Comparison of Glenoid Version and Posterior Humeral Subluxation in Patients With and Without Posterior Shoulder Instability

Concordance of Preoperative 3D Templating in Stemless Anatomic Total Shoulder Arthroplasty

INTRODUCTION

Recent advances in preoperative 3D templating software allow surgeons to plan implant size and position for stemless total shoulder arthroplasty (TSA). Whether these preoperative plans accurately reflect intraoperative decisions is yet unknown, and the purpose of this study was to evaluate concordance between planned and actual implant sizes in a series of patients undergoing stemless TSA.

METHODS

A retrospective cohort of consecutive, anatomic, stemless TSA cases performed by two surgeons between September 2019 and February 2021 was examined. Preoperative templated plans were collected using 3D planning software, and the sizes of planned glenoid, humeral head, and nucleus "stem" implants and other procedural data were recorded, along with sociodemographic information. These predicted parameters were compared with the implant sizes, and the concordance of these templated plans was quantified by direct comparison and bootstrapped simulations.

RESULTS

Fifty cases met inclusion criteria, among which perfect concordance across all three implants was observed in 11 cases (22%). The glenoid implant had the highest concordance (80%) relative to the humeral head and nucleus implants (38% and 60%, respectively), which was statistically significant ( P < 0.001). Planned humeral head implants were more often oversized relative to their actual implanted size. However, 84% of the planned humeral heads were within 1 diameter size; in addition, 98% of the planned glenoid implants were within one size and all were within 10 mm of the implanted glenoid backside radius. All nucleus implants were within one size.

DISCUSSION

Final implant sizes demonstrated variable concordance relative to preoperative plans, with glenoid implants having the highest accuracy and humeral heads having the highest variability. Multiple factors contributed to the varying concordances for the different implants, suggesting possible areas of improvement in this technology. These results may have implications for logistics, intraoperative efficiency, and overall cost and underscore the potential value of this technology.

LEVEL OF EVIDENCE

Level III.

The Effect of Glenoid Version on Glenohumeral Instability

In recent years, an appreciation for the dynamic relationship between glenoid and humeral-sided bone loss and its importance to the pathomechanics of glenohumeral instability has substantially affected modern treatment algorithms. However, comparatively less attention has been paid to the influence of glenoid version on glenohumeral instability. Limited biomechanical data suggest that alterations in glenoid version may affect the forces necessary to destabilize the glenohumeral joint. However, this phenomenon has not been consistently corroborated by the results of clinical studies. Although increased glenoid retroversion may represent an independent risk factor for posterior glenohumeral instability, this relationship has not been reliably observed in the setting of anterior glenohumeral instability. Similarly, the effect of glenoid version on the failure rates of surgical stabilization procedures remains poorly understood.

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.

Editorial Commentary: Posterior Shoulder Instability Surgical Treatment Outcomes Are Inferior to Outcomes of Anterior Instability: Standardization of Patient Evaluation and Indications Could Improve Results

Arthroscopic capsulolabral repair remains the mainstay of treatment in patients with refractory shoulder posterior instability. In addition, glenoid bone block augmentation procedures for posterior shoulder instability are gaining momentum. Unfortunately, results from anterior glenoid bone block augmentation procedures have enjoyed much better success than posterior, and it is unclear why surgical treatment of posterior instability with either congenital or acquired retroversion, with or without posterior bone loss, can result in complications or poor outcomes. It is essential to standardize evaluation and reporting of clinical presentation, radiographic assessment, indications, and mid- to long-term follow-up in patients who undergo posterior shoulder bony augmentation procedures. Current literature suggests that greater than 11% posterior glenoid bone loss increases risk of surgical failure 10 times, and 15% posterior bone loss increases risk of surgical failure 25 times, suggesting a possible threshold for posterior bony augmentation. However, in the end, the problem is complex, and work remains to better define optimal patient indications in consideration of congenital or acquired pathology, retroversion, amount of bone loss, and patient demographics and risk factors.

The Cartilage Wear Index: A new evaluation method to improve patient selection in surgical treatment of recurrent posterior glenohumeral instability

Background

The purpose of this study was to validate glenoid cartilage lesions as a negative prognostic factor and to define a new image-based preoperative evaluation method to identify surgical candidates for arthroscopic labral refixation with suture anchors in posterior shoulder instability.

