CASE REPORT Modified lateral orbitotomy with combined partial zygomatic arch and vertical ramus ostectomies for excision of a frontal and parietal bone osteoma in a dog Laura E. Selmic BVetMed, MPH, DACVS-SA, DECVS | Megan T. Cray VMD | Josh G. Good DVM | David W. Hummel DVM, DACVS-SA | Stephen Joslyn DVM, DACVR Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois Correspondence Laura E. Selmic, Department of Veterinary Clinical Sciences, The Ohio State University College of Veterinary Medicine, 601 Vernon L. Tharp St, Columbus, OH 43210. Email: selmic.1@osu.edu Abstract Objective: To describe modifications to the lateral orbitotomy for surgical excision of tumors affecting the frontal, parietal, palatine, or temporal bones. Study design: Case report. Animal: A 5-year-old female spayed American pit bull terrier. Methods: The dog presented for excision of a bone tumor affecting the right fron- tal and parietal bones. A modified lateral orbitotomy was performed with combined partial zygomatic arch and vertical ramus ostectomies to increase working space and allow drilling of the calvarium ventral to the mass. Results: The dog tolerated the procedure well, and there were no complications from either the ostectomies or the craniectomy. Histopathological examination was consistent with complete excision of an osteoma. The dog survived 2 years with no recurrence and was euthanized due to an intestinal mass. Conclusion: The lateral orbitotomy approach can be modified with combined par- tial zygomatic arch and vertical ramus ostectomies to increase exposure and work- ing space for resection of tumors affecting the frontal, parietal, palatine, or temporal bones. 1 | INTRODUCTION Tumors of the medial orbit and rostral frontal bones can be difficult to access surgically. 1 Approaches that have been described in the veterinary literature include transconjunctival, 2 transfrontal, 1 dorsal and partial orbitotomy, 2 total and partial orbitectomy, 3 lateral orbi- totomy involving zygomatic arch resection or zygomatic arch replacement, 4 and partial orbitectomy using a com- bined intraoral and dorsolateral approach. 3,5 The modi- fied lateral orbitotomy approach was reported to give good access to the ventral aspect of the orbit in 2 dogs (one Afghan hound and 1 pointer). 4 However, difficulties may still arise in obtaining sufficient access for re- section of the tumor because of individual tumor location and patient factors. 1,5 If the tumor is caudally located within the orbit or arising from the rostral frontal bones, it is possible the dorsal vertical ramus will be overlying the tumor when the mouth is closed. In addition, it has been the authors’ experience that, in some heavily mus- cled breeds of dog (such as American pit bull terriers and mastiffs), the thickness of the masseter can obstruct exposure of the ventral aspect of tumors. Limited surgi- cal exposure and working space complicates these sur- geries, potentially impacting the decision to take the dog to surgery or increasing the length of the surgical proce- dure or by impairing complete excision of the tumor. This report describes a modified lateral orbitotomy approach with combined ostectomies of the unaffected zygomatic arch and vertical ramus of the mandible to Received: 8 October 2017 Revised: 9 March 2018 Accepted: 11 May 2018 DOI: 10.1111/vsu.13116 Veterinary Surgery. 2018;1–6. wileyonlinelibrary.com/journal/vsu © 2018 The American College of Veterinary Surgeons 1