Published on February 18, 2014
Opportunities and challenges in Laryngeal MicrosurgeryA user- based design of a wound closure device with potential to disrupt Dr Chui Chee Kong, NUS Dr David Lau Pang Cheng, SGH Stefan Choo A graduate seminar presented for the degree of M.Eng
Presentation Outline Introduction, Vocal fold pathology and intervention Study of surgical environment and tools for laryngeal microsurgery Introduction to various types of vocal fold interventions UCD and Task analysis of based approach and analysis to design of microclips Disruptive approach to scientific research. Experimental Task Analysis- Microclip strength vs Conventional sutures. What this implies for disruptive innovation.
1. Introduction, Vocal Fold Pathology and Intervention Vocal Folds in Work Contributors for vocal fold disorders Lifestyle Genetics Age Leisure Stress Food Dairy Histamines Spicy Smoking Occupation products Foods
1. Introduction- Vocal Cord Lesions Most lesions form on the superficial lamina propria (Reinke’s space). This results in mechanical hoarseness of voice and diminished voice Singers Nodules quality. These lesions include Does not vocal cord nodules, require surgical cysts and polyps. excision. A large vocal fold polyp Surgical excision is recommended!
Simulated Surgical Setup 2. Setup for Microlaryngeal surgery- Surgery on pigs Surgical Laryngoscope Microscope Framework to hold Layrngoscope Horizontal Vertice ≈ 30 mm Vertical Vertice ≈ 18 mm Average Tool diameter : 2mm
2. Setup for laryngeal microsurgery- Actual Patient Tools used for Layngeal Microsurgery Picture obtained from (http://www.muschealth.com/bin/l/a/operation.jpg)
2. Excision of a vocal fold lesionMicroflap technique Excision of foreign body from vocal fold (Picture from http://www.jdrntruhs.org/articles/2012/1/1/images/ JNTRUnivHealthSci_2012_1_1_7_94168_f7.jpg) Elevation of mucosal flap with L-alligator forceps
2. Existing methods of Surgical Intervention and evaluation Surgical Glue Surgical Glue Easy to apply, Collagen bundles observed Picture obtained from http://www.bjorl.org/conteudo/acervo/i mages/v78n1a08-fig04.jpg Sutures Primary Healing Sutures Primary Healing Best healing results, diffcult to apply Vocal fold scarring Picture obtained from http://www.internationalarchivesent. org/conteudo/imagesFORL/11-03-12fig05-ing.gif Picture obtained from http://www.jdrntruhs.org/viewimage.asp?img=JNTR UnivHealthSci_2012_1_1_7_94168_f8.jpg
4 Pillars of Research Material Research, Design and Optimization Research Objectives 1. User- Centric Approach: Bridging the gap between research and the users. Design of microclip Clinical Usability & Application Facilitation of wound healing 2. Characterizing a microclip that matches the intended period of implantation. 2.1 Animal Implantation 2.2 Experimental Task Analysis- Tensile Test on Clips 2.3 Degradation Experiments
Lessons from User Psychology Perspective BJ Fogg’s Model Of User’s Behavior Tacit 11 All 3 Factors have to Come together Simultaneously for the Surgeons to make a switch
Dichotomy between Designer and User’s Mental Model
Storyboarding Story-boarding: Use of illustrations to communicate ideas- Dr Lau
Story-boarding: Extension of initial conception of microclips Microclips that secure scaffold onto rhinolaryngeal wound sites via minimal access surgeries Microclips that secure scaffold construct onto cylindrical vessel
Design Considerations of Microclip C.f. “Method and material for minimal access wound closure using resorbable microclip and applicator” (Patent Application) Size & Geometry •High strength to weight ratio. •Ease of customizabili ty to small wounds across different tissues. •Mechanical stability and integrity over 2 wks. Degradability •Biocompati ble with minimum cytotoxicity. •Complete degradation within 2 weeks. •No adverse effects from clip migration. Material Consideration Stability of Insertion Modular nature •Biocompati bility •Good mechanical strength •Ease of processing and modification s •Easy and stable deployment. •No adverse mechanical effects such as tearing and injury on adjacent tissues •Standards •R&D can focus on on improving properties •Complemen tary features without changing bulk properties •Platformisati on
Proposed embodiment of microclips d e Range of thicknesses: 2.5mm- 3.5mm US Provisional Patent Application No. 61/495,035 filed 9th June 2011,
Microclip under Scanning Electron Microscope Clip before bending Clip before bending Closed clip
Insertion of Microclips- Pictures and Videos
Analysis for animal experiments. Task Analysis Subject: Dr David Lau, Dr Neville (Junior ENT consultant). Key variables recorded: ~12 - 20 seconds, fast for insertion process of suture. ~ 35 - 45 mins, tedious and slow for insertion of clips.
