Challenging forelimb lameness: The shoulder (Proceedings)

Diagnosing and treating forelimb conditions in dogs can be very challenging. Many dogs present with a similar history including minimal responsive to rest and non-steroidal anti-inflammatory drugs and increased lameness following exercise and heavy activity. It can be difficult to localize the lesion on palpation as many dogs may show increased sensitivity in the shoulder and elbow from referred pain and compensation. To further challenge the veterinarian it is not uncommon for diagnostics such as radiology to be within normal limits due to the soft tissue nature of these injuries (tendon, ligament, and cartilage). Fortunately, with the availability of advanced diagnostics (arthroscopy, MRI, CT scan, ultrasound, etc) the definitive diagnosis can be determined and an appropriate treatment plan created. Depending on the diagnosis (tendon, ligament, cartilage lesions, etc) treatment options may include arthroscopic treatments, stem cell therapy (SCT), platelet rich plasma (PRP), rehabilitation therapy and medical management.

Supraspinatus Tendinopathy

In humans and dogs, several degenerative disorders in the insertion of the supraspinatus tendon have been identified, including rotator cuff tears, calcifying tendonitis or tendinosis, and tendinosis as a result of overuse. Degeneration of the supraspinatus tendon has been suggested to be a factor in the development of rotator cuff tears in humans. Overuse injury has been suggested as the cause of this disorder, and the role of overuse in the pathogenesis has been supported by findings of experimental studies. Histologically, affected tendons contain discontinuous and disorganized collage fibers. Typically, no inflammatory cells are detected. In chronic cases, a proliferative nodule develops which can cause biceps brachii tendon displacement and pain.

Dogs commonly present with a history of a chronic unilateral weight-bearing lameness that is exacerbated with activity and often refractory to treatments. Supraspinatus atrophy may be noted and discomfort may be elicited by direct palpation over the tendon and during flexion of the shoulder. It is not uncommon to identify concurrent BT or medial shoulder instability (MSI), therefore a thorough shoulder exam including biceps test and abduction angles are required.

Enhanced imaging using MRI is able to readily visualize the condition in the acute phase. Plain radiography and CT Scan may reveal mineralization just cranial to the greater tubercle in chronic cases. Ultrasound may also a useful modality for diagnosing this condition. Arthroscopic exploration may identify "impingement" of the biceps tendon secondary to supraspinatus tendon swelling as well as possible MSI pathology.

Depending on the severity, treatment options may include rehabilitation therapy (manual therapy, modalities, therapeutic exercise, etc), platelet rich plasma (PRP), and stem cell therapy. In chronic cases, it is necessary to re-initiate the inflammatory process to stimulate the healing response.

Surgical treatment is warranted for those that do not respond to conservative medical management and rehabilitation therapy. Surgical treatment should include arthroscopic exploration to identify and treat concurrent BT and/or MSI if noted, or resection of abnormal tissue through an open approach. Surgery has been considered the treatment of last resort in humans with tendinosis because of the small reported difference in treatment success between surgical intervention and conservative management.

Bicipital Tenosynovitis

Another common shoulder condition seen in active dogs is bicipital tenosynovitis (BT), which involves the biceps brachii muscle and its tendon that crosses the shoulder joint. The biceps flexes the elbow and extends and stabilizes the shoulder joint during standing or during the weight-bearing phase of locomotion.

Cause

The cause of injury in performance dogs appears to be related to repeated strain injury. This includes two-on/two-off contacts, landing vertically on the forelimbs from a misjudged jump, overstretching of the muscle, quick turns, and repetitive contractions of the muscle with the shoulder flexed and/or the elbow extended. Injury to the tendon can occur in a number of ways including strain from overloading, degeneration, or disruption. A single less than maximum load may injure some of the fibers without complete failure of the tendon, but the blood supply to the tendon proper is poor, leading to a longer healing time. Repetitive strain injury may initiate actual degeneration of the tendon. As the area continues to be reinjured, the tendon may weaken sufficiently for inflammation and/or microtears (tendinopathies) in the connective tissue in or around other tendons to form, ultimately leading to shoulder joint instability.