Methods

Twenty-six patients who underwent arthroscopic posterior labral repair for shoulder instability were evaluated. Only patients with structural dynamic posterior instability were included. We evaluated on preoperative magnetic resonance arthrogram: glenoid version, humeral head subluxation, type of capsular insertion, and the cartilage lesions using the new Cartilage Wear Index (CWI). Two subgroups were analyzed with regard to the preoperative CWI and shoulder outcome scores: Single Assessment Numerical Evaluation (SANE) and Western Ontario Shoulder Instability Index (WOSI).

Results

The median age at operation was 28 (interquartile range = 21-33) years. Median overall postoperative outcome assessment demonstrated a SANE of 90 and a WOSI of 385. The median CWI was 1.02. Subgroup analysis revealed worse median WOSI and SANE scores in patients with a CWI >1.02 and a strong correlation between a high preoperative CWI and a higher postoperative WOSI score (R = 0.58; P = .038).

Conclusion

The CWI can be useful to identify patients who might obtain better outcomes when treated with arthroscopic labral repair in posterior shoulder instability.

The critical shoulder angle, the acromial index, the glenoid version angle and the acromial angulation are associated with rotator cuff tears

PURPOSE

To compare the critical shoulder angle (CSA), acromion index (AI), acromion angulation (AA) and glenoid version angle (GVA) between patients with full-thickness rotator cuff tears (RCTs) and patients with intact rotator cuffs.

METHODS

Between 2014 and 2018, the CSA, AI, AA and GVA were measured in consecutively included patients aged > 40 years who underwent shoulder arthroscopy for full-thickness RCTs. A total of 437 patients with RCTs and a mean age of 51.2 years (± 5.8) were included, 35.7% of whom were male. In the control group, there were n = 433 patients (36.3% male) with an intact rotator cuff, and the mean age was 50.7 years (± 5.3).

RESULTS

The mean AI for the RCT group was 0.7 ± 0.1, which was significantly higher than the mean AI for the control group (0.6 ± 0.1, p < 0.001). The mean CSA for the RCT group was 33.6° ± 3.9°, which was significantly higher than the mean CSA for the control group (31.5° ± 4°, p < 0.001). The mean AA for the RCT group was 13.9° ± 9°, which was significantly higher than the mean AA for the control group (12.4 ± 8.6, p = 0.012). The mean GVA for the RCT group was - 3.5° ± 4.6° and significantly retroverted compared with the mean GVA for the control group (- 2.2° ± 4.6°, p < 0.001). The cutoff values determined by the ROC curve analyses were as follows: 0.6 for AI, 31.4° for CSA, 9.6° for AA and - 2.6° for GVA.

CONCLUSION

The CSA, AI, GVA and AA values measured by MRI were determined to be significantly related to full-thickness rotator cuff ruptures. The AI, CSA, AA and GVA may be considered risk factors for degenerative rotator cuff tears. Assessing the CSA, AI, GVA and AA can be helpful for diagnostic evaluation of patients with full-thickness RCTs.

LEVEL OF EVIDENCE

III.

Decreased Glenoid Retroversion Is a Risk Factor for Failure of Primary Arthroscopic Bankart Repair in Individuals With Subcritical Bone Loss Versus No Bone Loss

PURPOSE

To determine whether glenoid retroversion is an independent risk factor for failure after arthroscopic Bankart repair.

METHODS

This was a retrospective review of patients with a minimum 2-year follow-up. In part 1 of the study, individuals with no glenoid bone loss on magnetic resonance imaging (MRI) and who failed arthroscopic Bankart repair (cases) were compared with individuals who did not fail Bankart repair (controls). In part 2 of the study, cases with subcritical (<20%) glenoid bone loss as measured on sagittal T1 MRI sequences who failed arthroscopic Bankart repair were compared with controls who did not. For each part of the study, glenoid version was measured using axial T2 MRI sequences. Positive angular measurements were designated to represent glenoid anteversion, whereas negative measurements were designated to represent glenoid retroversion. Independent t tests were conducted to determine the association between glenoid version and failure after arthroscopic Bankart repair.

