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Background Conventional fat quantification methods for rotator cuff muscles have various limitations, such as inconsistent reliabilities of the Goutallier grades and need for advanced techniques in quantitative MRI sequences. We aimed to examine a threshold-based fat quantification method in the supraspinatus muscle on standard T1-weighted MR images and compare the threshold-based method with Goutallier grades and MR spectroscopy. Methods We retrospectively examined 38 symptomatic patients, who underwent T1 and T2-weighted fast spin-echo MR imaging and a single voxel spin-echo MR spectroscopy. The supraspinatus muscle and fossa were manually segmented in T1-weighted sagittal images and clustering-based thresholding was applied to quantify the fat fractions in the segmented areas using custom MATLAB software. Threshold-based fat fractions were compared with the Goutallier grades and MR spectroscopy fat/water ratios. A one-way analysis of variance and Pearson correlation were tested in the MATLAB software. Results Inter-observer reliability of threshold-based fat fractions for the supraspinatus muscle and fossa were 0.977 and 0.990 respectively, whereas the reliability of the Goutallier grading was 0.798. Threshold-based fat fractions in the supraspinatus fossa were significantly different between various Goutallier grades (one-way ANOVA, p  < 0.001). Threshold-based fat fractions in the supraspinatus muscle strongly correlated with the MR spectroscopy fat/water ratio (Pearson correlation R-square = 0.83). Conclusions Threshold-based fat quantification on standard T1-weighted MR images was highly reliable and produced comparable results to conventional Goutallier grades and MR spectroscopy fat/water ratios and could serve as an alternative method for accurate fat quantification in rotator cuff muscles.

IntroductionArthroscopic superior capsule reconstruction (ASCR) using fascia lata autograft is a new surgical technique developed to overcome irreparable rotator cuff tears. There is little information about graft tear after ASCR and its impact on clinical outcome. This study is to investigate the graft tear rate, pattern of failure, and its correlation with clinical outcomes after arthroscopic superior capsule reconstruction (ASCR).Materials and methodsFrom June 2013 to June 2016, 31 shoulders in 31 consecutive patients (mean 65.3 years) underwent ASCR using fascia lata autograft for irreparable large-to-massive tears. Magnetic resonance imaging (MRI) was performed before surgery and at mean 12.8 months (12–24 months) after surgery to assess fatty infiltration progression and graft integrity. Graft tear was defined as the loss of graft continuity and was categorized as medial and lateral rows according to the failure location. Acromiohumeral distance (AHD) was pre- and postoperatively measured with the standard radiograph. Pain visual analog scale (VAS) score, American Shoulder and Elbow Surgeons (ASES) score, constant score, and physical examination were used to assess clinical outcomes. Average follow-up was 15 months (range 12–24 months) after surgery.ResultsMean active forward elevation increased from 133° to 146° (P = 0.011). Mean VAS score, ASES score, and constant score significantly improved: from 6 to 2.5, 54.4 to 73.7, and 51.7 to 63.7, respectively (P < 0.001). There was no remarkable progression of fatty infiltration after surgery. AHD increased from 5.3 mm preoperatively to 6.4 mm postoperatively (P < 0.016). Nine patients (29%) showed graft tear on follow-up MRI: 7 and 2 at the medial and lateral rows, respectively. Although the intact graft group showed better outcomes than the graft tear group (pain VAS score 2.3 vs. 3.0; ASES score 74.1 vs. 69.8; constant score 63.4 vs. 57.9), the results were not statistically significant.ConclusionsGraft tear rate after ASCR assessed by MRI was 29%, and failures mostly occurred at the medial row. The graft tear group showed clinical improvement despite the recurred superior capsule defect.Level of evidenceIV, case series, treatment study.