Diagnosis

Performance dogs with BT commonly have difficulty with quick turning to the affected side and are reluctant to jump. Agility dogs may also have issues performing two-on/two-off contacts and knocking bars with their forelimbs. On gait analysis, dogs with BT often have a shortened stride and a weight-bearing lameness (subtle to severe) that becomes worse with activity. Pain may be elicited by direct palpation over the biceps tendon. Pain and spasm may be noted when flexing the shoulder while at the same time extending the elbow. Radiographs are of minimal assistance when the injury is in its acute phase, but may reveal mineralization of the tendon when the condition is chronic. MRI (magnetic resonance imaging) and ultrasound may be used to identify the condition in acute and chronic situations. Shoulder arthroscopy is recognized as superior to other diagnostic procedures for diagnosis of bicipital tenosynovitis.

Treatment

Acute cases of bicipital tenosynovitis may be treated by conservative medical management and rehabilitation therapy. Conservative medical management should include controlled activity, non-steroidal anti-inflammatory drugs (NSAIDs), cryotherapy, and possibly intra-articular injections of hyaluronic acid or cortisone. To promote healing and decrease adhesion formation, laser therapy is recommended to increase circulation and to remove waste products. Acupuncture also can be used to promote healing and decrease pain levels. Initiating low load, pain-free, high repetition exercise and range of motion (ROM) movements early in the healing process is important. Pain relief and reduction of inflammation can be achieved with electrical nerve stimulation therapy. Acute tendon injuries should not be stretched because of the potential for producing more microtears due to the chemical changes in the tissue. Pain-free, passive ROM movements (flexion and extension of the limb while the dog is not weight bearing) and gentle wobble board activities (all directions, front to back and side to side), and alternating leg lifts are recommend first, with progression to active ROM exercises (weight-bearing exercises that cause flexion and extension of the limb). All exercises in the acute stage are aimed at increasing the strength of the shoulder and scapular stabilizers. Balance and proprioceptive exercises are the requirements and are imperative to the healing process. An active dog will require stabilization of this region and strength of the slow twitch muscle fibers before resuming activity. Deep friction massage is utilized at this stage if the dog is not too painful. At this stage, a sweeping motion is made across the bicipital tendon for five minutes, daily if possible. The goal is to help realign the fibers of the inflamed tendon. Cyrotherapy is recommended after the cross friction massage, and laser therapy prior to. A strengthening program consisting of controlled leash walking, stepping over cavaletti, wobble board use, and stabilizing exercises should follow. Examples of stabilization exercises include balancing on a well controlled rocker board, standing on a theraball, weight shifting exercises, wheel barrowing the dog so their weight in on the forelimbs, walking in figure eights and walking in circles. Leash walks of increasing duration and end-stage eccentric exercises, such as walking and trotting down hills may then be introduced. Short periods of off-lead activity are allowed after leash walks have substantially increased without the return of lameness. In the acute stages, it is imperative to reinforce the owner or handler not to perform any activity that produces a lameness. Many owners of performance dogs are eager to return to sports and will often push the dogs too quickly.

With chronic BT, the inflammatory process must be reinitiated to break down scar tissue and remodel the tendon fibers into the proper orientation, which increases the tendon's load capacity. Because of the need to reinitiate the inflammatory response, NSAIDs or intra-articular corticosteroids are not recommended for chronic tendinopathies. Appropriate therapy for chronic tendinopathies includes deep cross-friction massage, heat, and ultrasound therapy. At this stage, cross friction massage is applied for ten to twenty minutes, two to three times per week. Acupuncture and laser to increase circulation and for pain control may be beneficial. The exercise progression is similar to that recommended for acute tendinopathies, but stretching after treatment is advised. Active ROM exercise such as walking for longer periods also is recommended. End-stage eccentric exercises, such as walking and trotting down hills should be added followed by short periods of off-lead activity provided lameness is completely resolved.

Because of the chronic nature of the tendon changes, the dog will usually take longer to recover and progress through the healing and exercise stages. It is again imperative to construe to the owner and handler that the progression of conservative management of BT may be lengthy and nothing should be done to aggravate the condition. The dog should be pain free and not exhibit any lameness.

