In patients with shoulder arthritis, the ability to accurately determine glenoid morphological alterations affects the outcomes of shoulder arthroplasty surgery significantly. This study was conducted to determine whether there is a correlation between scapular and glenoid morphometric components. Existence of such a correlation may help surgeons accurately estimate glenoid bone loss during pre-operative planning. The dimensions and geometric relationships of the scapula, scapula apophysis and glenoid were assessed using CT scan images of 37 South African and 40 Chinese cadavers. Various anatomical landmarks were marked on the 77 scapulae and a custom script was developed to perform the measurements. Intra-cohort correlation and inter-cohort differences were statistically analysed using IBM SPSS v28. The condition for statistical significance was p<0.05. The glenoid width and height were found to be significantly (p<0.05) correlated with superior glenoid to acromion tip distance, scapula height, acromion tip to acromion angle distance, acromion width, scapula width, and coracoid width, in both the cohorts. While anterior glenoid to coracoid tip distance was found to be significantly correlated to glenoid height and width in the South African cohort, it was only significantly correlated to glenoid height in the Chinese cohort. Significant (p<0.05) inter-cohort differences were observed for coracoid height, coracoid width, glenoid width, scapula width, superior glenoid to acromion tip distance, and anterior glenoid to coracoid tip distance. This study found correlations between the scapula apophyseal and glenoid measurements in the population groups studied. These morphometric correlations can be used to estimate the quantity of bone loss in shoulder arthroplasty patients

Introduction. The clinical impact of scapular notching is controversial. Some reports suggest it has no impact while others have demonstrated it does negatively impact clinical outcomes. The goal of this clinical study is to analyze the pre- and post-operative outcomes of 415 patients who received rTSA with one specific prosthesis (Equinoxe; Exactech, Inc). Methods. 415 patients (mean age: 72.2yrs) with 2 years minimum follow-up were treated with rTSA for CTA, RCT, and OA by 8 fellowship trained orthopaedic surgeons. 363 patients were deemed to not have a scapular notch by the implanting surgeon at latest follow-up (72.1 yrs; 221F/131M) whereas 52 patients were deemed to have a scapular notch at latest follow-up (73.3 yrs; 33F/19M). Outcomes were scored using SST, UCLA, ASES, Constant, and SPADI metrics; active abduction, forward flexion, and internal/external rotation were also measured to quantify function. Average follow-up was 38.1 months (No Notch: 37.2; Notch: 44.4). A two-tailed, unpaired t-test identified differences (p<0.05) in pre-operative, post-operative, and pre-to-post improvements. Results. The overall scapular notching rate was 12.5%. The rTSA cohort with a scapular notch had an average notching grade of 1.3 (41 grade 1, 6 grade 2, 5 grade 3, and 0 grade 4 notches). rTSA patients with a scapular notch on average weighed significantly less (168.0 vs. 154.7 lbs; p = 0.016) and had a significantly lower BMI (27.3 vs. 26.0; p = 0.032). 8 patients without scapular notching had a radiolucent line around the humeral component (2.2%); whereas, 5 patients with scapular notching had a radiolucent line around the humeral component (10.0%). Table 1 demonstrates no difference between the cohorts in pre-operative outcomes. Table 2 demonstrates rTSA patients without scapular notching were associated with significantly larger clinical outcome scores in all 5 metrics and also had significantly improved function according to 3 of the 6 measurements as compared to rTSA patients with scapular notching. Table 3 demonstrates only one significant difference was observed in pre-to-post improvement of outcome scores between cohorts. Finally, 27 complications were reported (6.5%), 20 for patients without scapular notching (5.5%) and 7 complications for patients with scapular notching (13.5%). Discussion and Conclusions. This large-scale clinical outcome study demonstrated that patients with scapular notching are associated with significantly poorer outcomes and a greater complication rate than patients without scapular notching at a similar average post-operative follow-up. The finding that patients with lower BMI were associated with a higher notching rate is new but also intuitive as these patients can likely adduct their arm more; it may also be that the lower average BMI and weight suggests that patients with notching were also more active. One additional new finding in this analysis is that patients with scapular notching had a 4.5X greater rate of radiolucent lines around the humeral component suggesting that the UHWMPE wear debris are related to the formation of humeral radiolucent lines. Additional and longer-term follow-up is needed to confirm these conclusions

