GMS CURAC 2006;1:Doc11 The electronic version of this article is the complete one and can be found online at: http://www.egms.de/en/journals/curac/2006-1/curac000011.shtml

Integration of a Robotic system in the neurosurgical operation theatre

Engelhardt M1, Popovic A2, Bast P, Lauer W, Scholz M, Radermacher K, Schmieder K

Authors 1 and 2 contribute equally to the authorship of this paper

Popovic Aleksandra, Institute for Biomedical Technologies, Aachen University, Aachen Germany Mail: [email protected] Bast Pierre, Institute for Biomedical Technologies, Aachen University, Aachen, Germany Mail: [email protected] Lauer Wolfgang, Institute for Biomedical Technologies, Aachen University, Aachen, Germany Mail: [email protected] Scholz Martin, Department of Neurosurgery, Ruhr University Bochum, Bochum, Germany Mail: [email protected] Radermacher Klaus, Institute for Biomedical Technologies, Aachen University, Aachen, Germany Mail: [email protected] Schmieder Kirsten, Department of Neurosurgery, Ruhr University Bochum, Bochum, Germany Mail: [email protected]

Corresponding Author:

Dr. Martin Engelhardt Neurochirurgische Universitätsklinik Ruhr-Universität Bochum Knappschaftskrankenhaus In der Schornau 23-25 44892 Bochum Germany Tel.: 0234/299-3602 Fax: 0234/299-3609 Mail: [email protected]

Abstract To integrate a robot assisted trepanation system into the neurosurgical operation theatre, requirements of the system have to be addressed. To perform a craniectomy with removal of the pathological calvaria the results of a study concerning the entities, the location and the histological findings of calvarial tumors had to be considered. Furthermore, the small space around the patients´ head during surgery, the work angles in surgical procedures as well as the possible positioning of the robotic system and its design have been analyzed. Sterile and ergonomic aspects have been adjusted and proven to fulfill the requirements of the workflow during surgery. The result is a small hexapod robotic system, which is placed beneath the patients´ head on a replaceable stage, able to reach the majority of calvarial tumors that are typically located around the forehead. The handling of the hardware as well as the software userinterface is appropriate to be integrated into the operation theatre.

Keywords: neurosurgery, robotic assisted surgery, craniotomy, workflow

Introduction Integration of a robotic system into surgical procedures is one important goal of research efforts for man-machine interlinked systems [1-5]. An interdisciplinary work group, consisting of engineers and clinicians, supported by the German Research Foundation (Deutsche Forschungsgemeinschaft SPP1124 „Medizinische Navigation und Robotik“, RA548/2-1), has successfully developed a small robotic system capable of drilling bone under navigational control [6,7,8]. The aim of this study was to analyze the integration of the robotic system in the operation theatre fulfilling the different criteria of accurate and sufficient bone milling, sterile workflow, limited workspace, and handling of instruments to perform the craniectomy. Some other robotic systems were removed from the medical market because of handling and safety problems during surgery. Most of them are bulky and heavy and space occupying [9,10] and the integrating into surgical workflow is difficult. Other obstacles are high costs and weight of robotic systems, which alters the current workflow or requires some changes in the operation theatre concerning architecture or general surgical planning [11]. Thus, the developed system should be mobile in the operation theatre and must not interfere with standard procedures, if possible.

Methods Firstly, the workspace for the robotic system had to be defined, analyzing surgically treated calvarial tumors within a ten-year period. Therefore, ten years were analyzed retrospectively to characterize calvarial tumors concerning their locations, sizes and histological findings [12,13]. Furthermore, the currently most frequent used trepanations in neurosurgery were defined. Their dimensions and topography on the surface of the skull were marked to determine the robot’s work area needed for craniectomies for the actual phase of the project and for craniotomies in further development. The possible working area of the hexapod robotic system was analyzed and correlated to the main calvarial tumor’s location. In the next step the setting in the neurosurgical theatre was analyzed to define the optimal location of the robotic system. The analysis was done using digital documentation and measurements of patients positioning and dimensions around the patient’s head during surgery. In this virtual reality the optimal location of the robotic system was simulated and resulting requirements for the robotic system including all criteria for positioning, handling and sterile workflow were addressed. In a final step the handling of the robotic system was tested several times concerning practicability of hardware integration and appreciation of software instructions. Important ergonomic aspects were determined and added to optimize the design of the robotic system and the user guidance software.

