Laser Facial Nerve Welding in a Rabbit Model - Temporal Bone ...Presentation Transcript
Resident Final Research Project Laser Facial Nerve Welding in a Rabbit Model Jason D. Bloom, M.D. University of Pennsylvania Department of Otorhinolaryngology: Head & Neck Surgery June 25 th , 2009 Faculty Mentors: Noam A. Cohen, M.D. & Stephen A. Goldstein, M.D. Special Thanks: Benjamin S. Bleier, M.D. Otorhinolaryngology: Head and Neck Surgery at PENN Excellence in Patient Care, Education and Research since 1870
Research Approval & Funding
This research project has been approved by both the U of Penn IACUC (Protocol # 802421) & Philadelphia VA ACORP
Awarded 2009-2010 AAO-HNSF / AAFPRS Leslie Bernstein Resident Research CORE Grant
Charles Gould (1957) - Introduces the term LASER ( L ight A mplification by S timulated E mission of R adiation)
In his doctoral thesis on energy levels of excited thallium
Sigel & Acevado (1962) - Reported thermal energy in tissue adhesion
Passing high frequency electric current through coapted vein edges to anastomose end-to-side porto-caval shunts in dogs (1)
Yahr & Strully (1966) – First description of laser tissue welding in blood vessel anastomosis (2)
Almquist et al. (1984) – Argon laser in peripheral nerve repair (3)
Fischer et al. (1985) – Published positive reports using the CO2 laser for rat nerve repair (4)
Allows for target specific laser energy absorption resulting in tissue bonds with greater tensile strength than wounds sealed with laser energy alone (5)
The use of biologic solders has been shown to provide an added benefit in the promotion of native wound healing mechanisms.
Contrast to the granulomatous inflammatory response seen with suture material
The lased solder coagulum provides a non-immunogenic scaffold (6)
Gradually absorbed during the normal wound healing process (7,8)
Biologic solders are now being combined with wavelength specific chromophores (9,10)
- Increased target specific energy absorption
- Decreased thermal energy leakage
- Objective basis of gauging adequacy of laser welding by providing a predictable color change
Laser welding of the rabbit facial nerve provides a method of creating an atraumatic, immediate and strong repair bond capable of allowing axonal regeneration across the injury site without damage to the nerve itself or the complications associated with suture neurorrhaphy.
Null Hypothesis: Laser nerve welding is not an effective way to perform neurorrhapy, as compared to suture nerve repair.
Time Table Day Procedure Data Point -Functional testing Data Point – EMG testing Data Point - Histology (H&E and Masson’s Trichrome Stain) 0 Rabbit Acquisition N/A N/A N/A 4 Rabbit Acclimation N/A N/A N/A 5 Survival Surgery/ Functional & EMG tests Laser Weld x 6, Suture x 6, Neg Control x 2 Laser Weld x 6, Suture x 6, Neg Control x 2 N/A 33 (wk 4) Functional & EMG tests/ Sac-Experimental Group #1 Laser Weld x 6, Suture x 6, Neg Control x 2 Laser Weld x 6, Suture x 6, Neg Control x 2 Laser Weld x 2, Suture x 2 61 (wk 8) Functional & EMG testing Laser Weld x 4, Suture x 4, Neg Control x 2 Laser Weld x 4, Suture x 4, Neg Control x 2 N/A 89 (wk 12) Functional & EMG testing Laser Weld x 4, Suture x 4, Neg Control x 2 Laser Weld x 4, Suture x 4, Neg Control x 2 N/A 117 (wk 16) Functional & EMG tests/ Sac-Experimental Group #2 Laser Weld x 4, Suture x 4, Neg Control x 2 Laser Weld x 4, Suture x 4, Neg Control x 2 Laser Weld x 4, Suture x 4, Neg Control x 2
Rabbit Survival Surgery
2 of the rabbit facial nerves (negative control group) = facial nerves transected with a 1cm piece of nerve excised w/o re-anastomosis
6 of the rabbits facial nerves = suture anastomosis w/ three 9-0 monofilament nylon sutures on an atraumatic taper needle
6 of the rabbit facial nerves = laser welded utilizing an 810nm diode laser and a “ribbon” of 42% albumin-based biologic solder coupled with an indocyanine green dye chromophore applied with a 27 G needle
14 New Zealand White Rabbits (3-4kg)
Housed at the Animal Research Facility (ARF) of the Philadelphia Veterans Affairs Medical Center (PVAMC)
Rabbit Facial Nerve Anatomy
Identifying the Facial Nerve
Hand-held nerve stimulator was used to identify the facial nerve and verify facial movement.
