Vertical ramus osteotomy for improved exposure of the distal internal carotid artery: A new technique

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1 TECHNICAL NOTE Vertical ramus osteotomy for improved exposure of the distal internal carotid artery: A new technique Peter E. Larsen, DDS, and Wtlliam L. Smead, MD, Columbus J Ohio Access to the internal carotid artery distal to a line drawn from the angle of the mandible to the tip of the mastoid process may be compromised (Fig. 1).1 The angle and ramus of the mandible overlie this segment of the distal internal carotid artery (the paraatlantoaxial segment) from a few centimeters after its origin and distally to its entry into the carotid canal. Even when the exposure is sufficient to display the arterial lesion, the mandible obstructs vision of other vital strucmres, especially the cranial nerves in the region, and may compromise surgical maneuvers involved in repair ofthe vessel. 2 Access may be necessary for repair of traumatic injury to the distal internal carotid or for endarterectomy. Previously recommended aids to exposure have included anterior mandibular -subluxation or dislocation and mandibular osteotomy. Subluxation and dislocation may be associated with inadequate access. Previously recommended osteotomies fail to use modern maxillofacial principles including the use of rigid internal.fixation. The vertical ramus, osteotomy is ideal for allowing improved access to the distal internal carotid artery, can be accomplished through the standard surgical exposure needed for access to the vessel, requires minimal additional surgical time, and is associated with little additional morbidity. The technique recommended requires rigid internal fixation with bone plates, which are adapted to the ramus and. have screw holes drilled before osteotomy to assure exact repositioning of the osteotomized segments. From the Department of Dentistry, Division of Oral and Maxillofacial Surgery (Dr. Larsen) and Surgery, Division of Peripheral Vascular Surgery (Dr. Smead), Ohio State University, Columbus. Reprint requests to: Peter E. Larsen, DDS, Department oforal and Maxillofacial Surgery, 305 W. 12th Ave., Box 169, Columbus, OH /38/ Fig. 1. Access to the internal carotid artery distal to a line from the tip of the mastoid to the angle of the mandible may be compromised. The ramus ofthe mandible overlies most of the artery in this region. DESCRIPTION OF TECHNIQUE A standard carotid endarterectomy incision extending along the anterior border of the sternocleidomastoid muscle from the mastoid process to the sternoclavicular joint is used. The mandibular ramus is approached through this incision by anterior dissection along the plane between the masseter muscle and the parotid gland, keeping the branches of the facial nerve superficial to the dissection. Immediatelyoverlying the lateral aspect ofthe ramus of the mandible, the attachment of the masseter muscle is elevated allowing access to the ramus. The lateral aspect of the mandibular ramus is exposed superiorly to the sigmoid notch where a retractor is

2 Volume 15 Number 1 January 1992 Vertical ramus osteotomy 227 Fig. 2. The broken line indicates where the osteotomy is made. Itextends from the depth ofthe sigmoid notchto the angle of the mandible. Fig. 4. Radiograph shows plate fixation. This patient is 4 weeks after surgery. The plates have assured exact position of the segments into their presurgical position with maintenance of normal jaw opening and occlusion. Fig. 3. A, The vertical ramus osteotomy has been performed. The mandible is retracted anteriorly and rotated away from the side of the osteotomy (arrow). The proximal segment is rotated forward and laterally (arrow).!his allows uncompromised access to the entire distal mternal carotid artery to the level of the skull base. B, Medial view ofthe mandibular ramus. The vertical ramus?steotomy is performed posteriorly to the entrance of the!ffierior alveolar nerve. The incidence of altered sensation IS minimal. placed. A mark identifying the planned osteotomy is then scribed in the lateral cortexfrom the depth ofthe sigmoid notch to the angle of the mandible with a reciprocating saw (Fig. 2). Miniature titanium bone plates are then adapted across the planned osteotomy and contoured to the ramus. Holes for screw placementare drilled, taking care to avoid the inferior alveolar nerve within the distal segment, and the plates are removed and placed aside. The osteotomy is completed by use of the reciprocating saw. The distal segment of the mandible is now retracted anteriorly and the proximal segment retracted laterally and rotated superiorly and anteriorly (Fig. 3). This allows complete access to the distal aspect ofthe internal carotid artery to the level of the base of the skull. Surgical management of the carotid arterial lesion is then accomplished. After completion ofthe arterial surgery, the distal segment ofthe mandible is repositioned, and the previously adapted plates are easily replaced. This ensures exact repositioning of