Surgical treatment is recommended for chronic cases of BT that are not responsive to medical management or rehabilitation therapy. Surgical options include tenodesis (releasing and reattaching the tendon at a distal location on the proximal humerus) or an arthroscopic tendon release. Controlled activity is an important component during the postoperative period and should include leash walks of increasing duration and end-stage eccentric exercises, such as walking and trotting down hills. Short periods of off-lead activity are allowed once the lameness has resolved. NSAIDs may be used to decrease pain and inflammation following surgery. Modalities as described for the acute treatment of BT may be utilized post-operatively to improve comfort and function and facilitate progression to the retraining phase of recovery.

Toward the end of rehabilitation therapy retraining should begin. Examples of retraining techniques for BT may include starting with low, straight-line jumps with very wide sweeping turns that progress over time to higher jumps with tighter angles. Do not include the A-frame and weave poles until late in the retraining period. Alterations in contact controls from a two on/two off to a running or four on the floor may be necessary. Be sure to start with turns toward the injured limb and progress to turns toward the uninjured limb.

Dogs that will be returning to jumping activities need to start off with low level activities prior to returning to the sport. In jumping activities, the biceps muscle and tendon acts eccentrically to control the landing of the body. After cavaletti work has been utilized, low level jumping can be imitated. The jump heights should be set lower than the dog's normal jump height. For example, if the dog normally jumps twenty two inches in competition, the jump height should be set at sixteen inches. Three or four jumps should be set up and the surface should be padded or performed in sand. Three to five repetitions should be performed of the jump sequence – the dog going over the jumps – and then the dog should be reevaluated. The jump sequencing should not cause any lameness and should only be performed three times per week with at least a 48 hour break in between. Plyometrics should be progressed by increasing the jump height and the number of repetitions should be increased. Once the dog is up to its normal jump height on a controlled surface, additional training surfaces can be added.

Following a warm-up, make sure to perform active stretching techniques. Following agility work, use an appropriate cool down with ice therapy (5 minutes on, 5 minutes off, 5 minutes on) and passive stretching techniques (including shoulder flexion with elbow extension). Treadmill walking and the use of underwater treadmill are absolutely appropriate for the rehabilitation of BT. In acute stages, exert caution with swimming since the shortened position of the biceps tendon may aggravate the condition.

Medial Shoulder Instability (MSI)

Currently, the exact cause of MSI in dogs is unknown, although it is suspected to be related to chronic repetitive activity, or overuse rather than trauma. Overuse of the shoulder support structures leads to degeneration of the tissues, lowering the tensile strength of the tissues predisposing them to fraying, disruption, and eventually complete breakdown.

Sporting athletes that participate in activities such as agility, undergo extreme stresses on their muscles, ligaments, and tendons. Repetitive activities such as jump- turn combinations and weave poles are performed regularly during practice and at weekend trials. These routine maneuvers place the shoulder near its end range of abduction, stressing the soft tissues of the medial shoulder complex. Additionally, events such as slipping on wet surfaces, mishaps on the dog walk, teeter, or A-frame may also contribute to the trauma inflicted on the shoulder while participating in performance activities. Over time, there may be a cumulative effect of the micro trauma occurring to the ligaments, tendons and joint capsule, leading to a decrease in performance.

Dogs with MSI may present with a varying degree of history and clinical signs. The history may range from dogs that are missing cues or refusing tight turns during performance to dogs with intermittent unilateral forelimb lameness. It is not uncommon to have a history from therapists (rehabilitation therapists, massage therapists or chiropractors) that identify restrictions, spasm and trigger points, or mild atrophy in the effected shoulder during routine sessions. The history of dogs with more chronic condition typically includes a non-responsive effect to rest and non-steroidal anti-inflammatory drugs (NSAIDS) and dogs that are commonly worse after exercise and heavy activity.

Gait analysis may range from a mildly shortened stride in the affected forelimb at a walk and a trot to a significant weight-bearing lameness. Depending on the chronicty, atrophy may be noted in the affected shoulder on physical examination. Forelimb circumference may be decreased in the effected forelimb when compared to the contralateral unaffected forelimb. Dogs with MSI typically have a restriction and decreased range of motion in extension. When placing the shoulder into abduction spasm and discomfort are almost always noted. In more severe cases, it is not uncommon to feel a slight "thud" or subluxation when abducting the shoulder. If a concurrent supraspinatus tendinopathy is present pain may be noted when placing the shoulder into flexion (direct stretch of the supraspinatus) or on direct palpation of its point of insertion.

