The effect of a Hill-Sachs defect on glenohumeral translations, in situ capsular forces, and bony contact forces

Clinical outcome of rotator cuff repair in patients with mild to moderate glenohumeral osteoarthritis

PURPOSE

Osteoarthritis (OA) in the glenohumeral joint is a concomitant lesion with rotator cuff tear that commonly occurs in older patients. The authors aimed to evaluate the effect of associated OA on the treatment outcome of rotator cuff repair.

METHODS

A total of three hundred and forty-eight patients who underwent full-thickness arthroscopic rotator cuff repair were retrospectively reviewed, and the data were prospectively collected. The severity of OA was evaluated using the Samilson and Prieto method preoperatively and the Outerbridge classification intraoperatively. The patients were divided into the small-to-medium group and large-to-massive group according to rotator cuff tear size and were evaluated for presence or absence of OA. The postoperative clinical outcomes were assessed using the visual analog scale for pain, simple shoulder test (SST), University of California-Los Angeles, Constant, and American Shoulder and Elbow Surgeons (ASES) scoring systems at baseline and at final follow-up.

RESULTS

Forty-five patients were diagnosed with glenohumeral OA (12.9%). Overall, no significant differences were observed in demographic and baseline data between the two groups according to the presence or absence of OA. The clinical symptoms of both groups significantly improved at the final follow-up. At the final follow-up, no significant differences were found in the VAS for pain, SST, UCLA, Constant, and ASES scores between the two groups. In the large-to-massive tear group, patients with OA had significantly inferior clinical results compared with those without OA.

CONCLUSION

The clinical outcome scores improved after rotator cuff repair regardless of the presence of concomitant OA. However, glenohumeral OA should be considered as a potential negative prognostic factor in patients with large-to-massive rotator cuff tears.

LEVEL OF EVIDENCE

III.

The Role of Remplissage in the Setting of Shoulder Instability

Recurrent anterior shoulder instability is a multifactorial problem for which many solutions exist. Often, the bony surface area of the humeral head and the glenoid needs to be addressed surgically. For large, engaging humeral head defects associated with <25% glenoid bone loss, a remplissage procedure can effectively "fill in" the humeral defect with minimal postoperative morbidity. Remplissage is an effective biological solution that should be considered any time there is a humeral head defect which is contributing to glenohumeral instability.

Shoulder biomechanics in normal and selected pathological conditions

The stability of the glenohumeral joint depends on soft tissue stabilizers, bone morphology and dynamic stabilizers such as the rotator cuff and long head of the biceps tendon. Shoulder stabilization techniques include anatomic procedures such as repair of the labrum or restoration of bone loss, but also non-anatomic options such as remplissage or tendon transfers.

Rotator cuff repair should restore the cuff anatomy, reattach the rotator cable and respect the coracoacromial arch whenever possible. Tendon transfer, superior capsular reconstruction or balloon implantation have been proposed for irreparable lesions.

Shoulder rehabilitation should focus on restoring balanced glenohumeral and scapular force couples in order to avoid an upward migration of the humeral head and secondary cuff impingement. The primary goal of cuff repair is to be as anatomic as possible and to create a biomechanically favourable environment for tendon healing.

Cite this article: EFORT Open Rev 2020;5:508-518. DOI: 10.1302/2058-5241.5.200006

Humeral Head Osteochondral Allograft Reconstruction with Arthroscopic Anterior Shoulder Stabilization at a Long-Term Follow-Up: A Case Report

CASE

The authors report a case of recurrent anterior shoulder instability in a 19-year-old man. Intraoperative arthroscopic examination identified Bankart and engaging Hill-Sachs lesions. The patient was treated with humeral head osteochondral allograft reconstruction and concomitant arthroscopic anterior stabilization. At the 14-year follow-up, there was no recurrent instability.

CONCLUSION

Humeral head osteochondral allograft reconstruction combined with an arthroscopic anterior stabilization procedure can be successful for recurrent shoulder instability and engaging Hill-Sachs lesion.

New concepts of radiologic preoperative evaluation of anterior shoulder instability: on-track and off-track lesions

The shoulder is the most frequently dislocated joint in the body due to a larger range of motion and a small area of articulation between the humeral and glenoid surfaces. Traumatic shoulder dislocations, especially those associated with injury to the labroligamentous or bony stabilizers of the joint, lead to further reduction of articular surface contact with resultant glenohumeral instability and recurrent shoulder dislocations. Imaging plays an increasingly important role in the preoperative evaluation of patients with traumatic shoulder instability by evaluating glenohumeral bone loss (uni- or bipolar), assessing soft tissue injuries and identifying patients at risk of postoperative recurrence. Quantification of bone loss is key to differentiate engaging vs. non-engaging Hill-Sachs lesions, while newer concepts of "on-track" vs. "off-track" lesions are being discussed that can determine the required surgical approaches. In this article, we review the preoperative imaging approaches, traditional treatments, outline the bone loss measurement strategies and review these new tracking concepts with relevant case examples.