Introduction. Snapping scapula symptoms occur due to disruption of the smooth gliding motion between scapula and thoracic cage. Patients present with pain in the scapulothoracic area aggravated by overhead and repetitive shoulder movements. It is often associated with audible and palpable crepitus, clicking, crunching, grating or snapping sensation. Open or arthroscopic scapulothoracic surgical treatment is an option when non-operative treatment modalities fail. The aim of our study was to assess the outcome of scapulothoracic arthroscopic treatment in patients with painful snapping scapula. Methods. Eight patients underwent scapulothoracic arthroscopic treatment for painful snapping scapula. Pre-operatively, all these patients had a trial of conservative treatment modalities for at least 6 months, consisting of activity modification, analgesia and physiotherapy for restoration of normal scapulothoracic kinematics. All patients had a temporary pain relief following a local anaesthetic and steroid injection. We graded the crepitus from 0 to 3 - 0 being no crepitus, 1 being palpable but not audible crepitus, 2 being soft audible crepitus and 3 being loud crepitus. Operations were performed with the patients in either prone or semi-prone position. The arm was placed in the “chicken wing” position (arm in full internal rotation with the hand placed on the back), so that the scapula lifted up from the chest wall. Two portals along the medial border of scapula were used for arthroscopy and instrumentation. In two cases a superior portal was also used. Outcome was assessed by pre and postoperative visual analogue score (VAS) and Oxford Shoulder Score. Pre and postoperative scores were compared using paired t-test. The significance level was set at P <. 05. Results. Of the eight patients included in our study, two were male and six were female patients. Mean age at the time of surgery was 26 years (range 16–34 years). Based on the preoperative clinical and MRI/CT findings and intra-operative arthroscopic findings, five had scapulothoracic bursectomy and 3 had bursectomy and shaving of superomedial border of scapula. Mean follow up was 5 months (Range 2 to 7 months). VAS score improved significantly from a mean of 9.4 preoperatively to 2.4 (P value .0002). There was also a significant improvement in Oxford Shoulder Score from a mean of 8.7 pre-operatively to 34.7 post operatively (P= .0001). Mean crepitus score significantly decreased from 2.6 to 0.3 (p <.0001). In six patients crepitus completely resolved. In two there was residual palpable crepitus but they had good pain relief. All eight patients were happy with the outcome of their surgery and will recommend this procedure to patients with similar symptoms. Conclusion. Arthroscopic scapulothoracic treatment provides significant pain relief and functional improvement for painful snapping scapula symptoms not responding to non surgical treatment modalities

Background. Glenoid baseplate fixation for reverse shoulder arthroplasty relies on the presence of sufficient bone stock and quality. Glenoid bone may be deficient in cases of primary erosions or due to bone loss in the setting of revision arthroplasty. In such cases, the best available bone for primary baseplate fixation usually lies within the three columns of the scapula. The purpose of this study was to characterise the relationship of the three columns of the scapula independent of glenoid anatomy and to establish the differences between male and female scapular anatomy. Methods. Fifty cadaveric scapulae (25 male, 25 female) were analysed using CT-based imaging software. The surface geometries of the coracoid, scapular spine and inferior scapular column were delineated in the sagittal plane. A linear best-fit line was drawn to establish the long axis of each column independent of the glenoid. The width of the glenoid was measured and points marked at the midpoint of each measurement. A best-fit line starting at the supra glenoid tubercle passing through the midpoints was chosen as the superior inferior (SI) axis of the glenoid. An orthogonal plane to the scapular plane was developed parallel to the glenoid face. The axis representing each of the three columns of the scapula and the SI axis of the glenoid, were projected onto this plane. The relationship between each column was analysed with respect to each other and with respect to the SI glenoid axis. Thus, measurements obtained gave the relationships of the three columns of the scapula (independent of the glenoid) and their relationships to the long axis of the glenoid (dependant on the glenoid). Comparisons were made between males and females using the independent t-tests. Results. The mean angle between the scapular spine and the coracoid column was 93±13° with no significant difference between males (91±15°) and females (95±10°) (p=0.29). The angle between the inferior scapular column and the scapular spine was 6.5° greater (p=0.03) in females (134±10°) than in males (128±11°). Similarly, the angle between the inferior scapular column and the coracoid column was 11° greater (p=0.009) in males (141±15°) than in females (130±12°). No significant sex difference was found between the acromion and inferior scapular pillar with respect to the SI glenoid axis. However, the female coracoid was found to be more horizontal than the male coracoid in relation to the SI axis of the glenoid (p=0.037). Conclusion. This study demonstrates that the relationship between the scapular spine and the coracoid column is independent of sex. However, sex has significant effects on the positions of the scapular spine and coracoid columns with respect to the inferior scapular column. The inferior scapular column is noted to be positioned more anterior (closer to the coracoid) in females than in males. Sex variations may be important when directing screws for baseplate fixation in bone deficient glenoids undergoing reverse shoulder arthroplasty

The purpose of this study is to quantify the distribution of bone density in the scapulae of patients undergoing reverse shoulder arthroplasty (RSA) to guide optimal screw placement. To achieve this aim, we compared bone density in regions around the glenoid that are targeted for screw placement, as well as bone density variations medial to lateral within the glenoid. Specimen included twelve scapula in 12 patients with a mean age of 74 years (standard deviation = 9.2 years). Each scapula underwent a computed tomography (CT) scan with a Lightspeed+ XCR 16-Slice CT scanner (General Electric, Milwaukee, USA). Three-dimensional (three-D) surface mesh models and masks of the scapulae containing three-D voxel locations along with the relative Hounsfield Units (HU) were created. Regions of interest (ROI) were selected based on their potential glenoid baseplate screw positioning in RSA surgery. These included the base of coracoid inferior and lateral to the suprascapular notch, an anterior and posterior portion of the scapular spine, and an anterosuperior and inferior portion of the lateral border. Five additional regions resembling a clock face, on the glenoid articular surface were then selected to analyze medial to lateral variations in bone density including twelve, three, six, and nine-o'clock positions as well as a central region. Analysis of Variance (ANOVA) tests were used to examine statistical differences in bone density between each region of interest (p < 0 .05). For the regional evaluation, the coracoid lateral to the suprascapular notch was significantly less dense than the inferior portion of the lateral border (mean difference = 85.6 HU, p=0.03), anterosuperior portion of the lateral border (mean difference = 82.7 HU, p=0.04), posterior spine (mean difference = 97.6 HU, p=0.007), and anterior spine (mean difference = 99.3 HU, p=0.006). For the medial to lateral evaluation, preliminary findings indicate a “U” pattern with the densest regions of bone in the glenoid most medially and most laterally with a region of less dense bone in-between. The results from this study utilizing clinical patient CT scans, showed similar results to those found in our previous cadaveric study where the coracoid region was significantly less dense than regions around the lateral scapular border and scapular spine. We also have found for medial to lateral bone density, a “U” distribution with the densest regions of bone most medially and most laterally in the glenoid, with a region of less dense bone between most medial and most lateral. Clinical applications for our results include a carefully planned trajectory when placing screws in the scapula, potentially avoiding the base of coracoid. Additionally, surgeons may choose variable screw lengths depending on the region of bone and its variation of density medial to lateral, and that screws that pass beyond the most lateral (subchondral) bone, will only achieve further purchase if they enter the denser bone more medially. We suspect that if surgeons strategically aim screw placement for the regions of higher bone density, they may be able to decrease micromotion in baseplate fixation and increase the longevity of RSA

