Reliable technique for acromion density assessment on CT.

INTRODUCTION: Acromial stress fracture (ASF) is an uncommon but acknowledged complication of reverse total shoulder arthroplasty (RTSA). There is no standardised method to directly measure the bone mineral density of the acromion to allow a detailed analysis of the potential mechanism of ASF. The aim is to establish a reliable and reproducible technique for measurement of acromial density on computer tomography (CT). METHODS: A retrospective review on CT scans obtained for three groups of patients: those planned for RTSA (n = 26); age and gender-matched non-operative (n = 26); and young non-operative patients (n = 28) were performed. Standardised axial images of 1 mm thickness at 1 mm increments were created following horizontal straightening on the coronal and sagittal views. To assess inter-rater reliability, two senior CT radiographers performed density measurements using standard region of interest (ROI) tool on the CTs with the ROI placed on the mid (ROI 1) and posterior (ROI 2) acromion. ROIs were selected as the most common locations for acromion fracture post RTSA. Measurements were repeated at least 6 weeks apart. Intra-class coefficients (ICC) were used to determine intra- and inter-rater reliability. RESULTS: ICCs demonstrated good to high intra-rater and inter-rater reliability for both ROI 1 and ROI 2 across all three groups. The lower margin of 95% confidence intervals was more than 0 for all intra-class coefficients. CONCLUSION: This study demonstrates a reliable method of measuring acromion density on CT. This method can be used to assess bone mineral density in the clinical setting and in future studies investigating ASF following RTSA.

The acetabularization index: a novel measure of acromial bone loss prior to reverse shoulder arthroplasty.

BACKGROUND: Acromial stress fractures following reverse shoulder arthroplasty (RSA) have gained attention among specialized surgeons over the past decades craving answers regarding predisposing factors and technical aspects as how to avoid the complication. This study introduces the acetabularization index (AI) for the preoperative estimation of acromial bone loss attributed to acetabularization in cases of cuff tear arthropathy (CTA). METHODS: The acromiohumeral interval (AHI), extent of acromial acetabularization (AA), acromial height (AH), and width of acetabularization (r) were measured on preoperative radiographs and two-dimensional computed tomography scans (2D CT) of patients who underwent RSA within the timeline 2019-2023 for CTA. The AI calculated AI % = AA mm ÷ AH mm . The CTA grade was determined according to the Hamada classification. The AI values on radiographs and 2D CT were compared by a Student's t-test. Possible correlation between the AI and AHI was investigated via Pearson's coefficient. The intraclass correlation coefficient (ICC) was employed to test the interobserver reliability among two independent testers. RESULTS: The radiographs and 2D CT scans of thirty-three patients who underwent RSA were analyzed. The mean AHI, AH, AA, r, and AI values on radiographs were 5.5 ± 2 mm, 10 ± 2 mm, 2 ± 2 mm, 30 ± 4 mm, 16 ± 16%, respectively. On 2D CT, the corresponding mean values were 4.7 ± 2.5 mm, 10.8 ± 2.65 mm, 2.45 ± 2.35 mm, and 30 ± 4.5, and 22.3 ± 22%, respectively. There was a statistically significant difference between the AI values on radiographs and 2D CT (P = .000). The Pearson's correlation coefficient demonstrated a negative correlation between AI and AHI (r = - 0.33). Excellent reliability was observed by the ICC values for all parameters in both groups among two testers. CONCLUSION: The AI is a reliably measurable tool on radiographs and 2D CT scans; however, the measurements derived from radiographs vary significantly from CT based measurements due to projection restrictions. Grade IVB of the Hamada/Fukuda classification is associated with the highest AI values. Further research is warranted to assess the clinical utility of this index as a predictive tool for postoperative acromial stress fractures.

Transcending Patient Morphometry: Acromiohumeral Interval to Glenoid Ratio as a Universal Diagnostic Tool for Massive Rotator Cuff Tears.

Background: Morphological differences among various ethnicities can significantly impact the reliability of acromiohumeral interval (AHI) measurements in diagnosing massive rotator cuff tears. This variation raises questions about the generalizability of AHI studies conducted in Western populations to the Asian population. Consequently, the primary objective of this study was to develop a novel parameter that can enhance the diagnosis of massive rotator cuff tears, irrespective of morphometric disparities between individuals of different ethnic backgrounds. Methods: A 10-year retrospective analysis of shoulder arthroscopic surgery patients was conducted, categorizing them into 3 groups based on intraoperative findings: those without rotator cuff tears, those with non-massive tears, and those with massive tears. AHI-glenoid ratio (AHIGR) was measured by individuals with varying academic backgrounds, and its diagnostic performance was compared to AHI. Sensitivity, specificity, accuracy, and intra- and inter-rater reliability were evaluated. Results: AHIGR exhibited significantly improved sensitivity, specificity, and accuracy as a diagnostic tool for massive rotator cuff tears, compared to AHI. A proposed cut-off point of AHIGR ≤ 0.2 yielded comparable results to AHI < 7 mm. Intra- and inter-rater reliability was excellent among different observers. Conclusions: AHIGR emerges as a promising diagnostic tool for massive rotator cuff tears, offering improved sensitivity and specificity compared to AHI. Its reproducibility among diverse observers underscores its potential clinical utility. While further research with larger and more diverse patient cohorts is necessary, AHIGR offers significant potential as a reference for enhancing the assessment of massive rotator cuff tears.

