Simple method of glenoid bone loss calculation using ipsilateral magnetic resonance imaging

Statistical shape models that predict native glenoid width based on glenoid height are inaccurate in their current form: a cross-sectional study

BACKGROUND

The extent of measurement errors of statistical shape models that predict native glenoid width based on glenoid height to subsequently determine the amount of anterior glenoid bone loss is unclear. Therefore, the aim of this study was to (1) create a statistical shape model based on glenoid height and width measured on 3-dimensional computed tomography (3D-CT) and determine the accuracy through measurement errors and (2) determine measurement errors of existing 3D-CT statistical shape models.

MATERIALS AND METHODS

A retrospective cross-sectional study included all consecutive patients who underwent CT imaging before undergoing primary surgical treatment of traumatic anterior shoulder dislocation between 2007 and 2022 at the Tohoku University Hospital and affiliated hospitals. Patients were included when instability was unilateral and CT scans of both the injured and contralateral uninjured shoulder were available. 3D segmentations were created and glenoid height and width of the injured and contralateral uninjured side (gold standard) were measured. Accuracy was determined through measurement errors, which were defined as a percentage error deviation from native glenoid width (contralateral uninjured glenoid), calculated as follows: measurement error = [(estimated glenoid width with a statistical shape model - native glenoid width) / native glenoid width] × 100%. A linear regression analysis was performed to create a statistical shape model based on glenoid height according to the formula: native glenoid width = a × glenoid height + b.

RESULTS

The diagnosis and procedure codes identified 105 patients, of which 69 (66%) were eligible for inclusion. Glenoid height demonstrated a very strong correlation (r = 0.80) with native glenoid width. The linear regression formula based on this cohort was as follows: native glenoid width = 0.75 × glenoid height - 0.61, and it demonstrated an absolute average measurement error of 5% ± 4%. The formulas by Giles et al, Chen et al and Rayes et al demonstrated absolute average measurement errors of 10% ± 7%, 6% ± 5%, and 9% ± 6%, respectively.

CONCLUSION

Statistical shape models that estimate native glenoid width based on glenoid height demonstrate unacceptable measurement errors, despite a high correlation. Therefore, great caution is advised when using these models to determine glenoid bone loss percentage. To minimize errors caused by morphologic differences, preference goes to methods that use the contralateral side as reference.

The Use of Linear Formulas to Estimate Glenoid Bone Loss in the Lebanese Population: A 3-Dimensional Computed Tomography Study

Background

Glenoid bone loss (GBL) is common in patients with shoulder instability and plays a major role in surgical decision-making. While a plethora of GBL estimation methods exist, all of which present specific challenges, recent studies have developed simple linear formulas estimating GBL based on glenoid height.

Purpose

To assess the correlation between glenoid height and width, and to develop specific formulas based on age and sex to calculate the native glenoid width in the Lebanese population.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Computed tomography scans for 202 normal shoulders were extracted from our database. The glenoids were reconstructed in 3 dimensions and their width and height were measured. Glenoid width and height were compared between male and female groups. Correlation analysis was also performed on the width, height, age, and body mass index. Formulas estimating glenoid width were developed using regression analysis including all variables significantly influencing the model. Results were then compared with the values calculated using previously published formulas to determine the external validity when using linear formulas to estimate GBL.

Results

Significant differences were found between men and women. Regression analysis found that glenoid height and width strongly influenced the model, and that age showed a weak but significant correlation; therefore, the following 2 sex-specific formulas were developed: width (mm) = 6.1 + 0.51 ×height+ 0.03 ×age, and width (mm) = 4.55 + 0.51 ×height+ 0.03 ×age, in men and women, respectively. The values yielded from the formulas developed in this study and the true width significantly differed from those calculated from previous reports.

Conclusion

A strong correlation was found between glenoid height and width in a the Lebanese population and demonstrated that glenoid width can be accurately calculated based on the glenoid height and patient's age and sex using the following simplified formulas: width (mm) = 6 + 0.5 ×height+ 0.03 ×age, and width (mm) = 4.5 + 0.5 ×height+ 0.03 ×age, in men and women, respectively.

Three-Dimensional Magnetic Resonance Imaging Fast Field Echo Resembling a Computed Tomography Using Restricted Echo-Spacing Sequence Is Equivalent to 3-Dimensional Computed Tomography in Quantifying Bone Loss and Measuring Shoulder Morphology in Patients With Shoulder Dislocation

PURPOSE

To evaluate the equivalence of 3-dimensional (3D) magnetic resonance imaging (MRI) (FRACTURE [Fast field echo Resembling A CT Using Restricted Echo-spacing]) and 3D computed tomography (CT) in quantifying bone loss in patients with shoulder dislocation and measuring morphologic parameters of the shoulder.

METHODS

From July 2022 to June 2023, patients with anterior shoulder dislocation who were aged 18 years or older and underwent both MRI and CT within 1 week were included in the study. The MRI protocol included an additional FRACTURE sequence. Three-dimensional reconstructions of MRI (FRACTURE) and CT were completed by 2 independent observers using Mimics software (version 21.0) through simple threshold-based segmentation. For bone defect cases, 2 independent observers evaluated glenoid defect, percentage of glenoid defect, glenoid track, Hill-Sachs interval, and on-track/off-track. For all cases, glenoid width, glenoid height, humeral head-fitting sphere radius, critical shoulder angle, glenoid version, vault depth, and post-processing time were assessed. The paired t test was used to assess the differences between 3D CT and 3D MRI (FRACTURE). Bland-Altman plots were constructed to evaluate the consistency between 3D CT and 3D MRI (FRACTURE). Interobserver and intraobserver agreement was evaluated with the interclass correlation coefficient. The paired χ2 test and Cohen κ statistic were used for binary variables (on-track/off-track).

RESULTS

A total of 56 patients (16 with bipolar bone defect, 5 with only Hill-Sachs lesion, and 35 without bone defect) were ultimately enrolled in the study. The measurements of 21 bone defect cases showed no statistically significant differences between 3D CT and 3D MRI: glenoid defect, 4.05 ± 1.44 mm with 3D CT versus 4.16 ± 1.39 mm with 3D MRI (P = .208); percentage of glenoid defect, 16.21% ± 5.95% versus 16.61% ± 5.66% (P = .199); glenoid track, 18.02 ± 2.97 mm versus 18.08 ± 2.98 mm (P = .659); and Hill-Sachs interval, 14.29 ± 1.93 mm versus 14.35 ± 2.07 mm (P = .668). No significant difference was found between 3D CT and 3D MRI in the diagnosis of on-track/off-track (P > .999), and diagnostic agreement was perfect (κ = 1.00, P < .001). There were no statistically significant differences between the 2 examination methods in the measurements of all 56 cases, except that the post-processing time of 3D MRI was significantly longer than that of 3D CT: glenoid height, 34.56 ± 1.98 mm with 3D CT versus 34.67 ± 2.01 mm with 3D MRI (P = .139); glenoid width, 25.32 ± 1.48 mm versus 25.45 ± 1.47 mm (P = .113); humeral head-fitting sphere radius, 22.91 ± 1.70 mm versus 23.00 ± 1.76 mm (P = .211); critical shoulder angle, 33.49° ± 2.55° versus 33.57° ± 2.51° (P = .328); glenoid version, -3.25° ± 2.57° versus -3.18° ± 2.57° (P = .322); vault depth, 37.43 ± 1.68 mm versus 37.58 ± 1.75 mm (P = .164); and post-processing time, 89.66 ± 10.20 seconds versus 360.93 ± 26.76 seconds (P < .001). For all assessments, the Bland-Altman plots showed excellent consistency between the 2 examination methods, and the interclass correlation coefficients revealed excellent interobserver and intraobserver agreement.

CONCLUSIONS

Three-dimensional MRI (FRACTURE) is equivalent to 3D CT in quantifying bone loss in patients with shoulder dislocation and measuring shoulder morphologic parameters.

LEVEL OF EVIDENCE

Level II, development of diagnostic criteria (consecutive patients with consistently applied reference standard and blinding).

A formula for instability-related bone loss: estimating glenoid width and redefining bare spot

PURPOSE

The aim of the study reveals a new intuitive method for preoperatively assessing defect ratio in glenoid deficiency based on the native glenoid width and the bare spot.

METHODS

A linear relationship, i.e. the rh formula, between the native glenoid width (2r) and height (h) was revealed by a cadaver cohort (n = 204). To validate the reliability of the rh formula, 280 3D-CT images of intact glenoids were recruited. To evaluate the accuracy of rh formula in estimating glenoid defect, the 65 anterior-inferior defect models were artificially established based on the 3D-CT images of intact glenoids. Moreover, a clinically common anterior-posterior (AP) method was compared with the rh formula, to verify the technical superiority of rh formula.

