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Stifle disarticulation as a pelvic limb amputation technique in a cockatiel (Nymphicus hollandicus) and a northern cardinal (Cardinalis cardinalis).

Abstract: This clinical report describes the use of stifle disarticulation in 2 avian patients as an alternative to transfemoral limb amputation. A northern cardinal (Cardinalis cardinalis) was presented for soft tissue swelling and a traumatic fracture of the third digit of the left limb, with secondary bacterial infection and necrosis. A 25-year-old cockatiel (Nymphicus hollandicus) was diagnosed with distal extremity necrosis after a nonunion of a closed tibiotarsal fracture. In both cases amputation was recommended due to the poor prognosis for healing and because both birds were poor surgical candidates for traditional methods of amputation due to patient size or age. Therefore, stifle disarticulation surgery for amputation of the pelvic limb was performed successfully in both cases and recovery was unremarkable. The outcomes of these 2 cases suggest that stifle disarticulation may be used as an alternative to transfemoral amputation in birds where prolonged surgery, anesthesia, or patient size precludes traditional amputation techniques.

Key words: stifle disarticulation, amputation, orthopedic surgery, surgery, knee, avian

Clinical Report

Case 1

An approximately 1-year-old, 40-g captive male northern cardinal (Cardinalis cardinalis) with a 6week history of an injured distal left tarsus was presented for examination. On initial presentation, the patient was grade 3/5 lame on the left limb with edema and ulceration evident on the left foot. The third digit of the left foot appeared black and necrotic (Fig 1). No other abnormalities were present on physical examination. The bird was sedated with midazolam (6 mg/kg IM; Hospira Inc, Lake Forest, IL, USA), and radiographs were taken. Imaging revealed significant circumferential soft tissue swelling of the tarsus and a complete fracture of the proximal phalanx of digit 3 of the left limb. Because of the concern for secondary bacterial infection and devitalization of the digit, amputation at the level of the stifle was recommended. The bird was started on meloxicam (0.5 mg/kg PO ql2h) and enrofloxacin (25 mg/kg PO q24h, compounded suspension), and surgery was scheduled for the next day.

On the morning of surgery, the bird was premedicated with midazolam (4 mg/kg IM) and butorphanol (2 mg/kg IM; Torbugesic, Zoetis, Florham Park, NJ, USA) and induced and maintained with isoflurane in oxygen delivered by mask. It was placed in dorsal recumbency and the surgery site was prepped aseptically. A circumferential skin incision was made distal to the stifle (Fig 2a). The subcutaneous tissues and overlying muscle were bluntly dissected with tenotomy scissors and bipolar electrosurgery. A circumferential modified Miller's knot with 4-0 polyglyconate (Maxon, Covidien, Minneapolis, MN, USA) was placed around the distal femur encircling the muscle bellies and occluding the vasculature running distally (Fig 2b and c). A modified Miller's knot incorporates 2 initial loops around the tissue, with the free end of the suture placed under the loops to produce the first throw of a knot, with the remainder of the knot secured by sequential square knots. A complete incision through the joint capsule and the stifle joint was made with a #15 scalpel blade. The femorotibial joint was disarticulated, and the structures distal to the femoral condyles were removed (Fig 2d). Minor hemorrhage was controlled with digital pressure. The muscle tissue distal to the ligation was apposed with 5-0 polyglyconate in a simple continuous suture pattern. The skin was closed by a simple continuous pattern with 5-0 polyglyconate (Fig 2e). The bird recovered uneventfully. After surgery, the patient had a normal appetite and was able to maintain balance properly on the remaining limb. The bird was discharged the same day, and treatment was continued with meloxicam (0.5 mg/ kg PO q24h) and enrofloxacin (25 mg/kg PO q24h) for an additional 5 days. Three weeks after surgery, the patient was presented for examination and suture removal. The incision site had healed and sutures were removed. Developing pododermatitis of the right foot was evident, with a small circular ulceration present on the plantar surface of the fourth digit. No other physical abnormalities were observed. Although no further examinations were conducted, an interview with the owner revealed that the patient had few complications after surgery. The bird developed mild intermittent pododermatitis beginning a month after surgical treatment that resolved with softer padding and alternative perches. It also developed an ulceration on its keel, likely from using it for balance, which healed well without treatment. The bird died unexpectedly approximately 1 year after surgery. Although a postmortem examination was not performed, the cause of death was not suspected to be related to the amputation.

