Surgical simulators are designed to improve operative skills and patient safety. Transcanal Endoscopic Ear Surgery (TEES) is a relatively new surgical approach with a slow learning curve due to one-handed dissection. A reusable and customizable 3-dimensional (3D)-printed endoscopic ear surgery simulator may facilitate the development of surgical skills with high fidelity and low cost. Herein, we aim to design, fabricate, and test a low-cost and reusable 3D-printed TEES simulator.
The TEES simulator was designed in computer-aided design (CAD) software using anatomic measurements taken from anthropometric studies. Cross sections from external auditory canal samples were traced as vectors and serially combined into a mesh construct. A modified tympanic cavity with a modular testing platform for simulator tasks was incorporated. Components were fabricated using calcium sulfate hemihydrate powder and multiple colored infiltrants via a commercial inkjet 3D-printing service.
All components of a left-sided ear were printed to scale. Six right-handed trainees completed three trials each. Mean trial time (n = 3) ranged from 23.03 to 62.77 s using the dominant hand for all dissection. Statistically significant differences between first and last completion time with the dominant hand (p < 0.05) and average completion time for junior and senior residents (p < 0.05) suggest construct validity.
A 3D-printed simulator is feasible for TEES simulation. Otolaryngology training programs with access to a 3D printer may readily fabricate a TEES simulator, resulting in inexpensive yet high-fidelity surgical simulation.
The tympanic membrane (TM) is an exquisite structure that captures and transmits sound from the environment to the ossicular chain of the middle ear. The creation of TM grafts by multi-material three-dimensional (3D) printing may overcome limitations of current graft materials, e.g. temporalis muscle fascia, used for surgical reconstruction of the TM. TM graft scaffolds with either 8 or 16 circumferential and radial filament arrangements were fabricated by 3D printing of polydimethylsiloxane (PDMS), flex-polyactic acid (PLA) and polycaprolactone (PCL) materials followed by uniform infilling with a fibrin-collagen composite hydrogel. Digital opto-electronic holography (DOEH) and laser Doppler vibrometry (LDV) were used to measure acoustic properties including surface motions and velocity of TM grafts in response to sound. Mechanical properties were determined using dynamic mechanical analysis (DMA). Results were compared to fresh cadaveric human TMs and cadaveric temporalis fascia. Similar to the human TM, TM grafts exhibit simple surface motion patterns at lower frequencies (400 Hz), with a limited number of displacement maxima. At higher frequencies (>1000 Hz), their displacement patterns are highly organized with multiple areas of maximal displacement separated by regions of minimal displacement. By contrast, temporalis fascia exhibited asymmetric and less regular holographic patterns. Velocity across frequency sweeps (0.2-10 kHz) measured by LDV demonstrated consistent results for 3D printed grafts, while velocity for human fascia varied greatly between specimens. TM composite grafts of different scaffold print materials and varied filament count (8 or 16) displayed minimal, but measurable differences in DOEH and LDV at tested frequencies. TM graft mechanical load increased with higher filament count and is resilient over time, which differs from temporalis fascia, which loses over 70% of its load bearing properties during mechanical testing. This study demonstrates the design, fabrication and preliminary in vitro acoustic and mechanical evaluation of 3D printed TM grafts. Data illustrate the feasibility of creating TM grafts with acoustic properties that reflect sound induced motion patterns of the human TM; furthermore, 3D printed grafts have mechanical properties that demonstrate increased resistance to deformation compared to temporalis fascia.
Arterial stiffness is an independent predictor of cardiovascular outcomes in hypertensive patients including myocardial infarction, fatal stroke, cerebral micro-bleeds which predicts cerebral hemorrhage in hypertensive patients, as well as progression to hypertension in non-hypertensive subjects. The association between arterial stiffness and various cardiovascular outcomes (coronary heart disease, stroke) remains after adjusting for age, sex, blood pressure, body mass index and other known predictors of cardiovascular disease, suggesting that arterial stiffness, measured via carotid-femoral pulse wave velocity, has a better predictive value than each of these factors. Recent evidence shows that arterial stiffening precedes the onset of high blood pressure; however their molecular genetic relationship (s) and sex-specific determinants remain uncertain. We investigated whether distinct or shared genetic determinants might underlie susceptibility to arterial stiffening in male and female Dahl salt-sensitive rats. Thus, we performed a genome-wide scan for quantitative trait loci (QTLs) affecting arterial stiffness in six-week old F2 (Dahl S x R)-intercross male and female rats characterized for abdominal aortic pulse wave velocity and aortic strain by high-resolution ultrasonography.
We detected five highly significant QTLs affecting aortic stiffness: two interacting QTLs (AS-m1 on chromosome 4 and AS-m2 on chromosome16, LOD 8.8) in males and two distinct interacting QTLs (AS-f1 on chromosome 9 and AS-f2 on chromosome11, LOD 8.9) in females affecting pulse wave velocity. One QTL (AS-1 on chromosome 3, LOD 4.3) was found to influence aortic strain in a sex-independent manner. None of these arterial stiffness QTLs co-localized with previously reported blood pressure QTLs detected in equivalent genetic intercrosses.
These data reveal sex-specific genetic determinants for aortic pulse wave velocity and suggest distinct polygenic susceptibility for arterial stiffness and salt-sensitive hypertension in Dahl rats based upon reported blood pressure QTLs in equivalent (Dahl S x R)-intercrosses.