Post sacrifice observations
Histology results from initial microclip study Unpolished Magnesium clips Non excessive granulomaPCL Coated Clips
Results of In- Vivo Experiments of Magnesium clip on pigs at 2 week’s implantation. Surgeon’s Experience Observation on Pig’s Post Implantation Tissue Reaction Implant time. •Clip: 40secs. Requires 1 helper to position clip on applicator. •Suture: 12m40s/ 15s. Very tedious and strenuous process Suture may not be secured on pig #2 Pig # 1: No anomalies/ distress observed Pig #1: Minimal Host tissue inflammation (Only 1 clip remained at time of excision) Manipulation •C-Clips weighing 0.8mg More stable insertion •C-Clips weighing 0.65mg (thinner)Harder to insert, Preferred By Dr Lau Dr Lau would prefer a thinner embodiment of Mg clip, closer to that of a Suture Pig #2: Lower pitch of pig’s grunts detected. Absence of signs of distress. Pig #3: 2 clips were found after disccection. Pig #2: Dispersed granulation tissue observed throughout vocal fold. Signs of infection present. (All Clips remained at time of excision)
Post Implantation Results Extracted from “, A bioabsorbable microclip for laryngeal microsurgery: Design and evaluation”, J. Acta Biomaterialia, C.B. Chng, D.P. Lau, J.Q. Choo, C.K. Chui (2012)
Invention Vs Innovation Invention Vs Innovation Invention: A creation of a product/ knowhow for the first-time, usually as a result of scientific discovery or R&D Innovation: A product or process that makes a significant improvement in service or features to a product or existing market.
Disruptive Innovations New Dimension of Product Performance Progress Due to Innovation Sustaining , e.g. Innovations Customiza bility Low End Disruption New Market Creation EffortTime
Disruption as a strategy PerformanceHealing Sutures Increasing Ease of Use Reducecomplexities Glue First growth wave: Reduction in Surgical Effort- Time Complexities Second growth wave: Customization in treatment procedures, geometry, duration of wound healing Effort- Time
Disruptive InnovationsOvercoming Regulations Complexity of Diagnosis & Treatment Unpredict able & Iterative Time
Technology adoption CurveWound Closure Devices Glue Sutures Local Doctors in Singapore willing to experiment LocalRegional Hospitals, ok with CE Mark Standards High standing hospitals, Academic Hospitals, Private Hospitals , FDA Approved Standards Less trained surgeons
Experimental Task AnalysisMicroclips Vs Sutures
Materials and Methods Materials & Methods Magnesium Ribbon (Sigma Aldrich, 13103)- (3,m x 0.5mm)- Width x thickness. Specifications. Molar Mass, M Density, ρ Composition: Insol in HCL: 24.31g/mol 1.738 g/cm3 min 99.5% Mg max 0.05%, of which max 0.005% Cu max 0.02% Fe max 0.01% Pb Obtained from Material Safety Data Sheet, Mg- 13103, Sigma Aldrich A blood lead level of 10 μg/dL or above is a cause for concern - The US CDC, WHO Microclips were polished with 2000grit silicon carbide paper. Magnesium struts were then cut to 0.25mm thickness by Chng Boon and bent with a pair of surgical forceps.
Materials and Methods Materials - & Methods Mounting of Clips- - Clips were manually pieced into the silicone rubber sheets with surgical cusps forceps. Singular Clips- Nylon threads with a simple knot was tied to the opposite curved ends of the clip. The free ends of the threads were then looped around
Materials and Methods - Materials & Methods Mounting of Clips- - Clips were manually pieced into the silicone rubber sheets with surgical cusps forceps. Singular Clips- Nylon threads with a simple knot was tied to the opposite curved ends of the clip. The free ends of the threads were then looped around the silicone sheets. These sheets were clamped onto the respective ends of the tensile tester and
Materials and Methods Tensile - Test Procedures Tensile tester was set in place at a strain rate of 1mm/sec. Readings were taken until load drops of 40% of it’s maximum value. Readings with slippage was subsequently discarded.
