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British Journal of Oral and Maxillofacial Surgery 52 (2014) 219–222

Effectiveness of piezoelectric surgery in reducing surgical complications after bilateral sagittal split osteotomy Tatsuo Shirota a,∗ , Takaaki Kamatani a , Tetsutaro Yamaguchi b , Hiroshi Ogura c , Kotaro Maki b , Satoru Shintani a a

Department of Oral and Maxillofacial Surgery, School of Dentistry, Showa University, 2-1-1, Kita-senzoku, Ohta-ku, 145-8515 Tokyo, Japan Department of Orthodontics, School of Dentistry, Showa University, 2-1-1, Kita-senzoku, Ohta-ku, 145-8515 Tokyo, Japan c Department of Information Science, Faculty of Arts and Sciences at Fujiyoshida, Showa University, 4562, Kamiyoshida, Fujiyoshida, 403-0005 Yamanashi, Japan b

Accepted 28 November 2013 Available online 3 January 2014

Abstract Our aim was to investigate the effectiveness of piezoelectric surgery, where the osteotomy is made using ultrasonic vibration, in reducing surgical complications after bilateral sagittal split osteotomy (BSSO). Fifty-nine patients with skeletal mandibular prognathism who had mandibular setback with BSSO between January 2009 and April 2011 were included in the study. Piezosurgery was used in 29 cases, and the bone was split using a separator. In the remaining 30 cases, a Lindeman bur was used for the osteotomy and a chisel was used to split the bone. The amount of intraoperative bleeding and the Semmes Weinstein test scores were used as objective variables to evaluate the degree of neurosensory disturbance, and sex, age, use of piezosurgery, degree of setback, operating time, and method of fixation were used as explanatory variables. We used analysis of covariance (ANCOVA) to assess the significance of differences. Intraoperative bleeding was significantly less with age (p = 0.003), and longer when operating time was prolonged (p = 0.017), and was not influenced by the use of piezosurgery. The Semmes Weinstein test score significantly increased with age (p = 0.01), and was significantly greater when piezoelectric surgery was used (p = 0.008), and at 3 months, there were signs of more neurosensory disturbance in older patients and those who had had piezoelectric surgery. In this retrospective non-random study piezoelectric surgery reduced neither blood loss nor the incidence of neurosensory disturbance in BSSO. © 2013 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: Piezosurgery; Bilateral sagittal split osteotomy; Surgical complication

Introduction Bilateral sagittal split osteotomy (BSSO) is the most common mandibular corrective operation for skeletal malocclusion. As the mandibular body is moved by BSSO, there is a risk of excessive operative bleeding.1 There is also a risk of postoperative neurosensory damage to the inferior alveolar nerve because of the anatomical course of the mandibular canal.2



Corresponding author. Tel.: +81 3 3787 1151; fax: +81 3 5498 1543. E-mail address: [email protected] (T. Shirota).

Piezoelectric surgery uses ultrasonic vibration for osteotomy, and selectively removes the bone, which allows operations to be done with minimum invasion of the soft tissues such as blood vessels and nerves.3,4 Geha et al.5 used an ultrasonic bone scalpel for BSSO, and reported that the risk of operative nerve damage was lower than when rotary cutting instruments were used. However, many factors are involved. Not only the use of an ultrasonic bone scalpel, but also patients’ age, sex, degree of setback, operating time, and method of skeletal fixation may influence the degree of nerve damage and blood loss in orthognathic surgery.

0266-4356/$ – see front matter © 2013 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.bjoms.2013.11.015

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Table 1 Details of patients and clinical results. Variable

Mean (SD)

Range

Age (years) Setback (mm) Operating time (min) Total blood loss (ml) Semmes Weinstein test (Fmg)a

28 (9) 13 (4) 174 (37) 189 (113) 3.7 (0.8)

16–49 5–20 107–255 18–584 3.3–6.4

The amount of setback was measured as the distance from the mesial cusp of the mandibular first molar on the lateral cephalometric radiographs.

