478 EQUINE VETERINARY EDUCATION / AE / October 2007

Case Report to treat a donkey for coxofemoral luxation F. T ÓTH*, H. S. ADAIR, T. E. C. HOLDER AND J. SCHUMACHER The University of Tennessee, College of Veterinary Medicine, Large Animal Clinical Sciences, 2407 River Drive, Knoxville, Tennessee 37996, USA. Keywords: horse; donkey; coxofemoral luxation; femoral ostectomy

Introduction condition was 7/9 (Henneke et al. 1983). Its right hind foot was rotated outward, and the right calcaneal tuberosity and Coxofemoral luxation occurs uncommonly in horses and right greater trochanter were positioned more proximally than donkeys (Malark et al. 1992). Young equids are most their left counterparts. While standing, the donkey rested the commonly affected, and the most common cause is trauma toe of the affected limb on the ground, but when walked, it (Garcia-Lopez et al. 2001). Several techniques have been was a grade 5 out of 5 lame (Anon 1991). It violently resisted advocated for the treatment of horses with the condition. In manipulation of its right hindlimb. Crepitus was not palpated one study, reluxation after closed reduction occurred in 4 out in the region of the right coxofemoral . of 5 horses (Malark et al. 1992). Accounts of femoral head and neck ostectomy performed in cattle report a good prognosis Radiographic examination for growing to full adult weight (Squire et al. 1991), whereas accounts of femoral head and neck ostectomy performed in The donkey’s pelvis was radiographically examined, using a horses and ponies describe multiple complications, such as lateromedial radiographic projection obtained with the upward fixation of the patella and osteoarthritis of the donkey standing and sedated with xylazine HCl (0.5 mg/kg coxofemoral joint (Platt et al. 1990; Squire et al. 1991). bwt, i.v.). Radiographic examination revealed dorsocranial This report describes the successful outcome of an luxation of the right femoral head from the acetabulum adult donkey suffering from coxofemoral luxation (Fig 1). Treatment recommended was excision of the right treated by femoral head ostectomy. femoral head.

Case details

History

A 5-year-old donkey was referred to the University of Tennessee’s Veterinary Teaching Hospital for treatment for coxofemoral luxation. The donkey had been observed to be lame on its right rear limb for 4 weeks, but it had been on pasture with other donkeys and had not been closely observed by the owner, so the duration of lameness may have been longer. By examining the donkey’s right rear limb and hip radiographically, the referring veterinarian had established the cause of lameness to be luxation of the right coxofemoral joint.

Clinical findings

At presentation, the donkey weighed 153 kg, and its body Fig 1: Lateromedial radiographic view showing the right femoral head (white arrows) displaced dorsocranially from the *Author to whom correspondence should be addressed. acetabulum (grey arrows). EQUINE VETERINARY EDUCATION / AE / October 2007 479

