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The amount of fatty degeneration (FD) has major impact on the clinical result and cuff integrity after rotator cuff repair. A quantitative analysis with magnet resonance imaging (MRI) spectroscopy was employed to analyze possible correlation of FD with tendon retraction, tendon thickness and patients’ characteristics in full thickness supraspinatus tears. Forty-two patients with full-thickness supraspinatus tears underwent shoulder MRI including an experimental spectroscopic sequence allowing quantification of the fat fraction in the supraspinatus muscle belly. The amount of fatty degeneration was correlated with tendon retraction, tendon thickness, patients’ age, gender, smoker status, symptom duration and body mass index (BMI). Patients were divided in to three groups of retraction (A) 0-10 mm (n=), (B) 11-20 mm (n=) and (C)

Fatty Degeneration (FD) of the rotator cuff muscles influences functional and anatomical outcome after rotator cuff repair. The MRI based estimation of fatty degeneration is the gold standard. There is some evidence that Ultrasound elastography (EUS) can detect local differences of tissue stiffness in muscles and tendons. Shear-wave elastography (SWE) was evaluated to determine the extent to which shear wave velocity was associated with measures of fatty degeneration. MRI-spectroscopic fat measurement was used as a reference to quantify the amount of fat in the muscle belly. Forty-two patients underwent SWE of the supraspinatus muscles at its thickest diameter. After ultrasound evaluation an MRI-spectroscopic fat measurement of the supraspinatus muscle was performed using the SPLASH-technique. A gel filled capsule was used to locate the measured area in the MRI. The values of shear wave velocity (SWV) measured with SWE and spectroscopic fat measurement were correlated statistically using Pearson’s correlation test. Correlation of the fat amount measured with MRI-spectroscopy and the SWV measured with SWE was ρ =0.82. Spectroscopic measured fat ratio of the supraspinatus muscle ranged from 0% to 77.41% and SWV from 1.59 m/s to 5.32 m/s. In 4 patients no sufficient SWE could be performed, these individuals showed a larger diameter of the overlying soft tissue. SWV measured with SWE showed a good correlation with MRI spectroscopic fat amount of the supraspinatus muscle. These preliminary data suggest that SWE may be a sufficient tool in detecting and estimating the amount of fatty degeneration in the supraspinatus muscle in real time. Large overlying soft tissue may be a limitation in performing sufficient EUS. Ethical Committee Approval: Nr: 156/14 Date 12th August 2014. Level of Evidence: III.

Anatomic total shoulder arthroplasty is an accepted treatment for degenerative pathologies of the glenohumeral joint. However, when degenerative changes in the supraspinatus tendon are expected, it has been proposed to tilt downward the glenoid implant to avoid excessive upward humerus migration and eccentric loading of the glenoid. The advantage of glenoid tilting on joint stability has been measured on cadavers [Konrad, 2006] and bone substitutes [Oosterom, 2004], but its effect on glenoid stress is unknown. The goal of this study was evaluate the effect of a downward tilting of the glenoid when the supraspinatus muscle is deficient.

The Goutallier Classification is a semi quantitative classification system to determine the amount of fatty degeneration in rotator cuff muscles. Although initially proposed for axial computer tomography scans it is currently applied to magnet-resonance-imaging-scans. The role for its clinical use is controversial, as the reliability of the classification has been shown to be inconsistent. The purpose of this study was to compare the semi quantitative MRI-based Goutallier Classification applied by 5 different raters to experimental MR spectroscopic quantitative fat measurement in order to determine the correlation between this classification system and the true extent of fatty degeneration shown by spectroscopy. MRI-scans of 42 patients with rotator cuff tears were examined by 5 shoulder surgeons and were graduated according to the MRI-based Goutallier Classification proposed by Fuchs et al. Additionally the fat/water ratio was measured with MR spectroscopy using the experimental SPLASH technique. The semi quantitative grading according to the Goutallier Classification was statistically correlated with the quantitative measured fat/water ratio using Spearman’s rank correlation. Statistical analysis of the data revealed only fair correlation of the Goutallier Classification system and the quantitative fat/water ratio with R = 0.35 (p

The purpose of this study was to determine the torque produced by the supraspinatus muscle within the functional motion planes of forward flexion and elevation in the plane of the scapula. An isokinetic dynamometer was used to measure the reduction in torque produced by isolated paralysis of the suprascapular and axillary nerves in ten normal volunteers. A calculation of the potential torque of the supraspinatus and deltoid muscles was obtained from the product of the moment arm, cross-sectional area, and integrated electromyographic signal. The results of both the dynamometer measurement and the calculation of torque supported our conclusion that the supraspinatus and deltoid muscles are equally responsible for producing torque about the shoulder joint in the functional planes of motion.

Man's shoulder girdle is of the general pattern of his tree-swinging ancestors. With assumption of the upright posture, man's thorax has flattened from anterior-posterior. This results in a rotation of the scapula to a position of 45 degrees with the sagittal plane. In addition to this, man's forearm is habitually used in a position of approximately 45 degrees of internal rotation. This places the biceps tendon "off its trolley" and leads to biceps tinosynovitis. Motions of the glenohumeral joints result from the force couple of the deltoid muscle plus the rotator cuff muscles. The rotator cuff alone can abduct the arm with 50% force throughout the full range of its motion. In the absence of the supraspinatus muscle, however, the force couple is disrupted. Although initiation of abduction is with full force, the force rapidly falls off to 90 degrees. Above 90 degrees the arm can barely support its own weight. Although the shoulder undergoes progressive degenerative changes with age, the necessity for a joint implant, either partial or total--although successful--is rare.