A Clinical Comparison of Linear- and Surface Area-Based Methods of Measuring Glenoid Bone Loss

BACKGROUND

The purpose of this study was to determine whether linear-based measurement significantly overestimates glenoid bone loss in comparison with surface area-based measurement in patients with recurrent anterior shoulder instability and glenoid bone loss.

HYPOTHESIS

Linear-based measurement will significantly overestimate glenoid bone loss in comparison with surface area-based measurement in patients with anterior shoulder instability and glenoid bone loss.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

Thirty patients with anterior shoulder instability underwent preoperative bilateral shoulder computed tomography (CT) scans. Three-dimensional CT (3D-CT) reconstruction with humeral head subtraction was performed to obtain an en face view of the 3D-CT glenoid. Glenoid bone loss was measured with the surface area and linear methods of measurement. Statistical analysis was performed with a paired 2-tailed t test.

RESULTS

Twenty-eight patients (5 female and 23 male; mean age, 25.1 years; age range, 15-58 years) were included in the study; 17 patients underwent a glenoid augmentation procedure, and 11 underwent arthroscopic Bankart repair. The mean percentage glenoid bone loss calculated with the surface area and linear methods was 12.8% ± 8.0% and 17.5% ± 9.7% ( P < .0001), respectively. For the 17 patients who underwent glenoid augmentation, mean percentage bone loss with the surface area and linear methods was 16.6% ± 7.9% and 23.0% ± 8.0% ( P < .0001), respectively.

CONCLUSION

Linear measurement of glenoid bone loss significantly overestimates bone loss compared with surface area measurement in patients with anterior glenoid bony defects. These results indicate that these different methods cannot be used interchangeably and cannot be used with the same critical thresholds for glenoid bone loss.

Trends and Risk Factors for 1-Year Revision of the Latarjet Procedure: The New York State Experience During the Past Decade

Little research has been conducted evaluating surgical trends during the past 10 years and subsequent procedure risk factors for patients undergoing bone-blocking procedures for the treatment of anterior shoulder instability. The Statewide Planning and Research Cooperative System database was queried between 2003 and 2014 to identify patients undergoing soft tissue or bone-blocking procedures for anterior shoulder instability in New York. Patient demographics and 1-year subsequent procedures were analyzed. Multivariate logistic regression analyses were conducted to identify 1-year subsequent procedure risk factors. From 2003 through 2014, a total of 540 patients had Latarjet procedures performed. During this period, the volume of Latarjet procedures increased by 950%, from 12 procedures in 2003 to 126 procedures in 2014. The volume of open Bankart repairs declined by 77%; arthroscopic Bankart repairs fluctuated, being up (328%) between 2003 and 2012 and then down (6%) between 2012 and 2014. Of the 540 patients, 2.4% (13 of 540) required intervention for recurrent shoulder instability events. Age older than 20 years and workers' compensation were identified as independent risk factors for reoperation. The number of bone-blocking procedures, such as the Latarjet, has increased by nearly 1000% during the past decade in New York. Only 2.4% (13 of 540) of the patients had subsequent shoulder instability interventions. [Orthopedics. 2018; 41(3):e389-e394.].

Managing Bony Defects of the Shoulder Joint that Occur in Association with Dislocation

Background

Defects to the articular surface of the humeral head have been known to be associated with shoulder dislocation since the 19^th century. It wasn't until 1934 that the first description of the ubiquitous compression fracture of the posterolateral humeral head that occurs with traumatic anterior instability appeared. From 1940, this defect became referred to as a Hill-Sachs lesion after the investigators who reported the condition. The significance of, and therefore treatment of, these and other such bony defects around the shoulder joint has been hotly debated.

Methods

We reviewed the available current literature to determine and report on the most up to date concepts and treatment techniques being used to manage bony defects of the shoulder.

Results

Numerous surgical options have been proposed to manage bony defects of the shoulder, including a variety of defect-filling procedures, with good outcomes. However, the small numbers and diversity of case mix makes for difficult comparisons.

Conclusion

We are currently developing a greater appreciation of how both the humeral and glenoid defects interact and therefore should be assessed and addressed simultaneously in order to improve patient outcomes. More research and collaboration is needed to determine the optimal method of assessing and managing these patients.

Does the Arthroscopic Latarjet Procedure Effectively Correct "Off-Track" Hill-Sachs Lesions?

BACKGROUND

The glenoid track concept describes the dynamic interaction of bipolar bone loss in anterior glenohumeral instability. Initial studies have successfully demonstrated this concept's application in clinical populations. In clinical practice, the Latarjet procedure is commonly the preferred treatment in addressing "off-track" Hill-Sachs lesions. The effectiveness of this procedure in restoring such lesions to an "on-track" state, however, has not yet been evaluated or described in the literature.

HYPOTHESIS

The Latarjet procedure would transform "off-track" Hill-Sachs lesions to "on-track" lesions. Lesions would remain "on-track" during follow-up, despite glenoid remodeling.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients with "off-track" Hill-Sachs lesions treated with the arthroscopic Latarjet procedure between March 2013 and May 2014 were included. Glenoid track and coracoid graft contact surface area measurements using 3-dimensional computed tomography (3D-CT) were performed preoperatively and at 6-week, 6-month, and at least 12-month (final) follow-up. The mean final follow-up was 23 months. The glenoid diameter, as a percentage of the native glenoid, was also calculated from this imaging.

