Role of Ultrasound in Evaluation of Shoulder Injuries: A Comparative Study of Ultrasound and MRI
Abhinav Pratap Singh, Anuradha Rao, Siddalinga Devaru, Amithavikrama
1. Resident, Department of Radiology, Apollo Hospitals, Bangalore, Karnataka, India. 2. Associate Consultant, Department of Radiology, Apollo Hospitals, Bangalore, Karnataka, India. 3. Senior Consultant, Department of Radiology, Apollo Hospitals, Bangalore, Karnataka, India. 4. Consultant, Department of Radiology, Apollo Hospitals, Bangalore, India.
Correspondence Address :
Dr. Anuradha Rao,
317, 11 A Cross, J.P. Nagar, 2nd Phase, Bangalore
560078, Karnataka, India.
: The rotator cuff disorders constitute the most common cause of painful shoulder. Ultrasonography and MRI are widely used in evaluating various shoulder pathologies. USG of shoulder is simple, cheap, fast and non-invasive imaging technology for detection of rotator cuff and non- rotator cuff abnormalities. In this study we have assessed the usefulness of USG in diagnosing the shoulder pathologies and have compared with the MRI.
Aim: Evaluation of a patient with painful shoulder with ultrasonography as the initial line of imaging technique as compared to MRI, assessing the accuracy of ultrasonography in diagnosing shoulder joint pathologies, especially rotator cuff abnormalities, using MRI as a reference standard and correlating findings wherever possible, and to delineate pitfalls during image interpretation and limitations of USG.
Materials and Methods: Sixty patients were studied prospectively over a period of two years. Study subjects included both men and women in all age groups with shoulder pain, suspected to have musculo-tendinous origin. All patients underwent USG evaluation of the shoulder joint followed by MRI of the affected shoulder.
Results: USG showed an accuracy of 70%, 95% and 98% in detection of any tear of supraspinatus, subscapularis and infraspinatus tendon respectively using MRI as reference. USG showed a sensitivity of 88.89%, specificity of 100%, PPV of 100% and NPV of 98.07% in diagnosing full thickness tear of rotator cuff using MRI as reference. For partial thickness tears, it showed a sensitivity of 78.04%, specificity of 89.47%, PPV of 94.11% and NPV of 65.38%. Overall accuracy of USG in detection of any tear of rotator cuff with MRI as reference was 82%. The strength of agreement between USG and MRI for the diagnosis of any tear of rotator cuff is considered to be ‘substantial’ in our study (Kappa=0.635).
Conclusion: USG showed comparable results to MRI in assessment of rotator cuff abnormality and should be used as first line of investigation in patients presenting with shoulder pain. It proved to have high sensitivity and specificity for full thickness tears with relatively less sensitivity and specificity in detection of partial thickness tear.
|Keywords : Complete tears, Joint effusion, Partial tears, Rotator cuff, Tendinosis|
Shoulder pain is third most common presenting complaints due to which a person visits Orthopedic clinic (1). Tendon inflammation, tendon tear, joint instability, arthritis, fracture are common causes of shoulder pain. Other less common causes include infections and nerve related conditions. The rotator cuff disorders constitute the most common cause of painful shoulder (2). Continuous active and passive forces make the rotator cuff tendons prone to degeneration causing swelling of tendon with sub-luxation (3). Ultrasonography and MRI are widely used in evaluating various shoulder pathologies.
Shoulder joint is the commonest joint to undergo musculoskeletal (MSK) USG examination (4). USG of shoulder is simple, cheap, fast and non-invasive imaging technology for the detection of rotator cuff and non- rotator cuff abnormalities (5),(6).
Dynamic examination of shoulder can be carried out in multiple planes and areas of concern can be focused promptly to make a diagnosis. However, it has its own limitations such as high operator dependency, limited utility in evaluation of labral lesions, rotator cuff interval, in demonstrating subtle bony lesions and inter-observer variations.
Magnetic resonance imaging (MRI) has extensive contrast resolution which allows extensive non-invasive evaluation of the soft tissues. Details of the rotator cuff pathology, including the size of the tear, extent of retraction, and amount of muscle atrophy are provided by the MRI aid surgical planning (7). Identifying ganglion cysts, labral injuries, and biceps tendon lesions are other advantages of MRI.
Arthrography though considered accurate for detection of complete tears, is an invasive procedure and is associated with patient discomfort. It is insensitive to intra substance and superficial partial tears of rotator cuff (8).