Results As the retrospective study demonstrated, 87% of 83 surgically treated osseous tumors were located in the frontal, the temporal and the anterior parietal region of the skull (Table 1), as shown in the example (Fig.1). This vizor-like workspace has to be reached using trepanation tools. Additionally, most of the standard trepanations are located in similar shaped areas (Fig.2). Since the Stewart platform based parallel robots’ workspace has a shape that resembles an opened umbrella (Fig. 3) craniotomy geometries shown in Fig. 2 are very suitable for the resection with the robot. In order to evaluate the robots’ workspace and determine the optimal position of the platform in relation to the patient placed in supine position, fixed with the Mayfield clamp, a virtual model of the skull was used. The skull was simulated using a sphere with a 200 mm diameter, milling area with angle of 70° to reflection axis with the maximum tool angle of 25°. Following the virtual simulation the optimal position of the patient and the robotic system due to its working area was found to be beneath the operation table directly under the patients´ head (Fig.4). The system was divided into the lower part containing the electrics with the control unit and the leg motors (Fig.4). The mechanical upper part consists of a strong removable C-shaped arm. The upper part of the arm can be sterilized before the procedure. The surgical instruments are fixed to the C-shaped arm to realize high accuracy during the milling procedure (Fig.4). The entire system is placed on a replaceable stage to allow easier handling and prepositioning. The usability was proved in simulated surgical surroundings by several surgeons and engineers and an easy workflow was used to achieve a sterile management during surgery. Furthermore, the instructing user-interface has been evaluated during simulation and was revised with some additional hints and pictograms. The important aspect in medical robotics is the safety of patient and OR team during the surgery. Prior to the design of the robot with a control system, a risk analysis based both on fault-tree and failure mode and effect analysis had been performed. As a result a need for a redundant hardware for enhancement of the system safety emerged. This safety unit was designed as a stand-alone system, connected between the control unit and manipulator. Safety hardware continuously inspects various values and signals, e.g. motor and amplifier signals. If an error is detected, the safety unit will execute an emergency stop, e.g. by turning the motor brakes. Ending the adaptation of this new robotic system within a simulated surgical setting, test courses were done (Fig.5), including positioning of the virtual patient and the robotic system and installation of the neuronavigation.

Discussion: Compared to other robotic systems [2,3], which are available for medical requirements, the actual system of this group is smaller and easier to be moved, which could be important within the surgical procedure and workflow. If necessary it can easily be removed and after fulfilling its task the presence of the lower part of the system doesn’t obstruct the surgeon to continue surgery. During surgery the small dimensions of the system is well matched with the small surgical area around the patients´ head. The system is self-explaining with the user-guided software and the ergonomic aspects fulfill the criteria for a necessary sterile workflow, achieved with the systems composition in two divided parts, one of them fully autoclavable. Motion, one factor for infections, takes place beneath the table, outside the surgical field. Other robotic systems are mainly located in the same level as the surgical field, reducing place for any

other supporting tool, such as microscope or neuronavigation and therefore include the danger of infection.

Conclusions The robotic system now available, based on a hexapod robot is able to perform a craniectomy in all requested regions including the stated locations of calvarial tumors and standard trepanations. Furthermore, it is suitable for the neurosurgical operation theatre since all sterile and not sterile components do not interfere with the current workflow. Future studies will allow modifications of the components in order to optimize the integration and the man-machine cooperation during neurosurgical procedures. Regarding the ergonomic aspects the handling of the arm and the fixation device of the drill have to be optimized. Currently a new robotic system with three additional degrees of freedom to hold the trepanation tool and to cover the different surface angles of the calvaria during craniotomy is ready to be integrated. This newly designed part, a completely autoclavable fixation device was constructed to optimize the handling of the surgical instruments.

