Bipolar Bone Defects Research Articles

SHOULDER INSTABILITY IN SOUTHEAST ASIA: ARE WE THAT DIFFERENT? ALGORITHM AND TREATMENT STRATEGIES IN DEALING WITH MINOR AND MAJOR BONE LOSS

Concepts in glenoid tracking and treatment strategies of glenoid bone loss are well established. Initial observations in our practice in Singapore showed few patients with major bone loss requiring glenoid reconstructions. This led us to investigate the incidence of and the extent of bone loss in our patients with shoulder instability. Our study revealed bony Bankart lesions were seen in 46% of our patients but glenoid bone loss measured only 6–10% of the glenoid surface. In the same study we found that arthroscopic labral repair with capsular plication and Mason-Ellen suturing (Hybrid technique) was sufficient to stabilise patients with bipolar bone defects and minor glenoid bone loss. This led us to develop the concept of minor bone loss and a new algorithm.Our algorithm and strategies to deal with major bone loss will also be discussed, and techniques & outcomes of Arthroscopic Bony Bankart repair, Arthroscopic Glenoid Reconstruction and Arthroscopic Remplissage procedures will be shown.

Analysis of Bipolar Bone defects Pattern in Anterior Shoulder Instability

Analysis of Bipolar Bone defects Pattern in Anterior Shoulder Instability

Arthroscopic Autologous Iliac Crest Grafting Results in Similar Outcomes and Low Recurrence Compared to Remplissage Plus Bankart Repair for Anterior Shoulder Instability With Bipolar Bone Defects

To compare the functional outcomes, range of motion (ROM), recurrence rates, and complication rates of arthroscopic autologous iliac crest grafting (AICG) and Remplissage plus Bankart repair (RB) for anterior shoulder instability with bipolar bone defects. This study enrolled patients undergoing arthroscopic AICG or RB with 13.5-25% glenoid bone defect combined with Hill-Sachs lesion between January 2013 and April 2020, who had a minimum 2-year follow-up. Patient-reported outcomes were evaluated by Subjective Shoulder Value (SSV), Oxford Shoulder Instability Score (OSIS), Rowe score, Constant score, and visual analog scale (VAS) for pain. Active ROM, return to sports, recurrence, self-reported apprehension, and complications were recorded. This study included 60 patients, including 28 AICG (Group A) and 32 RB (Group R). Mean glenoid bone defect was similar (17.7% ± 3.1% vs 16.6% ± 2.4%; P= .122). Both groups showed significant postoperative improvement in Rowe score, SSV, OSIS, and Constant score. No significant difference was found in postoperative Rowe Score (87.7 vs 85.2; P= .198). A total of 20/28 (71.4%) patients in Group A versus 26/32 (81.3%) patients in Group R met the Patient Acceptable Symptomatic State determined by VAS pain score (P= .370). Both groups showed high return-to-sports rates (67.8% vs 71.8%; P= .735) and slightly decreased ROM. There were two cases of recurrence in Group A versus one in Group R (P= .594). Group R had insignificantly higher positive self-reported apprehension rate (40.6% vs 17.9%; P= .055). For anterior shoulder instability with bipolar bone defects, both arthroscopic AICG and RB can result in satisfactory clinical outcomes, good postoperative ROM, and low recurrence and complication rates. Level III, retrospective cohort study.

Recurrence of glenohumeral instability in patients with isolated rotator cuff repair after a traumatic shoulder dislocation.

