Evaluation of the prognostic value of the anatomical characteristics of the bony structures in the shoulder in bursal-sided partial-thickness rotator cuff tears.

Background: In recent studies, individual scapular anatomy has been found to be related to degenerative full-thickness rotator cuff tears. However, research on the relationship between the anatomical characteristics of shoulder radiographs and bursal-sided partial-thickness rotator cuff tears (PTRCTs) is limited, and the risk factors for this pathology still need to be determined. Methods: The bursal-sided PTRCTs group included 102 patients without a history of shoulder trauma who underwent arthroscopy between January 2021 and October 2022. A total of 102 demographically matched outpatients with intact rotator cuffs were selected as the control group. Radiographs were used to measure the lateral acromial angle (LAA), critical shoulder angle (CSA), greater tuberosity angle (GTA), ß-angle, acromion index (AI), acromiohumeral distance (AHD), acromial tilt (AT), acromial slope (AS), acromial type, and acromial spur by two independent observers. Multivariate analyses of these data were used to identify potential risk factors for bursal-sided PTRCTs. Receiver operating characteristic (ROC) analysis was performed to assess the sensitivity and specificity of CSA, GTA, and AI for this type of pathology. Result: The ß-angle, AHD, AS and acromion type showed no difference between bursal-sided PTRCTs and controls (p = 0.009, 0.200, 0.747 and 0.078, respectively). CSA, GTA and AI were significantly higher in bursal-sided PTRCTs (p < 0.001). LAA, ß-angle and AT were significantly lower in bursal-sided PTRCTs. Multivariate logistic regression analysis demonstrated significant correlations between the acromial spur (p = 0.024), GTA (p = 0.004), CSA (p = 0.003) and AI (p = 0.048) and bursal-sided PTRCTs. The areas under the ROC curves for AI, CSA, and GTA were 0.655 (95% CI 0.580-0.729), 0.714 (95% CI 0.644-0.784), and 0.695 (95% CI 0.622-0.767), respectively. Conclusion: Acromial spur, GTA, CSA, and AI were independent risk factors for bursal-sided PTRCTs. Furthermore, CSA was the most powerful predictor of bursal-sided PTRCTs compared to GTA and AI.

Deep learning model for measurement of shoulder critical angle and acromion index on shoulder radiographs.

Background: Several bone morphological parameters, including the anterior acromion morphology, the lateral acromial angle, the coracohumeral interval, the glenoid inclination, the acromion index (AI), and the shoulder critical angle (CSA), have been proposed to impact the development of rotator cuff tears and glenohumeral osteoarthritis. This study aimed to develop a deep learning tool to automate the measurement of CSA and AI on anteroposterior shoulder radiographs. Methods: We used MURA Dataset v1.1, which is a large publicly available musculoskeletal radiograph dataset from the Stanford University School of Medicine. All normal shoulder anteroposterior radiographs were extracted and annotated by an experienced orthopedic surgeon. The annotated images were divided into train (1004), validation (174), and test (93) sets. We use pytorch_segmentation_models for U-Net implementation and PyTorch framework for training the model. The test set was used for final evaluation of the model. Results: The mean absolute error for CSA and AI between human-performed and machine-performed measurements on the test set with 93 images was 1.68° (95% CI 1.406°-1.979°) and 0.03 (95% CI 0.02 - 0.03), respectively. Conclusions: A deep learning model can precisely and accurately measure CSA and AI in shoulder anteroposterior radiographs. A tool of this nature makes large-scale research projects feasible and holds promise as a clinical application if integrated with a radiology software program.

Are critical shoulder angle and acromion index correlated to the size of a rotator cuff tear.