Background. There has been increased focus on understanding the risk factors associated with scapular notching in reverse shoulder arthroplasty (RSA). The purpose of this study is to evaluate the effect of scapular morphology and surgical technique on the occurrence of scapular notching using the notching index as a comprehensive predictive tool. Methods. Ninety-one patients treated with a primary RSA were followed for a minimum of 24 months. Using a previously published notching index formula ((PSNA × 0.13) + (PGRD)), a notching index value for all patients was calculated. Radiographic assessment of patients were grouped by Nerot grade of scapular notching, group mean differences for prosthetic scapular neck angle (PSNA), peg glenoid rim distance (PGRD), preoperative scapular neck angle (SNA), notching index and clinical outcomes were compared. Results. Seventy-five (82%) of the ninety one shoulders in the study developed scapular notching. There was no significant difference in average notching index for group 1, 31.8 ± 4.4, and group 2, 33.1 ± 7.2. No significant difference was demonstrated between the groups for SNA (102.7° vs. 105.4°, p = 0.3), PSNA (125.8° vs. 124.5°, p = 0.82), PGRD (15.4 mm vs. 16.8 mm, p = 0.47) or in clinical outcomes between groups. Discussion. Our results demonstrated an overall low notch index that lacked specificity in predicting notching for this cohort. These results suggest that perhaps PSNA and prosthetic design are more significant contributors to notching with certain scapular morphology

Developments in adjuvant therapies and surgical techniques have allowed more confident excision of the neoplastic scapula without radical margins. Total scapular excision has been proven to be an effective limb salvage procedure for tumours involving the whole scapula, with or without gleno-humeral extension. The two most common types of excision are the Tikhoff-Linberg procedure or total scapulectomy. We identified 13 patients who had undergone total scapular excision between 1995 and 2008. Eight patients underwent total scapulectomy and five underwent a Tikhoff-Linberg procedure. All reconstructions were in the form of humeral suspension. There were four females and nine males with a mean age at operation of 47.7 years (range 16-81). Most tumours excised were either Ewing's sarcoma or chondrosarcoma and mean follow-up was 44 months (7-167). Functional outcomes were assessed using the Musculoskeletal Tumor Society Score (MSTS) and the Disabilities of the Arm, Shoulder and Hand Score (DASH). Active flexion and abduction ranges were also assessed. Of the original 13 patients, five died at a mean of 21 months post-operatively. One patient developed a recurrence after five months, which was successfully excised. The mean forward flexion and abduction following all procedures was 22.5 degrees (0-30) and 22.9 degrees (0-40) respectively. There was no statistical difference between ranges of motion of total scapulectomy and Tikhoff-Linberg procedures. The mean MSTS score for the entire group was 65.8% and there was no statistical difference between total scapulectomy and Tikhoff-Linberg (p = 0.69). The mean DASH score for all patients was 39.7 with no statistically significant difference between the two procedures (p = 0.46). Both procedures allow successful excision of scapular tumours with an acceptable level of post-operative function. Total scapulectomy and Tikhoff-Linberg procedures followed by humeral suspension compare favourably with forequarter amputation, endoprosthetic reconstruction and allografting