RESULTS

The regression analysis indicated a linear relationship between the width and height of intact glenoid: 2r = 0.768 × h - 1.222 mm (R2 = 0.820, p < 0.001). An excellent reliability was found between the formula prediction and model width (ICC = 0.911, p = 0.266). An excellent agreement was found between the predicted values and model parameters (glenoid width, ICCrh = 0.967, prh = 0.778; defect ratio, prh = 0.572, ICCrh = 0.997). And, it is of higher accuracy compared to the AP method (glenoid width, ICCAP = 0.933, pAP = 0.001; defect ratio, ICCAP = 0.911, pAP = 0.033).

CONCLUSION

Applying the cadaver-based formula on 3D-CT scans accurately predicts native glenoid width and redefines bare spot for preoperatively determining glenoid bone loss.

Comparison of Glenoid Dimensions Between 3D Computed Tomography and 3D Printing

INTRODUCTION

Glenoid dimensions can be measured in vivo with various imaging methods including two-dimensional (2D) and three-dimensional computed tomography (CT) and magnetic resonance imaging scans. Printing of three-dimensional (3D) models of the glenoid using imaging data is feasible and can be used to better understand skeletal trauma and complex skeletal deformations such as glenoid bone loss in patients with shoulder instability. The purpose of this study was to compare measurements of glenoid dimensions on 3D CT scan reconstructed models and 3D printed models of the glenoid.

METHODS

CT scans from 62 young, male adults acquired for non-trauma-related causes were evaluated. Following volume rendering, a stereolithography model of each scapula was constructed and a 3D model was printed. Additionally, 3D CT models of each glenoid were reconstructed using dedicated software. Measurements of the maximum glenoid height and width were performed on both the 3D printed and the 3D reconstructed models. To assess intra- and interrater reliability, measurements of 15 glenoids were repeated by two observers after three weeks. The measurements of the 3D printed and 3D reconstructed models were compared.

RESULTS

Inter- and intra-rater reliability was excellent or perfect. Analysis of height and width values demonstrated a strong correlation of 0.91 and 0.89 respectively (p<0.001) for both the 3D printed models and the 3D reconstructed models. There was a strong correlation between the height and width, but no significant difference between the glenoid width and height in both models. There was no statistical significance between height and width when measurements on the two models were examined (p=0.12 and 0.23 respectively).

CONCLUSION

3D printed glenoid models can be used to evaluate the glenoid dimensions, width, and height, as they provide similar accuracy with 3D reconstructed models as provided from CT scan data.

Current Concepts in the Measurement of Glenohumeral Bone Loss

PURPOSE

The extent of glenohumeral bone loss seen in anterior shoulder dislocations plays a major role in guiding surgical management of these patients. The need for accurate and reliable preoperative assessment of bone loss on imaging studies is therefore of paramount importance to orthopedic surgeons. This article will focus on the tools that are available to clinicians for quantifying glenoid bone loss with a focus on emerging trends and research in order to describe current practices.

RECENT FINDINGS

Recent evidence supports the use of 3D CT as the most optimal method for quantifying bone loss on the glenoid and humerus. New trends in the use of 3D and ZTE MRI represent exciting alternatives to CT imaging, although they are not widely used and require further investigation. Contemporary thinking surrounding the glenoid track concept and the symbiotic relationship between glenoid and humeral bone loss on shoulder stability has transformed our understanding of these lesions and has inspired a new focus of study for radiologists and orthopedist alike. Although a number of different advanced imaging modalities are utilized to detect and quantify glenohumeral bone loss in practice, the current literature supports 3D CT imaging to provide the most reliable and accurate assessments. The emergence of the glenoid track concept for glenoid and humeral head bone loss has inspired a new area of study for researchers that presents exciting opportunities for the development of a deeper understanding of glenohumeral instability in the future. Ultimately, however, the heterogeneity of literature, which speaks to the diverse practices that exist across the world, limits any firm conclusions from being drawn.

Return to Preinjury-Level Sports After Arthroscopic Latarjet for Recurrent Anterior Shoulder Instability in Professional Athletes

Background

The Latarjet procedure is recommended to treat recurrent anterior shoulder instability with glenoid bone loss. Longer return-to-sport (RTS) times have been reported after the open Latarjet when compared with the arthroscopic Latarjet.

Purpose

To assess the clinical outcomes and RTS in athletes who underwent an arthroscopic Latarjet.

Study Design

Case series; Level of evidence, 4.

Methods

This study included 46 professional athletes with recurrent anterior shoulder instability who underwent an arthroscopic Latarjet between 2010 and 2016. Patients were divided by type of sport: noncollision and nonoverhead (n = 22), collision and martial arts (n = 13), and overhead (n = 11). Sport activity was evaluated with the Kerlan-Jobe Orthopaedic Clinic (KJOC) score, Subjective Patient Outcome for Return to Sports score, and RTS time. Clinical results were evaluated by Constant-Murley score, Walch-Duplay score, and range of external and internal rotation. Complication rates, recurrence of shoulder instability, and number of revision procedures were recorded. Correlation tests were used to assess the relationship between measured parameters.

Results

The mean ± SD patient age was 27.1 ± 7.3 years, and the mean follow-up was 50.7 ± 18 months. Overall, 44 patients (95.7%) returned to their previously practiced sports, and 40 (87%) returned to their preinjury levels. The RTS time was 5 ± 1.4 months, with no significant difference among sport types. KJOC and Subjective Patient Outcome for Return to Sports scores were 95.2 ± 5.6 and 9.5 ± 1, respectively. Significant pre- to postoperative improvement was seen on the Constant-Murley score (from 54.3 ± 9.4 to 87.9 ± 8.2; P = .001) and Walch-Duplay score (from 53.7 ± 7.3 to 88.1 ± 10.7; P = .001). Mean postoperative external and internal rotation was 72.8° ± 18.6° and 81.3° ± 11.3°. Procedure-related complications occurred in 10 patients (21.7%); recurrence of shoulder instability was observed in 4 (8.7%); and 4 (8.7%) underwent revision surgery. A worse Walch-Duplay score was significantly associated with longer RTS time (r = -0.39; P = .019) and lower KJOC score (r = 0.29; P = .03).

Conclusion

There was a 95.7% RTS rate after the arthroscopic Latarjet procedure, although the procedure was not free from complications.

"Nearly off-track lesions" or a short distance from the medial edge of the Hill-Sachs lesion to the medial edge of the glenoid track does not seem to be accurate in predicting recurrence after an arthroscopic Bankart repair in a military population: a case-control study

BACKGROUND

On-track lesions with a short distance from the medial edge of the Hill-Sachs lesion to the medial edge of the glenoid track (nearly off-track) may predispose recurrence after arthroscopic Bankart repair (ABR) in the general population. The aim of this study was to determine if a shorter distance between the medial edge of the Hill-Sachs lesion and the medial edge of the glenoid track could accurately predict recurrence after an ABR in a high-demand military population. It was hypothesized that a shorter distance would not accurately predict recurrence.

MATERIALS AND METHODS

A retrospective monocenter case-control study was performed at the Dutch Central Military Hospital. Patients with an on-track Hill-Sachs lesion who underwent a primary ABR between 2014 and 2019 with a minimal follow-up of 2 years and a preoperative magnetic resonance imaging (MRI) assessment received a questionnaire. The primary outcome was recurrence, defined as a complete dislocation or subluxation. Glenoid bone loss was assessed using a linear-based method on MRI. The distance from the medial edge of the Hill-Sachs lesion to the medial edge of the glenoid track was defined as the distance to dislocation (DTD). A receiver operating characteristic curve was created to determine the predictive value of the DTD for recurrence. Logistic regression was used to determine preoperative risk factors that predispose recurrence. Covariates were selected based on univariable analysis and included gender, body mass index, age at surgery and first dislocation, laterality, smoking habits, overhead shoulder activity during work, preoperative dislocations, sports type and level, bony or labral lesions on MRI, and DTD.

RESULTS

In total, 80 patients with an average follow-up of 4.8 ± 1.9 years completed the questionnaire and were included in the analyses. Seventeen patients (21%) experienced recurrence at the final follow-up. No difference in DTD was observed among patients who experienced recurrence (9 ± 4 mm) compared with patients who did not (9 ± 5 mm; P = .81). The receiver operating characteristic curve demonstrated no predictive power of DTD for recurrence (area under the curve = 0.49). Smoking at the time of surgery (odds ratio: 3.9; confidence interval: 1.2-12.7; P = .02) and overhead shoulder movement during work (odds ratio: 9.3; confidence interval: 1.1-78.0; P = .04) were associated with recurrence according to the logistic regression analysis.

CONCLUSION

A shorter DTD demonstrated no accuracy in predicting recurrence in a military population. Smoking at the time of surgery and overhead shoulder activity during work were associated with recurrence; however, these analyses were underpowered to draw valid conclusions.

