Analysis of forces during robot-assisted and manual manipulations of mobile and fixed footplate in temporal bone specimens.

PURPOSE: To evaluate the forces involved in different manipulations, manual or robot-assisted, applied to the ossicular chain, on normal temporal bones and on an anatomical model of otosclerosis. METHODS: Thirteen cadaveric temporal bones, with mobile footplates or with footplates that were fixed using hydroxyapatite cement, were manipulated, manually or using a robotic arm (RobOtol®). "Short contact" of a mobile footplate was the weakest interaction on the incus. "Long contact" was the same manipulation held for 10 s. "Mobilization" was the smallest visualized movement of the mobile footplate, or the movement necessary to regain mobility of the fixed footplate. A six-axis force sensor (Nano17, ATI) measured the maximal peak of forces, summation of forces applied, and yank. RESULTS: Maximal forces during short (~4 mN) and long contact (~15 mN) were similar for manual and robot-assisted manipulations. For manual manipulation, yank measured during long contact was twice as high compared to robot-assisted manipulation: 6 ± 2.4 (n = 5) and 3 ± 1.3 mN/s (n = 5), respectively (mean ± SD, p < 0.02). For mobilization of the mobile footplate, maximal forces during mobilization were similar during manual and robot-assisted manipulations, respectively: 12 ± 2.5 (n = 6) and 19 ± 7.6 mN (n = 7). Compared with mobilization of a mobile footplate, mobilization of a fixed footplate required ~ 60 and ~ 27 times higher maximal forces for manual and robot-assisted manipulations, respectively: 724 ± 366.4 and 507 ± 283.2 mN. Yank was twice as high during manual manipulation compared to robot-assisted manipulation (p < 0.05). CONCLUSION: Robot-assisted manipulation of the ossicular chain was reliable. Our anatomical model of otosclerosis was successfully developed requiring higher forces for stapes mobilization.

Robot-based assistance in middle ear surgery and cochlear implantation: first clinical report.

PURPOSE: Middle ear surgery may benefit from robot-based assistance to hold micro-instruments or an endoscope. However, the surgical gesture performed by one hand may perturb surgeons accustomed to two-handed surgery. A robot-based holder may combine the benefits from endoscopic exposure and a two-handed technique. Furthermore, tremor suppression and accurate tool control might help the surgeon during critical surgical steps. The goal of this work was to study the safety of an otological robot-based assistant under clinical conditions in a limited series of patients. METHODS: The RobOtol system has been used as an endoscope or a micro instrument holder for this series. Eleven cases were operated on with the robot as an endoscope holder for chronic otitis. Twenty-one cases were operated on with the robot as a micro-instrument holder for otosclerosis (9 cases), transtympanic tube placement (2 cases), or cochlear implantation (10 cases). RESULTS: No complications related to the robot manipulation occurred during surgery nor in postoperative. In the chronic otitis group, all perforations were sealed and 3-month postoperative pure-tone average air-bone gap (PTA ABG) was 15 ± 2.6 dB. In the otosclerosis group, 1-month post-op PTA ABG was 10 ± 1 dB. For cochlear implantation cases, a scala tympani insertion, a vestibular scala translocation occurred and a full scala vestibuli insertion was observed in 7, 2 and 1 case, respectively. CONCLUSION: The RobOtol system has reached the clinical stage. It could be used safely and with accurate control as an endoscope holder or a micro instrument holder in 32 cases.

Navigation-guided transmodiolar approach for auditory nerve implantation via the middle ear in humans.

The aim of this study was to assess the surgical feasibility of a transmodiolar approach via the middle ear cavity for an auditory nerve implantation in humans. In the first part of the study, 6 adult human temporal bones underwent a navigator-guided transmodiolar implantation via the middle ear space after a radical mastoidectomy. In the second part, 122 temporal bone CT scans were analyzed for anatomical parameters relevant to this approach. The nerve implantation was feasible in all temporal bones in laboratory conditions, with a mean target registration error of 0.065 ± 0.0583 mm (n = 6). Evaluation of anatomical parameters on CT scans also supported the feasibility. There was a significant interindividual variation of the modiolar axis and the entry point in relation to visible anatomical landmarks, highlighting the necessity for surgical preplanning.

