The Dimensions of the Scapula Glenoid in Japanese Rotator Cuff Tear Patients

Factors affecting stress shielding and osteolysis after reverse shoulder arthroplasty: A multicenter study in a Japanese population

BACKGROUND

Stress shielding and osteolysis around the humeral stem after reverse shoulder arthroplasty causes loosening and periprosthetic fractures and reduces bone stock during revision surgery. In Japanese patients, who have relatively small bodies, different characteristics may exist regarding the occurrence of these changes compared with the characteristics of Westerners, who have relatively larger frames. The purpose of this multicenter study was to investigate the incidence and clarify the predictors of stress shielding and osteolysis in Japanese individuals who underwent reverse shoulder arthroplasty.

METHODS

The occurrence of stress shielding and osteolysis was investigated in 135 shoulders that had undergone reverse shoulder arthroplasty at least 2 years prior in five Japanese hospitals. During post-surgical follow-up, which was conducted every 3 months, the locations of the stress shielding occurrences, such as cortical thinning and osteopenia (which primarily occurred in zones 1, 2, and 7, where 1 is the greater tuberosity and 7 is the calcar part), spot weld, and condensation lines, were recorded. Cases without any abnormal findings on radiographs obtained up to ≥2 years after surgery were regarded as having no abnormalities. Finally, the predictors of cortical thinning and proximal humeral osteolysis were assessed using univariate and multivariate regression analyses.

RESULTS

Cortical thinning and osteopenia occurred in 68 shoulders, a condensation line occurred in 37 shoulders, and spot weld occurred in 23 shoulders. In particular, greater tuberosity and calcar osteolysis occurred in 40 and 47 shoulders, respectively. Long stem, cementless stem, and a larger proximal filling ratio were independent predictors of cortical thinning and osteopenia, whereas a cementless stem, larger metaphysis diameter, and a larger proximal filling ratio were associated with proximal humeral osteolysis.

CONCLUSIONS

The predictors of stress shielding and osteolysis included the use of long stems, cementless stems, larger proximal filling ratios, and larger metaphysis diameters.

LEVEL OF EVIDENCE

retrospective comparative study (Level III).

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.

Three-dimensional morphometric analysis of glenoid in the Indonesian population and its clinical significance

Background

Understanding glenoid morphometry is important in shoulder prosthetic replacement surgery. In total and reverse shoulder arthroplasty, the size of the implants has to be determined according to the morphometry of the shoulder. However, there has been no known data on glenoid morphometry in the Indonesian population.

Methods

Seventy-four computed tomography scans of asymptomatic shoulders were obtained from the medical databases of a third referral hospital in Jakarta. Mimics Research 21.0 was used to reconstruct 3D models of the scapula from the DICOM files. The morphometry parameters included were glenoid fossa height (GFH), maximum glenoid fossa width (MGW), glenoid width at center of the glenoid fossa (CGW), vertical distance between maximum width and center (VDMC), glenoid version angle (GVA), glenoid inclination (GI), glenopolar angle (GPA), glenoid vault depth (GVD), coracoid length (CL), coracoid midpoint length (CML), coracoid tip height (CTH) and width (CTW), and coracoid midpoint height (CMH) and width (CMW).

Results

Our study found the average Indonesian GFH was 30.24 mm, the MGW was 24.03 mm, the CGW was 22.46 mm, the VDMC was 3.67 mm, the GPA was 42.76°, the GVD 18.8 mm, the GVA was 2.39° retroverted, the GI was 3.15° superiorly inclined, the CL was 37.76 mm, the CML was 18.89 mm, the CTW was 13.31 mm, the CTH was 8.52 mm, the CMW was 14.21 mm, and the CMH was 10.46 mm. All parameters except VDMC, GVA, and GI showed significant differences between male and female subjects Meanwhile, there was no significant difference in dimension and orientation of the glenoid and coracoid between the right and left shoulder.

Conclusion

Our study showed a lower value of MGW, GFH, and GVD compared to other Asian ethnicities. These results may be helpful in designing smaller prostheses suitable for Indonesian glenoids.

Surgeon-designed patient-specific instrumentation improves glenoid component screw placement for reverse total shoulder arthroplasty in a population with small glenoid dimensions

PURPOSE

Glenoid component loosening is a potential complication of reverse total shoulder arthroplasty (rTSA), occurring in part due to lack of adequate screw purchase in quality scapular bone stock. This study was to determine the efficacy of a surgeon-designed, 3D-printed patient-specific instrumentation (PSI) compared to conventional instrumentation (CI) in achieving longer superior and inferior screw lengths for glenoid component fixation.

