Scapular Fractures

Scapular fractures are traumatic disruptions of the scapula, a flat, triangular bone that connects the forelimb to the axial skeleton via the synsarcosis (muscular attachment) rather than a true synovial joint. The scapula consists of a body, spine, acromion, coracoid process, glenoid cavity, and supraglenoid tubercle. Fractures can involve the body, spine, acromion, neck, glenoid, or supraglenoid tubercle, and may be classified as articular or non-articular. These fractures are relatively uncommon in small animals, accounting for approximately 1-3% of all fractures. They often result from high-energy trauma such as vehicular accidents, falls from heights, or kicks. Surgical management is frequently indicated for displaced, articular, or unstable fractures to restore normal glenohumeral joint congruity and limb function. Non-displaced, stable fractures of the body may be managed conservatively, but surgical fixation is preferred for most fractures to ensure optimal healing and early return to function.

The primary etiology of scapular fractures is high-energy trauma, including vehicular accidents (most common), falls from significant heights, kicks from large animals, and direct blows. Less common causes include pathological fractures secondary to neoplasia (e.g., osteosarcoma, chondrosarcoma), infection (osteomyelitis), or metabolic bone disease (e.g., hyperparathyroidism). Iatrogenic fractures can occur during surgical approaches to the shoulder or thoracic cavity. In young animals, physeal fractures of the supraglenoid tubercle or acromion may occur due to avulsion forces. Biomechanically, the scapula is protected by overlying muscles, but direct lateral or dorsoventral forces can cause fractures. The body and spine are particularly vulnerable to bending and torsional forces, while the neck and glenoid are susceptible to shear forces during shoulder trauma.

Scapular fractures are uncommon in dogs and cats, representing approximately 1-3% of all fractures in these species. They are most frequently seen in young to middle-aged animals, with a slight male predisposition due to higher activity levels and increased exposure to trauma. There is no strong breed predisposition, but large and giant breeds may be overrepresented due to higher energy trauma. Working dogs, such as police and military dogs, may be at increased risk. In cats, scapular fractures are often associated with high-rise syndrome (falls from heights). The majority of fractures are unilateral, with no significant side predilection. Articular fractures involving the glenoid are less common but carry a higher risk of long-term osteoarthritis.

The pathophysiology of scapular fractures involves direct mechanical disruption of bone architecture, leading to pain, hemorrhage, and soft tissue damage. Fracture displacement is influenced by the pull of attached muscles: the supraspinatus and infraspinatus muscles pull the supraspinous fossa cranially, while the subscapularis and teres major pull the caudal aspect. The biceps brachii originates from the supraglenoid tubercle, and avulsion fractures of this tubercle occur due to sudden contraction of the biceps. Articular fractures of the glenoid disrupt the smooth cartilage surface, leading to cartilage damage, hemarthrosis, and subsequent osteoarthritis. Fractures of the neck can compromise the suprascapular nerve, which runs around the neck, leading to supraspinatus and infraspinatus muscle atrophy. Severe trauma may also cause concurrent thoracic trauma, including pneumothorax, pulmonary contusions, and rib fractures, due to the proximity of the scapula to the thoracic wall. Systemic inflammatory response syndrome (SIRS) can develop secondary to significant tissue trauma, leading to systemic effects.

Intrinsic factors include age (young animals have open physes, making them prone to physeal fractures), breed (large and giant breeds may have heavier musculature and greater forces), and body condition (obesity may increase force transmission). Genetic factors are not well-defined, but conditions like osteogenesis imperfecta may predispose to fractures. Extrinsic factors include high-energy trauma (vehicular accidents, falls), environmental hazards (e.g., being hit by a car), and management factors (e.g., unsupervised outdoor activity). Prior surgeries or pathological weakening of bone (e.g., neoplasia, infection) also predispose to fractures. Excessive activity or athletic training may increase the risk of stress fractures, though rare.

Clinical signs include acute onset of non-weight-bearing lameness or severe weight-bearing lameness of the affected forelimb. The limb may be held in a flexed or abducted position. Palpation of the scapular region may elicit pain, crepitus, and swelling. There may be visible deformity or asymmetry of the shoulder region. If the fracture is open, there may be a wound communicating with the fracture site. Concurrent thoracic trauma may cause dyspnea, tachypnea, or muffled heart sounds. Neurological deficits may be present if the suprascapular nerve is injured, leading to muscle atrophy over time. In cases of articular fractures, joint effusion and pain on manipulation of the shoulder joint are common. Systemic signs may include tachycardia, pale mucous membranes, and hypothermia due to shock.