The primary objective of this study was to assess the incidence of recurrent glenohumeral instability in patients over 40years with isolated rotator cuff (RC) repair for traumatic shoulder dislocation. The secondary objectives were to identify risk factors for glenohumeral recurrence after RC repair and to describe the causes and incidences of re-intervention. In this retrospective cohort study, data of consecutive patients at a single trauma center between January 2014 and July 2019 were reviewed, and 84 patients with a mean age of 57 (range: 40-75) years and follow-up duration of 3.9 (2-6) years were included. The inclusion criteria were as follows: first traumatic anterior shoulder dislocation, reparable RC tear, primary arthroscopic RC repair, no labral or bony Bankart lesion repair, and at least 2years of follow-up. Patients less than 40years of age were excluded. Shoulder instability recurrences and surgical reinterventions were reviewed with medical records. Statistical analysis was performed for qualitative variables using the Chi-squared test. Statistical significance was set at P ≤ 0.05. There was one patient with a redislocation episode (1.2%) at 2.5years after surgery, who was surgically treated. Age, subscapular tears, bony Bankart injuries, humeral defects, and associated neurological injuries were not risk factors for recurrence in this study. Ten patients (11.9%) required reintervention. Nine patients (10.7%) re-tore their RCs. Recurrent glenohumeral instability in active patients over 40years with isolated RC repair after traumatic shoulder dislocation was infrequent, despite the incidence of significant Hill-Sachs defects, anterior glenoid defects, bipolar bone defects, size of the RC injury, and tendon re-tears. The incidence of re-interventions was 11.9%, with symptomatic RC retear as the main cause.

Long-term outcomes of arthroscopic Bankart repair and Hill-Sachs remplissage for bipolar bone defects.

To evaluate long-term results after arthroscopic Bankart repair and Hill-Sachs remplissage (BHSR) in bipolar bone defects with less than 20% of glenoid bone loss (GBL) and to analyse risk factors for recurrent dislocation. From 2009-2012, 43 patients with recurrent anterior shoulder instability were treated with BHSR. Inclusion criteria were GBL < 20% and minimum of 4-yearfollow-up. There were 35 males and 8 females with a mean age of 29years (range 16-53). The mean ISIS score was 3.6 (range 2-6). Patients were evaluated for recurrence, range of motion and functional outcomes (Walch-Duplay and Rowe score). Post-operative MRI was performed at least 6months after surgery to evaluate infraspinatus capsulotenodesis healing. Glenoid track was assessed retrospectively from pre-operative computed tomography. Mean follow-up was 7.3years (range 4-11). At the last follow-up, good to excellent outcomes were reported in 86% of patients. Average post-operative Walch-Duplay was 87.9 (range 75-100) and ROWE 93.7 (range 70-100). Infraspinatus capsulotenodesis healing was achieved in 86%. The rate of recurrence and revision surgery was 9.3% and 13.9%, respectively. Recurrence was associated with higher ISIS score (p = 0.0191) and lower age at surgery (p = 0.0227). Four (9.3%) Hill-Sachs lesions were considered off-track. The presence of off-track Hill-Sachs was associated with higher risk of recurrence (p < 0.00001). Arthroscopic BHSR improves shoulder instability in the setting of bipolar bone defects with less than 20% of GBL. Patient-related factors and pre-operative glenoid track should be taken into consideration to reduce the risk of recurrence.

Association Between Excessive Joint Laxity and a Wider Hill-Sachs Lesion in Anterior Shoulder Instability

Background: Excessive general joint laxity, a negative prognostic factor in joint instability, has not been studied to determine its relationship with bipolar bone loss in anterior shoulder instability. Purpose/Hypothesis: This study aimed to investigate the characteristics of bipolar bone defects in the presence of excessive joint laxity and the clinical outcomes based on the on-track/off-track theory. We hypothesized that (1) patients with excessive joint laxity might have less significant bipolar bone defects compared with those without excessive joint laxity and (2) no significant difference would be found in the clinical outcomes, including recurrence rate. Study Design: Cohort study; Level of evidence, 3. Methods: This study included 81 patients who had undergone arthroscopic Bankart repair, with (group L; n = 33) or without (group N; n = 48) excessive joint laxity. The presence of excessive joint laxity was defined as a score of ≥4 using Beighton and Horan criteria preoperatively. Bipolar bone lesions were assessed using preoperative 3-dimensional computed tomography. Additional remplissage was performed for cases with off-track or positive engagement test in borderline on-track lesions. The functional outcomes at the 2-year follow-up were assessed using the recurrence rate, Subjective Shoulder Value, Rowe score, University of California Los Angeles shoulder score, active range of motion, and the sports/recreation activity level. Results: No significant difference was found in the glenoid bone defect between groups (14.1%, group L; 14.4%, group N). Off-track lesions were identified in 39.4% (13/33) of group L and 14.6% (7/48) of group N (P = .011). The mean Hill-Sachs interval to glenoid track ratio was 83.1% in group L and 75.2% in group N (P = .021). Additional remplissage procedures were more frequently performed in group L (48.5%; 16/33) than in group N (16.7%; 8/48) (P = .002). However, no significant difference was observed in the shoulder functional scores and recurrence rates between the groups. Conclusion: Patients with anterior shoulder instability and excessive joint laxity had significantly wider Hill-Sachs lesions and more off-track lesions than did those with normal joint laxity despite the lack of a significant difference in the glenoid bone defect. However, these differences in the Hill-Sachs lesion were not related to differences in the functional outcomes between the groups.