MRI is a sensitive modality but is expensive and time consuming. It cannot be used for patients having claustrophobia. The accuracy of ultrasound depends on the sonologist, his experience with musculoskeletal imaging and also on the equipment available (4). Ultrasonography has advantages of being comparatively a faster technique with low cost and wide availabilty. High resolution USG has emerged as widely used diagnostic tool for musculoskeletal pathologies in the last few decades with rise in its use in sports medicine (9). Rheumatologists, Orthopaedicians and Physicians dealing with sports medicine use ultrasound in evaluation of shoulder injuries. Hence, with wide availability and increasing use it is also needed to determine the diagnostic accuracy of the USG.
|MATERIAL AND METHODS|
A prospective study was undertaken in Department of Radiology in our Apollo Hopsitals, Bangalore, India, on 60 patients referred for MRI shoulder joint for a period of two years from November 2013 to December 2015. Symptomatic patients with painful shoulder, who were referred for shoulder MRI were considered for the study. After clinical evaluation, once a patient satisfied the inclusion and exclusion criteria for this study, he or she underwent sonographic evaluation of the shoulder joint followed by MRI of the affected shoulder. Ethical committee approval was obtained. Patient consent was taken.
Inclusion Criteria • History of pain in either of the shoulder. • History of restricted movements in either shoulder. • Clinically suspected to have internal derangements like rotator cuff injury, biceps tendon injury, calcific tendinitis, etc.
Exclusion Criteria • Patients with glenoid labral pathologies. • Patients with instability disorders. • Patients with any electrically, magnetically or mechanically activated implants (pacemaker, biostimulators, neurostimulators and cochlear implants). • Patients having claustrophobia.
Data Acquisition After clinical evaluation, once a patient satisfied the inclusion and exclusion criteria for this study, he or she underwent sonographic evaluation of the shoulder joint followed by MRI of the affected shoulder.
Ultrasound: The examination on the affected shoulder was carried out on Phillips IU 22 with high frequency linear array transducer (5-12MHz). The patient was made to sit on a rotating stool close to and facing the USG machine. Both static and dynamic examination of the shoulder was performed and comparison to the opposite side was also done.
Techniques: In our study we followed techniques and protocol described by Jon A. Jacobson (10) USG scanning protocol followed in our study is shown in (Table/Fig 1).
Usg – diagnostic criteria: In our study, we used major and minor criteria for diagnosing rotator cuff tears as described by Soble et al., (11) and Chauba (4).
Major criteria were non-visualisation of the cuff, focal non visualisation, discontinuity in the cuff and focal abnormal echogenicity.
Minor criteria were fluid along the biceps tendon sheath and in the subdeltoid bursa, concave subdeltoid bursal contour, irregularity of the greater tuberosity and compressibility.
Full thickness tear: It is focal or complete non visualisation of tendon which presents as an anechoic or hypoechoic defect in tendon extending from articular to bursal surface.
Partial thickness tear: It is presence of hypoechoic or heterogeneously echoic defect extending to articular surface or bursal surface but not completely involving the tendon. When intratendinous longitudinal splits are identified which appear as thin fluid-filled intratendinous line oriented from the bony insertion proximally without exiting onto either the bursal or the articular side of the tendon they are referred to as intrasubstance tears.
Criteria for non-tear related rotator cuff pathologies: Tendon calcification is presence of echogenic structure with marked posterior acoustic shadow.
Tendinosis is depicted as thickened and/or hypoechoic tendon. Effacement of fibrillar pattern of tendon may also be seen in some individuals (12).
Impingement: Subacromial impingement is pooling of bursal fluid at the lateral acromion edge or snapping of bursal tissue indicated (14). Interposition of the supraspinatus tendon between the greater tuberosity and the acromion, as well as direct contact between the greater tuberosity and the acromion are the other signs of impingement (10).
Criteria for non-rotator cuff tear related pathologies: Biceps Tendinopathy is considered when there is thickening or thinning of the tendon, hypoechoic appearance and loss of fibrillar pattern on long axis. Biceps tendon dislocation is considered when tendon is not seen in bicipital groove or when tendon is seen displaced medially or laterally.
Bursa: It is considered pathological when there is fluid distension which appears predominantly anechoic. Appearance of thickened bursal wall is also a diagnostic criteria for inflammation.