Critical shoulder angle and acromial index do not influence functional outcomes after repair of massive rotator cuff tears.

OBJECTIVES: Critical shoulder angle (CSA) and acromial index (AI) are two radiographic signs that can influence the risk of rotator cuff tears and the outcomes of repair. The purpose of this study was to determine the influence of CSA and AI on massive cuff tears and on the functional outcomes after repair. The hypothesis was that CSA and AI would be higher in posterosuperior compared to anterosuperior tears. METHODS: CSA and AI were retrospectively measured on radiographs of patients who underwent repair of two rotator cuff tendons. Functional outcomes were evaluated using the American Shoulder and Elbow Surgeons (ASES) score and Simple Shoulder Test (SST) at least six months postoperatively. Patients were divided according to the tendons repaired into anterosuperior group and posterosuperior group. Radiographic measurements and functional outcomes were compared. Patients in the posterosuperior group were subdivided into low or high CSA (cut-off value â€‹= â€‹39), and into low or high AI (cut-off value â€‹= â€‹0.75). All available preoperative magnetic resonance images were reviewed and graded according to Goutallier classification. Multivariate analysis was used to determine the influence of CSA, AI and Goutallier grade on functional outcomes. RESULTS: Eighty six patients were included. Both CSA and AI were statistically significantly higher in the posterosuperior group (p â€‹= â€‹0.0143 and 0.0052, respectively). After a mean follow-up of 33 months, ASES and SST were significantly better in patients with Goutallier grades 0-1 than grades>1 (multivariate p â€‹= â€‹0.03 and 0.009, respectively). No statistically significant differences were found between low and high CSA and AI groups in terms of functional outcomes of the posterosuperior group after repair (multivariate p â€‹= â€‹0.9). CONCLUSION: Higher CSA and AI seem to increase the risk of posterosuperior more than anterosuperior rotator cuff tears. Neither of these radiographic parameters influenced the functional outcomes of massive posterosuperior tears after repair. LEVEL OF EVIDENCE: Level III.

Relationship between scapular body morphology and rotator cuff tears: a threedimensional computed tomography study.

The purpose of this study was to identify the relationship between scapula morphology and rotator cuff tears (RCT). Hundred seventeen shoulders with and 87 shoulders without RCTs were included in this retrospective study. The critical shoulder angle (CSA) and lateral acromion angle in the coronal view, and the acromial coverage angle (ACA) and coracoid and scapular spine angle (CSSA) in the sagittal view were evaluated using 3-dimensional computed tomography. The glenoid anterior tilt, anterior acromial projection angle (AAPA), coracoid process angle, scapular spine angle (SSA), and inferior angle angle (IAA) with respect to the scapular plane were measured in the sagittal view. In univariate logistic regression analysis, CSA, ACA, AAPA, SSA, and IAA were significantly greater in shoulders with RCTs, whereas CSSA was greater in shoulders without RCTs. In multivariate logistic regression analysis, CSA and IAA were greater in shoulders with RCT and were significantly associated with this condition (P=.00073, P=.0032). This study has shown us that RCTs were associated with a greater curvature of the scapular body and greater CSA and IAA.

Risk Factors Analysis and Prediction of Rotator Cuff Tears: A Retrospective Study.

AIM: Rotator cuff tears (RCTs) are a major cause of shoulder pain and disability, affecting millions worldwide. Understanding the risk factors and developing reliable predictive measures for RCTs is essential for early diagnosis, targeted prevention, and effective treatment of this patient population. This study seeks to enhance our understanding by analyzing the acromiohumeral distance (AHD) and Constant-Murley Score (CMS) in patients with and without RCTs, thereby aiding the development of a predictive model aimed at improving clinical outcomes and prevention strategies in rotator cuff pathology. METHODS: This retrospective analysis involved 201 patients with shoulder pain, categorized into RCT (n = 72) and no RCTs (N-RCTs, n = 129) groups based on Magnetic Resonance Imaging (MRI) findings. We compared demographics, AHD, CMS, and rotator cuff status between groups and utilized logistic regression for identifying RCT predictors, leading to the development of a multifactorial predictive model. RESULTS: The mean AHD was 6.60 ± 1.12 mm. The RCT group showed a marginally higher AHD than the N-RCT group (p = 0.669). CMS scores were significantly lower in the RCT group (p < 0.001). Dominant side involvement (Odds Ratio (OR) 2.244), type III acromion (OR 6.106), and lower CMS (OR 0.938) significantly correlated with RCTs. The predictive model demonstrated an area under the curve (AUC) of 0.701 for RCT diagnosis. CONCLUSIONS: Reduced CMS, dominance of the affected side, and type III acromion emerged as key risk factors for RCTs. Our predictive model, incorporating these factors, holds promise for RCT diagnosis, with future studies needed for further validation.

