complications with orthognathic mandibular surgery part i presurgical and intraoperative...

SROMS 1 VOLUME 16.2

COMPLICATIONS WITH ORTHOGNATHIC MANDIBULAR SURGERY Part I

Presurgical and Intraoperative Complications.

Felice O’Ryan, DDS and Alessandro Silva, DDS, MS

INTRODUCTION

Complications with mandibular orthognathic surgery can, and do, happen to virtually all practitio-ners involved in the treatment of patients with dentofacial deformities. A thorough understanding and appreciation of the nature of the deformity, the biologic basis for the planned procedure, the probability of specific operative and postoperative problems and how to avoid and manage these, constitutes the core of knowledge required to successfully treat these patients. In this review complications pertain-ing to mandibular procedures are discussed relative to the type of surgery performed and the point at which the complication can be identified. Complications can occur with even the “simplest” of surgical procedures and during all phases of treatment. Appreciation of these problems provides the surgeon with the tools to maximize the surgical predictability while avoiding potentially untoward results.

The majority of patients undergoing man-dibular orthognathic surgery are ASA (American Society of Anesthesiology) status I or II and generally in good health. However, several fac-tors are important in determining the anesthetic risks and potential complications of this surgery. In addition to overall health, evaluation of the airway is essential in these patients. Patients with maxillary and mandibular deformities, especially mandibular hypoplasia, can be dif-ficult to intubate. Failure to manage the airway is the most significant cause of morbidity and mortality and this is especially significant in pa-tients with potentially difficult airways.1 Several bedside methods of airway assessment include maximal mouth opening, Mallampati classifica-tion,2 ratio of the patient’s height to thyromental distance (RHTMD) and BMI. Mallampati class

3 or 4 and RHTMD of greater than 23.5 are both predictive of difficulty with laryngoscopy and intubation.3 Planning for fiberoptic nasal intuba-tion is often prudent in such cases.

Body mass index (BMI) has been increasing at a rapid rate in the general population. Today, more patients undergoing elective surgery are obese. This is especially relevant in the subgroup of patients undergoing orthognathic surgery for correction of obstructive sleep apnea. In addition to a difficult airway, perioperative complications in the obese patient include infection, deep vein thromboses, cardiac events, urologic issues, positioning-related palsies and delayed extuba-tion.4 Adequate patient padding and application of pneumatic compression stockings should be routine, especially in the obese patient.

Mandibular Surgery Complications I F. O’Ryan DDS and A. Silva, DDS,

SROMS 2 VOLUME 16.2

Table I: Methods to Prevent Preoperative and Intraoperative Mandibular Complications

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SROMS 3 VOLUME 16.2

Factors that impair healing include diabetes mellitus and smoking status. Alpha et al. found a 66% prevalence of postoperative infections in diabetic patients undergoing maxillary and mandibular osteotomies, despite adequately con-trolled glucose levels.5 Hyperglycemia is associ-ated with impaired immune function and poor wound healing. Fasting blood glucose levels and glycosylated hemoglobin (HbA1c) values should be normalized prior to surgery. Smoking impairs the healing process and increases mor-bidity associated with most surgical procedures. With regard to musculoskeletal surgery, smoking has been recently shown to delay the chondro-genic phase of fracture healing.6 Preoperative smoking cessation at least three weeks prior to surgery can reduce the incidence of impaired wound healing.

Psychological assessment should be done prior to surgery. While this does not necessarily mean that all patients must undergo a psycho-logic evaluation, surgeon awareness of the psy-chologic issues influencing patient motivation for orthognathic surgery and postoperative satis-faction is important. The majority of patients are motivated by functional and esthetic concerns. Family or close friends, who are supportive of the surgery, realistic expectations and a compre-hensive understanding of the surgical course, including the risks and benefits, are important factors in assuring patient satisfaction with the surgery.7 The best advice regarding complica-tions is to try to prevent them. Recommendations from our personal experience in this regard are summarized in Table 1.

PREOPERATIVE PHASE

The preoperative phase consists of diag-nosis and treatment planning as well as any necessary presurgical orthodontics. Regardless of the type of mandibular surgery, certain basic preoperative orthodontic principles must be applied to reduce the chances for relapse and unacceptable results.8

Eliminate Dental Compensations

Dental compensations, to varying degrees, are present in the majority of patients undergo-ing orthognathic surgery. Decisions regarding dental extractions to eliminate these compensa-tions should be made at the beginning of treat-ment. Failure to remove dental compensations can contribute to compromised functional and esthetic results.

The primary goals of presurgical orthodon-tics are to place the teeth over basal bone, maxi-mize the surgical correction, and ensure dental stability.9 Removal of dental compensations can help counterbalance orthodontic and surgical relapse. Incisor position is heavily influenced by the decision to extract teeth.

Liberal extraction practices were largely halted with the teachings of Angle early in the 20th century.10 but were reversed in the mid-century with studies indicating improved orth-odontic results when certain cases were com-bined with extraction therapy. The pendulum has swung back to non-extraction orthodontic treatment in recent decades and this trend has occurred in surgical patients as well. Serial surveys of orthodontic diagnosis and treatment have indicated that the percentage of cases treated with extraction therapy has decreased from 34.9% in 1986 to 20% in 2002.11


SROMS 4 VOLUME 16.2

________________________________________________________________________________

Figure 1. A. Profile of a patient with mandibular hypopla-sia and microgenia. Failure to remove dental compen-sations prevented adequate mandibular advancement. B. Frontal, C. right and D. left views of postoperative occlusion.

A

B

C

D

In the patient with mandibular deficiency and a Class II division 1 malocclusion, dental compensations often include flared lower inci-sors. Proper position of the lower incisors (90º – 93º to the mandibular plane) is the presurgical orthodontic goal. Preoperative orthodontics should be directed toward uprighting the lower incisors and accentuating the Class II maloc-clusion before mandibular advancement. This can be achieved with appropriate extractions, if necessary, and class III elastics. Failure to remove these compensations prior to surgery reduces the magnitude of mandibular advance-ment and compromises the esthetic results if an advancement genioplasty is also needed (Fig. 1). The greater the proclination of the man-dibular incisors, the smaller the magnitude of mandibular advancement that can be achieved surgically. Additionally, lower incisor flaring increases the Holdaway ratio to greater than 1:1; and an advancement genioplasty, although nec-essary for proper esthetics, cannot be achieved without excessively deepening the labiomental fold (Fig. 2).

