Posterior Glenoid Defects Research Articles

Posterior Glenoid Bone Grafting in the Setting of Excessive Glenoid Retroversion Does Not Provide Adequate Stability in a Cadaveric Posterior Instability Model

Background: Excessive glenoid retroversion is a known risk factor for posterior shoulder instability and failure after soft tissue stabilization procedures. Whether excessive glenoid retroversion is a risk factor for failure after posterior glenoid bone grafting is unknown. Purpose: To evaluate the biomechanical effectiveness of posterior iliac crest bone grafting (ICBG) for posterior shoulder instability with increasing glenoid retroversion. Study Design: Controlled laboratory study. Methods: Six fresh-frozen cadaveric shoulders had a posterior glenoid osteotomy allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At these 3 preset angles, 4 conditions were simulated consecutively on the same specimen: (1) intact glenohumeral joint, (2) posterior Bankart lesion, (3) 20% posterior glenoid bone defect, and (4) posterior ICBG. Stability was evaluated in the jerk position (60° of glenohumeral anteflexion, 60° of internal rotation) by measuring (A) posterior humeral head (HH) translation (in mm) and (B) peak translational force (in N) necessary for translation of the HH over 25% of glenoid width. Results: At 0° of retroversion, the ICBG restored posterior HH translation and peak translational force to values comparable with those of the intact condition (P = .649 and P = .979, respectively). At 10° of retroversion, the ICBG restored the peak translational force to a value comparable with that of the intact condition (22.3 vs 24.7 N, respectively; P = .418) but showed a significant difference in posterior HH translation in comparison to the intact condition (4.5 vs 2.0 mm, respectively; P = .026). There was a significant increase in posterior HH translation and significant decrease in peak translational force with the ICBG at 20° of glenoid retroversion compared with the intact condition (posterior HH translation: 7.9 vs 2.0 mm, respectively; P < .006; peak translational force: 15.3 vs 24.7 N, respectively; P = .014). Conclusion: In this cadaveric study, posterior ICBG was able to restore stability to a level comparable to that of the native condition at 0° and to some extent at 10° of retroversion. However, posterior ICBG was not able to provide adequate stability at 20° of glenoid retroversion. Clinical Relevance: Posterior glenoid bone grafting with ICBG should be used with caution when performed in isolation in the setting of posterior instability associated with glenoid bone loss and combined glenoid retroversion of >10°.

The Kouvalchouk procedure vs. distal tibial allograft for treatment of posterior shoulder instability: the deltoid “hammock” effect exists

BackgroundIn 1993, Kouvalchouk described an acromial bone block with a pedicled deltoid flap for the treatment of posterior shoulder instability. This procedure provides a “double blocking” effect in that the acromial autograft restores posterior glenoid bone loss and the deltoid flap functions as a muscular “hammock” resembling the sling effect of the conjoint in the Latarjet procedure. The primary aim of this study was to compare the Kouvalchouk procedure to distal tibial allograft (DTA) reconstruction for the management of posterior shoulder instability with associated bone loss, while the secondary aim was to evaluate the deltoid hammock effect. s MethodsTen upper extremity cadavers were evaluated using a validated shoulder testing apparatus in 0° and 60° of glenohumeral abduction in the scapular plane. Testing was first performed on the normal shoulder state and was followed by the creation of a 20% posterior glenoid defect. Subsequently, the Kouvalchouk and DTA procedures were conducted. Forces of 0N, 5N, 10N and 15N were applied to the posterior deltoid tendinous insertion on the Kouvalchouk graft along the physiological muscle line-of-action to evaluate the ‘hammock” effect of this procedure. Testing was additionally performed on the Kouvalchouk bone graft with the deltoid muscle sectioned from its bony attachment. For all test states, a posteriorly directed force was applied to the humeral head perpendicular to the direction of the glenoid bone defect, with the associated translation quantified using an optical tracking system. The outcome variable was posterior translation of the humeral head at an applied force magnitude of 30N. ResultsThe Kouvalchouk procedure with the loaded deltoid flap (10N: P=0.039 and 15N: P<0.001) was significantly better at reducing posterior humeral head translation than the DTA. Overall, increased glenohumeral stability was observed with increased force applied to the posterior deltoid flap in the Kouvalchouk procedure. The 15N Kouvalchouk was most effective at preventing posterior humeral translation, and the difference was statistically significant compared with the 20% glenoid defect (P=0.003), detached Kouvalchouk (P<0.001), and 0N Kouvalchouk (P<0.001). The 15N Kouvalchouk procedure restored posterior shoulder joint stability to near normal levels, such that it was not significantly different from the intact state (P=0.203). ConclusionsThe Kouvalchouk procedure with load applied to the deltoid was found to be biomechanically superior to the DTA for the management of posterior shoulder instability with associated bone loss. Additionally, the results confirmed the presence and effectiveness of the deltoid “hammock” effect.