PURPOSE: Scapular morphology is an extrinsic factor playing role in rotator cuff tear (RCT) etiology. The objective of this study was to evaluate the relationship between critical shoulder angle (CSA) and acromion index (AI) with partial-bursal side and full thickness RCT and the size of the RCT. HYPOTHESIS: The hypothesis was that CSA and AI would be greater in partial bursal-side RCT and full-thickness RCT patients and would increase with the size of the RCT. METHODS: This retrospective study assessed 218 patients who had standard shoulder radiographs and magnetic resonance imaging. Patients were divided into three groups: intact rotator cuff (68), partial bursal-side RCT (34) and full-thickness RCT (116). In the second part, full-thickness RCT patients were divided into four groups according to RCT size; small (<1cm), medium (1-3cm), large (3-5cm) and massive (>5cm). AI and CSA measurements were evaluated from radiographs. RESULTS: The mean CSA was 32.8̊ in control group, 34.3̊ in partial group and 36.9̊ in full-thickness group. The mean AI was 0.66, 0.68 and 0.72 respectively. Significant difference was found in AI and CSA between full thickness RCT and intact RC group (p<0.01), and partial RCT and full thickness RCT group (p<0.05) in paired comparisons. In full thickness RCT size groups the mean CSA was 34.2̊, 36.4̊, 39.0̊ and 40.8̊ and mean AI was 0.70, 0.71, 0.73 and 0.79 respectively. Significant difference was found between small-large, small-massive, medium-massive groups for CSA in paired comparisons and between small-massive, medium-massive groups for AI. CONCLUSION: CSA and AI were significantly greater in full-thickness RCT patients and the size of the RCT increased with CSA and AI. The greater CSA and AI could be predictors for larger RCT. LEVEL OF EVIDENCE: III; Cross-Sectional Design; Prognosis Study.

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.

The association between acromial anatomy and articular-sided partial thickness of rotator cuff tears.

BACKGROUND: Acromial anatomy has been found to be correlated with degenerative full-thickness rotator cuff tears in current studies. However, research on the relationship between acromial anatomy and articular-sided partial thickness of rotator cuff tears (PTRCTs) is still lacking. The purpose of this study was to evaluate whether these imaging graphic parameters exhibit any association between acromial anatomy and degenerative articular-sided PTRCTs. METHODS: Between January 2016 and December 2018, a total of 91 patients without a history of trauma underwent arthroscopy as an articular-sided PTRCT group. In the control group, with age- and sex-matched patients, we selected 91 consecutive outpatient patients who underwent shoulder magnetic resonance imaging (MRI) because of shoulder pain and an MRI diagnosis of only synovial hyperplasia and effusion. MRI was used to measure the acromial type, acromiohumeral distance (AHD), lateral acromial angle (LAA), acromion index (AI), and critical shoulder angle (CSA) by 2 independent observers. RESULTS: The acromion type, AHD and LAA showed no difference between degenerative articular-sided PTRCTs and controls (P = 0.532, 0.277, and 0.108, respectively). AI and CSA were significantly higher in degenerative articular-sided PTRCTs (P = 0.002 and 0.003, respectively). A good correlation was found between AI and CSA to measurement(Pearson correlation coefficient = 0.631). CONCLUSIONS: Our study revealed that higher AI and CSA were found in degenerative articular-sided PTRCTs. Acromial anatomy with a large acromial extension was associated with the occurrence of degenerative articular-sided PTRCTs.

WITHDRAWN: Higher coracoacromial ligament thickness, critical shoulder angle and acromion index are associated with rotator cuff tears in patients who undergo arthroscopic rotator cuff repair.

PURPOSE: To evaluate the effect of several shoulder anatomical parameters in the development of rotator cuff tear (RCT). METHODS: Between 2014 and 2018, all consecutive patients who underwent arthroscopic rotator cuff repair due to full-thickness rotator cuff tear with a minimum 2-year follow-up were identified. Inclusion criteria were (1) age>18 years, (2) patients with degenerative RCT, (3) full-thickness RCTs, (4) patients underwent arthroscopic RCR due to unresponsive conservative treatment, (5) minimum 2-year follow-up period. Exclusion criteria were traumatic RCT, history of previous shoulder surgery, shoulder deformity, neurologic or neuromuscular dysfunction, glenohumeral and/or acromioclavicular joint arthritis, cuff-tear arthropathy, history of fracture around shoulder and inadequate or low-quality magnetic resonance images (MRI). Acromion index (AI), Critical shoulder angle (CSA), Coracoacromial ligament (CAL) thickness, Subacromial space (SS) width, Acromiohumeral distance (AHD), CAL/SS ratio, Lateral acromial angle (LAA) and glenoid version angle (GVA) parameters were measured on MRI. Intra- and interobserver reliability were measured. Regression analysis was used to evaluate the association between anatomical parameters and RCT development. Receiver operating curves (ROC) were created for independent risk factors. The correlation between measurement parameters were evaluated. RESULTS: There were 1029 patients met the inclusion criteria. After exclusions, 437 patients were included. Age- and sex matched 437 patients without any shoulder pathologies were selected as control group. There was almost perfect intra- (ICC>0.85) and interobserver (ICC> 0.81) reliability regarding all measurement parameters. There was significant difference between RCT group and control group regarding AI (0.67±0.07 vs. 0.61±0.08, p<0.001), CSA (33.58±3.93 vs. 31.50±4.01, p<0.001), CAL thickness (1.81±0.64 vs. 1.53±0.50, p<0.001), CAL/SS ratio (0.29±0.14 vs. 0.23±0.10, p<0.001) and GVA (-16.69±6.69 vs. -15.37±5.95, p=0.002) parameters. AI (OR: 1.998, P<0.001), CAL thickness (OR: 2.801, p<0.000) and CSA (OR: 3.055, p<0.001) were found to be independently associated with the increased risk of RCT development. Area under curve (AUC) of the AI, CSA, and CAL thickness were 71.4%, 71.3%, and 70.2%, respectively. Cut-off values for AI, CSA, and CAL thickness were 0.62, 36.4° and 1.47 mm, respectively. There was significantly positive strong correlation between AI and CSA (p<0.001, r=0.814). CONCLUSION: Higher AI, CSA and CAL thickness independently associated with full-thickness RCT development. In clinical practice, these parameters may be useful in the prediction of rotator cuff rupture.