Case 2

A 25-year-old male cockatiel (Nymphicus hollandicus) weighing 89 g was presented originally for a suspected pelvic limb fracture after a traumatic injury. On initial presentation, the bird was nonambulatory on the left pelvic limb, and a closed midshaft fracture of the tibiotarsus was palpable. The bird was sedated with midazolam (2 mg/kg IM) and butorphanol (2 mg/kg IM), radiographs were taken to confirm the left tibiotarsal fracture, and a tape splint was applied to stabilize the fracture. Sedation was reversed with flumazenil (0.05 mg/kg IM), and amoxicillin/ clavulanic acid (100 mg/kg PO ql2h for 7 days) and meloxicam (1 mg/kg PO q24h for 10 days) were prescribed. The patient was discharged after 3 days of hospitalization with instructions to confine the bird to an enclosure that prevented climbing. At the 2-week recheck appointment, complete devitalization of digits 1-3 of the left foot and sloughing of the skin of the distal foot were visible (Fig 3). The fracture site remained unstable after removal of the splint under the same sedation protocol as described above. Amputation was recommended because of the compromised vascular supply to the distal left limb. A blood sample was collected for preanesthetic evaluation. The results of the complete blood count and the plasma biochemical evaluation (VetScan Avian Reptilian Profile Plus, Abaxis Inc, Union City, CA, USA) revealed no clinically significant abnormalities. Whole body radiographs demonstrated a nonunion fracture of the mid-diaphysis of the left tibiotarsus with mild craniodistolateral displacement and progressive cellulitis and edema. There was also mild degenerative joint disease present in the right stifle. Surgical amputation of the left pelvic limb was elected by the owner over euthanasia. Before surgery, the patient received meloxicam (1 mg/kg PO q24h) and trimethoprimsulfamethoxazole (30 mg/kg PO ql2h) and was given a single vitamin K injection (2 mg/kg SC).

For anesthesia, the patient was premedicated with midazolam (3 mg/kg IM) and butorphanol (2 mg/kg IM). The bird was induced with isoflurane administered by face mask then intubated with a 16-gauge intravenous catheter and maintained on a nonrebreathing system. Intraoperative fluid therapy consisted of a continuous-rate infusion of a balanced electrolyte solution (10 mL/kg per hour) and bolus of hetastarch (10 mL/kg; Vetstarch, Abbott Laboratories, North Chicago, IL, USA), administered via an intraosseous catheter (22gauge spinal needle) placed in the right distal ulna.

The patient was placed in dorsal recumbency, and the surgery site was prepped aseptically. The surgical procedure was repeated in a similar manner described in case 1 above; however, the muscle tissue distal to the ligation was not apposed in this case. The subcutaneous tissue was closed with 4-0 polyglyconate in a simple continuous pattern, and the skin was closed with 4 simple interrupted sutures with 4-0 polyglyconate. The patient received flumazenil (0.05 mg/kg IM), and recovery from anesthesia was uneventful. After surgery, the bird received another dose of butorphanol (2 mg/kg IM) and by that evening was consuming its regular diet and drinking water. No postoperative hemorrhage or discomfort was observed. During hospitalization for 2 days after surgery, the patient received meloxicam (1 mg/kg PO q24h) and trimethoprim-sulfamethoxazole (30 mg/kg PO ql2h), and medication was continued for 2 more days after discharge.

The cockatiel was re-examined 13 days after surgery for evaluation of the surgical site and suture removal. The incision site was healed, and mild increased wear and hyperkeratosis were observed on the plantar aspect of the right foot consistent with increased weight bearing on the affected limb. Recommendations were made to replace perches with softer material to decrease the probability of pressure sores and pododermatitis developing on the weight-bearing limb. Follow-up phone conversation with the owner 2 months after the last recheck appointment revealed no concerns.