Because preoperative diagnosis of MSI is critical for clinical decision making, a palpation technique has been developed which is know as the shoulder abduction test. This test aids in assessment of the passive stabilizers of the medial aspect of the shoulder joint. Using this palpation technique, it has been reported that a normal mean shoulder abduction angle is approximately 30°. The abduction angles in shoulders with MSI are typically significantly larger. In addition, the abduction angles in affected shoulders are typically significantly larger than the contralateral unaffected shoulders in dogs with unilateral MSI. Because MSI is typically a unilateral problem comparison of the maximal abduction angle between limbs can be diagnostic for unilateral MSI.

In addition to history, signalment, gait analysis, physical examination, orthopedic and neurologic examinations, and abduction angle tests, further diagnostic tests used to differentiate causes of shoulder pathology currently consist of hematology, biochemical profile, urinalysis, arthrocentesis, imaging modalities, and arthroscopy. Most imaging modalities available to practitioners for evaluating forelimb lameness offer minimal objective diagnostic support for evaluation of the cause of shoulder lameness. Current imaging modalities include radiographs, computed tomography (CT), ultrasonography, magnetic resonance imaging (MRI), and arthroscopy and each has limitations. However, arthroscopic evaluation of the shoulder joint of dogs allows for direct observation of all major intra-articular structures with magnification, "dynamic" evaluation of tissues during shoulder range-of-motion tests, and "palpation" of intra-articular tissues using arthroscopic instrumentation. Using these techniques during exploratory arthroscopy of a dog's shoulder, it is evident that some shoulder lameness can be attributed to shoulder instability because of changes in the tissues responsible for joint stability. Arthroscopic exploration with evaluation of intra-articular structures provides a definitive diagnosis of MSI.

Based on the results of the orthopedic examination, abduction angle tests, and arthroscopic scoring, patients are placed into one of three treatment categories; mild, moderate, or severe. For patients with abduction angles of 30° - 45° and arthroscopic findings consisting of mild pathology (inflammation without fraying, disruption, or laxity of the MGL, subscapularis tendon, joint capsule) patients are placed in a shoulder support system / hobbles (http://Dogleggs.com) and entered into a rehabilitation therapy program.

Dogs with moderate pathology (moderate category) typically have abduction angles that range from 45° - 65°, and arthroscopic findings consisting of fraying, disruption, and laxity of the subscapularis tendon, medial glenohumeral ligament, focal synovial proliferation associated with the subscapularis tendon, and synovial hypertrophy or hyperplasia. Additional findings may occasionally include a bulge of the suraspinatus tendon with biceps impingement. Dogs in this category are typically treated arthroscopically with radiofrequency (RF) treatment and/or imbrication, or tightrope stabilization. Dogs are placed in hobbles for 12 weeks and entered into a rehabilitation therapy program.

Dogs with severe MSI typically have shoulder abduction angles greater then 65°. Arthroscopic findings usually include complete tears of the medial glenohumeral ligament and severe disruption and the supscapularis tendon and joint capsule. For this type of injury, reconstruction of the medial compartment by direct tissue reapposition and synthetic capsulorrhaphy by a medial approach or TightRope stabilization may be indicated. Following surgical repair, dogs may be placed in a custom non-weightbearing velpeau sling for 1-2 weeks followed by the shoulder support system (hobbles) for 3 months. Rehabilitation therapy is required for a longer period of time as recovery following primary reconstruction ranges from 4 to 6 months. Fortunately, severe cases are less common and are usually due to trauma rather than repetitive activities as seen in the mild and moderate categories.

Appropriate postoperative care is a critical factor in dogs with MSI. Physical Therapy for orthopaedic conditions has a strong scientific background in human medicine. Many studies have shown the benefits of rehabilitation following rotator cuff surgery. The canine rehabilitation therapist should be aware of and apply what is known to be effective in human practice. Many of the same goals, strategies and techniques will be applied in the following Rehabilitation Protocol. It should also be noted that this protocol is given as a guideline to rehabilitation, regular monitoring of the exercise program and its progression is necessary for full benefit. Be aware that not all exercises work for every patient, some exercises will require trial and error to achieve desired results.