Trauma-Induced Aneurysmal Bone Cysts in Two Psittacine Species (Cacatua Alba and Nymphicus Hollandicus)

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TRAUMA-INDUCED ANEURYSMAL BONE CYSTS IN TWO PSITTACINE SPECIES (CACATUA ALBA AND NYMPHICUS HOLLANDICUS)

J. Jill Heatley, D.V.M., M.S., Dipl. A.B.V.P. (Avian), Thomas N. Tully, Jr., D.V.M., M.S. Dipl. A.B.V.P. (Avian), Dipl. E.C.A.M.S., Mark A. Mitchell, D.V.M., Ph.D., Beth P. Partington, D.V.M., M.S., Dipl., A.C.V.R. and H. Wayne Taylor, D.V.M., Ph.D., Dipl. A.C.V.P.

Abstract: An umbrella cockatoo (Cacatua alba) and two cockatiels (Nymphicus hollandicus) were presented with rapidly enlarging masses of the head or wing joints. Historic trauma to these areas was con®rmed in two cases. All birds were Ͼ2 yr of age, and two were female. Cytologic examination of ¯uid aspirated from masses in two cases was described as serosanguineous cytologically but failed to reveal in¯ammation, neoplasia, or microorganisms. Radio- graphic evaluation of these masses included proliferation and lysis of bone, suggestive of a neoplastic process. Histo- pathologic examination of surgically excised tissues revealed proliferative new bone and an absence of neoplastic tissue in all cases, consistent with aneurysmal bone cyst formation. Despite the guarded prognosis reported for other com- panion animals, these case results suggest a good prognosis for aneurysmal bone cyst in psittaciformes. Complete surgical excision and histopathologic examination is recommended for de®nitive diagnoses of aneurysmal bone cyst. Postoperative bandaging and rational antibiotic use are indicated to prevent excessive motion and secondary infection of affected sites, respectively. Key words: Cacatua alba, Nymphicus hollandicus, trauma, aneurysmal bone cyst, psittacine.

INTRODUCTION free-¯ight aviary and offered a free-choice commercial seed mix diet. It was reported that the bird Aneurysmal bone cysts are expansile cortical had ¯own into a window approximately 1 yr before bone lesions likely resulting from anomalous vas- presentation. Physical abnormalities were limited to cular processes of bone marrow. Primary aneurys- a featherless mass (1.0 ϫ 1.0 ϫ 0.25 cm) on the mal bone cysts lack an apparent cause, whereas superior aspect of the cranium, with a hardness secondary bone cysts are associated with an under- consistent with bone and no signs of pain or in¯am- lying disease process such as neoplasia. In humans, mation. Based on the physical examination and the diagnoses of aneurysmal bone cysts are based on size and placement of the mass, a poor prognosis radiographic and histopathologic ®ndings; primary for clinical resolution of the presenting condition therapies include excision with bone grafting.14 An- was given. The bird was then donated to The Lou- eurysmal bone cysts are rare in animals. Although isiana State University Veterinary Teaching Hos- their prognosis in humans is generally good, it is pital for surgical removal of the mass. guarded to grave in domestic animals.3,5,7,16,18,19,21 The bird was anesthetized with iso¯urane (Iso- However, we describe three cases of aneurysmal ¯o௡, iso¯urane USP, Abbott Laboratories, North bone cyst, with favorable outcomes in two psitta- Chicago, Illinois 60064, USA) in oxygen adminis- cine species. tered by face mask. An elliptical skin incision was CASE REPORTS made over the mass, and the skin and subcutis were bluntly dissected free from the underlying mass Case report 1 (Fig. 1). Removal of the super®cial layer of the An adult cockatiel (Nymphicus hollandicus)of mass exposed a cystic structure (Fig. 2) containing unknown sex was presented for a cranial mass, serosanguineous ¯uid, which was aspirated using which had enlarged over a 12-mo period. The bird sterile technique but not cultured. The remaining had been housed with a group of cockatiels in a walls of the bone cyst were debrided to the cranium, which formed the base of the mass (Fig. 3), and were submitted for histopathologic evaluation. From the Departments of Clinical Sciences (Heatley, The skin was closed with a 4-0, synthetic, absorb- Tully, Mitchell, Partington) and Pathobiology (Taylor), able, mono®lament suture (PDS II, Ethicon᭧, Som- School of Veterinary Medicine, Louisiana State Univer- sity, Baton Rouge, Louisiana 70803-8410, USA. Present erville, New Jersey 08876, USA) in a simple inter- address (Heatley): Department of Clinical Sciences, Col- rupted suture pattern (Fig. 4). Histopathologic ®nd- lege of Veterinary Medicine, Auburn University, Alabama ings were consistent with aneurysmal bone cyst. No 36849, USA. Correspondence should be directed to Dr. recurrence of the mass was evident for 24 mo after Heatley. the surgical procedure.