RESULTS

There were 20 cases and 40 controls in part 1 of the study. In part 2, there were 19 cases and 21 controls. There was no difference in baseline characteristics between cases and controls. Among individuals with no glenoid bone loss, there was no difference in glenoid version between cases and controls (cases: 6.0° ± 8.1° vs controls: 5.1° ± 7.8°, P = .22). Among individuals with subcritical bone loss, cases (3.8° ± 4.4°) were associated with significantly less mean retroversion compared with controls (7.1° ± 2.8°, P = .0085). Decreased retroversion (odds ratio 1.34; 95% confidence interval 1.05-1.72, P = 20) was a significant independent predictor of failure using univariable logistic regression.

CONCLUSIONS

While glenoid retroversion is not associated with failure after arthroscopic Bankart repair in individuals with no glenoid bone loss, decreased retroversion is associated with failure in individuals with subcritical bone loss.

LEVEL OF EVIDENCE

Level 3: Retrospective review.

Effect of Posterior Glenoid Bone Loss and Retroversion on Arthroscopic Posterior Glenohumeral Stabilization

BACKGROUND

Posterior glenohumeral instability is an increasingly recognized cause of shoulder instability, but little is known about the incidence or effect of posterior glenoid bone loss.

PURPOSE

To determine the incidence, characteristics, and failure rate of posterior glenoid deficiency in shoulders undergoing isolated arthroscopic posterior shoulder stabilization.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

All patients undergoing isolated posterior labral repair and glenoid-based capsulorrhaphy with suture anchors between 2008 and 2016 at a single institution were identified. Posterior bone deficiency was calculated per the best-fit circle method along the inferior two-thirds of the glenoid by 2 independent observers. Patients were divided into 2 groups: minimal (0%-13.5%) and moderate (>13.5%) posterior bone loss. The primary outcome was reoperation for any reason. The secondary outcomes were military separation and placement on permanent restricted duty attributed to the operative shoulder.

RESULTS

A total of 66 shoulders met the inclusion criteria, with 10 going on to reoperation after a median follow-up of 16 months (range, 14-144 months). Of the total shoulders, 86% (57/66) had ≤13.5% bone loss and 14% (9/66) had >13.5%. Patients with moderate posterior glenoid bone loss had significantly greater retroversion (-11.5° vs -4.3°; P = .01). Clinical failure requiring reoperation was seen in 10.5% of patients in the minimal bone deficiency group and 44.4% in the moderate group (P = .024). There was no difference between groups in rate of military separation or restricted duty. Patients with moderate posterior glenoid bone deficiency were more likely to be experiencing instability instead of pain on initial presentation (P < .001), were more likely to have a positive Jerk test result (P = .05), and had increased glenoid retroversion (P = .01).

CONCLUSION

In shoulders with moderate glenoid bone deficiency (>13.5%) and increased glenoid retroversion, posterior capsulolabral repair alone may result in higher reoperation rates than in shoulders without bone deficiency.

Glenoid version is associated with different labrum tear patterns in shoulder instability

BACKGROUND

Previous studies have evaluated glenoid version as a risk factor for anterior and posterior shoulder instability. However, the association of glenoid version with combined anterior-inferior-posterior (>180°) labrum injuries is unknown. The purpose of the present study was to investigate various parameters of glenoid morphology, including version, in >180° labral tears and to compare these values with isolated anterior and isolated posterior tears.

METHODS

Magnetic resonance imaging studies from a consecutive series of shoulder instability patients were reviewed by 3 independent observers to measure the parameters of glenoid morphology including superior-inferior and anterior-posterior diameter, diameter ratio, glenoid version using the glenoid vault method, and percentage of glenoid bone loss using the best-fit circle method. These parameters were compared between patients with anterior (group 1), posterior (group 2), and >180° labral tears (group 3). Interobserver reliability coefficients were calculated for all measurements assessed.

RESULTS

There were statistically significant differences for all group comparisons regarding the glenoid version, with group 2 having the most retroversion (19.9° ± 4.71°) followed by group 3 (14.21° ± 4.59°) and group 1 (11.24° ± 5.3°). Group 3 showed the lowest amount of glenoid bone loss; however, the group differences did not reach statistical significance. There was also no statistically significant group difference for the other measured parameters. Interobserver reliability was in the good to excellent range for all measurements.

