Splinting the limb in extension will allow the foal to bear weight on the affected limb. A well-padded bandage, extending from the ground to the proximal radius, with a rigid splint affixed to the caudal aspect of the bandage is recommended. This is advisable for transport as well as prior to surgery to reduce swelling, patient fatigue and distress.
Strength of fixation
It is important to obtain maximum purchase in the proximal fracture segment by
contouring and affixing the plate to allow purchase of 3 short screws in the apophysis of the olecranon and
placing 2-3 cortex screws (5.5 mm if possible) in lag fashion through the plate across the fracture line into the dense cortical bone of the cranial metaphysis.
Note: The latter are the most important screws for the fixation, therefore care must be taken to engage the entire dorsal fragment width.
Transfixation of the radius
Care must be taken to avoid transfixing the radius and the ulna with the distal plate screws in growing foals (less than 7 months of age) to avoid disrupting elbow congruence as the foal grows.
If there is comminution at the anconeal process the fragment is removed at this point. The fracture is distracted by flexing the limb allowing the surgeon to digitally inspect the joint through a separate stab incision over the fragment and in most cases palpate and remove the loose fragment(s).
The apophysis of the olecranon is grasped with pointed reduction forceps seated medially and laterally, and with the limb extended and distal traction applied to the pointed reduction forceps, the fracture is brought into reduction.
The fracture is held in reduction by either an assistant holding the reduction forceps or by repositioning the forceps with one point on the cranial metaphysis of the fragment and one on or near the caudal cortex of the parent olecranon.
Plate selection and preparation
A soft aluminum template of appropriate length is contoured for application over the proximal olecranon extending distally onto the ulna.
Usually an 8-10 hole narrow plate is appropriate. LCP, LC-DCP or DCP have all been used successfully in this location. The plate is bent to match the previously contoured aluminum template.
It is very important to place the plate such that it is located along the entire length on the narrow caudal edge of the olecranon. Also it is better to err slightly to the lateral side than to the medial side. If the plate comes to lie more to the medial side it will be impossible to insert the most important screws into the entire width of the cranial fragment.
Once the fracture is held in reduction, the plate is applied initially with one short cortex screw in the apophysis of the olecranon and another cortex screw distal to the fracture. It is very important that the plate is positioned correctly. Depending on the degree of fracture reduction, one or both of these screws are placed in the “load” position of the plate to allow for dynamic compression of the fracture. It should be noted that as compression is applied, the cranial aspect of the fracture at the articular surface may become malaligned. If this is the case, the metaphyseal component of the fracture and articular surface should be maintained in alignment by placing the lag screws through the plate prior to final tightening of the previously placed plate screws.
If possible, an intraoperative lateral to medial radiograph is taken to assess implant position and fracture reduction.
Placement of lag screws through the plate
Providing the fracture is adequately realigned one or two plate holes that are immediately distal to the physis are prepared for the insertion of 5.5 mm cortex screws placed using lag technique across the metaphyseal fracture and engaging the dense cortical bone of the cranial metaphysis. For the preparation of the two glide holes axial compression provided by tightening of the initial two plate screws should be loosened to facilitate appreciation of fracture line penetration with the drill bit for the glide hole. With tightening of these screws, the anconeal process and metaphyseal fracture lines are reduced and compressed.
Note: Care must be taken to ensure that these screws are directed into the cranial cortex of the metaphysis. Because the medial aspect of the olecranon is slightly concave the direction of drilling must be monitored carefully to prevent these screws from exiting the metaphysis on it’s medial aspect. If these holes are misdirected, the screws may exit the medial cortex and fail to purchase the cranial metaphysis which will substantially weaken the fixation. In addition, screws protruding from the medial cortex may impinge on the medical epicondyle of the humerus during extension of the elbow and cause lameness.
To achieve this a Steinman pin is carefully inserted along the medial edge of the olecranon in cranial direction to serve as orientation guide for the drill bit. The 5.5 mm drill bit and its corresponding drill guide are oriented parallel to this pin in all directions and the glide hole is prepared into the fracture line. The same procedures is repeated through the second and if deemed necessary through the third plate hole destined to accept a cortex screw in lag fashion across the cranial fracture line.
After reapplying axial compression to realign the fragment into anatomic reduction, the thread hole of the first screw is prepared, tapped and the screw inserted and tightened. The same procedure is subsequently repeated with the second and if deemed necessary with the third screw inserted in lag fashion.
Placing the remainder of the screws
The remainder of the screws are then inserted through the appropriate plate holes. If LCP implants and instrumentation are available, all cortex screws are placed prior to insertion of any locking head screws. At least 1-2 locking head screws are placed on either side of the fracture, more specifically on the proximal most aspect of the olecranon and distal to the 5.5 mm cortex screws placed in lag fashion.
Pitfall: Care must be taken to avoid screw penetration into the caudal radius. If these screws engage the radius in individuals less than 7 months of age this may lead to incongruity of the elbow joint. This is caused by the inability of the transfixed ulna to slide proximally to maintain elbow congruity as the proximal radius elongates with growth.
Ensure that the screws adjacent to the trochlear notch of the olecranon do not penetrate cranially into the articulation.
Postoperative radiographs are taken to confirm the final configuration of the fixation. Fixation with a LCP on the left and with a DCP on the right.
Immediate postoperative radiograph and 1-month follow up radiograph of the fracture repair in an adult horse. The fracture was initially reduced and repaired with cortex screw in lag fashion, followed by application of a LCP with one interfragmentary cortex – and one locking head screw.
Antibiotic impregnated polymethylmethacrylate beads are placed long 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.
7. Overview of rehabilitation
The patient is kept in stall rest for a minimum of 60 days. The first 30 days hand-grazing only is advised, followed by 30 days of hand-walking. Follow up radiographs are taken at 60 days. If healing appears to be progressing without complications the patient is gradually transitioned to free paddock exercise. The implants are left in place unless complications develop.
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.