The fracture fragments are brought into reduction with pointed reduction forceps. When necessary, larger fragments are reduced and attached with a cortex screw in lag fashion across the fracture line outside the area where the plate will be placed to maintain reduction.
Fracture gaps that are not amenable to lag screw fixation can often be reduced using the dynamic compression principles of the plate, or when a very large gap exists, using the Articulated Tension Device (ATD). In some of these cases an interfragmentary cortex screw can be inserted through a plate hole.
Typically a 10-14 hole narrow plate is contoured to fit the caudal cortex of the olecranon/ulna extending distally from the level of the scar of the olecranon physis spanning the fracture. To ensure adequate purchase, 4-5 screws are placed in the proximal and distal fracture segments each. LCP, LC-DCP or DCP have all been used successfully in this location. A soft aluminum template is used to aid in contouring of the plate. Because of the anatomy of the proximal olecranon it may be necessary to slightly torque the plate at its proximal end to fit the bone.
The plate is applied to the bone with one screw through the proximal and another screw through the distal aspect of the plate to assure that the plate is located along its entire length on the narrow caudal edge of the olecranon. One or both of these screws can be placed in the load position to effect dynamic compression on the fracture if desired. An intraoperative radiograph should be taken at this time to confirm reduction of the fracture, and plate contour.
If possible, a cortex screw is placed in lag fashion through the plate across the fracture line or fracture lines in the case of comminution to further compress the fracture.
Placement of the remainig screws
The remaining screws are inserted with the cortex screws being placed prior to insertion of any locking head screws when a locking compression plate is used. The proximal screws should gain purchase in the dense cortical bone of the cranial metaphysis of the olecranon. Take care that the screws adjacent to the trochlear notch do not penetrate into the joint.
Engaging the radius
In horses over a year of age the screws distal to the articular surface of the radius should engage the caudal cortex of the radius. It is not necessary to engage the cranial cortex of the radius, which could predispose to a radial fracture. 1-2 locking head screws are usually placed adjacent to the fracture in each fracture fragment and one at or near the ends of the plate.
Pitfall: Anatomically the ulna is superimposed over the lateral aspect of the radius distally. It is important to direct the distal plate screws medially, into the medullary cavity of the radius, to avoid the lateral cortex of the radius. Care must be taken to avoid drilling and placing screws into the lateral cortex of the radius, which may weaken the radius and predispose it to catastrophic fracture. For this reason, it is usually not possible to apply locking screws for fixation in the most distal aspect of the locking plate.
Laterlal-medial radiograph shwong the fracture at distal end of the plate.
Photograph of the specimen showing the second screw from distal end position in the lateral cortex.
End view of the previous picture.
Antibiotic impregnated polymethylmethacrylate beads are placed along the plate prior to surgical wound closure. The wounds are closed routinely and are covered and protected with a bandage until the skin staples or sutures are removed. Some surgeons prefer to use suction drains, but the author does not routinely use them.
5. Overview of rehabilitation
The patient is confined to stall rest for 90 days. The first 45 days only a limited amount of hand-grazing is advised, for the next 45 days a progressive program of hand-walking exercises is advised. Follow up radiographs are taken at 90 days. If healing progresses and no complications occur gradual transition to free paddock exercise is allowed. Usually after 1-2 months of paddock exercise they are re-introduced to normal training and performance activities.
Plate removal after the ulna fracture has healed is strongly discouraged because of potential re-fracture of the ulna during recovery along empty screw holes. Therefore, whenever possible plate removal is performed in the sedated, standing horse. For more information please see additional material "Implant removal and complications".
Occasionally specific situations (explicit wish of the owner, etc.) may lead to implant removal and rarely selected screws have to be removed but the plate is left in place.
The only real indication of implant removal is chronic, non-resolving infection. More information about plate removal can be found here.
Chronic infection is usually diagnosed because intermittent lameness and subsequent opening of a fistulous tract at the surgical wound draining purulent material. Through cleaning of the fistulous tract and repeated flushing with physiologic saline and mild antiseptica the tract eventually clears up and the skin closes. As soon as the tract opens lameness disappears. With time, however, another pocket containing purulent material accumulates at the same spot associated with increasing lameness and the whole cycle repeats itself.