Acromioclavicular joint arthropathy is considered when there is narrowing, distension of joint capsule and/or presence of marginal osteophytes (14).
Magnetic resonance imaging: The MRI examination of shoulder was performed on a 1.5 Tesla Philips Achieva. Patient was positioned supine and an approximately neutral position of the arm was obtained by asking the patient to place his hand at the side of the body, with the thumb pointing upwards.
Sense–Flex- M coil was used and centered over the affected shoulder.
Multiplanar images were obtained in the axial, oblique coronal and oblique sagittal planes.
Field of view 16 cm, slice thickness 2-3 mm and matrix 512 x 512 (Table/Fig 2).
MRI Findings: Normal tendons are hypointense on standard MR sequences.
Tears: Increased signal intensity within the substance of such tendons are usually considered pathologic or indicative of injury.
Focal region of fiber discontinuity that is filled with fluid signal as demonstrated on T2-weighted imaging with or without retraction of tendinous fibers from the distal insertion were considered partial tear. Tendon defect extending from the articular surface to the bursal surface filled with fluid signal intensity was the most direct and definite sign of a complete rotator cuff tear. Important secondary signs of cuff tear considered were diffuse loss of the peribursal fat plane and the presence of fluid in the subdeltoid bursa. Muscle atrophy and fluid in the glenohumeral joint, decrease in the acromial humeral distance, presence of AC joint cysts, superior translation of the humeral head with associated remodeling of the under surface of the acromion were other signs (15).
Tendinosis: The typical MR appearance of tendinosis is high signal on short TE sequences, such as proton density sequences. On T2-weighted images, true defects associated with partial tears are hyperintense, contrary to tendon degeneration. Magic angle phenomenon may result in artifactually increased signal in regions where the tendon courses at a 55-degree angle in relation to the main magnetic field. Magic angle artifact usually resolves on T2 weighted (long TE) sequences, thus differentiating it from tendinopathy (15).
The statistical analysis was performed by STATA 11.2 (College Station TX USA). Kappa statistics were used to find the agreement between the USG and MRI findings. Sensitivity, specificity, accuracy, the positive predictive value and the negative predictive value were calculated using cross tabulations. Descriptive statistics were performed. Chi square test were used to find the significance of MRI and USG findings, and it was expressed as frequency and percentage. The p-value <0.05 was considered as statistically significant.
Study design: Total 60 patients with shoulder joint pain were studied and USG findings were correlated with MRI findings. Rotator cuff pathology was the most common outcome in our study and hence was the focus of our study.
Spectrum of pathology: Of the patients with shoulder complaints referred to our department, rotator cuff pathologies were the most common finding and were seen in 57 patients.
USG findings: Among the subjects studied for painful shoulder, on USG majority had supraspinatus tendon [Table/ Fig-3]. This was followed by subscapularis tendon pathologies seen in 32 (53%) patients.
Among the non rotator cuff disorders, acromio-clavicular joint arthropathy was the most common pathology detected on USG (Table/Fig 4).
MRI findings: On MRI, 56 patients showed supraspinatus tendon pathologies. Detailed MRI spectrum of supraspinatus pathologies is represented in (Table/Fig 3). Among the non rotator cuff disorders acromioclavicular joint arthropathy was most common pathology seen in 40(66.67%) patients on MRI other pathologies subacromial-subdeltoid bursa effusion, subcoracoid bursa effusion, acromio-clavicular joint arthropathies, biceps tendinosis and dislocation (Table/Fig 4).
Correlation of USG and MRI findings: In our study, MRI was used as reference standard and out of 60 patients, 49(81.67%) patients showed either partial thickness, full thickness or combined partial and full thickness rotator cuff tears whereas on ultrasonography examination out of 60 patients 42 (70%) patients showed either isolated or combined rotator cuff tears (Table/Fig 3).
Rotator cuff tears: Tear in any tendon, whether in isolation or in combination with other tendons was considered a rotator cuff tear. Overall, MRI showed rotator cuff tears in 49 patients (Table/Fig 5).
USG showed good sensitivity in diagnosing full thickness tears and correctly identified eight out of nine cases of full thickness tears (Table/Fig 5).
Agreement between USG and MRI in diagnosing rotator cuff tears: The agreement between the two methods was assessed using kappa coefficient (Kappa=0.63). The strength of agreement between USG and MRI for the diagnosis of any tear of rotator cuff is considered to be ‘substantial’ in our study (Table/Fig 6).