Introduction:. The complex 3D geometry of the scapula and the variability among individuals makes it difficult to precisely quantify its morphometric features. Recently, the scapular neck has been recognized as an important morphometric parameter particularly due to the role it plays in scapular notching, which occurs when the humeral component of a reverse shoulder arthroplasty (RSA) prosthesis engages the posterior column of the scapula causing mechanical impingement and osseous wear. Prosthetic design and positioning of the glenoid component have been accepted as two major factors associated with the onset of notching in the RSA patient population. The present image-based study aimed to develop an objective 3D approach of measuring scapular neck, which when measured pre-operatively, may identify individuals at risk for notching. Materials and Methods:. A group of 81 subjects (41 M, 69.7 ± 8.9 yrs.; 40 F, 70.9 ± 8.1 yrs.) treated with RSA were evaluated in this study. The 3D point-cloud of the scapular geometry was obtained from pre-operative computed tomography (CT) scans and rendered in Mimics. Subsequently, a subject-specific glenoid coordinate system was established, using the extracted glenoid surface of each scapula as a coordinate reference. The principal component analysis approach was used to establish three orthogonal coordinate axes in the geometric center of the glenoid. Utilization of glenoid-specific reference planes (glenoid, major axis, and minor axis plane) were selected in order to remove subjectivity in assessing “true” anterior/posterior and profile views of the scapula. The scapular neck length was defined as the orthogonal distance between the glenoid surface and the point on the posterior column with the significant change of curvature (Fig. 1). In addition, the angle between the glenoid plane, area center of the glenoid, and the point of significant change of the curvature were assessed (Fig. 2). This new parameter was developed to serve as a predictive critical value for the occurrence of notching. The incidence of notching increases as the value of the notching angle decreases. In order to evaluate relationships between glenoid and scapular neck, the glenoid width and height was also measured at the glenoid plane. Results:. Glenoid neck length and notching angle within the population were normally distributed with mean values of 7.8 ± 2.3 mm and 19.6 ± 4.8°, respectively (Fig. 3). No gender difference was found (p = 0.676). In one subject, a glenoid neck length of less than 1 mm was measured with the notching angle less than 2.5°. No association between glenoid neck length and glenoid size were identified (vs. glen. height r. 2. = 0.001, and vs. glen. width r. 2. = 0.05). Conclusion:. The present study reported on the scapular neck length and notching angle as measureable morphometric parameters that follow a normal distribution throughout the population and that are not correlated to the subject's glenoid size. Pre-operative acquisition of these novel and unique CT-based measurements may promote more appropriate RSA prosthesis selection to account for subject-specific anatomy in an effort to avoid scapular notching. Inferior placement of a baseplate or lateralization of glenoid component center of rotation (either biologically or mechanically) both serves to theoretically increase the notching angle

Background. Scapular notching is a complication after reverse shoulder arthroplasty with a high incidence up to 100%. Its clinical relevance remains uncertain; however, some studies have reported that scapular notching is associated with an inferior clinical outcome. There have been no published articles that studied positional relationship between the scapular neck and polyethylene insert in vivo. The purpose of this study was to measure the distance between the scapular neck and polyethylene insert in shoulders with Grammont type reverse shoulder arthroplasty during active external rotation at the side. Methods. Eighteen shoulders with Grammont type prosthesis (Aequalis Reverse, Tornier) were enrolled in this study. There were 13 males and 5 female, and the mean age at surgery was 74 years (range, 63–91). All shoulders used a glenosphere with 36mm diameter, and retroversion of the humeral implant was 10°in 4 shoulders, 15°in 3 shoulders, and 20°in 11 shoulders. Fluoroscopic images were recorded during active external rotation at the side from maximum internal to external rotation at the mean of 14 months (range, 7–24) after surgery. The patients also underwent CT scans, and three-dimensional glenosphere models with screws and scapula neck models were created from CT images. CT-derived models of the glenosphere and computer-aided design humeral implant models were matched with the silhouette of the implants in the fluoroscopic images using model-image registration techniques (Figure 1). Based on the calculated kinematics of the implants, the closest distance between the scapular neck and polyethylene insert was computed using the scapular model and computer-aided design insert models (Figure 2). The distance was computed at each 5° increment of glenohumeral internal/external rotation, and the data from 20°internal rotation to 40°external rotation were used for analyses. One-way repeated-measures analysis of variance was used to examine the change of the distance during the activity, and the level of significance was set at P < 0.05. Results. The mean glenohumeral abduction during the activity was 17°-22°. The mean distance between the neck and insert was approximately 1mm throughout the activity (Figure 3). The distance tended to become smaller with the arm externally rotated, but the change was not significant. Discussion. The reported incidence of scapular notching after Grammont type reverse shoulder arthroplasty is generally higher than the newer design prosthesis with the lateralized center of rotation. This may be associated with the design of the prosthesis, and the results of this study that the distance between the neck and insert was approximately 1mm throughout active external rotation at the side will support the high incidence of notching. We may need to analyze the distance with the newer design reverse shoulder prosthesis to prove the architectural advantage of the newer systems. Conclusion. The distance between the scapular neck and polyethylene insert was approximately 1mm throughout active external rotation activity in shoulders with Grammont type prosthesis

The purpose of this study was to determine if the use of a new 4 Dimensional CT scan aids the clinician in defining the size and area of the scapular bone to be removed arthroscopically in patients with Snapping Scapular Syndrome. From January 2009 – January 2011 nine consecutive patients with Snapping Scapular Syndrome were included. In six patients, (mean age 21±5 years, range 15–27) conservative treatment failed. These patients were positioned prone and demonstrated their snapping motion during the 7 seconds duration of the scan. The 4D CT machine scans 16 cm volumes in 0.3 seconds. It also scans motion, allowing a 3D reconstruction of the scapulothoracic joint, its’ movements and the dynamic area of impingement of the scapula on the surrounding structures. This scan has already improved arthroscopic removal of the supero-medial angle of the scapula. The scan showed in one case not only snapping of the superior medial angle of the scapula on the 2nd rib, but also extra bone impinging on the 3rd rib. Another case showed no real impingement but movement of the 2nd and 3rd rib by a tethering structure and a third case demonstrated impingement of the lateral third of the clavicle on the 2nd rib. The images provided by this new 4D CT scan offer greater pre-operative insight on the pathology in each individual patient with Snapping Scapular Syndrome. Therefore, we feel that it is a valuable addition to the assessment and treatment of these patients

