Ultrasonic orthognathic surgery: enhancements to established osteotomies

Abstract

The use of a novel ultrasonic osteotome enabled the authors to modify well-established orthognathic osteotomies to more favourably address the anatomy. For this purpose, they utilized a powerful ultrasonic device with tissue-selective cutting characteristics that was originally developed for spinal osteotomies and nerve decompression (BoneScalpel™ by Misonix Inc., Farmingdale, NY, USA). Its straight ultrasonic blade was adapted for dual action, and a soft protective element was added. The product modifications and the related changes regarding maxillary and mandibular osteotomies are explained in detail. A series of 83 patients underwent orthognathic surgery with the BoneScalpel ultrasonic osteotome. All osteotomies within this study group were performed purely ultrasonically and without the auxiliary use of reciprocating saws or rotary burrs. The complications, alveolar nerve impairment and bad splits were assessed. To assess the quality of the lingual osteotomies and pterygomaxillary separation, three-dimensional scanning was performed on 30 patients. In conclusion, the BoneScalpel™ ultrasonic osteotome enabled improved control over orthognathic osteotomies and resulted in significant reductions in the occurrence of nerve impairment and bad splits.

Ultrasonic systems have been used for surgical soft tissue removal for several decades. Typical applications include laparoscopic dissection, resection of head and neck tumours, lipoplasty and the aspiration of spinal and intracranial tumours.

The concept of ultrasonic bone dissection was envisioned as early as the 1960s by McFall et al. In 2001, Vercellotti introduced an angled piezoelectric short saw, which presented benefits for osteotomies during oral surgery without causing damage to adjacent soft tissue. A number of Vercellotti-type devices have since been launched on the market (Piezosurgery 3, Piezosurgery Medical, Piezon Master, Variosurg, and Piezotome 2) and are often referred to as piezoelectric, piezosurgical or piezotome systems. Numerous comparative studies have been performed to determine their safety and efficacy in bone surgery. Multiple studies have evaluated the feasibility of piezoelectric surgery with Vercellotti-type devices as a substitute for the use of conventional saws and burrs in orthognathic surgery. Overall, these studies reported favourable reductions in blood loss, operative oedema and nerve injuries at the cost of an increased time investment due to insufficient cutting power for the mandible and the need for the auxiliary use of traditional burrs or saws.

In 2003, Hadeishi et al. reported the safe use of a non-Vercellotti-type ultrasonic bone curette (Sonopet by Miwatec Co., Inagi, Japan) for anterior clinoidectomies and opening the internal auditory canal without causing damage to the surrounding structures. Ueki et al. used this instrument in 2004 to perform pterygoid process fractures without damaging the surrounding tissues in 14 adults. Garzino-Demo et al. used it for resecting mandibular tumours involving the inferior alveolar nerve.

The most recent system on the market is the BoneScalpel™ ultrasonic osteotome (Misonix, Inc., Farmingdale, NY, USA). Originally developed for neurosurgical nerve decompression and spinal osteotomies, this device promises to combine the benefits of previous piezoelectric devices with improved ergonomics and cutting efficiency. The device features a straight blade with distally bevelled edges that can cleave into bone. In this approach, osseous or calcified tissue is transected by the recurring mechanical impacts of the blade edge at high and constant ultrasonic repetitions of 22,500 purely longitudinal strokes per second. This results in the controlled compression and splitting of rigid, crystalline structures, while soft and elastic tissues are generally able to deform temporarily to maintain their integrity.

Sanborn et al. reported favourably on the safety and efficacy of the BoneScalpel ultrasonic osteotome after performing laminectomies on an ovine model in 2011. Parker et al. recently presented a case series of 11 patients using the ultrasonic osteotome to perform osteoplastic laminoplasty during the resection of intradural spinal cord pathology.

Based on ergonomic and performance requirements for advanced orthognathic osteotomies, the authors selected the BoneScalpel ultrasonic osteotome for further study and collaborated with the manufacturer to optimize an existing blade for use in maxillofacial procedures.