* Also, used to verify that the facial nerve was cut no longer innervating the face
Suture anastomosis w/ three 9-0 monofilament polypropylene (Prolene) sutures on an atraumatic taper needle
* Carl Zeiss OPMI CS-1 operating microscope
Biologic solder -
42% albumin solution Indocyanine green dye Hyaluronic acid sodium
* All treated w/ repeated 20G needle aspirations all completely resolved in 2wks
* No pain, distress, feeding issues, effect on wt. gain
Nicolet Viking IV EMG - subdermal electrodes
Nerve Conduction Study
- measuring CMAPs
- nerve latency
Functional / Clinical Testing
Positioning of the rabbits that allows standardized visualization and video recording of facial movements.
Gentle nasal & forehead taps performed in an attempt to elicit facial nerve motion.
Video tapes will then be analyzed to objectively grade facial nerve recovery by 2 different blinded observers.
Assess the rabbit's bilateral upper lip & whisker movement.
A scale of facial nerve movement from 0-3 will be used to record this functional testing with 0=no movement and 3=normal facial movement (16).
Normal Facial Nerve Function Left Facial Nerve Paralysis
6 nerve repairs from each experimental group were harvested and fixed in 10% buffered formalin for subsequent H&E staining
Analysis by our histopathologist (Eugene Einhorn, MD) for immune response to the solder, native wound healing progression, and extent of collateral nerve thermal injury.
The welds were also be prepared and stained with Masson’s Trichrome by our histopathologist, in order to view the axon counts and arrangement of nerve axons across the repair sites.
Nerve Laser Weld (H&E 4x) – 4wks * 16 week histological analysis = ongoing (1) Axon counts growing across the nerve repair site (2) Organization of the axons (3) Amount of neuroma formation (4) Amount of foreign body/granulomatous reaction
Operative Time * * P < 0.01 N=6 N=6
EMG Nerve Recovery
Clinical Nerve Recovery
Problems with the Study
Multiple buccal branches of the rabbit facial nerve distal to the site of the nerve injury & repair
Small number of rabbits in each group
Inability to circumferentially laser weld the nerve
Inconsistent EMG electrode placement in the facial musculature for each separate trial
No adequate method to measure synkinesis in a rabbit model
Testing EMG vs. ENoG
Discussion / Future Directions
Further areas of research with this laser welding technology:
Peripheral nerve repair
Microvascular arterial or venous anastomosis
Pharyngocutaneous fistula repair
Transoral robotic surgery models
Augmentation of the biologic solder with growth factors and antibiotics to further optimize wound healing
If these welds prove efficacious in larger trials, this technology would be ideally transitioned to clinical trials of facial nerve injury repair.
Clinical / Functional:
Improved facial nerve functional recovery on video analysis with the laser weld group
Improved facial nerve electrophysiological/EMG nerve recovery at all time points in the laser weld group, especially at early (1 month) & late (4 month) time points
H&E staining demonstrating negligible collateral thermal nerve or tissue damage
Biologic solder supporting the progression of the native wound healing response
Ongoing histopath: Utilizing Masson’s Trichrome stain (1) Axon counts growing across the nerve repair site (2) Organization of the axons (3) Amount of neuroma formation (4) Amount of foreign body/granulomatous reaction
No learning curve or operating microscope necessary with the laser weld group
Significantly reduced neurorrhaphy time with the laser weld group
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THANK YOU! Special Thanks To: - My Faculty Mentors - Dr. O’Malley - Dr. Cohen, Dr. Palmer, Dr. Bleier & The Penn Rhinology Lab - Perry DeRitis & VA ARF Staff - VA Neurology Service