Management of Bone Loss in Posterior Glenohumeral Shoulder Instability: Current Concepts.

» Posterior glenohumeral instability is relatively uncommon compared with anterior instability, but is becoming an increasingly recognized and surgically managed shoulder pathology.» Soft-tissue stabilization alone may not be sufficient in patients who present with substantial bone loss to the posterior glenoid and/or the anterior humeral head.» For posterior glenoid defects, posterior glenoid osteoarticular augmentation can be used, and posterior glenoid opening wedge osteotomy can be considered in cases of posterior instability with pathologic retroversion.» For humeral head lesions, several surgical treatment options are available including subscapularis transposition into the humeral head defect, autograft or allograft reconstruction, humeral rotation osteotomy, and shoulder arthroplasty.

Predictors of poor and excellent outcomes following reverse shoulder arthroplasty for glenohumeral osteoarthritis with an intact rotator cuff

BackgroundAs the indications for reverse total shoulder arthroplasty (RSA) continue to evolve, it has been more commonly utilized for the treatment of glenohumeral osteoarthritis with an intact rotator cuff (GHOA). Given the increased use of RSA for GHOA, it is important to identify factors influential of clinical outcomes. In this study, we sought to identify variables predictive of clinical outcomes following RSA for GHOA. MethodsPatients undergoing primary RSA for GHOA between 2015-2020 were retrospectively identified through a prospectively maintained, single surgeon registry. Eligible patients had complete patient-reported outcome measures and range of motion measurements with a minimum 2-year follow-up. Univariate analysis was utilized to compare characteristics and outcome measures of patients with poor and excellent outcomes, which was defined as postoperative American Shoulder and Elbow Surgeons (ASES) scores in the bottom and top quartiles, respectively. Multivariate linear regression was performed to determine factors independently predictive of postoperative ASES score. ResultsA total of 230 patients were included with a mean follow-up of 33.4 months (SD 13.2). The mean age of the study population was 71.9 (SD 6.1). Two hundred twenty-four patients (97.4%) surpassed the minimal clinically important difference and 209 patients (90.1%) achieved substantial clinical benefit for ASES score. Preoperative factors differing between the poor and excellent outcome groups were sex (male: poor 37.9%, excellent 58.6%; P = .041), opioid use (poor 24.1%, excellent 5.2%; P = .009), ASES score (poor 32.9, excellent 41.0; P = .011), and forward elevation (poor 92°, excellent 101°; P = .030). Linear regression demonstrated that Walch B3 glenoids (β 7.08; P = .010) and higher preoperative ASES scores (β 0.14; P = .025) were predictors of higher postoperative ASES score, while postoperative complications (β -18.66; P < .001) and preoperative opioid use (β -11.88; P < .001) were predictive of lower postoperative ASES scores. ConclusionOver 90% of patients who underwent RSA for GHOA with an intact rotator cuff experienced substantial clinical benefit. An unsurprising handful of factors were associated with postoperative clinical outcomes; higher preoperative ASES scores were slightly associated with higher postoperative ASES, whereas preoperative opioid use and postoperative complications were associated with lower postoperative ASES. Additionally, Walch glenoid type B3 was associated with higher postoperative ASES, indicating that patients with posterior glenoid defects are not predisposed to poor clinical outcomes following RSA. These results serve as a resource to improve preoperative patient counseling and manage postoperative expectations.

