A Novel 3D Printed Sensorized Surgical Instrument to Characterize Pituitary Adenoma: Development and Initial Validation

The pituitary adenoma (PA) is a tumor that grows in the sellar region, near the pituitary gland. PAs are usually removed surgically by expert neurosurgeons and otolaryngologists through the nasal cavities, with the so-called endoscopic transsphenoidal approach. One of the most challenging complications is that the consistency of PAs remains unpredictable until the surgeon approaches it during the surgery, thus meaning that surgeons must choose intraoperatively the most suitable technique to resect PAs. In this work is presented a novel and improved version of the solutions reported in the literature. The instruments consist of a body and a highly deformable tip fabricated through additive manufacturing technologies and a magnetoresistive sensor which measures the variation of the magnetic field when the tip is compressed due to the contact with the adenoma and then this system is capable of discerning soft tissues consistency. Two different tips with four arms were assessed, one with a 0.45 mm thickness and the other with a 0.75 mm thickness to find a trade-off between the stability of the tip and its deformability. Compression tests with samples of different Shore 00 hardness were conducted, to explore how the probe behaves with material with different hardness. Tests were conducted with specimens made of boiled egg white, which according to literature and expert surgeons, its consistency is similar to PAs. A preliminary value of hardness of 16.08 ± 2.02 for 0.45 mm tips and 16.17 ± 4.37 for 0.75 mm tips were measured for the boiled egg white. According to results, the 0.45 mm tips are more suitable for the application of the sensorized probe due to the lower uncertainties. In addition, force data measured during tests with the egg white specimen, are in line with data found in the literature about the force exerted during neurosurgical approaches. These results can be considered a preliminary analysis of how the probe would behave with a real PA.