Despite the high success rates of Reverse Shoulder replacements, complications of instability & scapular notching are a concern. Factors reducing relative motion of implant to underlying bone which include lateral offset to centre of rotation, screw & central peg insertion angle and early osteo-integration are maximized in the Trabecular Metal Reverse total shoulder system. We present clinico-radiological outcomes over 72 months. Analysis of a single surgeon series of 140 Reverse total shoulder replacements in 135 patients was done. Mean age was 72(range 58– 87 yrs); 81 females: 54 males. Indications were Rotator cuff arthropathy {n= 88} (63%); Osteo-arthritis with dysfunctional cuff {n= 22}(15%); post-trauma{n=23} (15%); revision from hemiarthroplasty {n=3} (2.4%) and from surface replacement {n=4} (2.8%). All patients were assessed using pre-operative Constants and Oxford scores and clinical & radiographic reviews with standard X-Rays at 6 weeks, 3, 6,12 months and yearly thereafter. X rays included an AP view in 45 degrees of external rotation and modified axillary view. Inferior Scapular notching using the Nerot-Sirveaux grades and Peg Glenoid Rim Distance were looked into by a consultant musculoskeletal radiologist/ Orthopaedic surgeon/ Senior Fellow (post CCT) or a specialist Trainee (ST4 and above). Pain on the visual analogue scale decreased by 98% (9.1 to 0.8) (p<0.01). Constant score improved by 81.8% (12.4 to 68.1) (p<0.05), Oxford shoulder score by 76.7% (56 to 13) (p<0.05). 95.6% of Humeral stems had no radiolucent lines and 4.4% had < 2mm of lucency. Scapular notching was calculated using Sirveaux grades with Peg scapular base angle distance (PSBA) measurements on PACS with Siemens calibration (grade 1= 4 (2.8%); grade 2 =1; grade 3 =0; grade 4=0). 3.57% showed radiographic signs of scapular notching at 72 months. Range of Peg Glenoid Rim Distance was 1.66 to 2.31 cm. Power analysis showed 65 patients were needed to have an 80% power to detect relation of Peg Glenoid Rim Distance to Scapular notching. A likelihood ratio test from Logistic regression model to check correlation of Peg Glenoid Rim Distance to Scapular notching gave a p value of 0.0005. A likelihood ratio from Logistic regression gave a p value of 0.0004 for Infraglenoid Scapular spurs. Highest incidence of spurring was seen in Reverse Total Shoulder Replacements done for Trauma and lowest in patients who got the procedure for Osteoarthritis. Complications included two glenosphere revisions; two stitch abscesses and two Acromial fractures in patients who had a fall two years after the procedure. Improved surgical outcomes can be attributed to surgical technique and implant characteristics. Trabacular metal promotes early osteointegration which resists shearing action of Deltoid on Glenoid component. This allows early mobilisation. Deltoid split approach preserves integrity of Subscapularis and Acromial osteotomy and lateral clavicle excision improve exposure and prevent Acromion fracture. Positioning the Glenoid component inferiorly on the Glenoid decreases incidence of Scapular notching. Our mid-term validated outcomes are promising with only 3.57% Grade I/II radiographic signs of scapular notching. Long term studies (10 year follow ups) are necessary to confirm its efficacy

Accurate and reproducible measurement of three-dimensional shoulder kinematics would contribute to better understanding shoulder mechanics, and therefore to better diagnosing and treating shoulder pathologies. Current techniques of 3D kinematics analysis use external markers (acromial cluster or scapula locator) or medical imaging (MRI or CT-Scan). However those methods present some drawbacks such as skin movements for external markers or cost and irradiation for imaging techniques. The EOS low dose biplanar X-Rays system can be used to track the scapula, humerus and thorax for different arm elevation positions. The aim of this study is to propose a novel method to study scapulo-thoracic kinematics from biplanar X-rays and to assess its reliability during abduction in the scapular plane. This study is based on the EOS™ system (EOS Imaging, Paris, France), which allows acquisition of 2 calibrated, low dose, orthogonal radiographs with the subject standing at 30 to 40° angle of coronal rotation to the plane of one of the X-ray beams, in order to limit superimposition with the ribcage and spine. Seven abduction positions in the scapular plane were maintained by the subjects for 10 seconds, during X-ray acquisition. Between two positions, the subjects returned at rest position. Arm elevations were approximately 0, 10, 20, 30, 60, 90 and 150° (position 1 to 7). Six subjects were enrolled to perform a reproducibility study based on the 3D reconstructions of 2 experienced observers three times each. For each subject, a personalised 3D reconstruction of the scapula was created. The observer digitises clearly visible anatomical landmarks on both stereoradiographs for each arm position. These landmarks are used to make a first adjustment of a parameterised 3D model of the scapula. This provides a pre-personalised model of the subject's scapula which is then rigidly registered on each pair of X-rays until its retroprojection fits best on the contours that are visible on the X-rays. The thorax coordinate system (CS) was built following the ISB (International Society of Biomechanics) recommendations. The CS associated to the scapula was a glenoid centred CS based on the ellipse which fit on the glenoid rim on the 3D model of scapula. Scapular CS orientation and translation in the thorax CS was calculated following a Y,X,Z angle sequence for each position. Each 3D reconstruction of the scapula was performed in approximately 30 minutes. The most reproducible rotation was upward/downward rotation (along X axis) with a 95% confidence interval (95% CI) from 2.71° to 3.61°. Internal/external rotation and anterior/posterior tilting were comprised respectively between 5.18° to 8.01° and 5.50° to 7.23° (CI 95%). The most reproducible translation was superior-inferior translation (along Y axis) with a 95% CI from 1.22mm to 2.46mm. Translation along X axis (antero-posterior) and Z axis (medio-lateral) were comprised respectively between 2.49mm to 4.26mm and 2.47mm to 3.30mm (CI 95%). We presented a new technique for 3D functional quantitative analysis of the scapulo-thoracic joint. This technique can be used with confidence; uncertainty of the measures seems acceptable compared to the literature. Main advantages of this technique are the very low dose irradiation compared to the CT-Scan and the possibility to study arm elevation above 120°