To our knowledge, this is the first report of disarticulation of the stifle joint as a method of pelvic limb amputation in birds. Because of the patient size (case 1) and advanced age (case 2), this technique was selected as an alternative to transfemoral limb amputation or euthanasia. Both birds recovered uneventfully from surgery, and follow-up examinations revealed adequate healing, return to function after amputation, and a subjectively good quality of life. These cases suggest that stifle disarticulation may be used as an alternative to transfemoral amputation in avian patients in which prolonged anesthesia and surgery or patient size precludes traditional amputation techniques. In both patients, amputation was recommended as the treatment of choice because of the poor prognosis for fracture healing, vascular compromise, necrosis, and infection of the distal pelvic limb.

In avian species, the most common sites for pelvic limb amputation are transection of the proximal tarsometatarsus and midfemur. (1,2) Some advocate the proximal tarsometatarsal technique, because the resulting stump can be used for moderate weight bearing. (2) However, the remaining stump is at risk of becoming traumatized, and most practitioners prefer the midfemoral transection method. (2,3) Because a significant portion of the femur is located within the body wall in avian species, a midfemoral amputation results in sufficient soft tissue for closure and prevents self-induced trauma to the amputated limb. (4)

To our knowledge, stifle disarticulation has not been used in veterinary species; however, in human orthopedics, stifle disarticulation, or through the knee amputation, is an established technique of pelvic limb amputation. (5,6) This method was first performed in 1824 as a way to perform amputations quickly with less blood loss. (5,6) However, with the advent of modern anesthesia and aseptic techniques, this method fell out of favor and femoral or tibial transection techniques were preferred because of better cosmetic outcomes and easier prosthesis utilization. (7,8) Recent technique modifications and prosthesis advances, however, have made these concerns less relevant. (7,9) Through-the-knee amputation in humans is an acceptable method of amputation and is performed mainly in patients who are elderly, pediatric, or nonambulatory or who have spinal cord injury or vascular disease. (7,9) This technique is preferred in pediatric patients, because it maintains femoral length by preserving the distal femoral epiphysis necessary for growth. (10) This technique also has less potential for hip or knee joint contracture compared with transfemoral or transtibial techniques. (5) A meta-analysis evaluating human amputation studies over the last 10 years also found that through-the-knee amputation had superior physical component scores, a measure of quality of life and mobility, compared with above-the-knee amputation." The main disadvantage of the procedure in people is a decreased cosmetic outcome, and healing complications with long tissue flaps have also been reported. (12,13)

Anatomically, the stifle joint of avian species is similar to mammals. The joint includes the distal articular condyles of the femur, the patella, the fibular head, and the proximal tibiotarsus. (14) It is also supported by similar soft tissue structures, including both cranial and caudal cruciate ligaments, the joint capsule, the patellar ligaments, the medial and lateral collateral ligaments, and 2 menisci with their associated ligaments. (15) The caudal cruciate ligament attaches to the intercondylar groove of the femur and attaches to the medial tibial condyle posteriorly. The cranial cruciate variably attaches to the lateral femoral condyle or in the intercondylar region, depending on species, and inserts in the center of the tibial plateau. (15) The tibial and fibular nerves run along the lateral aspect of the stifle joint and the proximal portion of the tibiotarsus and fibula. The medullary cavity of the tibiotarsus is often composed of medullary bone, whereas the femur is pneumatized in some avian species, connecting to the abdominal air sacs. (16) The stifle joint itself is made up of 3 joints: femoropatellar, femorotibial, and femorofibular. The femorotibial joint is the major weight-bearing joint in the stifle and functions mainly in flexion and extension. (14) The femorotibialis muscle is located on the dorsal aspect of the femur and inserts on the cnemial crest of the tibiotarsus to function in extension of the stifle. (14) The patella is located within the tendon of the femorotibialis muscle. The iliofibularis muscle and the flexor cruris medialis and lateralis muscles are responsible for flexion of the stifle.

In the 2 birds we describe, stifle disarticulation was the chosen surgical technique. The advantages of this procedure are decreased surgical and anesthesia time, a more simple surgical procedure, reduced blood loss, less trauma to soft tissue structures, and the lack of required bone and muscle sectioning. (6,7,10,11) It also may produce a longer lever arm, resulting in better proprioception and balance, as seen in human patients. (7,12) Because avian species are more similar to people in their bipedal nature compared with other species, these advantages may be applicable in the cases in this report as well.