CONCLUSIONS

Combined anterior-inferior-posterior labral tears are associated with an increased amount of glenoid retroversion compared with isolated anterior labral tears. Isolated posterior labral tears have the largest amount of glenoid retroversion of all tear patterns.

Qualitative and quantitative analysis of glenoid bone stock and glenoid version: inter-reader analysis and correlation with rotator cuff tendinopathy and atrophy in patients with shoulder osteoarthritis

PURPOSE

Glenoid bone stock and morphology and rotator cuff muscle quality and tendon integrity affect the outcome of total shoulder arthroplasty. We hypothesized that glenoid bone loss correlates with rotator cuff muscle fatty infiltration (FI), tendinopathy, and atrophy.

DESIGN

Forty-three 3D CT scans and MRIs of 43 patients (mean age 62 years; SD 13 years; range 22-77 years) referred for primary shoulder pain were evaluated. Measurements of glenoid bone stock, version, and posterior humeral subluxation index (HSI) were assessed on an axial CT image reconstructed in the true scapular plane. Measurements utilized the Friedman line to approximate the pre-pathologic surface. Glenoid morphology was assigned by modified Walch classification. Rotator cuff FI, atrophy, and tendon integrity were assessed on corresponding MRIs.

RESULTS

There was a very strong negative correlation between increasing glenoid version and HSI (r = - 0.908; p < 0.0001). There was a moderately negative correlation between anterior bone loss and HSI (r = - 0.562; p < 0.0001) and a moderately positive correlation between posterior bone loss and HSI (r = 0.555; p < 0.0001). Subscapularis muscle FI correlated moderately with increased anterior and central bone loss and increased humeral head medialization (r = 0.512, p = 0.0294; r = 0.479, p = 0.033; r = 0.494, p = 0.0294; respectively). Inter-observer reliability (intra-class correlation coefficient [ICC] and kappa) was good to excellent for all measurements and grading.

CONCLUSION

Glenoid anteversion and anterior and posterior bone loss are associated with varying HSI. Subscapularis muscle FI, not tendon integrity, correlates to anterior and central glenoid erosion. The study adds evidence that neither rotator cuff tendinopathy nor muscle atrophy exhibits a significant relationship to HSI.

Correction to: Qualitative and quantitative analysis of glenoid bone stock and glenoid version: inter-reader analysis and correlation with rotator cuff tendinopathy and atrophy in patients with shoulder osteoarthritis

Purpose Glenoid bone stock and morphology and rotator cuff muscle quality and tendon integrity affect the outcome of total shoulder arthroplasty. We hypothesized that glenoid bone loss correlates with rotator cuff muscle fatty infiltration (FI), tendinopathy, and atrophy.Design Forty-three 3-D CT scans and MRIs of 43 patients (mean age 62 years; SD 13 years; range 22-77 years) referred for primary shoulder pain were evaluated. Measurements of glenoid bone stock, version, and posterior humeral subluxation index (HSI) were assessed on an axial CT image reconstructed in the true scapular plane. Measurements utilized the Friedman line to approximate the pre-pathologic surface. Glenoid morphology was assigned by modified Walch classification. Rotator cuff FI, atrophy, and tendon integrity were assessed on corresponding MRIs.Results There was a very strong negative correlation between increasing glenoid version and HSI (r = - 0.908; p < 0.0001). There was a moderately negative correlation between anterior bone loss and HSI (r = - 0.562; p < 0.0001) and a moderately positive correlation between posterior bone loss and HSI (r = 0.555; p < 0.0001). Subscapularis muscle FI correlated moderately with increased anterior and central bone loss and increased humeral head medialization (r = 0.512, p = 0.0294; r = 0.479, p = 0.033; r = 0.494, p = 0.0294, respectively). Inter-observer reliability (intra-class correlation coefficient [ICC] and kappa) was good to excellent for all measurements and grading.Conclusion Glenoid anteversion and anterior and posterior bone loss are associated with varying HSI. Subscapularis muscle FI, not tendon integrity, correlates to anterior and central glenoid erosion. The study adds evidence that neither rotator cuff tendinopathy nor muscle atrophy exhibits a significant relationship to HSI.