METHODS

A multi-centre retrospective analysis of patients who underwent rTSA between 2015 and 2020. Lengths of the superior and inferior locking screws inserted for fixation of the glenoid baseplate component were recorded and compared according to whether patients received PSI or CI. Secondary outcomes included operative duration and incidence of complications requiring revision surgery.

RESULTS

Seventy-three patients (31 PSI vs. 42 CI) were analysed. Average glenoid diameter was 24.5 mm (SD: 3.1) and 81% of patients had smaller glenoid dimensions compared to the baseplate itself. PSI produced significantly longer superior (44.7 vs. 30.7 mm; P < 0.001) and inferior (43.0 vs. 31 mm; P < 0.001) mean screw lengths, as compared to CI. A greater proportion of maximal screw lengths for the given rTSA construct (48 mm) were observed in the PSI group (71.9% vs. 11.9% superior, 59.4% vs. 11.9% inferior). Operative duration was not statistically significantly different between the PSI and CI groups (150 min vs. 169 min, respectively; P = 0.229). No patients had radiographic loosening of the glenoid component with an average of 2-year follow-up.

CONCLUSION

PSI facilitates longer superior and inferior screw placement in the fixation of the glenoid component for rTSA. With sufficient training, PSI can be designed and implemented by surgeons themselves.

Glenoid Morphology and Related Parameters in Turkish Society

Introduction

Glenoid morphology may vary in different ethnic groups. Detection of these differences may be important in preoperative planning, especially in reverse shoulder arthroplasty. In this study, we investigated the mean glenoid size and retroversion in Turkish society and their relationship with the dominant side, gender, height, weight, and body mass index (BMI).

Materials and methods

Between 2019 and 2021, 102 shoulders of 51 patients (24 females/27 males, 51 left/51 right) who were included in shoulder joint imaging during thorax CT scanning were examined. Those with glenoid fracture, arthrosis, shoulder surgery or deformity, or younger than 18 years of age were not included in the study. The mean age was 41.69 (range: 18-73) years. Glenoid anterior-posterior diameter (D) and glenoid version (GV) were measured in axial slices, and glenoid height (H) was measured in coronal slices. The correlation of these parameters with gender, height, weight, and dominant side was examined.

Results

Mean D was 25.79±4.44 mm, mean H was 29.08±4.08 mm, and mean GV was -0.99°±0.92°. The mean height of the patients was 162±16.23 cm and the mean weight was 71.9±15.36 kg. The glenoid diameter and height were smaller in females, however, no statistically significant difference was found in the glenoid version (p<0.01, p<0.01, and p=0.92). The glenoid on the dominant side was statistically significantly more retroverted, whereas D and H were not associated with dominance (p<0.01, p=0.9, and p=0.98). It was found that the glenoid sizes were very highly correlated with the patient's height, and it was highly correlated with the patient's weight (p<0.01 and p<0.01). On the other hand, height and weight were not correlated with the glenoid version (p=0.47 and p=0.81, respectively). There was no statistically significant relationship between BMI and glenoid sizes and glenoid version (p=0.14 and p=0.46, respectively).

Conclusions

Females in Turkish society had small glenoid sizes. Male gender, height, and weight were positively correlated with large glenoids. The glenoid was more retroverted on the dominant side. These findings should be considered in preoperative planning in Turkish society.

Risk of penetration of the baseplate peg in reverse total shoulder arthroplasty for an Asian population

PURPOSE

Baseplate positioning may affect clinical outcome after reverse total shoulder arthroplasty (RTSA). The aim of this study was to evaluate the risk of penetration of the baseplate peg in RTSA.

METHODS

Forty-four patients with rotator cuff arthropathy or massive rotator cuff tears were included. Using their computed tomography data, ten insertion patterns of the baseplate pegs were simulated. First, in the axial plane, the baseplate was placed perpendicular to the Friedman axis (Friedman placement) and parallel to the glenoid surface (glenoid placement). Second, each of these placements were classified into the following groups: The baseplate peg was placed 2 mm anterior to the long axis of the glenoid (group A2), 1 mm anterior (group A1), on the long axis (group C0), 1 mm posterior (group P1), and 2 mm posterior (group P2). Cases in which the baseplate peg was within the scapular neck were defined as non-penetration, and the non-penetration rates among each group were evaluated and compared between sexes, and their relationship with patient height was evaluated.

RESULTS

In both the Friedman and glenoid placements, the non-penetration rate was significantly higher in groups A2 (68.2% and 70.5%) and A1 (65.9% and 65.9%) compared with groups P1 (18.2% and 29.5%) and P2 (9.1% and 13.6%; p < 0.001) and in males than in females (p < 0.05). Furthermore, the non-penetration rate tended to be higher as the patient's height increased.