Favorable short-term outcomes of micronized allogenic cartilage scaffold for glenoid cartilage defects associated with posterior glenohumeral instability

To determine clinical outcomes associated with micronized allogenic cartilage scaffold use for treatment of posterior glenoid cartilage defects at 2 years. Case series. A retrospective analysis of prospectively collected data was performed on a consecutive series of patients who underwent arthroscopic treatment of a symptomatic posterior glenoid cartilage defect with micronized allogenic cartilage scaffold between January 2019 and December 2020. The primary outcome was subjective shoulder value (SSV) at latest follow-up. Secondary outcomes included visual analog scale (VAS), recurrence of instability, and range of motion (ROM). Seven patients, including 4 in the setting of primary posterior instability and 3 in the setting of recurrent symptoms after arthroscopic posterior glenohumeral stabilization, were included in the analysis with a mean follow up of 2.6 years (range, 2-3.7 years). Statistically significant improvements were seen in SSV (median= 40, interquartile range [IQR]= 40-50 before surgery; vs median= 85, IQR= 67.5-87.5 after surgery; P= .018) and VAS (median= 4, IQR= 4-6.3 before surgery; vs median=1, IQR= 0-1.5 after surgery; P= .010). No significant differences were seen in ROM. There were no cases of recurrent instability or reoperation. The use of micronized allogenic cartilage scaffold for glenoid cartilage defects is associated with clinical improvement at 2-year follow-up. This is the case when performed in conjunction with index posterior labral repair when there is a concomitant glenoid cartilage defect or when performed in the setting of persistent pain and mechanical symptoms after prior posterior labral repair. Level IV, therapeutic case series.

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

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. 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. 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). 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.

Comprehensive management of posterior shoulder instability: diagnosis, indications, and technique for arthroscopic bone block augmentation.

Recurrent posterior glenohumeral instability is an entity that demands a high clinical suspicion and a detailed study for a correct approach and treatment. Its classification must consider its biomechanics, whether it is due to functional muscular imbalance or to structural changes, volition, and intentionality.Due to its varied clinical presentations and different structural alterations, ranging from capsule-labral lesions and bone defects to glenoid dysplasia and retroversion, the different treatment alternatives available have historically had a high incidence of failure.A detailed radiographic assessment, with both CT and MRI, with a precise assessment of glenoid and humeral bone defects and of glenoid morphology, is mandatory.Physiotherapy focused on periscapular muscle reeducation and external rotator strengthening is always the first line of treatment. When conservative treatment fails, surgical treatment must be guided by the structural lesions present, ranging from soft tissue repair to posterior bone block techniques to restore or increase the articular surface.Bone block procedures are indicated in cases of recurrent posterior instability after the failure of conservative treatment or soft tissue techniques, as well as symptomatic demonstrable nonintentional instability, presence of a posterior glenoid defect >10%, increased glenoid retroversion between 10 and 25°, and posterior rim dysplasia. Bone block fixation techniques that avoid screws and metal allow for satisfactory initial clinical results in a safe and reproducible way.An algorithm for the approach and treatment of recurrent posterior glenohumeral instability is presented, as well as the author’s preferred surgical technique for arthroscopic posterior bone block.

A Three-Dimensional Computed Tomography Radiographic Study -- Can We Predict Glenoid Width Based on Glenoid Height? (216)

Objectives:The purpose of this study was to investigate the relationship between glenoid width and other morphologic parameters using three-dimensional (3D) computed tomography (CT) images of native shoulders in hopes of generating a formula to predict glenoid width which will have utility in planning boney shoulder stabilization surgeries.Methods:102 glenoid images were obtained for patients who underwent contralateral shoulder glenoid reconstruction for anterior shoulder instability between 2012 and 2020. Demographic data was obtained including age, gender and BMI. The subjects were excluded if they had a prior history of ipsilateral shoulder instability, shoulder fractures, or bone tumors. The following glenoid parameters were measured: width (W), height (H), ratio (W/H), anteroposterior (AP) depth, superior-inferior (SI) depth and version. The shape of the glenoid was also classified into pear, inverted comma or oval. Data was analyzed based on gender and age. Simple logistic regression, Kruskal Wallis Rank tests and Fisher Exact tests were performed.Results:There were 71 male and 25 females with a mean age of 39.74 ± 17.88 years. Pear morphotype accounted for most glenoid shapes (46%). The glenoid width was strongly correlated with the height (coefficient = 0.78) and a regression model equation was obtained: W (mm) = 3.4 + 0.68*H (mm). There was also strong correlation with gender (P<0.0001), age (P=0.0384), BMI (P<0.0001), glenoid shape (P=0.0036), height (P=0.0019), AP and SI depths (P<0.0001). Male gender was associated with higher measurement values for all parameters. Older age was significantly correlated with higher glenoid width values in both male and females group. (P=0.0015 and P=0.0104, respectively).Conclusions:The native glenoid width can be easily estimated using solely the glenoid height. This is particularly important for surgical decision making when facing anterior or posterior glenoid defects in patients with shoulder instability.