In the patient with mandibular progna-thism, who is planned for mandibular set-back, dental compensations are removed using the op-posite presurgical orthodontic mechanics. Dental compensations in the Class III patient commonly include flaring of the maxillary incisors and re-trusion of the mandibular incisors. Extractions may be necessary in the maxillary arch in order to properly position the maxillary incisors (i.e., 120º to the Frankfort plane or 102º – 104º to SN). Proper positioning of the dentition may also


SROMS 5 VOLUME 16.2

A B C

Figure 2. A. Starting lateral cephalometric radiograph and tracing of a patient with mandibular hypoplasia and a class II malocclusion. B. Mandibular dental model of same patient demonstrating crowding of mandibular incisors. C. Lateral cephalometric radiograph following 18 months of presurgical orthodontics demonstrating failure to remove dental compensations and resulting flaring of mandibular incisors. The Holdaway ratio is approximately 12:2 instead of 1:1.________________________________________________________________________________

include preoperative class II elastics. Fail-ure to remove compensations in the Class III patient can reduce the amount of mandibular set-back and maxillary advancement that can be achieved surgically (Fig. 3).

In patients with an accentuated curve of Spee and an accompanying Class II division 1 deep bite malocclusion, leveling of the oc-

Figure 3: A. Profile of a patient with midfacial hypoplasia and mandibular hyperplasia. Clinically, the patient is indicated for maxillary advancement and mandibular set-back. B. & C. Preorthodontic occlusion. D. Lateral cephalometric ra-diograph following presurgical orthodontics demonstrating failure to remove dental compensations resulting in severe flaring of the maxillary incisors. If surgery is done with the teeth in the current position there will be inadequate clinical correction of the midfacial hypoplasia.

________________________________________________________________________________

clusal plane is best done following mandibular advancement. The mandibular incisors should be left in the pre-orthodontic position and attempts to level the occlusal plane prior to surgery should be avoided. In such patients, increased lower facial length is needed and esthetic results will be superior if the leveling is accomplished fol-lowing surgery. The surgical orthodontic set-up is placed in a “tripod” position with contact of

A C

B

D


SROMS 6 VOLUME 16.2

Factors that impair healing include diabetes mellitus and smoking status. Alpha et al. found a 66% prevalence of postoperative infections in diabetic patients undergoing maxillary and mandibular osteotomies, despite adequately con-trolled glucose levels.5 Hyperglycemia is associ-ated with impaired immune function and poor wound healing. Fasting blood glucose levels and glycosylated hemoglobin (HbA1c) values should be normalized prior to surgery. Smoking impairs the healing process and increases mor-bidity associated with most surgical procedures. With regard to musculoskeletal surgery, smoking has been recently shown to delay the chondro-genic phase of fracture healing.6 Preoperative smoking cessation at least three weeks prior to surgery can reduce the incidence of impaired wound healing.

Psychological assessment should be done prior to surgery. While this does not necessarily mean that all patients must undergo a psycho-logic evaluation, surgeon awareness of the psy-chologic issues influencing patient motivation for orthognathic surgery and postoperative satis-faction is important. The majority of patients are motivated by functional and esthetic concerns. Family or close friends, who are supportive of the surgery, realistic expectations and a compre-hensive understanding of the surgical course, including the risks and benefits, are important factors in assuring patient satisfaction with the surgery.7 The best advice regarding complica-tions is to try to prevent them. Recommendations from our personal experience in this regard are summarized in Table 1.

PREOPERATIVE PHASE

The preoperative phase consists of diag-nosis and treatment planning as well as any

Figure 4. Patient with tooth size discrepancy not corrected prior to surgery. A. Anterior view, B. Right side. In order to achieve a Class I cuspid position there is no anterior coupling and an inadequate overbite. ____________________________________

necessary presurgical orthodontics. Regardless of the type of mandibular surgery, certain basic preoperative orthodontic principles must be applied to reduce the chances for relapse and unacceptable results.8

Eliminate Dental Compensations

Dental compensations, to varying degrees, are present in the majority of patients undergo-ing orthognathic surgery. Decisions regarding dental extractions to eliminate these compensa-tions should be made at the beginning of treat-

A

B


SROMS 7 VOLUME 16.2

ment. Failure to remove dental compensations can contribute to compromised functional and esthetic results.

The primary goals of presurgical orthodon-tics are to place the teeth over basal bone, maxi-mize the surgical correction, and ensure dental stability.9 Removal of dental compensations can help counterbalance orthodontic and surgical relapse. Incisor position is heavily influenced by the decision to extract teeth.

Liberal extraction practices were largely halted with the teachings of Angle early in the 20th century.10 but were reversed in the mid-century with studies indicating improved orth-odontic results when certain cases were com-bined with extraction therapy. The pendulum has swung back to non-extraction orthodontic treatment in recent decades and this trend has occurred in surgical patients as well. Serial surveys of orthodontic diagnosis and treatment have indicated that the percentage of cases treated with extraction therapy has decreased from 34.9% in 1986 to 20% in 2002.11

In the patient with mandibular deficiency and a Class II division 1 malocclusion, dental compensations often include flared lower inci-sors. Proper position of the lower incisors (90º – 93º to the mandibular plane) is the presurgical orthodontic goal. Preoperative orthodontics should be directed toward uprighting the lower incisors and accentuating the Class II maloc-clusion before mandibular advancement. This can be achieved with appropriate extractions, if necessary, and class III elastics. Failure to remove these compensations prior to surgery reduces the magnitude of mandibular advance-ment and compromises the esthetic results if an advancement genioplasty is also needed (Fig.

1). The greater the proclination of the man-dibular incisors, the smaller the magnitude of mandibular advancement that can be achieved surgically. Additionally, lower incisor flaring increases the Holdaway ratio to greater than 1:1; and an advancement genioplasty, although nec-essary for proper esthetics, cannot be achieved without excessively deepening the labiomental fold (Fig. 2).