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.

The critical shoulder angle, the acromial index, the glenoid version angle and the acromial angulation are associated with rotator cuff tears.

PURPOSE: To compare the critical shoulder angle (CSA), acromion index (AI), acromion angulation (AA) and glenoid version angle (GVA) between patients with full-thickness rotator cuff tears (RCTs) and patients with intact rotator cuffs. METHODS: Between 2014 and 2018, the CSA, AI, AA and GVA were measured in consecutively included patients aged > 40 years who underwent shoulder arthroscopy for full-thickness RCTs. A total of 437 patients with RCTs and a mean age of 51.2 years (± 5.8) were included, 35.7% of whom were male. In the control group, there were n = 433 patients (36.3% male) with an intact rotator cuff, and the mean age was 50.7 years (± 5.3). RESULTS: The mean AI for the RCT group was 0.7 ± 0.1, which was significantly higher than the mean AI for the control group (0.6 ± 0.1, p < 0.001). The mean CSA for the RCT group was 33.6° ± 3.9°, which was significantly higher than the mean CSA for the control group (31.5° ± 4°, p < 0.001). The mean AA for the RCT group was 13.9° ± 9°, which was significantly higher than the mean AA for the control group (12.4 ± 8.6, p = 0.012). The mean GVA for the RCT group was - 3.5° ± 4.6° and significantly retroverted compared with the mean GVA for the control group (- 2.2° ± 4.6°, p < 0.001). The cutoff values determined by the ROC curve analyses were as follows: 0.6 for AI, 31.4° for CSA, 9.6° for AA and - 2.6° for GVA. CONCLUSION: The CSA, AI, GVA and AA values measured by MRI were determined to be significantly related to full-thickness rotator cuff ruptures. The AI, CSA, AA and GVA may be considered risk factors for degenerative rotator cuff tears. Assessing the CSA, AI, GVA and AA can be helpful for diagnostic evaluation of patients with full-thickness RCTs. LEVEL OF EVIDENCE: III.

Long-term follow-up of patients with a high critical shoulder angle and acromion index: is there an increased retear risk after arthroscopic supraspinatus tendon repair?