Materials and methods

A novel ultrasonic osteotome (BoneScalpel ® by Misonix Inc., Farmingdale, NY) was used to perform maxillary and mandibular osteotomies. The standard blade has a straight configuration, is 20 mm long, and 1.0 mm thick. The distal tip has a rounded shape with bevelled surfaces forming a blunt forward-cutting edge. A central channel ensures the proper distribution of room-temperature irrigant to all cutting surfaces to provide cooling and lubrication, even when the blade is fully engaged in bone. The authors collaborated with the manufacturer to introduce several modifications. Blunt serrations allow bone dissection with one lateral side of the blade, while the contralateral side remains smooth for safe manoeuvring within the oral cavity. Depth markers are etched into the blade surface at 3, 5, 10, and 15 mm to gauge blade insertion. A soft, protective element made out of silicone and placed at the junction with the handpiece prevents burns to lips or mucosa. The blade length was subsequently extended to 30 mm to accommodate anatomical needs in the maxilla and mandible better ( Fig. 1 ).

Fig. 1
Modified ultrasonic blade for orthognathic surgery.

83 patients (40 males and 43 females) who were scheduled to undergo orthognathic surgery were prospectively enrolled in this study between August 2009 and June 2012 with the consent of the local ethics committee. The patients’ mean age at the time of surgery was 29 years (range 13–65 years). Patients with a previous history of orthognathic surgery were excluded from the study. The indications for surgery included the presence of dimorphisms in 71 patients and symptoms of sleep apnea in 12 patients.

The authors performed 49 Le Fort I osteotomies, 19 maxillary expansions, 5 mandibular expansions, 102 sagittal split osteotomies, and 8 genioplasties. In addition, they performed 40 bi-maxillary procedures. The 20 mm blade was utilized for all osteotomies in patients 1–67, and the 30 mm blade version was used in patients 68–83.

The BoneScalpel ultrasonic osteotome operates at a nominal, nonmodulated frequency of 22.5 kHz, and the amplitude of vibration ranges from 35 to 300 μm. While amplitude settings of 1–10 are available, the authors observed that a setting of 7 was well suited to the range of bone qualities encountered. Room temperature 0.9% saline solution is delivered through an integrated peristaltic pump that moves fluid through the central hand piece channel to the blade. The irrigant flow rate is adjustable from 15 to 80 ml/min, which corresponds to console settings of 20–100%. Irrigation at setting 100% was chosen to cool the bone and clean the surgical site.

All of the surgical procedures were performed by two senior surgeons while the patients were under general anaesthesia with nasal intubation. The third molars had been removed at least 9 months prior to the orthognathic procedure.

A control scan with a 2 mm thickness (GE Brightspeed) was obtained 2 days postoperatively, in accordance with recommendations made by the ethics committee. The authors examined the ideal bilateral separation between the maxillary tuberosity and the pterygoid plates. The mandible was digitally isolated from the maxilla and skull to observe the design of the split with OSIRIX Software ( Fig. 2 ).

Fig. 2
Coronal and 3D-reconstructed model views of the mandible.

The operative time was evaluated objectively with OPERA Software. Patients were questioned about the presence or absence of abnormal sensitivity. Outpatient follow-ups were performed at 15 days, 2 months and up to 3 years after each procedure.

Fracture lines were classified and compared with those reported in the literature. For the bilateral sagittal split osteotomy (BSSO), the subperiosteal preparations and dissections were performed as usual. The osteotomy was initiated at 45° on the lingual ramus side. The nonactive rigid blade in combination with the serrated profile allowed us to determine the geometry and consistency of the osseous surface ( Figs. 3 and 4 ). According to the preoperative scans, the blade tip penetrated on the oblique line deeply into the cortical bone at a 30° angle in the direction of the nerve canal without fear of harming the alveolar nerve ( Figs. 4 and 5 ).

Fig. 3
Cutting the lingual ramus.

Fig. 4
Cutting the lingual ramus and the oblique line.

Fig. 5
Cutting the oblique line of the mandible.