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Bast P, Engelhardt M , Popovic A, Schmieder K, Radermacher K: CRANIO—Entwicklung eines Systems zur Computer- und Roboterunterstützten Kraniotmie. Biomed Tech 2002; 47 Ergänzungsband 1: 9-11 Nathoo N, Pesek T, Garnett GH: Robotics and neurosurgery. Surg Clin North Am 2003; 83:1339-50 Nathoo N, MC Cavusoglu, MA Vogelbaum, GH Barnett: In touch with robotics: neurosurgery for the future. Neurosurgery 2005; 56: 421-33 Nimsky C, Rachinger J, Iro H, Fahlbusch R: Adaptation of a hexapod-based robotic system for extended endoscope-assisted transsphenoidal skull base surgery. Min Invas Neurosurg 2004; 47: 41-6 Eggers G, Wirtz C, Korb W, Engel D, Schorr O, Kotrikova B, Raczkowsky J, Wörn H, Mühling, J, Hassfeld S, Marmulla R: Robot-Assisted Craniotomy. Minim Invas Neurosurg 2005; 48:154-8 Bast B, Engelhardt M, Lauer W, Schmieder K, Rohde V, Radermacher K.: Identification of Milling Parameters for Manual Cutting of Bicortical Bone Structures. Comput Aided Surg. 2003; 8(5):257-63. Engelhardt M, Bast P, Lauer W, Rohde V, Schmieder K, Radermacher K: Manual vs. Robotic milling parameters for development of a new robotic system in cranial surgery. In: Lemke HU, Vannier MW, Inamura K, Farmann AG, Doi K, Reiber JHC. Computer Assisted Radiology and Surgery. Elsevier; 2004. pp 533-538 Bast P, Engelhardt M, Lauer W, Schmieder K, Rohde V, Radermacher K: Approaches Towards Optimized Robot Kinematics for Surgical Applications. In: Paul Drews (eds), Proc. IEEE Mechatronics & Robotics 2004, 1436-40 Plinkert PK, Plinkert B, Hiller A, Stallkamp J: Einsatz eines Roboters an der lateralen Schädelbasis. Evaluation einer robotergesteuerten Mastoidektomie am anatomischen Präparat. HNO 2001; 49:514-22 Plinkert PK, Federspil PA, Plinkert B, Henrich D: Kraftbasierte lokale Navigation zur robotergestützten Implantatbettanlage in der lateralen Schädelbasis - eine experimentelle Studie. HNO 2002; 50:233-9 Wurm J, Bumm K, Steinhart H, Vogele M, Schaaf HG, Nimsky C, Bale R, Zenk J, Iro H: Development of an active robot system for multi-modal paranasal sinus surgery. HNO 2005; 53:446-54 Engelhardt M, Wehmoeller M, Eufinger H, Scholz M, Schmieder K: Ossäre Prozesse des Schädels - Anforderungsanalyse für Robotergestütztes Operieren. Biomed Tech 2002; 47 Ergänzungsband 1: 16-18 Engelhardt M, Bertlich N, Eufinger H, Harders A, Schmieder K: Indications, surgical management and pathological aspects of cranial and craniofacial bone resection. J Cranio Maxillofac Surg. 2002; 30 Suppl 1: 172

Table 1:

Distribution of the osseous lesions of the cranial vault (n=83)

Location

Number of lesions

%

Frontal

37

45

Parietal

23

28

Temporal

12

14

Occipital

6

7

Periorbital

5

6

Total

83

100

Gelöscht: ¶ ¶ ¶ ¶ ¶ ¶ ¶ ¶ Seitenumbruch

Figures

Fig. 1a,b:

A 47-year-old male patient with enlargement of the skull and localized pain. No neurological deficits were noted on admission. MRI revealed a large tumor with enlargement of bone and dural infiltration. The tumor was resected in Toto including dural repair with fascia lata and cranioplasty with a prefabricated titanium implant. The lesion was classified histological as a meningioma.

Figure 2 a,b: Standard-Trepanations transferred on plastic skulls to analyze the necessary range of motion of the robotic system

Figure 3 a, b: Combination of the patient in supine position in the OR in virtual reality and the umbrella shaped motion area of the robotic system. Best position of the robotic system beneath the table to optimal use of the robot’s working area.

Figure 4 a, b: Position of the robotic system beneath the table and the patients´ head, consisting of two components (sterile and unsterile), the upper c-shaped arm totally autoclavable

Figures 5 a - f: Workflow analysis of the robotic system in virtual surgical surrounding. Special emphasis was laid on sterility and navigation.