Forelimb lameness can often be a diagnostic challenge in sporting breeds and active family pets. Commonly the owner reports
the presence of a long standing lameness which has not resolved with the application conservative treatment modalities such
as physical therapy (rest, therapeutic ultrasound, aquatic therapy), NSAIDs, nutraceuticals, and other traditional modalities.
Frequently physical examination is unrewarding other than the finding of an obvious forelimb lameness. Although it is beyond
the scope of this presentation to discuss all pathologic conditions of the forelimb, more common problems and application
of imaging modalities to facilitate the achievement of an accurate diagnosis will be addressed.
Forelimb lameness can be a diagnostic challenge in the athletic dog; often the lameness has been treated for months with no
improvement. The only abnormal physical finding may be the observation of Grade 2 or Grade 3 lameness. The source of lameness
may be attributed to soft tissue injury, bony injury or a combination of both. In the active adult dog the most common cause
of latent forelimb lameness can be attributed to pathology in the elbow and to injury of the active and passive shoulder restraints.
In the author's experience, pathology in the elbow is regularly caused by occult microfracture/fragmentation of the medial
coronoid process. There is no joint effusion, loss of motion, pain, or crepitus on physical examination. Radiographs are reported
as normal or may show minimal subtrochlear sclerosis of the ulna.
Modalities to facilitate an accurate diagnosis in these cases are CT, nuclear scan, and arthroscopy. Recommendations for
performing CT include scanning from the point of the olecranon to 2cm distal to the radial head. Scan thickness should be
1-2mm with .5mm overlapping slice index. Transverse slices using 1500 to 3500 HU are ideal for imaging subchondral bone and
fragments of the medial coronoid; transverse images at 3500HU are considered ideal for identifying ostomalacic lesions of
the medial coronoid.
Nuclear scintigraphy can be used to localize the origin of the lameness and can be used to facilitate detection of subtle
pathologic changes before changes are evident of radiographs. Technetium phosphonates are typically used for scintigraphy
of joint tissues. Scintigraphy has high sensitivity for detection of presence of elbow pathology but is not specific for definitive
diagnosis. Regulatory issues often limit the use of scintigraphy to academic institutions or large referral practices. Nevertheless
it is invaluable facilitating lesion localization in dogs with forelimb lameness. Most commonly, it is used to rule in or
rule out elbow pathology. Note in the cases shown below the uptake in technetium in the involved elbow compared to the normal
elbow. Each of the below cases had a long standing undiagnosed forelimb lameness. Radiographs of these cases were considered
within normal limits. The use of scintigraphy localized the lesion to the elbow which then allowed application of more specific
diagnostic modalities such as CT or arthroscopy.
Arthroscopy is more invasive than imaging modalities but is very specific for identification of pathology in the medial compartment
of the elbow. A comparison of CT with arthroscopy showed that these procedures were complimentary for medial coronoid assessment.
Care must be exercised when assessing the medial coronoid on CT and arthroscopically. Fragmentation of the articular cartilage,
micro fissures and nondisplaced fragments may not be detected on CT. Likewise, with arthroscopy, thorough probing and or
curettage adjacent to the radial head often will reveal abnormal bone or fragments beneath the cartilage surface not visualized
on with casual observation.
Passive and active restraints of the shoulder joint may present as subtle injuries difficult which are difficult to identify.
Medial restraint (cranial arm of the medial collateral ligament) injury may occur resulting in subluxation of the glenohumeral
joint. The hall mark of diagnosis on physical exam is the abduction test. Comparing abduction of the involved limb with
the normal limb will show a side to side difference in abduction laxity. Caution must be exercised when performing the exam
that internal rotation of the shoulder does not accompany abduction. If the latter is the case, a false positive test will
result; as such, the shoulder must be kept in neutral position when abducting the limb. Additionally, a dog with a long standing
lameness will have cuff muscle atrophy which will give a false positive abduction test. MRI has been used to identify normal
restraints in the shoulder as well as identify abnormal mild lesions in the shoulder. Although early evidence shows this
to be a viable modality, it is not widely available.
Bicipital tenosynovitis is an inflammation of the biceps brachii tendon and its surrounding synovial sheath. The etiology
of bicipital tenosynovitis is either direct or indirect trauma to the bicipital tendon or tendon sheath. Direct trauma due
to repetitive injury may be an inciting factor and result in partial or complete tearing of the tendon. Indirect trauma secondary
to proliferative fibrous connective tissue, osteophytes or adhesions between the tendon and sheath limit motion and cause
pain. It has been hypothesized that thickening or mineralization of the supraspinatus tendon causes a secondary mechanical
bicipital tenosynovitis. Radiographically, bone resorption at the supraglenoid tuberosity is characteristic of chronic strain
at the origin of the biceps tendon. Ultrasound of the cuff muscles is also a useful modality for diagnosing cuff muscle injury
and differentiating which muscle(s) is involved.