In the patient with mandibular progna-thism, who is planned for mandibular set-back, dental compensations are removed using the op-posite presurgical orthodontic mechanics. Dental compensations in the Class III patient commonly include flaring of the maxillary incisors and re-trusion of the mandibular incisors. Extractions may be necessary in the maxillary arch in order to properly position the maxillary incisors (i.e., 120º to the Frankfort plane or 102º – 104º to SN). Proper positioning of the dentition may also include preoperative class II elastics. Failure to remove compensations in the Class III patient can reduce the amount of mandibular set-back and maxillary advancement that can be achieved surgically (Fig. 3).

In patients with an accentuated curve of Spee and an accompanying Class II division 1 deep bite malocclusion, leveling of the oc-clusal plane is best done following mandibular advancement. The mandibular incisors should be left in the pre-orthodontic position and attempts to level the occlusal plane prior to surgery should be avoided. In such patients, increased lower facial length is needed and esthetic results will be superior if the leveling is accomplished fol-lowing surgery. The surgical orthodontic set-up is placed in a “tripod” position with contact of


SROMS 8 VOLUME 16.2

the terminal molars and incisors. Postoperative leveling in these cases usually proceeds rela-tively quickly.

Properly Manage Transverse Discrepancies

Management of transverse discrepancies in children and adolescents by conventional orthodontic therapy is often successful. In adult patients (older than 16-18 years) with transverse maxillary deficiency orthopedic expansion primarily consists of alveolar or dental tipping with little or no basal skeletal movement.12 Orthodontic treatment of skeletal transverse maxillary deficiencies should be reserved for discrepancies of less than approximately 5 mm. In these cases, buccal orthodontic movement of the maxillary molars and lingual tipping of the mandibular molars can lead to a stable and predictable result. However, periodontal sta-tus and thickness of the alveolar buccal bone at the molar level may limit such maneuvers. Orthodontic or orthopedic maxillary expansion of more than 5 mm in adults can be unstable, potentially leading to gingival recession, buc-cal bone resorption, root fenestration and root resorption.121-14 Relapse of the expansion can lead to an anterior open bite because the effec-tive length of the maxillary molars is increased

Figure 5. A. Postoperative panorex of a patient who underwent sagittal ramus osteotomies for mandibular advancement with an unfavorable split that was salvaged during surgery. B. Stereolithographic model from CT-scan. Despite the placement of four bicortical screws a nonunion resulted and severe proximal segment rotation occurred.

A B

________________________________________________________________________________

resulting in clockwise (posterior) autorotation of the mandible. 15

Identify and Manage Tooth Size Discrepancies

A tooth size discrepancy, as determined with a Bolton’s analysis, is common in surgical patients. In the Class II patient with mandibular deficiency, failure to manage tooth size discrep-ancies may prevent the surgeon from achieving a Class I cuspid occlusion and proper anterior coupling with adequate overjet and overbite (Fig. 4).8 Tooth size discrepancies are best determined from models.

When a tooth size discrepancy is identified a decision should be made regarding the method and timing of treatment. We recommend treating tooth size discrepancies prior to surgery because this allows a better fit of the anterior occlusion, especially in the cuspid regions. Preoperative corrections include stripping the mandibular incisors, creating spaces distal to the maxillary lateral incisors or removing a mandibular inci-sor, depending upon the magnitude of the dis-crepancy. Spaces distal to the maxillary lateral incisors will allow a greater degree of mandibu-


SROMS 9 VOLUME 16.2

Figure 6. A & B. Failure to adequately transect the inferior border of the mandible is frequently the cause of a buc-cal plate fracture. C. Positioning a curved osteotome at the superior aspect of the osteotomy to D. assess whether or not the inferior border of the mandible is adequately transected. A small curved osteotome can be used to complete the inferior border osteotomy. E. Isolated dry mandible demonstrating a low buccal plate fracture. This can usually be repaired with a four-hole monocortical bone plate. F. Isolated dry mandible with four-hole plate fixing the low buccal plate fracture and completion of the sagittal split. Once repair of the buccal plate fracture has been done the sagittal split can be completed in the normal fashion.

A B

C D E

F


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lar advancement and assist the orthodontist in finishing the case, should relapse occur.

Ensure Proper Leveling and Root Divergence in Segmental Cases

Preoperative orthodontics in cases of seg-mental mandibular surgery can include leveling of the individual segments. It is important to assure proper leveling of the teeth adjacent to the osteotomy especially on the segment to be mobilized. For example, if a deep bite deformity exists and surgical intrusion of the anterior man-dibular segment is planned, a rainbow curve of Spee must be leveled so that the cuspids are not buried below the level of the occlusal plane when the segment is moved inferiorly. With segmental surgery inadequate space between the proposed tooth roots increases the likelihood of damage to adjacent tooth roots.

Prepare the Patient Psychologically for Surgery

Patients can be dissatisfied with a surgical success if there is a discrepancy between the ex-pected and experienced impacts of treatment on the patient’s life.16-18 Flanary found that effective, continuous communication between the patient, surgeon, and orthodontist was among the most important factors in patient satisfaction with the surgical results.19 Nagamine et al. found 14% of 65 patients who had surgical correction of mandibular prognathism were dissatisfied with their result.20 Among the primary reasons for dissatisfaction were forward relapse of the mandible and paresthesia of the lower lip.

With the advent of video imaging, patients have been able to visualize treatment results more clearly.21,22 One study has indicated that video image predictors were clinically accept-

able in cases of isolated mandibular surgery.23

INTRAOPERATIVE PHASE

Intraoperative complications are often due to improper surgical technique, failure to appreciate the patient’s anatomy or both. How-ever, unanticipated intraoperative complications can also occur. Intraoperative complications for various mandibular procedures will be divided into the following categories: 1) unfavorable osteotomy split, 2) nerve injury, 3) bleeding, 4) proximal segment malpositioning, and 5) miscellaneous technical difficulties.