RESULTS

Twenty-six patients met the inclusion criteria. 3D-CT scans were available for all patients preoperatively and postoperatively, with 21 patients (81%) undergoing 6-month follow-up CT and 19 patients (73%) undergoing final follow-up CT. Hill-Sachs lesions remained "on-track" at all follow-up time points. The mean glenoid diameter changed significantly from 84.6% preoperatively to 122.8% at 6 weeks ( P < .001) and from 120.5% at 6 months to 113.9% at final follow-up ( P = .005). This was also reflected in significant remodeling seen in the coracoid graft articular contact area (6 weeks to 6 months, P = .024; 6 months to final follow-up, P = .002). This persisting glenoid arc enlargement at final follow-up avoided "off-track" Hill-Sachs lesions in 6 of 19 patients (32%), which would otherwise have occurred had the coracoid graft remodeled to native glenoid dimensions.

CONCLUSION

The Latarjet procedure provides an effective treatment for "off-track" engaging Hill-Sachs lesions, despite an evident glenoid remodeling process. At a mean of 23 months postoperatively, a mean persisting enlargement of the glenoid arc of 14% beyond native dimensions remained, avoiding a recurrent "off-track" lesion in 32% of patients, which would otherwise have occurred with complete remodeling.

Management of Humeral Defects in Anterior Shoulder Instability

BACKGROUND

A Hill Sachs lesion is a posterior-superior bony defect of the humeral head caused by a compression of the hard glenoid rim against the soft cancellous bone in the context of an anterior instability episode. The presence of these humeral defects increases with the number of dislocations and larger lesions are associated with a greater chance of development of recurrent instability and recurrence after surgery. Also its location and pattern, in particular the so-called engaging Hill-Sachs, are associated with poor prognosis.

METHODS

There is a lack of consensus in terms of classification and management algorithm, although lesions greater than 25% of the humeral head had been suggested to need more than a simple Bankart repair to avoid recurrence. The concept of glenoid track has turned the attention to location and shape and not only size of the humeral defect. Moreover, the glenoid bone loss is crucial when choosing a treatment option as it contributes to decrease the glenoid track as well. A thorough revision of treatment options has been performed.

RESULTS

Numerous treatment options have been proposed including remplissage, glenoid or humeral head augmentation, bone desimpaction, humeral rotational osteotomy and arthroplasty.

CONCLUSION

Humeral defects treatment should be individualized. Determination of size and location of the defect and its relation with glenoid track is mandatory to achieve satisfactory results.

Latarjet procedure: evolution of the bone block and correspondent clinical relevance-a clinical and radiological study

PURPOSE

The purpose of this study was to correlate the bone block graft position, its dimension, its reabsorption and its integration with clinical outcome in patients operated on for recurrent anterior shoulder instability.

METHODS

Twenty-four patients affected by recurrent anterior shoulder dislocation and operated on using the Latarjet procedure were enrolled in this study. At 6 and 24 months, patients were evaluated with the following scales: ROWE, WOSI, Oxford instability score, UCLA, DASH and Constant score. Patients underwent two postoperative CT scans: immediately after surgery (T0) and at 24 months post-op (T1).

RESULTS

At 24 months, none of the 24 patients reported further episodes of dislocation. Clinically at the final follow-up, we found excellent results in all the evaluation scales. Mean reduction in bone graft from T0 to T1 was 42% of the overall volume; similarly reduction in the overall surface was 29.3%; decrease in length, width and depth was, respectively, 3.4, 2.2 and 1.0 mm; all these parameters decreased significantly (p < 0.05). No correlations were found between radiological parameters and clinical and functional outcomes.

CONCLUSIONS

The results confirm that a lack of integration or a significant reabsorption of the graft is present in the Latarjet procedure, but they do not significantly affect the clinical and functional results.

Remplissage of an Off-track Hill-Sachs Lesion Is Necessary to Restore Biomechanical Glenohumeral Joint Stability in a Bipolar Bone Loss Model

PURPOSE

To validate the glenoid track concept in a cadaveric bipolar bone loss model and to test whether "on-track" and "off-track" lesions can be stabilized with Bankart repair (BR) with or without Hill-Sachs remplissage (HSR).

METHODS

Eight fresh-frozen cadaveric shoulders were tested in a custom apparatus with passive axial rotation and then progressive translational loading (10 to 40 N) at mid-range (60°) and end-range external rotation (90°). Injury conditions included glenoid bone loss of 15% with on-track (15%) and off-track (30%) Hill-Sachs lesions. Repair conditions included BR with HSR and BR without HSR.

