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Use of an extracapsular stabilization technique to repair cruciate ligament ruptures in two avian species.

Abstract: An extracapsular stabilization technique was used to repair cruciate ligament ruptures in a trumpeter hornbill (Bycanixtes bucinator) and an African grey parrot (Psittacus erithacus). The hornbill demonstrated cranial drawer motion and severe rotational instability of the stifle from ruptures of the cranial and caudal cruciate ligaments and stifle joint capsule. The luxation was reduced, and the fibula was cranially transposed, in relation to the tibiotarsus, and anchored with 2 positive profile threaded acrylic pins. A lateral extracapsular stabilization was then performed. The African grey parrot had a traumatic stifle luxation, and an open reduction and a lateral extracapsular stabilization were performed. Both birds regained function of the affected leg by 1 month after surgery. Extracapsular stabilization allows motion of the stifle joint to be maintained during the postoperative recovery period, an advantage over rigid stabilization. Maintaining motion in the stifle joint facilitates physical therapy and can aid in full recovery after avian stifle injuries.

Key words: cruciate ligament, fibula, extracapsular stabilization, lateral suture technique, stifle joint luxation, orthopedics, avian, trumpeter hornbill, Bycanistes bucinator, African grey parrot, Psittacus erithacus

Clinical Report

A 14-year-old male trumpeter hornbill (Bycanistes bucinator) was being treated for previously diagnosed hemochromatosis. During capture for celioscopy and biopsy, the keeper staff observed that the bird was not using its left leg to perch. It was captured and evaluated under general anesthesia. The animal was induced with 4% isoflurane administered by mask, intubated with a 3.5mm uncurled endotracheal tube, and maintained at 1.5%-2% isoflurane, with intermittent manual ventilation. Palpation revealed moderate soft tissue swelling over the stifle and the proximal portion of the tibiotarsus, with a mild increase in internal and external rotational mobility of the stifle joint. Radiographs showed a cranial displacement of the left tibiotarsus in relation to the fibula and the femur, which was not palpable (Fig 1). Results of a complete blood cell count were within reference ranges. Plasma biochemical results revealed a high concentration of aspartate aminotransferase (280 U/L; in-house reference range, 155 [+ or -] 63 U/L) and a creatine kinase concentration above the detectable range (>2500 U/L). A diagnosis of traumatic stifle luxation with cranial displacement of the tibiotarsus was made, and surgery was scheduled for the next day at a referral facility. Meloxicam (0.3 mg/kg IM; Metacam, Boehringer Ingelheim Vetmedica, St Joseph, MO, USA) and butorphanol (2 mg/kg IM; Fort Dodge Animal Health, Fort Dodge, IA, USA) were administered for overnight analgesia.

The next morning, the bird was premedicated for surgery with butorphanol (2 mg/kg IM), induced and intubated as previously described, and maintained at 2%-2.5% isoflurane for radiographs and surgery. During the 2-hour procedure, the animal received lactated Ringer's solution (10 ml/kg/h IV). Palpation revealed an excessively mobile fibula, 60[degrees]-75[degrees] of internal and external rotational instability, and 5-7 mm of positive cranial drawer motion in the stifle.


