The repair can be carried out with Dynamic Compression Plates (DCPs), Limited Contact Dynamic Compression Plates (LC-DCPs), or Locking Compression Plates (LCPs), among which the LCPs are presently the first choice. Dependent upon the size of the animal and the fracture configuration, either 2 broad plates or one broad and one narrow plate may be applied.
The plates are attached to the bone either with cortex- or locking head screws; the latter only in the LCPs. Dependent upon the size and/or age of the animal either 3.5 mm (in ponies and small foals), 4.5 mm or 5.5mm cortex screws are used. Usually cancellous screws are avoided. 3.5 mm cortex screws can be used in lag fashion even in adult animals to initially repair the fracture. This is routinely followed by the application of larger plates.
The fracture is anatomically reduced and repaired with one or two plates spanning the entire bone and applied at 90° relative to each other (left). In small ponies, some foals and selective cases of adult horses only one plate may be selected (right). The major problem in these fractures is to achieve adequate purchase in the distal/proximal metaphyseal fragment to allow immediate weight bearing. Special plates systems such as the DCS system are ideal for such situation because the barrel of the plate, with an outside diameter of 25 mm that is angled 95° relative to the plate is inserted into the metaphyseal fragment. Through the barrel a large screw with long shaft (8 mm diameter) and a threaded portion at the end (25mm long and 25mm diameter) is inserted through the barrel providing superior holding power within the small diaphyseal fragment.
Alternate possibilities are any of the human condylar plate, which either are stronger (left) or allow the placement of multiple screws in a widened area of one plate end. Occasionally even an adjacent row of bones may be used to achieve additional purchase. The distal row of carpal/tarsal bones lend themselves for this techniques because they form non-moving joints with the proximal McIII/MtIII respectively. It is very important to insert some interfragmentary screws to assure the not only the plate(s) bridge the fracture. Care must be taken in foals to avoid bridging the distal physis of the bone.
A proximal metaphyseal fracture is repaired using the same principles as a distal metaphyseal fracture. Some adjustments may be necessary dependent upon the fracture configuration.
In selected cases of proximal metaphyseal fractures, the distal row of carpal/tarsal bones can be included in the fixation because these joints do, for practical purposes, not move. This allows the insertion of additional screws into the distal row of carpal/tarsal bones associated with a functional arthrodesis of the carpometacarpal/tarsometatarsal joint. Because of the additional purchase of screws it may be possible to only use one (special) plate for the fixation in association with full limb external coaptation for a prolonged period of time.
5. Skin closure
The longitudinally split common/long digital extensor tendon is sutured with a simple continuous suture pattern of a 2-O monofilament synthetic absorbable suture material. The subcutaneous tissues are subsequently closed in identical fashion as the tendon and the skin is closed with skin staples or simple interrupted monofilament nylon sutures.
6. Regional intravenous perfusion
At the end of the procedure it is advisable to perform regional intravenous perfusion with broad spectrum antibiotic of the surgeon’s choice. A tourniquet is applied at the distal third of the radius/tibia followed by insertion of an indwelling catheter into the corresponding vein distal to the tourniquet (Cephalic vein in the forelimb, saphenous vein in the hind limb).
About 40 ml of blood is withdrawn from the vein followed by by slow injection of the same amount if antibiotic. The antibiotic is maintained in the fracture region for 20 to 30 minutes.
7. Recovery from anesthesia
The animal is covered with a tight full-limb bandage and splint. Application of a full limb cast for recovery from anesthesia is an alternate option especially in proximal metaphyseal fractures.
The patient is kept in a box stall for one month. The splint bandage is changed at 4-day intervals. At the end of the first month, provided the patient uses the limb properly and and complication arose, the splint can be removed and a half limb bandage applied to the limb. At that time, some daily hand walking is allowed for one additional month.
Follow up radiographs are taken 2 months postoperatively. The remaining postoperative period is managed dependent upon the result of the follow up radiographs.
The management of the remaining reconvalescent period depends upon the progression of fracture healing assessed using the 2 month follow up radiographs. Barring any complications the patient can be turned out into a small paddock and assume light exercise at 3 months postoperatively.
More information about implant removal can be found here.