Cold Ablation Robot-Guided Laser Osteotome (CARLO®): From Bench to Bedside

Abstract

Background: In order to overcome the geometrical and physical limitations of conventional rotating and piezosurgery instruments used to perform bone osteotomies, as well as the difficulties in translating digital planning to the operating room, a stand-alone robot-guided laser system has been developed by Advanced Osteotomy Tools, a Swiss start-up company. We present our experiences of the first-in-man use of the Cold Ablation Robot-guided Laser Osteotome (CARLO^®).

Methods: The CARLO^® device employs a stand-alone 2.94-µm erbium-doped yttrium aluminum garnet (Er:YAG) laser mounted on a robotic arm. A 19-year-old patient provided informed consent to undergo bimaxillary orthognathic surgery. A linear Le Fort I midface osteotomy was digitally planned and transferred to the CARLO^® device. The linear part of the Le Fort I osteotomy was performed autonomously by the CARLO^® device under direct visual control. All pre-, intra-, and postoperative technical difficulties and safety issues were documented. Accuracy was analyzed by superimposing pre- and postoperative computed tomography images.

Results: The CARLO^® device performed the linear osteotomy without any technical or safety issues. There was a maximum difference of 0.8 mm between the planned and performed osteotomies, with a root-mean-square error of 1.0 mm. The patient showed normal postoperative healing with no complications.

Conclusion: The newly developed stand-alone CARLO^® device could be a useful alternative to conventional burs, drills, and piezosurgery instruments for performing osteotomies. However, the technical workflow concerning the positioning and fixation of the target marker and the implementation of active depth control still need to be improved. Further research to assess safety and accuracy is also necessary, especially at osteotomy sites where direct visual control is not possible. Finally, cost-effectiveness analysis comparing the use of the CARLO^® device with gold-standard surgery protocols will help to define the role of the CARLO^® device in the surgical landscape.

Keywords: CARLO®; midface; orthognathic surgery; osteotomy; robot-guided laser.

Figure 1

Cold Ablation Robot-guided Laser Osteotome (CARLO^®) developed by Advanced Osteotomy Tools (AOT AG, Basel, Switzerland) consisting of a laser head mounted on a robotic arm and guided by an optical navigation system.

Figure 2

Segmentation of the cranium (green) and maxilla (brown) with preoperatively planned and intraoperatively adjusted osteotomy lines. (A): Preoperatively planned left and right linear midface osteotomy lines in Mimics. This model is exported as an STL file and then imported into the software of the CARLO^® device. (B): Intraoperatively adjusted osteotomy line on the right side of the maxilla, marked in blue.

Figure 3

Intraoperative position of the CARLO^® navigation system on the left side of the patient with the navigation marker attached to the hard palate using two 11.0-mm self-drilling intermaxillary fixation (IMF) screws. The white goggles provide ocular protection during laser cutting. The graphical user interface on the left side of the patient provides real-time visual information about the operating area obtained by a camera embedded in the laser head and about the bone thickness in the form of a histogram. Auditory feedback informs the surgeon when the osteotomy is completed.

Figure 4

Screenshot of the registration points used for point-based registration of the patient’s skull to the digital model imported into the software of the CARLO^® device. The osteotomy line on the right maxilla can be adjusted intraoperatively directly in the software of the CARLO^® device; the adjustment made is shown in red.

Figure 5

Intraoperative photograph obtained during a linear Le Fort I osteotomy of the right maxilla performed with the CARLO^® device. Soft tissue was retracted using two black malleable orbital retractors placed behind the tuber maxillae and apertura piriformis. The registration marker was attached to the palate using two 11.0-mm self-drilling IMF screws and positioned in direct sight of the optical camera system on the left side of the patient. The coaxially oriented noncutting green laser beam indicates the location of the osteotomy line.

Figure 6

Superimposed preoperative (green) and postoperative (blue) segmented maxillae based on the intraoral dental surface scan (red). (A): Preoperative maxilla with an intraoperatively adjusted osteotomy line that was imported into Mimics. The intraoperatively adjusted osteotomy line on the right side of the maxilla is shown in blue, and the aligned dental surface scan is shown in red. The measured distances from the mesiobuccal cusps of the left and right upper molars to the lateral osteotomy line and from both incisors to the medial osteotomy line are shown. (B): Postoperative maxilla segmented in Mimics aligned with the dental surface scan shown in red. (C): Superimposition of the two maxillae based on the aligned dental surface scan. The measurements for each landmark are presented in pairs, with those on the left and right representing the planned and performed osteotomies, respectively. The difference was 0.03 mm from the mesiobuccal cusp of tooth 16 to the right lateral osteotomy line, 0.51 mm from the mesial surface of tooth 11 to the right medial osteotomy line, 0.45 mm from the mesial surface of tooth 21 to the left medial osteotomy line, and 0.79 mm from the mesiobuccal cusp of tooth 26 to the left lateral osteotomy line.