A lateral incision was made over the tibiotarsus, which exposed the fibula, a large blood clot, and bruised muscle tissue. The stifle joint capsule and the cranial and caudal cruciate ligaments were ruptured; the medial and lateral collateral ligaments were intact. The cruciate ligaments were debrided with a no. 11 scalpel blade. The stifle luxation was manually reduced, the fibula was advanced craniad, relative to the femur and tibiotarsus, and secured with two 0.035-inch (0.89-mm) diameter positive-profile threaded acrylic pins (Imex Veterinary Inc, Longview, TX, USA) placed through the fibula into the tibiotarsus. A hole was drilled in the tibial tuberosity, and a nonabsorbable suture (2-0 Prolene, Ethicon Inc, Somerville, NJ, USA) was placed through the hole and around the origin of the lateral collateral ligament on the femur to further stabilize the stifle joint. The skin and subcutaneous tissues were closed with absorbable monofilament polydioxanone (5-0 PDS II; Ethicon). Postoperative radiographs showed good apposition of the tibiotarsus and fibula, with cranioproximal transposition of the fibula (Fig 2). Cranial drawer motion and rotational instability were not palpable after surgery. The anesthesia and recovery were uneventful. The bird received meloxicam (0.3 mg/kg IM) at the end of surgery and butorphanol (2 mg/kg IM) at extubation. Additional postoperative analgesia consisted of meloxicam (0.2 mg/kg PO q24h for 7 days), and antimicrobial prophylaxis consisted of enrofloxacin (12 mg/kg PO q24h; Baytril, Bayer Animal Health LLC, Shawnee Mission, KS, USA) and terbinafine (10mg/kg PO q24h; Novartis Pharmaceuticals Corp, East Hanover, NJ, USA) for 10 days. After returning to the holding facility, the bird could bear weight on its hocks but could not perch with the left foot. Coxofemoral joint motion was normal bilaterally, but the left tarsal joint was flaccid and the digits were held flexed. Grasping and superficial pain responses could not be elicited for the left foot but were normal for the right foot. Passive range of motion was not performed in the immediate postoperative period because of the risk of injury with repeated capture. The bird was provided with low perches and encouraged to flex and extend the limb during training exercises. At 7 days after surgery, the hornbill was radiographed while it was under isoflurane anesthesia administered by mask. A fracture of the fibula had occurred between the pin sites, and the distal fragment was caudally displaced (Fig 3). The proximal fragment was stable on palpation, and stifle instability was not detected. Meloxicam therapy was continued at the above dosage for a further 14 days. The bird was manually restrained for range of motion exercises on the stifle, hock, and interdigital joints, which were repeated every 3 days. No change in limb use or radiographic changes were present when the hornbill was examined and radiographed 14 days after surgery. Over the next 20 days, limb function gradually returned, beginning with limited movement of the hock joint and progressing to movement of the digits. By 25 days after surgery, the bird regained perching and grasping ability, and, at 35 days after surgery, it had full use of the foot.



A 6-year-old male African grey parrot (Psittacus erithacus) was referred for evaluation of a nonweight-bearing lameness of the right leg of 1 week's duration. The parrot had become acutely lame after a routine nail trim, and the condition had not improved with 1 week of cage rest. On initial evaluation, the parrot was able to grasp weakly but could not bear weight on the limb, and the stifle area was markedly swollen. Physical examination was otherwise unremarkable, and no abnormalities were present on a complete blood cell count and plasma biochemical analysis.

On radiographic examination, a right stifle luxation with cranial and proximal displacement of the tibiotarsus and patella was observed (Fig 4). The parrot was premedicated with butorphanol (2 mg/kg IM), mask-induced with isoflurane, then intubated with a 14F Cole endotracheal tube and maintained on isoflurane anesthesia. A 1.5-cm lateral incision was made over the right stifle, and the fascia overlying the stifle was bluntly dissected. The joint capsule was opened, and 2 mosquito hemostats were introduced into the joint to lever the craniolaterally displaced tibiotarsus caudally. The joint was stabilized with nylon suture (2-0 Ethilon; Ethicon) passed craniocaudally through holes drilled in the lateral femoral condyle and the tibial tuberosity. The stifle was maintained in flexion during the suture placement, and, once stabilized, it could not be manually reluxated. The fascial layers were closed with 4-0 Maxon (Syneture, Norwalk, CT, USA) in a simple interrupted pattern, and the skin was closed with 4-0 nylon in a cruciate pattern. The leg was bandaged in moderate flexion by using a thermoplastic splint (Orthoplast, Johnson & Johnson, New Brunswick, NJ, USA) and padding. The parrot received postoperative butorphanol (2 mg/kg IM PRN) and enrofloxacin (15 mg/kg PO ql2h for 10 days) for antimicrobial prophylaxis.


The bandage was removed 14 days after surgery, and the stifle was still reduced. The range of motion in the stifle joint was decreased, and the parrot was able to bear weight and grasp normally. The owner continued cage rest, and the bird was allowed movement between low perches to encourage use of the leg and to maintain mobility in the stifle. Recheck radiographs and orthopedic examination performed a month after surgery showed that the stifle was still adequately reduced, with near normal range of motion. Moderate soft tissue swelling remained. The referring veterinarian reported that the parrot maintained normal range of motion, ambulation, and perching for at least 2 years after surgery.


In this report, we described a nonrigid stabilization method for avian stifle injuries and highlight the potential for nerve damage with stifle injury. In both cases described in this report, routine handling seemingly led to stifle derangements and loss of function in a pelvic limb. Both birds experienced gradual return of function; however, the 2 cases differ in that the African grey parrot did not have a neurologic injury, and its recovery was more rapid.