A Sequential Approach to the Management of Posterior Glenoid Defects in RSA: Angulated BIO Versus Multiple Bioresorbable Pinning-Assisted Structural Bone-Grafting.

Background:Large posterior glenoid defects pose problems in reverse shoulder arthroplasty (RSA). We have adopted a sequential approach to the management of posterior glenoid defects using asymmetrical reaming, the placement of a ring graft around the central peg (bony-increased offset, or BIO), or structural bone-grafting, depending on the amount of glenoid retroversion. Furthermore, we have devised multiple bioresorbable pinning (MBP)-assisted bone-grafting, in which as many bioresorbable pins as required are inserted, from whichever aspects of the graft necessary, to achieve initial stability.Methods:We reviewed 52 shoulders with posterior glenoid defects undergoing RSA between 2014 and 2019 (mean follow-up, 4.8 years; range, 2 to 6 years). Twenty (38.5%) of the shoulders had glenoid retroversion of <15° and were treated by asymmetrical reaming (Group A), 19 (36.5%) of the shoulders had retroversion of ≥15° to <30° and were treated with asymmetrical reaming combined with angulated ring graft around the central peg (Group B), and 13 (25.0%) of the shoulders had retroversion of ≥30° and were treated with MBP-assisted bone-grafting (Group C).Results:Mean version correction was 10.6° ± 4.3° in Group A, 20.7° ± 8.8° in Group B, and 33.8° ± 9.6° in Group C. The mean postoperative active anterior elevation was 138.3° ± 12.3°, 128.3° ± 12.3°, and 126.5° ± 15.3° in the 3 groups, respectively. The mean postoperative Constant score was 66.8 ± 14.6, 62.2 ± 13.5, and 61.7 ± 16.7, respectively. The mean preoperative active anterior elevation was significantly higher in Group A than in Group C (p = 0.037). The full or partial graft-incorporation rate (≥25% of original size) was 89.5% in Group B and 100% in Group C. One glenoid fracture and 1 case of transient brachial plexus palsy occurred in Group B (10.5%), and 1 acromion fracture and 2 cases of transient brachial plexus palsy occurred in Group C (23.1%).Conclusions:The results of the present sequential approach to management of posterior glenoid defects by the 3 modalities were acceptable. The present MBP-assisted bone-grafting procedure is an effective treatment for cases of shoulder arthropathy with severe posterior glenoid defects. Angulated ring grafting around the central peg may yield equally acceptable results, although its graft-incorporation rate requires further follow-up.Level of Evidence:Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Location of the Glenoid Defect in Shoulders with Recurrent Posterior Glenohumeral Instability

Objectives:Posterior glenoid bone deficiency is an increasingly recognized entity in the setting of recurrent posterior shoulder instability; however, little is known about the subject. Due to the paucity of literature on posterior bone loss, historical comparisons to anterior bone loss may not be fully accurate. The purpose of this study was to systematically describe the morphology of posterior bone defects in the setting of recurrent posterior shoulder instability based on several quantitative parameters, including the mean location, orientation, and extent of bone loss on a clock face model, as well as the angle of the defect relative to the long axis of the glenoid.Methods:3-dimensional (3D) reconstructed computed tomography (CT) scans of serially collected patients with a history of recurrent posterior shoulder instability were evaluated by three separate reviewers. The posterior glenoid bone defect was characterized using the following measures: (a) the mean lesion location and orientation based on a clock face model with 6:00 o’clock denoted as inferior and 9:00 o’clock as directly posterior for all patients; (b) the total extent of the posterior bone defect based on the clock face; and (c) the average angle of the bone loss relative to the long axis of the glenoid.Results:A total of 70 male patients and 1 female patient with mean age of 29.3 years (range = 24.4 to 35.1 years) were included in the analysis. The mean clock face location of the posterior glenoid defect originated at 6:44 (range = 4:16 to 8:12) and extended to a mean of 9:28 (range = 7:02 to 10:38). The mean extent of the posterior glenoid defect was 2:43 (range = 1:08 to 4:50), which corresponds to a mean total bone loss arc of 81.5° (range = 34.2° to 144.9°), nearly one quadrant of the glenoid. Posterior bone loss occurred in a posteroinferior direction at a mean angle of 30.7° (range = 8.0° to 80.0°) relative to the long axis of the glenoid.Conclusion:This study describes the location and orientation of posterior glenoid bone loss one can expect when treating this challenging patient population. Posterior bone defects in the setting of posterior shoulder instability most commonly occur in the posterior-inferior quadrant of the glenoid and extend on average from 6:44 to 9:28 (81.5° total degrees of arc) on a clock face model. Posterior bone loss occurs at a mean of 30° off the long axis of the glenoid in a posteroinferior direction, which is historically different from anterior bone loss, which occurs parallel to the long axis of the glenoid. This study serves to highlight the location and orientation of bone loss that one can expect in a patient with recurrent posterior shoulder instability, although additional work is needed to assess why this develops.Figure 1.Figure 2.Figure 3.Figure 4.

