Abstract

Three hand-raised American flamingo (Phoenicopterus ruber ruber) chicks and one hand-raised Chilean flamingo (Phoenicopterus ruber chilensis) developed valgus angular limb deformities of the proximal tarsometatarsus. All flamingos underwent surgical correction to unequally retard the growth plate using transphyseal bridging. Positive profile pins were placed in the proximal epiphysis and distal to the growth plate in the metaphysis on the convex side of the affected tarsometatarsus. Various banding techniques were used in each flamingo to create tension. Three of the four flamingos responded in 7–14 days with correction or slight overcorrection of the valgus limb deformity. The fourth flamingo’s leg deformity did not improve for reasons thought to be involved in improper implant placement. Growth plate retardation by transphyseal bridging proved successful in correcting valgus limb deformity of the proximal tarsometatarsus. This technique may be considered as an option for correction of angular limb deformities of the proximal tarsometatarsus in flamingos less than 90–120 days of age.

Introduction

Angular limb deformities appear to be common in hand-raised, long-legged avian species.⁸ Etiologies in mammals include trauma, nutrition, genetics, and lack of or excessive exercise.^1,4,5 Similar etiologies are thought to be involved in angular limb deformities in avian species.^2,6-8 Treatments for mammalian species may be extrapolated for use in affected birds. This report presents a series of four flamingo chicks in which a procedure described in foals, physeal retardation by transphyseal bridging, was used.⁵

Case Report

Four flamingo chicks developed tarsometatarsal deformities: three American flamingos (Phoenicopterus ruber ruber) and one Chilean flamingo (Phoenicopterus ruber chilensis). Initial medical therapy for tarsometatarsus valgus limb deformity in the three American flamingo chicks included tension taping of the medial aspect of the tibiotarsal/tarsometatarsal joint, and implemented exercise (walking) with hydrotherapy (swimming). In addition, measured daily weight gains were decreased.

Case 1

An American flamingo developed valgus deformity of the left proximal tarsometatarsal bone at 34 days of age. Medical therapy as previously described was implemented for 14 days without clinical improvement. Radiographs of both tarsometatarsal bones revealed a 14° from normal valgus deformity of the proximal left tarsometatarsal bone. Minimally invasive surgical intervention was elected. The chick was anesthetized with isoflurane (IsoFlo, Abbott Laboratory, North Chicago, IL, USA) via face mask and then intubated with a 4-mm Cole tube. The skin on the medial aspect of the left tarsometatarsus was aseptically prepared. Butorphanol (Torbugesic, Fort Dodge Animal Health, Fort Dodge, IA, USA; 2 mg/kg IM) was administered for anesthetic sparing effects and pain management. Transphyseal bridging was performed using a sterile cordless handheld drill to place a 0.03-mm positive profile pin (IMEX Veterinary Inc., Longview, TX, USA) in the proximal epiphysis engaging the medial cortex of the left tarsometatarsal bone. A second pin was placed approximately 4 cm distal to the other pin in the metaphysis. The distal ends of each pin were bent 90° away from each other. The orthopedic pins were connected with 23-ga cerclage wire in a figure-eight pattern. A soft padded bandage was placed over the leg. Anesthetic recovery was uneventful, and the bird was using the leg the same day. Exercise therapy was reinstated. Radiographs at 10 days post-apparatus placement revealed a reduced valgus deformity of the tarsometatarsal bone and distraction of the pins due to bone growth. Orthodontic rubber bands were added to the pins and figure-eight wire to create constant dynamic tension. Radiographs at 15 days postoperative indicated slight overcorrection with a 1° from normal varus deformity of the left tarsometatarsus. The pins were removed from the left tarsometatarsus. The bird was immediately encouraged to walk, and hydrotherapy was reinstated 8 days post implant removal when the skin over the pin holes had closed. Six weeks postoperative, the left leg was clinically straight.

Case 2

A 75-day-old American flamingo chick presented with a mild valgus deformity of the proximal left tarsometatarsus. Radiographs verified a 15° from normal valgus deformity. Transphyseal bridging was performed as described in Case 1, and orthodontic rubber bands were applied instead of cerclage wire for constant dynamic tension. The orthodontic rubber bands had to be changed twice weekly to maintain continuous tension. At 14 days postoperative, rubber bands were changed, and two wire twist-ties were placed around both pins and twisted to create additional tension. Radiographs at this stage revealed a reduction from 14° to 4° valgus deformity from normal. At 25 days postoperative, the leg was visually straight, and radiographs revealed a mild overcorrection with a 2.5° varus deformity. The pins were removed, and the left leg appeared clinically normal.

