Shoulder Musculo-Tendinous Pathology: Problems of the Biceps, Supra and Infra Spinatus
Professor of Small Animal Surgery, Director of the Companion Animal Department, Ecole Nationale Vétérinaire de Lyon
Marcy L' Etoile (France)
PATHOLOGY OF BICEPS BRACHII TENDON
The biceps brachii tendon inserts on the supraglenoid tubercle, then crosses the shoulder joint cranio-medially and gains the intertubercular groove of the humerus in which it is secured by the transverse ligament. The synovial sheath of the tendon is an extension of the scapulo-humeral joint synovium and capsule. The amount of cranial support to the shoulder joint provided by the biceps tendon is controversial. The biceps brachii muscle acts both as an extensor of the shoulder joint and a flexor of the elbow joint.
BICIPITAL TENOSYNOVITIS (BT)
BT is an inflammatory situation of the tendon and its synovial sheath, which may be related to repeated direct or indirect trauma, cranial migration of joint mice in osteochondritis dissecans or synovial osteochondromatosis, or with DJD of the shoulder joint. It is generally seen in medium to large breed dogs, with an acute or chronic onset of lameness and an atrophy of deltoid, supra and infraspinatus muscles.
The precise diagnosis is not easy to make, the only "specific" criteria being a pain elicited when the shoulder is flexed and the elbow fully extended. Applying a direct pressure on the tendon is generally painful, more obviously in the previously described position.
Plain radiograph is of poor interest at the beginning, but may demonstrate some osteophytic deposition in the intertubercular groove in chronic situation. Arthrography may demonstrate adhesions between the tendon and the synovium. Echography may be of interest, as is arthroscopy. The diagnosis often relies on eliminating other causes of shoulder lameness.
In acute cases, conservative treatment with strict rest (3 to 4 weeks) and NSAID therapy is usually sufficient. Intra-articular or peritendinous injection of 40 to 60 mg of methylprednisolone, repeated 3 weeks later may be considered.
If conservative measures fail, surgical treatment is recommended. The goal is to eliminate pain by preventing the movement of the biceps in its inflamed sheath. Several techniques have been described: section of the transverse humeral ligament, section of the origin then displacement of the tendon out of the intertrabecular groove and reattachment to the supraspinatus through a bone tunnel, section of the tendon and reattachment to the proximal humerus by a bone screw and spiked washer, section of the tendon without reattachment (via arthroscopy). Postoperatively, the dog is confined for 3 weeks with a Velpeau sling, and exercise increases progressively to normal at 6 weeks postoperatively.
RUPTURE OF THE TENDON OF THE BICEPS BRACHI MUSCLE
In the growing dog (4 to 8 months) there is generally an avulsion of the supraglenoid tubercle, which can be seen on a plain X-ray and treated by a bone screw or Kirschner wires and a tension wire fixation.
In the mature dog, the rupture of the tendon occurs near its origin on the tubercle. The lameness is generally obvious, but flexion of the elbow is only lightly impaired during locomotion. Diagnosis is difficult: plain X-rays are generally sub-normal, some cranial joint hyperlaxity may be present on physical examination. Arthrography may be of interest if there is a filling defect in the lesion area. Arthroscopy, if available, is interesting. Suturing or reattachment of the tendon may be difficult, so a tenodesis with relocation of the tendon on the proximal humerus (see tenosynovitis) is usually considered as an appropriate treatment. Treatment of bicipital tenosynovitis by section of the tendon without reattachment may give interest to conservative treatment?
MEDIAL DISPLACEMENT OF THE TENDON OF THE BICEPS BRACHI MUSCLE
This uncommon injury has been described mainly in greyhounds. Displacement of the tendon out of the intertrabecular groove is secondary to a rupture, distension or agenesia of the transverse ligament.
Lameness is exacerbated with exercise. When manipulating the shoulder, and palpating the intertrabecular groove area, the tendon may be felt to slip out of the groove on flexion of the joint, then return in a normal position on extension. Treatment relies on replacing the tendon in normal position, then forming a roof over the groove with a small plate, a staple, or a wire. Tenodesis of the tendon with fixation to the proximal humerus may be considered.
INFRASPINATUS MUSCLE CONTRACTURE
This condition occurs most likely in hunting (or working) dogs. The history is generally associated with an acute onset of unilateral lameness during exercise, which improved gradually, 2 to 4 weeks before onset of characteristic gait abnormality. The problem is related to a post-traumatic fibrosis and contracture of the infraspinatus muscle which limits the range of motion (&extension) of the shoulder joint. At rest, in sitting position, the elbow may be held flexed, with the distal limb adducted and externally rotated. At the walk, there is a persistent outward rotation and abduction of the elbow. Manipulation of the shoulder is not painful but demonstrate limitation of motion.
Treatment is related at restoring normal forelimb function by tenotomy of the infraspinatus muscle, which can be performed by a direct approach, lateral to the greater tubercle, immediately followed by mobilisation of the joint to breakdown adhesions. The limb is left unbandaged. The prognosis for full recovery is excellent.
MINERALIZATION OF THE SUPRASPINATUS TENDON
Mineralization of the supraspinatus tendon, close to its attachment on the greater tubercle, has been described as an uncommon cause of lameness in medium to large size dogs, 3 to 4 years of age. The lameness is a chronic, weight bearing one, which worsens during exercise. On plain medio-lateral X-rays, mineralization is observed, but is more precisely localised (in relation to bicipital tendon) on cranio-caudal X-rays with the shoulder flexed, or on proximo-distal projection.
Whether mineralization of the supraspinatus tendon is always pathologic and what treatment is the best one are controversial. A retrospective study (Laitinen & Flo) emphasizes the good results of conservative treatment (3 months rest, NSAID, possibly intra-articular injection of methylprednisolone). Surgery should be used if conservative treatment fails, or in case of mineralization close to the tendon of the biceps, which may be a cause of tenosynovitis.
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