A 3-year-old 2.5-kg (5.5-lb) sexually intact male Pomeranian was evaluated because of non–weight-bearing lameness of the right forelimb of 1 day's duration that developed after falling from its owner's bed. On physical examination, the only abnormality was signs of pain localized to the proximal portion of the right antebrachium. Results of a CBC and serum biochemical analysis revealed no clinically relevant abnormalities.
The patient was sedated with methadone (0.4 mg/kg [0.18 mg/lb], SC) and acepromazine (0.05 mg/kg [0.023 mg/lb], SC). Anesthesia was induced with propofol (4 mg/kg [1.8 mg/lb], IV) and thiopentone (4 mg/kg, IV) and maintained with isoflurane in oxygen at a concentration of 1% to 2% after orotracheal intubation.
Orthogonal radiographs of both antebrachia were obtained. The proximal portion of the right radius had a minimally displaced, reducible fracture that appeared to have propagated from a well-demarcated, ovoid, osteolytic lesion within the cortex of the caudolateral aspect of the radius (Figure 1). The right ulna, left radius, and left ulna were unremarkable. Subsequently, the right forelimb was further assessed with CT.a Computed tomography confirmed the fracture, and its communication with an expansile, osteolytic lesion and the associated smooth periosteal reaction of the caudolateral aspect of the proximal diaphysis of the radius (Figure 2). No abnormalities were noted on CT images of the contralateral radius, shoulder and elbow joints of both forelimbs, thorax, and abdomen. Imaging results were consistent with RUIN and secondary fracture of the radius. Plans were then immediately made to biopsy the bony lesion and repair the fracture by open reduction and internal fixation. Cefazolin (22 mg/kg [10 mg/lb], IV) was administered to the patient prior to proceeding with surgery.
The patient was positioned in dorsal recumbency, and the right forelimb was clipped of hair and aseptically prepared for surgery. The limb was draped, and a craniomedial approach to the right radius was made. The fracture was visualized, and the lateral surface of the radial cortex appeared expanded (Figure 3). A tenacious, rubbery fibrous tissue filled the gap between the fracture fragments. A bone curette was used to remove this tissue as well as open the proximal and distal portions of the medullary cavity. The tissue was placed into a container of neutral-buffered 10% formalin and submitted for histologic examination. Then, the fracture was reduced with bone reduction forceps. A 7-hole locking bone plateb was contoured, applied to the cranial aspect of the radius, and secured with 6 bicortical locked screws, with 3 each proximal and distal to the fracture line, such that the middle hole of the plate immediately adjacent to the fracture remained open. A locking screw was also placed to hold the fragments in approximate reduction (Figure 4). During surgery, methadone (0.3 mg/kg [0.14 mg/lb], IV) was administered, and cefazolin (22 mg/kg, IV) was read-ministered once 90 minutes after administration of the first dose and then every 6 hours for 2 doses. Postoperative radiography confirmed reduction and stabilization of the fracture. The patient recovered uneventfully from anesthesia and was discharged from the hospital 1 day after surgery with a 7-day supply each of cephalexin (22 mg/kg, PO, q 12 h) and meloxicam (0.1 mg/kg [0.045 mg/lb], PO, q 24 h). The owner was instructed to restrict the patient's activity to short walks on a leash for 6 weeks.
Sections of the harvested fibrous tissue were processed normally and stained with H&E stain, and histologic examination revealed the presence of viable bone associated with dense fibrous tissue. A large proportion of the fibrous tissue was anuclear and had small areas of coagulative necrosis. No neoplastic cells were identified, and no bacteria or fungal elements were identified with a second histologic examination of tissue stained with special stains.
On physical examination 12 days after surgery, the patient ambulated normally with the right forelimb and did not have signs of pain on palpation of the surgical site. Fifteen weeks after surgery, the dog continued to ambulate normally, and findings on radiographic and CT examinations of the right antebrachium indicated healing at the fracture site and remodeling of the bone associated with the RUIN lesion (Figure 5).
The authors thank Dr. Richard Lam for providing his expertise in CT imaging and manuscript preparation.
No external funding was provided. The authors declare that there were no conflicts of interest.
Presented in abstract form at the Science Week Conference of the Australian and New Zealand College of Veterinary Scientists, Surfers Paradise, QLD, Australia, July 2018.
Radioulnar ischemic necrosis
Brilliance 6, Philips Healthcare, Macquarie Park, NSW, Australia.
Intrauma SpA, Genova, Italy.
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