuries associated with anterior shoulder dislocation. It is generally thought that these bony defects are created at the time of dislocation. However, there have been no biomechanical reports demonstrating the exact time point when these lesions occur. The purpose of this study was to clarify when, how, and which types of bony defects were created during experimental dislocation in cadaveric shoulders. METHODS: Fifteen fresh-frozen cadaveric shoulders (mean age at the time of death, 79 years) were fixed in a custom testing machine. First, the glenohumeral joint was inspected by arthroscopy. Then, the arm was held at 60° of abduction and maximum external rotation and was manually extended horizontally under fluoroscopy until an anterior dislocation occurred. Next, a force of 800 N was applied to a Kirschner wire inserted in the humeral head in the direction of the pectoralis major with use of an air cylinder. We waited until the arm came to equilibrium under this condition. Finally, the glenohumeral joint was arthroscopically examined. We further performed x-ray micro-computed tomography and histologic examination in 1 shoulder with a bipolar lesion. RESULTS: After the anterior dislocation, a Bankart lesion was created in 9 of 15 shoulders and a fragment-type glenoid defect (avulsion fracture) was created in 4. A Hill-Sachs lesion, on the other hand, was not observed after the dislocation. The equilibrium arm position was 40° ± 17° in flexion, 45° ± 22° in abduction, and 27° ± 19° in external rotation. In this arm position, newly created lesions were Hill-Sachs lesions in 6 shoulders and erosion-type glenoid defects (compression fracture) in 7. Micro-computed tomography, performed in a single specimen, showed a flattened anterior glenoid rim with collapse of trabecular bone. Histologic analysis of nondecalcified sections using hematoxylin-eosin staining indicated that the anterior rim of the glenoid was compressed and flattened. The cortex of the anterior glenoid rim could be clearly observed. CONCLUSION: The fragment-type glenoid defect (avulsion fracture) was observed at the time of dislocation, whereas the erosion-type defect (compression fracture) was observed when the arm came to equilibrium in the midrange of motion. Hill-Sachs lesions were created not at the time of dislocation but after the arm came to equilibrium.

The Evaluation and Management of the Failed Primary Arthroscopic Bankart Repair.

Primary arthroscopic Bankart repair is a common procedure that is increasing in popularity; however, failure rates can approach up to 6% to 30%. Factors commonly attributed to failure include repeat trauma, poor or incomplete surgical technique, humeral and/or glenoid bone loss, hyperlaxity, or a failure to identify and address rare pathology such as a humeral avulsion of the glenohumeral ligament lesion. A thorough clinical and radiographic assessment may provide insight into the etiology, which can assist the clinician in making treatment recommendations. Surgical management of a failed primary arthroscopic Bankart repair without bone loss can include revision arthroscopic repair or open repair; however, in the setting of bone loss, the anterior-inferior glenoid can be reconstructed using a coracoid transfer, tricortical iliac crest, or structural allograft, whereas posterolateral humeral head bone loss (the Hill-Sachs defect) can be addressed with remplissage, structural allograft, or partial humeral head implant. In addition to the technical demands of revision stabilization surgery, patient and procedure selection to optimize outcomes can be challenging. This review will focus on the etiology, evaluation, and management of patients after a failed primary arthroscopic Bankart repair, including an evidence-based treatment algorithm.

When to Abandon the Arthroscopic Bankart Repair: A Systematic Review.

CONTEXT: Bone loss is a major factor in determining surgical choice in patients with anterior glenohumeral instability. Although bone loss has been described, there is no consensus on glenoid, humeral head, and bipolar bone loss limits for which arthroscopic-only management with Bankart repair can be performed. OBJECTIVE: To provide guidelines for selecting a more complex repair or reconstruction (in lieu of arthroscopic-only Bankart repair) in the setting of glenohumeral instability based on available literature. DATA SOURCES: An electronic search of the literature for the period from 2000 to 2019 was performed using PubMed (MEDLINE). STUDY SELECTION: Studies were included if they quantified bone loss (humeral head or glenoid) in the setting of anterior instability treated with arthroscopic Bankart repair. STUDY DESIGN: Systematic review. LEVEL OF EVIDENCE: Level 4. DATA EXTRACTION: Study design, level of evidence, patient demographics, follow-up, recurrence rates, and measures of bone loss (glenoid, humeral head, bipolar). RESULTS: A total of 14 studies met the inclusion criteria. Of these, 10 measured glenoid bone loss, 5 measured humeral head bone loss, and 2 measured "tracking" without explicit measurement of humeral head bone loss. Measurement techniques for glenoid and humeral head bone loss varied widely. Recommendations for maximum glenoid bone loss for arthroscopic repair were largely <15% of glenoid width in recent studies. Recommendations regarding humeral head loss were more variable (many authors providing only qualitative descriptions) with increasing attention on glenohumeral tracking. CONCLUSION: It is essential that a standardized method of glenoid and humeral head bone loss measurements be performed preoperatively to assess which patients will have successful stabilization after arthroscopic Bankart repair. Glenoid bone loss should be <15%, and humeral head lesions should be "on track" if an arthroscopic-only Bankart is planned. If there is greater bone loss, adjunct or open procedures should be performed.

