
Thoracic trauma is uncommon in the horse, and because the thorax is well protected by the rib cage, when wounds do occur, they tend to be superficial. Nevertheless, certain aspects need to be considered when evaluating and treating thoracic trauma, and underestimating the depth or extensiveness of a thorax wound can have grave consequences.
The general approach of examining a thoracic trauma case is very comparable to examining any other trauma case. Everything starts with a good anamnesis, enquiring about the cause and time of trauma, onset of clinical symptoms, previous treatment, and known health conditions predating the trauma. It is worth paying extra attention to any signs of breathing difficulty or substantial blood loss. The focus of the clinical examination is the general condition of the horse. First, the general composure and breathing comfort are being evaluated from a distance. General physical parameters such as heart rate and rhythm, mucosal color and capillary refill time, and rectal temperature are routinely collected. If the general examination reveals a concern for a systemic problem caused by thoracal involvement, taking both an arterial and a venous blood sample may reveal more information. Horses with thoracal trauma that show signs of respiratory distress or shock need to be stabilized first, before the wound is taken care of.
If the horse does not show any signs of shock or respiratory distress, the wound needs to be thoroughly explored for penetration of the thoracal cavity, presence of foreign objects, rib fractures, or hemothorax. Tissue layers may shift relative to each other, hiding the actual extent of the lesion when only a superficial exploration is carried out. Lesions that affect only the skin and muscle layers can often be cleaned, debrided, and sutured in the standing horse. Special attention needs to be paid to facilitating wound drainage, and in many cases some creativity is needed to avoid extensive tension on the wound edges, which would result in dehiscence. Oftentimes, skin flaps are traumatized, and/or the blood supply to the skin is damaged, resulting in skin flaps becoming necrotic post-surgery, but it is almost always worth it to try and save as much skin as possible. Nevertheless, wounds with extensive skin loss can heal by second intention surprisingly well on the thorax.
When the wound extends into the pleural space, the vacuum keeping the lungs from collapsing is lost, and a pneumothorax develops. Because of an imperfect separation by the mediastinum, a bilateral pneumothorax can even develop when only one hemithorax is affected by the causative lesion. Even when a wound does not penetrate into the thoracal cavity, secondary pneumothorax can still develop as a result of massive emphysema. Diagnosis of pneumothorax is based on clinical symptoms, and can be confirmed on both X-ray and ultrasound, with the latter being significantly more sensitive in a recent study (Partlow et al., 2017). A minimal pneumothorax is often well tolerated, and the focus can shift to wound debridement and closure. In case of severe respiratory distress, the wound needs to be packed first, and an emergency thoracocentesis needs to be done to restore breathing capacity, prior to wound care. Prognosis for survival after penetrating thoracal trauma varies, but is reported to be fair (Laverty et al., 1996; Boy et al., 2000).
Rib fractures can be suspected on careful palpation of the wound, and confirmed by X-ray and ultrasound. In addition, scintigraphy was demonstrated to be the most sensitive method of detection (Hall et al., 2023). Closed fractures usually do not need surgery and can heal by second intention. Open fractures are contaminated by definition, and surgery consisting of debridement of the fracture fragments, or sectional ostectomy, if indicated. In foals, the risk of bone fragments from a fracture penetrating vital structures in the thorax is higher, and surgical repair is more often indicated than in adult horses (Bellezzo et al., 2004). Prognosis is excellent in adult horses (Hall et al., 2023), and somewhat more reserved in foals (Bellezzo et al., 2004; Downs et al. 2011; Williams et al., 2017).
Hemothorax is a possible complication of thoracal trauma and causes clinical symptoms similar to those caused by pneumothorax. Hemothorax can be suspected on ultrasound, and confirmed by thoracocentesis. The first focus should be directed stopping the bleeding. To restore the pleural vacuum, a thorax drain can be placed.
In some cases, a penetrating trauma can extend through the diaphragm into the abdominal cavity, creating a diaphragmatic hernia. Diagnosis consists of palpation, ultrasound, and/or thoracoscopy. Repairing a diaphragmatic tear is often difficult and can be attempted through a thoracal or abdominal approach, with the aid of thoracoscopy or laparoscopy if needed. If caused by a penetrating trauma, the abdominal cavity should be approached through a classic midline incision as well, to check the abdominal organs for damage, and to lavage the abdominal cavity.
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