Options for stabilizing stifle luxations in birds include rigid immobilization with external skeletal fixation, arthrodesis, and placing conjoined intramedullary pins in the femur and tibiotarsus. (1-5) Herein, we describe the stabilization of stifle joint luxation with an extracapsular stabilization with lateral nonabsorbable sutures. This technique has the advantage of maintaining mobility in the stifle joint. (6) Maintaining joint motion during the recovery period has theoretical advantages in decreasing the likelihood of cartilage damage and the loss of joint motion. (7) Surgery of the avian stifle carries a risk of fibular nerve damage that can lead to a prolonged recovery or permanent neurologic compromise.' Preserving joint mobility and nerve function is essential for proper perching and for preventing pododermatitis in the postoperative period. (2)

Although the relative proportion of bones in the avian pelvic limb varies considerably by taxonomy, the components and general structure are conserved across species. (8-10) The bones of avian stifle joints include the femoral condyles, the proximal tibiotarsus, and the fibular head. (9) The main supporting structures include cranial and caudal cruciate ligaments, joint capsule, patellar ligaments, medial and lateral collateral ligaments, and menisci." (10-12) The proximal third of the fibula has a fibrous synarthrosis with the lateral tibiotarsus by means of the interosseous ligament and is attached at the fibular crest by a bifurcated proximal tibiofibular ligament. The lateral collateral ligament originates on the femur and inserts on the fibula. (9) Although the fibula is not a weight-bearing bone, the attachment of the lateral collateral ligament to the femur and fibular head provides stability to the lateral aspect of the stifle. (9)

The lateral suture technique has multiple variations described in dogs. Most include placing the suture through a hole in the tibial tuberosity, as was performed in these birds. (6) The absence of fabellae in the avian stifle requires anchoring the suture to the femoral attachment of the lateral collateral ligament, as in the first patient, or through a hole in the lateral femoral condyle, as described in the second patient. Fibular head transposition and stabilization with a lateral fabellar to tibial suture are used in dogs, although not combined. (6,13,14 In one report in dogs, lateral suture stabilization showed greater success than fibular head transposition in alleviating the stifle instability that resulted from cranial cruciate rupture. (14) The hornbill in this report had a cranial luxation of the tibiotarsus, without displacement of the fibula relative to the femur. This type of luxation has not been described in dogs or birds, and requires rupture of the cruciate ligaments, tibiofibular ligament, and the interosseus ligament, without damage to the lateral collateral ligament. (11,13) Detachment of the fibula from the tibiotarsus likely leads to the rotational instability of the joint. The presence of intact collateral ligaments provided support to the stifle once the fibula was anchored to the tibiotarsus. If the collateral ligaments had been ruptured, then the stifle would have retained rotational instability, warranting complete immobilization of the joint.

The tibial and fibular nerves are branches of the ischiatic nerve and course along the lateral aspect of the stifle joint and proximal portion of the tibiotarsus and fibula. The smaller fibular nerve innervates the craniolateral muscles of the crus and pes, which are essential for tarsal flexion and digit extension. The tibial nerve supplies the extensors of the hock joint and the digital flexor muscles. (8) Damage to the fibular and tibial nerves and associated muscles during a traumatic injury or surgical correction results in temporary or permanent loss of function in the distal leg and foot. (1,8) Paresis or paralysis of the distal limb can impair the ability to perch and lead to secondary pododermatitis on the contralateral foot. (2) Both birds in this report had recovery periods that lasted more than 30 days. The trumpeter hornbill exhibited severe neurologic deficits in the foot, which suggested fibular nerve damage, and physical therapy was possibly helpful in preventing contractures during recovery. Whether the nerve injury in the trumpeter hornbill was iatrogenic or resulted from the initial injury is unknown. A relatively long recovery period should be expected for return to function after fibular nerve injury.

Injuries to the stifle are uncommon in avian medicine, and reported surgical repairs have involved rigid external and internal fixation to achieve a fibrous ankylosis or arthrodesis of the joint. (1-5) Reported complications of rigid stabilization in birds include infection, neuromuscular damage, and loss of joint mobility. (1,2,5) In dogs, prolonged joint immobilization can lead to cartilage damage, soft tissue contracture, intraarticular adhesion formation, and decreased synovial fluid production. These complications can potentially be avoided by allowing some mobility in the stifle during the postoperative period. (7) For the birds described here, the immediate outcome was a moderately decreased range of motion in the stifle, which improved during the recovery period with physical therapy. Although reports of avian stifle luxation and cruciate rupture repair exist, to our knowledge, there are no reports of extracapsular stabilization followed by physical therapy. (2-4)


(1.) Donato LN. Stifle arthrodesis in a military macaw utilizing safe, hazardous, and danger zones. Proc Annu Conf Assoc Avian Vet. 2000:121-126.

