Study patients:
A retrospective study was performed to investigate whether the distance between the two tendons differed or not. A review of medical records and shoulder MRI scans of two different groups of patients was performed after receiving institutional review board approval (NO.2021–07). The two groups of patients were the anterior cable injury group, and anterior cable intact group.
The inclusion criteria of the anterior cable injury group patients were that they: (1) underwent a primary rotator repair at our institution between 2018 and 2020; (2) had clear MRI data of shoulder and documented tear pattern and size in the operative report; (3) had no previous history of shoulder surgery or trauma.
The exclusion criteria included were: (1) advanced glenohumeral joint arthritis; (2)large rotator cuff tear with the supraspinatus muscle retracted over the top of the humeral head; (3) extreme internal and external rotation of the humeral head on a shoulder MRI scan. All patient data were collected from the hospital medical record system.
Shoulder MRI scan: A 1.5-or 3.0- T Siemens MRI scanner (Siemens, Erlangen, Germany) was used for a shoulder examination. The patients, shoulder MRI scan included an axial turbo spin-echo (TSE) proton density-weighted image, TSE T1 and TSE T2- weighted images with fat suppression on a parallel or sagittal oblique plane to the supraspinatus tendon.
The standards of diagnosis of anterior cable disruption:
Firstly, operative records were reviewed if it was found that anterior supraspinatus was involved; then, the patient’s preoperative MRI scan was evaluated by an experienced senior orthopaedist and a radiologist. A 5mm anterior and posterior area to the intertubercular groove was considered to be the attachment area of the anterior cable [13]. Both the operative records and the MRI scan support would be marked as anterior cable disruption. When it was difficult to determine, the patient would be marked as intact anterior cable. If a disruption was seen on at least one of the parasagittal or coronal sequences, the MRI scan was marked as ‘anterior cable disruption’. The intraoperative records were used to evaluate at the same time, both showing that anterior cable disruption was divided into anterior cable injury group.
Measurement of humeral rotation and the central tendon of the supraspinatus:
All measurements were performed by four independent examiners. The four examiners included two fellowship-trained shoulder surgeons (Lifeng Yin and Jiaxin Chen ), one musculoskeletal radiologist (Xinyu Zhang) and one orthopaedic resident (Wenlong Yan). All measurements were operated on the PACS (picture archiving and communication system) of our hospital. (IDX Image cast, version 10.7; Koninklijke Philips Electronics, Amsterdam, Netherlands)
Humeral rotation and radius of the humeral head:
The rotation angle of the humeral head and the radius of the humeral head will be measured on a horizontal plane on the patients’ MRI scan by using the PACS tool. A proximal slice, showing an obvious outline of the bicipital groove, was chosen for measuring. Using the tool provided by the PACS system,a circle was drawn for measuring the radius, and for locating the central point of the humeral head, which was then used for measuring the rotation angle The angle between the line from the central point to the bicipital groove and the vertical line was defined as the rotation angle, and it was stipulated that the internal rotation was positive and the external rotation was negative.
Measurement of distance between the central tendon and the long head of the biceps tendon (DTD), posterior displacement distance of the central tendon on a horizontal plane (PTD):
DTD was used to reflect the distance between the supraspinatus tendon and the long head of the biceps tendon. The DTD was defined as the distance between the central points of the long head of the biceps tendon with the anterior edge of the supraspinatus tendon on the oblique sagittal shoulder MRI scan, where the distal coracoid process is about to disappear. First, the T2 fat suppression or the proton density fat suppression sagittal sequence of the MRI scan was reviewed to find the slice where the distal coracoid process nearly disappears (Fig1). Then a line connecting the central point of the LHBT and the anterior edge of the supraspinatus central tendon was made. The DTD was then measured by PACS automatically and the measuring of the distance was repeated twice. The average value was recorded. If the tendon was difficult to be located a more precise slice was selected.
The posterior displacement of the central supraspinatus tendon was defined as the shortest distance from the centre of the bicipital groove to the transferred central tendon line on the horizontal plane of the MRI, which measurement was based on Updegrove, G. F’s method [12]. (Fig. 2)
Tear Characteristic and muscle fatty degeneration:
Additional data regarding the tear size, the degree of the tear and fatty degeneration of the supraspinatus muscles were collected. The tear size was categorised into three degrees: level 1 (<1 cm), level 2 (1 cm–3 cm), level 3 (>3cm) and tear degrade was categorised into two types: partial tear and full thickness tear.
The degrees of supraspinatus muscle atrophy were determined by using Goutallier grading criteria to evaluate the atrophy of supraspinatus. Level 0: no fat infiltration; Level 1: a small amount of fat bands in muscles; Level 2: less fat than muscle; Level 3: fat equivalent to muscle; Level 4: more fat than muscle.
Sample size and Statistical methods
Owing to the fact that there was no previous research for this study to determine the variables, a preliminary experiment was carried out and after analysing with PASS software, it was shown that at least 50 samples were required.
Data analysis: SPSS 25.0 was used for most of the statistical analysis. Mean value and standard deviation were used to describe quantitative continuous data, while frequency and percentage were used to describe qualitative data. The humeral rotation, DTD and PTD from the biceps groove, was compared between groups using a two independent T test. Classification and rank variables were compared using the c² test. Binary logistical regression was also performed to assess the correlation between the DTD, posterior displacement distance, and other tear characteristics with anterior cable disruption. The receiver operating curve was also used for testing the predicting performance of the DTD, PTD, and other rotator cuff tear characteristics.
The data are presented as mean and standard deviation. Statistical significance was set at P<.05.