Sagittal Ramus Osteotomy

The sagittal ramus osteotomy (SSRO) is among the most frequently performed surgi-cal procedures in the mandibular ramus. It is used both for mandibular advancement and mandibular set-back. The intraoral sagittal os-teotomy was first described by Schuchart.25,26 and was modified and popularized by Trauner and Obwegeser. 27,28 Obwegeser carried the medial osteotomy to the posterior border of the mandible and the vertical limb to the region of the antegonial notch.28 DalPont29 modified the osteotomy to extend further forward into the body of the mandible, and Hunsuck30 limited the extent of the medial cut to the retrolingular fovea. Epker further modified the technique by limiting the soft tissue dissection.31 Despite its frequent use, the sagittal ramus osteotomy is a technically difficult procedure.32-38

Unfavorable osteotomy split



Figure 7. A. Preoperative panorex of a patient with irregular condylar anatomy who was planned for a sagittal split ramus osteotomy. B. Isolated dry mandible showing where a high buccal plate fracture occurred intraoperatively. The condyle was still attached to the distal segment. C. The buccal plate was secured to the distal segment with bicortical screws and a vertical os-teotomy in the distal segment as described by Patterson and Bagby47. D. The mandible was advanced and the inferior alveolar nerve can be seen in the osteotomy gap (arrow). E. Allogeneic bone graft placed in the gap. F. Postoperative panorex showing the four-hole plate was utilized to stabilize the proximal and distal seg-ments. G. Postoperative PA cephalometric radiograph.

A B C

D E F

G



Figure 8. A. Lateral cephalometric and B. panorex radiographs on a patient with mandibular hypoplasia planned for man-dibular advancement and simultaneous removal of third molar teeth. C. Postoperative panorex demonstrating a through and through osteotomy of the proximal segment resulting in a free condylar process. D. 4 months postoperative panorex of the patient demonstrating counter-clockwise rotation of the proximal segment. E. TMJ tomogram of the right side with the patient in during maximal opening and F. in centric occlusion. Note that the condyle is far out of the fossa in centric occlusion.________________________________________________________________________________

A

B

C

D

E F

One of the most common problems asso-ciated with the sagittal split ramus osteotomy is unfavorable fracture of either the proximal or distal segment. Incidence rates as high as 18% have been reported for these types of frac-tures.37-41 One can either correct the bad split and

complete the operation or abort the procedure and allow the patient to heal. This decision must be made on a case by case basis. It may be the better part of valor to stop the operation, with a plan to reoperate after the bone has healed, if it appears unlikely that good bone contact can



Figure 9. A. Small fracture of the distal segment during SSRO. B. Comminuted fracture of the distal segment after application of force with a Smith spreader (Walter Lorenz Surgical, Jacksonville, Florida)._____________________________________

A B

be achieved (Fig. 5). It is far easier to reoperate a well healed mandible than to try to valiantly complete the procedure and end with a non-union due to poor bone contact.

Buccal Plate Fracture

Proximal segment fracture, also known as a buccal plate fracture, is the most frequent type of unfavorable split.42 Several contributing factors have been cited: presence of an impacted third molar, recent removal of a third molar, age of the patient, and extent of the surgeon’s experience.43

In an analysis of 1,256 patients who underwent sagittal osteotomy, Precious et al. found that fracture of the proximal segment was more common (70% versus 30%) than fracture of the distal segment.37 Berhman44 and later Turvey38 reported a 3% incidence of proximal segment fracture while MacIntosh39 found a 6.6% incidence of such fractures.

The role of impacted third molars in unfa-vorable splits is controversial. Precious et al. did

Figure 10. Incomplete transaction of the inferior border of the mandible may result in the inferior border remaining attached to the distal segment (arrow).

_____________________________________

not observe any relationship between proximal segment fractures and the presence of third mo-lars, but they did note a relationship with distal segment fractures when the third molars were present.37 Mehra et al.36 found that fracture of the distal segment occurred more often in younger patients with impacted third molars, whereas fracture of the proximal segment was seen more often in older patients without third molars. In a group of 70 patients, Reyneke et al. found 3 fractures of the distal segment and 1 fracture of the proximal segment.35 They observed that the presence of the third molars in young patients (less than 20 years-old) was correlated with a higher rate of unfavorable fractures.



Figure 11. Injury to the inferior alveolar nerve can occur during many phases of the SSRO. If the osteotomy is made too far medially the nerve can be caught in the proximal segment and stretched (arrow) during separa-tion of the proximal and distal segments._____________________________________

Some authors feel that removal of third mo-lars at least 6 months prior to SSRO is important in reducing the risk for adverse fractures while others feel that third molars do not predispose the patient to such problems.36,45,46 The direction of mandibular movement, degree of impaction of the third molar and experience of the surgeon are factors to be considered in the decision to remove third molars prior to an SSRO. Removal of the third molars at the time of orthognathic surgery helps reduce costs and avoids an addi-tional surgical procedure.

Fracture of the buccal plate most often occurs when the inferior border of the mandible is incompletely transected (Fig. 6A). In this situ-ation, the thin buccal plate is the area of least resistance and can be fractured by the force used to split the mandible (Fig. 6B). A buccal plate fracture makes the task of completing the split

technically difficult because the buccal plate is shortened, with less bone to pry against (Fig. 6C).

Mehra et al. did not describe their technique for completing the osteotomy after proximal segment fracture, but these authors stabilized the free proximal segment with a bone plate and monocortical screws. 36 In response to a “low” fracture of the buccal plate during sagittal split osteotomy, we recommend that the buccal plate be secured with a monocortical plate immedi-ately after it becomes fractured; the split should then be completed in the usual way (Fig. 6D). This technique is simple and quick, facilitates completion of the split, and might reduce dam-age to the inferior alveolar nerve that can occur when osteotomes are blindly used to finish the split.

When a high buccal plate fracture occurs near the mandibular condyle it can be more dif-ficult to plate the segment. Patterson and Bagby discussed fracture of the proximal segment and noted that completion of the split can be extremely difficult.47 To complete the split, they recommended lateral retraction of the remaining proximal segment and a vertical osteotomy of the distal segment. Although this procedure can limit the amount of advancement and can place the lingual nerve at risk from stretching or retrac-tion of the medial tissues we have found it useful in salvaging high buccal plate fractures (Fig. 7).

Coronoid Process Fractures

Fracture of the coronoid process of the mandible during SSRO is likely due to place-ment of the horizontal osteotomy is too high. If an osteotome is used, where the ramus is thin, it can penetrate the lateral ramus. Coronoid pro-



cess fractures can be avoided by ensuring that the horizontal cut is not carried too far laterally and is made just above the lingula where the mandible is relatively thick.