Location of the Glenoid Defect in Shoulders With Recurrent Posterior Glenohumeral Instability

Background: Posterior glenoid bone deficiency is an increasingly recognized entity in the setting of recurrent posterior shoulder instability; however, little is known about the subject. Due to the paucity of literature on posterior bone loss, historical comparisons with anterior bone loss may not be fully accurate. Purpose: To systematically describe the morphology of posterior bone defects in the setting of recurrent posterior shoulder instability based on several quantitative parameters, including the mean location, orientation, and extent of bone loss on a clockface model, as well as the angle of the defect relative to the long axis of the glenoid. Study Design: Cross-sectional study; Level of evidence, 4. Methods: Three-dimensional reconstructed computed tomography scans of serially collected patients with a history of recurrent posterior shoulder instability were evaluated by 3 separate reviewers. The posterior glenoid bone defect was characterized using the following measures: (1) the mean lesion location and orientation based on a clockface model with 6 o’clock denoted as inferior and 9 o’clock as directly posterior for all patients; (2) the total extent of the posterior bone defect based on the clockface; and (3) the average angle of the bone loss relative to the long axis of the glenoid. Results: A total of 70 male patients and 1 female patient with a mean age of 29.3 years (range, 24.4-35.1 years) were included in the analysis. The mean clockface location of the posterior glenoid defect originated at 6:44 (range, 4:16-8:12) and extended to a mean of 9:28 (range, 7:02-10:38). The mean extent of the posterior glenoid defect was 2:43 (range, 1:08-4:50), which corresponds to a mean total bone loss arc of 81.5° (range, 34.2°-144.9°), nearly 1 quadrant of the glenoid. Posterior bone loss occurred in a posteroinferior direction at a mean angle of 30.7° (range, 8.0°-80.0°) relative to the long axis of the glenoid. Conclusion: Posterior bone defects in the setting of posterior shoulder instability most commonly occur in the posteroinferior quadrant of the glenoid and extend on average from 6:44 to 9:28 (81.5° total degrees of arc) on a clockface model. Posterior bone loss occurs at a mean of 30° off the long axis of the glenoid in a posteroinferior direction, which is historically different from anterior bone loss, which occurs parallel to the long axis of the glenoid. This study serves to highlight the location and orientation of bone loss that one can expect in a patient with recurrent posterior shoulder instability, although additional work is needed to assess why this develops.

Characterization of Posterior Glenoid Bone Loss Morphology in Patients With Posterior Shoulder Instability