185 186 JOURNAL OF ZOO AND WILDLIFE MEDICINE

Figure 1. Intraoperative elliptical incision exposing the mass on the dorsocaudal aspect of the head of a cockatiel.

Case report 2 metacarpal bones of both wings (Figs. 5, 6). The A 15-yr-old, 95-g female cockatiel was presented distal cortex of each metacarpal bone appeared in- for a featherless, immobile, s.c. nodular mass (1.0 tact, and radiographic interpretation concluded that ϫ 1.0 ϫ 0.5 cm) of 45-day duration on the ventral these ®ndings were consistent with cutaneous ex- left metacarpus. The bird was maintained indoors ostosis. in a standard cockatiel cage and fed a commercial The animal was anesthetized with iso¯urane in seed mix for cockatiels. The owner was concerned oxygen administered by face mask. The left-wing that the mass had enlarged since ®rst detection and mass was biopsied by sharp excision under general now affected the bird's ability to ¯y. On further anesthesia. Postoperatively, doxycycline (Vibra- examination, a similar but smaller mass of 0.5 ϫ mycin SF I.V., P®zer Inc., New York, New York 0.5 ϫ 0.25 cm was noted in the same location on 10017, USA; 50 mg/kg, i.m., once) was adminis- the contralateral wing. Other abnormal ®ndings on tered. Histopathologic ®ndings included in®ltration physical examination were limited to a palpable of the s.c. fat with focal accumulations of well- mass in the caudal coelom, consistent with an egg. differentiated, haphazardly arranged spicules of Initial diagnostics were limited to a complete laminar bone and numerous red blood cells. No his- blood count (CBC) and radiography of the wings. tologic evidence of neoplastic bone formation was Abnormal CBC ®ndings were a mild leukocytosis found, but recent trauma was considered, based on (12,300 cells/␮l, reference range: 5,000±11,000) a lack of in¯ammatory cells in the sections exam- with a heterophilia (10,800 cells/␮l, reference ined. Based on these ®ndings, bilateral surgical cyst range: 2,300±7,000), lymphocytopenia (500 cells/ excision and curettage of the remaining cortices ␮l, reference range: 1,250±6,600), and gross plas- was performed in a second surgery. A ®gure-of- ma that appeared lipemic and yellow.6,9 Abnormal eight bandage was placed on each wing postoper- radiographic ®ndings included extracortical miner- atively, and the owner was instructed to provide alization of the soft tissues associated with the cage rest until reexamination. HEATLEY ET AL.ÐTRAUMATIC BONE CYSTS IN PSITTACIFORMES 187

Figure 2. Exterior shell of the aneurysmal bone cyst of a cockatiel before incision.

