Treatment of recurrent luxation of the shoulder in an alpaca

LUXATION of the shoulder is an uncommon condition in large animals (Semevolos and others 1998), and has not pre-viously been reported in alpacas. Alpacas are raised primarily as companion animals, and have similar orthopaedic prob-lems to cattle. The mild temperament and relatively small body size of these animals make them excellent candidates for the treatment of orthopaedic problems (Kaneps 1996).This short communication describes the clinical presenta-tion and surgical treatment of recurrent lateral luxation of the shoulder in an alpaca by greater tubercle osteotomy and bicipital tendon transposition, using a technique previously described in dogs (Hohn and others 1971, Piermattei 1997, Engen 1998, Talcott and Vasseur 2003).A four-year-old male alpaca, bodyweight 60 kg, had a history of recurrent luxation of the shoulder. The initial lux-ation had occurred seven months previously, after a fight with another male alpaca. The luxated joint was easily reduced under sedation using 6 mg (0·1 mg/kg) xylazine (Rompun; Bayer), and the animal was reported be sound between each episode.On examination, the alpaca did not show any lameness at the walk, and manipulation of the shoulder was not resented in extension or flexion. There was no swelling or thickening of the soft tissues. Lateral luxation was easily induced manu-ally, resulting in a non-weight-bearing lameness, but any lux-ation could be easily reduced without sedation. Craniocaudal and lateromedial radiographs of the shoulder were taken in sternal and lateral recumbency, respectively. There were no visible osteoarthritic or other changes affecting the shoulder joint with the joint reduced.The alpaca was not allowed food for 24 hours before surgery, and water was withheld for at least eight hours. After place-ment of a 14 G catheter into the right jugular vein (Intraflon 2; Vygon), 6 mg xylazine was administered intravenously to sedate the animal. Anaesthesia was induced with 140 mg (2·3 mg/kg) ketamine (Ketaset; Fort Dodge Animal Health) and 5 mg (0·08 mg/kg) diazepam (Diazepam; Hameln Pharmaceuticals), administered intravenously. The alpaca became recumbent, but needed additional increments of ket-amine, as well as the local application of lidocaine (Xylocaine Spray; Astra) on to the larynx, to facilitate intubation of the trachea using a cuffed endotracheal tube with an inter-nal diameter of 7·5 mm. Anaesthesia was maintained with sevoflurane (SevoFlo; Abbott) in 100 per cent oxygen, admin-istered via a small animal circle breathing system. Flunixin (60 mg) (Meflosyl; Fort Dodge Animal Health) and 6 mg morphine (Morphine Sulfate; Celltech) were administered 10 ml/kg/hour Hartmann’s solution intravenously through-out the period of anaesthesia.The alpaca was positioned in right lateral recumbency. After the usual aseptic precautions, a craniolateral para-humeral incision was made, beginning 6 cm dorsal to the shoulder joint and extending to a point midway down the humeral shaft. The skin and subcutaneous tissues were then reflected, and the lateral border of the brachiocephalic mus-cle was retracted medially, exposing the cranial aspect of the proximal humerus and the insertions of the supraspinatus, deltoid and superficial and deep pectoral muscles (Fig 1). The insertion of the superficial pectoral muscle was transected. The tissues over the bicipital groove and the intertubercular ligament were incised. The biceps tendon was freed from the surrounding fascia by blunt dissection proximally, and the muscle body was separated from surrounding tissue distally.Two holes were drilled through the greater tubercle, 1·5 cm apart, using a 2 mm drill bit perpendicular to the humerus axis, exiting on its medioproximal aspect. The glid-ing holes were enlarged with a 3·5 drill bit to a depth of 1·5 cm. The pilot hole was drilled with a 2·5 mm drill bit through the opposite cortex. A depth gauge was used to obtain the correct length of screw before tapping the pilot hole with a 3·5 tap. Two 3·5 mm cortical screws, 4·8 and 5·5 cm long, were driven in place to assess correct positioning and length, and they then were removed. A 7 mm thick osseous flap, 2·5 cm long and 1·5 cm wide, was made with an oscillating saw from the greater tubercle, to include the insertion of the supraspinatus muscle. The flap was retracted and separated proximally from the surrounding tissues by blunt dissection (Fig 2).The bicipital tendon was transposed laterally and the bone flap from the greater tubercle was fixed in position with the screws (Fig 3). The wound was flushed with saline. The brachiocephalic muscle was reattached and the subcutane-ous tissues were closed in a simple continuous pattern with 2·0 braided lactomer (Polysorb 2.0; Syneture). The skin was closed with simple interrupted sutures of polypropylene (Prolene 0; Ethicon). A stent bandage was applied on the skin. The alpaca was placed into sternal recumbency with its head held up and blankets were used to treat the hypother-mia (rectal temperature 35·7°C at the end of the pro cedure). The endotracheal tube was removed once the animal’s swallowing reflex returned, but the head was kept supported in an elevated position until full consciousness was achieved. A moderate bloat developed during the procedure, but it resolved once the animal was placed into sternal recum-bency and no reflux was observed. A dose of 6 mg morphine intramuscularly, followed by 0·6 mg (0·01 mg/kg) buprenor