Arathi Vinayak VCA West Coast Animal Emergency and Specialty Hospital, Fountain Valley, CA, USA Thoracic and pelvic limb amputations are routinely performed procedures in small animal practice. The procedure is a salvage option when medical management or other limb‐sparing surgical options fail to address the problem. It is also considered when the cost of treatment for the owner becomes prohibitive to save the limb. Careful orthopedic and neurologic evaluation of the animal should be performed to ensure compensation with the remaining three limbs occurs following amputation. Marked obesity and significant orthopedic and/or neurologic disease of the remaining limbs are contraindications for amputation of a limb.1 Despite how well veterinary amputees recover, there is still considerable reservation against the procedure from owners and some veterinarians. It is, thus, important to prepare the owner about amputation as an option and regarding surgical esthetics and recovery, as adequate owner preparation in advance of the procedure showed higher owner satisfaction with the procedure.1 Concerns regarding the ability to compensate, concurrent osteoarthritis in remaining limbs/spine, compromise of other limbs due to compensation, change in attitude after surgery, postoperative pain, fear of anesthesia in an older pet, ability to resume normal activity, prognosis if cause of amputation is neoplasia, and thoracic limb versus pelvic limb are some of the more common owner concerns.2,3 The reality is that most dogs are reported to return to normal activity within one month following amputation.1,4 In clinically normal dogs, the thoracic limbs each take on 30% of the body weight while the pelvic limbs each distribute 20% body weight.5,6 This finding, however, does not appear to affect recovery from thoracic limb compared to pelvic limb amputation, as several studies show that there is no difference in owner perception of recovery.1,3 Age and breed size have not been found to be factors impeding recovery.1,3 Body weight did not appear to affect the time to reach best quality of life.3 Objective data regarding adaptation have been evaluated using spatial kinematic and kinetic data in pelvic limb amputee dogs, and it was shown that this adaptation occurs from increased range of motion at the contralateral tarsal joint, thoracolumbar and cervicothoracic vertebral regions, and extension of the lumbosacral vertebrae.6 A similar study evaluating adaptations for forelimb amputee dogs has shown that the ipsilateral pelvic limb served a dual thoracic and pelvic limb role during trotting.7 In fact, a study evaluating adaptations has shown that the adaptation process began before the amputation was even performed, contributing to the rapid recovery seen in most pelvic limb amputees.2 Magnetic resonance imaging evaluating the contralateral stifle in pelvic limb amputee dogs 120 days after amputation showed no cartilage damage or osteoarthritis.2 Overall, 91% of dog amputee owners perceived no change in attitude, 88% reported complete to near complete return to life prior to amputation, 78% indicated that the recovery was better than they were expecting, and 86% of owners indicated they would elect amputation again if given a choice based on their experience.3 While kinetic and kinematic studies are hard to perform in cats, a client survey in a multi‐institutional study of nearly all owners reported a good to excellent satisfaction with only 1.7% reporting fair satisfaction. In this same study, 84.7% of owners would elect for an amputation in another pet if needed based on their current experience.8 It is our responsibility as veterinarians to present objective information to owners regarding prognosis if amputation is being considered for malignancy. Bloodwork is indicated prior to amputation to determine general health status, and staging diagnostics are recommended as well if the procedure is being considered for neoplasia. Indications for limb amputation include trauma, neoplasia, neurological dysfunctions confined to one limb, chronic osteomyelitis, limb deformities (congenital, malunion fractures), severe infection, and vascular disease (thromboembolism, arteriovenous fistulas).9 Thorough knowledge of the intrinsic and extrinsic muscles of the limb is required prior to amputation, since only the extrinsic muscles need transection for successful amputation. Transection of the intrinsic muscles leads to surgical morbidity, longer anesthesia times, and increase in surgical blood loss. Maintaining hemostasis is paramount during the procedure. Anatomic location of large caliber blood vessels must be known such that these vessels can be isolated and ligated prior to transection. Smaller arteries and veins encountered should be addressed with electrocautery, hemoclips, or ligatures. While forelimb amputation can be performed distal to the scapula with a disarticulation at the level of the scapulohumeral joint leaving the scapula on the thoracic wall, there is no literature to support the procedure. Like a mid‐femoral amputation, muscle atrophy from disuse that occurs over time can lead to protrusion of the bony remnants against the skin, leading to ulceration and sores over the sites. Thus, the amputation preference in veterinary medicine is a complete forequarter amputation for the thoracic limb and a coxofemoral disarticulation for the pelvic limb. Multimodal analgesia should be considered in conjunction with opioids, N‐methyl‐D‐aspartate (NMDA) receptor antagonists‐antagonists, and anti‐inflammatories with local blocking of the nerve sheaths with lidocaine or bupivacaine prior to transection, which should ideally be performed with a blade instead of scissors for the sharpest transection. Infiltration of the transected muscle with liposome‐encapsulated bupivacaine available commercially should be considered at the time of surgical closure. Forequarter amputation is a procedure that disarticulates the scapula from the thoracic wall, removing the scapula with the limb (Figures 17.1 and 17.2). The entirety of the front leg to dorsal midline, cranial thorax, and thorax ventral to the front leg are clipped, and a rough prep is performed outside of the operating room. The patient is placed in lateral recumbency with the affected side up, and the leg is draped in using a standard hanging leg technique after a final surgical prep is performed in the operating room. A teardrop skin incision is made along the spine of the scapula to the acromion and continued circumferentially around the limb ventrally. Subcutaneous tissue is dissected away, to reveal the omotransversarius muscle along the cranial and ventral aspect of the scapula and the trapezius cranial and dorsal to the scapula. The omotransversarius and trapezius (both cervical and thoracic portions) muscles are transected at the spine of the scapula where it is least vascular, and the entirety of these muscles are saved for closure. Distal to the omotransversarius and cranial to the scapula, the cleidobrachialis muscle is transected near its insertion onto the humeral crest, or if amputating for neoplasia, transected mid‐belly. Cephalic and omobrachial veins encountered in this area are isolated and ligated with a suture ligature, hemoclip, or vessel‐sealant device prior to transection. Figure 17.1 Proposed incision for forequarter amputation of the left thoracic limb in a 10‐year‐old spayed female mixed‐breed dog. (a) Surgical markings in purple for proposed incisions indicate the dorsoventral line over the scapular spine to the acromion and continued circumferentially around the leg. (b) The ventromedial aspect of the leg showing continuation of the proposed circumferential incision. The dorsal spine of the scapula is grasped with a towel clamp and lifted laterally to expose the rhomboideus muscle attaching to the dorsal border of the scapula, which is transected along the scapula to expose the serratus ventralis muscle, which is also transected along its scapular attachment. The subcutaneous dissection is carried along the caudal aspect of the scapula with monopolar electrosurgery, a Freer or other periosteal elevator, or curved Mayo scissors to expose the caudally located latissimus dorsi muscle. This muscle is then transected carefully and methodically to identify the thoracodorsal neurovascular bundle along the deep fibers of the latissimus. The thoracodorsal artery and vein can be quite sizable in large dogs and can be a source of hemorrhage during dissection if they are not identified and ligated, being mindful to separate the nerve to sharply transect instead of ligating with the artery and vein.
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Limb Amputation in Companion Animals: Thoracic and Pelvic Limb Amputations
Introduction
Indications
Pre‐operative Considerations
Surgical Procedure
Thoracic Limb Amputation (Forequarter Amputation)
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