Differential diagnoses include: 1) Shoulder luxation (traumatic or congenital) - presents with similar lameness and pain, but radiographs show joint incongruity without fracture; 2) Proximal humeral fractures - pain and swelling localized to the humerus, radiographs confirm fracture location; 3) Bicipital tenosynovitis - chronic forelimb lameness, pain on palpation of the biceps tendon, ultrasound or MRI findings; 4) Osteosarcoma of the scapula - progressive lameness, palpable mass, radiographic bone lysis and proliferation; 5) Osteomyelitis - history of penetrating wound or prior surgery, radiographic changes with periosteal reaction and sequestra; 6) Suprascapular nerve injury - muscle atrophy, but no fracture on radiographs; 7) Panosteitis - shifting leg lameness in young dogs, radiographs show medullary sclerosis; 8) Hypertrophic osteodystrophy - metaphyseal pain and fever in young dogs, radiographic changes; 9) Cervical spinal cord disease - forelimb lameness with neurological deficits, spinal radiographs or MRI; 10) Soft tissue trauma (muscle contusion or laceration) - no fracture on radiographs, but soft tissue swelling.

The diagnostic algorithm begins with a thorough history and physical examination, including assessment of the respiratory and cardiovascular systems due to the high incidence of concurrent thoracic trauma. Orthopedic examination should include palpation of the scapula and shoulder joint, noting pain, crepitus, and swelling. Neurological examination is essential to rule out nerve injury. Initial diagnostic imaging includes orthogonal radiographs of the scapula (lateral and craniocaudal views) and thorax to evaluate for concurrent injuries. If the fracture is articular or involves the glenoid, computed tomography (CT) is recommended for precise evaluation of fracture fragments and surgical planning. In cases of suspected neoplasia, thoracic radiographs and bone biopsy are indicated. Advanced imaging such as MRI may be used if soft tissue or nerve injury is suspected. Arthroscopy can be used to assess articular surface damage in minimally displaced fractures. The diagnostic workup should be systematic to avoid missing concurrent injuries.

Laboratory findings are generally non-specific but may reflect trauma and stress. Complete blood count may show leukocytosis due to stress or inflammation, and anemia if significant hemorrhage occurred. Serum biochemistry may reveal elevated creatine kinase (CK) and aspartate aminotransferase (AST) due to muscle trauma. Electrolytes may be altered if there is concurrent vomiting or shock. Coagulation panel (PT/aPTT) is recommended to assess for coagulopathy, especially if surgery is planned. Blood gas analysis may show metabolic acidosis due to shock. Inflammatory biomarkers such as C-reactive protein (CRP) and serum amyloid A (SAA) may be elevated. Synovial fluid analysis is not typically performed unless there is suspicion of septic arthritis, but if performed, it may show hemorrhagic or inflammatory changes in articular fractures.

Radiography is the primary imaging modality. Standard views include lateral and craniocaudal (or ventrodorsal with limb extended) projections of the scapula. Radiographs can reveal fracture location, displacement, and articular involvement. Stress views may be needed to assess instability. Thoracic radiographs are essential to rule out pneumothorax, pulmonary contusions, and rib fractures. CT is highly recommended for articular fractures, providing detailed 3D reconstructions and assessment of fragment displacement and joint congruity. CT is also useful for evaluating bone quality in cases of neoplasia. MRI is superior for evaluating soft tissue structures, including the suprascapular nerve and rotator cuff muscles, and may be indicated if nerve injury is suspected. Ultrasonography can be used to assess soft tissue injuries, but is less useful for bone evaluation. Arthroscopy is a minimally invasive technique that allows direct visualization of the articular surface and can be used for both diagnosis and treatment of intra-articular lesions.

Cytology and histopathology are primarily relevant when there is suspicion of neoplasia or infection. Fine-needle aspiration of a scapular mass may yield cells consistent with sarcoma (e.g., osteosarcoma, chondrosarcoma) or inflammation. Histopathology of a bone biopsy is the gold standard for diagnosing neoplasia, with features such as osteoid production, atypical mitotic figures, and tissue invasion. In cases of osteomyelitis, histopathology may show necrotic bone, inflammatory infiltrate, and bacterial colonies. Special stains (e.g., Gram stain) can help identify organisms. For articular fractures, synovial fluid analysis may show hemorrhagic or inflammatory changes, but is not diagnostic for fracture.