Onlay Dynamic Anterior Stabilization With Biceps Transfer for the Treatment of Anterior Glenohumeral Instability Produces Good Clinical Outcomes and Successful Healing at a Minimum 1 Year of Follow-Up

Purpose

To report the results of the onlay dynamic anterior stabilization (DAS) using the long head of biceps (LHB) and the double double-pulley technique for the treatment of anterior glenohumeral instability (AGI) with ≤20% glenoid bone loss (GBL).

Methods

From September 2018 to December 2021, patients with AGI and ≤20% GBL were enrolled in a prospective study on DAS and followed for a minimum of 1 year. The primary outcomes were Western Ontario Shoulder Instability Index, Rowe score, range of motion, and strength. The secondary outcomes were ability to return to play (RTP), RTP at same level, lack of recurrence of instability, successful LHB healing, and lack of complications. Magnetic resonance imaging was used to measure GBL, Hill-Sachs interval, glenoid track, and assess LHB integrity.

Results

Eighteen consecutive patients underwent DAS. Fifteen patients had a minimum follow-up of 12 months (mean, 23.93 ± 13.67 months). In total, 12 were male and 3 female patients; 73.3% practiced recreational sports; mean age at surgery was 23.40 ± 6.53 years; mean number of dislocation episodes were 10.13 ± 8.42; mean GBL was 8.21 ± 7.39% (range, 0-20.24%); mean Hill-Sachs interval was 15.00 ± 2.96 mm; and mean glenoid track was 18.87 ± 2.57mm. The mean improvement in the Western Ontario Shoulder Instability Index and Rowe score (959.27 ± 386.70 and 74.00 ± 22.22 points) was significant (P < .001 and P < .001) and more than 6 times greater than the minimum clinically important difference. The mean improvement in active elevation, abduction, and external and internal rotation (23.00 ± 27.76°, 33.33 ± 43.78°, 8.33 ± 13.58°, and 0.73 ± 1.28 points) was significant (P = .006, P = .011, P = .032, and P = .044). RTP rate was 93.33%. RTP at same level was 60.00%. One patient with hyperlaxity had a redislocation (6.7% recurrence). No complications were reported. Each magnetic resonance imaging scan showed successful LHB healing to the anterior glenoid.

Conclusions

At a minimum of 1-year follow-up, DAS produces significant and clinically important improvements in shoulder function, successful LHB healing, and is safe for the treatment of AGI with ≤20% GBL without severe hyperlaxity.

Level of Evidence

IV, therapeutic case series.

High correlation between inner and outer glenoid circle diameters and its clinical relevance

PURPOSE

The majority of methods for measuring glenoid bone loss in shoulder instability use the best-fit circle following the inferior glenoid rim. However, there is no precise method on how to draw this circle, particularly in case of a missing rim segment. Defining the radius is a source of substantial error. It was hypothesized that there is a relationship between the best-fit inferior circle (inner circle), defined by Sugaya, and the circle tangent to the supra- and infra-glenoid tubercles (outer circle), defined by Itoi, thus allowing a more consistent appreciation of the paleo-glenoid.

METHODS

Ninety-five normal dry scapulae were examined. The specimens were digitally photographed obtaining perpendicular images of the glenoid cavity. Using HOROS® imaging software, a best-fit inferior circle (inner circle) and a second circle fitting the most inferior and superior points of the glenoid (outer circle) were drawn by two investigators. The diameters and areas of the circles were recorded. Two-way random-effects intra-class correlation coefficients (ICC) were used to measure intra- and inter-observer agreement. A Bayesian measurement-error regression model was used to determine the relationship between outer and inner circle measurements.

RESULTS

The mean glenoid height was 35.1 mm and the glenoid width 25.6 mm. The mean diameter of the outer circle was 35.7 ± 4.2 mm and the mean diameter of the inner circle was 26.8 ± 3.2 mm. ICC showed excellent inter- and intra-observer agreement for both the outer circle diameter (ICC ≥ 0.95) and inner circle diameter (ICC ≥ 0.93). The two diameters demonstrated a very strong significant Pearson correlation (0.92, p < 0.001) and the regression showed excellent model fit R² = 0.87. The areas of the two circles were also highly and significantly correlated (r = 0.94; p < 0.001). The ratio of inner circle to outer diameters was 0.74.

CONCLUSION

There is a strong correlation between the inner and outer glenoid circle diameters. This study sets the base for the use the combined outer and inner circle and its ratio to better appreciate the paleo-glenoid morphology and thus obtain a more reliable bone loss estimation. Application of this method aids in a more reliable estimation bone loss with potential benefit in surgical decision-making.

Calculating glenoid bone loss based on glenoid height using ipsilateral three-dimensional computed tomography

PURPOSE

To investigate the relationship between glenoid width and other morphologic parameters using three-dimensional (3D) computed tomography (CT) images of native shoulders, and to create a new measurement tool to assess glenoid defects in a Canadian population with established anterior shoulder instability.

METHODS

Forty-three glenoid CT scans were analyzed for patients who underwent contralateral shoulder glenoid reconstruction for anterior shoulder instability between 2012 and 2020. Demographic data were 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), anteroposterior (AP) depth, superior-inferior (SI) depth and version. The shape of the glenoid was also classified into pear, inverted comma or oval.

RESULTS

There were 35 male and 8 females with a mean age of 34.5 ± 12.9 years. The glenoid width was strongly correlated with the height (R² = 0.9) and a regression model equation was obtained: W (mm) = 2.5 + 0.7*H (mm). There was also strong correlation with gender (P < 0.001), glenoid shape (P = 0.030), AP and SI depths (P = 0.006 and P < 0.001, respectively). Male gender was associated with higher measurement values for all parameters. The most common glenoid shapes were the pear (46.5%) and oval morphotypes (39.6%) for the whole study group.

CONCLUSION

The native glenoid width can be estimated based on glenoid height using ipsilateral 3D CT. This may help with preoperative planning and surgical decision-making for patients with anterior shoulder instability and glenoid bone loss.

LEVEL OF EVIDENCE

III.

How to Fashion the Bone Block for Reconstruction of the Glenoid in Anterior and Posterior Instability

BACKGROUND

Glenoid restoration techniques to address glenohumeral instability-induced anterior and posterior glenoid bone loss (AGBL and PGBL) often require reconstruction, but best-fit bone block (BFBB) modeling has not been developed.

PURPOSE

To provide glenoid bony reconstruction models for anterior and posterior instability of the shoulder using a bone loss instability cohort with high-fidelity 3-dimensional (3D) imaging.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

We reviewed consecutive patients indicated for operative stabilization who had posterior glenohumeral instability and suspected GBL who underwent 2-dimensional (2D) computed tomography (CT). Patients were matched by sex, laterality, and age to patients who underwent operative stabilization of anterior glenohumeral instability. Mimics software was used to convert all 2D CT scans into 3D models of the scapula. A BFBB model was designed to digitally reconstruct GBL and was used to predict the amount, anatomic configuration, and fixation configuration of bony reconstruction required in AGBL and PGBL.

RESULTS

The study included 30 patients with posterior instability and 30 patients with anterior instability; the participants' mean ± SD age was 28.8 ± 8.15 years (range, 16.0-51.0 years). Mean surface area of AGBL was 24.9% ± 7.7% (range, 14.7%-39.1%). Mean BFBB dimensions to reconstruct the anterior glenoid were determined to be a superior-inferior length of 23.9 ± 4.2 mm, anterior-posterior width of 6.4 ± 2.4 mm, and height of 1 cm. Mean angle of AGBL bone block interface relative to glenoid to reconstruct the native concavity was 79.4°± 5.9°. For PGBL, the mean surface area was 9.2% ± 5.6% (range, 3.0%-26.3%). Mean BFBB dimensions to reconstruct the posterior glenoid were a superior-inferior length of 21.9 ± 3.4 mm, width of 4.5 ± 2.3 mm, and height of 1 cm. The mean angle of PGBL bone block interface relative to the glenoid to reconstruct the native concavity was 38.6°± 14.3°. Orientation relative to the vertical glenoid axis was 77.2°± 13.8° in anterior reconstructions versus 105.9°± 10.9° in posterior reconstructions.

CONCLUSION

Patients with anterior instability required a more rectangular BFBB with a bone block-glenoid interface angle of 79°, whereas patients with posterior instability required a more trapezoidal, obtusely oriented BFBB with a bone block-glenoid interface angle of 39°. BFBBs for either AGBL or PGBL can be effectively designed, and their size and/or shape can be predicted based on approximate percentage of GBL.

Prospective Evaluation of Posterior Glenoid Bone Loss After First-time and Recurrent Posterior Glenohumeral Instability Events

BACKGROUND

Although posterior glenohumeral instability is becoming an increasingly recognized cause of shoulder pain, the role of posterior glenoid bone loss on outcomes remains incompletely understood.