Hill-Sachs Remplissage Procedure and its Role in Arthroscopic Stabilisation of the Shoulder

The arthroscopic Hill-Sachs Remplissage procedure was first described in 2004 and published in 2008. It consists of an arthroscopic posterior capsulodesis combined with an infraspinatus tenodesis to achieve a “filling in” effect of posterior humeral head defects. The technique was put forward as a solution to high rates of Bankart repair failure, in the presence of large Hill-Sachs lesions. We describe the evolution of the technique and its outcomes and report on the evolving surgical indications over the last decade in response to new paradigm shifts. Due to a better understanding of the pathophysiology of shoulder instability, emphasis was given to both Bankart soft tissue repair and to the associated bony injuries, accounting for both glenoid and humeral head (bipolar) bone loss. We present the transition from the concept of “engaging” Hill-Sachs lesions to the concept of “on-track” / “off-track” lesions and the current role of Remplissage in shoulder instability surgery which remains paramount. We believe that in view of the critical role of bipolar bone defects in shoulder instability, preoperative magnetic resonance imaging assessment of the glenoid track of Hill-Sachs lesions is becoming increasingly important in preoperative planning. This allows the orthopaedic surgeon to detect an “off-track” lesion, select the appropriate surgical technique and improve surgical outcomes.

Bipolar Bone Defects in Shoulders With Primary Instability: Dislocation Versus Subluxation.

Background:In shoulders with traumatic anterior instability, a bipolar bone defect has been recognized as an important indicator of the prognosis.Purpose:To investigate bipolar bone defects at primary instability and compare the difference between dislocation and subluxation.Study Design:Cohort study; Level of evidence, 3.Methods:There were 156 shoulders (156 patients) including 91 shoulders with dislocation and 65 shoulders with subluxation. Glenoid defects and Hill-Sachs lesions were classified into 5 size categories on 3-dimensional computed tomography (CT) scans and were allocated scores ranging from 0 (no defect) to 4 points (very large defect). To assess the combined size of the glenoid defect and Hill-Sachs lesion, the scores for both lesions were summed (range, 0-8 points). Patients in the dislocation and subluxation groups were compared regarding the prevalence of a glenoid defect, a bone fragment of bony Bankart lesion, a Hill-Sachs lesion, a bipolar bone defect, and an off-track Hill-Sachs lesion. Then, the combined size of the bipolar bone defects was compared between the dislocation and subluxation groups and among patients stratified by age at the time of CT scanning (<20, 20-29, and ≥30 years).Results:Hill-Sachs lesions were observed more frequently in the dislocation group (75.8%) compared with the subluxation group (27.7%; P < .001), whereas the prevalence of glenoid defects was not significantly different between groups (36.3% vs 29.2%, respectively; P = .393). The combined defect size was significantly larger in the dislocation versus subluxation group (mean ± SD combined defect score, 2.1 ± 1.6 vs 0.8 ± 0.9 points, respectively; P < .001) due to a larger Hill-Sachs lesion at dislocation than subluxation (glenoid defect score, 0.5 ± 0.9 vs 0.3 ± 0.6 points [P = .112]; Hill-Sachs lesion score, 1.6 ± 1.2 vs 0.4 ± 0.7 points [P < .001]). Combined defect size was larger in older patients than younger patients in the setting of dislocation (combined defect score, <20 years, 1.6 ± 1.2 points; 20-29 years, 1.9 ± 1.5 points; ≥30 years, 3.4 ± 1.6 points; P < .001) but was not different in the setting of subluxation (0.8 ± 1.0, 0.7 ± 0.9, and 0.8 ± 0.8 points, respectively; P = .885). An off-track Hill-Sachs lesion was observed in 2 older patients with dislocation but was not observed in shoulders with subluxation.Conclusion:The bipolar bone defect was significantly more frequent, and the combined size was greater in shoulders with primary dislocation and in older patients (≥30 years).