BACKGROUND: The effect of the acromion index (AI) and critical shoulder angle (CSA) on the short-term healing rate after arthroscopic repair of the supraspinatus tendons is already known. Long-term effects have not been published yet. PURPOSE: Long-term evaluation of the effect of the AI and CSA on the postoperative healing rate and clinical results after arthroscopic repair of the supraspinatus tendon. METHODS: Patients with a symptomatic, single-tendon, full-thickness supraspinatus tear in whom nonoperative management had failed were treated with an arthroscopic repair. Preoperative radiographs were used to measure CSA and AI. Eight years postoperatively, magnetic resonance imaging (MRI) studies were performed and evaluated on repair integrity. Patient-reported outcome measurements were collected pre- and postoperatively. RESULTS: Thirty-one patients were evaluated 8 years postoperatively. The mean age at the time of surgery was 61 ± 9 years. MRI evaluation showed that 20 patients (65%) had an intact repair and 11 (35%) had a full-thickness retear. No significant differences were found between the intact and retear groups regarding age (P = .605), initial tear size (P = .485), retraction grade (P = .439), and all PROMs. The mean CSA for the intact group (33° ± 1°) was significantly lower than the CSA in the retear group (38° ± 1°; P = .004). Eighteen patients (58%) had a CSA ≥35°, and 9 (50%) among them had a retear and 9 (50%) had an intact repair.The mean AI for the intact group (0.72 ± 0.11) was significantly lower than the AI in the retear group (0.81 ± 0.08 ; P = .021). Seventeen patients (55%) had an AI ≥0.75, and 9 (53%) among them had a retear and 8 had an intact repair. If the AI was ≥0.75, the odds ratio of having a retear was 6.19 (P = .045). No progressive worsening of PROMs and clinical results could be demonstrated related to a higher CSA or AI during the entire follow-up. CONCLUSION: At long-term follow-up, a higher CSA has the tendency to have an increased rate of retear after arthroscopic supraspinatus tendon repair, but this was not significant. A higher AI significantly increased the retear risk. A higher CSA and AI did not impair the clinical results over time. An AI ≥0.75 was associated with a 6-fold increase in risk of retear after arthroscopic supraspinatus tendon repair.

Effect of different geometrical structure of scapula on functional recovery after shoulder arthroscopy operation.

BACKGROUND: There are no published studies of the influence of geometry of the scapula on the postoperative recovery of rotator cuff injuries. Our aim was to explore the relationship between the critical shoulder angle (CSA), acromion index (AI), glenoid inclination (GI), and postoperative repair outcomes in shoulder joints after arthroscopic supraspinatus tendon repair. METHODS: Sixty two patients suffering a supraspinatus tear were analyzed retrospectively following failure of conservative treatment and subsequent shoulder arthroscopy in our hospital. Standard anterior and posterior X-rays of the injured shoulder had been performed prior to surgery, with follow ups for at least 2 years (24-43 months). Magnetic resonance imaging (MRI) was performed 2 years after surgery to assess repair of the supraspinatus tendon. Patients were divided into either the intact or re-tear group, according to the MRI results. In addition, assessments using the Constant Shoulder Score (CSS), the American Shoulder and Elbow Surgeon (ASES) Shoulder Assessment Form, the University of California at Los Angeles (UCLA) score and visual analog scale (VAS) score were performed to establish shoulder function at the 2-year evaluation for each patient. RESULTS: The mean CSA of all patients was 35.79° ± 3.59°, mean AI was 0.72 ± 0.05, and mean GI was 15.87° ± 3.62°. The CSA, AI, and GI in the intact group were statistically significantly different than the re-tear group (p < 0.05). There was no correlation between the magnitude of the CSA, AI, or GI and any shoulder function score (p > 0.05). CONCLUSIONS: The geometry of the scapula had no significant effect on the recovery of postoperative function of patients with rotator cuff injury, but the value of the CSA, AI, and GI affected the risk of rotator cuff re-tear.

The association between a low critical shoulder angle and SLAP lesions.

PURPOSE: To evaluate the critical shoulder angle (CSA), acromion index (AI) and further acromion parameters in patients with isolated SLAP lesions compared with patients without SLAP lesions. METHODS: Between 2012 and 2016, the CSA, AI, lateral acromion angle (LAA) and acromion slope (AS) were radiologically examined in consecutive patients > 18 years having had a shoulder arthroscopy with isolated SLAP lesion types II-IV. These were compared to controls without SLAP lesions and without (control group I) or with (control group II) complete supraspinatus tendon (SSP) tears. RESULTS: 75/103 patients with isolated SLAP lesion types II-IV with a mean age of 46.5 years (± 13.0, 18.1-76.3) were analyzed, 61% of them being male. For control, n = 211 consecutive patients (47% male) with an intact SSP and SLAP complex and a mean age of 52.3 years (± 15.0, 18.6-88.4) and n = 115 patients (60% male) with an intact SLAP complex but complete SSP tears, mean age 66.6 years (± 9.3, 44.7-87.9) were examined. The CSA in SLAP patients was 29.6° (± 3.5, 21.0-38.0), 33.8° (± 3.7, 25.1-46.9) in no SLAP and no SSP (p < 0.001) and 36.7° (± 3.6, 29.1-46.6) in no SLAP but SSP (p < 0.001). The area under the curve (AUC) for CSA was 0.83 for SLAP lesions resulting in a probability of 83% for patients with SLAP lesion to be associated with a specific CSA. CONCLUSIONS: Isolated SLAP lesion types II-IV are associated with a low CSA < 30°. The AI, the AS as well as the LAA showed no correlation with SLAP lesions. LEVEL OF EVIDENCE: Retrospective comparative study, Level III.