Interobserver reliability of shoulder radiographic findings and correlation to MRI: a preliminary case series.

BACKGROUND: The aim of this study was to evaluate the interobserver reliability of measurements of the Acromiohumeral Distance (AHD) first described by Golding et al., the Critical Shoulder Angle (CSA), the Acromion Index with Glenoid Humeral (GH) and Glenoid Acromial (GA) distances, following the measuring method by Nyffeler et al., the Lateral Acromion Angle (LAA), as well as the morphology of the acromion according to Bigliani and the humeral head position according to Maloney in X-rays and MRI. Furthermore, the study assessed the correlation of measurement results in X-ray with those in MRI for AHD, CSA, GA, GH, AI, and LAA. METHODS: A total of 187 patients who underwent shoulder joint X-ray and MRI examinations from 09/2016 to 05/2023 were included in the study. Patients with poor imaging quality, arthrosis or radical prior surgeries, like shoulder prosthetic surgery, status post humerus fractures, that have undergone surgery and therefore changed the anatomical features were excluded, what lead to a total study population of 78. X-ray measurements were performed by two observers in the true anteroposterior view, so that the humeral head and the glenoid are shown without overlap, providing a clear view into the joint space. MRI measurements were performed in oblique coronal MRI slices, using the most accurately depicted glenoid surface as a landmark. RESULTS: Interobserver measurement results showed a significance with p < 0.001 for the assessment of acromion type according to Bigliani, humeral head offset assessment according to Maloney, and AHD. No significance was found for interobserver reliability in measuring LAA. Additionally, there was a high correlation of measurement results in X-ray with measurements in MRI for, CSA, GH/GA, and consequently AI, a good correlation for AHD but no correlation could be shown for LAA. CONCLUSIONS: These findings provide valuable insights into the robustness of radiological parameters for evaluating shoulder pathology, offering promising prospects for clinical applications and further research. Nevertheless, the specific methodological considerations and patient characteristics should be taken into account when interpreting the results to ensure their accurate application in clinical practice.

Evaluation of the Relationship between Acromiohumeral Distance and Supraspinatus Tendon Thickness Measured by Ultrasonography and Rotator Cuff Pathologies, Pain, and Function.

PURPOSE OF THE STUDY: In this study, we aimed to evaluate acromiohumeral distance (AHD) and supraspinatus tendon (ST) thickness measurements and their relationship with pain and function in ST pathologies. MATERIAL AND METHODS: The study included 111 patients and 25 healthy controls (HC). Patients were divided into 3 groups according to their diagnosis: non-tear tendinopathy (NTT), partial thickness tear (PTT), and full thickness tear (FTT). The AHD and ST thickness of the participants were measured with ultrasound. The pain and functional status of the patients were evaluated with the Numeric Rating Scale (NRS), The QuickDASH shortened version of the DASH Outcome Measure - Disabilities of the Arm Shoulder and Hand (QDASH), and Simple Shoulder Test (SST). RESULTS: The AHD value was significantly higher in the NTT group (p=0.000). The AHD value was significantly lower in the FTT group (p=0.000). ST thickness value was significantly lower in the PTT group compared to the NTT group (p=0.000). There was a positive correlation between ST thickness and BMI (r=0.553,p<0.01). There was a negative correlation between ST thickness and SST and a positive correlation between ST thickness (r=-0.223,p<0.05) and QDASH (r=0.276,p<0.05). CONCLUSIONS: We found that AHD and SST thicknesses significantly differed in the NTT, PTT, FTT, and HC groups. This difference may be important for diagnosis. In addition, the effect of obesity on ST thickness and the relationship between ST thickness and functional scores may be considered. Weight control may be effective at this point. KEY WORDS: acromiohumeral distance, supraspinatus tendon thickness, ultrasound.

Verification of acromion marker cluster and scapula spinal marker cluster methods for tracking shoulder kinematics: a comparative study with upright four-dimensional computed tomography.