While reverse shoulder arthroplasty (RSA) is a reliable treatment option for patients with rotator cuff deficiency, loss of glenoid baseplate fixation often occurs due to screw loosening. We questioned whether an analysis of the trabecular bone density distribution in the scapula would indicate more optimal sites for screw placement. As such, the purpose of this study was to determine the anatomic distribution of trabecular bone density in regions of the scapula available for screw placement in RSA. Seven cadaveric shoulders were computed tomography (CT) scanned, and then voxels of the scapulae were isolated from the CT volume (Mimics 15.0 Materialise, Leuven, Belgium). Analyses were conducted in a common, 3D coordinate system. Volumetric regions of interest (ROI) within the scapula were identified based on potential baseplate screw sites. ROIs included areas at the base of the coracoid process lateral and inferior to the suprascapular notch, in the posterior and anterior lateral spine and in the anterosuperior and posteroinferior lateral border. Hounsfield Units (HU) were extracted from voxels corresponding to trabecular bone within each ROI. Overall bone density was summarised as the frequency of HU values above 80% of the ROI's maximum density value. Paired, two-tailed t-tests assuming unequal variance were used for pairwise comparisons (P≤0.05). Intra-region analyses compared two ROIs within the same broad anatomical structure; inter-region analyses compared ROIs between anatomical structures. Areas of the spine and lateral border of the scapula appeared to be denser than the coracoid process. Intra-region comparisons indicated no significant differences within ROI: coracoid P=0.43, spine P=0.95, lateral border P=0.41. ROI inferior to the suprascapular notch were on average 3.78% (P=0.08) and 6% (P=0.04) less dense than the anterosuperior and posteroinferior lateral border and 7.59% (P=0.006) and 7.72% (P=0.01) less dense than the anterior and posterior lateral spine. ROI lateral to the suprascapular notch were 6% (P=0.05) and 8.21% (P=0.02) less dense than the anterosuperior and posteroinferior lateral border and 9.8% (P=0.006) and 9.94% (P=0.008) less dense than the anterior and posterior lateral spine. There was no significant difference between the anterior spine and anterosuperior and posteroinferior lateral border (P=0.12, P=0.58), nor between the posterior spine and anterosuperior and posteroinferior lateral border (P=0.14, P=0.57). Results from this study indicate that the spine and lateral border of the scapula contain denser trabecular bone relative to regions in the coracoid. The higher quality bone of the spine and lateral border should be favoured over the coracoid process when fixing the glenoid baseplate in RSA. Further research may support the redesign of the glenoid baseplate geometry to better integrate the anatomy of the scapula and improve implant survival

INTRODUCTION. Automated MRI bone segmentation is one of the most challenging problems in medical imaging. To increase the segmentation robustness, a prior model of the structure could guide the segmentation. Statistical Shape Models (SSMs) are efficient examples for such application. We present an automated SSM construction approach of the scapula bone with an adapted initialisation to address the correspondences problem. Our innovation stems from the derivation of a robust SSM based on Watershed segmentation which steers the elastic registration at some critical zones. METHODS. The basic idea is to relate only corresponding parts of the shape under investigation. A sample from the samples set is chosen as a common reference (atlas), and the other samples are landmarked and registered to it so that the corresponding points can be identified. The registration has three levels: alignment, rigid and elastic transformations. To align two scapulae, we define a coordinate system, attach it to each scapula and align both systems. For this, we automatically locate three characteristic points on the scapula's surface. All samples are then scaled to the atlas and the rigid registration is determined by minimising the Euclidian distance between surfaces using Levenberg-Marquadt algorithm. Afterwards, the samples are locally deformed toward the atlas using directly their landmarks (traditional approach). Unfortunately, landmarks-correspondences could be mismatched at some anatomically complex, “critical,” zones of the scapula. To overcome such a problem, we suggest to 3D-segment these “critical” zones using a 3D Watershed-based method. Watershed is based on a physical concept of immersion, where it is achieved in a similar way to water filling geographic basins. We believe that this is a natural way to segment the surface of the scapula since it has two large “basins”: the glenoid and the subscapularis fossa. Watershed is followed by geometrical operations to establish eight separated zones on the surface of the scapula. Once we have the zones, surface-to-surface correspondence is defined and the landmarks' point-to-point correspondences are obtained within each zone pair separately. The elastic registration is then applied on the whole surface via a multi-resolution B-Spline algorithm. The atlas is built through an iterative procedure to eliminate the bias to the initial choice and the correspondences are identified by a reverse registration. Finally, the statistical model can be constructed by performing Principle Component Analysis (PCA). RESULTS. The framework was tested on a set of 14 surfaces of cadaveric scapulae. We calculate an error metric across all the set samples by registering each sample into the remainder of the samples using the traditional and the new approach. The error is calculated using the surface-to-surface correspondence to increase the reliability of the validation. Results show that using the new approach could significantly decrease the mean error and narrow its variance. On the other hand, it gives a “cleaner” SSM than the traditional one (i.e. it can carry more representative variations for a given set of samples.)