To systemically describe posterior bone defects in the setting of posterior shoulder instability based on several parameters, including surface area, slope and version, defect height from the base of the glenoid, and extent of bone loss at equal intervals along the long axis of the fossa. A total of 40 young, active individuals with recurrent posterior shoulder instability and a bony injury confirmed on either computed tomography (n= 18; mean age, 26.3 ± 4.0years) or magnetic resonance imaging (n= 22; mean age, 20.0 ± 4.9years) were identified. The posterior glenoid bone defect was characterized using the following measures: (1) percentage of bone loss, (2) glenoid vault version, (3) slope of the posterior defect relative to the glenoid surface, (4) superior-inferior length of the defect, and (5) anterior-posterior width of the defect at 5 intervals along the glenoid fossa. The mean age of the 40 patients was 22.9 ± 5.5years (range, 14.9-35.5years). The mean surface area of glenoid bone loss was 9.7% ± 4.7%. Glenoid version measured at 5 equal intervals along the inferior two-thirds of the glenoid was 12.8° ± 4.9°, 11.9° ± 5.0°, 10.1° ± 6.3°, 10.5° ± 6.5°, and 8.7° ± 7.2° from superior to inferior. The mean slope of the posterior defect relative to the glenoid fossa was 26.8° ± 11.5°. The mean superior-inferior height of the bony defect was 21.9 ± 0.4mm. The anterior-posterior sloped width of the defect at 5 equal intervals along the glenoid fossa was 0.9 ± 1.5mm, 2.8 ± 2.4mm, 4.0 ± 1.7mm, 4.0 ± 2.1mm, and 2.9 ± 2.6mm from superior to inferior. Low-grade (<10%) bone loss was diagnosed in most shoulders (23 of 40 evaluated), whereas 15 had moderate bone loss (10% to <20%) and 2 had high-grade bone loss (≥20%). Posterior glenoid bone loss is characterized by a loss of posterior bony concavity, increased slope from anterior to posterior, and increased posterior version. The most anterior-posterior sloped width was quantified at the third and fourth intervals of 5 equal intervals from superior to inferior. This study highlights that patients with posterior instability have bone loss that is sloped relative to the glenoid fossa and suggests that management must be appropriately tailored given the distinctiveness of posterior bone loss. Level IV, case series.

Comparison of a Distal Tibial Allograft and Scapular Spinal Autograft for Posterior Shoulder Instability With Glenoid Bone Loss.

Background:Posterior glenoid bone deficiency can occur with recurrent glenohumeral instability. Glenoid reconstruction with a distal tibial allograft (DTA) has been reported to successfully restore contact pressures that occur during posterior glenohumeral translation. However, there are concerns regarding the risk of allograft resorption, availability, and costs. Extracapsular reconstruction using a scapular spinal autograft (SSA) has been reported as an alternative technique secondary to its anatomic location relative to the posterior shoulder and preferable autograft properties. There are no known prior biomechanical studies evaluating the scapular spine as an effective extracapsular graft choice.Purpose:To compare the efficacy of a DTA and SSA in restoring the stability of a glenoid with a large posterior bone defect compared with the intact native glenoid.Study Design:Controlled laboratory study.Methods:Ten cadaveric shoulders were tested. With the use of a custom KUKA robot, a 50-N compressive force was applied to the glenohumeral joint. The peak force required to translate the humeral head beyond the glenoid lip posteriorly as well as the lateral displacement that occurred during posterior translation were measured. Testing was performed in 5 conditions: (1) intact glenoid and labrum, (2) simulated reverse Bankart lesion, (3) 12-mm posterior glenoid defect, (4) glenoid defect reconstructed with a fresh DTA, and (5) glenoid defect reconstructed with an SSA.Results:The mean glenoid width was 30 mm. The mean peak force and lateral displacement decreased significantly with a glenoid defect (0.99 ± 2.3 N and 0.06 ± 0.09 mm, respectively; P < .0001) compared with the intact glenoid (23.00 ± 9.7 N and 1.83 ± 0.70 mm, respectively; P = .0001). There was no significant difference between the peak force after reconstruction of the defect with a DTA (23.00 ± 7.4 N) and SSA (23.00 ± 7.7 N) when compared with the intact glenoid (P = .9999). There were no significant differences in the peak force between the 2 grafts (P = .9999). Additionally, both the DTA (1.04 ± 1.09 mm) and the SSA (1.02 ± 1.17 mm) demonstrated no differences in lateral displacement when compared with the intact glenoid (P = .2336 and .2043, respectively). There was no difference in lateral displacement that occurred between the DTA and SSA (P = .9999).Conclusion:Reconstruction of a large posterior glenoid defect with either a DTA or an SSA can effectively restore glenohumeral stability.Clinical Relevance:This study supports the use of a DTA or SSA in posterior glenoid defect reconstruction. Clinical studies are needed to determine the long-term effects of utilizing such grafts.