Risk Factors for Intra-articular Bone and Cartilage Lesions in Patients Undergoing Surgical Treatment for Posterior Instability.

BACKGROUND: Patients with posterior shoulder instability may have bone and cartilage lesions (BCLs) in addition to capsulolabral injuries, although the risk factors for these intra-articular lesions are unclear. HYPOTHESIS: We hypothesized that patients with posterior instability who had a greater number of instability events would have a higher rate of BCLs compared with patients who had fewer instability episodes. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Data from the Multicenter Orthopaedic Outcomes Network (MOON) Shoulder Group instability patient cohort were analyzed. Patients aged 12 to 99 years undergoing primary surgical treatment for shoulder instability were included. The glenohumeral joint was evaluated by the treating surgeon at the time of surgery, and patients were classified as having a BCL if they had any grade 3 or 4 glenoid or humeral cartilage lesion, reverse Hill-Sachs lesion, bony Bankart lesion, or glenoid bone loss. The effects of the number of instability events on the presence of BCLs was investigated by use of Fisher exact tests. Logistic regression modeling was performed to investigate the independent contributions of demographic variables and injury-specific variables to the likelihood of having a BCL. Significance was defined as P < .05. RESULTS: We identified 271 patients (223 male) for analysis. Bone and cartilage lesions were identified in 54 patients (19.9%) at the time of surgical treatment. A glenoid cartilage injury was most common and was identified in 28 patients (10.3%). A significant difference was noted between the number of instability events and the presence of BCLs (P = .025), with the highest rate observed in patients with 2 to 5 instability events (32.3%). Multivariate logistic regression modeling indicated that increasing age (P = .019) and 2 to 5 reported instability events (P = .001) were significant independent predictors of the presence of BCLs. For bone lesions alone, the number of instability events was the only significant independent predictor; increased risk of bone lesion was present for patients with 1 instability event (OR, 6.1; P = .012), patients with 2 to 5 instability events (OR, 4.2; P = .033), and patients with more than 5 instability events (OR, 6.0; P = .011). CONCLUSION: Bone and cartilage lesions are seen significantly more frequently with increasing patient age and in patients with 2 to 5 instability events. Early surgical stabilization for posterior instability may be considered to potentially limit the extent of associated intra-articular injury. The group of patients with more than 5 instability events may represent a different pathological condition, as this group showed a decrease in the likelihood of cartilage injury, although not bony injury.

Peripheral-Track and Central-Track Hill-Sachs Lesions: A New Concept of Assessing an On-Track Lesion.

BACKGROUND: It has been demonstrated biomechanically that 25% is a critical size defect of the glenoid. However, a recent clinical study reported that a bone loss between 13.5% and 20% (subcritical bone loss) led to impairment of quality of life but not a recurrence of instability. PURPOSE: To clarify whether a subcritical bone loss exists in assessing a Hill-Sachs lesion via a disease-specific quality of life questionnaire. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Fifty patients (mean age, 27 years) with <25% glenoid defect who were treated with arthroscopic Bankart repair for recurrent anterior dislocation were assessed at a mean follow-up of 28 months. All had an on-track Hill-Sachs lesion. The Western Ontario Shoulder Instability Index (WOSI) and Rowe scores were used for the clinical evaluation. The Hill-Sachs interval was measured on 3-dimensional computed tomography images and divided by the glenoid track width, defined as the Hill-Sachs occupancy (in percentages). The glenoid track was divided into 4 zones based on the percentage of the Hill-Sachs occupancy: zone 1, <25%; zone 2, 25% to <50%; zone 3, 50% to <75%; and zone 4, ≥75%. RESULTS: The recurrence rate was 6% (3 of 50 shoulders). The Rowe score significantly improved from 45.2 ± 4.7 (mean ± SD) preoperatively to 92.3 ± 6.5 at the final follow-up (P < .05). The WOSI score also significantly increased from 46.6% ± 19.3% preoperatively to 72.3% ± 21.0% at the final follow-up (P < .001). The WOSI score of patients in zone 4 (peripheral-track lesion) (n = 10) was significantly lower than those in the other zones (central-track lesion) (P = .0379). Of the 10 patients with the peripheral-track lesion, 5 had a <40% WOSI score, similar to the preoperative WOSI score (46.6%). CONCLUSION: Patients with on-track lesions can be divided into 2 subgroups: those with the Hill-Sachs occupancy ≥75% (peripheral-track lesion) showed significantly worse WOSI score without recurrent instability events than those with the Hill-Sacks occupancy <75% (central-track lesion).

The 6-O'clock Anchor Increases Labral Repair Strength in a Biomechanical Shoulder Instability Model.