Case 3

A 34-day-old American flamingo chick presented with a varus deformity of the proximal right tarsometatarsus. Medical therapy was implemented as described for Case 1. At 71 days of age, the proximal aspect and alignment of the right leg had straightened; however, the varus deformity remained and had grown distally on the tarsometatarsus. At this stage, surgical intervention was not elected.

At 79 days of age, a valgus deformity of the left leg had developed in the proximal tarsometatarsus. Radiographs revealed a 21° from normal valgus deformity and mild twisting of the mid-shaft right tarsometatarsus. Medical therapy as previously described was unsuccessful, and transphyseal bridging was performed at 90 days of age. The proximal pin was placed in the more distal aspect of the epiphysis, at the epiphyseal/physeal junction. Orthodontic rubber bands and 23-ga cerclage wire were both applied in this procedure. Three days postoperative, the cerclage wire was replaced with a twist-tie, and the rubber bands were changed. At this time, the proximal implant pin appeared to be loosening. At 7 days postoperative, the bird was limping significantly on the left leg. Radiographs revealed that the proximal pin was migrating out of the proximal epiphysis. The valgus deformity was still at 21° from normal. At 14 days postoperative, the bird was still limping on the left leg with no visually apparent correction of the valgus deformity. The implants were removed, and the limp improved within hours of recovery. Eventually the left tarsometatarsal valgus deformity improved visually, although currently mild valgus deviation appears present.

Case 4

A Chilean flamingo presented at 62 days of age with a valgus limb deformity of the left proximal tarsometatarsus. Radiographs revealed a 17° from normal valgus deformity of the proximal tarsometatarsus. Transphyseal bridging was performed using a Jacobs hand chuck to place the two 0.03-mm positive profile pins, and 28-ga cerclage wire was placed in a figure-eight pattern for tension. Three days postoperative, two orthodontic rubber bands were placed around the pins. Radiographs at 7 days postoperative revealed a decrease to 4° from normal valgus deformity. At this point, the chick was slightly lame, and some swelling was noted in the foot. Radiographs at 9 days postoperative revealed an overcorrection to a 4° from normal varus deformity. The apparatus was removed, the lameness resolved, and the leg remained clinically straight.

Discussion

Angular limb deformities commonly occur in hand-raised, long-legged birds.⁸ The etiology of the deformity is rarely elucidated. In ratites, angular limb deformities have been associated with high planes of nutrition, lack of exercise, trauma, and genetics.⁶ In cranes, leg problems may result from the same etiologies, as well as management practices including incubation temperatures, hatching and rearing substrates, nutrition, ambient temperature, illumination, external stimuli and exercise.³ Angular limb deformities of clinical significance left untreated may produce irreparable limb misalignment that may lead to joint abnormalities, muscle contracture, and ulcerative pododermatitis.⁷

Medical management of angular limb deformities of long-legged avian species includes increasing exercise, slowing weight gain, correcting nutritional deficiencies, swimming or hydrotherapy, and bandaging or hobbling the legs into a more normal orientation.^2,7,8 Surgical procedures reported to address angular limb deformities include hemi-circumferential periosteal stripping and dome osteotomy techniques.^6-8 Periosteal stripping procedure was not elected due to the minimal amount of soft tissue present for closure over the tarsometatarsal bone. Dome osteotomy was not elected due to the technique requirement of fracturing the affected bone for realignment and the immature age of the affected flamingos in this report.⁷ The use of transphyseal bridging has been reported in foals and calves, but not to date in avian species.

Transphyseal bridging is a tension band technique that retards bone growth at the physis of the convex side allowing lengthening of the bone on the concave side to straighten the leg.⁵ In foals, retardation of growth on the convex aspect of the deformity is consistently effective in correction of angular limb deformities and can be performed using several different systems of implants.⁵ In this instance, due to the size of the four flamingos and their very small proximal tarsometatarsal epiphyses (radiographic measurements ranged from 3–4 mm), small diameter positive profile pins were used to engage soft epiphyseal bone and cortical bone of the metaphysis with minimal disruption of the physeal growth plate.