Background. Degeneration of the shoulder joint is a frequent problem. There are two main types of shoulder degeneration: Osteoarthritis and cuff tear arthropathy (CTA) which is characterized by a large rotator cuff tear and progressive articular damage. It is largely unknown why only some patients with large rotator cuff tears develop CTA. In this project, we investigated CT data from ‘healthy’ persons and patients with CTA with the help of 3D imaging technology and statistical shape models (SSM). We tried to define a native scapular anatomy that predesignate patients to develop CTA. Methods. Statistical shape modeling and reconstruction:. A collection of 110 CT images from patients without glenohumeral arthropathy or large cuff tears was segmented and meshed uniformly to construct a SSM. Point-to-point correspondence between the shapes in the dataset was obtained using non-rigid template registration. Principal component analysis was used to obtain the mean shape and shape variation of the scapula model. Bias towards the template shape was minimized by repeating the non-rigid template registration with the resulting mean shape of the first iteration. Eighty-six CT images from patients with different severities of CTA were analyzed by an experienced shoulder surgeon and classified. CT images were segmented and inspected for signs of glenoid erosion. Remaining healthy parts of the eroded scapulae were partitioned and used as input of the iterative reconstruction algorithm. During an iteration of this algorithm, 30 shape components of the shape model are optimized and the reconstructed shape is aligned with the healthy parts. The algorithm stops when convergence is reached. Measurements. Automatic 3D measurements were performed for both the healthy and reconstructed shapes, including glenoid version, inclination, offset and critical shoulder angle. These measurements were manually performed on the mean shape of the shape model by a surgeon, after which the point-to-point correspondence was used to transfer the measurements to each shape. Results. The critical shoulder angle was found to be significantly larger for the CTA scapulae compared to the references (P<0.01). When analyzing the classified scapulae significant differences were found for the version angle in the scapulae of group 4a/4b and the critical shoulder angle of group 3 when compared to the references (P<0.05). Conclusion. Patients with CTA have a larger critical shoulder angle compared with reference patients. Some significant differences are found between the scapulae from patients in different stages of CTA and healthy references, however the differences are smaller than the accuracy of the SSM reconstruction. Therefore, we are unable to conclude that there is a predisposing anatomy in terms of glenoid version, inclination or offset for CTA

Scapular spine fracture is a serious complication of reverse total shoulder arthroplasty (RTSA) often caused by a fall on an outstretched arm or a forced movement to the shoulder. The incidence of scapular fractures occurring after RTSA is reported between 5.8% and 10.2%. These fractures have been classified into 3 discrete fracture patterns. Avulsion of the anterior acromion (Type I), Acromion fractures (Type II) and Scapular spine fractures (Type III). This discussion will review the incidence of these post-operative peri-prosthetic fractures of the scapula after reverse TSA and describe potential treatment options and prevention methods to avoid this complication

Background:. While reverse shoulder arthroplasty (RSA) has shown successful outcomes for a variety of shoulder pathologies, postoperative scapula fractures continue to be one of the most common complications limiting outcomes with rates reported between 0.8–7.2%. Previous literature has shown that postoperative scapula fractures have a deleterious effect on elevation and outcomes scores, however these studies were all performed at short-term follow-up from the fracture. It has also not been shown whether postoperative scapular fractures increases risk of revision surgery. The purpose of this study was to determine the effect of postoperative scapula fracture on the outcomes following RSA at minimum 1 year follow-up from the fracture. Methods:. A retrospective, case-control study of 25 nonoperatively treated postoperative scapula fractures following RSA in a single surgeon's practice was analyzed with minimum 2 year follow-up from surgery and 1 year follow-up from fracture. Patients with postoperative scapula fractures were matched 1: 4 to a control group for age, sex, total follow-up time, indication for surgery, and primary versus revision surgery. Outcome measures including revision surgery, ASES score, and change in range of motion were compared between fracture cases and controls. Radiographic features including fracture location (acromion vs. scapular spine) and healing of fracture was also analyzed with respect to outcome. Results:. The incidence of postoperative scapula fracture following RSA in this series was 3.1% (32/1018). Fractures occurred from 1–94 months postoperatively, at an average of 16 months. Revision rate was higher in the fracture group (8%, 2/25) than in controls (2%, 2/100) but did not reach statistical significance (p = 0.18). Patients with fractures had inferior clinical outcomes with a postoperative ASES score of 58.0 compared to 74.2 in controls (p = 0.001), but were clinically improved from preoperative scores with an average improvement of 21 points. Improvement in range of motion was also decreased in the fracture group with a mean gain of forward elevation of 26° compared to 76° in controls (p < 0.001). Fracture location (acromion versus scapular spine) (p = 0.54) or healing (p = 0.40) did not affect outcome. Conclusion:. Postoperative scapula fractures may occur at any point during the postoperative period therefore increasing incidence is likely as longer follow-up becomes available. This complication leads to inferior clinical results compared to controls, however patients show improvement compared to their preoperative measurements, even at longer term follow-up. Patients sustaining postoperative scapula fractures may have increased risk of revision surgery