Arthroscopic repair is sufficient for treating recurrent shoulder instability in patients with bipolar bone defects and minor glenoid bone loss

Arthroscopic repair is sufficient for treating recurrent shoulder instability in patients with bipolar bone defects and minor glenoid bone loss

Effects of Glenoid and Humeral Bone Defects on Recurrent Anterior Instability of the Shoulder.

For proper treatment of recurrent anterior instability of the shoulder with a bone defect, the defect size should be assessed preoperatively with three-dimensional computed tomography or magnetic resonance imaging. In general, the risk of postoperative recurrence of instability is estimated on the basis of preoperative imaging of bipolar bone defects: more than 20%–25% glenoid bone loss and off-track Hill-Sachs lesions have been considered risk factors for recurrence. In patients with a glenoid bone defect more than 20%–25%, a bone graft procedure, such as the Latarjet procedure, is preferred regardless of the glenoid track concept, because compared with arthroscopic stabilization procedure, it provides greater postoperative stability. For patients with a borderline glenoid bone defect (around 20%), surgeons should discuss surgical options with the patients, considering their demand and physical activity level. In addition, the surgeon should take care to prevent postoperative instability and long-term complications. Arthroscopic soft-tissue reconstruction including labral repair and capsular plication combined with the additional remplissage procedure is an anatomical procedure and could be considered as one of the primary treatment methods for patients with glenoid bone defects around 20%. Therefore, treatment strategies for recurrent anterior shoulder instability combined with bone defects should be determined more flexibly on the basis of the patient's individual condition.

Un échec préalable de « Bankart » arthroscopique est un facteur indépendant de résultat inférieur après intervention de Latarjet

BackgroundThere is limited evidence that the Latarjet procedure has a worse outcome as a revision operation, after a failed stabilization surgery, compared with when it is the primary procedure for posttraumatic antero-inferior instability of the shoulder joint. PurposeTo compare the results from Latarjet as a primary operation vs. revision surgery after a failed arthroscopic Bankart repair for posttraumatic antero-inferior shoulder instability. In addition, to assess the effect of preoperative bony pathology on outcome. Patients and methodsNinety-nine patients who underwent the Latarjet procedure (47 primary, 52 revision after failed Bankart repair) were analyzed after an average of 3.8 (SD 2.3, range 1–11) years of follow-up. All patients underwent either computed tomography or magnetic resonance imaging preoperatively. Glenoid and humeral bone defects were measured to assess whether the Hill-Sachs lesion was on- or off-track. Clinical outcome measures included the Western Ontario Shoulder Instability Index (WOSI), subjective shoulder value (SSV), and recurrence of instability (dislocation, subluxation, or any perception of instability). ResultsThere were no cases of recurrent dislocation in either group. Four patients in the primary surgery group and 13 in the revision group had at least one subluxation or perception of instability after the Latarjet procedure. Patients with a previous arthroscopic Bankart repair had worse outcomes than those undergoing primary Latarjet when assessed by the WOSI: 76 (SD 22) vs. 85 (SD 15), difference in means −9 (95 % CI −17 to −1, p=0.02); SSV: 80 (SD 18) vs. 88 (SD 13), difference in means −8 (95 % CI −15 to −2, p=0.01); and the recurrence percentage (25 % vs. 9 %, p=0.03). A multivariate linear regression model adjusted for the length of follow-up, glenoid bone defect size, Hill-Sachs lesion size, and the frequency of preoperative bipolar bone defects (on/off track Hill-Sachs lesions) further increased the difference in WOSI to −12 (95 % CI −21 to −4, p=0.005). DiscussionA previous failed arthroscopic Bankart repair was a significant independent risk factor for inferior outcome. Preoperative bony pathology did not explain the worse outcome from the revision vs. primary Latarjet procedure. Level of evidenceIV, cohort observational study.