In the 2 patients in this report, intrasurgical hemorrhage and resulting acute hypovolemia were of great concern because of the small size of the birds, particularly in case 1 (40-g body weight). In the case of disarticulation, risk of hemorrhage is decreased because of less muscle mass to transect and because the vasculature is ligated with a single circumferential ligation incorporating the blood vessels, muscle, and femur. Therefore, overall risk of hemorrhage is decreased with this technique.

Another benefit of disarticulation over midfemoral amputation in these cases was the abbreviated anesthesia time required. Because disarticulation is surgically less challenging and less muscle and soft tissue dissection is required, the procedure is significantly shorter compared with traditional methods of amputation. Although knowledge of the relative anatomy is important, because of the smaller patient size selected for this procedure, specific anatomic structures are not able to be individually appreciated. Dissecting out individual ligaments and muscles during the amputation is not recommended, because this will prolong the surgical procedure. In the transarticular amputation technique described, we recommended palpating the articulation between the femur and the tibiotarsus and sectioning the muscle, ligaments, joint capsule, and vasculature with a single transecting cut. Patient 2 was of geriatric age, and although preanesthetic blood profiles reflected adequate organ function, the length of the surgical procedure was of great concern. In that case, disarticulation was favored because of the decreased anesthetic risk to the patient and therefore greater chance of a successful recovery.

Different species of birds have variable amounts of pneumatization of the appendicular skeleton. In most birds, the sternum, scapula, humerus, femur, pelvis, and thoracic vertebrae contain diverticula of the air sacs.14 When performing a transfemoral amputation, there is a risk of entering one of these diverticula if femurs are pneumatized. This risk is not present in the case of stifle disarticulation.

A complication of this procedure that is also seen in other pelvic limb amputation techniques is pododermatitis developing in the contralateral limb. (16,17) This complication is less likely in smaller birds fed a balanced diet and provided with appropriate perches. (3,5) However, the bird should always be monitored after surgery for development of pododermatitis of the remaining pelvic limb. Suggested negative prognostic indicators of pelvic limb amputation in birds include obesity, degenerative changes in the opposite limb, and disorders affecting the wings, which are crucial for balance. (4) Although case 2 had evidence of degenerative joint disease in the contralateral limb at the time of amputation, the procedure was still elected over euthanasia at the client's request. Because of the patient's geriatric age and the fact that no overt clinical signs of osteoarthritis were present, the amount of progressive degeneration to the right stifle with increased weight bearing was thought to be of minimal concern.

The 2 cases in this report represent successful pelvic limb amputation using a transarticular stifle disarticulation technique. While the current preferred method of pelvic limb amputation in birds is the transfemoral approach, this method of amputation is not appropriate for all patients. (1-3) Although further investigation of the postoperative complication rate and a larger patient sample size is needed, this surgical technique may be considered in birds in which traditional methods of amputation are contraindicated.

Sarah Ozawa, DVM, and Christoph Mans, Dr med Vet, Dipl ACZM

From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA.

Acknowledgment: We thank Dr Grayson Doss for taking the photographs used in Figure 2.


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Caption: Figure 1. Gross appearance of distal extremity injury in a northern cardinal. Note the necrosis of the left third digit.

Caption: Figure 2. Surgical knee disarticulation procedure demonstrated in a northern cardinal cadaver, (a) Circumferential skin incision at the level of the stifle, (b) Placement of a circumferential modified Miller's knot around the distal femur encircling the musculature and vasculature, (c) Appearance of the ligation (arrow) after tightening of the knot, (d) Transection of the stifle joint and surrounding soft tissue, (e) Appearance of the amputation site after closure of the skin.

Caption: Figure 3. Appearance of the left pelvic limb in an approximately 25-year-old male cockatiel 2 weeks after diagnosis and treatment (external cooptation) of a right tibiotarsal fracture. Note the complete devitalization of digits 1-3 of the left foot and sloughing of the skin of the distal foot.
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Author:Ozawa, Sarah; Mans, Christoph
Publication:Journal of Avian Medicine and Surgery
Article Type:Report
Date:Mar 1, 2017
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