Introduction. Subject-specific finite element models (FEMs) allow for a variety of biomechanical conditions to be tested in a highly repeatable manner. Accuracy of FEMs is improved by mapping density using quantitative computed tomography (QCT) and choosing a constitutive relationship relating density and mechanical properties of bone. Although QCT-derived FEMs have become common practice in contemporary computational studies of whole bones, many density-modulus relationships used at the whole bone level were derived using mechanical loading of small trabecular or cortical bone cores. These cores were mechanically loaded to derive an apparent modulus, which is related to each core's mean apparent or ash density. This study used these relationships and either elemental or nodal material mapping strategies to elucidate optimal methods for scapular QCT-FEMs. Methods. Six cadaveric scapulae (3 male; 3 female; mean age: 68±10 years) were loaded within a micro-CT in a custom CT-compatible hexapod robot Pre- and post-loaded scans were acquired (spatial resolution = 33.5 µm) and DVC was used to quantify experimental full-field displacements (BoneDVC, Insigneo) (Figure 1).. Experimental reaction forces applied to the scapulae were measured using a 6-DOF load cell. FEMs were derived from corresponding QCT scans of each cadaver bone. These models were mapped with one of fifteen density-modulus relationships and elemental or nodal material mapping strategies. DVC-derived BCs were imposed on the QCT-FEMs using local displacement measurements obtained from the DVC algorithm. Comparisons between the empirical and computational models were performed using resultant reaction loads and full-field displacements (Figure 2). Results and Discussion. Reaction forces predicted by the QCT-FEMs showed large percentage error variations across all specimens and density-modulus relationships with elemental material mapping. The percentage errors were as large as 899%, but as low as 3=57% for the different specimens. Similarly, when using a nodal material mapping strategy, percentage errors were as large as 965%, but as low as 4=59% for the different specimens (Figure 3). For all specimens, minimal variation only occurred in the slope between the QCT-FEM and DVC displacements in the x and y directions for either elemental or nodal material mapping strategies. Slopes ranged from 0.86 to 1.06. This held true for 3 specimens in the z direction; however, for the remaining 3 specimens more pronounced variations occurred between the QCT-FEM and DVC displacements, dependent on density-modulus relationship. The r. 2. values were consistently between 0.82 and 1.00 for both material mapping strategies and density-modulus relationships for all three Cartesian components of displacement and all specimens. Conclusions. The results suggest that QCT-FEMs using DVC derived boundary conditions can replicate experimental loading of cadaveric specimens. It was also shown that only slight variations exist when either elemental or nodal material mapping strategies are adopted. Given the recent advancements provided by DVC-derived BCs, this study provides a basis for a common methodology that can be implemented in future studies comparing similar outcomes in all anatomic locations. Expanding the current sample size has the potential to determine if a single density-modulus relationship can exist or if specimen or anatomic location-specific relationships should be utilized. For any figures or tables, please contact the authors directly

Introduction

Acromial and scapular fractures are a rare but difficult complication with reverse total shoulder arthroplasty (rTSA), with an incidence rate reported from 1–10%. The risk factors associated with these fractures types is largely unknown. The goal of this study is to analyze the clinical outcomes, demographic and comorbidity data, and implant sizing and surgical technique information from 4125 patients who received a primary rTSA with one specific prosthesis (Equinoxe, Exactech, Inc) and were sorted based on the radiographic documentation of an acromial and/or scapula fracture (ASF) to identify factors associated with this complication.

Scapula fractures mostly occur following high energy trauma, however, the demographics are unknown in deployed soldiers. We analysed the incidence, aetiology, associated injuries, treatment and complications of these fractures in military personnel from Afghanistan and Iraq (2004–2014). Forty-four scapula fractures from 572 upper limb fractures (7.7%) were sustained. 85% were caused by blast or gunshot wounds and 54% were open blast fractures. Multiple injuries were noted including lung, head, vascular and nerve injuries. Injury Severity Scores were almost double compared to the average upper limb injury without a scapula fracture (21 vs. 11). Brachial plexus injuries (17%) have a favourable outcome following GSW compared to blast injuries. Glenoid fractures or floating shoulders were internally fixed (10%) and resulted from high velocity gunshot wounds or mounted blast ejections. There were no cases of deep soft tissue infection or osteomyelitis and all scapula fractures united. Scapula fractures have a 20 times higher incidence in military personnel compared to the civilian population. These fractures are often associated with multiple injuries, including brachial plexus injuries, where those sustained from blast have less favourable outcome. High rates of union following fixation and low rates of infection are expected despite significant contamination and soft tissue loss.