Postoperative Recurrence of Instability After Arthroscopic Bankart Repair for Shoulders With Primary Instability Compared With Recurrent Instability: Influence of Bipolar Bone Defect Size

Background: In shoulders with traumatic anterior instability, a bipolar bone defect has recently been recognized as an important indicator of the prognosis. Purpose: To investigate the influence of bipolar bone defects on postoperative recurrence after arthroscopic Bankart repair performed at primary instability. Study Design: Cohort study; Level of evidence, 3. Methods: The study group consisted of 45 patients (45 shoulders) who underwent arthroscopic Bankart repair at primary instability before recurrence and were followed for at least 2 years. The control group consisted of 95 patients (95 shoulders) with recurrent instability who underwent Bankart repair and were followed for at least 2 years. Glenoid defects and Hill-Sachs lesions were classified into 5 size categories on 3-dimensional computed tomography and were allocated scores ranging from 0 for no defect to 4 for the largest defect. The shoulders were classified according to the total score for both lesions (0-8 points). The postoperative recurrence rate was investigated for each score of bipolar bone defects and was compared between patients with primary instability and patients with recurrent instability. The same analysis was performed for the age at operation (<20 years, 20-29 years, or ≥30 years) and for the presence of an off-track Hill-Sachs lesion. Results: Bipolar bone defects were smaller in shoulders with primary instability (mean ± SD defect score, 1.4 ± 1.5 points) than in those with recurrent instability (3.6 ± 1.9 points) and were larger in older patients than in younger patients at the time of primary instability. The postoperative recurrence rate was low (6.7%) in shoulders with primary instability regardless of the size of the bipolar bone defect and the patient’s age, whereas the postoperative recurrence rate was high (23.2%) in shoulders with recurrent instability, especially among patients younger than 20 years with bipolar bone defects of 2 points or greater. An off-track Hill-Sachs lesion was found in only 1 patient in the oldest age group (2.2%) at primary instability, but it was found in 19 patients (20%) at recurrent instability, including 14 patients younger than 30 years. Among patients with an off-track lesion, the postoperative recurrence rate was significantly higher in patients younger than 20 years with recurrent instability (recurrence rates: <20 years, 71.4%; 20-29 years, 14.3%; ≥30 years, 0%). Conclusion: The recurrence rate was consistently low in patients with primary instability and was significantly influenced by bipolar bone defect size and patient age in patients with recurrent instability.

Changes of Bipolar Bone Defect Size After Arthroscopic Bankart Repair for Traumatic Anterior Shoulder Instability: Evaluation Using a Scoring System and Influence on Postoperative Recurrence.