At this reexamination and bandage change 7 fore presentation. The owner reported no signs of days postoperatively, complications of s.c. hema- pain associated with the mass but reported that the toma and edema were noted on the ventral left mass had increased in size during a 1-mo period. metacarpus at the surgical site. The right wing had Abnormal physical examination ®ndings were lim- healed without complications. A ®gure-of-eight ited to a 4.0- ϫ 4.0- ϫ 1.0-cm, ®rm, non¯uctuant, bandage was replaced on the left wing only, and unin¯amed mass found on the ventral surface of cage rest was continued for an additional 7 days. the right wing at the humeroradioulnar joint. At reexamination 14 days postsurgically, both The initial diagnostic plan included a CBC, plas- wings had developed healthy granulation tissue at ma biochemical analysis, ®ne-needle aspiration of the incision sites. Bandaging was discontinued, and the mass, and whole-body radiographs. Hematolog- the owner was instructed to apply a light coating ic abnormalities included leukocytosis (20,400 of an over-the-counter multiple antibiotic ointment cells/␮l, reference range: 8,000±16,000 cells/␮l) topically to each site once daily to avoid secondary with a heterophilia (16,300 cells/␮l, reference bacterial infection and to promote reepithelializa- range: 3,600±11,360 cells/␮l), lymphopenia (1,000 tion of the incision sites. The owner failed to return cells/␮l, reference range: 0±320 cells/␮l), mono- for further follow-up care. cytosis (3,100 cells/␮l, reference range: 1,600± 8,160 cells/␮l), anemia (packed cell volume 26%, Case report 3 reference range: 38±48%), an elevated alkaline A 2-yr-old, 604-g umbrella cockatoo (Cacatua phosphatase (218 IU/L, reference range: 38±106), alba) presented for a swelling of 1-mo duration in and a hypouricemia (35.7 ␮mol/L, reference range: the ventral proximal antebrachium of the right 208.2±648.3).1,6,9 Cytologic evaluation of the ®ne- wing. The owner attributed the mass to a fall the needle aspirate of the mass revealed low numbers bird sustained in the cage approximately 3 mo be- of erythrocytes and occasional clusters of smudged 188 JOURNAL OF ZOO AND WILDLIFE MEDICINE

Figure 3. Intraoperative view of the base of the aneurysmal bone cyst formed by the cranium in a cockatiel. nuclei but no evidence of infectious microorgan- dage was applied to the right wing to cover the isms or in¯ammatory or neoplastic cells. surgical site, and enro¯oxacin (Baytril, 11.3 mg/ml Radiographic examination included ventrodorsal suspension, compounded from tablets by Louisiana and lateral views of the whole body and ventro- State University Pharmacy, Bayer Corp., Shawnee dorsal and anterior±posterior views of the right Mission, Kansas 66201, USA; 15 mg/kg, p.o., b.i.d. wing. The only abnormality found on radiographs for 10 days) was administered. Histopathologic ex- was a severely osteolytic and mildly osteoprolifer- amination of the submitted tissue indicated no ev- ative lesion in the proximal aspect of the radius idence of neoplasia, but extensive connective tissue surrounded by a soft tissue mass containing mineral was evident with foci of new bone formation. His- density (Figs. 7, 8). This was initially interpreted topathologic interpretation suggested callus forma- as an aggressive neoplasm. Primary differential di- tion or other causes of nonneoplastic bone produc- agnoses for this lesion were neoplasms of subcu- tion, such as a bone cyst. taneous, muscle, or bone tissue. However, infec- Based on these histopathologic ®ndings, the tious etiologies, especially those of bacterial or fun- mass was surgically removed from the medial as- gal origin, and noninfectious processes such as a pect of the right wing. The bird was admitted for bone cyst or abnormal callus formation were in- surgery, and anesthesia was induced and main- cluded in the differential diagnoses. tained as previously described. A ventral skin in- In preparation for surgical biopsy, the animal cision revealed a thin (2 mm) osseous shell sur- was anesthetized with iso¯urane in oxygen admin- rounding the mass. Because of the extensive nature istered by face mask. Three 5-mm incisional biop- of the lesion, partial resection of the affected tissue sies were collected from the ventral aspect of the was performed. The mass contained a serosanguin- mass by sharp excision and submitted for histo- eous ¯uid, which was collected intraoperatively by pathologic examination. Grossly, the mass was aspiration and submitted for aerobic microbial cul- ®rm, relatively immobile, and varied in color from ture. Anesthetic recovery was uneventful. Butor- red to tan. Postoperatively, a ®gure-of-eight ban- phanol (Torbugesic, butorphanol tartrate, 10 mg/ml, HEATLEY ET AL.ÐTRAUMATIC BONE CYSTS IN PSITTACIFORMES 189

Figure 4. Postoperative view of a cockatiel after excision of an aneurysmal bone cyst of the cranium.