Association between the Critical Shoulder Angle and Rotator Cuff Tears in Japan.

Distinct anatomic variants of the scapula such as the critical shoulder angle (CSA) were found to be associated with rotator cuff tears (RCTs), but it is unclear whether the CSA is a risk factor in Japanese. Here we sought to determine whether the CSA is associated with RCTs in a Japanese population, and whether the CSA is a more useful parameter than the conventionally used parameters. Our RCT group and non-RCT group each consisted of 54 consecutive cases. We compared the groups' values of CSA, the acromion index (AI), and the lateral acromion angle (LAA) obtained by X-ray imaging. Receiver operating characteristic (ROC) analyses were performed to determine cutoff values and the area under the curve (AUC), and to assess the odds ratio. The means of the CSA and the AI in the RCT group were significantly larger (36.3° vs. 33.7°, 0.74 vs 0.68), but the LAA did not show a significant between-group difference. The AUCs for the CSA and AI were 0.678 and 0.658, the cutoff values were 35.0° and 0.72, and the odds ratios were 3.1 and 2.5, respectively. In conclusion, the CSA was a strong risk factor compared to the AI and LAA for rotator cuff tears.

Predictors of shoulder degeneration in the Kwazulu-Natal population of South Africa / Indicadores de la degeneración del hombro en la poblacion Kwazulu/Natal de Sudáfrica

SUMMARY: The critical shoulder angle and acromion index are conventional radiological tools employed as predictors of shoulder degeneration. As they represent the static components of glenohumeral stability, the scapulo-humeral geometry and underlying subacromial tissue appear as the resultant cause-effect factors. Consequently, the purpose of this study was to investigate the critical shoulder angle and acromion index as interrelated parameters within the South African population. The measurement of both biomechanical parameters was conducted on two-hundred and sixty (n = 260) true AP radiographs. This was a cross-sectional study that also incorporated the demographic representation of the population group which was analysed accordingly. The mean values recorded for both the critical shoulder angle (36.31±5.84º) and acromion index (0.74±0.13) suggested rotator cuff arthropathy. The results confirmed the theories of Nyffeler et al. (2006) and Moor et al. (2012) who alluded to glenoid inclination and the acromial coverage over the humeral head. A significant proportionality correlation, verified by a P value of 0.000, was established between the acromion index and critical shoulder angle which may assist to differentiate between normal asymptomatic shoulders and those with cuff disease. Furthermore, these predictors of shoulder degeneration may present as a preventative tool against tear progression.

RESUMEN: El ángulo crítico del hombro y el índice acromial son herramientas radiológicas convencionales empleadas como indicadores de la degeneración del hombro. Debido a que representan los componentes estáticos de la estabilidad glenohumeral, la geometría escápulo-humeral y el tejido subacromial subyacente aparecen como los factores causa-efecto resultantes. En consecuencia, el propósito de este estudio fue investigar el ángulo crítico del hombro y el índice acromial como parámetros interrelacionados dentro de la población sudafricana. La medición de ambos parámetros biomecánicos se realizó en 260 radiografías antero-posteriores (AP). Se realizó un estudio transversal que también incorporó la representación demográfica del grupo de la población que fue analizada. Los valores medios registrados tanto para el ángulo crítico del hombro (36,31 ± 5,84º) como para el índice del acromión (0,74 ± 0,13) sugirieron una artropatía del manguito rotador. Los resultados confirmaron las teorías de Nyffeler et al. (2006) y Moor et al. (2012) que aludían a la inclinación glenoide y a la cobertura acromial sobre la cabeza humeral. Se estableció una correlación de proporcionalidad significativa, verificada por un valor de P de 0,000, entre el índice acromial y el ángulo crítico del hombro, lo que puede ayudar a diferenciar entre los hombros asintomáticos normales y aquellos con enfermedad del manguito rotador. Además, estos predictores de degeneración del hombro pueden ser útiles como una herramienta preventiva contra la progresión del desgarro.