(2.) Helmer P, Redig PT. Surgical resolution of orthopedic disorders. In: Harrison G J, Lightfooot TL, eds. Clinical Avian Medicine. Vol II. Palm Beach, FL: Spix Publishing; 2006:768-771.

(3.) Rosenthal K, Hillyer E, Mathiessen D. Stifle luxation repair in a Moluccan cockatoo and a barn owl. J Assoc Avian Vet. 1994:8:173-178.

(4.) Bowles HL, Zantop DW. A novel surgical technique for luxation repair of the femorotibial joint in a monk parakeet (Myiopsitta monachus). J Avian Med Surg. 2002; 16:34-38.

(5.) Harris MC, Diaz-Figueroa O, Lauer SK, et al. Complications associated with conjoined intramedullary pin placement for femorotibial joint luxation in a Solomon Island eclectus parrot (Eclectus roratus solomonensis). J Avian Med Surg. 2007;21:299-306.

(6.) Piermattei DL, Flo GL. The stifle joint. Brinker, Piermattei, and Flo's Handbook of Small Animal Orthopedics and Fracture Repair. 3rd ed. Philadelphia, PA: WB Saunders; 1997:534-559.

(7.) Jaeger GH, Wosar MA, Marcellin-Little D J, Lascelles BD. Use of hinged transarticular external fixation for adjunctive joint stabilization in dogs and cats: 14 cases (1999-2003). J Am Vet Med Assoc. 2005;227:586-591.

(8.) Orosz SE, Ensley PK, Haynes CJ. Anatomy of and surgical approaches to the leg: femur. In: Avian Surgical Anatomy. Thoracic and Pelvic Limbs. Philadelphia, PA: WB Saunders; 1992:59-77; 102-106.

(9.) Chamberlain FW. Atlas of Avian Anatomy: Osteology, Arthrology, Myology. East Lansing, MI: Hallenbeck Printing Company; 1943.

(10.) Fuss FK, Gasser CR. Cruciate ligaments of the avian knee: insight into a complex system. J Morphol. 1992;214:139-151.

(11.) Baumel JJ. Arthrologia. In: Baumel JJ, ed. Nomina Anatomica Avium. London, England: Academic Press; 1979:157-169.

(12.) Vanden Berge JC. Myologia. In: Baumel JJ, ed. Nomina Anatomica Avium. London, England: Academic Press; 1979:201-216.

(13.) Piermattei DL, Flo GL. Fractures of the tibia and fibula. In: Brinker, Piermattei, and Flo's Handbook of Small Animal Orthopedics and Fracture Repair. 3rd ed. Philadelphia, PA: WB Saunders; 1997: 581-606.

(14.) Conzemius MG, Evans RB, Besancon MF, et al. Effect of surgical technique on limb function after surgery for rupture of the cranial cruciate ligament in dogs. J Am Vet Med Assoc. 2005;226: 232-236.

Sathya K. Chinnadurai, DVM, MS, Dipl ACZM, Gary Spodnick, DVM, Dipl ACVS, Laurel Degernes, DVM, MPH, Dipl ABVP (Avian), Ryan S. DeVoe, DVM, MSpVM, Dipl ACZM, Dipl ABVP (Avian), and Denis J. Marcellin-Little, DEDV, Dipl ACVS, Dipl ECVS

From the Department of Clinical Sciences at North Carolina State University, College of Veterinary Medicine, 4700 Hillsborough St, Raleigh, NC 27606, USA (Chinnadurai, Degernes, Marcellin-Little); the North Carolina Zoological Park, 4401 Zoo Parkway, Asheboro, NC 27203, USA (Chinnadurai, DeVoe); and Veterinary Specialty Hospital of the Carolinas, 6405-100 Tryon Rd, Cary, NC 27511, USA (Spodnick).
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Article Details
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Title Annotation:Clinical Reports
Author:Chinnadurai, Sathya K.; Spodnick, Gary; Degernes, Laurel; DeVoe, Ryan S.; Marcellin-Little, Denis J.
Publication:Journal of Avian Medicine and Surgery
Article Type:Report
Geographic Code:1USA
Date:Dec 1, 2009
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