Background:The combination of a glenoid defect and a Hill-Sachs lesion in shoulders with traumatic anterior instability has been termed bipolar bone loss, and the preoperative size of these lesions has been reported to influence postoperative recurrence of instability after arthroscopic Bankart repair.Purpose:To investigate the influence of postoperative bipolar bone defect size on postoperative recurrence of instability.Study Design:Cohort study; Level of evidence, 3.Methods:A total of 64 male collision/contact athletes (69 shoulders) were evaluated for a minimum of 2 years after surgery, and the pre- and postoperative sizes of both lesions (glenoid defect and Hill-Sachs) were evaluated retrospectively with 3-dimensional computed tomography. The sports played by the athletes included rugby (n = 28 shoulders), American football (n = 24 shoulders), and other collision/contact sports (n = 17 shoulders). Glenoid defects and Hill-Sachs lesions were classified into 5 size categories and assigned scores from 0 (no defect) to 4 (very large defect). Patients were then classified according to the total score (sum of the scores for both lesions). The influence of pre- and postoperative bipolar bone defect sizes on recurrence of instability was investigated by using the total scores for bipolar bone defects. The influence of postoperative glenoid morphology (normal preoperative glenoid, preoperative glenoid erosion, bone union after arthroscopic bony Bankart repair [ABBR], or nonunion after ABBR) was also investigated, as well as changes in shoulders with a preoperative off-track Hill-Sachs lesion.Results:Of 69 shoulders, 15 (21.7%) developed recurrent instability after surgery. The postoperative recurrence rate was 0% in shoulders with a total score ≤1, while the recurrence rate was consistently higher in shoulders with a total score ≥2 at both pre- and postoperative evaluation (mean, 28.8% and 32.6%, respectively). Postoperative recurrence was uncommon when there was a normal preoperative glenoid or bone union after ABBR, while it was frequent in shoulders with preoperative glenoid erosion or shoulders with nonunion after ABBR and a total score ≥2. An off-track lesion was recognized in 9 shoulders preoperatively. It was transformed to on-track lesions in 4 of the 5 shoulders showing bone union after ABBR, and there was no recurrence in the 5 shoulders with bone union. In contrast, postoperative recurrence of instability occurred in 3 of the 4 shoulders without bone union.Conclusion:Postoperative recurrence was influenced by the pre- and postoperative size of bipolar bone defects. Recurrence was uncommon if bone union was achieved after ABBR, even if there had been an off-track lesion preoperatively.

Previous arthroscopic Bankart repair is an independent risk factor for an inferior outcome after Latarjet procedure

BackgroundThere is limited evidence that the Latarjet procedure has a worse outcome as a revision operation, after a failed stabilization surgery, compared with when it is the primary procedure for posttraumatic anteroinferior instability of the shoulder joint. PurposeTo compare the results from Latarjet as a primary operation vs. revision surgery after a failed arthroscopic Bankart repair for posttraumatic anteroinferior shoulder instability. In addition, to assess the effect of preoperative bony pathology on outcome. Patients and methodsNinety-nine patients who underwent the Latarjet procedure (47 primary, 52 revision after failed Bankart repair) were analyzed after an average of 3.8 (SD 2.3, range 1–11) years of follow-up. All patients underwent either computed tomography or magnetic resonance imaging preoperatively. Glenoid and humeral bone defects were measured to assess whether the Hill-Sachs lesion was on- or off-track. Clinical outcome measures included the Western Ontario Shoulder Instability Index (WOSI), subjective shoulder value (SSV), and recurrence of instability (dislocation, subluxation, or any perception of instability). ResultsThere were no cases of recurrent dislocation in either group. Four patients in the primary surgery group and 13 in the revision group had at least one subluxation or perception of instability after the Latarjet procedure. Patients with a previous arthroscopic Bankart repair had worse outcomes than those undergoing primary Latarjet when assessed by the WOSI: 76 (SD 22) vs. 85 (SD 15), difference in means −9 (95% CI −17 to −1, p=0.02); SSV: 80 (SD 18) vs. 88 (SD 13), difference in means −8 (95% CI −15 to −2, p=0.01); and the recurrence percentage (25% vs. 9%, p=0.03). A multivariate linear regression model adjusted for the length of follow-up, glenoid bone defect size, Hill-Sachs lesion size, and the frequency of preoperative bipolar bone defects (on/off track Hill-Sachs lesions) further increased the difference in WOSI to −12 (95% CI −21 to −4, p=0.005). DiscussionA previous failed arthroscopic Bankart repair was a significant independent risk factor for inferior outcome. Preoperative bony pathology did not explain the worse outcome from the revision vs. primary Latarjet procedure. Level of evidenceIV, cohort observational study.

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.

