Improved Visibility

Improved visibility during arthroscopic examination allows for evaluation of most of the joint compared with the limited view provided by arthrotomy. Even long arthrotomy incisions rarely provide added visibility because overlying capsule, retinaculum, and sheaths make retraction difficult. During arthroscopic examination, cartilage at locations distant to the primary lesion site, synovium, and intraarticular soft tissue structures such as ligaments can be examined. For example, newly described disease conditions involving intercarpal ligaments were not known before arthroscopic examination existed.

Reduced Trauma and Morbidity

Arthroscopic examination is less traumatic and causes less morbidity. Arthroscopic examination allows surgery to be performed through small incisions and requires less surgical exposure and damage to overlying soft tissues, upholding a time-honored principle of limiting trauma. Little pain is observed in horses after arthroscopic surgery compared with arthrotomy, and many horses appear to ambulate normally. However, in an unblinded study of horses after arthroscopy under general anesthesia, horses showed mild but significant increases in discomfort compared with pain-free controls.² Complications such as wound dehiscence and seroma formation are minimal. Horses often show pronounced lameness for several days after arthrotomy. After arthroscopic examination and surgery, owners and trainers expect horses to return to full work soon after surgery, an idea that is fueled by widespread reports of human athletes returning to professional sports quickly after arthroscopic surgery. A general misunderstanding is that incision size is the limiting factor. Although arthrotomy does cause short-lived lameness after surgery, the fear that it will delay onset of training is unfounded because the underlying lesion dictates recovery time. Although not recommended, horses with mild conditions such as osteochondritis dissecans, effusion but no lameness, and those that receive prophylactic arthroscopic surgery can resume training a few weeks after arthroscopic examination or arthroscopic surgery. Arthroscopic surgery can be performed within weeks before a sale, and if hair was not clipped, surgical sites are barely noticeable.

Better Cosmetic Results

Improved cosmesis is a definite advantage. Small incisions cause less fibrous tissue formation, and incisions are difficult to identify 2 to 3 months after surgery. Generally the instrument portal (incision), the site through which the arthroscopic instruments are passed and lavage is performed, suffers more trauma than does the arthroscopic portal, and swelling, reactions, and fibrous tissue production are more common.

Earlier Functional Capability

Earlier return to function was once believed to be an advantage of arthroscopic surgery. However, incision size has little to do with lameness except within the first few weeks after surgery. Lameness observed in horses returned to work 4 to 6 weeks after arthroscopic surgery for substantial articular lesions has nothing to do with incision size. When horses undergoing arthroscopic surgery were given only a brief rest, results were unsatisfactory. Incisions heal from side to side, not end to end, and incision size has no effect on articular healing. Lesions must heal as completely as possible before full work can begin—a process that often takes several months. Type and location of lesions are important because horses with osteochondritis dissecans not involving weight-bearing surfaces can start training within 2 to 3 weeks of surgery, if necessary, whereas those with lesions in critical sites, such as the typical carpal osteochondral fragment, must be given 3 to 4 months of rest.

More Versatility

Improved versatility is a definite advantage because joints considered inaccessible, such as the coxofemoral joint, can be evaluated. Techniques such as repair of third carpal slab fractures, distal third metatarsal (MtIII) or third metacarpal (McIII) fractures, fractures in other joints, and resurfacing techniques can be done using arthroscopic surgery.

Fewer Complications

Arthroscopic surgery results in fewer complications. Arthrotomy of the scapulohumeral, femorotibial, femoropatellar, cubital, and tarsocrural joints has been associated with dehiscence, seroma formation, and infection, but arthroscopic surgery of these joints is safe.

Expensive Instrumentation

Expense of surgical instrumentation is a disadvantage because start-up costs are high, but basic instrumentation is no more costly than routine surgical instruments. Although arthroscopic surgery can be done without video equipment, video arthroscopy is valuable for archiving images. It is much more comfortable than direct-view arthroscopy (looking directly through the eyepiece) because surgery is performed using a comfortably positioned monitor. It allows the procedure to be viewed by others and is valuable in maintaining aseptic technique because breaks in technique often occur during direct-view arthroscopic surgery.