Treatment options include conservative management and surgical fixation. Conservative management is reserved for non-displaced, stable fractures of the scapular body or spine, and involves strict cage rest, analgesia, and gradual return to activity. However, surgical fixation is generally preferred for most scapular fractures to achieve anatomical reduction, stable fixation, and early return to function. Surgical techniques include: 1) Fracture of the body: open reduction and internal fixation using plates and screws (e.g., 2.0-2.7 mm plates) applied along the spine or lateral surface, or using cerclage wires for long oblique fractures. 2) Fracture of the neck: fixation with a plate or screws, with care to avoid the suprascapular nerve. 3) Articular fractures of the glenoid: require anatomical reduction and internal fixation using lag screws or small plates, and may require arthrotomy or arthroscopy. 4) Avulsion of the supraglenoid tubercle: reattachment using a lag screw or tension band wire. 5) Acromion fractures: fixation with a tension band or small plate. Postoperative management includes pain control, antibiotics, and restricted activity for 6-8 weeks. Physical rehabilitation is crucial to restore range of motion and muscle strength.

The prognosis for scapular fractures is generally good to excellent for non-articular fractures, with a high rate of union and return to function. Articular fractures have a guarded to good prognosis, depending on the degree of articular damage and the success of anatomical reduction. Complications include nonunion, malunion, implant failure, infection, and osteoarthritis. Negative prognostic indicators include severe comminution, open fractures, concurrent thoracic trauma, and delayed treatment. With appropriate surgical intervention, most animals regain acceptable limb function, though some may develop chronic lameness due to osteoarthritis.

Postoperative follow-up includes serial radiographs at 4, 6, 8, and 12 weeks to assess fracture healing. Suture removal is typically at 10-14 days. Restricted activity (leash walks only) is recommended for 6-8 weeks, with gradual return to normal activity over 3-4 months. Physical therapy, including passive range of motion exercises and swimming, is initiated early to prevent muscle atrophy and joint stiffness. Long-term monitoring for osteoarthritis is recommended, especially for articular fractures, with periodic radiographs and assessment of lameness. In cases of neoplasia, oncologic follow-up is necessary.

Pearls: 1) Always evaluate for concurrent thoracic trauma in scapular fractures. 2) Use CT for articular fractures to plan surgical approach. 3) Protect the suprascapular nerve during neck fracture repair. 4) Use a plate along the spine for body fractures for optimal stability. 5) For supraglenoid tubercle avulsion, use a tension band to counteract biceps pull. Pitfalls: 1) Missing concurrent injuries (pneumothorax) can be fatal. 2) Inadequate exposure can lead to iatrogenic nerve damage. 3) Failure to achieve anatomical reduction in articular fractures leads to osteoarthritis. 4) Overly aggressive postoperative activity can cause implant failure. 5) Inadequate pain management can lead to delayed healing and complications.

Perioperative antimicrobial prophylaxis: Cefazolin 22 mg/kg IV at induction and every 90 minutes during surgery. Postoperative antibiotics (e.g., amoxicillin-clavulanate 13.75 mg/kg PO q12h) for 7-10 days if open fracture or extensive soft tissue trauma. Analgesia: Preoperative opioids (e.g., hydromorphone 0.05-0.1 mg/kg IV or IM, or methadone 0.2-0.5 mg/kg IV) and postoperative continuation for 24-48 hours. NSAIDs (e.g., carprofen 2.2 mg/kg PO q12h, or meloxicam 0.1 mg/kg PO q24h) for 3-7 days, with caution in patients with renal or hepatic disease. Local anesthesia: Brachial plexus block with bupivacaine (1-2 mg/kg) or lidocaine (2 mg/kg) for intraoperative and postoperative analgesia. CRI of lidocaine (25-50 mcg/kg/min) and ketamine (0.5 mg/kg/hr) may be used for multimodal analgesia. Muscle relaxants: Methocarbamol 15-20 mg/kg PO q8h for muscle spasms. Chondroprotectants: Polysulfated glycosaminoglycan (Adequan) 4.4 mg/kg IM or SC twice weekly for 4 weeks, or oral glucosamine/chondroitin supplements. Gastroprotectants: Omeprazole 1 mg/kg PO q24h if NSAIDs are used. Adjust dosages based on organ function and concurrent medications.

Literature on scapular fractures is limited to retrospective case series and expert opinion. A study by Harasen (2002) reported that scapular fractures accounted for 1.5% of fractures in dogs and cats, with most being body fractures. Surgical fixation with plates and screws resulted in excellent outcomes in 85% of cases. Another study by Voss et al. (2004) emphasized the importance of CT for articular fractures and reported good to excellent outcomes with surgical repair. AO Vet principles recommend anatomical reduction and stable fixation for articular fractures to prevent osteoarthritis. Conservative management of non-displaced body fractures has been reported to have good outcomes, but surgical fixation is preferred for faster return to function. There is consensus that articular fractures have a higher risk of complications and require meticulous surgical technique. Overall, the evidence supports surgical intervention for most scapular fractures, with a favorable prognosis.