3 228 Larsen and Smead Journal of VASCULAR SURGERY Fig. 5. A, Lateral view ofthe left internal carotid arteriogram. B, PA view ofthe left internal carotid arteriogram. the mandibular segments and maintenance of the preoperative occlusion (Fig. 4). TRAUMA APPLICATION This technique is very useful for penetrating injuries within wne III of the neck. Treatment of injuries in this area is problematic because of diffi... culty with access. This technique allows uncompromised access.. A 23-year-old white woman was brought to the Ohio State University emergency department after having been shot once in the left lateral neck by a.22-caliber handgun. Evaluation by the trauma service revealed no otherwounds. Thepatientwas stable and neurologically intact. The entrance wound was 0.5 cm in diameter and located just below the lobe of the left ear. Plain radiographs revealed multiple missile fragments along the medial aspect ofthe right mandibular ramus with some minor comminuted fractures of the anterior aspect of the ramus. These fractures did not extend through the mandible. A carotid arteriogram was performed, which demonstrated a disruption of the distal internal carotid artery on the left, with development of a pseudoaneurysm (Fig. 5). Physicians on the vascular surgery service were consulted for management of the carotid artery injury, and physicians on the oral and maxillofacial surgery service were consulted for management of the facial injuries as well as assistance in gaining access to the carotid artery. At operation the common carotid artery was exposed. Dissection was carried superiorly to the bifurcation, and the internal and external carotid arteries were isolated. A vertical ramus osteotomy was performed through this incision as described. The hypoglossal nerve was identified and retracted anteriorly, and the styloid process was removed exposing the injury to the internal carotid artery. A single through-and-through perforation could be seen where the missile had traversed through the lateral and out the medial aspects of the artery (Fig. 6). The injury was approximately 5 mm below the base of the skull. Through the approach described, access was uncompromised, and the distal internal carotid artery could be identified to its point of entrance through the skull base. An inadequate distance between the skull base and the perforation existed to allow clamp or shunt placement. Distal internal carotid artery control was achieved with a Fogarty balloon catheter, whereas repair ofthe injury was accomplished with a reversed saphenous vein

4 Volume 15 Number I January 1992 Vertical ramus osteotomy 229 Fig. 7. With anterior subluxation, the ramus of the mandible still frequently obscures visibility of a significant portion of the internal carotid artery. Fig. 6. lntraoperative view of the injury to the internal carotid artery. This through-and-through perforation of the vessel (arrows) was present 0.5 cm below the base of the skull. Note the excellent visibility and access provided by the vertical ramus osteotomy. graft that had been harvested simultaneously with the carotid exploration. The wounds were closed, and the patient underwent an uneventful postoperative COurse. ENDARTERECTOMY APPLICATION Access for carotid endarterectomy may be compromised because of the presence of a high bifurcation. A 69-year-old white man was referred to the Ohio State University Department of Peripheral Vascular Surgery after an attempted carotid endarterectomy the preceding day at an outside hospital Was aborted because of inability to gain access to the bifurcation and to the internal carotid artery. DiffiCulty with access was a result of a high carotid bifurcation complicated by severe ankylosing Spondylitis with fusion of several cervical vertebrae. This precluded any rotation or extension of the neck. The existing incision was opened. The carotid bifurcation was located