Evaluation of the postoperative neurosensory disturbance

a

Fmg is the value of the filament mark displayed on the Semmes Weinstein tester.

In the present study we analysed the effect of factors such as sex, age, use of piezoelectric surgery, degree of setback, operating time, and method of skeletal fixation on blood loss in BSSO and postoperative neurosensory damage.

Patients and methods The Ethics Committee of the School of Dentistry, Showa University, Tokyo, Japan approved the study. A total of 59 patients who had been diagnosed with skeletal mandibular prognathism between 2009 and 2011, and who had been treated by mandibular setback with BSSO by the same operator, were included. There were 24 men and 35 women, whose ages ranged from 16 to 49 (mean 28) years. Piezoelectric surgery was used for osteotomy in 30 cases, and a Lindeman bur fitted on to a straight handpiece was used in the remaining 29 (Table 1). Surgical technique We used the Epker method.6 When we used piezosurgery (Mectron Piezosurgery, Medical Technology, Carasco, GE, Italy) for the osteotomy, we made grooves in bone with a layer of cortical bone that did not reach the bone marrow using a fissure bur. Then the tip of an ultrasonic bone scalpel was pressed into these grooves to cut the cortical bone completely. The tip of the ultrasonic scalpel was inserted along the inner surface of the cortical bone of the mandibular ramus to cut the cancellous bone, and the bone was separated sagittally using a bone separator. In the patients who did not have piezosurgery the cortical bone was cut completely using a Lindeman bur followed by sagittal separation with a bone chisel. Semirigid fixation was achieved with an absorbable miniplate (Super-FIXSOR® -MX, Takiron Co., Ltd., Osaka, Japan) or titanium miniplate (Medicon Co., Ltd., Tuttlingen, Germany). The choice of whether piezoelectric surgery or a bone chisel was used was randomly selected by surgeons, as was the type of miniplate used, but biases such as surgeons’ opinions were not completely eliminated. All patients were given vitamin B12 supplementation in the form of methylcobalamin (Methycobal® , Eisai Co., Ltd. Tokyo, Japan) 1500 ␮g/day to promote early recovery from any neurosensory disturbance.7 This was continued until the disturbance had resolved.

Numbness of the lower lip was evaluated by the same examiner using the Semmes Weinstein sensory tester 3 months postoperatively. Data are expressed as Fmg, which is the value of the filament marking displayed by the tester. The patient was placed horizontally with the eyes open. The Semmes Weinstein tester was lowered vertically to the measurement point in about a minute, pressure was applied so that the filament bent slightly, and then the pressure was released after a minute. The measurement started from 1.65, the minimum marking number, and we gradually increased it until the patients felt the pressure. The first number that patients felt was regarded as the measurement. Three points including the vermilion, the transitional part of the vermilion, and the rest of the lip were measured on each side. The highest value of these was regarded as the Semmes Weinstein test value (Fmg).

Software We used the R2.12.0 software (freely available from , R Foundation for statistical Computing, Vienna, Austria) to assess the significance of differences between the groups.8

The causal connection between the left and right mandibular distance and Semmes Weinstein test value Correlations between the right and left setback, and Semmes Weinstein test values of the right lower lip and left lower lip, were confirmed by calculating the correlation matrix between right setback, left setback, right lower lip, and left lower lip. The results showed that there was a good correlation between right setback and left setback, and right lower lip and left lower lip, but there was no correlation between right setback, left setback, and right lower lip, left lower lip. To evaluate the setback and the Semmes Weinstein test value for each patient, the total amount of bilateral setback was regarded as the patient’s total setback. The total test value of the bilateral lower lip was regarded as the patient’s test value.

Influence of the use of piezoelectric surgery on the operating time The influence of the use of the ultrasonic bone scalpel on the duration of operation was analysed using the Wilcoxon rank sum test.

T. Shirota et al. / British Journal of Oral and Maxillofacial Surgery 52 (2014) 219–222

Fig. 1. Intraoperative bleeding as a function of the patients’ age. The amount of bleeding decreased significantly with increasing age.