Fort Dodge Animal Health, Fort Dodge, Iowa graphic interpretation attributed radial absence as 50501, USA; 2 mg/kg, i.m.) was administered once well as gas within the tissues to surgical interven- postoperatively for analgesia, and enro¯oxacin ad- tion, although bacterial, fungal, or neoplastic eti- ministration was continued at the same dosage reg- ologies could not be ruled out. Radiographic ®nd- imen for an additional 10 days. A ®gure-of-eight ings suggested the presence of a primary bone tu- bandage was placed over the surgical site, and the mor such as osteosarcoma, chondrosarcoma, or ®- animal was discharged 1 day postoperatively. One brosarcoma, and wing amputation was recommended. week later, the cockatoo was readmitted for surgery Differential diagnoses considered for the abnormal to remove the remaining bony mass from the dorsal radial ®ndings included disuse demineralization, aspect of the wing. Anesthesia, surgical techniques, devitalized bone or sequestration due to surgical in- and intraoperative ®ndings were similar to the pre- tervention, or traumatic, infectious, or neoplastic pro- vious surgery. The surgical approach was modi®ed cesses. to access to the dorsal aspect of the wing. Grossly, Based on the radiographic ®ndings, the animal the mass appeared as a 3-cm-diameter ovoid shell, was returned to surgery, and the proximal remain- surrounding soft friable tissue. ing 4.0 cm of the radius was resected and submitted Postoperative radiographs included ventrodorsal for histopathologic examination. Grossly, the resec- and anterior±posterior views of the affected wing tus had a 6.0-mm, ®rm red mass at the proximal (Figs. 9, 10). A 3.0- ϫ 4.0- ϫ 1.0-cm soft tissue end. Butorphanol (1.5 mg/kg, i.m.) was adminis- mass containing multiple radiolucent areas consis- tered once for pain control postoperatively, and a tent with gas density was now visible distal and ®gure-of-eight bandage was placed to immobilize dorsal to the cubital joint. Although the entire prox- the wing. Microbial culture of the serosanguineous imal radial diaphysis and metaphysis were absent, ¯uid obtained in the initial surgery produced a pure the remaining proximal radial diaphysis was scle- culture of small numbers of Corynebacterium ren- rotic with permeative osteolysis and mild periosteal ale, resistant to ¯uoroquinolones but sensitive to proliferation. The substantially demineralized radial sulfonamides. Based on microbial culture and an- head was faintly radiographically apparent. Radio- timicrobial sensitivity testing, oral antibiotic admin- 190 JOURNAL OF ZOO AND WILDLIFE MEDICINE

Figure 5. Ventrodorsal radiographic view of the affected distal left metacarpus of an adult cockatiel with an aneurysmal bone cyst. istration was changed to trimethoprim sulfameth- The bird had gained weight 7 days postopera- oxazole (Sulfatrim Pediatric Suspension, sulfameth- tively and had a good appetite and normal elimi- oxazole and trimethoprim oral suspension 200/40 nations. The bandage was intact and without swell- mg per 5 ml; Alpharma USPD Inc., Baltimore, ing of the wing or apparent discomfort. The ban- Maryland 21244, USA; 100 mg/kg, p.o., b.i.d.). dage was removed, and antibiotic use was discon- Histopathologic examination of the radial frag- tinued 2 wk postoperatively. The owner was ment revealed granulation tissue with cartilage and instructed to perform passive range of motion ex- bone production. Foci of bone lysis and hemor- ercises on the wing to restore function and to re- rhage were present along with periosteal prolifera- lease carpal contracture. Approximately 2 mo after tion in the cortex adjacent to the proximal radial the second postoperative examination, the animal mass. The lesion was consistent with a posttrau- returned for the unrelated complaint of hemorrhage matic callus. The second mass was sectioned so that from a developing feather. At this time, the owner the ``shell'' and central tissue could be assessed reported no problems with the surgical site, and the separately. Histopathologically, the outer wall of wing had full return to function. the mass was composed of immature ®brous bone trabeculae with intense osteoclastic activity, where- DISCUSSION as the central tissue was composed of ®brin and Aneurysmal bone cysts are benign, lytic, expan- packed erythrocytes. Collectively, this was inter- sile lesions of bone consisting of anastomosing cav- preted as a cyst, which likely occurred as a result ernous spaces ®lled with unclotted blood, ®brous of bone marrow hemorrhage and hematoma for- tissue and, usually, osseous components.2 These mation with substantial bone remodeling. No evi- cysts are named for the distended contour of the dence of neoplasia was found in any examined tis- affected bone cortices seen radiographically.11 The sue, and the ®nal morphologic diagnosis was an- de®nitive pathogenesis of these lesions remains un- eurysmal bone cyst. clear, but histopathologic descriptions support the HEATLEY ET AL.ÐTRAUMATIC BONE CYSTS IN PSITTACIFORMES 191