PURPOSES

To prospectively determine the amount of bone loss associated with posterior instability events and to determine predisposing factors based on preinstability imaging.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 1428 shoulders were evaluated prospectively for ≥4 years. At baseline, a subjective history of shoulder instability was ascertained for each patient, and bilateral noncontrast magnetic resonance imaging (MRI) scans of the shoulders were obtained regardless of any reported history of shoulder instability. The cohort was prospectively followed during the study period, and those who were diagnosed with posterior glenohumeral instability were identified. Postinjury MRI scans were obtained and compared with the screening MRI scans. Glenoid version, perfect-circle-based bone loss was measured for each patient's pre- and postinjury MRI scans using previously described methods.

RESULTS

Of the 1428 shoulders that were prospectively followed, 10 shoulders sustained a first-time posterior instability event and 3 shoulders sustained a recurrent posterior instability event. At baseline, 11 of 13 shoulders had some amount of glenoid dysplasia and/or bone loss. The change in glenoid bone loss was 5.4% along the axis of greatest loss (95% CI, 3.8%-7.0%; P = .009), 4.4% at the glenoid equator (95% CI, 2.7%-6.2%; P = .016), and 4.2% of total glenoid area (95% CI, 2.9%-5.3%; P = .002). Recurrent glenoid instability was associated with a greater amount of absolute bone loss along the axis of greatest loss compared with first-time instability (recurrent: 16.8% ± 1.1%; 95% CI, 14.6%-18.9%; first-time: 10.0% ± 1.5%; 95% CI, 7.0%-13.0%; P = .005). Baseline glenoid retroversion ≥10° was associated with a significantly greater percentage of bone loss along the axis of greatest loss (≥10° of retroversion: 13.5% ± 2.0%; 95% CI, 9.6%-17.4%; <10° of retroversion: 8.5% ± 0.8%; 95% CI, 7.0%-10.0%; P = .045).

CONCLUSIONS

Posterior glenohumeral instability events were associated with glenoid bone loss of 5%. The amount of glenoid bone loss after a recurrent posterior glenohumeral instability event was greater than that after first-time instability. Glenoid retroversion ≥10° was associated with a greater amount of posterior glenoid bone loss after a posterior instability event.

Glenoid Bone Loss Determination: Validity and Reliability of the Constellation Technique Versus the Sagittal Best Fit Circle Technique

OBJECTIVE

To propose a new method for glenoid bone loss measurement, the constellation technique (CST); determine its reliability and accuracy; and compare the validity of CST with that of the conventional technique (CVT) and standard measurements for ratio calculation.

MATERIALS AND METHODS

Sixty shoulders with intact glenoids and no glenohumeral instability and arthritis underwent CT scans. Simulated osteotomies were conducted on the 3D models of glenoids at two cutting locations, expressed as clock face times (2:30-4:20; 1:30-5:00). Two experienced surgeons compared three methods for glenoid bone loss measurement; CVT (best-fit circle), CST ('5S' steps), and standard measurement. Eight undergraduates remeasured five randomly chosen shoulders with moderate to severe bone loss. Intraclass correlation coefficients (ICCs) were calculated for raters.

RESULTS

With a defect range between 2:30 and 4:20, all 60 glenoids demonstrated minimal bone loss (< 15%); while between 1:30 and 5:00, 42 shoulders were with moderate bone loss (15-20%), and 18 shoulders with severe bone loss (≥ 20%). For experienced raters, no significant differences were noted between protocos for all categories of bone loss (p ≥ 0.051), with good inter- and intraobserver reliability indicated by ICC. For novice raters, post hoc Tukey analysis found that CST was more accurate in one patient with a standard mean bone loss of 23.2% ± 1.9% compared with CVT.

CONCLUSION

The CST turned the key step of glenoid defect evaluation from deciding an en face view to determining the glenoid inferior rim. The protocol is simple, accurate, and reproducible, especially for novice raters.

A Ratio Estimating Glenoid Bone Loss

Background

Estimating glenoid bone loss when assessing the unstable shoulder can be challenging. The aim of this article was to describe a simple derived ratio to estimate glenoid bone loss.

Methods

When the glenoid is damaged and bone is damaged because of instability, the anterior aspect of the glenoid loses its normal curvature and becomes flattened. In geometry, this represents a chord. There are 3 assumptions for the calculations: (1) the lower glenoid is a circle; (2) there is a relationship between the glenoid height and the diameter of the glenoid circle; and (3) the length of the measured bone loss of the glenoid is a chord. Two measurements are required: glenoid height and length of the glenoid defect. The calculations involved in the ratio are reviewed.

Results

If the ratio of the length of the bone defect to the glenoid height is 0.5 (otherwise, 50% of the height), the estimated bone loss is 12%.

Conclusion

Glenoid bone loss can be estimated by measuring the length of the glenoid and the length of the defect.

The relationship of glenoid version and severity of glenoid bone loss in anterior shoulder instability patients: A retrospective cohort study

Background/objective

The effect of glenoid version on the severity of glenoid bone loss is not completely understood, although the variation of glenoid version angles is considered to reflect the degree of glenoid bone loss in anterior shoulder instability cases. The objective of this retrospective case-control study is to determine the relationship of the glenoid version and the severity of glenoid bone loss in a group of previously documented recurrent anterior shoulder dislocation patients.

Methods

We retrospectively collected magnetic resonance arthrogram (MRA) data from 72 patients with unidirectional recurrent anterior shoulder instability. The best-fit circle method was used to identify the percentage of glenoid bone loss. Measurements of glenoid labral, chondral, and bony versions were performed using the Friedman method.

Results

Using univariate regression analysis, it was found that a retroversion angle of more than 4 degrees was associated with an increased risk ratio for the occurrence of a critical glenoid defect by approximately 5 times.

Conclusions

24 Univariate logistic regression analysis, used to determine the presence of a critical glenoid bone defect, showed that both the bony version angle and the number of previous dislocations were significantly associated with the extent of glenoid bone loss. A retroversion angle of more than 4 degrees was associated with an approximately five-fold increase in the odds ratio for the presence of a critical glenoid defect. Surgeons may use the value of the measured glenoid version in prediction the required version of the reconstructive treatment.

What Is the Most Reliable Method of Measuring Glenoid Bone Loss in Anterior Glenohumeral Instability? A Cadaveric Study Comparing Different Measurement Techniques for Glenoid Bone Loss

BACKGROUND

Preoperative quantification of bone loss has a significant effect on surgical decision making and patient outcomes. Various measurement techniques for calculating glenoid bone loss have been proposed in the literature. To date, no studies have directly compared measurement techniques to determine which technique, if any, is the most reliable.

PURPOSE/HYPOTHESIS

To identify the most consistent and accurate techniques for measuring glenoid bone loss in anterior glenohumeral instability. Our hypothesis was that linear measurement techniques would have lower consistency and accuracy than surface area and statistical shape model-based measurement techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 6 fresh-frozen human shoulders, 3 incremental bone defects were sequentially created resulting in a total of 18 glenoid bone defect samples. Analysis was conducted using 2D and 3D computed tomography (CT) en face images. A total of 6 observers (3 experienced and 3 with less experience) measured the bone defect of all samples with Horos imaging software using 5 common methods. The methods included 2 linear techniques (Shaha, Griffith), 2 surface techniques (Barchilon, PICO), and 1 statistical shape model formula (Giles). Intraclass correlation (ICC) using a consistency model was used to determine consistency between observers for each of the measurement methods. Paired t tests were used to calculate the accuracy of each measurement technique relative to physical measurement.

RESULTS

For the more experienced observers, all methods indicated good consistency (ICC > 0.75; range, 0.75-0.88), except the Shaha method, which indicated moderate consistency (0.65 < ICC < 0.75; range, 0.65-0.74). Estimated consistency among the experienced observers was better for 2D than 3D images, although the differences were not significant (intervals contained 0). For less experienced observers, the Giles method in 2D had the highest estimated consistency (ICC, 0.88; 95% CI, 0.76-0.95), although Giles, Barchilon, Griffith, and PICO methods were not statistically different. Among less experienced observers, the 2D images using Barchilon and Giles methods had significantly higher consistency than the 3D images. Regarding accuracy, most of the methods statistically overestimated the actual physical measurements by a small amount (mean within 5%). The smallest bias was observed for the 2D Barchilon measurements, and the largest differences were observed for Giles and Griffith methods for both observer types.

CONCLUSION

Glenoid bone loss calculation presents variability depending on the measurement technique, with different consistencies and accuracies. We recommend use of the Barchilon method by surgeons who frequently measure glenoid bone loss, because this method presents the best combined consistency and accuracy. However, for surgeons who measure glenoid bone loss occasionally, the most consistent method is the Giles method, although an adjustment for the overestimation bias may be required.

CLINICAL RELEVANCE

The Barchilon method for measuring bone loss has the best combined consistency and accuracy for surgeons who frequently measure bone loss.