Posterior Shoulder Instability: Surgical Outcomes and Risk of Failure in Adolescence

BACKGROUND

Arthroscopic capsulolabral reconstruction has proven to be effective in treating posterior shoulder instability. Few studies have examined the risk factors that may contribute to poor outcomes in the adolescent population.

PURPOSE

To identify risk factors for surgical failure by comparing anatomic and subjective variations in children who underwent surgical intervention for posterior shoulder instability.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

All patients undergoing arthroscopic shoulder surgery at one institution between 2011 and 2018 were reviewed. Patients >18 years old at presentation and those with Ehlers-Danlos syndrome were excluded. Posterior instability was defined as unidirectional subluxation on posterior drawer testing while under anesthesia. Two-year minimum follow-up was required, but those whose treatment failed earlier were included for calculation purposes. Demographics and intraoperative findings were recorded, as were Single Assessment Numeric Evaluation (SANE) scoring, Pediatric and Adolescent Shoulder Survey (PASS), and the short version of the Disabilities of the Arm, Shoulder and Hand (QuickDASH) results. Major complication was defined as revision arthroscopy or redislocation, and minor complications included self-reporting a poor outcome score (eg, SANE score <65).

RESULTS

A total of 48 children (23 girls and 25 boys) met criteria, with a mean age of 16.5 years (range, 12.4-17.9 years) and a mean follow-up of 3.75 years. Fifteen (31.3%) patients had a complication by our criteria, including 12.5% with surgical failures; regarding major complications, boys were treated successfully 96% of the time and girls 78% of the time (P = .049). Of the anatomic and subjective variables tested, only younger age (P≤ .001) and presentation type (P < .05) were correlated with complications. SANE scores differed significantly (P < .002) by presentation type, with mean scores of 52 (trauma), 94 (recurrent instability), and 81 (pain). QuickDASH scores demonstrated patients with a history of trauma (mean, 37), instability (mean, 9), and pain (mean, 11).

CONCLUSION

Adolescents treated surgically for posterior shoulder instability are at risk of treatment failure (when including outcome scores), and it appears that patients of female sex, younger age, and traumatic presentation are at the highest risk to require revision surgery or experience continued limitations secondary to their shoulder.

Magnetic Resonance Imaging Correlates With Computed Tomography for Glenoid Version Calculation Despite Lack of Visibility of Medial Scapula

PURPOSE

To assess the accuracy of measuring glenoid version on magnetic resonance imaging (MRI) in the presence of varying amounts of the medial scapula body as compared with the gold standard of glenoid version measured on computed tomography (CT) imaging, including the entire scapula in a cohort of young patients with shoulder instability and without glenohumeral arthritis.

METHODS

A retrospective review was performed on instability patients with preoperative MRI and CT imaging. Measurements of available scapular width and glenoid version were performed using the Cobb angle method to measure the angle between the plane of the glenoid fossa to Friedman's line on axial images. Intra- and interrater reliability analysis was performed using intraclass correlation coefficients to assess agreement between MRI and CT measurements. Paired t tests were used to compare measurement differences between MRI and CT.

RESULTS

Thirty-two patients with both MRI and CT scans were assessed. Intra- and inter-rater assessment revealed strong agreement for scapular width measurement. For glenoid version measurement, intra-rater agreement was excellent and inter-rater agreement was moderate on CT and good on MRI. The mean available scapular body width was 24.7 mm longer on CT as compared with MRI (95% confidence interval 17.5-31.9, P < .0001; 109.8 ± 8.2 mm vs 85.1 ± 16.9 mm, respectively), with MRI having an average of 78.2% (±17.6%) of the CT scapular width shown on CT. No significant difference in glenoid version was found between MRI and CT (95% confidence interval -0.87 to 1.75, P = .499; MRI -2.57° vs CT -2.13°).

CONCLUSION

MRI provided significantly shorter available scapular widths when compared with CT imaging in a cohort of patients with glenohumeral instability and without arthritis. However, this failed to produce a significant difference of ≥5° in measured glenoid version compared with CT measurements when 75% (8 cm) of the scapular width was present on MRI. Measuring glenoid version on MRI does not appear to be significantly affected when the entirety of the medial border of the scapula is not included in the imaging field.