BACKGROUND: This study validated the accuracy of the acromion marker cluster (AMC) and scapula spinal marker cluster (SSMC) methods compared with upright four-dimensional computed tomography (4DCT) analysis. METHODS: Sixteen shoulders of eight healthy males underwent AMC and SSMC assessments. Active shoulder elevation was tracked using upright 4DCT and optical motion capture system. The scapulothoracic and glenohumeral rotation angles calculated from AMC and SSMC were compared with 4DCT. Additionally, the motion of these marker clusters on the skin with shoulder elevation was evaluated. RESULTS: The average differences between AMC and 4DCT during 10°-140° of humerothoracic elevation were - 2.2° ± 7.5° in scapulothoracic upward rotation, 14.0° ± 7.4° in internal rotation, 6.5° ± 7.5° in posterior tilting, 3.7° ± 8.1° in glenohumeral elevation, - 8.3° ± 10.7° in external rotation, and - 8.6° ± 8.9° in anterior plane of elevation. The difference between AMC and 4DCT was significant at 120° of humerothoracic elevation in scapulothoracic upward rotation, 50° in internal rotation, 90° in posterior tilting, 120° in glenohumeral elevation, 100° in external rotation, and 100° in anterior plane of elevation. However, the average differences between SSMC and 4DCT were - 7.5 ± 7.7° in scapulothoracic upward rotation, 2.0° ± 7.0° in internal rotation, 2.3° ± 7.2° in posterior tilting, 8.8° ± 7.9° in glenohumeral elevation, 2.0° ± 9.1° in external rotation, and 1.9° ± 10.1° in anterior plane of elevation. The difference between SSMC and 4DCT was significant at 50° of humerothoracic elevation in scapulothoracic upward rotation and 60° in glenohumeral elevation, with no significant differences observed in other rotations. Skin motion was significantly smaller in AMC (28.7 ± 4.0 mm) than SSMC (38.6 ± 5.8 mm). Although there was smaller skin motion in AMC, SSMC exhibited smaller differences in scapulothoracic internal rotation, posterior tilting, glenohumeral external rotation, and anterior plane of elevation compared to 4DCT. CONCLUSION: This study demonstrates that AMC is more accurate for assessing scapulothoracic upward rotation and glenohumeral elevation, while SSMC is preferable for evaluating scapulothoracic internal rotation, posterior tilting, glenohumeral external rotation, and anterior plane of elevation, with smaller differences compared to 4DCT.

Acquired Acromion Compromise, Including Thinning and Fragmentation, Is Not Associated With Poor Outcomes After Reverse Shoulder Arthroplasty.

BACKGROUND: Acquired acromial compromise, including thinning (less than 30% of the normal acromion) or fragmentation resulting from acromiohumeral impingement or previous acromioplasty, is a concern in reverse shoulder arthroplasty (RSA). This condition may lead to shoulder pain and difficulties in arm elevation because of acromial insufficiency fracture. QUESTIONS/PURPOSES: (1) Do patients with acromial compromise (thinning less than 30% of normal acromion or fragmentation) have worse functional outcome scores, ROM, and strength after RSA compared with patients without acromial compromise? (2) Are patients with acromial compromise at a higher risk of complications such as acromial insufficiency fracture after RSA? (3) Do patients who develop acromial insufficiency fracture have predisposing associated factors and worse clinical outcomes? METHODS: Between January 1, 2016, and December 31, 2020, we treated 398 patients with RSA, and all patients were considered potentially eligible for this study. Our clinic is part of the orthopaedic department within a tertiary general hospital, serving patients from across the country. Among them, 49% (197 of 398) of patients were excluded for the following reasons: 8% (31 of 398) because of proximal humerus fracture, 5% (19 of 398) because of osteonecrosis, 9% (35 of 398) because of previous infective arthritis, 5% (18 of 398) because of a deformed shoulder, 4% (14 of 398) because of poor general condition after surgery, 3% (12 of 398) because of death, and another 17% (68 of 398) were lost before the minimum study follow-up, leaving 51% (201 of 398) for analysis. A preoperative acromial compromise was defined as follows: (1) thinning of the acromion (< 3 mm), which means a thickness of less than 30% of the normal acromion thickness (8 to 9 mm), and (2) acromial fragmentation. Acromial thickness was measured using a CT scan. The middle portion of the anterolateral acromion, situated lateral to the distal end of the clavicle, was crosschecked using the axial view. Measurements were subsequently performed from both coronal and sagittal views. In all, 29 patients with acromion compromise and 172 without acromion compromise met the inclusion and exclusion criteria. There was no differential loss to follow-up before 2 years between patients with and without acromial compromise in this study (36% [16 of 45] versus 23% [52 of 224]; p = 0.12). We matched patients using propensity score, pairing them in a 1:3 ratio based on gender, age, bone mineral density, diagnosis, previous rotator cuff repair surgery, subscapularis repair or latissimus dorsi transfer performed during surgery, the type of prosthesis used, and follow-up duration. Twenty-three patients with acromial compromise (acromion compromised group) and 69 patients without acromial compromise (normal control group) were matched; the mean ± SD duration of follow-up was 40 ± 22 months in those with acromial compromise and 43 ± 19 months the in normal control group. Pre- and postoperative functional outcome scores, ROM, and shoulder strength were compared. Shoulder scaption refers to lifting the arm in the scapular plane, and scaption strength was measured by applying upward force with the arm at 90° while seated, pushing it as far as possible and measured using a handheld myometer. Complications, including acromial insufficiency fracture, scapular notching, dislocation, periprosthetic infection, and overall risk of complication, were analyzed. Acromial insufficiency fracture was diagnosed based on clinical and radiological findings. Clinically, sudden pain and tenderness at the acromion along with reduced shoulder elevation raised acromial insufficiency fracture suspicion. Radiologically, acromion tilt on plain radiograph or fracture line on coronal CT view confirmed diagnosis of acromial insufficiency fracture. RESULTS: Comparing both groups, patients with a compromised acromion had no difference in American Shoulder and Elbow Surgeons scores (60 ± 12 versus 64 ± 12; mean difference -4 [95% CI -11 to 2]; p = 0.16), Constant scores (48 ± 10 versus 54 ± 12; mean difference -6 [95% CI -13 to 0]; p = 0.06), forward flexion degree (125 ± 24 versus 130 ± 21; mean difference -5 [95% CI -16 to 6]; p = 0.36), and scaption strength (5 ± 3 versus 6 ± 3; mean difference -1 [95% CI -3 to 0]; p = 0.13). Having acromial compromise was not associated with increased risk of overall complications (30% [7 of 23] versus 19% [13 of 69], relative risk 2 [95% CI 1 to 4]; p = 0.26). However, the only complication that was higher in the acromial compromised group was infection (13% [3 of 23] versus 0% [0 of 69], relative risk not available; p = 0.01). Only the lateralized glenoid prosthesis demonstrated negative association with the acromial insufficiency fracture occurrence; no other factors showed an association. The use of lateralized glenoid prostheses was not observed in patients with acromial insufficiency fracture (0% [0 of 7] acromial insufficiency fracture versus 39% [33 of 85] no acromial insufficiency fracture, relative risk 0 [95% CI 0]; p = 0.047). CONCLUSION: In patients with acquired acromial compromise-such as thinning or fragmented acromion because of advanced cuff tear arthropathy or previous acromioplasty-primary RSA resulted in no different functional outcome score, ROM, shoulder strength, and overall complications compared with patients without acromial compromise. Our findings suggest that a thin or fragmented acromion may not necessarily be exclusion criteria for RSA, potentially aiding surgeons in their decision-making process when treating these patients. However, one of the major complications, postoperative infection, is more frequently observed in patients with acquired acromial compromise. Pre- and postoperative caution would be necessary to prevent and detect infection even when short-term outcomes are favorable in this study. Further studies with large cohorts and long-term follow-up durations are needed. LEVEL OF EVIDENCE: Level III, therapeutic study.

