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A 2-year-old alpaca was presented for acute onset right forelimb lameness. Clinical findings included bilateral carpal valgus (more severe in the affected forelimb) and medial instability of the right radio-carpal joint. Surgical treatment consisted of radio-carpal joint arthrodesis, which is presented as a therapeutic option for severe carpal instability secondary to injury to the supporting ligamentous structures of the carpus.
Arthrodèse carpienne partielle chez un alpaca âgé de 2 ans. Un alpaca de 2 ans est présenté pour l’apparition aiguë de boiterie de la jambe avant droite. Les résultats cliniques ont inclus le valgus carpien bilatéral (plus grave dans la jambe avant touchée) et l’instabilité médiale de l’articulation radio-carpienne droite. Le traitement chirurgical comporte l’athrodèse de l’articulation radio-carpienne, qui est présentée comme une option thérapeutique pour une instabilité carpienne grave causée par une blessure aux structures ligamenteuses de support du carpe.
(Traduit par Isabelle Vallières)
A 2-year-old intact adult male alpaca was presented to the Boren Veterinary Medical Teaching Hospital at Oklahoma State University with a history of an acute onset severe lameness affecting the right forelimb for the past 7 d. The alpaca was kept in a paddock with other herd-mates. No traumatic event had been witnessed by the owner. The owner reported that the alpaca had been born after a normal length of gestation without any post-partum orthopedic problems being noted. Mild bilateral carpal valgus had been present since birth.
On presentation the alpaca was found to be in good body condition. All vital parameters were within normal limits. The alpaca exhibited a marked lameness at the walk in the right forelimb. Bilateral carpal valgus was observed, being more severe in the lame forelimb. Carpal hyperextension was also noted in the affected limb. Manipulation of the right forelimb revealed that the carpal valgus was correctable and that there was medial joint instability.
Radiographic examination of both forelimbs revealed approximately 12° of carpal valgus deviation in the right limb and 7° in the left. In the right forelimb, radio-carpal joint instability was demonstrable radiographically as a widening of the joint space medially (Figure 1a) and palmarly (Figure 1b). The clinical presentation, physical findings and radiographic signs were consistent with severe injury to the ligmentous structures supporting the carpus, specifically the medial collateral and palmar carpal ligaments. Based on the severity of the valgus deformity in the right forelimb, the observed carpal instability and the degree of lameness, surgical arthrodesis of the right radio-carpal joint was elected.
Peri-operative medications including ceftiofur (Naxcel; Pfizer and Upjohn, Division of Pfizer, New York, New York, USA), 2.2 mg/kg, IV, q12h, and ketoprofen (Ketofen, Fort Dodge Animal Health, Fort Dodge, Iowa, USA), 2.2 mg/kg, IV, q24h, were administered prior to surgery. Pre-anesthetic medications of butorphanol (Torbugesic, Fort Dodge Animal Health), 0.2 mg/kg, IV, and midazolam (Baxter Healthcare, Deerfield, Illinois, USA), 0.1 mg/kg, IV, were given followed by the induction of general anesthesia with propofol (PropoFlo, Abbott Laboratories, Chicago, Illinois, USA), 8 mg/kg, IV. Oral endotracheal intubation was performed using a No. 10 French cuffed endotracheal tube (Surgivet, Smiths Medical North America, Wakesha, Wisconsin, USA) and general anesthesia was maintained with isofluorane vaporized in 100% oxygen. Respiration was maintained with a mechanical ventilator.
The alpaca was placed in right lateral recumbency and the right forelimb was clipped from the elbow to the digital region and aseptically prepared for surgery. A 15-cm incision was made on the dorsal aspect of the distal radius and carpus. The incision was located between the tendons of the extensor carpi radialis and the extensor digitorum communis muscles. The radio-carpal joint capsule was incised, and the articular cartilage of the distal radius and proximal radial, intermediate, and ulnar carpal bones was removed with a pneumatic burr.