LEVEL OF EVIDENCE

Level III; study of diagnostic test.

Editorial Commentary: How Does Magnetic Resonance Imaging Stack up in Comparison to Computed Tomography Imaging for Measurement of Glenoid Version?

Computed tomography (CT) has been the gold standard for measuring glenoid version in patients with glenohumeral osteoarthritis or instability. However, few studies have compared measurements of glenoid version on magnetic resonance imaging (MRI) versus CT. Clinicians should feel confident in assessing glenoid version on MRI in the absence of CT imaging. In fact, MRI could be comparable to CT even in cases where the entire scapula is not visible on MRI. A 5° difference in glenoid version between imaging modalities represents a clinically significant difference.

Glenoid retroversion is an important factor for humeral head centration and the biomechanics of posterior shoulder stability

PURPOSE

Glenoid retroversion is a known independent risk factor for recurrent posterior instability. The purpose was to investigate progressive angles of glenoid retroversion and their influence on humeral head centration and posterior translation with intact, detached, and repaired posterior labrum in a cadaveric human shoulder model.

METHODS

A total of 10 fresh-frozen human cadaveric shoulders were investigated for this study. After CT- canning, the glenoids were aligned parallel to the floor, with the capsule intact, and the humerus was fixed in 60° of abduction and neutral rotation. Version of the glenoid was created after wedge resection from posterior and fixed with an external fixator throughout the testing. Specimens underwent three conditions: intact, detached, and repaired posterior labrum, while version of the glenoid was set from + 5° anteversion to - 25° retroversion by 5° increments. Within the biomechanical setup, the glenohumeral joint was axially loaded (22 N) to center the joint. At 0° of glenoid version and intact labrum, the initial position was used as baseline and served as point zero of centerization. After cyclic preloading, posterior translation force (20 N) was then applied by a material testing machine, while start and endpoints of the scapula placed on an X-Y table were measured.

RESULTS

The decentralization of the humeral head at glenoid version angles of 5°, 10°, 15°, and 20° of retroversion and 5° of anteversion was significantly different (P < 0.001). Every increment of 5° of retroversion led to an additional decentralization of the humeral head overall by (average ± SD) 2.0 mm ± 0.3 in the intact and 2.0 mm ± 0.7 in the detached labrum condition. The repaired showed significantly lower posterior translation compared to the intact condition at 10° (P = 0.012) and 15° (P < 0.01) of retroversion. In addition, CT measured parameters (depth, diameter, and native version) of the glenoid showed no correlation with angle of dislocation of each specimen.

CONCLUSION

Bony alignment in terms of glenoid retroversion angle plays an important role in joint centration and posterior translation, especially in retroversion angles greater than 10°. Isolated posterior labrum repair has a significant effect on posterior translation in glenoid retroversion angles of 5° and 10°. Bony correction of glenoid version may be considered to address posterior shoulder instability with retroversion > 15°.

Increased Glenoid Retroversion Is Associated With Increased Rotator Cuff Strength in the Shoulder

BACKGROUND

The rotator cuff muscles are critical secondary stabilizers in the shoulder. Increased glenoid retroversion and rotator cuff strength have been associated with the risk of posterior shoulder instability; however, the effect of increased glenoid retroversion on rotator cuff strength remains unclear.

PURPOSE/HYPOTHESIS

The purpose was to examine the association between glenoid version and rotator cuff strength in the shoulder in a young and healthy population with no history of shoulder instability. The hypothesis was that increased glenoid retroversion would be associated with increases in rotator cuff muscle strength.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A prospective cohort study was conducted over a 4-year period within a high-risk population to identify the risk factors for shoulder instability. Analyzed participants included 574 freshmen entering a United States service academy. Baseline data collected upon entry into the study included magnetic resonance imaging measurements of glenoid version. Rotator cuff strength was also assessed at baseline using a handheld dynamometer. Internal and external rotation strength were assessed with the glenohumeral joint positioned in neutral and in 45° of abduction. The current study represents an analysis of the baseline data from this cohort.

