Evaluation and treatment of an adult quarter horse with an unusual fracture of the humerus and septic arthritis

Abstract

Humeral fractures are rare and usually carry a guarded prognosis in adult horses. This paper describes the evaluation and the successful surgical management of a fracture of the lateral supracondyloid crest and part of the epicondyle of the humerus in an adult quarter horse.

Skeletal fractures are a major cause of fatalities in horses (1,2). A retrospective study of fatal musculoskeletal injuries in racing Thoroughbreds showed a low prevalence of humeral fractures in adult horses, occurring in 10 of 157 cases (3). Most fractures are diaphyseal, complete, and comminuted; 50% of horses evaluated for these fractures are immediately euthanized (2,4,5,6). The surgical management of humeral fractures may be successful in younger horses, but it is rarely successful in adult horses due to postoperative disruption following repair. The following report describes the successful management a humeral fracture with an unusual configuration.

An 8-year-old quarter horse gelding (500 kg) was found at pasture with reluctance to bear weight on the left forelimb and unwillingness to fully protract it. The trainer noticed a full thickness skin wound on the lateral aspect of the left forelimb near the elbow. It was approximately 2 cm in diameter and 3 cm deep, located below the elbow joint. Trauma was suspected. The trainer treated the horse with penicillin, IM, and phenylbutazone, PO, q24h, for 3 d, and administered a tetanus toxoid. The referring veterinarian examined the horse 2 d after the injury had occurred. The horse was reluctant to bear weight on the grossly swollen limb, and there was a serosanguineous discharge from the wound. Three days after first being observed lame, the horse was referred to the Atlantic Veterinary College (AVC) for further evaluation and treatment of a suspected olecranon fracture.

On presentation to the AVC, the horse was in good body condition but was reluctant to bear weight (grade 4/5 lame) on the left forelimb. The limb was markedly swollen from the point of the elbow to the middle of the cannon bone and was warmer to the touch than the right forelimb. A draining wound was evident on the lateral aspect of the elbow. Palpation of this area was resented and cellulitis of the limb was diagnosed. No other abnormalities were detected on physical examination. The area surrounding the wound was clipped, cleaned, and lavaged with sterile saline. An ice pack was applied over the proximal half of the limb for 20 min. Craniocaudal and mediolateral radiographs of the elbow were taken. On lateral views, a bone fragment was observed approximately 5 cm long and arising from the region of the lateral epicondyle of the humerus, tapering proximally to a sharp point (Figure 1). This fragment was displaced caudodistally from the shaft of the humerus. The horse was diagnosed radiographically with a simple displaced fracture of the lateral supracondylar crest and lateral epicondyle of the left humerus, complicated by cellulitis. Penetration of the cubital joint was suspected but could not be confirmed on radiographs. Based on the available data, the owner requested surgical exploration.

Figure 1. Mediolateral view of the left elbow joint and distal one-third of the humerus, showing the fragment of bone displaced from the lateral supracondylar crest and epicondyle.

The wound was dressed and the limb was heavily bandaged from the hoof to above the elbow to reduce the limb swelling prior to surgery. Next day, sodium penicillin (Sodium Penicillin G; Novopharm, Toronto, Ontario), 22 000 IU/kg body weight (BW), IV, q6h, and phenylbutazone (Phenylbutazone Injection; Dominion, Winnipeg, Manitoba), 4.4 mg/kg BW, IV, q12h, were administered preoperatively. The gelding was sedated with 450 mg of xylazine hydrochloride (Xylamax; Bimeda-MTC, Cambridge, Ontario). Anesthesia was induced with 50 g of guaifenesin (Guaifenesin; Wiler Fine Chemicals, London, Ontario), 1 g of ketamine (Ketaset; Ayerst, Guelph, Ontario) and 10 mg of diazepam (Valium; Sabex, Boucherville, Quebec), IV. Anesthesia was maintained using 3% isoflurane (Isoflo; Abbott, North Chicago, Illinois, USA) on a circle rebreathing circuit. The gelding was placed in right lateral recumbency, and the left limb was prepared aseptically. Following routine draping, a 20-cm crescent-shaped incision was made caudal to the wound over the distal diaphysis of the humerus extending distad to the level of the proximal extremity of the radius. The intrasynovial entry point of the traumatic penetration wound was found within the proximal craniolateral region of the joint sac. The wound tract terminated in the area of the proximal aspect of the lateral epicondyle from which the fracture line appeared to originate. A combination of blunt and sharp dissection was used to expose the large bone fragment, and the caudal aspect of the cubital joint. Some small fragments of bone were removed with rongeurs. The larger fragment identified on the radiographs was well attached to the underlying tissue and had penetrated the joint space via the wound, but there was no articular component to the fracture. A small portion of the origin of the lateral collateral ligament was sharply dissected to allow removal of the fragment. Turbid synovial fluid was observed in the incision and swabs for were taken for culture and sensitivity testing. The joint was lavaged with sterile saline. A rigid drain, composed of fenestrated silicone irrigation tubing, was placed in the lateral aspect of the joint, so as to exit the limb distal and caudal to the original wound, and was attached to a suction unit (Hemovac; Source Medical, Pointe-Claire, Quebec), which was affixed to the horse's mane. The surgical incision was closed routinely with the exception that gentamicin sulfate (Gentocin; Schering Canada, Pointe-Claire, Quebec)-impregnated polymethylmethacrylate (PMMA) beads (1 g gentamicin in 20 g PMMA) were placed SC. The skin was closed with staples. The original wound was debrided and left to heal by second intention. A sterile stent bandage was affixed over the surgical site and a full limb bandage was placed on the limb. Romifidine (Sedivet; Boehringer, Burlington, Ontario), 10 mg, was given IV prior to an uneventful recovery.