Variations in the Anatomic Morphology of the Scapular Spine and Implications on Fracture After Reverse Shoulder Arthroplasty.

INTRODUCTION: This study evaluates the role of anatomic scapular morphology in acromion and scapular spine fracture (SSAF) risk after reverse shoulder arthroplasty (RSA). METHODS: Twelve scapular measurements were captured based on pilot study data, including scapular width measurements at the acromion (Z1), middle of the scapular spine (Z2), and medial to the first major angulation (Z3). Measurements were applied to 3D-CT scans from patients who sustained SSAF after RSA (SSAF group) and compared with those who did not (control group). Measurements were done by four investigators, and the intraclass correlation coefficient was calculated. Regression analysis determined trends in fracture incidence. RESULTS: One hundred forty-nine patients from two separate surgeons (J.L., A.M.) were matched by age and surgical indication of whom 51 sustained SSAF after reverse shoulder arthroplasty. Average ages for the SSAF and control cohorts were 78.6 and 72.1 years, respectively. Among the SSAF group, 15 were Levy type I, 26 Levy type II, and 10 Levy type 3 fractures. The intraclass correlation coefficient of Z1, Z2, and Z3 measurements was excellent (0.92, 0.92, and 0.94, respectively). Zone 1 and 3 measurements for the control group were 18.6 ± 3.7 mm and 3.2 ± 1.0 mm, respectively, compared with 22.5 ± 5.9 mm and 2.0 ± 0.70 mm in the SSAF group, respectively. The fracture group trended toward larger Z1 and smaller Z3 measurements. The average scapular spine proportion (SSP), Z1/Z3, was significantly greater in the control 6.20 ± 1.80 versus (12.60 ± 6.30; P < 0.05). Regression analysis showed a scapular spine proportion of ≤5 was associated with a fracture risk <5%, whereas an SSP of 9.2 correlated with a 50% fracture risk. DISCUSSION: Patients with a thicker acromions (Z1) and thinner medial scapular spines (Z3) have increased fracture risk. Understanding anatomic scapular morphology may allow for better identification of high-risk patients preoperatively.

The frequency of os acromiale in 751 shoulder MRI of Saudi population.

Background: Os acromiale (OA) is an uncommon pathology with a variable prevalence rate among different populations. Objectives: The aim of this study was to report the frequency of OA utilizing shoulder MRI of patients with shoulder pathology. Methods: It was a retrospective study. After obtaining our IRB approval, we gathered all shoulder and upper arm MRIs from the radiology department and evaluated them. Results: The prevalence of OA was found to be 3.32%. The mean age of the affected patients was 50.87 years (25-81). Conclusion: The rate of OA in patients presenting with shoulder pain is 3.32% in Saudi Arabia, which correlates with what has been previously reported in the literature.

