Does the innate relative size of the humeral head and glenoid affect the risk of anterior shoulder instability?

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.

Effect of Glenohumeral Joint Bone Morphology on Anterior Shoulder Instability: A Case-Control Study

PURPOSE

Glenohumeral joint compatibility and bone morphology are among the most critical factors in shoulder stabilization. Our study investigated the effect of the bone morphological structure of the shoulder joint on anterior shoulder dislocation.

METHODS

In our study, people with a history of shoulder dislocation were selected as the patient group. In the control group, patients with shoulder MRIs for any reason and no history of shoulder dislocation were included. Those who have a fracture around the shoulder, a congenital deformity in the shoulder region, arthrosis of the shoulder, those whose MRI images cannot be measured, those with Hill-Sachs lesion, connective tissue diseases (such as Ehler Danlos), who are unsure of their diagnosis, or who have incomplete and incorrect suspicious information in their patient file have been excluded. In our retrospective case-control study, glenoid width, glenoid height, glenoid's height-to-width ratio, glenoid's depth, glenoid's version, glenoid's inclination, humerus radius of curvature, glenoid radius of curvature, and bony shoulder stability ratio were measured on MRI images of the patients. The sample size for each group was determined using a power analysis method. The intra-class coefficient (ICC) assessed interobserver and intraobserver reliability.

RESULTS

A total of 80 patients, 40 each in the control and patient groups, were included in the study. Glenoid width was measured as 24.27 ± 1.58 in the patient group, 25.61 ± 1.72 in the control group; glenoid height was as measured 36.49 ± 2.26 in the patient group, 36.74 ± 1.99 in the control group; height-to-width ratio was measured as 1.5 ± 0.08 in the patient group, 1.43 ± 0.05 in the control group; glenoid version was as measured -0.53 ± 1.17 in the patient group, -1.44 ± 1.1 in the control group; glenoid inclination was measured as 1.44 ± 3.93 patient group, 2.64 ± 3.81 in the control group; glenoid depth was measured as 1.69 ± 0.41 in the patient group, 2.12 ± 0.53 in the control group; humerus radius of curvature was measured as 29.70 ± 6.76 in the patient group, 24.98 ± 3.22 in the control group; glenoid axial radius of curvature was measured as 61.8 ± 13.52 in the patient group, 52.53 ± 15.69 in the control group; glenoid coronal radius of curvature was measured as 43.01 ± 7.47 in the patient group, 37.74 ± 6.89 in the control group; the bony shoulder stability ratio was measured as 0.35 ± 0.06 in the patient group and 0.44 ± 0.06 in the control group. In the statistical evaluation, the glenoid width (p < 0.001), the glenoid height/width ratio (p < 0.001), the glenoid version (p < 0.001), the depth of the glenoid cavity (p < 0.001), and the radius of curvature measurements of the humeral head (p < 0.001) and the glenoid (axial, p < 0.007; coronal, p < 0.001) were found to be significantly different. Glenoid height and inclination were similar in both groups.

CONCLUSIONS

The detection of bone morphological features that constitute risk factors for shoulder dislocations plays an important role in preventing shoulder dislocations. In this way, it provides essential data on personalized rehabilitation programs and treatment selection for recurrent dislocations.

Does native glenoid anatomy predispose to shoulder instability? An MRI analysis

BACKGROUND

It is unclear if native glenohumeral anatomic features predispose young patients to instability and if such anatomic risk factors differ between males and females. The purpose of this study was to compare glenoid and humeral head dimensions between patients with a documented instability event without bone loss to matched controls and to evaluate for sex-based differences across measurements. The authors hypothesized that a smaller glenoid width and glenoid surface area would be significant risk factors for instability, whereas humeral head width would not.

METHODS

A prospectively maintained database was queried for patients aged <21 years who underwent magnetic resonance imaging (MRI) for shoulder instability. Patients with prior shoulder surgery, bony Bankart, or glenoid or humeral bone loss were excluded. Patients were matched by sex and age to control patients who had no history of shoulder instability. Two blinded independent raters measured glenoid height, glenoid width, and humeral head width on sagittal MRI. Glenoid surface area, glenoid index (ratio of glenoid height to width), and glenohumeral mismatch ratio (ratio of humeral head width to glenoid width) were calculated.

RESULTS

A total of 107 instability patients and 107 controls were included (150 males and 64 females). Among the entire cohort, there were no differences in glenoid height, glenoid width, glenoid surface area, humeral head width, or glenoid index between patients with instability and controls. Overall, those with instability had a greater glenohumeral mismatch ratio (P = .029) compared with controls. When stratified by sex, female controls and instability patients showed no differences in any of the glenoid or humerus dimensions. However, males with instability had a smaller glenoid width by 3.5% (P = .017), smaller glenoid surface area by 5.2% (P = .015), and a greater glenohumeral mismatch ratio (P = .027) compared with controls.

CONCLUSION

Compared with controls, males with instability were found to have smaller glenoid width and surface area, and a glenoid width that was proportionally smaller relative to humeral width. In contrast, bony glenohumeral morphology did not appear to be a significant risk factor for instability among females. These sex-based differences suggest that anatomic factors may influence risk of instability for male and female patients differently.

Similar scapular morphology in patients with dynamic and static posterior shoulder instability

Background

There is evidence that specific variants of scapular morphology are associated with dynamic and static posterior shoulder instability. To this date, observations regarding glenoid and/or acromial variants were analyzed independently, with two-dimensional imaging or without comparison with a healthy control group. Therefore, the purpose of this study was to analyze and describe the three-dimensional (3D) shape of the scapula in healthy and in shoulders with static or dynamic posterior instability using 3D surface models and 3D measurement methods.

Methods

In this study, 30 patients with unidirectional posterior instability and 20 patients with static posterior humeral head subluxation (static posterior instability, Walch B1) were analyzed. Both cohorts were compared with a control group of 40 patients with stable, centered shoulders and without any clinical symptoms. 3D surface models were obtained through segmentation of computed tomography images and 3D measurements were performed for glenoid (version and inclination) and acromion (tilt, coverage, height).

Results

Overall, the scapulae of patients with dynamic and static instability differed only marginally among themselves. Compared with the control group, the glenoid was 2.5° (P = .032), respectively, 5.7° (P = .001) more retroverted and 2.9° (P = .025), respectively, 3.7° (P = .014) more downward tilted in dynamic, respectively, static instability. The acromial roof of dynamic instability was significantly higher and on average 6.2° (P = .007) less posterior covering with an increased posterior acromial height of +4.8mm (P = .001). The acromial roof of static instability was on average 4.8° (P = .041) more externally rotated (axial tilt), 7.3° (P = .004) flatter (sagittal tilt), 8.3° (P = .001) less posterior covered with an increased posterior acromial height of +5.8 mm (0.001).

Conclusion

The scapula of shoulders with dynamic and static posterior instability is characterized by an increased glenoid retroversion and an acromion that is shorter posterolaterally, higher, and more horizontal in the sagittal plane. All these deviations from the normal scapula values were more pronounced in static posterior instability.