The Anatomy of Glenoid Concavity-Bony and Osteochondral Assessment of a Stability-Related Parameter

Glenoid concavity is a crucial factor for glenohumeral stability. However, the distribution of this stability-related parameter has not been focused on in anatomical studies. In this retrospective study, computed tomography (CT) data and tactile measurements of n = 27 human cadaveric glenoids were analyzed with respect to concavity. For this purpose, the bony and osteochondral shoulder stability ratio (BSSR/OSSR) were determined based on the radius and depth of the glenoid shape in eight directions. Various statistical tests were performed for the comparison of directional concavity and analysis of the relationship between superoinferior and anteroposterior concavity. The results proved that glenoid concavity is the least distinctive in anterior, posterior, and anterosuperior direction but increases significantly toward the superior, anteroinferior, and posteroinferior glenoid. The OSSR showed significantly higher concavity than the BSSR for most of the directions considered. Moreover, the anteroposterior concavity is linearly correlated with superoinferior concavity. The nonuniform distribution of concavity indicates directions with higher stability provided by the anatomy. The linear relationship between anteroposterior and superoinferior concavity may motivate future research using magnetic resonance imaging (MRI) data to optimize clinical decision-making toward more personalized treatment of glenoid bone loss.

Three-Dimensional Quantification of Glenoid Bone Loss in Anterior Shoulder Instability: The Anatomic Concave Surface Area Method

Background

Recurrent shoulder instability may be associated with glenoid erosion and bone loss. Accurate quantification of bone loss significantly influences the contemplation of surgical procedure. In addition, assessment of bone loss is crucial for surgical planning and accurate graft placement during surgery.

Purpose

To quantify the concave surface area of glenoid bone loss by using 3-dimensional (3D) segmented models of the scapula and to compare this method with the best-fit circle and glenoid height/width methods, which use the glenoid rim for bone loss estimations.

Study Design

Cohort study (diagnosis); Level of evidence, 2.

Methods

A total of 36 consecutive preoperative bilateral computed tomography scans of patients eligible for a primary Latarjet procedure were selected from our institutional surgical database (mean patient age, 29 ± 9 years; 31 men and 5 women). The 3D models of both scapulae were generated using medical segmentation software and were used to map the anatomic concave surface area (ACSA) of the inferior glenoid using the diameter of the best-fit circle of the healthy glenoid. Bone loss was calculated as a ratio of the difference between surface areas of both glenoids (healthy and pathological) against the anatomic circular surface area of the healthy glenoid (the ACSA method). These results were compared with bone loss calculations using the best-fit circle and glenoid height/width methods. Inter- and intraobserver reliability were also calculated.

Results

The mean (± SD) bone loss calculated using the ACSA, the best-fit circle, and glenoid height/width methods was 9.4% ± 6.7%, 14.3% ± 6.8%, and 17.6% ± 7.3%, respectively. The ACSA method showed excellent interobserver reliability, with an intraclass correlation coefficient (ICC) of 0.95 versus those for the best-fit circle (ICC, 0.71) and glenoid height/width (ICC, 0.79) methods.

Conclusion

Quantification of instability-related glenoid bone loss is reliable using the 3D ACSA method.

Glenoid Bone Loss in Shoulder Instability: Superiority of Three-Dimensional Computed Tomography over Two-Dimensional Magnetic Resonance Imaging Using Established Methodology

Backgroud

Recent literature suggests that three-dimensional magnetic resonance imaging (3D MRI) can replace 3D computed tomography (3D CT) when evaluating glenoid bone loss in patients with shoulder instability. We aimed to examine if 2D MRI in conjunction with a validated predictive formula for assessment of glenoid height is equivalent to the gold standard 3D CT scans for patients with recurrent glenohumeral instability.

Methods

Patients with recurrent shoulder instability and available imaging were retrospectively reviewed. Glenoid height on 3D CT and 2D MRI was measured by two blinded raters. Difference and equivalence testing were performed using a paired t-test and two one-sided tests, respectively. The interclass correlation coefficient (ICC) was used to test for interrater reliability, and percent agreement between the measurements of one reviewer was used to assess intrarater reliability.

Results

Using an equivalence margin of 1 mm, 3D CT and 2D MRI were found to be different (p = 0.123). The mean glenoid height was significantly different when measured on 2D MRI (39.09 ± 2.93 mm) compared to 3D CT (38.71 ± 2.89 mm) (p = 0.032). The mean glenoid width was significantly different between 3D CT (30.13 ± 2.43 mm) and 2D MRI (27.45 ± 1.72 mm) (p < 0.001). The 3D CT measurements had better interrater agreement (ICC, 0.91) than 2D MRI measurements (ICC, 0.8). intrarater agreement was also higher on CT.

Conclusions

Measurements of glenoid height using 3D CT and 2D MRI with subsequent calculation of the glenoid width using a validated methodology were not equivalent, and 3D CT was superior. Based on the validated methods for the measurement of glenoid bone loss on advanced imaging studies, 3D CT study must be preferred over 2D MRI in order to estimate the amount of glenoid bone loss in candidates for shoulder stabilization surgery and to assist in surgical decision-making.

When to Abandon the Arthroscopic Bankart Repair: A Systematic Review

CONTEXT

Bone loss is a major factor in determining surgical choice in patients with anterior glenohumeral instability. Although bone loss has been described, there is no consensus on glenoid, humeral head, and bipolar bone loss limits for which arthroscopic-only management with Bankart repair can be performed.

OBJECTIVE

To provide guidelines for selecting a more complex repair or reconstruction (in lieu of arthroscopic-only Bankart repair) in the setting of glenohumeral instability based on available literature.

DATA SOURCES

An electronic search of the literature for the period from 2000 to 2019 was performed using PubMed (MEDLINE).

STUDY SELECTION

Studies were included if they quantified bone loss (humeral head or glenoid) in the setting of anterior instability treated with arthroscopic Bankart repair.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Study design, level of evidence, patient demographics, follow-up, recurrence rates, and measures of bone loss (glenoid, humeral head, bipolar).

RESULTS

A total of 14 studies met the inclusion criteria. Of these, 10 measured glenoid bone loss, 5 measured humeral head bone loss, and 2 measured "tracking" without explicit measurement of humeral head bone loss. Measurement techniques for glenoid and humeral head bone loss varied widely. Recommendations for maximum glenoid bone loss for arthroscopic repair were largely <15% of glenoid width in recent studies. Recommendations regarding humeral head loss were more variable (many authors providing only qualitative descriptions) with increasing attention on glenohumeral tracking.

CONCLUSION

It is essential that a standardized method of glenoid and humeral head bone loss measurements be performed preoperatively to assess which patients will have successful stabilization after arthroscopic Bankart repair. Glenoid bone loss should be <15%, and humeral head lesions should be "on track" if an arthroscopic-only Bankart is planned. If there is greater bone loss, adjunct or open procedures should be performed.

Simple Linear Calculating Method of Glenoid Bone Defects Using 3-Dimensional Computed Tomography Based on an East Asian Population in China

Background:

The evaluation of glenoid bone defects in the preoperative stage for patients with anterior shoulder instability is critical for surgical decision making. A novel method that predicts the intact glenoid width based purely on the measurement of the glenoid height has been advocated. Despite the convenience, all studies to date have focused on the Western population, and there is no similar research based on an East Asian population.

Purpose:

To determine the relationship between glenoid height and width in an East Asian population.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Spiral computed tomography (CT) scans of both sides of the shoulder joints were obtained from 205 patients of Han nationality (China) who had no history of shoulder trauma or pain. The maximal height and width of each glenoid were measured on the en face view by 2 radiologists who were blinded to each other’s results. Pearson correlation coefficients and multivariable linear regression were calculated from all data measured to evaluate the relationship between maximal glenoid height and width between the sexes.

Results:

A total of 205 patients (410 shoulder CT scans) were analyzed. The mean glenoid height was 34.45 ± 2.82 mm, and the mean glenoid width was 23.35 ± 2.40 mm. There was a statistical difference between male and female patients with regard to glenoid height (36.61 vs 32.39 mm, respectively; t = 9.76; P < .001) and width (25.26 vs 21.54 mm, respectively; t = 20.73; P < .001). Analysis of the measured glenoid height and width demonstrated a strong linear correlation of 0.82 (R² = 0.68; P < .001) for the entire cohort and similarly strong linear correlations when each sex was analyzed separately. For male patients, the glenoid width was measured as: glenoid height × 0.50 + 7 mm (R² = 0.36; P < .001); for female patients, the glenoid width was measured as: glenoid height × 0.45 + 7 mm (R² = 0.31; P < .001).

Conclusion:

In an East Asian population, the mean glenoid height and width were 34.45 and 23.35 mm, respectively. The formulas that represent the relationship between glenoid width and height for male and female patients are the following: glenoid width = glenoid height × 0.50 + 7 mm and glenoid width = glenoid height × 0.45 + 7 mm, respectively.