RESULTS

For on-track lesions, engagement occurred with translation testing in one shoulder (12.5%) at end-range rotation. After BR, engagement was prevented for this shoulder. For off-track lesions, engagement with translation testing occurred in 8 shoulders (100%) at end-range rotation and in 6 (75%) at mid-range rotation. After BR, engagement was prevented in 4 of 6 engaging shoulders (67%) at mid-range rotation but was prevented in zero of 8 (0%) at end-range rotation. Adding HSR prevented engagement in all 14 engaging shoulders with off-track lesions (100%). BR with HSR resulted in supraphysiological stiffness for off-track lesions at mid- and end-range rotation (13.3 N/m vs 7.0 N/m and 10.0 N/m vs 5.0 N/m, P = .0002) and for on-track lesions at end-range rotation (10.1 N/m vs 5.0 N/m, P = .0002). Stiffness of BR with HSR was not different from the intact shoulder for on-track lesions at mid-range rotation (7.2 N/m vs 7.0 N/m, P > .99).

CONCLUSIONS

The patterns of engagement of Hill-Sachs lesions with a 15% glenoid defect in this model give support to the glenoid track concept. BR plus remplissage resulted in supraphysiological shoulder stiffness but was necessary to prevent engagement of off-track bipolar bone lesions.

CLINICAL RELEVANCE

This biomechanical study provides evidence to aid in surgical decision making by examining the effects of bipolar bone loss and soft-tissue reconstruction on shoulder stability.

Biomechanical analysis of the effect of congruence, depth and radius on the stability ratio of a simplistic 'ball-and-socket' joint model

Objectives

The bony shoulder stability ratio (BSSR) allows for quantification of the bony stabilisers in vivo. We aimed to biomechanically validate the BSSR, determine whether joint incongruence affects the stability ratio (SR) of a shoulder model, and determine the correct parameters (glenoid concavity versus humeral head radius) for calculation of the BSSR in vivo.

Methods

Four polyethylene balls (radii: 19.1 mm to 38.1 mm) were used to mould four fitting sockets in four different depths (3.2 mm to 19.1mm). The SR was measured in biomechanical congruent and incongruent experimental series. The experimental SR of a congruent system was compared with the calculated SR based on the BSSR approach. Differences in SR between congruent and incongruent experimental conditions were quantified. Finally, the experimental SR was compared with either calculated SR based on the socket concavity or plastic ball radius.

Results

The experimental SR is comparable with the calculated SR (mean difference 10%, sd 8%; relative values). The experimental incongruence study observed almost no differences (2%, sd 2%). The calculated SR on the basis of the socket concavity radius is superior in predicting the experimental SR (mean difference 10%, sd 9%) compared with the calculated SR based on the plastic ball radius (mean difference 42%, sd 55%).

Conclusion

The present biomechanical investigation confirmed the validity of the BSSR. Incongruence has no significant effect on the SR of a shoulder model. In the event of an incongruent system, the calculation of the BSSR on the basis of the glenoid concavity radius is recommended.

Cite this article: L. Ernstbrunner, J-D. Werthel, T. Hatta, A. R. Thoreson, H. Resch, K-N. An, P. Moroder. Biomechanical analysis of the effect of congruence, depth and radius on the stability ratio of a simplistic ‘ball-and-socket’ joint model. Bone Joint Res 2016;5:453–460. DOI: 10.1302/2046-3758.510.BJR-2016-0078.R1.

Trends in Bone-Block Augmentation Among Recently Trained Orthopaedic Surgeons Treating Anterior Shoulder Instability

BACKGROUND

Shoulder instability is a common entity requiring surgical stabilization. Although arthroscopic soft-tissue stabilization has been the most common surgical treatment, increased attention is now being paid to Latarjet coracoid transfers and bone-block augmentation, particularly with glenoid bone loss. The purpose of this work was to evaluate the current status of arthroscopic soft-tissue stabilization and bone-block augmentation stabilization techniques among newly trained orthopaedic surgeons in the United States.

METHODS

The American Board of Orthopaedic Surgery (ABOS) database was utilized to identify shoulder instability cases submitted by ABOS Part-II Board Certification examination candidates. Cases were dichotomized into two groups: isolated soft-tissue stabilizations and bone-block augmentation procedures, including coracoid transfer. The two groups were then analyzed to determine trends in annual incidence, complication rates, types of complications, concomitant procedures, surgeon fellowship training, and geographic region of practice.

RESULTS

From 2004 to 2013, 6,854 surgeons submitted 7,587 shoulder instability surgical cases that met all inclusion criteria. Of these, 7,515 (99.1%) were isolated soft-tissue stabilizations, and 72 (0.95%) were bone-block glenoid augmentations. Surgeons with sports medicine fellowship training performed 61.85% of isolated soft-tissue stabilization procedures and 58.33% of bone-block stabilization procedures. The percentage of stabilization cases that utilized bone-block augmentation increased tenfold from 0.14% to 1.4% (p = 0.029) during the study period. The overall annual incidence of isolated soft-tissue stabilizations (p = 0.037) and bone-block procedures (p = 0.016) increased from 2004 to 2013. Although the complication rate of the bone-block procedures remained steady (mean rate, 20.8%; p = 0.932), the isolated soft-tissue stabilization complication rate rose from 4.9% to 9.0% (mean rate, 5.4%; p = 0.003).

