Fractures of the Shoulder

Chapter 102 Fractures of the Shoulder



James K. Roush


Recognition of shoulder fractures is important to allow acute lameness diagnosis and treatment and to protect normal shoulder joint mobility and function. Fractures of the shoulder are often associated with concurrent thoracic trauma and may be associated with ipsilateral brachial plexus injuries or trauma to the overlying soft tissues.



ANATOMY


The shoulder is a diarthrodial joint with a shallow ball-and-socket configuration. Major support structures of the shoulder are the loosely defined medial and lateral glenohumeral ligaments and the joint capsule. Stability is also provided by a number of muscles and tendons that cross the joint to insert on the humerus, including the supraspinatus tendon, acromial and spinous heads of the deltoideus muscle, infraspinatus tendon, coracobrachialis tendon, and teres minor tendon. The biceps brachii tendon provides minimal cranial support to the normal shoulder but is commonly transposed to provide medial or lateral support after traumatic joint luxation.


The scapula is a broad, flat bone with a prominent spine and numerous muscle origins and insertions. It is loosely attached to the chest wall through the insertions of a number of muscles, including the rhomboideus, subscapularis, and trapezius. Scapular areas can be anatomically divided into the body, spine, neck, and glenoid cavity, with differing surgical approaches and treatments recommended for fractures in each area (Fig. 102-1). In immature animals, the dorsal border of the scapula serves as a physis for long bone growth. The distal scapula has no physis for long bone growth, but the supraglenoid tubercle is a secondary center of ossification in the immature dog and this apophysis is often misdiagnosed as a fracture in dogs until radiographic closure from 6 to 7 months of age.


image

Figure 102-1 Percentage of canine scapular fractures occurring in various regions of the scapula from a study of 107 scapular fractures.


(Rohn D, Roush JK: Unpublished data.)


The proximal humerus has a number of defined tubercles with important muscle insertions. The greater tubercle provides insertions for the supraspinatus tendon cranially and the infraspinatus and teres minor tendons laterally. The deltoid tuberosity is a linear protuberence on the lateral aspect of the humerus serving as the insertion for the acromial and spinous heads of the deltoid muscle. The coracobrachialis tendon inserts on the medially located coracoid process of the proximal humerus. There is a proximal humeral physis that closes functionally at approximately 8 months and radiographically at 10 months of age in the dog, and a secondary ossification center composing the greater tubercle is visible in dogs under 5 months of age.


Important soft tissue structures that may be affected by trauma or that are important during surgical approaches include the suprascapular nerve, which crosses the scapular neck from cranial to caudal beneath the acromion; the circumflex humeral vessels, which lie just distal to the teres minor muscle beneath the spinous head of the deltoideus muscle; and the cephalic vein, which lies superficially on the craniolateral aspect of the greater tubercle.



DIAGNOSIS



Clinical Signs


Clinical signs associated with canine scapular and proximal humeral fractures include partial or non–weight-bearing lameness of a forelimb, pain or crepitus during palpation of the scapula or proximal humerus, and pain during manipulation of the scapulohumeral joint. Malposition and soft tissue of the limb at the scapulohumeral joint may be visible and palpable during physical examination. It is important to apply direct pressure along all borders of the scapula and along the scapular spine while observing the animal for signs of pain to detect greenstick or minimally displaced scapular fractures.



Radiography


Definitive diagnosis of scapular fractures is by radiography. Reported radiographic views of the scapula include caudocranial, mediolateral, dorsally displaced mediolateral, and distoproximal. Any or all of these views may be useful for the surgeon’s understanding of the fracture’s configuration. Frequently, computed tomography (CT scan) of the scapula is useful to determine the degree of comminution and provide operative planning, particularly with the addition of three-dimensional reconstructions of the fracture available in some software. In a study of 107 dogs with scapular fractures, 28% were comminuted fractures, but only one fracture was an open fracture. Nuclear scintigraphy of the scapula may be useful to identify non-displaced scapular fractures. In young animals, diagnosis of supraglenoid tubercle fracture should not be made until comparison with radiographs of the opposite scapula indicates an obvious displacement of the affected supraglenoid tubercle.



FRACTURES OF THE SCAPULA



Preoperative Considerations



• Treatment of scapular fractures varies by the location and configuration of the fracture, the degree of displacement of the fragments and their effect on distal limb position, and the location and degree of involvement of the articular surfaces by the fracture.

• In a study of 107 dogs with scapular fracture, the scapular body had the most fractures (50%). Fractures of the articular surface of the glenoid were found for only 9% of dogs, with 6 of 9 dogs involving only the supraglenoid tubercle (Fig. 102-1).

• Non-displaced or minimally displaced fractures of the scapula body and spine are best treated by strict cage confinement.

• Application of a Velpeau sling has been advocated, but it generally provides no advantages over adequate cage confinement and has the disadvantage of resulting in decreased humeral joint function and increased joint stiffness from the immobility period.

• Perform surgery for fractures of the scapula or proximal humerus in lateral recumbency with the limb prepared for aseptic surgery. Surgical approach is dependent on the area of exposure needed for the particular fracture, but a number of described surgical approaches are useful, including the lateral, craniolateral, and caudolateral approaches and variations of these approaches combined with acromion osteotomy, greater tubercle osteotomy, and infraspinatus tenotomy.

• Because of the extensive number of muscles and tendons crossing the joint, adequate exposure of the glenoid surface during surgery may require osteotomy of any or all supraglenoid or greater tubercles or of the acromion. These are reattached at the conclusion of the primary fracture repair by lag screw or tension band fixation.


Equipment



• Standard orthopedic pack and bone reduction forceps

• Orthopedic wire (20 and 22 gauge, or 0.8 and 1.0 mm) and wire twisters

• Selection of Kirschner wires and small Steinmann pins

• Bone plating sets, including 2.0-, 2.7-, and 3.5-mm screws to accommodate all animal sizes, and a variety of bone plates, including miniplates, dynamic compression plates, T plates, L plates, and reconstruction plates


Scapular Body Fractures


Fractures of the scapular body comprise 50% of all scapular fractures and are often transverse or oblique. The thinness of the scapular body results in difficulty in finding purchase for surgical implants; thus, minimally displaced or non-displaced fractures are treated by cage confinement. Fractures of the proximal half of the scapular body are often comminuted but are also adequately treated by cage confinement for an extended period.



Technique Overview



• If internal fixation is necessary to prevent limb shortening and malalignment, treat fractures of the scapular body by placement of appropriately sized plates across the fracture fragments.

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Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Fractures of the Shoulder

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