Case 1: Comminuted P1 fracture in a 14-year-old warmblood mare

A 14-year-old Belgian warmblood mare weighing 520 kg was presented with a medical history of severe right forelimb lameness following an unwitnessed paddock injury. Radiographs confirmed a highly comminuted fracture of P1. A distal limb bandage had been applied in an attempt to stabilize the injury before transporting the mare.

Radiographic evaluation at the time of admission confirmed the highly comminuted fracture configuration and revealed considerable collapse of P1 with malalignment and overriding of the fracture fragments (Fig 3). Due to the highly unstable nature of the injury and the presence of multiple sharp fracture fragments, the immediate concern was the potential for skin penetration and conversion to an open fracture. Consequently, the mare was placed under general anesthesia to facilitate indirect fracture reduction through traction on the distal limb. Once alignment was confirmed radiographically, the distal limb was stabilized by application of a fiberglass cast extending distally from the proximal metacarpus and incorporating the hoof.

Following recovery from anesthesia, the mare was placed in intensive care for 24 hours to stabilize her physiological status before surgical fixation. Bridging plate fixation of the comminuted P1 fracture in conjunction with arthrodesis of the metacarpophalangeal and proximal interphalangeal joints was accomplished using an LCP DFP (11-holes). Prior to fixation,articular cartilage was debrided from the articulations using a 4.5 mm drill bit and curettes passed through stab incisions. The frontal plane fracture in the proximal aspect of P1 was reduced and stabilized with 5.5mm cortex screws placed in lag fashion from dorsal to palmar in a slightly distal to proximal orientation.

The plate was contoured to the desired 15 of dorsiflexion at the level of the fetlock joint to provide an appropriate joint angle (Fig 4a).Three, approximately 4 cm long dorsal midline incisions were performed through the skin and extensor tendon at the level of the proximal end of the plate, the metacarpophalangeal joint, and at the distal end of the plate overlying the proximal interphalangeal joint. Using a combination of sharp dissection and a large periosteal elevator, a tunnel was created between the bone and overlying soft tissues including the extensor tendon. The plate was inserted into the tunnel and appropriate plate positioning ,and cortical alignment were confirmed radiographically. A Push-Pull Reduction Device was placed through hole (A) in the head of the plate at the level of the proximal interphalangeal joint to compress the plate onto the dorsal cortices of the phalanges and maintain alignment of the proximal interphalangeal joint. Five 5.0 mm locking screws were inserted in the expanded head of the plate to purchase the distal aspect ofP1 and the proximal aspect of P2. To ensure plate-bone contact proximally, two 5.5 mm cortex screws were placed into the distal aspect of the metacarpus (plate shaft holes4 and 5). The remaining holes overlying the metacarpus were filled with 5.0 mm locking screws; where possible, 4.5 mm cortex screws were placed through the plate overlying large fragments of the P1. Finally, two 5.5 mm cortex screws were placed in lag fashion abaxial to the plate to engage the medial and lateral proximal sesamoid bones(Fig 5). Screws placed outside of the dorsal midline incisions were placed through additional stab incisions.

The incisions were closed routinely (Fig 4b).The distal limb was placed in a cast, and the patient was assisted in recovery. Surgery time, including casting, was 310 minutes.

The cast was changed 2 weeks postoperatively and removed 1 month following the repair. The distal limb was maintained in a Robert-Jones bandage for 1 additional month. Routine hoof care in conjunction with rocker shoes and silicone padding were initiated at the time of case removal. The mare made excellent progress postoperatively and was fully weight bearing on the repaired leg immediately. Radiographic evaluation 5 months postoperatively confirmed good fracture healing and progression of the arthrodesis(Fig 6). The mare was returned to paddock activity at this time and was fully functional with only mild mechanical lameness, as expected with arthrodesis of the metacarpophalangeal joint.

Case 2: Comminuted PI fracture in a 10-year-old warmblood gelding horse

A 10-year-old French warmblood gelding weighing 580 kg was presented a few hours after developing a severe left forelimb lameness following an unwitnessed paddock injury. Initial radiographs demonstrated a severely comminuted, minimally displaced fracture of P1 (Fig 7). The distal limb was immediately placed in a fiberglass cast by the referring veterinarian before transporting the horse, which prevented further displacement of the fragments.

The day following admission, the horse was placed under general anesthesia and bridging plate fracture fixation/arthrodesis was accomplished using an 11-hole LCP DFP as described in case 1. Surgery time was 315 minutes.

Postanesthetic myopathy complicated the patients recovery and necessitated intensive care immediately following surgery. He responded to supportive therapy and improved rapidly. In addition, his comfort level was excellent on his operated leg for the duration of hospitalization. At 3 months postoperatively, clinical evaluation revealed excellent weight bearing on the operated leg (Fig 8a), with mechanical lameness characteristic of horses with a fused metacarpophalangeal joint. The cosmetic appearance of the distal limb was excellent (Fig 8bc). Radiographic examination demonstrated excellent fracture healing with ongoing progress of the arthrodesis in both articulations (Fig 9). He was shoed with rocking shoes and silicone padding on both front feet to facilitate mobility and to provide hoof support.