Introduction: An 8yo MN German Shepherd named Mutley presented with trauma of unknown origin. He had sustained a RHS comminuted calcaneal fracture and Type IV Central tarsal bone fracture. He was stable otherwise. Apart from the tarsal fracture, orthopaedic and neurological examinations were normal.
Radiographic Findings: Mutley had a comminuted calcaneal fracture with a longitudinal fissure. He also had a type IV central tarsal bone fracture/luxation.
Operative Management: Mutley was anaesthetized with Propofol and maintained on Isoflurane. A medial approach to the central tarsal bone was made. A 3.5mm cortical lag screw was placed from medial to lateral and a 2.7mm cortical lag screw was placed from dorsal to plantar.
After wound closure a separate longer lateral skin incision was made to the calcaneus. Independent calcaneal lag screws were placed from plantar to dorsal and a 2.7mm 10 hole DCP was placed in neutral fashion laterally.
A cancellous bone graft was placed from the ipsilateral ilium using an acetabular reamer. Closure was routine with releasing skin incisions for tension.
To protect the repair, a unilateral, uniplanar, four pin positive profile SK external fixator was placed laterally.
Analgesia: Mutley was given Buprenorphine and carprofen postoperatively. His limb was iced and the ESF frame was padded and temporarily bandaged.
Outcome: Mutley was using his limb quite well within a week of surgery, and was fully weight bearing within 14 days. He was placed on Clavulox 500mg BID for 7 days, and has made an excellent recovery. He had repeat x-rays at 8 weeks, and his ESF was removed at that stage. He is now walking and exercising well and doesn’t appear to have any lameness.
Discussion : Central tarsal bone fractures can occur in any breed but are most commonly seen in the RHS hock of greyhounds during racing. Type IV fractures are the most common and involve a transverse mid-body fracture and a dorsal slab fracture, slicing the bone into four. They are often accompanied by a comminuted calcaneal fracture.
It is essential to provide anatomical reduction and fixation of the central tarsal bone with dual lag screw internal fixation. Screw size and positioning is critical in order to avoid fracturing the bone. We chose a 3.5mm cortical and 2.7mm cortical screws for their size and strength. The calcaneus of the dog is extremely dense and strong and holds implants really well. A cancellous bone graft aids in osteoinduction and osteogenesis, improving rates of healing. Because the bone plate crosses the tarsometatarsal joint, I used a high speed neurosurgical drill to remove the cartilage from this joint and resulting in arthrodesis. This joint contributes minimally to hock range of motion and the extra stability again aids healing.
A 2.7mm DCP was chosen due to size limitation. Custom made arthrodesis plates are often also employed.
We elected to also place a temporary external fixator to protect the internal fixation.
The SK IMEX external fixator has carbon based connecting rods which are radiolucent, lightweight and very strong. Positive profile pins have their threads laid onto the shaft and are stronger with higher pullout strengths.
The SK clamps are designed to allow additional pins to be added after frame construction, and the positive pins can be passed through the clamp, making placement easier.
Complex hock fractures and luxations are commonly seen, and very good results can be achieved in most cases, by attention to detail, and anatomic reconstruction.