Surgery Treatment/aftercare

A preoperative complete blood count and the results of Following surgery, the donkey received tetanus toxoid, cefazolin biochemical serum assays were within normal limits. Cefazolin (11 mg/kg bwt i.v., q. 8 h), gentamicin sulphate (6.6 mg/kg bwt (Cefazolin for Inj)1 11 mg/kg bwt i.v., gentamicin sulphate i.v., q. 24 h), and phenylbutazone (4.4 mg/kg bwt i.v., q. 12 h). (GentaVed 100)2 6.6 mg/kg bwt i.v. and phenylbutazone (Equi- As soon as the donkey recovered from anaesthesia, it received Phar Phenylbutazone Injection)2 2.2 mg/kg bwt i.v. were morphine (Morphine Sulfate Inj.)9, administered once into the administered preoperatively. The donkey was sedated with epidural space (0.1 mg/kg bwt), and i.m. (0.2 mg/kg bwt, q. xylazine HCl (AnaSed)3 1.1 mg/kg bwt i.v. and anaesthesia was 6 h). The suction drain was emptied every 4 h, and the amount induced with a combination of ketamine HCl (Vetalar)4, 2 mg/kg of fluid removed recorded. The drain was removed the day after bwt and diazepam (Diazepam Injection)5 0.1 mg/kg bwt surgery, when the amount of fluid obtained every 4 h had administered i.v. Anaesthesia was maintained with a mixture of decreased to less than 10 ml. oxygen and isoflurane administered through a circle system and On the second day after surgery, the donkey placed more ketamine HCl 50 μg/kg bwt/min and lidocaine (Lidocaine weight on the limb when standing and walking than before hydrochloride inj.)2 2%, 50 μg/kg bwt/min administered i.v. surgery. The frequency of morphine administration, therefore, The donkey was positioned in left lateral recumbency and was decreased to twice daily. the right gluteal region was prepared for aseptic surgery. The When the Stent bandage was removed 4 days after coxofemoral joint was approached dorsally (Ducharme 1996) surgery, the surgery site was dry and only slightly swollen. By through a 25 cm long curvilinear skin incision, centred over the fifth day following surgery, the donkey began placing the greater trochanter. The incision followed the cranial edge more weight on the limb. Morphine administration was of the biceps femoris muscle and extended distally to the discontinued and the dose of phenylbutazone decreased to middle part the femoral diaphysis. The cranial margin of the 2.2 mg/kg bwt i.v., q. 24 h. Administration of cefazolin and biceps femoris muscle, the caudal margin of the superficial gentamicin was discontinued on the sixth day after surgery, gluteal muscle, and the tensor fasciae latae muscle were and 13 days after surgery, the sutures were removed. divided at their intermuscular junction to expose the greater When the donkey was discharged from the hospital trochanter. Two gliding holes were drilled through the greater 14 days after surgery, it placed the sole of its right rear foot on trochanter using a 4.5 mm AO/ASIF drill bit and, after inserting the ground when walking. The owner was instructed to a 3.2 mm drill sleeve into each of these holes, thread holes administer phenylbutazone (2.2 mg/kg bwt, per os) to the were drilled using a 3.2 mm drill bit. The thread holes were cut donkey once daily for a week and to confine the donkey to a with a 6.5 mm cancellous tap for later insertion of 6.5 mm stall for 45 days, before allowing it to be turned out into a AO/ASIF screws. The greater trochanter was then transected small paddock for an additional 45 days. using obstetrical wire, while preserving the attachments of middle and deep gluteal muscles on the greater trochanter. Follow-up After the greater trochanter was transected and reflected, along with the middle and deep gluteal muscles, the head of Follow-up information obtained from the referring the and the disrupted ligament and accessory ligament veterinarian by telephone conversation 22 months after of the femoral head were visible. The fibrocartilagenous dorsal surgery revealed that the donkey appeared to be comfortable acetabular rim was intact but severely worn by the constant at pasture. Although the donkey was sound at a walk, it was pressure and motion of the . Fracture of the a grade 2/5 lame at the trot. Shortening of the affected limb acetabulum, or femoral head or neck was not observed. The was not apparent. Both the referring veterinarian and the neck of the femoral head was transected using an oscillating owner of the donkey were satisfied with the outcome. saw (3M)6. Using a file, rough edges were removed from the transected neck of the femur. The dorsal rim of the Discussion acetabulum, including the remaining fibrocartilage, was removed using a rongeur, to minimise bone-to-bone contact. Coxofemoral joint luxation is most commonly caused by The surgical site was lavaged, and the greater trochanter trauma (Malark et al. 1992) and is often associated with reattached to the femur by inserting 6.5 mm AO/ASIF screws upward fixation of the patella, in which case it may result from (60 and 66 mm long) into each of the previously drilled and violent contraction of the quadriceps femoris muscle as the threaded holes. Before closing the wound, a closed suction horse tries to flex the limb while the stifle is locked (Clegg and drain (Reliavac)7 was placed into the wound near the Butson 1996). In one report, 70% of coxofemoral luxations coxofemoral joint. The deep and superficial fascial layers were were due to trauma, either from a kick from another horse or closed using USP 0 lactomer 9-1 Polysorb8 placed in a simple from a fall. Recovery from general anaesthesia, application of continuous pattern, and the subcutis was closed with USP 2-0 a full-limb cast and in the case of an aged mare, dystocia were lactomer 9-1 Polysorb8 placed in the same pattern. The skin also noted as initiating causes (Malark et al. 1992). We incision was closed with USP 0-polypropylene Surgipro8, and a speculate that the injury of the donkey was a result of a Stent bandage was sutured over the wound. Recovery from trauma suffered while it was on pasture, but we were not able anaesthesia was unassisted. to determine the nature of the trauma. 480 EQUINE VETERINARY EDUCATION / AE / October 2007