Minimally invasive computer-assisted approach for cochlear implantation: a human temporal bone study.

Computer-assisted navigation systems can now potentially guide the surgeon to the cochlea with a trajectory avoiding the facial nerve through a keyhole approach. Five temporal bone specimens, with 4 titanium screws placed in the mastoid cortex, were studied. Preoperative computed tomographic scan images were loaded on an electromagnetic computer-assisted surgery (CAS) system (Digipointeur, Collin, Bagneux, France). A drill was connected to the CAS to monitor its progression continuously. A conical approach passing through the facial recess and ending in the scala tympani was performed. A 0.5-mm wire was inserted into the cochlea. The keyhole approach was technically feasible in all cases. No facial nerve injury was observed on imaging and dissection control. The wire was positioned in the scala tympani and the position accuracy of the CAS was <0.76 mm on the target in all cases. The CAS system with fiducial markers yielded sufficient precision to allow a minimally invasive approach to the cochlea.

Use of bone anchoring device in electromagnetic computer-assisted navigation in lateral skull base surgery.

CONCLUSION: The use of the bone anchoring device associated with a fiducial marker, both fixed close to the operating field, improves the reproducibility and effectiveness of the computer-assisted navigation in lateral skull base surgery. OBJECTIVES: Computer-assisted navigation in lateral skull base surgery using the electromagnetic system Digipointeur(®) needs an external fiducial marker (titanium screw) close to the operating field to increase position accuracy (PA) to about 1 mm. Displacement of the emitter placed in the mouth (Buccostat(®)) induces a drift of the system, leading to at least 20% of unsuccessful procedures. The aim of this study was to evaluate the PA, stability, and reproducibility of computer-assisted navigation in lateral skull base surgery using a bone anchoring device to provide a fixed registration system near the operating field. METHODS: Forty patients undergoing a lateral skull base procedure with the Digipointeur(®) system performed with both the titanium screw and bone anchoring device were included in this prospective study. They were divided in two groups. In the first one (n = 9), the PA was measured before and after screw registration for five intratemporal landmarks, during a translabyrinthine approach. In the second group (n = 31), all lateral skull base procedures were included and the PA was evaluated visually by the surgeon on different landmarks of the approaches as well as the stability of the system. RESULTS: In the first group, the PA was 7.08 ± 0.59 mm and 0.77 ± 0.17 mm (mean ± SEM, p < 0.0001) before and after screw registration, respectively. In the second group, the PA was considered as accurate by the surgeon in all cases and no drift of the system was observed. Computer-assisted surgery was never abandoned due to increased stability of the bone-anchored emitter.

Use of anatomic or invasive markers in association with skin surface registration in image-guided surgery of the temporal bone.

CONCLUSION: The use of an invasive marker in the ipsilateral temporal bone with mid-facial skin contouring for registration improved the position accuracy (PA) to levels required for otological and neuro-otological procedures. OBJECTIVE: The aim of this study was to compare the PA after skin contouring with the combination of anatomic landmarks or a local invasive marker and skin surface registration for intratemporal computer-assisted navigation. PATIENTS AND METHODS: Thirty-three patients undergoing a lateral skull base procedure with the Digipointeur system (Collin, Bagneux, France) based on CT scan were included in this study. Registration was obtained by a mid-facial skin contouring. In the first protocol (n=8), PA was evaluated and the position corrected for three intratemporal landmarks before evaluation of the target (round window). In a second protocol (n=25), a titanium screw was placed in the ipsilateral mastoid region before imaging. PA was measured before and after screw registration for five intratemporal landmarks. RESULTS: In the first protocol, PA did not improve after the registration of the landmarks, and PA of the target was evaluated as 4.9+/-0.64 mm. In the second protocol, PA was reduced after screw registration for all landmarks with a mean PA ranging from 0 to 2.3 mm.