Distribution and analysis of subacromial spurs and the relationship with acromial classification and angle in healthy individuals.

BACKGROUND: Subacromial spurs are considered the one of the pathology underlying shoulder impingement syndrome. Furthermore, few studies have focused on the morphology of the subacromial spurs in normal Chinese people. This study aimed to study the spur distribution and to illustrate the morphology of spurs, which may help guide the extent of acromioplasty. METHODS: A total of 93 normal individuals were enrolled, and both shoulders of all enrolled individuals were analyzed. The subjects were divided and classified into three different groups by ages: group I = 18-40 years, group II = 41-60 years, and group III ≥ 61 years. The osteophyte distribution, osteophyte area, subacromial surface area and osteophyte area/subacromial surface area ratio were measured and illustrated using Mimics and 3-matic software. The shape of the acromion was classified according to the Bigliani and Morrison classification system. The acromial angle was also classified. Then, the relationship between osteophytes, acromial classification and acromial angle was analyzed. RESULTS: Type II (curved shape) was the most common type of acromion, and the hooked shape was a rare form. A significant increase in the left subacromial surface area in males was observed in group III compared with group I (P < 0.001) and group II (P = 0.004). The total spur/subacromial area ratio was significantly higher in group II than I. An obvious increase in the right subacromial area was observed in group III compared with group I (P = 0.004). Furthermore, there was a significant increase in the right spur area (P = 0.021) and total spur/subacromial area ratio (P = 0.006) in females in group II compared with group I. Fewer spurs were observed on the left than on the right side (p = 0.0482). One spur was most common among type II acromions (29/36) (80.56%) on the left side and the right side (34/52, 65.38%). CONCLUSIONS: Spurs osteophytes are mainly distributed with an irregular shape and mostly run through the medial and lateral sides of the subacromial surface in normal subjects. The characteristics of subacromial spurs are so diverse that a surgeon must conduct subacromial decompression completely based on the morphology of individual spurs.

Bizarre parosteal osteocondromatous proliferation (BPOP) of the acromion with soft tissue recurrence.

Bizarre parosteal osteochondromatous proliferation (BPOP) is a benign but rare periosteal-originating chondrogenic tumor. It commonly arises from the hands and feet. It is slow-growing and often presents as a painless lump. On imaging, the mass is well-marginated and almost always remains contiguous with the cortical bone. Histologically, the lesion is composed of a disorganized admixture of fibrous tissue, bone, and cartilage with bizarre features. Treatment is surgical and local recurrence is common contiguous with bone. This case report demonstrates an uncommon acromial BPOP with the first reported recurrence not contiguous with the underlying cortex.

In Vivo Analysis of Acromioclavicular Kinematics and Distance During Multiplanar Humeral Elevation.

BACKGROUND: Knowledge of acromioclavicular (AC) joint kinematics and distance may provide insight into the biomechanical function and development of new treatment methods. However, accurate data on in vivo AC kinematics and distance between the clavicle and acromion remain unknown. PURPOSE/HYPOTHESIS: The purpose of this study was to investigate 3-dimensional AC kinematics and distance during arm elevation in abduction, scaption, and forward flexion in a healthy population. It was hypothesized that AC kinematics and distance would vary with the elevation angle and plane of the arm. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 19 shoulders of healthy participants were enrolled. AC kinematics and distance were investigated with a combined dual fluoroscopic imaging system and computed tomography. Rotation and translation of the AC joint were calculated. The AC distance was measured as the minimum distance between the medial border of the acromion and the articular surface of the distal clavicle (ASDC). The minimum distance point (MDP) ratio was defined as the length between the MDP and the posterior edge of the ASDC divided by the anterior-posterior length of the ASDC. AC kinematics and distance between different elevation planes and angles were compared. RESULTS: Progressive internal rotation, upward rotation, and posterior tilt of the AC joint were observed in all elevation planes. The scapula rotated more upward relative to the clavicle in abduction than in scaption (P = .002) and flexion (P = .005). The arm elevation angle significantly affected translation of the AC joint. The acromion translated more laterally and more posteriorly in scaption than in abduction (P < .001). The AC distance decreased from the initial position to 75° in all planes and was significantly greater in flexion (P < .001). The MDP ratio significantly increased with the elevation angle (P < .001). CONCLUSION: Progressive rotation and significant translation of the AC joint were observed in different elevation planes. The AC distance decreased with the elevation angle from the initial position to 75°. The minimum distance between the ASDC and the medial border of the acromion moved anteriorly as the shoulder elevation angle increased. CLINICAL RELEVANCE: These results could serve as benchmark data for future studies aiming to improve the surgical treatment of AC joint abnormalities to restore optimal function.