at the level of the mandibular angle. Improved access through extension of the neck was not possible. A vertical ramus osteotomy was performed through the existing incision. This allowed excellent exposure of the bifurcation and the internal and external carotid arteries. Standard endarterectomy was performed without any compromise in access. The mandibular osteotomy was reapproximated with bone plates. The patient underwent an uneventful recovery. DISCUSSION Access to the internal carotid artery between the mandibular angle and the base of the skull has been the subject of numerous discussions. Several authors have recommended anterior subluxation or dislocation of the mandible to assist in access to the artery in these situations. Experience with anterior dislocation or subluxation by means ofarch bars, IVY loops, or skeletal wires has been described. 2-4 Subluxation is defined as a physiologic self-reducing partial dislocation of the temporomandibular joint, whereas dislocation is described as extension beyond this physiologic limit. 4 These techniques require from 10 to 90 minutes for application of the wires. 3,4 When properly performed, a maximum additional distal exposure of 2 cm is possible (Fig. 7).4,5 This slightly improved exposure is due to the anterior movement

5 230 Larsen and Smead Journal of VASCULAR SURGERY Fig. 8. Previously recommended osteotomy techniques have included(a) Horiwntal ramus osteotomy, (b) Osteotomy through the mandibular angle, (c) Osteotomy through the anterior body, (d) Ostectomy of the mandibular angle. Fig. 9. If the osteotomy is performed horiwntally through the ramus, the coronoid process and temporalis muscle remain attached to the proximal segmentleading to rotation of ~e segment (arrow)) and instability and malocclusion. of the mandibular ramus. When subluxation or dislocation rather than osteotomy has been recommended as the treatment of choice, several reasons have been cited. These include the increase in time neededfor osteotomy, the risk ofinferior alveolar and facial nerve injury, and the need for intermaxillary fixation (wiring of,the teeth together).2 Disadvantages with the subluxation or dislocation techniques include the possibility of passing beyond a physiologic translation of the condyle resulting in the creation ofa pathologic dislocation with potential for long-term temporomandibular jointmorbidiry4; theneedtoapplythefixation before the onset ofoperation, or risk contamination ofthe wound with oral flora ifapplication is accomplished after carotid artery exploration is begun5; and inconsistent and limited improvement in access compared to that obtained with osteotomy techniques,5.7 especially if there is decreased range of motion of the temporomandibular joint. 5 "This decreased access or inconsistent access is of major concern. If the articular eminence of the temporomandibular joint is steep and the fossa is deep, the translation ofthe condyle is primarily in a vertical direction, and little increased exposure ofthe internal carotid artery is achieved. With this downward movement, the angle of the mandible may actually cause decreased access to the bifurcation.. Several osteotomy techniques have been previouslyrecommended (Fig. 8). Mandibulectomyofthe angle of the mandible, 5 horizontal osteotomy through the ramus, 6 osteotomy through the angle or anteriorly through the body ofthe mandible 2,7,s or a combination ofthese, have been tried. The rationale for selection ofthese different techniques has been somewhat obscure and based on principles used in mandibulectomy for resection of head and neck turnors. This may have contributed to the incorrect conclusion that osteotomy has an unacceptable morbidity when used to facilitate access to the carotid artery. The vertical ramus osteotomy has been used for many years by oral and maxillofacial surgeons for correction of prognathism. 9 Advantages of this osteotomyover previously recommended techniques for improving access to the internal carotid artery are numerous. Instrumentation for this procedure is readily available. Access can be achieved throughthe