Lack of Surgical Experience

Experience necessary to learn arthroscopic surgery is a disadvantage. Arthroscopic surgery requires skill in stereotactic techniques and orienting and operating without looking at the surgical site, and surgeons must be able to use instruments properly and safely while looking at a monitor. Preoperative planning must be done to ensure that the horse is positioned properly on the operating table and the surgeon has ready access for triangulation. Poor technique may result in iatrogenic damage or extravasation of large amounts of lavage fluid that can severely compromise distention of the joint capsule and thus ability to see adequately within the joint. Experience cannot be gained by simply attending a weekend course but rather by working long hours with cadaver specimens and observing experienced surgeons. Initially arthroscopic surgery can be time consuming until experience is gained, but with experience arthroscopic surgery is faster than arthrotomy.

Equipment Problems

Equipment failures can be a disadvantage, and because arthroscopic examination depends on electricity, a generator should always be available. Instruments are not made to withstand forces applied to cut, grasp, and debride equine bone and, along with the arthroscope, may break.

Improper Case Selection

Case selection is the most important disadvantage. Poor case selection can make arthroscopic surgery difficult and disappointing. Although much information can be gained by arthroscopic examination of any joint, prognosis should be carefully considered when operating on joints in which extensive osteoarthritis exists. Inadequate communication before surgery may leave owners and trainers with too high expectations of results. Often they have little appreciation for the magnitude of cartilage damage and osteoarthritis (OA), and they only see or hear about the chip fracture(s) visible radiologically. Owners and trainers tend to want to do something, but removal of osteochondral fragments from a carpus or fetlock joint with hopeless OA can be time consuming, cause instrument failures, and, worse, often results in a poor outcome. Poor prognosis associated with some conditions must be well communicated to owners before surgery. For example, we recently reviewed the results of surgical and conservative management of scapulohumeral osteochondrosis and found that overall, prognosis was poor.³ Prognosis varied inversely with the severity of radiological changes, and only 15% of potential racehorses started a race. Four of six nonracehorses were sound for intended use. Surgery did not improve prognosis.³

The fragment size that can be easily removed during arthroscopic surgery is limited, and the instrument portal must be enlarged to accommodate such fragments unless ostectomy is performed. The fragment must be located in the joint or at least close to it, a decision that must be made before surgery because arthroscopic surgery is of little benefit if the fragment is not in the joint or close enough to make the approach reasonable and safe. In the metatarsophalangeal joint, large plantar process fragments from the proximal phalanx are often located extraarticularly, and although they may still be best removed using conventional surgical techniques, I have removed large fragments with arthroscopic instrumentation; surgery is facilitated by use of a motorized synovial resector (Figure 23-1). Differentiation should be made preoperatively between fragments free in a joint, which are accessible to surgical removal, and those embedded in the joint capsule and therefore not readily removed. In the stifle joint, fragments in the distal aspect of the femoropatellar joint may appear radiologically as if they are in the femorotibial joint. Rare fragments in the caudal pouches of the medial and lateral femorotibial joints can be difficult to retrieve, especially if the precise location cannot be determined radiologically before surgery. The approaches to the difficult caudal pouches of the medial and lateral femorotibial joints were recently refined.⁴ Highly mobile fragments in a large joint such as the femoropatellar joint can prove challenging to locate. There is still a limited role for arthrotomy in equine surgery. For example, I still prefer to use a small, medial, middle carpal arthrotomy to repair sagittal slab fractures of the third carpal bone (C3) because I believe I can more accurately place the screw in the medial aspect of the C3, between the C3 and the second carpal bone.⁵ Others prefer a technique using arthroscopic guidance.¹

Fig. 23-1 A, Dorsal 25° proximal medial-plantarodistal lateral oblique digital radiographic image of the right hind (RH) metatarsophalangeal joint (MTPJ) in a 2-year-old Standardbred (STB) trotter showing a typical intraarticularly located plantar process fragment (arrow) easily removed using arthroscopic techniques. This “down angled” oblique radiographic image is useful to evaluate the region between the base of the medial proximal sesamoid bone and the proximal aspect of the proximal phalanx to see these fragments. B, Dorsolateral-plantaromedial oblique digital radiographic image of the RH MTPJ in a 2-year-old STB pacing filly with large nonarticular (large arrow) and small articular (small arrow) plantar process fragments, which were all removed using arthroscopic techniques. To remove fragments outside the joint, a combination of sharp and blunt dissection and use of a synovial resector are necessary.