The vertical inferior osteotomy was performed to a level below the basilar region. The split manoeuvre was easily performed with manual rotation of the osteotomes.

For the Le Fort I osteotomies, the subperiosteal preparations and dissections were performed in the usual fashion through sulcular incisions. The straight ultrasonic blade was pulled around the maxillary tuberosity without visual control. The blade was inserted deeper than would be possible with a saw, without fear of causing haemorrhage, to weaken the pterygomaxillary junction and the posterior sinus wall ( Fig. 6 ). The blade was then brought back to the anterior sinus wall to penetrate the lateral nasal wall over the entire length of the septum ( Figs. 7 and 8 ).

Fig. 6
Cutting the tuberosity and the anterior sinus wall.

Fig. 7
Cutting the nasal wall.

Fig. 8
Lateral, medial and septal osteotomies.

An Obwegeser chisel was applied to all pterygomaxillary sutures, although the disjunction primarily occurred during the use of the ultrasonic device. The maxillary down-fracture was easily obtained with improved control due to an absence of bleeding.

Results

All 183 osteotomies in 83 patients in this study were performed with the use of the BoneScalpel ultrasonic osteotome. Its ability to engage bone deeply while maintaining an efficient cutting speed made the use of traditional power instruments, such as saws or burrs, unnecessary. The blade design, with its integrated central channel, was effective in providing irrigant at room temperature to all cutting surfaces, including those that were deep in the bone. Subjectively, the authors noted clear reductions in swelling and haematoma formation. In addition, the authors observed the complete absence of dental lesions, haemorrhage, facial palsy and perforations of the nasal mucosa. Only 2 cases were observed to have hypoesthesia (1.96%) of the intra-alveolar nerve. The patients were older and treated for symptoms of sleep apnea. An unsatisfactory split occurred only once (0.98%) during the first use of the 30 mm blade due to insufficient power transmission, which was rectified in subsequent cases. This patient had no disturbance of the nerve. Three patients who underwent sagittal split osteotomy developed an infection on the sagittal side (2.94%) due to poor dental hygiene but did not suffer any significant consequences.

Control scans performed after 2 days in patients 53–83 showed different patterns of lingual splitting according to the Plooij et al. classification and different patterns of pterygomaxillary separation according to Robinson and Hendy. The results for mandibular splitting were 64.8% using Hunsuck’s definition and zero bad splits ( Table 1 ). For the maxilla, 58.3% showed perfect separation of the pterygomaxillary junction without fracture of the pterygoid plates ( Table 2 ).

Table 1
Classification of mandibular fracture lines.
20 mm % 30 mm % Total Plooij
LSS1 18 60% 17 70% 64.8% 51.25%
LSS2 8 26.6% 4 16.6% 22.2% 13.75%
LSS3 4 13.4% 3 12.4% 13% 32.5%
LSS4 0 0% 0 0% 0% 2.5%
N 30 24 54 80
LSS1, vertical pattern of fracture line to inferior border of the mandible (‘true’ Hunsuck); LSS2, horizontal pattern of fracture line to posterior border of the ramus; LSS3, fracture line through the mandibular canal to the inferior border of the mandible; LSS4, other patterns such as a buccal plate fracture or a bad split.

Table 2
Comparison of maxillary fracture patterns in the literature.
20 mm 30 mm % Lanigan micro-saw Reinick curved Ost Laster Shark-fin Laster Obwegeser Koichiro Sonopet
HLF 0% 7.7% 4.1% 70% 30%
LLF 9% 19.2% 14.6% 19% 4% 50% 39.2%
MLF 4.6% 0% 2.08%
PCS + PTI 59.1% 57.7% 58.3% 81% 25% 100% 20% 24.3%
PCS + HLF 4.6% 3.8% 4.1%
PCS + LLF 22.7% 11.6% 16.6% 16.2%
Total PCS 86.4% 73% 79.1% 100% 20%
N 22 26 48 32 24 10 10 74
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Jan 24, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Ultrasonic orthognathic surgery: enhancements to established osteotomies
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