Robert H. Cofield, MD, Award for Best Oral Presentation 2023: Up to 8 mm of glenoid-sided lateralization does not increase the risk of acromial or scapular spine stress fracture following reverse shoulder arthroplasty with a 135° inlay humeral component.

BACKGROUND: Glenoid-sided lateralization in reverse shoulder arthroplasty (RSA) decreases bony impingement and improves rotational range of motion, but has been theorized to increase the risk of acromial or scapular spine fractures (ASFs). The purpose of this study was to assess if glenoid-sided lateralization even up to 8 mm increases the risk for stress fracture following RSA with a 135° inlay humeral component. METHODS: A retrospective review was performed from a multicenter prospectively collected database on patients who underwent primary RSA from 2015 to 2021. All RSAs were performed with a 135° inlay humeral component. Varying amounts of glenoid lateralization were used from 0 to 8 mm. Preoperative radiographs were reviewed for the presence of acromial thinning, acromiohumeral distance (AHD), and inclination. Postoperative implant position (distalization, lateralization, and inclination) as well as the presence of ASF was evaluated on minimum 1-year postoperative radiographs. Regression analyses were performed on component and clinical variables to assess for factors predictive of ASF. RESULTS: Acromial or scapular spine fractures were identified in 26 of 470 shoulders (5.5%). Glenoid-sided lateralization was not associated with ASF risk (P = .890). Furthermore, the incidence of fracture did not vary based on glenoid-sided lateralization (0-2 mm, 7.4%; 4 mm, 5.6%; 6 mm, 4.4%; 8 mm, 6.0%; P > .05 for all comparisons). RSA on the dominant extremity was predictive of fracture (odds ratio [OR] 2.21, 95% confidence interval [CI] 1.20-5.75; P = .037), but there was no relationship between patient age, sex, preoperative acromial thinning, or diagnosis and risk of fracture. Although there was no difference in mean postoperative AHD between groups (P = .443), the pre- to postoperative delta AHD was higher in the stress fracture group (2.0 ± 0.7 cm vs. 1.7 ± 0.7 cm; P = .015). For every centimeter increase in delta AHD, there was a 121% increased risk for fracture (OR 2.21, 95% CI 1.33-3.68; P = .012). Additionally, for every 1-mm increase in inferior glenosphere overhang, there was a 19% increase in fracture risk (P = .025). CONCLUSION: Up to 8 mm of glenoid-sided metallic lateralization does not appear to increase the risk of ASF when combined with a 135° inlay humeral implant. Humeral distalization increases the risk of ASF, particularly when there is a larger change between pre- and postoperative AHD or higher inferior glenosphere overhang. In cases of pronounced preoperative superior humeral migration, it may be a consideration to avoid excessive postoperative distalization, but minimizing bony impingement via glenoid-sided lateralization appears to be safe.

Variability in the distance between the suprascapular notch with the spine of the scapulae and the acromion.

INTRODUCTION: The suprascapular notch lies in the superior border of the scapula and is a passageway for the suprascapular nerve that is sensory to the shoulder joint. Suprascapular nerve block involves injection of local anaesthetic into the suprascapular notch, either ultrasound guided or blind, using the spine of scapula and/or the medial border of the acromion as surface landmarks. AIM: To investigate the anatomic variations that exist between the distance of the notch from the spine of scapula and acromion. METHOD: Ninety-two dry scapulae were measured with a digital calliper for their length of the spine, distance between the midpoint of the spine and base of the suprascapular notch and distance between the medial border of the acromion and the base of the suprascapular notch. These measurements were compared for variations in the scapular bony landmarks, the spine and the acromion to determine the site for the injection. RESULTS: Measurement reliability was assessed by intraclass correlation, Cronbach's alpha being 0.99, 0.97 and 0.91 for length of spine, distance from spine and distance from acromion respectively. The distance from the acromion had less variation in measurement (3.73 ± 0.42 cm) but a flatter distribution when compared to distance from the spine of the scapula (3.32 ± 0.39 cm). CONCLUSION: Length of the spine of the scapula appeared not to influence either distance from the acromion or distance from the spine of scapula. There is potential for greater variability in placement of nerve blocks that use acromion as the bony reference. Key Points • Dry scapular measurement using electronic Vernier callipers is accurate (0.91-0.97). • There is potential for greater variability in placement of blind nerve blocks that use acromion as the bony reference to locate the suprascapular notch.

Acromion fractures after reverse shoulder arthroplasty occur in predictable clusters.