Correlation between anatomy of the scapula and the incidence of rotator cuff tear and glenohumeral osteoarthritis via radiological study.

INTRODUCTION: We conducted a study to elucidate the correlation between the anatomy of the shoulder joint with the development of rotator cuff tear (RCT) and glenohumeral osteoarthritis (GHOA) by using acromioglenoid angle (AGA). MATERIALS AND METHODS: The AGA is a new measured angle formed between the line from midglenoid to lateral end of the acromion with the line parallel to the glenoid surface. The AGA was measured in a group of 85 shoulders with RCT, 49 with GHOA and 103 non-RCT/GHOA control shoulders. The AGA was compared with other radiological parameters, such as, the critical shoulder angle (CSA), the acromion index (AI) and the acromiohumeral interval (AHI). Correlational and regression analysis were performed using SPSS 20. RESULTS: The mean AGA was 50.9° (45.2-56.5°) in the control group, 53.3° (47.6-59.1°) in RCT group and 45.5° (37.7-53.2°) in OA group. Among patients with AGA > 51.5°, 61% were in the RCT group and among patients with AGA < 44.5°, 56% were in OA group. Pearson correlation analysis had shown significant correlation between AGA and CSA ( r = 0.925, p < 0.001). It was also significant of AHI in RCT group with mean 6.6 mm (4.7-8.5 mm) and significant AI in OA group with mean 0.68 (0.57-0.78) with p value < 0.001 respectively. CONCLUSION: The AGA method of measurement is an excellent predictive parameter for diagnosing RCT and GHOA.

Higher critical shoulder angle increases the risk of retear after rotator cuff repair.

BACKGROUND: No evaluation has been done on the relationship of the critical shoulder angle (CSA) with retear after rotator cuff repair. Our purpose was to evaluate whether a higher CSA is associated with retear after rotator cuff repair. METHODS: This was a retrospective review of 76 patients who had undergone rotator cuff repair with postoperative ultrasound examination. Ultrasound findings were graded no retear (NT), partial-thickness (PT) retear, or full-thickness (FT) retear. Preoperative radiographs were used to measure CSA, glenoid inclination, lateral acromion angle, and acromion index. RESULTS: Average age was 61.9 years (45.3-74.9 years). On ultrasound examination, 57 shoulders (74.0%) had NT, 11 (14.2%) had PT retears, and 8 (10.3%) had FT retears. There was no significant difference in retear rate by age, gender, or tension of repair. Average CSA was significantly lower for the NT group at 34.3° ± 2.9° than for the FT group at 38.6° ± 3.5° (P < .01). If CSA was >38°, the odds ratio of having an FT retear was 14.8 (P < .01). In addition, higher CSA inversely correlated with postoperative American Shoulder and Elbow Surgeons scores (P < .03). Average glenoid inclination was significantly lower in the NT group at 12.3° ± 2.7° compared with 17.3° ± 2.6° in the FT group (P < .01). If glenoid inclination was >14, the odds ratio of having a FT retear was 15.0 (P < .01). CONCLUSION: At short-term follow-up, higher CSA significantly increased the risk of an FT retear after rotator cuff repair. Also, increasing CSA correlated with worse postoperative American Shoulder and Elbow Surgeons scores. This radiographic marker may help manage expectations for rotator cuff tear patients.

Effects of glenoid inclination and acromion index on humeral head translation and glenoid articular cartilage strain.

BACKGROUND: Previous clinical studies have reported associations between glenoid inclination (GI), the acromion index (AI), and the critical shoulder angle (CSA) on the one hand and the occurrence of glenohumeral osteoarthritis and supraspinatus tendon tears on the other hand. The objective of this work was to analyze the correlations and relative importance of these different anatomic parameters. METHODS: Using a musculoskeletal shoulder model developed from magnetic resonance imaging scans of 1 healthy volunteer, we varied independently GI from 0° to 15° and AI from 0.5 to 0.8. The corresponding CSA varied from 20.9° to 44.1°. We then evaluated humeral head translation and critical strain volume in the glenoid articular cartilage at 60° of abduction in the scapular plane. These values were correlated with GI, AI, and CSA. RESULTS: Humeral head translation was positively correlated with GI (R = 0.828, P < .0001), AI (R = 0.539, P < .0001), and CSA (R = 0.964, P < .0001). Glenoid articular cartilage strain was also positively correlated with GI (R = 0.489, P = .0004) but negatively with AI (R = -0.860, P < .0001) and CSA (R = -0.285, P < .0473). CONCLUSIONS: The biomechanical shoulder model is consistent with clinical observations. The prediction strength of CSA is confirmed for humeral head translation and thus presumably for rotator cuff tendon tears, whereas the AI seems more appropriate to evaluate the risk of glenohumeral osteoarthritis caused by excessive articular cartilage strain. As a next step, we should corroborate these theoretical findings with clinical data.