The valgus deformity was reduced manually and a 7-hole T-plate was applied to maintain the alignment of the distal limb with the radius. Cortical bone screws 4.5 mm in diameter were used to secure the plate to the radius and radial, intermediate and accessory carpal bones respectively (Figure 2). Screw placement and axial alignment of the limb was checked intra-operatively under fluoroscopic guidance. The surgical wound was closed with 2-0 polydioxanone in the subcutaneous layer and skin in simple interrupted and interrupted cruciate pattern, respectively. A full-limb fiberglass cast was applied prior to recovery from anesthesia. An additional analgesic regimen, consisting of a constant rate infusion (CRI) of fentanyl (Hospira, Lake forest, Illinois, USA), 1 μg/kg/h, and ketamine (KetaThesia, butler animal Health supply, Dublin, Ohio, USA), 0.25 mg/kg/h, was initiated intra-operatively. The CRI was administered for 8 d after surgery.
A post-operative radiographic examination revealed appropriate axial alignment of the limb (Figure 3). External coaptation, consisting of a fiberglass cast, was maintained for 9 wk after surgery with replacement of the initial cast after 4 wk. The orthopedic implants (T-plate and screws) were removed 9 wk after surgery. Implants were removed because the distal aspect of the T-plate was impinging on the middle carpal joint. Implant removal would circumvent degenerative changes and pain emanating from this joint. Subsequent radiographic examinations revealed bridging callus of the radio-carpal joint and obliteration of the radio-carpal joint space. Arthrodesis of the radio-carpal joint and correct axial alignment was evident at the 9 mo post-operative radiographic examination (Figure 3).
A 9-month clinical examination revealed that the alpaca was bearing full weight on the right limb at the walk. No medial to lateral carpal instability could be detected. The carpus was also rigid in the cranio-caudal direction, and minimal flexion of the carpus could be obtained with a manual range of motion assessment.
No deterioration in the degree of mild carpal valgus present in the contralateral forelimb was observed. The alpaca was otherwise in good health and according to the owner roamed freely in a pasture of several acres.
The lameness in this animal was the result of instability of the radio-carpal joint resulting from suspected rupture of the medial collateral and palmar carpal ligaments. The carpal valgus deformity could be manually corrected, and there was no evidence of metaphyseal or epiphyseal dysplasia of the distal radius and ulna. Valgus deformities have been reported to be correctable by growth retardation procedures in camelids < 12 mo old (1–3). The carpal deformity in this animal was acute in onset and was unlikely to be associated with aberrant limb development.
The medial collateral ligament is a substantial support structure of the carpus, and damage to it has been previously documented in llamas (2). Injury to the palmar carpal ligament in camelids does not appear to have been described. The exact nature of the soft tissue injuries sustained in this case remains conjecture as appropriate diagnostic imaging of the affected soft tissues was not carried out. Ultrasonography or magnetic resonance imaging (MRI), if available, would have been useful to demonstrate the nature of these injuries.
Based primarily on experiences with equine orthopedic patients, the authors were surprised by the degree of comfort exhibited by this alpaca while in a full limb cast. This observation contrasts with the findings of a recent retrospective case series in which the use of casts in camelids was associated with a high rate of soft tissue complications (4). In this case, a long period of external coaptation use, which allowed the affected carpal ligamentous structures time to heal, may have contributed to the significant reduction in the range of motion of the middle carpal joint. This complication may have been exacerbated by the impingement of the T-plate on the middle carpal joint resulting in peri-articular fibrosis. In retrospect, a shorter period of cast-immobilization followed by a Robert-Jones bandage may have resulted in a more functional middle carpal joint.
Partial carpal arthrodesis was elected in order to stabilize the affected radio-carpal joint thereby allowing pain-free ambulation. Wedge ostectomy has been previously described for correction of severe carpal valgus in an 18-month-old llama (3). This procedure may have resulted in correction of the valgus deformity but would not have alleviated the carpal instability and subsequent development of degenerative joint disease in the affected radio-carpal joint. The surgical treatment instituted in this case was successful in achieving both of these goals. The clinical outcome reported here is consistent with a previous clinical report describing arthrodesis of the metatarsophalangeal joint for severe chronic valgus deformity in mature llamas (5). CVJ
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