Analysis of factors influencing blood loss and neurosensory disturbance Blood loss and the Semmes Weinstein test values (total value of right and left) were set as objective variables, and patients’ sex, age, use of piezoelectric surgery, amount of setback (total value of right and left), method of fixation, and operating time were set as explanatory variables. We made an analysis of covariance (ANCOVA) of the blood loss using the statistical model with explanatory variables. Those that did not differ significantly were omitted. A combination of explanatory variables with the minimum Akaike’s information criterion8 was explored, and regarded as the best analysis model. Probabilities of less than 0.05 were accepted as significant.

Results

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Fig. 2. Intraoperative bleeding as a function of operating time. The amount of bleeding rose significantly as operating time increased.

Fig. 3. The Semmes Weinstein test value as a function of the patients’ age. The value increased significantly higher with increasing age.

(p = 0.01; Fig. 3) and with the use of piezoelectric surgery (p = 0.02; Fig. 4).

The clinical results are shown in Table 1. Influence of piezoelectric surgery application on the operation time There was no significant difference in the duration of operation when the ultrasonic bone scalpel (p = 0.47). Analysis of factors that influenced operative bleeding and neurosensory disturbance The amount of bleeding was analysed with 3 explanatory variables including sex, age, and operating time. The result showed no significant difference depending on sex (p = 0.12), so sex was omitted. As a result, the analysis model with explanatory variables simplified from 6 to 2, sex and duration of operation, was decided to be the best model in ANCOVA, the results of which showed that the amount of bleeding decreased significantly with increasing age (p = 0.003; Fig. 1), and rose significantly the longer the operation (p = 0.02; Fig. 2). The analysis model with 2 simplified explanatory variables including age and piezoelectric surgery was decided to be the best for the Semmes Weinstein test value in ANCOVA. The test value increased significantly with increasing age

Discussion We set intraoperative bleeding and postoperative neurosensory disturbance as indicators of operative complications, and used ANCOVA to analyse the factors (sex, piezoelectric surgery application, amount of setback, and skeletal fixation method) that influence such complications. As the cortical

Fig. 4. The effect of piezoelectric surgery on reducing the risk of postoperative neurosensory disturbance after bilateral sagittal split osteotomy. The test value was significantly higher when the piezoelectric device was used.

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bone in the anterior margin of the mandibular ramus and buccal side of the mandibular body is thick, the BSSO with piezoelectric surgery took significantly longer than BSSO with rotary cutting instruments. We therefore presumed that the amount of bleeding in the piezoelectric surgery group would be greater than in the bur osteotomy group. In such cases it was difficult to evaluate the inhibitory effect of bleeding during piezosurgery and the influence of the duration of operation separately, so grooves were formed in the cortical bone using a Lindeman bur to reduce the operating time, followed by the osteotomy made with an ultrasonic scalpel. The results showed that there was no significant difference in the duration of operation between the bur osteotomy and piezoelectric surgery groups. Possible factors that may influence intraoperative bleeding during BSSO include sex, age, use of piezoelectric surgery, amount of setback, method of skeletal fixation, and operating time. We found that there was more operative bleeding in younger patients and with increased duration of operation, and piezosurgery did not reduce it. These results suggest that an accurate and prompt operation was key to the reduction of bleeding, and piezosurgery did not influence it. As we aimed to analyse factors that influenced the degree of postoperative nerve damage the Semmes-Weinstein monofilament mark (Fmg) was used as the value that indicated the amount of damage in individual cases. In previous reports, neurosensory damage after BSSO was estimated separately on each side.5,9 We regarded the total values on each side as the patient’s test value. Sex, age, use of piezoelectric surgery, amount of setback, method of skeletal fixation, and operating time were listed as potential factors that could influence the incidence of postoperative neurosensory damage. However, there was no significant difference in the test values with any of these factors except age and the use of piezosurgery, which suggests that these 2 factors influence postoperative neurosensory damage. The results suggest that patients who had piezosurgery and who were older had more neurosensory damage 3 months postoperatively. This result was contrary to our initial expectation. We assumed that the ultrasonic scalpel tip was deeply inserted into the bone marrow during osteotomy, and the tip directly stimulated the nerve tissue. When the cortical bone was resected using a Lindeman bur followed by splitting with a bone chisel, the space between bone chips opened as a result of the wedge effect as the bone chisel proceeded into the cancellous bone. The risk of directly stimulating the nerve tissue was therefore relatively low. The Semmes Weinstein test value in most subjects was 3.3 Fmg (1.65 Fmg on each side), which was within the reference range. We found no serious damage such as complete sensory palsy. Although the test value was significantly higher when piezoelectric surgery was used, the degree of sensory disturbance was mild. There was more operative bleeding in younger patients and with longer operations, and we could find no influence of the use of piezosurgery. In particular, it was not associated with a reduction in neurosensory damage 3 months after BSSO;

