Neither critical shoulder angle nor acromion index were related with specific pathology 20 years later!

Purpose The critical shoulder angle (CSA) and the acromion index (AI) are measurements of acromial shape reported as predictors of degenerative rotator cuff tears (RCT) and glenohumeral osteoarthritis (GH OA). Whether they are the cause or effect of shoulder pathologies is uncertain since pre-morbid radiographs most often are lacking. The main aim of this study was to investigate if CSA or AI were related to the development of RCT or GH OA after 20 years. A secondary aim was to investigate if the CSA and AI had changed over time. Methods In the hospital archive, 273 preoperative plain shoulder radiographs were found of patients scheduled for elective surgery other than cuff repair and arthroplasty. Forty-five images fulfilled the strict criteria published by Suter and Henninger (2015) and were used to measure CSA and AI with two independent assessors. No patient had any sign of OA in the index radiographs or any information in the medical records indicating RCT. After a median of 20 (16–22) years, 30 of these patients were radiologically re-examined with bilateral true frontal views and ultrasound of the rotator cuff. There were 19 men (20 study shoulders) and 11 females (12 study shoulders). Results Mean age at follow-up was 56 (32–78) years. There was no correlation between CSA (r = 0.02) (n.s) or AI (r = − 0.13) (n.s) in the primary radiographs and OA at follow-up. Nor was any correlation found between index CSA (r = 0.12) (n.s) or AI (r = − 0.13) (n.s) and RCT at follow-up. Mean difference in CSA was − 1.7 (− 10–3) degrees and mean AI difference was − 0.04 (− 0.13–0.09) between the first and the second radiographs, 20 years later. Bilaterally, mean CSA was 32 and AI 0.61 at follow-up. Conclusion In this study, no correlation between the CSA, AI and development of OA or RCT could be found. The mean CSA and AI decreased over a 20-year period but the difference was very small. No difference was found between the study shoulders and the contralaterals. These findings question previously reported etiological associations between scapular anatomy and the development of OA or RCT and thereby the use of these calculations as the basis of treatment. Level of evidence III.

Correlation of Multiple Acromion Morphological Parameters on Radiographs in a Geriatric Chinese Population and Its Clinical Significance

Introduction Previous clinical studies have reported associations between the acromion index, lateral acromion angle, and critical shoulder angle and the occurrence of rotator cuff tears. The objective of this study was to analyze the correlations of these different anatomic parameters in geriatric Chinese Population. Methods Healthy geriatric Chinese participants (n = 66) and geriatric Chinese patients with rotator cuff tears (n = 70) identified between January 2019 and October 2020 were included in this study. Standardized true anteroposterior radiographs were used to measure the acromion index, lateral acromion angle, and critical shoulder angle in each study participant. Results The mean acromion index was significantly larger, the mean lateral acromion angle was significantly smaller, and the mean critical shoulder angle was significantly larger in geriatric patients with full-thickness rotator cuff tears compared with geriatric healthy participants. Conclusion There were a negative linear relationship between the acromion index and lateral acromion angle and a positive linear relationship between the acromion index and critical shoulder angle in geriatric patients with rotator cuff tear and geriatric healthy participants; we termed this phenomenon “Hypothesis of Acromion Index.” The acromion index, lateral acromion angle, and critical shoulder angle are independent predictors of rotator cuff tears in a geriatric Chinese population.

Feasibility of the acromion index as a reference of severity of stratified supraspinatus tendon injury: a secondary analysis

Background The acromion index (AI) is the acromial lateral extension above the head of the humerus. Some researchers have advocated that the AI indicates the severity of the tear size of the full-thickness supraspinatus tendon. Purpose To validate the reproducibility of the AI between shoulder magnetic resonance imaging (MRI) and standard X-ray and to verify whether the AI is a useful index for stratifying the severity of supraspinatus tendon injuries, as well as full-thickness tears. Material and Methods We enrolled 200 patients with impingement syndrome who were subsequently evaluated with standard X-ray of the shoulder in the anteroposterior view, as well as an MRI. We performed a pilot study to validate the reproducibility of the AI using standard X-ray and MRI, and to compare the AI between these imaging modalities. The severity of supraspinatus tendon injury was classified into four groups (0 = no evidence of injury, 1 = partial tear, 2 = full-thickness tear, and 3 = complete rupture) based on an official reading of the shoulder MRI. We compared the AIs of both modalities between the groups. Results Intraclass correlation coefficients of the AIs between the two examiners were 0.819 for MRI and 0.808 for plain X-ray. The mean AI from standard X-ray was greater than that from MRI ( P<0.0001). There was no statistical correlation between the AI and the severity of supraspinatus tendon injury. Conclusion Our findings indicate that the AI cannot be generally used as a predictive reference for the stratified severities of supraspinatus tendon injury.

