1 Principles topenlarge
Number and direction of screws
Interfragmentary compression is achieved through insertion of at least one screw placed in lag technique. Ideally, a second screw should be inserted to provide additional compression and rotational stability.
In abaxial articular fractures there is usually not enough space for two 4.5 mm screws. However, it may be possible to insert one 4.5 mm and one 3.5 mm screw or a Kirschner wire.
Insertion of two 3.5 mm screws is another option though less stable.
The screws can be inserted in a dorsopalmar/plantar direction or in a palmaro/plantarodorsal direction (left). However, if an attempt is made to use two interfragmentary screws, they should be inserted in dorsopalmar/plantar direction
Note: Displaced fractures are usually reduced when non-weight bearing.
Availability of pre- and intraoperative advanced diagnostic imaging techniques are a prerequisite for internal fixation of the fracture by means of screws inserted in lag technique. If these techniques are not available, conservative treatment should be selected.
2 Determination of screw position, orientation and length topenlarge
Entry and exit point
The entry and exit point of the future screw is marked on the hoof wall with a small barium bleb.
The CT-scan is performed and the screw axis determined and compared with the barium blebs. If the blebs are not in the correct location, they are changed in relation to the determined screw axis. The old blebs are removed.
The foot is re-scanned and the above procedure repeated until the blebs are in line with the screw axis.
The entry and exit point for a second screw are marked using the technique just described.
The foot is prepared for aseptic surgery.
The distance from the surface of the hoof to the fracture plane is determined.
3 Screw insertion topenlarge
Preparing the glide hole
The aiming device with the 4.5 mm drill sleeve is applied over the two blebs and the 4.5 mm glide hole is drilled to the predetermined depth.
The hoof is re-scanned and entry of the glide hole across the fracture plane (red arrow) is checked. If necessary, the glide hole is extended until it reaches the fracture plane.
The distal interphalangeal joint is distended and the arthroscope inserted using routine technique through a stab incision located 2 cm proximal to the coronary band and 2 cm lateral to the sagittal plane.
The joint is explored and the fracture identified and, if needed, anatomically reduced through manipulations with the 3.2 mm drill guide inserted into the glide hole after loosening the aiming device. Once the fracture is reduced the aiming device is tightened again.
Preparing the thread hole
The thread hole is drilled across the fragment.
If the drill bit for the thread hole is too short to reach the end of the bone, the aiming device is removed, the hole across the hoof wall expanded with a 10 mm drill bit. Reapplication of the aiming device is optional because the glide hole is in place and concentric completion of drilling the thread hole can be accomplished by inserting the 3.2 mm drill guide into the glide hole.
The threads are cut with the 4.5 mm tap guided through its corresponding sleeve.
Note: This step is out of routine screw insertion sequence.
An 8-10 mm hole is drilled across the hoof wall along the glide hole to the surface of the distal phalanx.
A countersink depression is prepared in the surface of the distal phalanx.
The prepared hole is thoroughly flushed with a bulb syringe to remove debris from tapping and enlarging the hole in the hoof wall.
The screw of predetermined length is inserted and tightened.
Compression of the fracture is observed arthroscopically.
A second 3.5 mm or 4.5 mm screw is inserted using the technique just described.
4 Closure of the hoof wall topenlarge
Filling the holes
A small portion of a gentamycin-impregnated collagen sponge is inserted in each hole to fill the space between the surface of the distal phalanx and the hoof wall.
The rest of the hole is filled with antibiotic-impregnated polymethylmethacrylate (PMMA). The edges are sealed with cyanoacrylate glue. If desired a Kevlar® strip can be glued over the top followed by non-adhesive tape covered.
An alternate techniques involves the insertion of artificial hoof resin.
The surface of the artificial hoof resin plugs are shaped to conform to the hoof surface.
Application of artificial hoof pad
The holes are covered by an additional artificial hoof pad that extends over the immediate hoof surface.
The patch is pressed onto the hoof wall with tightly applied wrapping tape around the entire hoof circumference and left hardening.
After 5-10 minutes the wrapping tape is removed and the surface of the patch adjusted as needed.
The surgical site can be covered by non-elastic tape.