Novel and effective arthroscopic extracapsular stabilization technique for anterior shoulder instability-BLS

PURPOSE

Arthroscopic Bankart repair for the treatment of anterior shoulder instability is associated with a high rate of recurrent instability. Extracapsular stabilization of the glenohumeral joint with enhancement of anterior wall soft tissues may be an effective alternative treatment technique. The aim of this study is to retrospectively assess clinical outcomes in the treatment of anterior shoulder instability using a novel technique of anterior extracapsular stabilization-"between glenohumeral ligaments and subscapularis tendon" (BLS).

METHODS

Patients with anterior shoulder instability who underwent surgical treatment with a novel arthroscopic BLS technique between 2008 and 2016 were eligible for inclusion. According to the level of glenoid bone loss, patients were separated into four groups. Group 1 comprised patients with GBL equal to or less than 5%, group 2 patients with GBL 6-10%, group 3 patients with GBL 11-15%, and group 4 patients with GBL > 15%. A positive outcome in this study was defined as full restoration of joint stability. To evaluate clinical results, preoperative range of ER and IR measured in 90 degrees of abduction were compared with ER and IR measured at final follow-up. Additional outcome instruments used consisted of the Constant Score and the Walch-Duplay Score.

RESULTS

A total of 150 patients underwent arthroscopic BLS surgery. During the study period, 50 patients were lost to follow-up and 100 patients were available for final analysis. Mean patient age was 27.5 (± 10.3) years at the time of surgery. Mean duration of follow-up was 82.9 (± 29.4) months. At final assessment, 86 patients (86%) were categorized as having a positive outcome, with full restoration of joint stability. Recurrence of shoulder instability was observed in 14 (14%) patients, including 6 (6%) cases that were associated with major trauma. At final follow-up, the mean Constant Score was 88.2 ± 10.1, compared to 82.9 ± 9.1 preoperatively (p < 0.05). The mean final and mean preoperative Walch-Duplay Scores were 81.5 ± 18.9 and 52.2 ± 11.9, respectively (p < 0.05). There was no statistically significant limitation of external or internal rotation.

CONCLUSIONS

The BLS technique has been shown to be an effective method to anterior shoulder instability in patients without significant glenoid bone loss. It was shown that this technique provides significant improvement in shoulder function without reducing shoulder range of motion.

LEVEL OF EVIDENCE

IV.

Reliability of the measurement of glenoid bone defect in anterior shoulder instability

Background:

The size of the glenoid bone defect is an important index in selecting the appropriate treatment for anterior shoulder instability. However, the reliability of glenoid bone defect measurement is controversial. The purpose of the present study was to investigate the reliabilities of measurements of the glenoid bone defect on computed tomography and to explore the predisposing factors leading to inconsistency of these measurements.

Methods:

The study population comprised 69 consecutive patients who underwent surgery for recurrent anterior shoulder dislocation in Peking University Fourth School of Clinical Medicine from March 2016 to January 2017. The glenoid bone defect was measured by three surgeons on ‘self-confirmed’ and ‘designated’ 3-D en-face views, and repeated after an interval of 3 months. Measurements included the ratio of the defect area to the best-fit circle area, and the ratio of the defect width to the diameter of the best-fit circle. The inter- and intra-observer reliabilities of the measurements were evaluated using intraclass correlation coefficients (ICCs). The maximum absolute inter- and intra-observer differences and the cumulative percentages of cases with inter- and intra-observer differences greater than these respective levels were calculated.

Results:

Almost all linear defect values were bigger than the areal defect values. The inter-observer ICCs for the areal defect were 0.557 and 0.513 in the ‘self-confirmed’ group and 0.549 and 0.431 in the ‘designated’ group. The inter-observer reliabilities for the linear defect were moderate or fair in the ‘self-confirmed’ group (ICC = 0.446, 0.374) and ‘designated’ group (ICC = 0.402, 0.327). The ICCs for intra-observer measurements were higher than those for inter-observer measurements. The respective maximum inter- and intra-observer absolute differences were 13.9% and 13.2% in the ‘self-confirmed’ group, and 15.8% and 9.8% in the ‘designated’ group.

Conclusions:

The areal measurement of the glenoid bone defect is more reliable than the linear measurement. The reliability of the glenoid defect areal measurement is moderate or worse, suggesting that a more accurate and objective measurement method is needed in both en-face view and best-fit circle determination. Subjective factors affecting the glenoid bone loss measurement should be minimized.

Prospective Evaluation of Glenoid Bone Loss After First-time and Recurrent Anterior Glenohumeral Instability Events

BACKGROUND

Determining the amount of glenoid bone loss in patients after anterior glenohumeral instability events is critical to guiding appropriate treatment. One of the challenges in treating the shoulder instability of young athletes is the absence of clear data showing the effect of each event.

PURPOSE

To prospectively determine the amount of bone loss associated with a single instability event in the setting of first-time and recurrent instability.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

The authors conducted a prospective cohort study of 714 athletes surveilled for 4 years. Baseline assessment included a subjective history of shoulder instability. Bilateral noncontrast shoulder magnetic resonance imaging (MRI) was obtained for all participants with and without a history of previous shoulder instability. The cohort was prospectively followed during the study period, and those who sustained an anterior glenohumeral instability event were identified. Postinjury MRI with contrast was obtained and compared with the screening MRI. Glenoid width was measured for each patient's pre- and postinjury MRI. The projected total glenoid bone loss was calculated and compared for patients with a history of shoulder instability.

RESULTS

Of the 714 athletes (1428 shoulders) who were prospectively followed during the 4-year period, 22 athletes (23 shoulders) sustained a first-time anterior instability event (5 dislocations, 18 subluxations), and 6 athletes (6 shoulders) with a history of instability sustained a recurrent anterior instability event (1 dislocation, 5 subluxations). On average, there was statistically significant glenoid bone loss (1.84 ± 1.47 mm) after a single instability event ( P < .001), equivalent to 6.8% (95% CI, 4.46%-9.04%; range, 0.71%-17.6%) of the glenoid width. After a first-time instability event, 12 shoulders (52%) demonstrated glenoid bone loss ≥5% and 4 shoulders, ≥13.5%; no shoulders had ≥20% glenoid bone loss. Preexisting glenoid bone loss among patients with a history of instability was 10.2% (95% CI, 1.96%-18.35%; range, 0.6%-21.0%). This bone loss increased to 22.8% (95% CI, 20.53%-25.15%; range, 21.2%-26.0%) after additional instability ( P = .0117). All 6 shoulders with recurrent instability had ≥20% glenoid bone loss.

CONCLUSION

Glenoid bone loss of 6.8% was observed after a first-time anterior instability event. In the setting of recurrent instability, the total calculated glenoid bone loss was 22.8%, with a high prevalence of bony Bankart lesions (5 of 6). The findings of this study support early stabilization of young active patients after a first-time anterior glenohumeral instability event.

The Influence of Bone Loss on Glenoid Version Measurement: A Computer-Modeled Cadaveric Analysis

PURPOSE

To characterize how increasing computed tomography (CT)-quantified glenoid bone loss influences measured version.

METHODS

Six embalmed cadaveric shoulders were used for this study. Glenoid bone defects were computer modeled in cadaveric shoulders; CT images were obtained and segmented using OsiriX software, creating 3-dimensional en face glenoids. Glenoid defects were made on CT images of intact glenoids superimposed with a glenoid clock face viewed en face to simulate anterior and posterior bone loss. Bony defects in various positions comprising 3%, 9.5%, and 19.5% were created posteriorly. Best-fit circles were superimposed to represent 10% and 25% defects anteriorly. Version was measured using the Friedman method.

RESULTS

The average glenoid version measured 4° of retroversion, 2° after 10% anterior bone loss, and neutral version in the 25% bone loss group. Version was significantly altered when we compared intact glenoids versus 10% and 25% anterior glenoid bone loss (P < .001). Increasing from 10% to 25% bone loss showed a significant difference in measured version (P = .025). Posterior defects from the 6:30 to 8:30 clock-face position averaged 4.6° of retroversion; from the 6:30 to 9:30 clock-face position, 6.2° of retroversion; and from the 6:30 to 10:30 clock-face position, 8.7° of retroversion. When comparing glenoid defects at the 6:30 to 8:30 clock-face position with those involving the 6:30 to 9:30 and 6:30 to 10:30 clock-face positions (P < .001), a 1° correction may be used for every 5% of bone loss to account for version changes seen with bone loss.

CONCLUSIONS

In this cadaveric analysis, glenoid version was altered in the setting of increasing posterior and anterior bone loss. A correction factor may be considered to account for this. When comparing glenoid defects at the 6:30 to 8:30 clock-face position with those involving the 6:30 to 9:30 and 6:30 to 10:30 clock-face positions (P < .001), a 1° correction may be used for every 5% of bone loss to account for version changes seen with bone loss.