RESULTS

The mean age, height, and weight of participants was 18.77 ± 0.97 years, 176.81 ± 8.48 cm, and 73.80 ± 12.45 kg, respectively. The mean glenoid version at baseline was 7.79°± 4.85° of retroversion. Univariate linear regression analyses demonstrated that increased glenoid retroversion was associated with increased internal and external rotation strength of the rotator cuff in neutral and 45° of abduction (P < .001). Similar results were observed in multivariable models controlling for important confounding variables.

CONCLUSION

The results of this study demonstrate that as glenoid retroversion increases, internal and external rotation strength of the rotator cuff also increase in a young and healthy athletic population. These compensatory changes may contribute to increased glenohumeral dynamic stability in the presence of worse static stability with increasing retroversion.

Normal Range of Humeral Head Positioning on the Glenoid on Magnetic Resonance Imaging: Validation through Comparison of Computed Tomography and Magnetic Resonance Imaging

Background

To determine the normal range of humeral head positioning on magnetic resonance imaging (MRI).

Methods

We selected normal subjects (64 patients; group A) to study the normal range of humeral head positioning on the glenoid by MRI measurements. To compare the MRI measurement method with the computed tomography (CT), we selected group B (70 patients) who underwent both MRI and CT. We measured the humeral-scapular alignment (HSA) and the humeral-glenoid alignment (HGA).

Results

The HSA in the control group was 1.47 ± 1.05 mm, and the HGA with and without reconstruction were 1.15 ± 0.65 mm and 1.03 ± 0.59 mm, respectively, on MRI. In the test group, HSA was 2.67 ± 1.47 mm and HGA with and without reconstruction was 1.58 ± 1.16 mm and 1.49 ± 1.08 mm, on MRI. On CT, the HSA was 1.72 ± 1.01 mm, and HGA with and without reconstruction were 1.54 ± 0.96 mm and 1.59 ± 0.93 mm, respectively. HSA was significantly different according to image modality (p=0.0006), but HGA was not significantly different regardless of reconstruction (p=0.8836 and 0.9234).

Conclusions

Although additional CT scans can be taken to measure decentering in patients with rotator cuff tears, reliable measurements can be obtained with MRI alone. When using MRI, it is better to use HGA, which is a more reliable measurement value based on the comparison with CT measurement (study design: Study of Diagnostic Test; Level of evidence II).

Comparative analysis of 2 glenoid version measurement methods in variable axial slices on 3-dimensionally reconstructed computed tomography scans

BACKGROUND

Most glenoid version measurement methods have been validated on 3-dimensionally corrected axial computed tomography (CT) slices at the mid glenoid. Variability of the vault according to slice height and angulation has not yet been studied and is crucial for proper surgical implant positioning. The aim of this study was to analyze the variation of the glenoid vault compared with the Friedman angle according to different CT slice heights and angulations. The hypothesis was that the Friedman angle would show less variability.

MATERIALS AND METHODS

Sixty shoulder CT scans were retrieved from a hospital imaging database and were reconstructed in the plane of the scapula. Seven axial slices of different heights and coronal angulations were selected, and measurements were carried out by 3 observers.

RESULTS

Mid-glenoid mean version was -8.0° (±4.9°; range, -19.6° to +7.0°) and -2.1° (±4.7°; range, -13.0° to +10.3°) using the vault method and Friedman angle, respectively. For both methods, decreasing slice height or angulation did not significantly alter version. Increasing slice height or angulation significantly increased anteversion for the vault method (P < .001). Both interobserver reliability and intraobserver reliability were significantly higher using the Friedman angle.

CONCLUSION

Version at the mid and lower glenoid is similar using either method. The vault method shows less reliability and more variability according to slice height or angulation. Yet, as it significantly differs from the Friedman angle, it should still be used in situations where maximum bone purchase is sought with glenoid implants. For any other situation, the Friedman angle remains the method of choice.