Arthroscopic lateral acromion resection (ALAR) optimizes rotator cuff tear relevant scapula parameters.

BACKGROUND: The acromion index (AI), critical shoulder angle (CSA) and lateral acromion angle (LAA) are predictive for degenerative rotatory cuff tears. Their unfavorable values are associated with a suboptimal deltoid force vector. The aim of this study was to evaluate whether an optimization of the radiological parameters could be achieved through a specific arthroscopic lateral acromion resection (ALAR). MATERIALS AND METHODS: The procedure was performed in eight fresh frozen cadaver shoulders. True a.p. and axial radiographs were taken before and after the intervention for radiological evaluation. The anterior and posterior acromion edges were marked with a spinal needle. Then 1 cm of the lateral acromion was resected with a 5.0 acromionizer (Arthrex Inc., Naples, FL, USA) beginning from the anterior aspect. The resection was completed over the total width of 1 cm from anterior to posterior. Finally the deltoid insertion was dissected via an open approach to ensure its integrity. The fluoroscopy images were evaluated regarding the pre- and postinterventional parameters AI, CSA and LAA. RESULTS: After the intervention, the mean AI could be significantly reduced from 0.62 ± 0.11 to 0.40 ± 0.15 (p = 0.012). Also the mean CSA was significantly reduced from 35.0° ± 7.65° to 25.12° ± 8.29° (p = 0.018). The LAA could not be significantly changed (76.5° ± 14.02° vs. 82.13 ± 8.93; p = 0.107). There was no injury to the deltoid insertion. CONCLUSION: The radiographic parameters AI und CSA can be optimized significantly by ALAR without macroscopic discontinuity of the deltoid insertion. LEVEL OF EVIDENCE: Level IV, case series without comparison group.

Does scapular morphology affect the integrity of the rotator cuff?

BACKGROUND: Current evidence suggests that distinct scapular morphologies may predispose patients to a rotator cuff tear. The objective of this longitudinal study was to evaluate the relationship between symptomatic degenerative cuff tears and different radiographic acromial characteristics, including acromion shape, indices (acromial index [AI], critical shoulder angle [CSA]), and acromial spur. METHODS: We divided 166 patients into 3 groups matched for age and sex: group 1, degenerative full-thickness tear; group 2, partial thickness bursal tear; and group 3, normal cuff. Patients were evaluated with standard radiographs and ultrasonography. RESULTS: The presence of an acromial spur was strongly associated with a full-thickness cuff tear (odds ratio, 3.5; P = .001). AI and CSA revealed a statistically significant difference between means of group 1 (P = .006) and group 3 (P < .001). There was no statistically significant difference in means of AI between groups 1 and 2 (P = .695) and between groups 2 and 3, with respect to AI (P = .071) and CSA (P = .125). Receiver operating characteristic curve revealed a higher area for CSA (0.70) than for AI (0.61). Stepwise logistic regression rejected AI as a cuff tear predictor but confirmed CSA and a spur to be stronger predictors of a full-thickness cuff tear. There was no association between the Bigliani acromial type and rotator cuff tear (P = .06). CONCLUSIONS: The presence of an acromion spur is strongly associated with full-thickness cuff tear. Higher AI and CSA are associated with a full-thickness tear but not with partial tears. The type of acromion is not related to cuff tear.

Relationship of individual scapular anatomy and degenerative rotator cuff tears.

