A Novel Instrument for Endoscopic Ear Surgery with a Steerable Flexible Tip: An Anatomical Validation Study

By June 7, 2019

Chayaopas, Nichtima1,2; Swarup, Arushri1,3; Andrysek, Jan3; James, Adrian1
1 Department of Otolaryngology – Head & Neck Surgery, Hospital for Sick Children, University of Toronto, Canada;
2 Khon Kaen Ear, Hearing and Balance Research Group, Department of Otorhinolaryngology, Khon Kaen University, Thailand;
3 Institute of Biomaterials & Bioengineering, University of Toronto, Toronto, Canada.

Endoscopes enhance visualisation of hidden middle ear structures1. Some such areas are beyond the reach of conventional surgical instruments. Following a needs analysis survey identifying a requirement for surgical instruments that reach more deeply into tympanic recesses2, a novel instrument with a steerable flexible tip (SFT) was developed.

– Study Design:
Observational study
– Setting:
Academic center
– Patients:
7 cases of cholesteatoma extending into the mastoid antrum treated with trans-canal totally endoscopic ear surgery (TEES) using an attico-antrostomy and canal wall reconstruction
– Intervention(s):
3D-printed temporal bone models were prepared from the CT-scan of each ear, adding fixed reference targets at potentially challenging anatomical sites for TEES (anterior epitympanum, sinus tympani, lateral semicircular canal and sino-dural angle). After a limited atticoantrostomy with bone curette, the ability of five surgical instruments (Rosen needle, Panetti suction dissectors for ear-drum, sinus-tympani and atticus and a prototype SFT instrument) to contact these targets using a 0°x2.7mm or 45°x3mm endoscope was assessed. Video-recordings of surgical access in the models were compared with surgical videos from the corresponding patients.

– Main Outcome Measure(s):
Proportion of the 28 anatomical targets (4-targets, 7-models) accurately palpated with each instrument.
– Results:
SFT reached and contacted all targets, excepting the sino-dural angle in five models, (23/28 =82%). Standard instruments reached fewer targets: atticus (57%), sinus-tympani (50%) and ear-drum (53%) dissectors, Rosen needle (46%). Model validity compared favorably with surgical videos.

The prototype SFT instrument increases a surgeon’s ability to reach structures that can be seen endoscopically but not reached with conventional instruments. Enhanced surgical access with less extensive bone removal can be anticipated so facilitating minimally invasive TEES.