If the horizontal osteotomy is made in the thin part of the ramus, is made too deeply and carried to the posterior border of the mandible, a through-and-through osteotomy can occur, resulting in a free condyle-ramus segment (Fig. 8 on Page 12). This is among the most difficult types of unfavorable fractures to salvage. If possible, fix the fracture with an osteosynthesis plate, and either properly complete or abort the SSRO.

Other “Bad Splits”

Fracture of the distal segment during the sagittal osteotomy can occur36 if the distal seg-ment is weakened, by an impacted third molar or an edentulous molar area that causes thinning of the mandible in this region (Fig. 9). In such cases, care must be taken when using a Smith spreader (Walter Lorenz Surgical, Jacksonville Florida) to apply force to the distal segment. If the inferior border of the mandible is not completely transected during the osteotomy, the inferior border, which should be on the proxi-mal segment, will remain on the distal segment (Fig. 10).

Nerve Injury

Injury to the inferior alveolar nerve can oc-cur at many points during the SSRO. The nerve may be stretched or avulsed during the medial dissection; cut during the osteotomy with the bur, saw, or chisel; torn during separation of the proximal and distal segments; or injured during

stabilization of the proximal segment (Fig. 11 on Page 14). The area of damage and incidence of nerve injury during the SSPO are difficult to estimate from the literature. Aside from transection of the nerve, some have concluded that aggressive retraction of the medial tissues is among the prime causes of neurosensory dysfunction.48 Intraoperative management of a transected inferior alveolar nerve involves im-mediate microsurgical repair with a tension- free direct anastomosis.

White et al. did not report any instances of direct damage to the inferior alveolar or lingual nerves, yet they noted 14 of 32 surgical sites had paresthesia of the lower lip, and two patients ex-hibited unilateral lingual paresthesia.49 Behrman found that 24% of the surgeons in his study re-ported paresthesia of the inferior alveolar nerve in their patients, but only two surgeons reported actually injuring the nerve.44 MacIntosh did not discuss the percentage of direct nerve injuries but noted that “inferior alveolar nerve transec-tion occurred only rarely when the ramus was sectioned properly”.39 Turvey found that nerve transection was the most frequent intraoperative complication, occurring up to 5.5% of the time.38 Nerve transection was anterior to or in the third molar region in all instances. Van Merkesteyn et al. found a visible lesion of the inferior alveolar nerve in 7 of 124 sagittal ramus osteotomies.50 Raveh et al. recommended using chisels to initiate the split, but not completing it until the nerve was completely visualized.51 Even so, they found four lacerations of 206 nerves using this technique. Several authors have found a greater incidence of neurosensory deficits with bicorti-cal versus monocortical fixation,51,52 perhaps due to excessive compression during stabilization of the proximal segment.



Bleeding

Significant bleeding is seldom encountered with the SSRO today, due to greater operator experience and improved hypotensive anesthetic techniques. The incidence of major intraopera-tive hemorrhage has gone down from 38% in 197244 to 1% in 2005.53 The largest vessels in proximity are the maxillary artery and its branches (masseteric and inferior alveolar), retromandibular vein and facial artery and vein.

The maxillary artery, which courses medial to the neck of the mandibular condyle and gives rise to the masseteric and inferior alveolar arteries, is readily avoided with careful subperiosteal dissection on the medial surface of the mandible and proper placement of the horizontal osteotomy. The facial artery courses just beneath the inferior border of the mandible in the area of the antegonial notch. This is the area where the vertical aspect of the SSRO is made. Damage to the facial artery occurs from violation of the periosteum with an instrument or from the proximal segment itself after the split is completed. In most cases, control of the hemorrhage can be accomplished with packing or direct ligation of the artery.

Behrman reported the maxillary, inferior alveolar or facial arteries were the most com-mon sources of hemorrhage during the SSRO.44 Bleeding was most often encountered when dissecting or using a rotary instrument on the medial ramus during the horizontal osteotomy. In his report, two patients required ligation of the external carotid artery, which did not appreciably slow the bleeding.

In Turvey’s series in 1985, the incidence of troublesome hemorrhage from the inferior

alveolar and facial arteries was 1.2%.38 Van Mer-kesteyn et al. reported difficulty with bleeding from the inferior alveolar and facial arteries in 2 cases.50 Acebal-Bianco et al. reported lacera-tion of the facial artery in 2 cases of SSRO at the vertical limb of the osteotomy.54

Silva et al. reported intraoperative lacera-tion of a branch of the maxillary artery during an SSRO which resulted in a pseudoaneurysm.55 Limiting the posterior and superior extent of the medial dissection is also advised. Teltzrow and co-workers,53 in their report of 1264 patients, found the retromandibular vein was the most common source of severe hemorrhage during the SSRO.

Proximal Segment Malpositioning

Proximal segment position following man-dibular surgery has been shown to significantly influence postoperative mandibular stability, temporomandibular joint function, masticatory efficiency and facial aesthetics.56-59 Counter-clockwise rotation and condylar distraction are the most frequent positional changes of the proximal segment, although clockwise rotation of the segment can also occur. The effect of condylar position on mandibular stability will be discussed in a following article on postopera-tive complications. (See Selected Readings in Oral and Maxillofacial Surgery, Vol 16, #3) The incidence of proximal segment malpositioning is difficult to estimate from the literature, but reports range from 1% to as high as 75%.60-62

Schendel and Epker found that control of the proximal segment was the most significant



Figure 12. A. Isolated dry mandible showing an osteotomy is angled too far posteriorly instead of straight down toward the inferior border of the mandible, resulting in a subcondylar segment. B. Postoperative panorex of an intraoral vertical ramus oseotomy that inadvertently made a subcondylar segment.

A

B

aspect in stability and prevention of relapse fol-lowing an SSRO for mandibular advancement.63 Proximal segment rotation was more common when wire fixation was used for stabilization. Jonhsson et al. described an increase in the obtuseness of the gonial angle in 75% of the 57 patients who underwent sagittal ramus oste-otomies and suggested that proximal segment rotation may be a source of this problem.60 Van Merkesteryn et al. described proximal segment malposition in 3 of 124 cases.50

There are many techniques for proximal segment stabilization, each with advantages and disadvantages. The method of choice should be tailored for each patient and depends upon the patient’s anatomy, direction and magnitude of mandibular movement, passive adaptation ver-sus flaring of the proximal segment, and other technical variables as well as the patient’s past medical history.

