Orthopedic surgery in standing horses

Introduction

Although it is feasible to perform many orthopedic procedures in the standing horse, consideration should always be given to the attendant benefits and risks of such an approach. Standing surgery has the primary benefits of eliminating the expenses of general anesthesia and the risks associated with recovery from recumbency. In addition, some procedures such as medial patellar desmotomy or lateral digital extensor tenectomy may be technically a bit easier with the horse bearing weight on the limb. In virtually every case, the surgeon’s comfort is significantly diminished when doing surgery in the standing horse but with proper chemical and physical restraint as well as appropriate local anesthesia, there should be little serious risk to the surgeon. A major disadvantage of standing surgery is maintenance of a sterile surgical field; it can be difficult to drape the surgical area and prevent contamination if the patient moves. Visibility of anatomical structures is usually more difficult in the standing horse because of poorer illumination, inadequate retraction and problems with hemorrhage. In particular, some procedures in the distal limb will bleed more in the standing horse due to simple gravitational reasons. In summary, orthopedic procedures are generally more difficult to perform in the standing horse and the surgeon should be experienced and confident in doing the procedure in a recumbent patient before attempting it in the standing horse

Specific indications for Standing Orthopedic Surgery

Stringhalt and upward fixation of the patella are well described and the surgical procedures used to treat them have remained essentially unchanged for decades. Use of lateral digital extensor tenotomy/tenectomy for stringhalt results in inconsistent long term improvement and is frequently unsuccessful in managing the more severely affected horses. Medial patellar desmotomy is still necessary to treat the severely “locked” upward fixation but evidence is strong that the procedure may lead to degenerative changes in the joint, specifically involving the distal pole of the patella. There are numerous good descriptions of these standing procedures in the literature as well as for distal splint bone amputation and palmar (plantar) digital neurectomy.
Annular ligament desmotomy is indicated in horses with constriction of the flexor tendons over the palmar/plantar aspect of the fetlock. The constriction can be due to either tendonitis and enlargement of the tendon(s) themselves or it can be associated with primary thickening of the annular ligament. Ultrasonography is the definitive diagnostic tool. The surgery is often indicated in the hind limb(s) of middle aged to older jumpers and dressage horses.
Osteostixis (transcortical drilling) is a common treatment for dorsal cortical fractures (“stress”, “fatigue” or “saucer” fractures) of the third metacarpal bone in Thoroughbred racehorses. The rationale is the recruitment of healing elements from the medullary cavity into the fracture site as well as a possible induction of the proposed “regional acceleratory phenomenon” believed to operate in bone. [5, 6] In the author’s opinion, osteostixis alone (without a bone screw) is adequate to treat most of these fractures. Many such fractures will heal with rest alone but mid diaphyseal cracks without evidence of endosteal involvement or periosteal response often are very slow to heal and are appropriate candidates for surgery. Horses with recurrence of dorsal cortical fractures also are good candidates for the procedure.

Sequestrectomy is often a simple procedure that can be done standing, even if it involves a bone more proximally located in the limb, head or axial skeleton. A good candidate for standing debridement is one in which the lesion is not adjacent to sensitive neurovascular structures and retraction and elevation of tissues is minimal. There is a potential advantage in standing debridement of very large sequestra from the appendicular skeleton because the risk of fracture during recovery is eliminated.
Deep digital flexor tenotomy for the treatment of laminitis is frequently done with the horse standing because of the poor overall condition of the patient or concomitant orthopedic problems. Although it can be done in either the mid-metacarpal region or the mid-pastern region in the standing horse, the mid-metacarpal approach is definitely easier. Inferior check desmotomy (transection of the accessory ligament of the deep digital flexor tendon) is usually done under general anesthesia for the treatment of flexural deformities. However, both inferior check desmotomy and deep digital flexor tenotomy can be done standing under ultrasonographic guidance, however.

[...]