CONCLUSIONS

A trend exists toward increased utilization of bone-block stabilization for the treatment of shoulder instability among recently trained orthopaedic surgeons. Complication rates remained relatively high (20.8%) for these procedures, but did not increase as was seen with the isolated soft-tissue stabilizations. Residency and fellowship programs should continue to focus on methods to optimize training for these procedures.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Does Repair of a Hill-Sachs Defect Increase Stability at the Glenohumeral Joint?

Background:

The effect of osteoallograft repair of a Hill-Sachs lesion and the effect of allograft fit on glenohumeral translations in response to applied force are poorly understood.

Purpose:

To compare the impact of a 25% Hill-Sachs lesion, a perfect osteoallograft repair (PAR) of a 25% Hill-Sachs lesion, and an “imperfect” osteoallograft repair (IAR) of a 25% Hill-Sachs lesion on glenohumeral translations in response to a compressive load and either an anterior or posterior load in 3 clinically relevant arm positions.

Study Design:

Controlled laboratory study.

Methods:

A robotic/universal force-moment sensor testing system was used to apply joint compression (22 N) and an anterior or posterior load (44 N) to cadaveric shoulders (n = 9) with the skin and deltoid removed (intact) at 3 glenohumeral joint positions (abduction/external rotation): 0°/0°, 30°/30°, and 60°/60°. The 25% bony defect state, PAR state, and IAR state were created and the loading protocol was performed. Translational motion was measured in each position for each shoulder state. A nonparametric repeated-measures Friedman test with a Wilcoxon signed-rank post hoc test was performed to compare the biomechanical parameters (P < .05).

Results:

Compared with the defect shoulder, the PAR shoulder had significantly less anterior translation with an anterior load in the 0°/0° (15.3 ± 8.2 vs 16.6 ± 9.0 mm, P = .008) and 30°/30° (13.6 ± 7.1 vs 14.2 ± 7.0 mm, P = .021) positions. Compared with IAR, the PAR shoulder had significantly less anterior translation with an anterior load in the 0°/0° (15.3 ± 8.2 vs 16.6 ± 9.0 mm, P = .008) and 30°/30° (13.6 ± 7.1 vs 14.4 ± 7.1 mm, P = .011) positions, and the defect shoulder had significantly less anterior translation with an anterior load in the 30°/30° (14.2 ± 7.0 vs 14.4 ± 7.0 mm, P = .038) position.

Conclusion:

PAR resulted in the least translational motion at the glenohumeral joint. The defect shoulder had significantly less translational motion at the joint compared with the IAR. An IAR resulted in the most translational motion at the glenohumeral joint. This demonstrates the biomechanical importance of performing an osteoallograft repair in which the allograft closely matches the Hill-Sachs defect and fully restores the preinjury state of the humeral head.

Clinical Relevance:

This study demonstrates the importance of performing an osteoallograft repair of a Hill-Sachs defect that closely matches the preinjury state and restores normal humeral head anatomy.

The biomechanical effect of shoulder remplissage combined with Bankart repair for the treatment of engaging Hill-Sachs lesions

PURPOSE

The purpose of this study was to determine the biomechanical effects of the remplissage repair combined with Bankart repair for engaging Hill-Sachs lesions on range of motion (ROM), translation, and glenohumeral kinematics.

METHODS

Six cadaveric shoulders were tested using a custom shoulder testing system. ROM, kinematics, and anterior-posterior (AP) and superior-inferior glenohumeral translations were quantified at 0° and 60° glenohumeral abduction. Six conditions were tested: intact, Bankart lesion, Bankart with 40 % Hill-Sachs lesion, Bankart repair, Bankart repair with remplissage, and remplissage repair alone.

RESULTS

Humeral external rotation (ER) and total range of motion increased significantly after the creation of the Bankart lesion at both 0° and 60° abduction. The Bankart repair restored ER to intact values at 0° and 60° abduction, and the addition of the remplissage repair did not significantly alter range of motion from the Bankart repair alone. AP translation increased following the creation of the Bankart and Hill-Sachs lesions and was restored with the Bankart repair; the remplissage did not alter translation from the Bankart repair alone. At maximum ER at 60° abduction, the apex of the humeral head shifted posteriorly and inferiorly with remplissage repair.

CONCLUSIONS

The addition of the remplissage procedure combined with Bankart repair for treatment of large Hill-Sachs lesions had no statistically significant effect on ROM or translation, but altered the kinematics of the glenohumeral joint. Thus, by addressing the humeral bone defect following an anterior shoulder dislocation, the remplissage technique with concurrent Bankart repair may be a relatively minimally invasive option for converting engaging Hill-Sachs lesions to non-engaging and promoting shoulder stability, though further biomechanical and clinical studies are warranted.

Comparison of 3-Dimensional Computed Tomography-Based Measurement of Glenoid Bone Loss With Arthroscopic Defect Size Estimation in Patients With Anterior Shoulder Instability

PURPOSE

The purpose of this study was to compare four 3-dimensional (3D) computed tomography (CT) methods of measuring glenoid bone loss with the arthroscopic estimation of glenoid bone loss.