Devices have been designed to duplicate the presurgical position of the proximal segment. Gerressen et al. reported no functional differ-ences in patients who underwent mandibular advancement or set-back with or without a con-dylar positioning device, and a greater incidence of TMJ dysfunction in the mandibular advance-ment group in whom the proximal segment positioning device was used.64 They concluded that using proximal positioning devices was not worth the inconvenience.

Minor Technical Difficulties

Minor technical difficulties include hernia-tion of the buccal fat pad and difficulty closing the incision.65 Herniation of the buccal fat pad occurs after tearing of the periosteum on the lateral aspect of the ramus and is often the result



Figure 13. A. Mandibular model demonstrating IVRO placed too far forward transecting the inferior alveolar canal. B. Preoperative and C. Postoperative panoramic radiographs of a patient who underwent maxillary osteotomy, intraoral vertical ramus osteotomies and a genioplasty. Note the IVRO is through the inferior alveolar canal (arrow).

A

B

C

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of using a sharp anterior border stripper. It can be avoided by using an anterior border stripper with rounded tips, limiting the amount of lateral dissection, and ensuring the dissection is main-tained in the subperiosteal plane.

Incision closure can be difficult if the inci-sion is placed too high in the attached gingiva. This can be especially troublesome when an acrylic splint is used. When an erupted third molar is removed in conjunction with the sagit-tal osteotomy the incision should be modified to include the extraction site.

MacIntosh described breaking a bur while performing the horizontal limb of the sagittal osteotomy.39 This rather common occurrence is due to excessive torquing of the rotary instru-ment while the bur is engaged in the bone. When this happens the broken piece can generally be

removed with a skin hook either prior to or after the split is completed.

Vertical Subcondylar Ramus Osteotomy

Correction of mandibular prognathism using the vertical ramus osteotomy (also known as the vertical subsigmoid osteotomy) is one of the simplest osteotomies to perform and is therefore very popular. Although the surgical approach was first described extraorally, the intraoral approach is performed most often today.

The vertical ramus osteotomy of the man-dible was first described by Caldwell and Let-terman in 1954 as a means to set the mandible back.66 It was performed from an extraoral approach until 1964 when Moose described an intraoral technique performed from the lingual



these arteries is torn, it is best to complete the osteotomy for adequate access to the torn vessel.

Proximal Segment Malpositioning

Bell cited difficulty controlling the proxi-mal segment as the major disadvantage of the IVRO.92 There is controversy regarding stabiliz-ing the proximal segment with this procedure, however many authors suggest no fixation or non-rigid fixation to allow functional positioning of the proximal segment.57,69,81,93 This functional positioning is thought to benefit the TMJ, es-pecially in those patients who suffer from pre-operative TMJ dysfunction. Detachment of the masseter and a portion of the temporalis muscles are necessary to carry out the IVRO. Excessive stripping of the lateral pterygoid muscle should be avoided to prevent potential proximal seg-

Figure 14. A. Mandibular model of an intraoral vertical ramus osteotomy with the proximal segment in the appropriate position lateral to the distal segment. B. Postoperative PA cephalometric radiograph of a patient who underwent maxil-lary osteotomy and intraoral vertical ramus osteotomies. Note the failure to lateralize the segement on the patient’s right side (arrow).

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A B

ment necrosis and severe condylar sag.

After the osteotomy is completed the proxi-mal segment must be “lateralized” (Fig. 14). Pull from the lateral pterygoid muscle may displace the segment antero-medially, anteriorly toward the articular eminence, medially or inferiorly. If the segment is displaced antero-medially the inferior alveolar neurovascular bundle may be torn as it enters the lingula. If the osteotomy is incomplete or if the segment is displaced pos-teriorly, proper set-back of the mandible might not be possible.

Tuinzing and Greebe reported 5 cases where the proximal segment was displaced medially during the vertical ramus osteotomy.76 Medial displacement resulted in an Eagle’s Syndrome-like condition in one of these five patients and necessitated surgical removal of the



ably due to inadequate stripping of the medial pterygoid muscle) and presented as a palpable and visual facial deformity at the angle of the mandible.

Van Merkesteyn et al. found proximal segment displacement in 8.8% of their vertical ramus osteotomies.50 They did not state in which direction the displacement occurred but noted that two patients required surgical reposition-ing of the condyle. Quinn and Wedell reported one case in which anterior displacement of the proximal segment ultimately required removal of the condyle with total joint replacement.88

When the proximal segment is not secured in position, the remaining soft tissue attachments are what maintains proper condylar position. Hall and MacKenna recommend leaving a por-tion of the medial pterygoid muscle attached to the proximal segment near the mandibular angle to minimize the chance for “condylar sag”.81 Walker feels that even if condylar sag is noted, normal masticatory function will seat the condyle.93

Minor technical difficulties

Minor technical difficulties include those already discussed with the sagittal ramus osteotomy technique, along with inability to reposition the distal segment the planned amount.57,75,94 Tuinzing and Greebe recommend removing a wedge-shaped piece of bone from the sigmoid notch in large set-backs.76 However, they note that this might be technically difficult, and the maxillary artery could be damaged. Braun and Sotereanos reported one case in which a unilateral styloidectomy was necessary to com-plete the mandibular set-back.94 They recom-

mended evaluating the styloid processes when mandibular set-back is planned with the vertical ramus osteotomy. When Hall and McKenna their osteotomies curved forward just beneath the lingula with simultaneous coronoidectomies they have reported no difficulty in repositioning the mandible up to 12 mm posteriorly.81

Inverted “L” osteotomy and “C” osteotomies

Both the inverted “L” and the “C” os-teotomies are used for correction of difficult and more unusual mandibular dysplasias. The intraoral inverted-L osteotomy for mandibular advancement is technically straight forward and has low morbidity.95 It has been adopted to reduce the frequency of postsurgical neu-rosensory disturbances.96 Some authors prefer the inverted-L osteotomy (with bone grafts) for large mandibular advancements, significant lengthening of posterior facial height or both. It has also been described for correction of open bite deformities.97 The intraoperative complica-tions with these procedures are similar to those already described with the IVRO, but because these procedures are infrequently used, the lit-erature is dated.