6 Volume 15 Number 1 January 1992 Vertical ramus osteotomy 231 same surgical incision necessary for carotid artery exploration, allowing the decision whether to perform the osteotomy to be delayed until it has been determined that improved access is necessary. Exposure is designed to avoid injury to the facial nerve and the third division of the trigeminal nerve (Fig. 3). The incidence of inferior alveolar nerve paresthesia after osteotomies of this type is less than 2%,10,11 in comparison to that seen with osteotomies through the angle or body of the mandible, where the incidence approaches 100%. A vertical osteotomy is stable with respect to muscle pull, and the segments will not tend to displace as they do when the osteotomy is through the ramus horizontally. In the horizontal ramus osteotomy the relatively small proximal segment of the mandible is left with the coronoid attached to it allowing the temporalis muscle to cause rotation and displacement of the segment (Fig. 9). The area of dissection along the ramus is well away from the oralmucosa, andunlike osteotomies through the angle or body" particularly in patients with teeth, there is minimal risk of oral communication and consequent wound contamination. With use of this technique, not only can the angle and posterior border ofthe mandible be moved much farther forward than with dislocation, but the angle can also be rotated anteriorly and laterally to allow even better access. As important as the improved access is the consistency of this access. The amount of exposure is consistent and, unlike dislocation techniques, is not dependent on variations in the anatomy ofthe temporomandibular joint, or on joint mobility. Rigid internal fixation with adaptation of the plates before osteotomy is easily performed on this type of osteotomy and reduces the time neededfor the procedure to a minimum, ensures return ofpresurgical occlusion, and obviates the need for intermaxillaryfixation (wiringtheteethtogether). In our experience the vertical ramus osteotomy has provided uncompromised access, with little disruption in the normal flow of the surgical procedure. No inferior alveolar nerve injury has been experienced. The use of rigid internal fixation has provided immediate return of function, with no malocclusion. CONCLUSION The vertical ramus osteotomy can provide excellent exposure to the distal internal carotid artery between the angle of the mandible and the base of the skull. It has a low morbidity. The osteotomy can be performed through a standard carotid endarterectomy incision extending along the anterior border of the sternocleidomastoid muscle from the mastoid process to the sternoclavicular joint, and requires instrumentation readily available in the operating room. There is little risk of intraoral contamination, temporomandibular joint dysfunction, or inferior alveolar nerve injury. When bone plates are adapted before the osteotomy, little time is wasted in osteosynthesis, and postoperative malocclusion is virrually eliminated. Patients do not require mandibular immobilization, and their postoperative course is not unlike any patient undergoing routine carotid artery operation. This should be considered as an adjunct for enhancing access to the distal internal carotid artery when exposure is likely to be a problem. REFERENCES 1. Blaisdell W, Crawford ES, Cooley DA, De Bakey ME. Extt'acranial aneurysms of the carotid artery: report of seven cases. Postgrad Med 1962;32: Cantore GP, Delfini R, Mariottini A, Santoro A, Cascone P. Anterior displacement ofthe mandible for betterexposure of the distal segment of the extracranial carotid artery. Acta Neurochir (Wien) 1987;86: Fry RE, Fry WJ. Extracranial carotid artery injury. Surgery 1980;88: Fisher DF, Clagett GP, Parker ]I, et al. Mandibular subluxation for high carotid exposure. J VAse SURG 1984;1: Goldsmith MM, Postma DS, Jones DF. The surgical exposure ofpenetrating injuries to the carotid artery at the skull base. Otolaryngol Head Neck Surg 1984;42: Batzdorf U, Gregorius FK. Surgical exposure of the high cervical carotid artery: experimental study and review. Neurosurgery 1983;13: Balagura S, CarterIB, Bossett DL. Surgical approach to the high subcranial internal carotid artery. Neurosurgery 1985; 16: Dichtel W], Miller RH, Feliciano DV. Lateral mandibulotomy: a technique of exposure for penetrating injuries of the internal carotid artery at the base of skull. Laryngoscope 1984;94: Caldwell JH, Letterman GS. Vertical osteotomy in the mandibular rami for correction of prognathism. JOral Surg 1954;12: Adkin RK, Walters PJ. Experience with the intraoral vertical subcondylar osteotomy. J Oral Surg 1975;33: Hall HD, Chase DC, Payor LG. Evaluation and refinement of the intraoral vertical subcondylar osteotomy. J Oral Surg 1975;33: Submitted Mar. 14, 1991; accepted May 2, 1991.