Shoulder pain being one of the commonest complaints in patients visiting Orthopaedic clinics. Myriad conditions lead to shoulder pain with common ones being tendon inflammation, tendon tear, joint instability, arthritis, fracture and less common ones being infections and nerve related conditions.
In our study rotator cuff pathologies were found to be the commonest cause for referral to Department of Radiodiagnosis which was found similar to study carried out by Mitchell C et al., (16).
Various techniques are used for evaluating patients with shoulder pain including clinical examination, plain radiography, arthrography, USG, CT-scan and MRI. Arthrography traditionally used for diagnosis of rotator cuff tears is invasive technique with many health risks (17). Hence, Ultrasonography and MRI have widely overtaken this technique. Conventional MRI is sensitive and specific, but cannot be used as a first line of investigation. However, USG is a non-invasive, relatively inexpensive modality that can be used.
Rotator cuff tears have been reported the most common rotator cuff pathology with USG showing high sensitivity and specificity for full-thickness tears (Table/Fig 7), but less for partial thickness tears (Table/Fig 8) (18). In the present study we have compared the findings of ultrasound with MRI, using it as a reference standard for the detection of rotator cuff and related pathology in patients referred to our department.
Our study is a prospective observational study involving 60 patients.
Among 60 patients, who complained to have painful shoulder that underwent sonography and MRI, majority of the subjects, 37(62%) patients (21 males and 16 females) were in the age group of 50 –70 years with mean age 56.67. Rotator cuff tears were seen in 31(52%) patients in age group of 50-70 years. Highest incidence of rotator cuff tears in our study was seen in sixth decade of life, similar to that observed by White et al., (19).
In our study, MRI was used as reference standard and out of 60 patients, 49(81.67%) patients showed either partial thickness, full thickness or combined partial and full thickness rotator cuff tears whereas on ultrasonography examination out of 60 patients, 42(70%) patients showed either isolated or combined rotator cuff tears.
USG detected 51 patients and MRI detected 56 patients with supraspinatus tendon pathologies which included tears, tendinosis and calcifications. Zlatkin et al., also found presence of supraspinatus tendon involvement in around 80% of cases in their study (15).
USG of supraspinatus tendon for detection of any tear showed sensitivity of 78.72%, specificity of 84.6%, PPV of 94.87%, NPV of 52.38%, an accuracy of 70 % and a significance of p<0.001.
USG of subscapularis tendon for detection of any tear showed sensitivity of 83.34%,specificity of 96.29 %, PPV of 71.42%, NPV of 98.11%, an accuracy of 95 % and a significance of p<0.001 .
USG of infraspinatus tendon for detection of any tear showed sensitivity of 80%, specificity of 100%, PPV of 100%, NPV of 98.21%, with an accuracy of 98 % and a significance of p<0.001.
Overall, MRI showed rotator cuff tears in 49 patients. Partial thickness tear was present in 40(66.67%) patients which included two patients with intrasubstance tear. Nine (15%) patients had full thickness tear or combined partial and full thickness tear. Rest of the 11(18.34%) patients had intact rotator cuff without any tendon tear. Hence, partial thickness tears were the most common rotator cuff pathology seen in our study.
USG of shoulder correctly picked partial thickness tears in 31 patients which included two patients with intrasubstance tear. Nine patients with partial thickness tears of rotator cuff on MRI were falsely diagnosed on USG as intact rotator cuff, out of which five patients were misdiagnosed to have tendinosis. For full thickness tears, out of nine patients diagnosed on MRI, USG correctly picked eight patients. One patient with full thickness rotator cuff tear was misdiagnosed as partial thickness tear. Five patients had associated dislocation of biceps tendon from bicipital groove all of which were correctly picked up on USG.
USG had a sensitivity of 78.04%, specificity of 89.47%, PPV of 94.11% and NPV of 65.38% in detection of partial thickness tears and a sensitivity of 88.89%, specificity of 100%, PPV of 100% and NPV of 98.07% in detection of full thickness tears. Overall accuracy of USG in detection of any tear was 82%.
The findings in our study are comparable to studies carried out by Bashir et al., (20) and Rutten et al., (21) where they found substantial agreement between USG and MRI in detection of rotator cuff tears. The level of sensitivity and specificity seen in our study closely resembles to that of Cullen et al., who reported a sensitivity of 89% and specificity of 100% in detection of full thickness tear and sensitivity of 79% and specificity of 94% in detection of partial thickness tears (22).
