Since the first descriptions of arthroscopic surgery in the horse, it has been assumed that this delicate and precise surgery should be performed under general anaesthesia. In the last decade two seminal publications have challenged this, presenting results of arthroscopy of the fetlock[1] and the stifle[2] in the standing sedated horse.
Needle arthroscopes, typically with a diameter less than 2 mm, are widely available. These are often single use devices in human surgical care, though are typically re-used in veterinary surgery. The devices are compact and lend themselves to standing surgery. Their use has been described, including for standing arthroscopy of the stifle, hock, carpal sheath and shoulder joint[3–5]. There are limitations with these devices. They are less rigid which can make positioning slightly more difficult, and they are not very long. The image quality is lower than modern 4K arthroscopy systems and the light intensity is lower. Finally, there is limited change to required analgesia; if you can make a 2 mm hole in a horse, you can make a 5 mm hole.
Fetlock
The initial description of fetlock arthroscopy in the standing sedated horse describes 103 horses, and surgery was successfully performed in all cases with no major intra or post operative complications[1], and similarly successful surgery was reported for 21 horses using a needle arthroscope[4]. It is rumoured that the technique evolved because the surgeon became impatient waiting for anaesthesia to arrive. This anecdote illustrates one of the important features of standing arthroscopy, that it can be commercially successful, expediting chip removal without the risks or expense of general anaesthesia. We have adopted this technique at Donnington Grove and standing arthroscopy is now the technique of choice for removal of dorso proximal P1 fragments.
Anaesthesia
We typically perform surgery, following a four point nerve block of the palmar (or plantar) and palmar metacarpal (or plantar metatarsal) nerves at the level of the distal end of the second and fourth metacarpal (or metatarsal) bones. This is usually augmented with a dorsal ring of local anaesthetic. An inverted “U” of local anaesthetic solution around the dorso proximal margin of the fetlock joint capsule has been described, ensuring the horse retains sensation of the foot[6]. It is helpful to distend the fetlock joint with local anaesthetic solution, partly to ensure complete intra articular analgesia, and partly as it facilitates joint distension without cables trailing across the room.
Draping
We have typically draped horses for standing arthroscopy in the same way as for standing fracture repair, with a disposable paper drape clipped around the pastern and covering the foot and floor, and gas sterilised “Vet-Wrap®” latex bandages wound around the limb. Even if performing unilateral surgery it is helpful to drape the contralateral limb to prevent inadvertent contamination of the surgeon.
Surgical Technique
No adaptation of arthroscopic technique is necessary. Removal of dorso proximal P1 fragments is a straightforward arthroscopic procedure and this remains the case when the horse is standing. Care should be taken to ensure the arthroscope portal is at the proximal margin of the joint, as the greater extension associated with weight-bearing reduces the proximal to distal depth of the joint. This is advantageous when performing surgery on the hind limb, where limited extension of the limb and pressure from the long digital extensive attendant can limit visualisation of the joint under general anaesthesia. One of the hardest parts of standing arthroscopy is cable management. Large drapes to cover much of the floor and room, allowing the cables to rest on the floor has been described[6]. We clip the three cables (light, camera lead and fluid) together using gas sterilised Ziploc® cable ties and then have a scrubbed assistant whose sole job is to hold the cables.
Debatably, one of the advantages of standing arthroscopy is that the surgeon may feel some time pressure, aware that the horse might start to move. Therefore the surgeon is focused on removing the fragment and finishing the surgery as quickly as possible. It could be argued that under general anaesthesia excessive attention can be paid to trying to achieve a perfectly debrided margin of the fragment bed, which ultimately just makes the defect bigger.
Stifle
Draping
Draping the stifle in the standing sedated horse is difficult and this procedure is typically undertaken without draping. We have found it can be very challenging if attempting to examine the stifle from medial, particularly in a gelding, when maintenance of asepsis is difficult.
Arthroscopic technique
Good results have been described with three horses[2]. Two underwent subsequent arthroscopic surgery under general anaesthesia but as the goal of standing surgery was to identify horses with a requirement for surgery under general anaesthesia, this is viewed as a success.
We have found the technique limited. There are few options for arthroscopic surgery rather than simple arthroscopic diagnosis and a substantial proportion of cases are converted to general anaesthesia for debridement of any identified lesions. We have used the technique to remove small fragments left behind after surgery for femoropatellar OCD.
Other Sites
Arthroscopic surgery for removal of chip fractures from the distal lateral radius in the antebrachiocarpal joint is reported[6]. It is possible to perform this surgery with the limb weight bearing, which results in a more stable surgical field. Diagnostic needle arthroscopy of the middle carpal joint is also reported[7].
Diagnostic needle arthroscopy of the tarsocrural joint is reported[3]. We have performed arthroscopic removal of fragments from the distal intermediate ridge of the tibia in the standing horse. Diagnostic needle tenoscopy of the carpal sheath is reported [8]. We have some reservations about this procedure in the standing horse, given the increased risk of post operative synovial sepsis in this structure[9]
We have used tenoscopy for removal of thorns from the extensor carpi radialis tendon sheath. O’Meara presented a poster at ECVS Cracow in 2023 reporting removal of proximal articular fragments following accessory carpal bone fracture. Standing arthroscopy has also been used for sepsis of the nuchal bursa and the temporomandibular joint. Standing diagnostic arthroscopy of the scapulohumeral joint has been reported[5]. Finally, most intriguingly, diagnostic arthroscopy of the caudal cervical facet joints has been described[10].
References