Critical Glenoid Bone Loss in Posterior Shoulder Instability

Background: There is currently no consensus regarding the amount of posterior glenoid bone loss that is considered critical. Critical bone loss is defined as the amount of bone loss that occurs in which an isolated labral repair will not sufficiently restore stability. Purpose: The purpose is to identify the critical size of the posterior defect. Study Design: Controlled laboratory study. Methods: Eleven cadaveric shoulders were tested. With the use of a custom robot device, a 50-N compressive force was applied to the glenohumeral joint, and the peak force that was required to translate the humeral head posteriorly and the lateral displacement that occurred with translation were measured. The defect size was measured as a percentage of the glenoid width. Testing was performed in 11 conditions: (1) intact glenoid and labrum, (2) simulated reverse Bankart lesion, (3) the reverse Bankart lesion repaired, (4) a 10% defect, (5) the reverse Bankart lesion repaired, (6) a 20% defect, (7) the reverse Bankart lesion repaired, (8) a 30% defect, (9) the reverse Bankart lesion repaired, (10) a 40% defect, and (11) the reverse Bankart repaired. Results: Force and displacement decreased as the size of the osseous defect increased. The mean peak force that occurred with posterior displacement in specimens with a glenoid defect ≥20% and a reverse Bankart repair (13 ± 9 N) was significantly lower than the peak force that occurred in specimens with an isolated reverse Bankart repair (22 ± 10 N) (P = .0451). In addition, the mean lateral displacement was significantly less in the specimens with a 20% glenoid defect and a reverse Bankart repair (0.61 ± 0.57 mm) compared with the lateral displacement that occurred in specimens with an isolated reverse Bankart repair (1.6 ± 0.78 mm) (P = .0058). Conclusion: An osseous defect that is ≥20% of the posterior glenoid width remains unstable after isolated reverse Bankart repair. Clinical Relevance: A bony restoration procedure of the glenoid may be necessary in shoulders with a posterior glenoid defect that is ≥20% of the glenoid width.

Diagnostics and treatment of posterior shoulder instability

Posterior shoulder instability has amarkedly lower incidence than anterior shoulder instability. It has awide spectrum of clinical symptom manifestations and the overwhelming number of patients lack atraumatic primary dislocation. In addition to a detailed medical history, aspecific clinical examination with the help of standardized provocation tests is essential for the diagnostics. For the detection of structural posterior capsule and labral lesions in cases of chronic courses, magnetic resonance imaging (MRI) should be used with an intra-articular contrast agent. Relevant bony defects of the humeral head (reverse Sachs-Hill lesion) are frequent, whereas critical posterior defects of glenoid cavity are relatively rare. Both lesions should be quantified using 3D computed tomography. The choice of therapeutic procedure should be based on the underlying pathology of the defect. Conservative therapy is useful in patients with scapular dyskinesis, voluntary dislocation and pathological muscle patterning. In isolated soft tissue pathologies, arthroscopic labrum fixation and capsule plication are the standard treatment. In the case of insufficient soft tissue relations or critical posterior glenoid defects, bony stabilization of the glenoid using an iliac crest bone graft is the recommended therapy.

Angled BIO-RSA (bony-increased offset–reverse shoulder arthroplasty): a solution for the management of glenoid bone loss and erosion

Glenoid deficiency and erosion (excessive retroversion/inclination) must be corrected in reverse shoulder arthroplasty (RSA) to avoid prosthetic notching or instability and to maximize function, range of motion, and prosthesis longevity. This study reports the results of RSA with an angled, autologous glenoid graft harvested from the humerus (angled BIO-RSA). A trapezoidal bone graft, harvested from the humeral head and fixed with a long-post baseplate and screws, was used to compensate for residual glenoid bone loss/erosion. For simple to moderate (<25°) glenoid defects, standardized instrumentation combined with some eccentric reaming (<15°) was used to reconstruct the glenoid and obtain neutral implant alignment. For severe (>25°) and complex (multiplanar) glenoid bone defects, patient-specific grafts and guides were used after 3-dimensional planning. Patients were reviewed with minimum 2 years of follow-up. Mean follow-up was 36 months (range, 24-81 months). Preoperative and postoperative measurements of inclination and version were performed in the plane of the scapula on computed tomography images. The study included 54 patients (41 women, 13 men; mean 73 years old). Fifteen patients had combined vertical and horizontal glenoid bone deficiency. Among E2/E3 glenoids, inclination improved from 37° (range, 14° to 84°) to 10.2° (range -28° to 36°, P < .001). Among B2/C glenoids, retroversion improved from -21° (range, -49° to 0°) to -10.6° (-32° to 4°, P = .06). Complete radiographic incorporation of the graft occurred in 94% (51 of 54). Complications included infection in 1 and clinical aseptic baseplate loosening in 2. Mild notching occurred in 25% (13 of 51) of patients. Constant-Murley and Subjective Shoulder Value assessments increased from 31 to 68 and from 30% to 83%, respectively (P < .001). Angled BIO-RSA predictably corrects glenoid deficiency, including severe (>25°) multiplanar deformity. Graft incorporation is predictable. Advantages of using an autograftharvested in situ include bone stock augmentation, lateralization, low donor-site morbidity, low relative cost, and flexibility needed to simultaneously correct posterior and superior glenoid defects.