IntroductionThe subscapularis has received little attention in the orthopedic literature, although such lesions are evident in up to 40 % of arthroscopies. An accurate diagnosis is important in clinical practice, as it affects both patient prognosis and surgical planning. The aim of this study was to evaluate the accuracy of preoperative MRI for the identification of subscapularis tears. Our secondary aim involved the identification of factors that may be predictive for the presence of subscapularis tears.Materials and methodsThis retrospective case series included patients undergoing shoulder arthroscopy due to rotator cuff injury. MRI was performed using a 1.5 T unit, and the results were assessed by a musculoskeletal radiologist. The findings were compared to those of arthroscopic inspection.ResultsA total of 93 shoulders were analyzed. The overall accuracy was 82 %, with values of 79 % for partial tears and 89 % for full-thickness tears. Tears requiring repair demonstrated an accuracy of 88 %. Infraspinatus tears, fatty degeneration of the subscapularis, biceps instability and age were identified as predictive factors for the presence of injury.ConclusionsMRI of the shoulder demonstrated an accuracy of 82 % for the diagnosis of subscapularis tears. The accuracy values for partial and full-thickness tears were 79 and 89 %, respectively.Level de evidenceIII, development of diagnostic criteria with universally applied reference—nonconsecutive patients.

BackgroundQuantification of rotator cuff intramuscular fatty infiltration is important for clinical decision-making in patients with rotator cuff tear. The semi-quantitative Goutallier classification system is the most commonly used method, but has limited reliability. Therefore, we sought to test a freely available fuzzy C-means segmentation software program for reliability of the quantification of shoulder intramuscular fatty infiltration on T1-weighted MR images and for correlation with fat fraction by six-point Dixon MRI.Materials and methodsWe performed a prospective cross-sectional study to measure visible intramuscular fat area percentage on oblique sagittal T1 MR images by fuzzy C-means segmentation and fat fraction maps by six-point Dixon MRI for 42 shoulder muscles. Intra- and inter-observer reliability were determined. Correlative analysis for fuzzy C-means and six-point Dixon intramuscular fatty infiltration measures was also performed.ResultsWe found that inter-observer reliability for the quantification of visible intramuscular fat area percentage by fuzzy C-means segmentation and fat fraction by six-point Dixon MRI was 0.947 and 0.951 respectively. The intra-observer reliability for the quantification of visible intramuscular fat area percentage by fuzzy C-means segmentation and fat fraction by six-point Dixon MRI was 0.871 and 0.979 respectively. We found a strong correlation between fuzzy C-means segmentation and six-point Dixon techniques; r = 0.850, p < 0.001 by individual muscle; and r = 0.977, p < 0.002 by study subject.ConclusionQuantification of intramuscular fatty infiltration by fuzzy C-means segmentation on T1-weighted sequences demonstrates excellent reliability and strong correlation with fat fraction by six-point Dixon MRI. Quantitative fuzzy C-means segmentation is a viable alternative to the semi-quantitative Goutallier classification system.

IntroductionThe reliable diagnosis of partial-thickness tears of the rotator cuff is still elusive in clinical practise. Therefore, the purpose of the study was to determine the diagnostic accuracy of MR imaging and clinical tests for detecting partial-thickness tears of the rotator cuff as well as the combination of these parameters.Materials and methods334 consecutive shoulder arthroscopies for rotator cuff pathologies performed during the time period between 2010 and 2012 were analyzed retrospectively for the findings of common clinical signs for rotator cuff lesions and preoperative MR imaging. These were compared with the intraoperative arthroscopic findings as “gold standard”. The reports of the MR imaging were evaluated with regard to the integrity of the rotator cuff. The Ellman Classification was used to define partial-thickness tears of the rotator cuff in accordance with the arthroscopic findings. Descriptive statistics, sensitivity, specificity, positive and negative predictive value were calculated.ResultsMR imaging showed 80 partial-thickness and 70 full-thickness tears of the rotator cuff. The arthroscopic examination confirmed 64 partial-thickness tears of which 52 needed debridement or refixation of the rotator cuff. Sensitivity for MR imaging to identify partial-thickness tears was 51.6%, specificity 77.2%, positive predictive value 41.3% and negative predictive value 83.7%. For the Jobe-test, sensitivity was 64.1%, specificity 43.2%, positive predictive value 25.9% and negative predictive value 79.5%. Sensitivity for the Impingement-sign was 76.7%, specificity 46.6%, positive predictive value 30.8% and negative predictive value 86.5%. For the combination of MR imaging, Jobe-test and Impingement-sign sensitivity was 46.9%, specificity 85.4%, positive predictive value 50% and negative predictive value 83.8%.ConclusionsThe diagnostic accuracy of MR imaging and clinical tests (Jobe-test and Impingement-sign) alone is limited for detecting partial-thickness tears of the rotator cuff. Additionally, the combination of MR imaging and clinical tests does not improve diagnostic accuracy.Level of evidenceLevel II, Diagnostic study.