METHODS

Twenty patients with recurrent anterior shoulder instability underwent bilateral shoulder CT scans and were found to have glenoid bone loss. Arthroscopic estimation of glenoid bone loss was performed in all patients. Three-dimensional CT reconstruction was performed on the CT scans of each patient. The glenoid bone loss of each patient was measured using the surface area, Pico, ratio, and anteroposterior distance-from-bare area methods. The mean percent loss calculated with each method was compared with arthroscopy to determine the reliability of arthroscopy in the measurement of glenoid bone loss.

RESULTS

The mean percent bone loss calculated with arthroscopic estimation, surface area, Pico, ratio, and anteroposterior distance-from-bare area methods was 18.13% ± 11.81%, 12.15% ± 8.50% (P = .005), 12.77% ± 8.17% (P = .002), 9.50% ± 8.74% (P < .001), and 12.44% ± 10.68% (P = .001), respectively. Repeated-measures analysis of variance showed that the 3D CT methods and arthroscopy were significantly different (F4,76 = 13.168, P = .02). The estimate using arthroscopy is 55% greater than the average of the 3D CT methods.

CONCLUSIONS

Our findings suggest that arthroscopy significantly overestimates glenoid bone loss compared with CT and call into question its validity as a method of measurement. A more internally consistent and accurate method for the measurement of glenoid bone loss is necessary to appropriately diagnose and treat shoulder instability.

LEVEL OF EVIDENCE

Level IV, case series.

Imaging methods for quantifying glenoid and Hill-Sachs bone loss in traumatic instability of the shoulder: a scoping review

Background

Glenohumeral instability is a common problem following traumatic anterior shoulder dislocation. Two major risk factors of recurrent instability are glenoid and Hill-Sachs bone loss. Higher failure rates of arthroscopic Bankart repairs are associated with larger degrees of bone loss; therefore it is important to accurately and reliably quantify glenohumeral bone loss pre-operatively. This may be done with radiography, CT, or MRI; however no gold standard modality or method has been determined. A scoping review of the literature was performed to identify imaging methods for quantifying glenohumeral bone loss.

Methods

The scoping review was systematic in approach using a comprehensive search strategy and standardized study selection and evaluation. MEDLINE, EMBASE, Scopus, and Web of Science were searched. Initial selection included articles from January 2000 until July 2013, and was based on the review of titles and abstracts. Articles were carried forward if either reviewer thought that the study was appropriate. Final study selection was based on full text review based on pre-specified criteria. Consensus was reached for final article inclusion through discussion amongst the investigators. One reviewer extracted data while a second reviewer independently assessed data extraction for discrepancies.

Results

Forty-one studies evaluating glenoid and/or Hill-Sachs bone loss were included: 32 studies evaluated glenoid bone loss while 11 studies evaluated humeral head bone loss. Radiography was useful as a screening tool but not to quantify glenoid bone loss. CT was most accurate but necessitates radiation exposure. The Pico Method and Glenoid Index method were the most accurate and reliable methods for quantifying glenoid bone loss, particularly when using three-dimensional CT (3DCT). Radiography and CT have been used to quantify Hill-Sachs bone loss, but have not been studied as extensively as glenoid bone loss.

Conclusions

Radiography can be used for screening patients for significant glenoid bone loss. CT imaging, using the Glenoid Index or Pico Method, has good evidence for accurate quantification of glenoid bone loss. There is limited evidence to guide imaging of Hill-Sachs bone loss. As a consensus has not been reached, further study will help to clarify the best imaging modality and method for quantifying glenohumeral bone loss.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-015-0607-1) contains supplementary material, which is available to authorized users.

Mid-range shoulder instability modeled as a cam-follower mechanism

In this paper, we model a simplified glenohumeral joint as a cam-follower mechanism during experimental simulated dislocation. Thus, humeral head trajectory and translational forces are predicted using only contact surface geometry and compressive forces as function inputs. We demonstrate this new interpretation of glenohumeral stability and verify the accuracy of the method by physically testing a custom-molded, idealized shoulder model and comparing data to the output of the 2D mathematical model. Comparison of translational forces between experimental and mathematical approaches resulted in r(2) of 0.88 and 0.90 for the small and large humeral head sizes, respectively. Comparison of the lateral displacement resulted in r(2) of 0.99 and 0.98 for the small and larger humeral head sizes, respectively. Comparing translational forces between experiments and the mathematical model when varying the compressive force to 30 N, 60 N, and 90 N resulted in r(2) of 0.90, 0.82, and 0.89, respectively. The preliminary success of this study is motivation to introduce the effects of soft tissue such as cartilage and validation with a cadaver model. The use of simple mathematical models such as this aid in the set-up and understanding of experiments in stability research and avoid unnecessary depletion of cadaveric resources.

A biomechanical analysis of a single-row suture anchor fixation of a large bony bankart lesion

PURPOSE

This study was conducted to assess whether a single-row suture anchor repair of a bony Bankart lesion comprising 19% of the glenoid length restores peak translational force and glenoid depth compared with the intact shoulder.