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.

Posterior Shoulder Instability with Glenoid Bone Loss: Morphology of Posterior Bone Defects

Although much less common than anterior shoulder instability with glenoid bone loss, posterior glenoid bone defects leading to shoulder instability are severely limiting and significantly affect a patient's quality of life. Moreover, given the rarity of incidence of this pathology, posterior instability with bone loss has been much less investigated in comparison to anterior instability. Given this paucity in literature, we sought to better define the geometrical pattern of posterior bone defects. The purpose of this study was to geometrically describe posterior bone defects based on slope and version as well as extent of bone loss along equal intervals spanning the long axis of the glenoid fossa. A total of forty young, active individuals with recurrent posterior shoulder instability and a bony injury confirmed on either computed tomography (CT) (n=18, 26.3±4.0 years) or magnetic resonance imaging (MRI) (n=22, 20.0±4.9 years) were identified. The posterior glenoid bone defect was characterized using the following measures: (a) percent bone loss; (b) glenoid vault version; (c) the slope of the posterior defect relative to the glenoid surface; (d) the superior-inferior height of the defect; and (e) the anterior-posterior width of the defect at five intervals along the glenoid fossa. Posterior glenoid bone loss morphology was characterized by MRI and CT as more sloped relative to the glenoid than the more perpendicular pattern of bone loss seen in anterior instability. Although CT featured a more severe pattern of bone loss, including greater glenoid version and a greater slope of the posterior defect, this pattern of glenoid bone loss remained consist regardless of the imaging modality. Posterior glenoid bone loss morphology differs considerably from its anterior counterpart. Therefore, this affirms the notion that shoulder instability with bone loss should not be grouped all together, but treated on a case-by-case basis given the direction of instability.

Iliac Bone Graft for Recurrent Posterior Shoulder Instability with Glenoid Bone Defect

Recurrent posterior shoulder instability is a debilitating condition that is relatively uncommon, but its diagnosis in young adults is increasing in frequency. Several predisposing factors for this condition have been identified, such as the presence of an abnormal joint surface orientation, an osteochondral fracture of the humeral head or glenoid cavity, and a postero-inferior capsuloligamentary deficit, but their relative importance remains poorly understood. Whilst, conservative treatment is effective in cases of hyperlaxity or in the absence of bone abnormality, failure of conservative treatment means that open or arthroscopic surgery is required. In general, soft-tissue reconstructions are carried out in cases of capsulolabral lesions in which bone anatomy is normal, whereas bone grafts have been required in cases where posterior bony Bankart lesions, glenoid defects, or posterior glenoid dysplasia are present. However, a consensus on the exact management of posterior shoulder instability is yet to be reached, and published studies are few with weak evidence. In our study, we report the reconstruction of the glenoid using iliac bone graft in a patient suffering recurrent posterior shoulder instability with severe glenoid bone defect.

Posterior Bone Grafting for Glenoid Defects of the Shoulder

Posterior shoulder instability is a challenging clinical entity that requires a comprehensive history and physical examination, as well as relevant imaging studies, to confidently make the diagnosis. Posterior shoulder instability may cause significant shoulder dysfunction and pain. Several anatomical features contribute to posterior instability, including soft tissue lesions and posterior glenoid bone loss. Posterior shoulder stabilization with bone graft transfer procedures and glenoid osteotomies to restore the normal glenohumeral arc have been revisited in recent years to address posterior glenoid bone erosion and glenoid version issue. This review article provides a comprehensive description of posterior shoulder instability with a focus on the treatment of posterior glenoid bone defects and glenoid version issues.