Postoperatively, the gelding was maintained on phenylbutazone, 4.4 mg/kg BW, IV, q12h, for 3 d, which was reduced to 2.2 mg/kg BW, PO, q12h, for 2 d, and then to 2.2 mg/kg BW, PO, q24h, for 6 d. No organisms were observed on Gram staining of smears prepared from the joint swab. Ceftiofur (Excenel; Pharmacia and Upjohn, Orangeville, Ontario) was administered at 4.4 mg/kg BW, IV, q12h, whilst the culture and sensitivity results were pending. The drain reservoir was emptied at least twice daily. Initially, the draining fluid was hemorrhagic to serosanguineous, becoming serous in nature as the area began to heal. The drain was removed 6 d postoperatively, as it was no longer productive and a mucopurulent discharge was noticed around it at the exit point from the skin; at the next bandage change, this had resolved. The original wound at this time had filled with granulation tissue and there was no discharge; the stent was removed. Staphylococcus aureus and an Enterococcus sp. were cultured from the swabs taken at the time of surgery and were found to be sensitive to penicillin. Ceftiofur administration was discontinued 8 d postoperatively. The gelding was discharged to the owner 14 d after presentation. Although still lame (grade 2/5), a significant improvement in his gait was evident.

At the owner's request, the gelding returned to the AVC 2 wk after discharge for removal of the PMMA beads. On presentation, he displayed no evidence of any abnormality, except for a small incisional scar. The beads were removed under sedation, local anesthesia, and physical restraint. Follow-up radiographs were not obtained at this time, due to the increasingly fractious response of the horse to further handling and his poor response to further sedation. Telephone contact with the owner 5 mo after the initial injury indicated that the horse had returned to training for competitive activity and no adverse effects were noted.

The current case had a comparatively small-sized main fragment and the configuration of the fracture did not appear to require reconstruction of the diaphysis with implants. It was therefore hypothesized, prior to surgery, that the prognosis for this fracture would be better than that reported for other types of complete diaphyseal fractures (4,5). A fracture with this configuration could not be found in previous reports in either the canine or equine species; there is limited information in the literature on humeral fractures of any configuration in horses (7). Fractures of the epicondylar and supracondylar region occur in dogs, but they usually involve complete fracture between the condyles, crossing the physis and exiting the metaphysis (8). These epicondylar or supracondylar fractures are usually caused by external trauma in dogs, and trauma has been implicated in 1 case of articular lateral condylar fracture in a horse (7,8). In our case, the condyles and the physis were not fractured; however, the history, the skin wound, and the open comminuted fracture suggest an etiopathogenesis related to trauma.

Preoperative evaluation includes identification of the tissues affected and often preliminary wound debridement. In cases with less extensive soft tissue inflammation, arthrocentesis and arthrography are recommended in order to determine joint involvement. In this case, the wound appeared to travel towards the cubital joint and distal extremity of the humerus, close to the location of the radial nerve. Joint sepsis was suspected preoperatively, but the extensive cellulitis and the risk of iatrogenic contamination or injury in the absence of a controlled surgical environment was considered unacceptable. Exploration of the wound without the aid of general anesthesia may have resulted in further contamination of the joint or injury to the radial nerve.

Arthroscopic approaches have been suggested for treating epicondylar fractures of the adult elbow, but no clinical cases in which this approach was used has been described (7). In the current case, a lateral approach was necessary to permit exposure of the lateral supracondyloid crest. The surgical approach was made through an incision adjacent to the traumatic wound on the limb to avoid introducing any contaminants from the initial wound to the fracture site. Prior to surgery, injury of the radial nerve was not suspected, and the gelding did not display any of the classical signs, such as dropped elbow (4,5). Careful dissection through the soft tissue prevented iatrogenic severance of the radial nerve (7,8). All fragments of bone were removed to reduce the risk of degenerative joint disease or subsequent sequestrum formation. Lavage of the joint was indicated to remove gross and cellular debris as a treatment for septic arthritis, which was suspected. Based on the surgical findings, it appeared that the fracture had been caused by a foreign body penetrating the joint and contacting the nonarticular portion of the lateral epicondyle. When joint penetration was confirmed during surgery, the prognosis became more guarded (9). The rigid drain was used to manage dead space and to remove exudate from the elbow joint.

The cultures of S. aureus and an Enterococcus sp., in comparison with a retrospective study, have been found in 11.8% and 9.3% of isolates, respectively (10). Both isolates were highly susceptible to penicillin. The sensitivity of the latter is uncommon among isolates. One study reported 29.2% of S. aureus and 3.9% of Enterococcus spp. were susceptible to penicillin (10).

Although there were no untoward sequelae in this case, consideration should be given to assisting the postanesthetic recovery of adult horses having any long bone injury. Incomplete diaphyseal fissure fractures may not be seen on radiographs, or via a limited surgical exposure, and may not be discovered until a catastrophic fracture occurs when weight is brought to bear on the limb (7). CVJ