Horses and donkeys rarely develop coxofemoral joint increased, the incidence of survival decreased. The incidence luxation because the acetabulum of these species is deep, and of survival for cows (75%) was significantly better than that the fibrocartilagenous acetabular rim further increases the for horses (33%). effective acetabular area (Hendrickson 2002). In addition, the Coxofemoral luxation can be reduced with the horse supporting soft tissue structures, such as the ligament of the anaesthetised using a closed or open technique (Malark et al. femoral head (i.e. the round ligament), the accessory ligament 1992), but in one report, 4 of 5 horses suffering from of the femur, the joint capsule, and the gluteal musculature coxofemoral luxation reluxated after closed reduction (Malark are well developed (Dyce et al. 1996). Coxofemoral luxation is et al. 1992). An Ehmer sling was used successfully in a 9-year- accompanied by rupture of the ligament of the femoral head old Shetland pony to prevent reluxation after closed reduction and the accessory ligament (Hendrickson 2002). (Clegg and Butson 1996). If the luxation is to be reduced, it The signs displayed by a horse suffering from coxofemoral should be reduced as soon as possible after luxation to avoid luxation are usually characteristic. The affected horse is either contraction of muscles and filling of the acetabulum with nonweightbearing on the affected limb, or it stands and granulation tissue. If the coxofemoral luxation is associated walks with only the toe of the affected limb touching the with a fracture of the dorsal acetabular rim, simple reduction ground (Malark et al. 1992). The affected limb appears of the femur is unrewarding, and femoral head ostectomy is shorter, and the foot is rotated outward. The pelvis appears necessary. Femoral head ostectomy may result in a to be asymmetric because the greater trochanter of the pseudoarthrosis and may provide permanent pain relief affected limb is positioned more dorsally than the greater (Hendrickson 2002). trochanter of the unaffected limb, provided that the direction A recent report of a 100 kg miniature horse suffering from of luxation is dorsocranial. In most case reports describing coxofemoral luxation of 5 days’ duration, described successful coxofemoral luxation of a horse or pony, the femoral head surgical treatment using a combination of techniques was luxated dorsocranially (Platt et al. 1990; Squire et al. frequently used to treat small animals for coxofemoral luxation 1991, Malark et al. 1992; Garcia-Lopez et al. 2001). One (Garcia-Lopez et al. 2001). These techniques included the exception was a Shetland pony that had a cranial luxation toggle-pin technique, the prosthetic capsule technique, and (Clegg and Butson 1996). transposition of the greater trochanter (Garcia-Lopez et al. The affected horse usually violently resists flexion or 2001). After receiving surgical treatment, this miniature horse abduction of the affected limb and manipulation of the became sound and had remained so after being pastured for affected limb may produce a soft, clicking crepitus (Richardson 2 years. Due to the chronicity of the luxation in the case 2006). When coxofemoral luxation is a suspected cause of reported here, we believed femoral head ostectomy to be the lameness, differential diagnoses should include femoral capital best choice of treatment. physeal fracture (Hunt et al. 1990), round ligament rupture, Other techniques used to repair coxofemoral luxation and fracture of the pelvis or femur. include transacetabular pinning, ischio-ileal (De Vita) pinning, Definitive diagnosis of coxofemoral luxation is usually and total using a prosthesis developed for established during radiographic examination of the pelvis, human patients, but results of these techniques in horses and cattle have been disappointing (Malark et al. 1992). When which, if the horse is small, can often can be performed with prostheses designed for human use or custom-made the horse standing (Clegg and Butson 1996). The luxated prostheses were implanted into the femur of ponies, rigid head of the femur is usually craniodorsal to the acetabulum fixation was achieved in only 3 of 7 ponies, and all 3 of these (Malark et al. 1992). Radiographic examination of the pelvis is developed dorsolateral coxofemoral luxation and also useful to rule out fracture of the pelvis or the femoral pseudoarthrosis within the first 10 days after surgery (Von head (Hendrickson 2002). Recum 1980). Radiographic views obtained while the donkey was A multimodal approach to the anaesthetic management of standing enabled us to confirm the referring veterinarian’s this donkey included using lidocaine and ketamine infusions in diagnosis. Because the lateromedial radiographic projection association with isoflurane. Lidocaine was included in the clearly delineated the luxation, a dorsoventral radiographic anaesthetic protocol for its effect in reducing MAC (Dzikiti projection was not obtained. et al. 2003) and its analgesic properties (Robertson et al. In one study investigating the outcome of 6 horses, 2005). Ketamine also reduces MAC of inhaled anaesthetic 3 mature ponies and 4 cows that underwent femoral head drugs in equids (Muir and Sams 1992). This report details the ostectomy for treatment for coxofemoral luxation, one successful use of femoral head ostectomy in a donkey to horse, 2 ponies and one cow were subjected to euthanasia restore a satisfactory degree of soundness, allowing it to lead after surgery because of post operative complications (Squire an apparently pain-free existence. et al. 1991). Two horses, one pony and 3 cows grew to full adult weight. Two horses died of causes unrelated to the Manufacturers’ addresses surgery within 6 months, and one horse was lost to follow- up. Those patients that were alive a year or longer after 1Sandoz, Holzkirchen, Germany. surgery had moderate gluteal atrophy of the affected side 2VEDCO Inc, St Joseph, Missouri, USA. 3LLOYD Laboratories, Shenandoah, Iowa, USA. and stood and walked with the stifle and toe abducted and 4Fort Dodge, Madison, New Jersey, USA. the hock adducted. In that report, as age and weight 5Hospira Inc, Lake Forest, Illinois, USA. EQUINE VETERINARY EDUCATION / AE / October 2007 481

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