BACKGROUND: The etiology of rotator cuff disease is age related, as documented by prevalence data. Despite conflicting results, growing evidence suggests that distinct scapular morphologies may accelerate the underlying degenerative process. The purpose of the present study was to evaluate the predictive power of 5 commonly used radiologic parameters of scapular morphology to discriminate between patients with intact rotator cuff tendons and those with torn rotator cuff tendons. METHODS: A pre hoc power analysis was performed to determine the sample size. Two independent readers measured the acromion index, lateral acromion angle, and critical shoulder angle on standardized anteroposterior radiographs. In addition, the acromial morphology according to Bigliani and the acromial slope were determined on true outlet views. Measurements were performed in 51 consecutive patients with documented degenerative rotator cuff tears and in an age- and sex-matched control group of 51 patients with intact rotator cuff tendons. Receiver operating characteristic analyses were performed to determine cutoff values and to assess the sensitivity and specificity of each parameter. RESULTS: Patients with degenerative rotator cuff tears demonstrated significantly higher acromion indices, smaller lateral acromion angles, and larger critical shoulder angles than patients with intact rotator cuffs. However, no difference was found between the acromial morphology according to Bigliani and the acromial slope. With an area under the receiver operating characteristic curve of 0.855 and an odds ratio of 10.8, the critical shoulder angle represented the strongest predictor for the presence of a rotator cuff tear. CONCLUSION: The acromion index, lateral acromion angle, and critical shoulder angle accurately predict the presence of degenerative rotator cuff tears.

An anthropometry study of the shoulder region in a chinese population and its correlation with shoulder disease / Estudio antropométrico de la región del hombro en una población china y su relación con enfermedad del hombro

Purpose: There is a paucity of data which reflected the relationship between morphology and incidence of shoulder disorders with respect to the ethnic Chinese population. We used anteroposterior radiographs to measure the Acromion Index (AI) and Acromioglenoid Angle (AA) of Chinese patients. The baseline was defined as the line that connected the superior and inferior osseous margins of the glenoid cavity. In order to calculate the AI, the distance from the baseline to the lateral margin of the acromion was measured and then divided by the distance from the baseline to the lateral aspect of the humeral head. The AA was defined as the angle formed by the intersecting line drawn tangent to the sclerotic line of the acromion undersurface and the baseline point. The AI and AA were determined in three groups: 165 patients (average age, 60.2 years) with chronic shoulder symptoms; in an age and gender-matched acute injury group of 61 patients (average age, 44.3 years); and in an age and gender-matched control group of 63 volunteers (average age, 37.3 years).The average AI and standard deviation was 0.72 +/- 0.06 in shoulders with subacromial impingement syndrome, 0.59 +/- 0.06 in those with acute injury, and 0.66 ± 0.06 in normal shoulders. The average AA and standard deviation was 76.8°+/-7.02 in shoulders with subacromial impingement syndrome, 84.2°+/-7.81 in those with acute injury, and 80.0°+/- 7.33 in normal shoulders. The AI and AA varied between patients with acute and chronic shoulder problems.

Hay escasez de datos que reflejen la relación entre la morfología y la incidencia de los trastornos de hombro con respecto a la población de origen chino. Se utilizó radiografías anteroposteriores para medir el índice acromial (IA) y ángulo acromioglenoido (AA) de los pacientes chinos. La línea de base se define como la que conecta los márgenes óseos superior e inferior de la cavidad glenoidea. Con el fin de calcular el IA, se midió la distancia desde la línea base hasta el margen lateral del acromion y luego se dividió por la distancia desde la línea base hasta la cara lateral de la cabeza humeral. El AA se define como el ángulo formado por la línea de intersección dibujada tangente a la línea esclerótica de la superficie inferior del acromion y el punto de línea base. El AI y AA se determinaron en tres grupos: 165 pacientes (edad media, 60,2 años) con síntomas crónicos en el hombro; en un grupo de 61 pacientes (edad media, 44,3 años) con herida aguda, y en un grupo control de 63 voluntarios (edad media, 37,3 años). La IA promedio fue de 0,72 +/- 0,06 en los hombros con el síndrome de pinzamiento subacromial, 0,59 +/- 0,06 en los pacientes con lesión aguda, y 0,66 +/- 0,06 en los hombros normales. El AA promedio fue de 76,8 ° +/- 7,02 en los hombros con el síndrome de pinzamiento subacromial, 84,2 ° +/- 7,81 en los pacientes con lesión aguda, y 80,0 ° +/- 7,33 en los hombros normales. La IA y AA variaron entre los pacientes con problemas en el hombro agudos y crónicos.