Details on appropriate preparation and draping for this procedure can be found here.
The animal is positioned on the surgery table either in dorsal recumbence or in lateral recumbency with the injured proximal sesamoid bone up.
Dorsal recumbency allows the insertion of the arthroscope from the contralateral palmar pouch to facilitate better visualization and an unfretted region for instrument insertion and manipulation during fragment removal.
In lateral recumbency the arthroscope is inserted through the proximal most aspect of the palmar pouch, whereas the instruments are inserted through a separate incision at the level of the fracture plane.
3. Surgical technique
The arthroscope is inserted and the fracture configuration inspected.
The fracture site is explored with a probe.
Small fragment removal
Small fragments can be grasped with a Ferris-Smith rongeur, twisted off their attachment and removed in one piece.
The fracture bed is curetted leaving a smooth surface.
Large fragment removal
Larger fragments are freed from their attachments of the distal sesamoidean ligaments with the help of sharp instruments such a scalpels, special, curved small osteotomes or sharp periosteal elevators. Loosening occurs proximally, ...
Once freed up the fragment is grabbed with Ferris-Smith rongeurs and rotated to free up the last attachments and finally removed as a whole. Occasionally the fragment has to be split in half to remove it.
Dependent upon the size of the fragment the instrument incision may have to be enlarged for fragment removal.
Another option is the use of an arthrobur to grind down the fragment and remove the debris via suction.
A combination of these techniques is also possible and larger fragments can be split with an osteotome and removed fragment by fragment.
Debridement and inspection of the fracture bed
Once the fragment is removed the fracture bed is inspected and thoroughly curetted. Any remaining debris or any small fragments are removed. Special attention is given to the ligamentous attachment remains, which are checked for osseous remains attached to them.
It is advisable to take intraoperative radiographs to assure that the entire fragment is removed. Intraoperative fluoroscopy represent another option.
Small ligamentous stands are removed with a motorized shaver.
Lavage and closure
The joint is thoroughly lavaged, the excess fluid removed from the joint, the arthroscope removed and the incisions closed using routine technique. A sterile pressure bandage is applied to the limb with the horse still on the table.
4. Case example
Left: lateromedial radiographic view of a minimally displaced apex fracture. Right: 3-month followu p lateromedial radiographic view of the same fracture. Fracture healing is progressing very nicely and the lameness has subsided.
Intraoperative arthroscopic view of the apex fracture shown above. The fracture is easily recognizable.
Intraoperative arthroscopic view of the same proximal sesamoid as shown above following apex fragment removal. The fracture surface of the parent bone is easily visible.
A splint-pressure bandage is applied prior to recovery from anesthesia. In most cases the splint can be left off after a couple of days.
For abaxial fractures, only a pressure bandage is applied.
Extended stall rest and a gradual return to exercise will typically result in a functional fibrous union, however soundness is dependent upon the degree of osteoarthritis that develops. Generally stall rest for 90 days followed by hand walking for 30-60 days is sufficient prior to free exercise.
Healing can be monitored radiographically and ultrasonographically. In some cases new bone formation at the fracture site may be noticed after some weeks, which usually do not cause any problems. The potential for return to the previous activities has to be judged cautiously.