CLINICAL RELEVANCE

This cadaveric study shows that glenoid bone loss alters glenoid version, as measured by CT, in a meaningful way. This information is important in managing anterior and posterior shoulder instability, and correction of measured version should be considered in this setting to provide an accurate and comprehensive evaluation.

Bone Loss and Glenohumeral Instability

Glenohumeral instability secondary to glenohumeral bone loss presents a complex problem to the treating surgeon because of the complex biomechanics of the glenohumeral joint and its reliance on numerous dynamic and static stabilizers. The role of glenoid bone loss, specifically inferior-anterior glenoid bone loss, has been well characterized in the setting of recurrent unidirectional instability with greatly improved clinical results when following an algorithmic reconstructive approach to the location and percentage of overall bone loss. Furthermore, as the role of bipolar bone loss in the setting of glenohumeral engagement becomes more apparent, surgeons can more effectively address those lesions contributing to the recurrent instability. As such, surgeons should carefully and critically asses patients with recurrent anterior instability to optimize patient clinical outcomes.

Anterior Glenohumeral Instability

Anterior shoulder dislocations, subluxations, and recurrent instability of the shoulder joint are common problems usually affecting a young active population. However, it can be a problem for patients up to the late decades in life and can lead to major shoulder arthropathy if left untreated or improperly treated. This article discusses the natural history, pathologic morphologic changes of the shoulder joint associated with anterior instability along with normal anatomic variants. We will also discuss current treatment recommendations and possible causes of the patient with recurrent instability despite prior stabilization procedures.

Review of Latarjet (1954) on the treatment of recurrent shoulder dislocations

This classic discusses the original publication ‘Treatment of recurrent dislocation of the shoulder’ on the Latarjet procedure. This surgical technique that has become one of the basics in shoulder-stabilising surgery, introduced by Latarjet in 1954 in the journal Lyon Chirurgical. Inspired by publications of colleagues in the field of shoulder surgery, Latarjet introduced a technique that transfers the coracoid process to the anterior glenoid rim in patients with anterior shoulder instability. Although being outrun in popularity by the Bankart repair for several decades, improved knowledge regarding long-term outcomes, surgical techniques and patient characteristics such as bone loss and participation in contact sports has led to renewed interest in the Latarjet procedure. This especially accounts for patients with significant glenohumeral bone loss or patients with a previously failed soft tissue repairs. Whereas the increase in popularity has led to many studies focussing on various aspects, the 15 basics of the initial procedure have virtually remained unchanged.

Radiographic Evaluation of Patients with Anterior Shoulder Instability

PURPOSE OF REVIEW

Injuries to the labrum, joint capsule (in particular the inferior glenohumeral ligament), cartilage, and glenoid periosteum are associated with anterior shoulder instability. The goal of this review is to provide common radiographic images and findings in patients with anterior shoulder instability. Furthermore, we will demonstrate the best methods for measuring anterior glenoid bone loss.

RECENT FINDINGS

Magnetic resonance (MR) imaging is highly relied upon for evaluating anterior shoulder instability and can diagnose soft tissue injuries with high sensitivity. While 3D computed tomography (CT) scan has been considered the optimal tool for evaluating osseous defects, certain MR imaging sequences have been shown to have similar diagnostic accuracy. Repair of Bankart lesions is critical to stabilizing the shoulder, and in the recent years, there has been an increasing focus on imaging to accurately characterize and measure glenoid bone loss to properly indicate patients for either arthroscopic repair or anterior bony reconstruction. Furthermore, Hill-Sachs lesions are commonly seen with shoulder instability, and importance must be placed on measuring the size and depth of these lesions along with possible engagement, as these factors will dictate management. The labral-ligamentous complex and rotator cuff are primary stabilizers of the shoulder. With anterior shoulder instability, the labrum is frequently injured. MRI with an arthrogram or provocative maneuvers is the gold standard for diagnosis. Various imaging modalities and methods can be performed to identify and measure Bankart and Hill-Sachs lesions, which can then be used for surgical planning and treating shoulder instability.

Imaging of the Unstable Shoulder

Background:

Unstable shoulder can occur in different clinical scenarios with a broad spectrum of symptoms and presentations: first-time (or recurrent) traumatic acute shoulder anterior dislocation or chronic anterior instability after repeated dislocations.

Imaging in unstable shoulder is fundamental for choosing the right treatment preventing recurrence.

The goal of imaging depends on clinical scenario and patient characteristics.

Method:

Careful selection and evaluation of the imaging procedures is therefore essential to identify, characterize and quantify the lesions. Proper imaging in unstable shoulder cases is critical to the choice of treatment to prevent recurrence, and to plan surgical intervention.

Results:

In acute setting, radiographs have to roughly detect and characterize the bone defects present. At about 7 days, it is recommended to perform a MR to demonstrate lesions to labrum and/or ligaments and bone defects: in acute setting, the MRA is not necessary, because of effusion and hemarthrosis that behave as the contrast medium.

In recurrence, it is fundamental not only to detect lesions but characterize them for planning the treatment. The first study to do is the MRI (with a magnetic field of at least 1.5 Tesla), and if possible MRA, above all in younger patients. Then, on the basis of the pathologic findings as bipolar lesion or severity of bone defects, CT can be performed. PICO method on 2D or 3D CT is helpful if you need to study a glenoid bone loss, with the “en face view” of glenoid, while a 3D CT reconstruction with the humeral head “en face view” is the gold standard to assess an Hill-Sachs lesion.

Conclusion:

The clinical diagnoses of anterior shoulder instability can be different and acknowledgement of imaging findings is essential to guide the treatment choice.

Imaging features are quite different in chronic than in acute scenario. This requires appropriate indications of many different imaging techniques.

The Effect of Subcritical Bone Loss and Exposure on Recurrent Instability After Arthroscopic Bankart Repair in Intercollegiate American Football

BACKGROUND

There is no consensus on the optimal method of stabilization (arthroscopic or open) in collision athletes with anterior shoulder instability.

PURPOSE

To examine the effect of "subcritical" bone loss and football-specific exposure on the rate of recurrent shoulder instability after arthroscopic stabilization in an intercollegiate American football population.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Fifty intercollegiate football players underwent primary arthroscopic stabilization for anterior shoulder instability and returned to football for at least a single season. Preoperatively, 32 patients experienced recurrent subluxations, and 18 patients experienced a single or recurrent dislocation. Shoulders with glenoid bone loss >20%, an engaging Hill-Sachs lesion, an off-track lesion, and concomitant rotator cuff repair were excluded from the study. The primary outcome of interest was the ability to return to football without subsequent instability. Patients were followed for time to a subsequent instability event after return to play using days of exposure to football and total follow-up time after arthroscopic stabilization.

RESULTS

Fifty consecutive patients returned to American football for a mean 1.5 seasons (range, 1-3) after arthroscopic stabilization. Three of 50 (6%; 95% CI, 1.3%-16.5%) patients experienced recurrent instability. There were no subsequent instability events after a mean 3.2 years of military service. All shoulders with glenoid bone loss >13.5% (n = 3) that underwent arthroscopic stabilization experienced recurrent instability upon returning to sport, while none of the shoulders with <13.5% glenoid bone loss (n = 47) sustained a recurrent instability event during football ( X² = 15.80, P < .001). Shoulders with >13.5% glenoid bone loss had an incidence rate of 5.31 cases of recurrent instability per 1000 athlete-exposures of football. In 72,000 athlete-exposures to football with <13.5% glenoid bone loss, there was no recurrent instability. Significantly more anchors were used during the primary arthroscopic stabilization procedure in patients who experienced multiple preoperative instability events ( P = .005), and lesions spanned significantly more extensive portions along the circumference of the glenoid ( P = .001) compared with shoulders having a single preoperative instability event before surgical stabilization.

CONCLUSION

Arthroscopic stabilization of anterior shoulder instability in American football players with <13.5% glenoid bone loss provides reliable outcomes and low recurrence rates.

The Bony Bankart Lesion: How to Measure the Glenoid Bone Loss

An osseous Bankart lesion is commonly seen in patients with an anterior shoulder dislocation. It is defined as a detachment of the anteroinferior labrum associated with a glenoid rim fracture. Radiological studies are crucial not only for detecting glenoid bone defects but also for measuring the amount of bone loss. The precise quantification of the bony defect is crucial for the therapeutic desicion-making and clinical outcomes. Although we know that major glenoid bone loss requires surgical intervention, none of the studies performed so far answered the question what size of the defect should be an indication for open surgery procedures. Moreover, there is still no consensus on the exact percentage of glenoid loss that results in a higher risk of re-dislocations. In our opinion, there is a strong need for a consensus on universally accepted measuring techniques of the glenoid defect as well as on algorithms with validated glenoid bone loss threshold values for therapeutic decision-making. In this study, we review the techniques described so far in the literature and try to assess if any of these techniques should be treated as a leading method of detecting and quantifying osseous glenoid lesions.

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.