CONCLUSIONS

It is recommended that the baseplate peg be placed anterior to the long axis of the glenoid.

3D printed patient specific customised surgical jig for reverse shoulder arthroplasty, a cost effective and accurate solution

INTRODUCTION

The reverse shoulder arthroplasty is a common orthopaedic procedure, where placement of the initial guiding wire is paramount to the implant instrumentation and position. To improve the position of the guiding wire, navigation and patient specific instrumentation have been used. These are however expensive and lengthy with many logistical issues.

MATERIAL AND METHODS

We utilised in house 3D printing to create a surgical guide to help with positioning of the central guiding wire. Pre and post op CT scans were utilised to determine positioning of the central screw.

RESULTS

Position of the screw tip was a mean of 3.3 mm away from the central point of the thickest portion of bone in the scapula with good bony purchase. There were no complications reported.

DISCUSSION

We report our experience in creation of the 3D printed surgical jig and the pearls of its creation, detailing from CT scan image acquisition to creation of surgical guide to intraoperative usage. 3D printing is a cost effective and accurate solution for the positioning of orthopaedic instrumentation. This can be easily applied to other operations in our institution, even with a low start up cost.

Anthropometrical study of the human glenoid in a normal Spanish population

OBJECTIVE

To evaluate the size of the glenoid in a southern Spanish population, to compare it with previous results from other populations and determine the size of the implants that are marketed for shoulder arthroplasty.

MATERIAL AND METHODS

Between January 2015 and December 2017, an anthropometrical study of the human glenoid was performed using computed axial tomography scans (CT) of 154 patients over 30 years old. The glenoid dimensions were analysed 3-dimensionally using 2mm interval thicknesses, determining the average height and width of the glenoid. The upper point of the glenoid geometry was determined as the supraglenoid tubercle of the ovoid glenoid surface, where the long head of the biceps tendon is thought to originate. The lower point was then positioned at the furthest point from the upper point on the glenoid contour. Anterior and posterior points were determined such that the 3-dimensional anterior-posterior distance was maximized on the plane perpendicular to the upper-lower axis. Sex differences and correlations between sides and among the respective parameters in the glenohumeral dimensions were also evaluated.

RESULTS

The glenoid had an average height of 28.78mm and width of 20.27mm. The values were significantly different between the men and the women, being greater in the men. The glenoid size is well correlated with the patient's size. Direct correlations exist between the glenoid height and width and the glenoid size and the patient's height. The available metaglenoids currently on the market are no bigger than 25-24mm.

CONCLUSION

In comparison, the southern Spanish population have a glenoid size similar to the Caucasian population, but smaller than that of the American population. The data shown could be useful to improve the design of shoulder prostheses for the southern Spanish population.

Predetermining glenoid dimensions using the scapular dimensions

BACKGROUND

Variations of morphology of the glenoid cavity have been previously reported. These influence the surgical reconstruction or arthroplasty of the shoulder. This study aims to study the variation of the shape of suprascapular notch, shape of glenoid cavity, dimensions of both the scapular and the glenoid cavity, and predict the glenoid dimensions from the scapular dimension parameters.

MATERIALS AND METHODS

Adult-dried scapulae were collected. The shapes of each suprascapular notch and glenoid cavity were evaluated. The scapular height, scapular width, glenoid superoinferior distance, and glenoid anteroposterior distance were measured using a digital vernier caliper, and statistical analysis was conducted on the data that were obtained.

RESULTS

There were 264 scapulae included in this study (166 male and 98 female). Most of the glenoid cavities were pear shaped (69.7%). The two most common types of suprascapular notches were small depression notches (31.8%) and the absence of notches (25.8%). The mean ± SD of scapular height, scapular width, glenoid superoinferior distance, and glenoid anteroposterior distance were 148.2 ± 10.0, 108.1 ± 6.4, 37.1 ± 2.2, and 27.4 ± 2.1 mm, respectively, in the male samples and 133.0 ± 7.0, 97.0 ± 5.2, 33.2 ± 1.9, and 23.7 ± 1.7 mm, respectively, in the female samples. The male scapulae were significantly larger than the female scapulae (p value < 0.05). However, there were no differences between the male and female scapulae in terms of scapular index or glenoid index (p value > 0.05). Scapular height and width were significantly associated with both the glenoid superoinferior distance (p = 0.0001) and glenoid anteroposterior distance (p value = 0.0001).

CONCLUSION

Scapular height and width can predict the dimensions of the glenoid. In cases of glenoid bone loss or shoulder arthroplasty, the native normal glenoid dimensions can be determined from the scapular dimensions as visualized using a true scapular anteroposterior radiograph. The surgeon can use these preoperative parameters when performing glenoid reconstruction or shoulder arthroplasty.