Methods to create tension were different in each case. Initially 23-ga orthopedic wire in a figure-eight pattern was used. The small-gauge orthopedic wire was difficult to manipulate to create the desired amount of tension. Orthodontic rubber bands created constant dynamic tension as long as they were changed every 3–4 days to ensure limited elasticity. Clinical results were not as rapid with rubber bands alone; therefore, commercial-grade twist-ties were added in a figure-eight pattern. This media tended to be much more pliable than cerclage wire. Based on the results from these limited cases and length of time for improvement in each case, small-gauge (≤25) orthopedic cerclage wire, or alternatively a commercial-grade twist-tie, is recommended to create the initial non-elastic tension on the 0.03-mm positive profile pins during the growth phase of the bone. At 3–4 days postoperative, the addition of orthodontic rubber bands appears warranted to maintain constant dynamic tension on the pins. These bands should be changed once to twice weekly.

The age of chicks when a tension band apparatus is placed may also be an important consideration. In a study of greater flamingo (Phoenicopterus rubber roseus) chicks at the Basle Zoo, females reached about 90% of their adult tarsus length, and male fledglings 80% of their adult tarsus length, at 90–120 days of age.⁹ Therefore, in these young, rapidly growing chicks, early correction would be necessary to prevent further abnormal growth and the resulting chronic orthopedic problems described in adults. It is doubtful that transphyseal bridging would have been successful after 90–120 days of age when their tarsometatarsus growth is nearly complete.

Case 3 was considered unsuccessful, although there was some improvement in the valgus deformity over time once the implant was removed. On postoperative radiographs, the proximal pin was not centered in the small epiphyseal bone. Due to decreased bone and increased cartilage engaged, the pin was unstable, and migration was evident on serial radiographs over 14 days. This also appeared to be causing pain, manifested as the clinical lameness observed. Improper pin placement appears to be at least part of the cause for failure, and it illustrates the importance of exact pin placement in the small epiphysis of this avian species.

Very few surgical options for angular limb deformities have been described in the literature for long-legged avian species. To the authors’ knowledge, this is the first reported use of transphyseal bridging in avian species. The procedure appears to be safe, minimally invasive, and was reasonably well tolerated. The success of transphyseal bridging-induced growth plate retardation appears encouraging based on the outcome in three of the four cases reported. Transphyseal bridging appears to be a viable surgical option to accelerate or affect the correction of proximal tarsometatarsal valgus angular limb deformities in young flamingo chicks.

Acknowledgments

We thank Dr. Gary West for contribution of one of the cases and Dr. John Hoover for manuscript review. We thank the bird departments of the Tulsa and Oklahoma City zoos for their help with these cases.

Literature Cited

1.  Auer, J.A. 1992. Angular limb deformities. In: Auer, J.A. (ed): Equine Surgery. W.B. Saunders Co., Philadelphia, PA. Pp. 940–956.

2.  Carpenter, J.W. 2003. Cranes. In: Fowler M.E. and R.E. Miller (eds): Zoo and Wildlife Medicine, 5th ed. W.B. Saunders Co., Philadelphia, PA. Pp. 177.

3.  Carpenter, J.W. 1986. Cranes. In: Fowler M.E. (ed): Zoo and Wildlife Medicine, 2nd ed. W.B. Saunders Co., Philadelphia, PA. Pp. 321–322.

4.  Egger, E.L. 1993. Fractures of the radius and ulna. In: Slatter, D. (ed): Textbook of Small Animal Surgery. W.B. Saunders Co., Philadelphia, PA. Pp. 1746–1757.

5.  Fackelman, G.E. 1984. Deformities of the appendicular skeleton. In: Jennings P.B. (ed): The Practice of Large Animal Surgery. W.B. Saunders Co., Philadelphia, PA. Pp. 950–957.

6.  Gnad, D., G. St. Jean, L.D. Homco, and C. Honnas. 1996. A review of some orthopedic diseases in ostriches, emus and rheas. Agri-Practice. 17 (10): 28–32.

7.  Greenacre, C.B., D.N. Aron, and B.W. Ritchie. 1994. Dome osteotomy for successful correction of angular limb deformities. Proc. Annu. Conf. Assoc. Avian Vet. 1994: 39–43.

8.  Kirkwood, J.K. 2000. Twisting and bending deformities of the long bones in growing birds. In: Samour, J. (ed): Avian Medicine. Harcourt Publishers Limited. London, England. Pp: 173–177.

9.  Studer-Thiersch, A. 2000. What 19 years of observation on captive greater flamingos suggests about adaptations to breeding under irregular conditions. Waterbirds. 23: 150–159.