By means of clinical examination, soft tissue radiography and quantitative electromyography, the effect of heavy industrial work was evaluated on welders at a shipyard. The study revealed that the older workers with shoulder pain have a chronic tendinitis of the rotator cuff. The supraspinatus muscle was shown to be consistently fatigued during overhead welding. It is believed that this is an important factor in the aetiology of the shoulder pain commonly occurring in older welders.

The problem of the increasingly common shoulder pain syndromes in industry was investigated by biomechanic and epidemiologic methods. Rotator cuff tendinitis constitutes a major problem in people with arduous occupations, i.e., shipyard welders (prevalence ratio, 18.3%), and steel plateworkers (16.2%). Static work seems to induce symptoms at an earlier age. The clinical diagnosis was supraspinatus tendinitis. The biomechanic studies confirmed the view that the shoulder muscles are heavily loaded when the arm is elevated. Excessive hand tool mass increases the strain markedly in some muscles, particularly the supraspinatus and the infraspinatus. The hypovascularity of the supraspinatus tendon is then likely to be accentuated by high intramuscular pressure that reduces the blood flow through the muscle. The strain on the supraspinatus muscle in overhead work is an important factor contributing to prolonged shoulder disability. An analysis of the distribution of loads imposed on the shoulder in practical working situations can be based on observations of working postures and external forces.

In an effort to elucidate the relationship of trauma, foci of infection and metabolic factors in the etiology of periarthritis of the shoulder and to determine the most efficacious treatment for this condition, we have analyzed a series of 200 cases that have come under our care during the last nine years. We realize that we may be treading on thin ice when we use the term "periarthritis of the shoulder," but it appears to us that this better describes the clinical entity than "painful shoulder," "subdeltoid bursitis," "subacromial bursitis" or "calcifications of the supraspinatus tendon," with which names all are familiar. Although Codman, 1 in his classic thesis of this subject, suggested the name "subacromial bursitis," he later demonstrated that when calcification occurred, the deposit was in the tendon of the supraspinatus muscle. This finding was confirmed by Brickner, 2 Carnett 3 and others. Calcification, however, does not explain

The admirable papers by Codman1published in theBoston Medical and Surgical Journalon subacromial bursitis have been responsible for a great increase both in interest and in knowledge of the common disabilities of the shoulder girdle. Codman differentiated calcification in the supraspinatus tendon from subacromial bursitis. A review of recent reports, however, indicates that this differentiation is but rarely made and thereby justifies an effort to distinguish further that particular clinical disability which is dependent on a degenerative disease of the supraspinatus tendon, accompanied by the deposition of lime salts but not necessarily with inflammation within the subacromial bursa. During the early period of more accurate observations on subdeltoid, or better subacromial, bursitis, calcification of the tendon was frequently mistaken for a bursitis, due to the failure to recognize that the area of calcification (fig. 1) rested beneath the inferior wall of the bursa but outside the true

A full discussion of the subject of subdeltoid bursitis is not possible here, and therefore only that phase in which the condition is associated with a deposit will be considered. A full study of both the acute and the chronic form may be obtained by reading the articles referred to in the footnotes. In 1906, Codman 1 gave a most complete discussion of the anatomy of the bursae about the shoulder. From this study it was clearly shown that the subacromial and the subdeltoid bursae were identical and the names synonymous. The bursa is composed of thin walls and contains but little fluid. There is no communication with the shoulder joint. Lying directly beneath and intimately connected with the bursa is the tendon of the supraspinatus muscle. It is also in close proximity to the subscapular and the infraspinatus tendons, thus playing a role in rotation of the humerus. On

Background Rotator cuff tendon tear is a leading cause for atrophy, fibrosis and fatty infiltration of the rotator cuff muscles. The pathophysiology of fatty muscle infiltration is not well understood. An animal model suited to study cellular and molecular mechanisms would therefore be desirable. While a rat model has been established for chronic rotator cuff tendon pathology, sufficient and easily identifiable fatty infiltration of the muscle has not yet been shown in rats. As younger animals regenerate better, we hypothesized that the absence of a sufficient amount of fatty infiltration in previous experiments was due to the selection of young animals and that older animals would exhibit higher amounts of fatty infiltration after tendon tear. Findings The supraspinatus tendon was released using tenotomy in 3 young (6 weeks old) and in 3 aged (24 months old) Sprague Dawley rats (group I and II). Another 3 aged (24 months old) rats underwent sham surgery and served as a control group (group III). In group I and II retraction of the musculotendinous unit was allowed for 6 weeks. All animals were sacrificed 6 weeks after surgery and the supraspinatus muscles were harvested. Each sample was examined for fatty infiltration of the muscle by histological methods and micro-CT. In histology, fat cells were counted with a 10-fold magnification in 6 fields of view twice. An adjusted measurement setup was developed for the use of micro-CT to quantify the absorption coefficient of the muscle as a reciprocal indicator for fatty infiltration, based on the established procedure for quantification of fatty infiltration on CT in humans. Tenotomy resulted in an insignificant increase of fat cells in histological sections in both, aged and young rats. Micro-CT was able to quantify small differences in the absorption coefficients of muscle samples; the absorption coefficient was 8.1% ± 11.3% lower in retracted muscles (group I and II) compared with the control (group III), indicating a tendency towards a higher amount of intra- and/or extracellular fat. Absorption was 4.28% ± 3.2% higher in aged compared with young muscles; however, this difference could not be confirmed by histology. Conclusions Substantial fatty muscle infiltration following chronic retraction after supraspinatus tenotomy could be documented histologically neither in young nor aged rats. Although micro-CT was able to reveal minor differences in absorption between the studied groups, the differences were too small to make the rat supraspinatus model interesting to study fatty infiltration of the chronically retracted muscle.