The Development Process of Bipolar Bone Defects From Primary to Recurrent Instability in Shoulders With Traumatic Anterior Instability

Background: Recurrence of glenohumeral joint instability after primary traumatic anterior instability is not rare, and bipolar bone loss is one of the most critical factors for recurrent instability, but the development process of bipolar bone defects is still unclear. Purpose: To investigate the development process of bipolar bone defects from primary to recurrent instability among shoulders with traumatic anterior instability evaluated at least twice by computed tomography (CT). Study Design: Case series; Level of evidence, 4. Methods: There were 44 patients (47 shoulders) with recurrence after primary instability in which bone morphology was evaluated by 3-dimensional reconstructed CT at primary instability (initial CT) and after recurrence. As CT was performed 3 times for 3 shoulders including primary injury and the second episode of instability (first recurrence), there were 50 CT evaluations. Morphological changes between the initial CT evaluation at primary instability and the second CT evaluation at first recurrence were investigated for 25 shoulders, with the mean interval since initial CT being 9.8 months (range, 2-23 months). Changes between initial CT evaluation and final CT evaluation after ≥2 recurrences were also investigated for 25 shoulders, while the mean number of instability episodes including primary instability was 8.0 (range, 3-40) and the mean interval since initial CT was 18.5 months (range, 5-56 months). Results: At primary instability, the prevalence of Hill-Sachs lesions (66.0%) was almost double that of glenoid defects (34.0%), but their prevalence was different between shoulders with primary subluxation (42.3% and 23.8%, respectively) and those with primary dislocation (84.7% and 42.3%, respectively). After recurrence, glenoid defects became significantly more frequent (at first recurrence, 72%; after ≥2 recurrences, 76%), while Hill-Sachs lesions showed a smaller increase (88% and 80%, respectively), so there was no difference between the prevalence of the 2 lesions. The sizes of glenoid defects and Hill-Sachs lesions also enlarged after recurrence, and large bone defects were frequently recognized after recurrence. While bipolar bone loss was not so frequent at primary instability (29.8%), bipolar bone loss increased significantly after recurrence (at first recurrence, 72%; after ≥2 recurrences, 72%). All Hill-Sachs lesions were on track at primary instability, but off-track lesions were recognized in 3 of 47 shoulders (6.4%) after recurrence. Conclusion: In most shoulders with recurrent instability, a Hill-Sachs lesion developed first, followed by a glenoid defect, leading to bipolar bone loss. Off-track Hill-Sachs lesions were detected only after recurrence.

Risk of Engagement of Bipolar Bone Defects in Posterior Shoulder Instability

Background: The risk of re-engagement of bipolar bone defects in posterior shoulder instability has not yet been investigated. Hypothesis: Posterior glenoid defects can lead to the engagement of supposedly noncritical reverse Hill-Sachs lesions (RHSLs). Study Design: Descriptive laboratory study. Methods: In a retrospective multicenter study, 102 cases of posterior shoulder dislocations and resulting RHSLs were collected. Of these cases, all patients with available computed tomography (CT) scans, with a reduced shoulder joint, and without bony posterior glenoid rim defects or concomitant dislocated fractures of the humeral head were included. The gamma angle (measure of the critical size and localization of RHSLs) and the delta angle (measure of the degree of internal rotation necessary for engagement to occur) of the RHSLs were determined on standardized CT scans. Virtual posterior glenoid defects were created, and the effect of increasing defect size on the delta angle was determined. Results: The mean gamma angle of the 19 patients included in this study was 94.5° (range, 69.7°-124.8°). After creation of the virtual posterior glenoid defects, a mean reduction of the delta angle by 2.3° ± 0.2° (range, 1.9°-2.9°) per millimeter defect was observed. The cumulative change in the delta angle showed a highly significant correlation with the absolute and relative size of the glenoid defect (R = 0.982, P < .001 and R = 0.974, P < .001, respectively). Conclusion: Concomitant posterior glenoid defects might lead to the engagement of noncritical RHSLs. When measuring the gamma angle to identify critical RHSLs, posterior glenoid bone loss should be accounted for.

