A 7-year-old female spayed German Shorthair Pointer used as a hunting dog presented to Sports Medicine for a 5 month history of right forelimb lameness. At presentation, the dog was bright, alert, and responsive with normal vital parameters. She had a grade 2-3/5 right forelimb and a grade 1/5 left forelimb lameness with mild right shoulder muscle atrophy. She was painful on palpation of the biceps with a mildly decreased range of motion in extension.
At presentation, ultrasound and CT of the bilateral shoulders were performed. Ultrasound clips of the biceps tendon of the right shoulder and a still image of the biceps tendon of the left shoulder are below. CT images of the shoulders (without contrast) are also shown in bone and soft tissue windows in the axial plane.
Biceps – There is severe disruption of the tendon fibers proximally characterized by multiple rounded and linear hypoechogenicities. The tendon sheath is thickened, measuring up to 1.2 mm. Irregular mineral fragments extend into the tendon at the origin. There is a moderate amount of anechoic fluid in the tendon sheath proximally, that distally becomes severe nearing the region of the musculocutaneous junction. Distally, the tendon becomes severely irregular with complete loss of tendon fibers and a normal muscular attachment is no longer seen. Multiple hyperechoic foci are throughout the disrupted tissues in this region. The cortical bone along the bicipital groove and distally is irregular, partially encircling the bicipital groove.
Supraspinatus – The greater tubercle cortical margin has multiple irregularities. No tendon disruption is seen. The craniomedial glenoid rim of the scapula has an irregular cortical margin.
Infraspinatus – There are mild hyperechogenicities near the insertion. Multiple cortical irregularities and defects are along the insertion.
Biceps – Scant pockets of anechoic fluid are at the insertion with a minimal amount of fluid within the sheath. There is mild hypoechoic disruption of the normal fibers, with central hypoechogenicities measuring up to 1.4 mm in diameter. Small hyperechoic foci are along the bicipital groove.
Supraspinatus – Normal insertion and tendon.
Infraspinatus – Deep to the tendon, along the lateral greater tubercle/proximal humerus are multiple irregularities along the cortical margin. A small pocket of fluid is along the insertion of the infraspinatus tendon.
Biceps – The biceps tendon is markedly thickened and mildly heterogeneous with mild mineralization of the tendon sheath at the level of the bicipital groove.
Scapulohumeral joint – There is a mild amount of increased fluid within the scapulohumeral joint with moderate periarticular well-defined mineral proliferation.
Biceps– There is a minimal amount of punctate mineral within the biceps tendon at the level of the proximal humeral diaphysis.
Scapulohumeral joint – There is a mild amount of increased fluid within the joint as well as a mild amount of gas consistent with vacuum phenomenon.
- Biceps tenotomy involving release of the long head of the biceps from the origin is considered a safe, reliable treatment with favorable long-term clinical results and high owner satisfaction and was pursued in this case.
- 3 weeks following presentation, MRI of the shoulders and repeat ultrasound (not shown) were performed under general anesthesia for research purposes and the patient underwent arthroscopic release of the right biceps tendon.
- MRI images of the right shoulder including PD-weighted DIXON IP and W sequences in the dorsal, sagittal, and axial planes are provided below.
Biceps– There is severely increased hyperintensity and heterogeneity of the bicipital tendon extending from the origin to the musculotendinous junction. There is also more focal, severely increased PDw W hyperintensity at the level of the origin of the bicipital tendon upon the supraglenoid tubercle and the margins of the bone are ill-defined and irregular with small hypointense foci extending into the tendon. The biceps tendon is thickened; there is effacement of the effusion within the biceps tendon sheath.
Supraspinatus– The supraspinatus tendon is moderately enlarged and mildly hyperintense, with enlargement and heterogeneity at the musculotendinous junction. There is moderate fluid along its medial aspect, ventral to the subscapularis tendon.
Scapulohumeral joint– There is moderately increased effusion within the right shoulder joint. The caudal joint pouch and the synovium of the tendon sheath is moderately thickened with intermediate tissue signal intensity. There are small osteophytes on the caudal and medial glenoid rim and humeral head. The intertubercular groove is sclerotic with bony proliferation along the margin, some which extends into the overlying bicipital tendon. There is a focus of PDw W hyperintensity within the proximal humerus along the lateral margin of the intertubercular groove.
Other– There is a PDw hyperintense focus at the attachment of the lateral glenohumeral ligment and joint capsule with thinning of the cortex. Musculature of the proximal thoracic limb is thin
Partial or complete tears at the origin of the biceps tendon are increasingly diagnosed in medium to large working dogs. Biceps tendinopathy is commonly associated with supraspinatus tendinopathy, glenohumeral joint synovitis, partial or full thickness articular cartilage defects, periarticular osteophytes, or glenohumeral collateral ligament pathology, which makes global evaluation of the shoulder joint essential prior to treatment. In a report of 24 dogs undergoing tenotomy for primary biceps rupture, 8 dogs had fibrillation of the medial glenohumeral ligament and one was partially ruptured. Although ultrasonography is often the modality of choice for initial evaluation, several reports in the veterinary literature describe shortcomings of this modality in evaluation of the soft tissue structures of the shoulder, particularly along the medial aspect of the joint.
MRI offers superior soft tissue detail and contrast resolution as well as the ability to perform a more global evaluation of the shoulder. In veterinary medicine, the use of MRI for diagnosis of pathology in the performance horse has rapidly expanded over the past decade. Despite encouraging musculoskeletal data in other species, there remain only a few reports in the literature on the performance of shoulder MRI in normal and clinical dogs with no reports on its performance in comparison to other more widely used imaging modalities such as ultrasonography. In a studycomparing MRI findings performed on a 1.0 T magnet with arthroscopy or open surgery, there was 90% agreement and 87% concordance between 53 abnormal soft tissue structures, including pathology of the biceps, subscapularis, and infraspinatus tendons, as well as the medial and lateral glenohumeral ligaments. On MRI, a previous report of biceps rupture in a 5-year-old Labrador reported additional soft tissue pathology including shoulder joint effusion with contrast enhancement of the right shoulder joint capsule as well as thickening and partial rupture of the medial glenohumeral ligament and subscapularis tendon. Although the diagnosis of a biceps rupture may be accomplished with alternative modalities, this case, as well as Violet’s case, demonstrate the complementary information obtained with high field MRI, which may help tailor treatment regimens and optimize patient outcomes.
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