Reporting on acromion morphology: classifications demonstrate significant correlation

ObjectivesVarious classifications of acromion morphology exist in the literature. Only a few studies have compared these classifications and their results vary substantially. The primary purpose of this study was to determine a correlation between different classifications of acromial morphology on a large cohort. The secondary purpose was to establish if there is a difference between age, sides and gender.MethodsA retrospective analysis of 1853 subjects’ shoulder CTs has been performed. A total of 350 CT scans of polytraumatised patients have been selected out of the initial cohort, after exclusion of fractures and technically insufficient scans. Acromial slope, type, lateral acromion angle (LAA) and acromion index were measured and gender, age and side differences were analysed. Correlations between the different classifications were analysed using the Pearson correlation coefficient.ResultsThe average patient age of this cohort was 48 (range 16–90). There were 232 men and 118 women. There was a significant correlation between all classifications. Excellent correlations have been shown for left-right comparison of all measurements. Gender showed no correlation to any of the measurements. Age was correlated to LAA and acromial type.ConclusionThere is a significant correlation between all investigated acromion classifications, demonstrated with the CT. This may aid the clinician in choosing a classification to use when reporting on a patient, depending on the pathology even when plain X-rays are obtained. Age is correlated to LAA and acromial type. There is a strong bilateral correlation within each patient. Gender is not correlated to the acromial shape in any classification.Level of evidenceLevel III diagnostic study.

Correlation of Multiple Acromion Morphological Parameters on Radiographs in a Chinese Population

Background Previous clinical studies have reported associations between the acromion index (AI), lateral acromion angle (LAA), and critical shoulder angle (CSA) and the occurrence of rotator cuff tears. The objective of this study was to analyze the correlations of these different anatomic parameters. Materials and Methods Healthy Chinese participants ( n = 66) and Chinese patients with rotator cuff tears ( n = 70) identified between January 2014 and October 2015 were included in this study. Standardized true anteroposterior radiographs were used to measure the AI, LAA, and CSA in each study participant. Results The mean AI was significantly larger (0.71 standard deviation [SD], 0.05; range 0.58–0.89 vs. 0.64 SD, 0.06; range 0.55–0.78; P < 0.001), the mean LAA was significantly smaller (77.0° SD, 5.73; range 61.0°–94.5° vs. 82.0° SD, 7.33; range 67.6°–98.3°; P < 0.001), and the mean CSA was significantly larger (36.1° SD, 5.29; range 21.3°–42.4° vs. 31.6° SD, 5.29; range 21.4°–45.8°; P < 0.001) in patients with full-thickness rotator cuff tears compared with healthy participants. Conclusions There were a negative linear relationship between the AI and LAA (rotator cuff tears: R = −0.759, P < 0.01; healthy participants: R = −0.813, P < 0.01) and a positive linear relationship between the AI and CSA (rotator cuff tears: R = 0.854, P < 0.01; healthy participants: R = 0.912, P < 0.01) in patients with rotator cuff tear and healthy participants; we termed this phenomenon “The Acromion Rule.” The AI, LAA, and CSA are independent predictors of rotator cuff tears in a Chinese population.

Radiographic shoulder parameters and their relationship to outcomes following rotator cuff repair: a systematic review

Background Anatomic parameters, such as the critical shoulder angle and acromion index, have emerged as methods to quantify scapular anatomy and may contribute to rotator cuff pathology. The purpose of this paper is to investigate the published literature on influences of scapular morphology on the development of re-tears and patient-reported outcomes following rotator cuff repair. Methods A systematic review of the Embase and PubMed databases was performed to identify published studies on the potential influence of scapular bony morphology and re-tear rates and patient-reported outcomes after rotator cuff repair. Studies were reviewed by two authors. Results A total of 615 unique titles and 49 potentially relevant abstracts were reviewed, with eight published manuscripts identified for inclusion. Two of three papers reported no relationship between these acromion index and rotator cuff re-tear rate, while one paper found an increased re-tear rate. All three studies on critical shoulder angle found a significant association between critical shoulder angle and cuff re-tear rate. There was no clear relationship between any bony morphologic measurement and patient-reported outcomes after rotator cuff repair. Conclusions Rotator cuff re-tear rate appears to be significantly associated with the critical shoulder angle and glenoid inclination, while not clearly associated with acromial morphologic measurements.