Mandibular Body and Symphysis Surgery

Surgical procedures in the mandibular body and symphysis consist of the subapical osteoto-mies (anterior, posterior or total), mandibular body osteotomy and mandibular symphyseal osteotomy (genioplasty).

Subapical Osteotomies

Subapical osteotomies are indicated for movement of dentoalveolar segments while



maintaining an intact inferior border of the mandible. The subapical osteotomy generally refers to an osteotomy of the anterior mandible (i.e., cuspids and incisors) and is typically used for leveling or setting back an anterior segment. The horizontal aspect of the osteotomy should be made at least 5 mm beneath the apices of the teeth in order to maintain tooth vitality, and provide an area for stabilization of the segment.

These cases often involve interdental osteotomies for which adequate root divergence is necessary to avoid root damage (Fig. 15). The buccal cortex can be thick, and the tooth roots are generally not visible through it. Root diver-gence is best assessed from properly angulated periapical radiographs.

Sher, in his 1984 survey of complications with subapical surgery, found that most sur-geons recommend using fine osteotomes rather than saws for interdental cuts.98 The buccal cortex is cut with a bur or saw blade and the remainder of the osteotomy is completed with a fine osteotome. If an extraction and interdental ostectomy are planned, care must be taken at the inferior aspect of the osteotomy where adjacent tooth roots may converge toward the surgical site. Additionally, the anterior segment must be properly leveled prior to surgery to avoid placing the most proximal teeth (usually the cuspids) be-neath the level of the mandibular occlusal plane.

The total subapical osteotomy involves movement of the entire mandibular dentoalveo-lus, and is primarily used to treat dentoalveolar retrusion when pogonion position and projec-tion are normal. As with the anterior subapical osteotomy, the horizontal osteotomy should be made at least 5 mm beneath the root apices. In-

Figure 15. A. Preoperative panoramic radiograph of a patient who was planned for sagittal ramus osteotomies and an anterior mandibular subapical osteotomy. B. Postoperative panoramic radiograph following SSRO and anterior subapical osteotomy. The mandibular left first premolar tooth was extracted and the right first premolar was transected with the root remaining in the subapical segment. C. Close up of subapical osteotomy showing transected right first premolar with the root fragment in the subapical segment.

A

B

C



Some surgeons cite inadequate stabilization of the mobilized segment as a difficulty with seg-mental surgery,98 unless rigid fixation is used.

Inadequate trimming is the most common problem encountered, especially if the subapical segment is intruded. In such cases, trimming of the intact mandible on the inferior or lingual surfaces might be necessary in order to allow stable repositioning of the mobilized segment. Bone trimming is required most often on the lingual aspect of the mandible. Visualization can be difficult, and excessive manipulation of the mobilized segment can cause stripping or tearing of the soft tissue pedicle. Because small segments in the mandible are dependent upon the soft tissue pedicle, the inferior alveolar artery or both as their primary sources of blood. Stretch-ing or tearing these tissues can compromise postoperative healing, with a wide spectrum of sequelae.103

It is essential to remove all bony inter-ferences so that the mobilized segment can be placed passively into proper position without stripping the vascular pedicles. Sher recom-mended leaving the crestal bone intact until all of the interdental osteotomies have been com-pleted to avoid tearing the gingival pedicle.98 The crestal gingiva should be carefully manipulated so it is not torn or crushed between the segments

Furthermore, inadequate bone removal can result in malpositioning of the mobilized segment, especially if a thin flexible acrylic splint is used. Accurate model surgery, judicious duplication of the model surgery intraoperatively and the use of a thick non-flexible acrylic splint, all help prevent this problem.

dividuals with dentoalveolar retrusion generally are brachycephalic with vertical defi-ciency of the mandible. In such cases, it can be difficult to maintain an adequate stable inferior border segment, leading to fracture of the infe-rior border of the mandible if there is less than 9 mm between the root apices and the inferior border of the mandible.99 Such fractures can generally be treated with a titanium bone plates, much as one would for a mandible fracture. After treatment of the fracture the mobilized dentoalveolar segment is stabilized in the normal fashion.

Nerve Injury

Performing the total subapical osteotomy can involve considerable manipulation of the inferior alveolar nerve (IAN), especially if de-cortication is required.8,92,100 The mental nerve is located approximately 4.5 mm inferior to the mental foramen prior to its exit.101 If decortica-tion of the IAN is not planned the osteotomy should be at least 6 mm beneath the mental foramen.102

Bleeding

Hemorrhage has not been reported as a significant intraoperative complication with mandibular body surgery. The most likely source of excess intraoperative bleeding would be the inferior alveolar artery, and bleeding here which can usually be adequately controlled with pack-ing and other direct measures.

Malpositioning of the Mobilized Segment

Several factors can contribute to improper positioning of the mobilized segment during mandibular subapical or body osteotomies.



Mandibular Symphyseal Osteotomy (Genioplasty)

The bony genioplasty is among the most commonly performed surgical procedures in orthognathic surgery. It is generally a safe and quick procedure with few intraoperative compli-cations.74,104,105 Lindquist & Obeid encountered no intraoperative complications in 31 patients who underwent genioplasties.105

Unfavorable Osteotomy

For the horizontal osteotomy of the man-dibular symphysis the midline is marked and the osteotomy is usually performed with either a reciprocating or oscillating saw. The use of osteotomes is generally not necessary, nor is it recommended. Goracy reported fracture of the mandibular body and ramus during mobilization of the symphyseal segment while performing a genioplasty.104 This was most likely due to an incomplete osteotomy of the symphysis and the use of excessive force and torque with an osteo-tome in attempting to downfracture the genial segment. Osteotomes should be reserved for checking completion of the osteotomy and bone cutting should be performed with saws or burs.

Care must be taken when performing the osteotomy to insure that the bone cut is at least 5 mm below the apices of the mandibular teeth. This may be difficult in the brachycephalic patient in whom the anterior mandibular height is less than normal.106,107 Measurement of the length and position of the teeth is best accom-plished from periapical radiographs. Care must also be taken to insure that bone cuts are sym-metrical.