METHODS

Nine thawed adult cadaveric shoulders were dissected and mounted in 45° of abduction and 30° of external rotation. A bony Bankart lesion was simulated with an anterior longitudinal osteotomy, parallel to the superoinferior axis of the glenoid, equivalent to 19% of the glenoid length. The humeral head was displaced 10 mm anteriorly at a speed of 2 mm/s with a 50-N compressive load applied. Testing was performed with the glenoid intact, a simulated lesion, and the lesion repaired with 3 single-row suture anchors. Median (interquartile range [IQR]) peak translational force and glenoid depth were reported. The Friedman test and post hoc comparisons with the Wilcoxon signed rank test were used for between-group analyses.

RESULTS

Peak translational force decreased after osteotomy (13.7 N; IQR, 9.6 to 15.5 N; P = .01) and increased after the repair (18.3 N; IQR, 18.3 to 20.6 N; P = .01) compared with the intact shoulder (23.7 N; IQR, 16.4 to 29.9 N). Glenoid depth significantly decreased after the osteotomy (0.2 mm; IQR, -0.6 to 0.7 mm) compared with baseline (1.7 mm; IQR, 1.3 to 2.0 mm; P = .01) and increased after repair (0.8 mm; IQR, 0.1 to 1.0 mm; P = .03) compared with the osteotomized shoulder. The glenoid depth of the repair was less than the baseline value (P = .01).

CONCLUSIONS

Repair of an anterior bony Bankart lesion equivalent to 19% of the glenoid length with 3 suture anchors restored the peak translational force needed to anteriorly displace the humerus relative to the glenoid; however, this technique failed to restore the natural glenoid depth in a laboratory setting.

CLINICAL RELEVANCE

Our findings describe the inability of a single-row suture anchor repair to provide anatomic fixation of the bony Bankart lesion equivalent to 19% of the glenoid length.

Shoulder instability in the setting of bipolar (glenoid and humeral head) bone loss: the glenoid track concept

BACKGROUND

An assortment of variables has been used in predicting anterior shoulder instability resulting from pathologic engagement of Hill-Sachs lesions on the glenoid. The glenoid track is a unique biomechanical model that relates both Hill-Sachs and bony Bankart lesions to predict shoulder engagement. We examined the glenoid track concept to determine if it provides a model that unifies glenoid rim and humeral head bone loss in predicting engagement.

QUESTIONS/PURPOSES

In this review we addressed two questions: (1) How are humeral head and glenoid rim bony defects and their interactions quantified? (2) Why is the concept of the glenoid track important?

METHODS

We performed a systematic review of the literature using PubMed (MEDLINE) and OVID for biomechanical studies and peer-reviewed articles published until March 2013. Twenty-four studies fit the inclusion criteria. These were subdivided into four anatomic studies, four studies quantifying glenohumeral bone loss, nine studies biomechanically defining shoulder engagement, six studies analyzing current treatment models, and one clinical study to be included in the final review.

RESULTS

Data demonstrate pathologic engagement is dependent on the medial margin of the Hill-Sachs lesion traveling outside the glenoid track. The width of the glenoid track decreases accordingly if there is a glenoid defect, making engagement more likely. Most treatment models focus on widening the glenoid track before addressing Hill-Sachs lesions.

CONCLUSIONS

The glenoid track uses both glenoid and humeral head bone loss to predict subsequent risk of humeral head engagement and possible dislocation. The glenoid track shows us that restoring the track to its natural width should be among the surgeon's first priority in restoring shoulder stability. Humeral head lesions, also known as Hill-Sachs lesions, are surgically addressed when they cause clinical symptoms. Symptoms arise when the medial margin of the defect engages the glenoid track.

Effect of humeral head rotation on bony glenohumeral stability

BACKGROUND

The humeral head and glenoid cavity are not perfectly spherical, nor do they have matching radii of curvature. We hypothesized that glenohumeral stability is dependent on axial humeral rotation.

METHODS

Seven cadaveric shoulders were investigated. For each test, the humeral head was translated relative to the glenoid in 2 directions (starting from neutral), anterior and anteroinferior. Contact forces and lateral humeral displacement were recorded. Joint stability was quantified using the stability ratio and energy to dislocation. The humerus was set in 60° of abduction for all tests. Testing was performed in neutral rotation and 60° of external rotation.

FINDINGS

The force displacement curves differed between rotations. In both displacement directions, the peak translational force occurred with less displacement in neutral rotation than in external rotation. The stability ratio and energy to dislocation in the anteroinferior direction were greater than in the anterior direction for both rotation positions. While there were no significant differences in the stability ratio or energy to dislocation between rotation conditions at complete dislocation, the energy required to move the humeral head 10% of the glenoid width was significantly greater with the arm in neutral rotation.

INTERPRETATION

The energy to dislocation, a new parameter of dislocation risk, and the stability ratio, indicate that the glenohumeral joint is more stable in the anteroinferior direction than the anterior direction. During initial displacement, axial rotation of the humeral head contributes to glenohumeral geometrical stability. However, humeral head rotation does not have a significant effect when looking at complete dislocation.