Patellofemoral pain syndrome in female athletes: A review of diagnoses, etiology and treatment options

Patellofemoral pain syndrome (PFPS) is one of the most common causes of knee pain and is present in females disproportionately more relative to males. PFPS causes tend to be multifactorial in nature and are described in this review. From a review of the current literature, it is clear that there needs to be further research on PFPS in order to better understand the complex etiology of this disorder in both males and females. It is known that females with patellofemoral pain syndrome demonstrate a decrease in abduction, external rotation and extension strength of the affected side compared with healthy patients. Conservative management, including optimizing muscle balance between the vastus medialis and lateralis around the patella along with formal therapy should be the first line of treatment in patients presenting with PFPS. Surgery should be reserved for patients in which all conservative management options have failed. This review aims to guide physicians in accurate clinicaldecision making regarding conservative and surgical treatment options when specifically faced with PFPS in a female athlete. Furthermore, we will discuss the anatomic variants, incidence and prevalence, etiology, diagnosis and treatment of PFPS.

Arthroscopic treatment of posterior shoulder instability in patients with and without glenoid dysplasia: a comparative outcomes analysis

BACKGROUND

The purpose of this study was to evaluate the influence of glenoid dysplasia on outcomes after isolated arthroscopic posterior labral repair in a young military population.

METHODS

Thirty-seven male patients who underwent arthroscopic posterior labral repair for symptomatic posterior shoulder instability were evaluated at a mean duration of 3.1 years. A comparative analysis was performed for those with glenoid dysplasia and without dysplasia. Additional factors analyzed included military occupational specialty (MOS), preoperative mental health clinical encounters and mental health medication use, and radiographic characteristics (version, posterior humeral head subluxation, and posterior capsular area) on a preoperative standard shoulder magnetic resonance arthrogram. The groups were analyzed with regard to shoulder outcome scores (subjective shoulder value [SSV], American Shoulder and Elbow Surgeons [ASES] rating scale, Western Ontario Shoulder Instability Index [WOSI]), need for revision surgery, and medical separation from the military.

RESULTS

Of 37 patients, 3 (8.1%) underwent revision surgery and 6 (16%) underwent medical separation. Overall outcome assessment demonstrated a mean SSV of 67.9 (range, 25-100) ± 22.1, mean ASES of 65.6 (range, 15-100) ±  22, and mean WOSI of 822.6 (range, 5-1854) ± 538. There were no significant differences in clinical outcome scores between the glenoid dysplasia and no dysplasia groups (SSV, P = .55; ASES, P = .57; WOSI, P = .56). MOS (P = .02) and a history of mental health encounters (P = .04) were significantly associated with diminished outcomes.

CONCLUSIONS

The presence or absence of glenoid dysplasia did not influence the outcome after arthroscopic posterior labral repair in a young military population. However, a history of mental health clinical encounters and an infantry MOS were significantly associated with poorer clinical outcomes.

Editorial Commentary: More Evidence of the Importance of the Glenoid Labrum-Magnetic Resonance Imaging Reveals Its Possibility to Increase Both Version and Diameter of the Glenoid

An intact glenoid labrum has the possibility to increase both the version and the diameter of the glenoid, thus theoretically reducing the risk of instability.

Comparison of Magnetic Resonance Imaging and Computed Tomography Scans of the Glenoid Version in Anterior Dislocation of the Shoulder

The glenoid version is an important factor in the etiology of anterior dislocation of the shoulder and the planning of shoulder surgery. Few reports compare the magnetic resonance imaging (MRI) measurements of the glenoid version with those of computed tomography (CT). This study aimed to show that it is possible to use MRI instead of CT, which is accepted as the gold standard today for the evaluation of the glenoid version. A total of 55 patients with a history of 1 nonsurgically treated unilateral anterior dislocation of the shoulder who had both MRI and CT records for the dislocated shoulders constituted the study group. The glenoid version was measured in the axial plane on MRI and CT. Mean glenoid version measured by the observers was -1.6°±4.7° (95% confidence interval, -2.3° to -0.8°) and -1.8°±4.3° (95% confidence interval, -2.5° to -1.2°) by CT and MRI, respectively (P=.126). The evaluation of the CT and MRI measurements made by the 3 observers (X, Y, and Z) revealed no significant difference, as the P values of X CT - X MRI, Y CT - Y MRI, and Z CT - Z MRI were .550, .406, and .238, respectively. Interclass correlation among the 3 observers for CT and MRI was 0.996 and 0.981, respectively. The imaging methods of MRI and CT can be interchangeably used in the evaluation of the glenoid version in cases of anterior dislocation of the shoulder. [Orthopedics. 2017; 40(4):e687-e692.].