BACKGROUND: Acromion and scapular spine fractures (ASFs) following reverse total shoulder arthroplasty (RSA) have been reported at a rate of 3.9%. The location of the fracture has been shown to be an important factor in determining the outcomes of nonoperative treatment, with medial fractures having worse outcomes than lateral fractures. As the debate between operative and nonoperative treatment continues, a more precise understanding of the location of the fracture is necessary for effective management. The purpose of this study was to use 3-dimensional computed tomography (CT) reconstruction to characterize the exact location of ASFs after RSA. METHODS: A retrospective review of 2 separate institutional shoulder and elbow repositories was performed. Patients with post-RSA ASFs documented by post-fracture CT scans were included. The query identified 48 patients who sustained postoperative ASFs after RSA between July 2008 and September 2021. CT scans of patients with ASFs were segmented using Mimics software. Eight patients were excluded because of poor image quality. Each bone model was manipulated using 3-Matic Medical software to align the individual scapula with an idealized bone model to create a view of scapular fracture locations on a normalized bone model. This model was used to classify the fractures using the modified Levy classification. RESULTS: The study cohort consisted of 40 patients with a diagnosis of postoperative ASF after RSA. The median age at the time of surgery was 76 years (interquartile range, 73-79 years). The cohort comprised 32 women (80%) and 8 men (20%), with a median body mass index of 27.8. Only 10 patients (25%) had a previous diagnosis of osteoporosis and 6 (13%) had a diagnosis of inflammatory arthritis; 53% of patients underwent RSA owing to rotator cuff tear arthropathy. The distribution of fracture locations was similar within the cohort. However, lateral fractures were slightly more prevalent. The most common fracture location was the type I zone, with 12 fracture lines (29%). There were 11 fracture lines (26%) in the type IIa zone, 10 (23%) in the type IIb zone, 0 in the type IIc zone, and 9 (21%) in the type III zone. CONCLUSION: ASFs after RSA occur in 4 predictable clusters. No fractures appeared to distinctly cluster in the type IIc zone, which may not represent a true fracture zone. Understanding the distribution of these fractures will help to enable the future design of implants and devices to stabilize the fractures that require fixation.

Ipsilateral fractures of the acromion and coracoid processes of the scapula.

A fracture of the acromion and coracoid processes of scapula is rarely seen in the outpatient clinic, due to the acromion's anatomical position and shape, as well as the strong ligaments and muscles that are attached to it. These fractures are caused by either direct or indirect high-energy trauma injuries to the shoulder joint, leading to severe pain and a grossly restricted range of motion. Several acromial classifications were reported, but this type of longitudinal plane fracture of the acromion process in our case is yet to be described in the current literature. We present a rare combination of the coracoid process and unstable acromion bony projection fractures that have not previously been noted for this type of fracture. The closest to this is Kuhn's type III classification. A 51-year-old male presented to our emergency department complaining of the right shoulder pain and difficulty raising his arm following a 2-wheeler accident. The patient was managed by open reduction and internal fixation with 3 cannulated cancellous screws fixation and progressed well with no postoperative complications. He was asymptomatic postoperatively and regained full range of motion after 4 months.

Changes in the Lateral Acromion Angle in Rotator Cuff Tear Patients with Acromioplasty.

BACKGROUND: Arthroscopic surgery has been established as an efficacious intervention for the treatment of rotator cuff tears. The primary aim of this study was to analyze the modifications in the lateral acromial angle (LAA) subsequent to rotator cuff repair surgery using single-row rivet fixation and double-row rivet fixation techniques. Furthermore, we sought to investigate the influence of LAA on the prognosis of rotator cuff repair surgery. METHOD: This observational study retrospectively enrolled 105 patients diagnosed with degenerative rotator cuff tears who underwent arthroscopic rotator cuff repair between 2016 and 2019. Following the exclusion of two patients with subscapularis or superior labrum anterior and posterior (SLAP) tears, as well as three patients who were lost to follow-up, a cohort of 100 patients was included for clinical and imaging evaluation. Among these individuals, 50 were assigned to the double-row repair group, whereas the remaining 50 comprised the single-row repair group. Bilateral shoulder magnetic resonance imaging (MRI) scans were conducted no less than 24 months post-surgery. Experienced arthroscopic surgeons, blinded to the LAA measurements, assessed the rotator interval (RI) using a control MRI. Functional assessment was performed using the University of California, Los Angeles (UCLA) quick disability of the shoulder and arm, shoulder and hand (qDASH) score. The Wilcoxon signed-rank test for dependent samples was employed to compare data between the pre- and post-intervention groups. Pearson correlation coefficients were calculated to evaluate the relationship between different parameters. RESULTS: The study population consisted of 73 female patients and 27 male patients, with a mean age of 58.32 ± 5.29 years and a mean follow-up duration of 25.88 ± 8.11 months. Preoperatively, the mean LAA was 75.81° ± 11.28°, RI was 4.78 ± 0.62, UCLA score was 17.54 ± 2.44, and qDASH score was 2.45 ± 0.25. The average tear size was 8.95 ± 2.11 mm. A statistically significant difference in LAA was observed between the preoperative and postoperative measurements, with the double-row repair group exhibiting a greater LAA than the single-row repair group. Finally, a significant correlation was identified between LAA, RI, and qDASH scores after a 24-month follow-up period. CONCLUSION: According to our findings, the utilization of double-row rivet fixation has a greater LAA angle than single-row rivet fixation. Moreover, this preservation of LAA is significantly associated with the functional recovery of the shoulder joint.