Figure 6. Ventrodorsal radiographic view of the affected distal right metacarpus of an adult cockatiel with an aneurysmal bone cyst. concept that aneurysmal bone cysts may result cinoma.11 In domestic animals, osteosarcoma has when trauma or tumor induces an anomalous vas- been associated with aneurysmal bone cyst,7 where- cular process of the bone marrow.11 The hemody- as trauma has been postulated as a causative factor namic force of this marrow vascular abnormality in other cases.15 creates a progressively expanding and thinning cor- In studies of human cases of aneurysmal bone tex of bone ®lled with blood. Thus, aneurysmal cysts, the incidence is low (0.00014%), with young bone cysts appear to be a manifestation of a path- adult females most commonly affected.11,13,14 In do- ophysiologic change rather than the result of a sin- mestic animals, rare reports document aneurysmal gle etiologic entity. Aneurysmal bone cysts have bone cyst, in both sexes and in both mature and been extensively described in humans but are rarely immature animals.5,15,16,21 In humans, aneurysmal reported in domestic animals.3±5,11,15 bone cysts most often affect the long bones, spine, The majority of aneurysmal bone cysts in hu- and pelvic bones.11 In humans and animals, the me- mans occur as primary lesions in which a preexist- taphyseal regions of bone are most often affected.5 ing cause cannot be identi®ed and are termed pri- In these psittacine cases, two of the birds were fe- mary aneurysmal bone cysts.14 However, approxi- male, and all were Ͼ2 yr of age. Areas prone to mately 30% of human bone cysts reported are as- trauma, such as the superior cranium, distal wing sociated with a preexisting bone lesion and are tips, and the anconeal joint, appeared to be a com- termed secondary aneurysmal bone cysts.11,14 Doc- mon factor in these avian cases. umented precursor lesions in humans most com- Most human cases of primary aneurysmal bone monly include giant cell tumor, followed by ®brous cyst have pain with or without swelling and symp- or osseous neoplasia, eosinophilic granuloma, ra- tom duration of Ͻ6 mo.11 In domestic animals, pro- diation osteitis, trauma (fracture), or metastatic car- gressively enlarging, nonin¯amed masses of 2-wk 192 JOURNAL OF ZOO AND WILDLIFE MEDICINE