2500 Plot of Single Clip Securing Thin Silicone Sheets Load (mN) 2000 1500 Series1 1000 Poly. (Series1) 500 0 0 0.5 1 1.5 2 2.5 Extension (mm) 3 3.5 4 4.5 Observations: 1. Segment A- 0 to 1.5mm displacement- Logarithmic increase in Load Extension, possibly due to combined bending and elongation (Unrolling). 2. Segment B- 1.5mm to 2.5mm- Alignment 3. Segment C- 2.5 mm-3.8mm- Simple Elongation 4. Segment D- 3.8mm- 4mm- Slip
Analysis of Pull off Force VS Extension for Clips embedded in thick silicone rubber (1.5mm) 4000 3500 Load (mN) 3000 2500 2000 1500 1000 500 0 0 0.5 1 1.5 Extension (mm) 2 2.5 3 Observations: Clips on Thick Silicone Sheet … 1. Segment A- 0 to 1.5mm displacement- Logarithmic increase in Load Extension, possibly due to combined bending and elongation (Unrolling). 2. Segment B- 1.5mm to 2.5mm- Alignment 3. Segment C- 2.5 mm-3.8mm- Simple Elongation 4. Segment D- 3.8mm- 4mm- Slip 3.5
Plot of Single Clip Securing Silicone Sheets of different thicknesses 4000 3500 Load (mN) 3000 2500 2000 Clips (Thin) (n=5) 1500 Clips (Thick) (n=3) 1000 500 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Extension (mm) 1. Observations: Holding strength of clips is largely determined by thickness of silicone sheet. • A 3.8 times increase in sheet thickness larger sustained pull off force off approximately 3N, twice that of the thinner sheets. 2. Thicker silicone sheet Reduced clip displacement before slip.
3500 Plot of Single Clip Vs Triple Clips in Securing Silicone Sheets 3000 Load (mN) 2500 ~50 0m N 2000 Single Clips 1500 Triple Clips 1000 500 0 0 1 2 3 4 5 *Triple Clips (n=3) Extension (mm) Observations: 1. Triple clips reduces variance In load displacement. 6 2. Triple clips provide a 500mN increase (28%) of maximum holding strength, accompanied by a 24% increase in maximum extension before clip detachment.
Plot of Load- Extension Graph: Free-Tensile Test of Fully Closed Clips with Strings Attached 3500.00 Combined bending and elongation 3000.00 Load (mN) 2500.00 2000.00 Primary elongation 1500.00 1000.00 500.00 0.00 0 1 2 3 4 5 Extension mm 6 7 8 9
Plot of force- extension of a suture tied across Thin Silicone Sheet (mN) 6000 5000 Load (mN) 4000 3000 2000 1000 0 0 2 4 6 Force (mN) (Sample size, n=4) 8 10 12 14 Poly. (Force (mN) (Sample size, n=4)) Extension (mm) 16 Observations: Suture strength >>> Strength of silicone sheet. Silicone sheet tore apart at 14.75mm. Large strains deformation of silicone sheet was similar to that of an indentation test. Silicone sheet might not be a good way to test the holding force of suture at large strain. 18
Comparison of Load- Extension Characteristics of Clip Vs Suture at Low Extensions across two thin silicone sheets (8mm) 2500 Load (mN) 2000 1500 1000 500 0 0 0.5 1 1.5 2 Extension (mm) 2.5 3 Clip (n=5) 3.5 4 4.5
Observations from Experimental Task AnalysisMicroclips Vs Sutures A single clip provides superior holding strength to resist low levels of strain as compared to a suture. is suitable to hold the edges of the vocal fold in place, since lateral extensions of the vocal fold edge <2mm. We recommend that the mechanical properties of the clip be further investigated at low strains, upon in vivo degradation experiments timed at 1day, 3 days, 7 days, 14 days and 1 month and examined.
Potential for disruptive impact Microclips R&D has the potential to serve as alternatives for wound litigation for wounds subjected to minimal displacements. Microclips can be customized to fit surgical instruments, unlike sutures. Mircoclips can be quickly deployed for use by surgeons versus sutures.
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