Revision posterior shoulder stabilization

BACKGROUND

Revision arthroscopic posterior glenohumeral stabilization requires a thorough understanding of the static and dynamic stabilizers of the glenohumeral joint. The evaluation of these patients is complex but critical given the variety of possible underlying lesions.

METHOD

We reviewed the literature surrounding recurrent and revision posterior instability biomechanics, etiology, evaluation, treatment, and outcomes. We also reviewed our own database of posterior instability cases and isolated revision procedures to review our own outcomes and to highlight overall concepts.

DISCUSSION/CONCLUSION

Although other authors have argued that performing a revision procedure indicates for an open procedure and osseous augmentation, our experience has been that revision posterior stabilization arthroscopic soft-tissue repair alone may be indicated in selected patients. After identification of posterior glenoid bone loss/effective retroversion and mechanical failure of prior repairs, the majority of the patients with recurrence of posterior instability likely have either recurrent or persistent labral pathology or patulous capsules with occult multi-directional instability primarily manifesting in the posterior direction. These patients are best served with capsular shift, reefing, and plication, often requiring 180-270° repair and 4 or greater suture anchors. Because of significant heterogeneity in the clinical outcomes reported to date further research will be necessary to define the clinical outcomes in revision posterior stabilization.

The effect of glenohumeral osteoarthritis on the outcome of isolated operatively treated supraspinatus tears

BACKGROUND

Rotator cuff tear is considered to be a common source of shoulder pain and dysfunction. Osteoarthritis of the glenohumeral joint (OAG) may coexist with rotator cuff tear, especially in elderly patients. The aim of the study was to evaluate the effect of associated OAG on the treatment outcome of rotator cuff repair.

METHODS

A total of 85 consecutive shoulders with an arthroscopically repaired isolated full-thickness supraspinatus tendon tear in males were included in this study. The grade of OAG was estimated preoperatively from shoulder radiographs using the Kellgren-Lawrence (K-L) classification, and peroperatively using the Outerbridge classification. Supraspinatus tendon tear was re-inserted anatomically to the native footprint in all cases. The Constant score was used as an outcome measure and was measured preoperatively and 1 year after the operation. The effect of OAG on the Constant score was analyzed statistically.

RESULTS

82 shoulders (96.5 %) were available for the 1-year follow-up. Preoperative OAG was detected in 22/82 patients (26.8 %). Any OAG above K-L grade 0 was associated with a lower Constant score preoperatively [49.9 (SD 17.6) vs. 60.1 (SD 16.7) (p = 0.0185)] and also at the 1-year follow-up [73.9 (SD 17.5) vs. 82.8 (SD 10.9) (p = 0.0074)]. 16/60 patients (26.7 %) with K-L grade 0 radiographs had peroperatively detected OAG. Furthermore, any peroperatively detected OAG was associated with a lower Constant score preoperatively [53.2 (SD 19.0) vs. 60.9 (SD 15.2) (p = 0.0445)] and at the 1-year follow-up 76.8 [(SD 14.8) vs. 83.5 (SD 11.4) (p = 0.0223)].

CONCLUSION

OAG is a relatively common finding in operated supraspinatus tear patients. Pre- and peroperatively detected OAG during rotator cuff reconstruction is predictive for lower pre- and postoperative Constant scores.

Theoretical model of the effect of combined glenohumeral bone defects on anterior shoulder instability: a finite element approach

The presence of either a Hill-Sachs or a bony Bankart defect has been indicated as a possible cause of subluxation and anterior shoulder dislocation. Previous studies investigated only the effects of isolated humeral or glenoid defects on glenohumeral instability. We investigated the effects on shoulder stability of both glenoid and humeral defects in the glenohumeral joint. A computer-based finite element approach was used to model the joint. A generic model was developed for cartilage and bone of the glenoid and humerus, using previously published data, and experiments were analyzed using static analysis with displacement control in the anterior-inferior direction. Simulations were run with a 50-N compressive load in the presence of both isolated and combined defects to analyze reaction forces and distance to dislocation. The distance to dislocation for normal joint was 13.6 mm at 90° abduction, which reduced to 9.7, 0, and 0 mm for largest isolated humerus defect, glenoid defect, and certain combined defects, respectively. For combined defects, stability ratio was decreased to 0% from 43%. Our results suggest that in the setting of combined bone defects, stability may be reduced more than what is known for isolated defects alone.

Bone loss in anterior instability

Bone loss is commonly observed in shoulders with anterior instability. The Latarjet procedure is commonly performed when a glenoid bony defect exists that is greater than 25 % of the glenoid width or when the risk of recurrent instability is higher (i.e., collision-sport athletes). Hill-Sachs lesions need to be assessed as well. For the purpose of assessing the bipolar lesions, the glenoid track concept is useful. A Hill-Sachs lesion that is located more medially than the medial margin of the glenoid track is defined as an engaging Hill-Sachs lesion. A potential treatment for such a condition is remplissage, but this procedure also decreases range of motion. Thus, its application in overhead athletes needs to be carefully considered.