Figure 7. Ventrodorsal radiographic view of the affected left wing of an umbrella cockatoo with an aneurysmal bone cyst. to 5-mo duration with or without lameness or pain clude osteosarcoma, osteoma, ®brosarcoma, chon- on palpation have been reported.3,4,7,15,18,20 Patholog- drosarcoma, osteoblastic or giant cell tumor, hem- ic bone fracture secondary to an aneurysmal bone angioma, and hemangiosarcoma.3,7,12,15±19,21 Second- cyst is not uncommon in humans and occurs in do- ary neoplastic processes affecting bone for consid- mestic animals. These cases may present with acute eration as differentials include solitary plasma cell lameness or, in cases where vertebrae are affected, myeloma or multiple myeloma and lymphosarco- have neurologic dysfunction.11,16,18,19 Abnormal clin- ma.7,19 Dysplastic differentials include unicameral ical signs in these case reports were limited to non- bone cysts and ®brous dysplasia.12,15,16,18,20,21 Al- painful, non¯uctuant, nonin¯amed, and rapidly though histopathologic examination was performed growing masses on the affected areas. in all cases reported here, no primary neoplastic De®nitive diagnosis of aneurysmal bone cyst is lesion was identi®ed. dependent on appropriate radiographic lesions and Although CBC, plasma biochemistries, and cy- biopsy.5 Accordingly, differential diagnoses extend tologic ®ndings supported the diagnosis of aneu- primarily from radiographic and pathologic ®nd- rysmal bone cyst in these cases, clinicopathologic ings. Patient age and lesion location should also ®ndings could not rule out in¯ammatory processes in¯uence the consideration of differential diagno- including neoplastic and infectious etiologies. In ses.19 Differentials for these osteolytic lesions the cockatoo, elevated alkaline phosphatase levels should include infectious, neoplastic, in¯ammatory, were supportive of bone activity or damage.8 Low traumatic, and dysplastic processes. Neoplastic dif- numbers of C. renale in the ®rst surgical resectus ferentials can be subdivided into primary bone tu- of this case could have indicated infection or mere- mors and secondary neoplastic processes affecting ly contamination. Although this organism is con- bone. Primary bone tumors for consideration in- sidered autochthonous ¯ora in avian species and HEATLEY ET AL.ÐTRAUMATIC BONE CYSTS IN PSITTACIFORMES 193

Figure 8. Lateral radiographic view of the affected left wing of an umbrella cockatoo with an aneurysmal bone cyst. none of Corynebacterium spp. isolated from birds tour of bone resulting from bone production of the have been found to be pathogenic,10 antimicrobial periosteum. The lesions tend to be eccentric in long sensitivity testing and corresponding antibacterial bones but may appear more centrally located or ®ll therapy, were instituted. Microbiologic sampling, the entirety of shorter bones. Although cyst margins antimicrobial sensitivity testing, and antimicrobial may be sclerotic and well de®ned, ¯occulent den- administration are indicated in aneurysmal bone sities or faint mineralization may also be radio- cyst cases because the serosanguineous ¯uid often graphically evident within the lesion. Although ra- contained in these cysts provides an excellent me- diographic ®ndings in all three psittacine cases dium for bacterial growth. Although antimicrobial were consistent with aneurysmal bone cyst, diag- testing was not performed in the cockatiels because nosis was hindered in the cockatoo, where radio- of client constraints, antimicrobial therapy was em- graphic ®ndings suggested an aggressive neoplastic pirically instituted. process. However, radiographic ®ndings in the sec- In human cases of secondary aneurysmal bone ond cockatiel were interpreted as consistent with cyst, most lesions have the radiographic appearance the tentative diagnosis of bone cyst, likely due to typical of the causative condition.11 In cases of pri- previous radiologic experience with similar lesions. mary aneurysmal bone cyst, radiographic evalua- Although clinicopathologic and radiographic ®nd- tion will demonstrate an eccentric, lytic lesion with ings may be supportive of aneurysmal bone cyst, an expansive remodeled or ballooned cortical con- the rarity of aneurysmal bone cysts in domestic an- 194 JOURNAL OF ZOO AND WILDLIFE MEDICINE