Three-dimensional analysis of the locked position in patients with recurrent shoulder instability

Although recurrent anterior shoulder instability (RASI) is a common condition in young patients, no studies to date have measured the 3-dimensional (3D) locked position of the glenohumeral joint during an anterior dislocation. Therefore, our goal was to estimate it with 3D computed tomography (CT) scans. Patients in this prospective observational study were separated in 3 groups: normal laxity, hyperlaxity, and epilepsy. They were characterized by questionnaires (Western Ontario Shoulder Instability Index, 11-item version of the Disabilities of the Arm, Shoulder and Hand, and Beighton Laxity Score), and a CT scan revealing bipolar bone defects. 3D models of the humeral head and the glenoid were reconstructed from the CT scan, and the rotations and displacements of the humerus relative to the glenoid, from initial to locked position, were calculated. Intraobserver and interobserver reliability by intraclass correlation coefficient (ICC), analysis of variance test, and the Pearson correlation were used to evaluate data. This study involved 44 patients (46 shoulders): 18 with "normal" laxity, 18 with hyperlaxity and 8 (2 bilateral) with epilepsy. The mean locked position was of 12° of abduction, 90° of external rotation, and 21° of extension. The intraobserver and interobserver reliability was excellent for all the rotations and displacements (ICCs, 0.751-0.977) except the proximal-distal displacement (ICCs, 0.409-0.688). Significant differences were found for external rotation, anterior displacement, and medial displacement among the 3 groups of patients. Correlation was found between locked position and function. This study produced highly reliable measurements, with abduction angles proving to be lower than expected. Future work should focus on the effect of this low abduction angle on Hill-Sachs lesion management.

Diagnosis of Engaging Bipolar Bone Defects in the Shoulder Using 2-Dimensional Computed Tomography

Background: Anatomic studies have demonstrated that bipolar glenoid and humeral bone loss have a cumulative effect on shoulder instability and that these defects may engage in functional positions depending on their size and location, potentially resulting in failure of stabilization procedures. Determining which lesions pose a risk for engagement remains challenging, with arthroscopic assessments and a 3-dimensional computed tomography (CT)–based glenoid track method being accepted approaches at this time. Purpose: The purpose was to investigate the interaction of humeral and glenoid bone defects on shoulder engagement in a cadaveric model. Two alternative approaches to predicting engagement were evaluated: (1) CT of the shoulder in abduction and external rotation (ABER) and (2) measurement of the glenoid lesion width and measurement of a novel parameter, the intact anterior articular angle (IAAA), on conventional 2-dimensional multiplane reformats. Study Design: Controlled laboratory study. Methods: Hill-Sachs and glenoid defects of varying sizes were created in 12 cadaveric upper limbs, producing 45 bipolar defect combinations. The defect characteristics were assessed using CT with the shoulder in a neutral position. ABER CT was performed with the shoulder positioned in 60° of glenohumeral abduction (corresponding to 90° of abduction relative to the trunk) and 90° of external rotation. The IAAA was measured as the cartilage arc angle anterior to the Hill-Sachs defect on the axial slice bisecting the humeral head. The performance of the ABER CT and IAAA approaches to predicting engagement were compared with the glenoid track method. Results: Of the 45 defect combinations, 24 (53%) were classified as engaging using the glenoid track method. ABER CT predicted engagement accurately in 43 of 45 (96%), with a sensitivity and specificity of 92% and 100%, respectively. A logistic model based on the glenoid defect width and IAAA provided a prediction accuracy of 87%, with a sensitivity and specificity of 92% and 81%, respectively. Conclusion/Clinical Relevance: Bipolar lesions at risk for engagement can be identified accurately using an ABER CT scan or by performing 2-dimensional measurements of the glenoid defect width and IAAA on conventional CT multiplane reformats. This information will be useful for surgical planning in the setting of bipolar bone defects before shoulder stabilization.

Neglected posterior shoulder dislocation treated with anatomic reconstruction for bipolar bone defects of humeral head and posterior glenoid: A case report and literature reviews

Treatment of chronic posterior shoulder dislocation remains difficult. Currently, there is no consensus on how to treat these cases. In this report, we present a uncommon case of a 42-yearold man with neglected posterior shoulder dislocation, a reverse Hill-Sachs lesion, and a defect of the posterior glenoid. We show our treatments and reviews articles about posterior shoulder dislocations.