Estimating Glenoid Width for Instability-Related Bone Loss: A CT Evaluation of an MRI Formula

BACKGROUND

Determining the magnitude of glenoid bone loss in cases of shoulder instability is an important step in selecting the optimal reconstructive procedure. Recently, a formula has been proposed that estimates native glenoid width based on magnetic resonance imaging (MRI) measurements of height (1/3 × glenoid height + 15 mm). This technique, however, has not been validated for use with computed tomography (CT), which is often the preferred imaging modality to assess bone deficiencies.

PURPOSE

The purpose of this project was 2-fold: (1) to determine if the MRI-based formula that predicts glenoid width from height is valid with CT and (2) to determine if a more accurate regression can be resolved for use specifically with CT data.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Ninety normal shoulder CT scans with preserved osseous anatomy were drawn from an existing database and analyzed. Measurements of glenoid height and width were performed by 2 observers on reconstructed 3-dimensional models. After assessment of reliability, the data were correlated, and regression models were created for male and female shoulders. The accuracy of the MRI-based model's predictions was then compared with that of the CT-based models.

RESULTS

Intra- and interrater reliabilities were good to excellent for height and width, with intraclass correlation coefficients of 0.765 to 0.992. The height and width values had a strong correlation of 0.900 (P < .001). Regression analyses for male and female shoulders produced CT-specific formulas: for men, glenoid width = 2/3 × glenoid height + 5 mm; for women, glenoid width = 2/3 × glenoid height + 3 mm. Comparison of predictions from the MRI- and CT-specific formulas demonstrated good agreement (intraclass correlation coefficient = 0.818). The CT-specific formulas produced a root mean squared error of 1.2 mm, whereas application of the MRI-specific formula to CT images resulted in a root mean squared error of 1.5 mm.

CONCLUSION

Use of the MRI-based formula on CT scans to predict glenoid width produced estimates that were nearly as accurate as the CT-specific formulas. The CT-specific formulas, however, are more accurate at predicting native glenoid width when applied to CT data.

CLINICAL RELEVANCE

Imaging-specific (CT and MRI) formulas have been developed to estimate glenoid bone loss in patients with instability. The CT-specific formula can accurately predict native glenoid width, having an error of only 2.2% of average glenoid width.

Risk factors for anterior glenohumeral instability

BACKGROUND

While anterior glenohumeral instability has been shown to be common in young athletes, the risk factors for injury are poorly understood.

PURPOSE/HYPOTHESIS

To determine the modifiable and nonmodifiable risk factors for anterior shoulder instability in a high-risk cohort. The hypothesis was that specific baseline factors would be associated with the subsequent risk of injury.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

We conducted a prospective cohort study in which 714 young athletes were followed from June 2006 through May 2010. Baseline assessments included a subjective history of instability, physical examination by a sports medicine fellowship-trained orthopaedic surgeon, range of motion, strength with a handheld dynamometer, and bilateral noncontrast shoulder magnetic resonance imaging (MRI). A musculoskeletal radiologist measured glenoid version, glenoid height, glenoid width, glenoid index (height-to-width ratio), glenoid depth, rotator interval (RI) height, RI width, RI area, RI index, and the coracohumeral interval. Subjects were followed to document all acute anterior shoulder instability events during the 4-year follow-up period. The time to anterior shoulder instability event during the follow-up period was the primary outcome of interest. Univariate and multivariable Cox proportional hazards regression models were used to analyze the data.

RESULTS

Complete data were available for 714 subjects. During the 4-year surveillance period, there were 39 anterior instability events documented at a mean of 285 days. While we controlled for covariates, significant risk factors of physical examination were as follows: apprehension sign (hazard ratio [HR], 2.96; 95% CI, 1.48-5.90; P = .002) and relocation sign (HR, 4.83; 95% CI, 1.75-13.33; P = .002). Baseline range of motion and strength measures were not associated with subsequent injury. Significant anatomic risk factors on MRI measurement were glenoid index (HR, 8.12; 95% CI, 1.07-61.72; P = .043) and the coracohumeral interval (HR, 1.20; 95% CI, 1.08-1.34; P = .001).

CONCLUSION

This prospective cohort study revealed significant risk factors for shoulder instability in this high-risk population. Physical examination findings of apprehension and relocation were significant while controlling for history of injury. The anatomic variables of significance were not surprising-tall and thin glenoids were at higher risk compared with short and wide glenoids, and the risk of instability increased by 20% for every 1-mm increase in coracohumeral distance.

Glenoid Bone Loss Measurement in Recurrent Shoulder Dislocation: Assessment of Measurement Agreement Between CT and MRI

BACKGROUND

Shoulder instability can cause both soft tissue injury and bone defects, requiring both computed tomography (CT) and magnetic resonance imaging (MRI) for a thorough workup, which results in high patient costs and radiation exposure. Prior studies in cadaveric and nonclinical models have shown promise in assessing preoperative bone loss utilizing MRI.

PURPOSE

To evaluate the utility of MRI in detecting and evaluating glenoid bone defects in a clinical setting. The aim was to establish whether similar information could be determined by utilizing MRI and CT in a population with recurrent instability.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

CT and MRI scans of 22 shoulders were read by 4 orthopaedic surgeons. The CT images were obtained on a 2-dimensional CT scanner. Vertical measurements were taken from the superior glenoid tubercle and directed inferiorly along the glenoid; horizontal measurements were taken across the widest part of the face of the glenoid and were perpendicular within one-half of 1° to the vertical measurement. The same protocol was followed for MRI measurements. An intraclass correlation coefficient (ICC) was calculated.

RESULTS

There was a moderate amount of agreement between examiners for the height measurements on MRI (ICC, 0.53) and a substantial agreement for the CT images (ICC, 0.64). The width measurements for MRI had a moderate amount of agreement (ICC, 0.41), while the CT images had a fair agreement (ICC, 0.39). The height measurements between the measurements of MRI and CT images had an overall ICC of 0.43, while the width measurements had an overall ICC of 0.41, both of which were considered a moderate amount of agreement.

CONCLUSION

There is moderate correlation between MRI and CT scans when measuring the glenoid, indicating that taking the length-to-height ratio measurements across the glenoid is a promising way to estimate the glenoid defect. At present, a complete workup of a patient with shoulder instability includes both a CT scan and an MRI. Future research that establishes precisely how MRI misestimates CT measurements of the glenoid can perhaps obviate the need for 2 scans.

The quantification of glenoid bone loss in anterior shoulder instability; MR-arthro compared to 3D-CT

OBJECTIVE

The purpose of this study is to investigate if magnetic resonance imaging with intra-articular contrast (MR-arthro) is as reliable as three-dimensionally reconstructed computed tomography imaging (3D-CT) in quantifying the glenoid bone loss in patients with anterior shoulder instability.

MATERIALS AND METHODS

Thirty-five patients were included. Sagittal MR-arthro and 3D-CT images of the glenoid surface were obtained pre-operatively. Two observers measured these images twice with OsiriX software in a randomized and blinded way. The intraclass correlations (ICC) of the intra- and inter-observer reliability within one method and an additional Bland-Altman plot for calculating agreement between the two methods were obtained.

RESULTS

The joint estimates of the intra-observer reliability, taking into account the data from both observer A and B, for 3D-CT and MR-arthro were good to excellent. The intra-observer reliability was 0.938 (95% CI: 0.879, 0.968) for 3D-CT and 0.799 (95% CI: 0.639, 0.837) for MR-arthro. The inter-observer reliability between the two observers within one method (3D-CT or MR-arthro) was moderate to good. 3D-CT: 0.724 (95% CI: 0.236, 0.886) and MR-arthro: 0.534 (95% CI: 0.128, 0.762). Comparing both the 3D-CT and MR-arthro method, a Bland-Altman plot showed satisfying differences with the majority of outcomes (89%) within 1 SD.

CONCLUSIONS

Good to excellent intra- and moderate to good inter-observer correlations and a satisfying Bland-Altman plot when compared to 3D-CT show tendencies that MR-arthro is reliable and valid for measuring bony defects of the glenoid.

Techniques to evaluate glenoid bone loss

Assessing glenoid morphology as well as quantifying bone loss is critical when treating patients with recurrent anterior glenohumeral instability because this greatly affects surgeons surgical planning. Although many surgeons agree that 3-dimensionally reconstructed computed tomography (3DCT) images with humeral head digitally subtracted has been considered to be a gold standard when assessing glenoid morphology, there are some surgeons who are making an attempt to replace computed tomography with magnetic resonance imaging to reduce cost for imaging studies and avoid possible radiation exposure, and demonstrated that MRI was equally valuable as 3DCT to quantify glenoid bone loss. However, the role of preoperative imaging study is not only quantifying glenoid bone loss but to assess the glenoid shape and morphology to facilitate surgeons stabilizing the shoulder. In this view, 3DCT is the most recommended preoperative imaging study for bony tissue which provides critical and substantial information of the glenoid.