Non tear related rotator cuff and other related pathologies seen were calcification, tendinosis, tendon impingement, subacromial- subdeltoid fluid and bicipital tendon pathologies (Table/Fig 9),(Table/Fig 10),(Table/Fig 11),(Table/Fig 12),(Table/Fig 13).
In our study we found that MRI was less accurate in detecting calcific deposits in tendon. Only one patient was diagnosed to have calcific deposits in supraspinatus tendon on MRI. Zubler et al., also found that detection of smaller amounts of calcification may be difficult with MRI, whereas, Hartig and Huth in a study found USG to show 100% sensitivity in detecting calcific deposits in rotator cuff tendon (23),(24). Hence, our findings were in accordance with literature and USG proved to be a better modality in detection of tendon calcification.
Dynamic examination of shoulder showed sub acromial impingement of tendon in two patients and subcoracoid impingement in one patient.
ACJ arthropathy was the most commonly observed non rotator cuff related pathology in our study. USG correctly identified acromio-clavicular joint arthropathy in 32(53.3%) patients with a sensitivity of 80% and specificity of 95%. Iagnocco et al., also found ACJ involvement in 51.5% patients in their study and considered it to be commonly involved in patients with painful shoulder (25).
USG showed a sensitivity of 44.4% and specificity of 100 % in detection of subacromial-subdeltoid effusion and a sensitivity of 18.18% and specificity of 100% in detection of subcoracoid effusion in reference to MRI. Hence, MRI proved to be a better modality in detection of bursal effusion.
USG showed 100% sensitivity in detection of biceps tendinosis and dislocation.
Thus, in our study we found USG to have good sensitivity, specificity and accuracy for detection of rotator cuff tears. USG and MRI findings showed good agreement in diagnosis of partial and full thickness tears. MRI proved to be superior in characterisation of tear with respect to location and extent. It also proved to be superior in detection of certain non rotator cuff related pathologies like subacromial-subdeltoid effusion, subcoracoid effusion and ACJ arthropathy.
However, USG is cheap, readily available, non-invasive, fast, easily performed reproducible & well tolerated modality (26). Dynamic examination and comparison with contralateral shoulder are added advantages. Rotator cuff pathologies being the most common cause of shoulder pain and USG showing comparable results to MRI in detection of rotator cuff pathology (27), it can be clearly used as a first line investigation modality in assessment of shoulder pain. However, USG has a limitation with respect to inter observer variation and needs a trained Radiologist/Sonologist for interpretation. High frequency probes with good settings for the musculoskeletal ultrasound is needed.
Tissue harmonic imaging [THI] is said to be superior to conventional US in the examination of patients suspected of having rotator cuff tears as joint and tendon surfaces are better seen with use of THI as compared to conventional US (28).
MRI was used as a reference standard which itself is not 100% accurate in detection of rotator cuff pathology. True pathology of rotator cuff was not known as follow-up of all the patients was not available. This could have lead to overestimation or underestimation of accuracy of USG in detection of rotator cuff pathology. Another limitation in our study, symptomatic patients with painful shoulder, who were referred for shoulder MRI were included. The subjects had higher probability for rotator and non rotator cuff pathology and were not fully representative of general patients with shoulder pain. This could have lead to selection bias which caused an increase in positive predictive value and decrease in negative predictive value of USG. Also USG had limited role in evaluation of non rotator cuff related pathologies like bursal effusion, labral tears and ACJ arthropathy in our study.
In our study we concluded that USG can be used as an initial line of investigation for evaluation of all patients with painful shoulder who are clinically suspected to have rotator cuff disorders. Rotator cuff pathologies proved to be the most common cause of shoulder pain and USG showed comparable results to MRI in detection of rotator cuff pathology. Thus, it can be clearly used as a cost effective first line investigation modality in assessment of shoulder pain. Dynamic examination and ability to compare findings with contralateral shoulder were added advantages. It is proved to have high sensitivity and specificity for full thickness tears with relatively less sensitivity and specificity in detection of partial thickness tear.
MRI proved to be superior in estimation of assessment of correct site and extent of tear. It is also proved to be superior in detection of non-rotator cuff related pathologies like subacromial-subdeltoid effusion, subcoracoid effusion, ACJ arthropathies.
|TABLES AND FIGURES|
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