Fractures of the Patella
Fractures of the patella usually result from direct trauma, most commonly when a horse is kicked by another horse or hits a fixed obstacle while jumping. Prognosis depends on fracture conformation. Sagittal fractures of the medial pole of the patella are most common. These fractures are usually intra-articular and involve the attachment of the parapatellar fibrocartilage of the medial patellar ligament. Complete horizontal fractures are rare but considered serious injuries because of fragment distraction due to the massive pull of the extensor muscles. Complete sagittal fractures may be more amenable to internal fixation, because there is less distractive force.
Fracture of the patella usually results in marked lameness initially, with swelling and edema over the patella and effusion of the femoropatellar joint. In less severe or nonarticular fractures, lameness may improve within a few days. Diagnosis is confirmed by radiography. Standard radiographic projections of the stifle, together with a cranioproximal-craniodistal oblique projection of the patella, are used to determine fracture configuration.
Management options depend on fracture configuration. Horses with small, nondisplaced, nonarticular fractures may be treated conservatively with stable rest for 6–8 wk and have a good prognosis for return to athletic function. Articular fractures of the medial pole of the patella can be removed arthroscopically or via an arthrotomy and are also considered to have a good prognosis. Larger, mid-body sagittal or horizontal fractures require repair by internal fixation. These injuries carry a risk of catastrophic breakdown during anesthetic recovery but can have a favorable outcome.
Fractures of the Tibial Tuberosity
Fractures of the tibial tuberosity are not uncommon. There is little soft tissue covering this area, and fractures usually result from direct trauma. Fracture configuration may range from small fragments off the cranial proximal part of the tuberosity to large fractures of the whole of the tuberosity extending into the femorotibial joints. Fracture of the tibial tuberosity usually results in marked lameness initially with localized swelling and edema. Lameness will often improve within a few days. Diagnosis is confirmed by radiography.
Small and nondisplaced fractures may heal with conservative treatment. Stable rest for 6–8 wk is advised. During the first 2–3 wk, the horse should be prevented from lying down by tying or the use of slings to prevent fragment displacement. Larger intra-articular fractures should be repaired by internal fixation. Fractures generally have a good prognosis for return to athletic function if appropriately managed.
Fractures of the Femoral Condyles and Femoral Trochlear Ridges
Fracture of the femoral condyles is usually the result of direct trauma. Large, intra-articular, displaced fractures in adult horses are catastrophic and have a grave prognosis. However, traumatic fragmentation of the femoral condyles or trochlear ridges can also occur. Such injuries usually result in acute onset, moderate to severe lameness with joint effusion. Diagnosis is confirmed by radiography. Treatment involves surgical removal of the fracture fragments to prevent development of osteoarthritis. This is usually achieved arthroscopically but may require arthrotomy. The prognosis is usually considered to be good after surgery, so long as there is no significant concurrent soft-tissue damage.