Nerve Injury

The mental nerve is the nerve most likely injured during the genioplasty. It courses approximately 4.5 mm to 5.5 mm beneath the mental foramen101,108 and is located in the region of the second premolar. The mental nerve exits the foramen and travels upward to the lower lip where it lies just beneath the mucosa. The mental nerve can be cut if the soft tissue incision, which is generally made through the bellies of the men-talis muscles in the lower lip, is carried too far laterally. The nerve can be stretched excessively or avulsed from the mental foramen during the initial dissection or when retractors are used during the osteotomy. It can also be cut during the osteotomy itself (Fig. 16) if the course of the mental nerve inferiorly within the bony canal is not appreciated.

Bleeding

Damaging lingual soft tissues with the saw during the osteotomy can cause intraoperative bleeding. Placing the saw deep to the lingual cor-tex can damage the genioglossus and geniohyoid muscles and lacerate the sublingual or submental arteries. This can be avoided by noting the width of the symphysis on the preoperative lateral cephalometric radiograph and not allowing the saw to penetrate too far beyond this depth. When excess bleeding does occur it is usually from severing the submental or mylohyoid arteries with the saw blade.105

The submental artery branches off the facial artery between 4 mm and 7 mm in front of the mandibular angle. It runs just beneath the inferior border of the mandible (approximately 7 mm) and courses deep to the anterior digastic muscle. The sublingual artery arises at the anterior margin of the hyoglossus, and runs for-ward between the genioglossus and mylohyoid



Figure 16. A. Preoperative PA cephalometric and B. Panoramic radiographs in a patient planned for bimaxillary surgery and an advancement genioplasty. No preoperative asymmetry was present. C. Postoperative panoramic radiograph demonstrating asymmetric position of the mobilized genioplasty segment.________________________________________________________________________________

muscles to the sublingual gland. One branch courses behind the alveolar process of the mandible in the substance of the sublingual gland and anastomoses with its contralateral counterpart; another pierces the mylohyoid muscle and anastomoses with the submental branch of the external maxillary artery.109 Excess bleeding can usually be controlled with packing and local measures. However, reports of severe bleeding from laceration of the sublingual artery exist.11

Malpositioning of Mobilized Segment

Advancement of the mobilized segment must also be symmetric unless an asymmetric move is planned. Failure to appreciate intraop-erative asymmetries can result in postoperative asymmetry of the chin (Fig.17). There are many methods of assuring intraoperative symmetry including skin marking, making a wide incision

Figure 17. Postoperative panorex demonstrating improper placement of osteotomy for genioplasty. Osteotomy was too high and transected both mental nerves.

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and vertically scoring the anterior mandible. Davis described a simple technique of skin marking to assist in maintaining symmetry of the chin during a genioplasty.111 The chin segment is typically stabilized with monocortical plates and screws or bicortical screws.

A

B

C



Figure 18. A. Oblique and B. Lateral views of perforation of the skin with reciprocating saw blade during genioplasty. Discoloration of the skin and adherence to underlying bone resulted in a visible depression.________________________________________________________________________________

A B

Figure 19. A. Panorex demonstrating transection of the anterior aspect of the bone plate which was used to stabilize the sagittal ramus osteotomy. B. This resulted in rotation of the proximal segment postoperatively.

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A B

The genioplasty is generally performed bimanually with one hand directing the saw and the other hand palpating the skin adjacent to the saw blade to ensure that the osteotomy completely transects the thick inferior border of the mandible laterally. Palpation of the skin in this area should be done gently, because pushing the skin firmly or poor control of the saw blade can result in perforation of the skin with the saw blade. Any lacerations should be repaired with 5-0 nylon suture. Despite repair, scarring in this area can lead to an indentation and a visible or pigmented scar especially in patients with thin tissues (Fig. 18). Treatment of such defects involves injection of soft tissue fillers.

The genioplasty is usually performed after completion and stabilization of the mandibular osteotomies. If bone plates are to stabilize SSRO segments, care must be taken to ensure that the genioplasty’s osteotomy is in front of or beneath the hardware. Otherwise, the plates could be transected with the reciprocating saw, and if this goes unnoticed the proximal segment will be unstable (Fig. 19).

Placing the soft tissue incision too high in the vestibule can make incision closure difficult, resulting in scar bands and periodontal problems. Closure of the incision should include reap-



proximation of the mentalis muscula-ture.107,112-115 The closure must be symmetric. The bandage should be placed symmetrically for support of the mentalis muscles and with minimal pressure.

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Dr. Felice S. O’Ryan received her DDS from University of Pacifico, San Francisco, California. She received her residency training in oral and maxillofacial surgery at Univer-sity of Texas Southwestern Medical Center and Parkland Memorial Hospital, Dallas, Texas. She is currently Head of the Division of Maxil-lofacial Surgery at Kaiser Permanente Hospital, Oakland, California. She is also an Associated Professor of the Division of Oral and Maxil-lofacial Surgery at Highland General Hospital, Oakland, California. Dr. Felice O’Ryan is on the editorial board of the Journal of Oral and Maxillofacial Surgery and a Founding Editor of the Selected Readings in Oral and Maxillofacial Surgery. Dr. Felice O’Ryan focuses her private practice in orthognathic and cosmetic surgery, facial trauma repair and obstructive sleep apnea.

Dr. Alessandro Silva received his D.D.S. from Unimes University (Santos Dental School), in Santos, SP, Brazil. He received his residency training and his MS degree in oral and maxil-lofacial surgery at Piracicaba Dental School (Unicamp), Piracicaba, SP, Brazil. He received his fellowship in orthognathic surgery at Kaiser Permanente Hospital, Oakland, CA, USA. He is currently PhD student in oral and maxillofa-cial surgery at Sao Paulo Dental School (USP),

Assistant Professor of Oral and Maxillofacial Surgery at Fundecto (USP) and Assistant Profes-sor of Implantology at Piracicaba Dental School (Unicamp). Dr. Alessandro Silva focuses his private practice in orthognathic and cosmetic surgery, facial trauma repair, obstructive sleep apnea and implantology.

AKNOWLEDGEMENTS: Selected Read-ings in Oral and Maxillofacial Surgery thanks Dr. Timothy A. Turvey for permission to reprint this chapter from Fonsecas’s Oral and Maxil-lofacial Surgery, Vol. 3



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complications with orthognathic mandibular surgery part i presurgical and intraoperative...

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