Figure 9. Ventrodorsal radiographic view of the affected left wing of an umbrella cockatoo after aneurysmal bone cyst resection and partial radial resection. imals and humans precludes de®nitive diagnosis In the case of secondary aneurysmal bone cyst, without histopathologic evaluation of affected tis- the causative agent, usually a neoplasia, must be sues. treated appropriately.11 In the case of a primary an- Histologically, the aneurysmal bone cyst is de- eurysmal bone cyst, treatment options are based on ®ned as ``an expanding osteolytic lesion consisting techniques to reduce blood supply to the lesion. of blood ®lled spaces of variable size that are sep- Historic treatments include complete surgical ex- arated by connective tissue septa containing trabec- cision, curettage with or without subsequent bone ulae of bone or osteoid tissue and osteoclast giant graft, radiotherapy, cryotherapy, phenol, or packing cells.''13 Histopathologic diagnosis is obtained more with polymethylmethacrylate, or, more recently, readily when material from the sinus portion is in- embolotherapy.5,7,11,17 Although effective in treat- cluded in the biopsy.5 An open biopsy technique is ment of aneurysmal bone cysts, radiation therapy preferred to obtain suf®cient sample for diagnosis is contraindicated because of risk of delayed sec- and reduce the risk of damage to adjacent neural ondary sarcoma.17 In primary lesions, curettage and and vascular structures.5 The cockatoo case report bone grafts are performed ®rst with surgical re- illustrates that multiple histopathologic evaluations moval or other more involved treatments reserved of the mass may be necessary to obtain the diag- for recurrent lesions, or lesions that are nonresect- nosis of aneurysmal bone cyst. The cockatiel case able.11 In domestic animal cases of primary aneu- reports demonstrate that in some birds, size may rysmal bone cyst, only complete surgical excision limit the possible number of biopsies or other di- or surgical curettage and cancellous bone grafting agnostics possible. Complete excisional biopsy may have achieved successful outcomes.4,7 be the primary diagnostic procedure indicated when Most domestic animals with aneurysmal bone bone cyst is suspected in the smaller (Ͻ100gof cyst are euthanized because of a poor prognosis as- body weight) avian cases. Surgical resection of the sociated with appendage dysfunction, neurologic mass in toto is the most practical diagnostic and dysfunction, suspicion of neoplasia, or likelihood of treatment option in these cases. lesion recurrence.3,5,7,16,18,19,21 In contrast, most cases HEATLEY ET AL.ÐTRAUMATIC BONE CYSTS IN PSITTACIFORMES 195

Figure 10. Anterior±posterior radiographic view of the affected left wing of an umbrella cockatoo after aneurysmal bone cyst resection and partial radial resection.

of primary aneurysmal bone cyst in humans carry Acknowledgment: We acknowledge the permis- a good prognosis although recurrence is possi- sion of Harrison's Bird Diets International Inc. for ble.11,17 These are the ®rst documented cases of psit- use of Figure 1, which was originally published in tacine aneurysmal bone cysts. Surgical resection of Avian Medicine: Principles and Application. the cysts and associated bone resulted in positive LITERATURE CITED outcomes, with minimal postsurgical complications. 1. Altman, R., S. Clubb, G. Dorrestein, and K. Que- Postoperative complications were likely related senberry. 1997. Table 2: Plasma biochemical reference ranges of common psittacine species. In: Altman, R., S. to bandage application and the inherent motion and Clubb, G. Dorrestein, and K. Quesenberry (eds.). Avian likelihood of trauma to these areas. Speci®c com- Medicine & Surgery. W. B. Saunders Co., Philadelphia, plications were limited to swelling, birds' trauma Pennsylvania. Pp. 1006±1007. to the bandage, carpal contracture in a cockatiel and 2. Baxter, G. 1996. Subchondral cystic lesions in hors- the cockatoo, and hematoma formation in the same es. In: McIlwraith, C. W. (ed.). Joint Disease. W. B. Saun- cockatiel. In all three cases, further radiographic ders Co., Philadelphia, Pennsylvania. Pp. 384±397. evaluation was indicated to rule out further bone 3. Belknap, E., S. Brodie, J. Lowry, and R. Getzelmen. cyst formation. Additional clinicopathologic anal- 1992. Aneurysmal bone cyst in a holstein bull. J. Am. ysis is also recommended in these cases, dependent Vet. Med. Assoc. 201: 1413±1415. on bird size, to assess resolution of abnormal ®nd- 4. Biller, D., G. Johnson, S. Birchard, and R. Fingland. 1987. Aneurysmal bone cyst in a rib of a cat. J. Am. Vet. ings. Additional diagnostics for the cases described Med. Assoc. 190: 1195. in this report were declined. Positive outcome of 5. Bowles, M. H., and K. Freeman. 1986. Aneurysmal the described cases may have contributed to poor bone cyst in the ischia and pubes of a dog: a case report client compliance for recommended continuing re- and literature review. J. Am. Anim. Hosp. Assoc. 23: 423± examinations. 427. 196 JOURNAL OF ZOO AND WILDLIFE MEDICINE

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