the rate in the piezosurgery group was actually higher than in the bur group. All patients had some return of sensation and the difference up to 18 months remains to be established. The postoperative recovery of damage to nerve tissue requires a long period of time, so long-term follow up is necessary. Although piezosurgery is superior to conventional rotary cutting instruments in many aspects, we failed to show that it reduced blood loss and neurosensory damage in BSSO.

Conflict of interest statement No sources of support in the form of the grant and no authors have any conflicts of interest to declare.

Ethical statement None.

Author’s contribution Conception and design of study/review/case series by Tatsuo Shirota. Acquisition of data: laboratory or clinical/literature search by Takaaki Kamatani and Tetsutaro Yamaguchi. Analysis and interpretation of data collected by Hiroshi Ogura. Drafting of article and/or critical revision by Tatsuo Shirota, Kotaro Maki and Satoru Shintani. Final approval and guarantor of manuscript by Tatsuo Shirota, Kotaro Maki and Satoru Shintani.

References 1. Lanigan DT, Hey J, West RA. Hemorrhage following mandibular osteotomies: a report of 21 cases. J Oral Maxillofac Surg 1991;49:713–24. 2. Bruckmoser E, Bulla M, Alacamlioglu Y, et al. Factors influencing neurosensory disturbance after bilateral sagittal split osteotomy: retrospective analysis after 6 and 12 months. Oral Surg Oral Med Oral Pathol Oral Radiol 2013;115:473–82. 3. Robiony M, Polini F, Costa F, et al. Endoscopically assisted intraoral vertical ramus osteotomy and piezoelectric surgery in mandibular prognathism. J Oral Maxillofac Surg 2007;65:2119–24. 4. Stübinger S, Kuttenberger J, Filippi A, et al. Intraoral piezosurgery: preliminary results of a new technique. J Oral Maxillofac Surg 2005;63:1283–7. 5. Geha A, Gleizal A, Nimeskern N, et al. Sensitivity of the inferior lip and chin following mandibular bilateral sagittal split osteotomy using piezosurgery. Plast Reconstr Surg 2006;118:1598–607. 6. Epker BN. Modifications in the sagittal osteotomy of the mandible. J Oral Surg 1977;35:157–9. 7. Okada K, Tanaka H, Temporin K, et al. Methylcobalamin increases Erk1/2 and Akt activities through the methylation cycle and promotes nerve regeneration in rat sciatic nerve injury model. Exp Neurol 2010;222:191–203. 8. Crawley M. Statistics: an introduction using R. Chichester: John Wiley; 2005. 9. Calabria F, Sllek L, Gugole F, et al. The use of sensory action potential to evaluate inferior alveolar nerve damage after orthognathic surgery. J Craniofac Surg 2013;24:514–7.

Effectiveness of piezoelectric surgery in reducing surgical complications after bilateral sagittal split osteotomy.

Our aim was to investigate the effectiveness of piezoelectric surgery, where the osteotomy is made using ultrasonic vibration, in reducing surgical co...
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