PURPOSE: To characterize the additive effect of a 6-o'clock anchor in the stabilization of a Bankart lesion. METHODS: Twelve cadaveric shoulders were tested on a 6-df robotic musculoskeletal simulator to measure the peak resistance force due to anterior displacement of 1 cm. The rotator cuff muscles were loaded dynamically. The test conditions consisted of the intact shoulder, Bankart lesion, Bankart repair (3-, 4-, and 5-o'clock anchors), and Bankart repair with the addition of a 6-o'clock anchor. A 13% anterior bone defect was then created, and all conditions were repeated. Repeated-measures analysis of variance was performed. RESULTS: In the group with no bone loss, the addition of a 6-o'clock anchor yielded the highest peak resistance force (52.8 N; standard deviation [SD], 4.5 N), and its peak force was significantly greater than that of the standard Bankart repair by 15.8% (7.2 N, P = .003). With subcritical glenoid bone loss, the repair with the addition of a 6-o'clock anchor (peak force, 52.6 N; SD, 6.1 N; P = .006) had a significantly higher peak resistance force than the group with bone loss with a Bankart lesion (35.2 N; SD, 5.8 N). Although the 6-o'clock anchor did increase the strength of the standard repair by 6.7%, this was not statistically significant (P = .9) in the bone loss model. CONCLUSIONS: The addition of a 6-o'clock suture anchor to a 3-anchor Bankart repair increases the peak resistance force to displacement in a biomechanical model, although this effect is lost with subcritical bone loss. CLINICAL RELEVANCE: This study provides surgeons with essential biomechanical data to aid in the selection of the repair configuration.

The Number of Injury Events Associated With the Critical Size of Bipolar Bone Defects in Rugby Players With Traumatic Anterior Shoulder Instability.

BACKGROUND: The size of a glenoid bone defect is responsible for reduction in shoulder stability and is correlated with the number of instability events. Biomechanical studies have suggested that it should be considered concomitantly with the Hill-Sachs lesion as "bipolar" bone defects for assessing structural degradation, but the definitive number of instability events associated with the critical size has not been investigated. PURPOSE: To (1) confirm that the number of instability events is the predictor of a critical size of bipolar bone defects and (2) demonstrate the cutoff value of the number of instability events for these defects in rugby players with traumatic anterior shoulder instability. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: One-hundred forty-four rugby players with anterior shoulder instability underwent morphologic evaluation for glenoid and Hill-Sachs lesions by computed tomography and determination of the critical (a glenoid bone defect of ≥25% or an off-track Hill-Sachs lesion) and subcritical (a glenoid bone defect of ≥13.5%) size of bipolar bone defects. In the primary analysis, the prevalence of the critical and subcritical size of bipolar bone defects was investigated. In the secondary analysis, the authors explored the predictors for these bone defects and determined the cutoff value correlating with the critical and subcritical size of bipolar bone defects by applying receiver operating characteristic curves. RESULTS: The primary analysis revealed that the prevalence of critical and subcritical size of bipolar bone defects was 20.8% and 61.8% of 144 shoulders, respectively. In the secondary analysis, multiple logistic regression analysis demonstrated that the total number of shoulder instability events and dominant shoulder were the significant factors associated with the critical and subcritical size of bipolar bone defects. The cutoff value for the number of instability events that correlated with critical bipolar bone defects was 6 for the dominant and 9 for the nondominant shoulder, whereas it was 4 for the dominant and 5 for the nondominant shoulder for subcritical bipolar bone defects. CONCLUSION: The number of shoulder instability events and the dominant shoulder were the predictors for the critical and subcritical size of bipolar bone defects for a shoulder with traumatic instability. Four injury events should herald caution when treating rugby players with shoulder instability.

In Which Arm Position Is a Hill-Sachs Lesion Created?

BACKGROUND: It has been believed that a Hill-Sachs lesion (HSL) is created with the arm in abduction and external rotation at the time of dislocation. However, no studies have clarified the arm position in which an HSL is created. PURPOSE: To determine the arm position in which an HSL is created. STUDY DESIGN: Descriptive laboratory study. METHODS: The computed tomography images of 100 shoulders of 100 patients (72 males and 28 females; mean age, 30 years old) with recurrent anterior dislocation of the shoulder were investigated using an image analyzing software. Three-dimensional surface bone models of the scapula and humerus were created separately. The humerus was moved so that the HSL perfectly fit the anterior rim of the glenoid. This arm position was recorded 3-dimensionally. RESULTS: Considering the scapulohumeral rhythm, the average arm position in which the HSL and the anterior glenoid rim best fit was 74° of abduction, 27° of external rotation, and 3° of horizontal flexion relative to the trunk. CONCLUSION: The arm position when an HSL and the anterior glenoid rim best fit is 74° of abduction, 27° of external rotation, and 3° of horizontal flexion, which seems to be the arm position when the HSL has been created. This result suggests 2 possibilities: dislocation occurred in this midrange position or HSL was not created at the time of dislocation but later in the mid-range of motion. However, as we have no information on the arm position at the time of dislocation, we cannot conclude which of these possibilities is true in our study. CLINICAL RELEVANCE: This study gives us a better understanding of the timing of HSL occurrence. Shoulder dislocation may occur at the end range of motion or in the mid-range of motion, but an HSL is created in the mid-range of motion.