Medical Student Research Fellowship for Summer 2008

Mentor: Michel Saint-Cyr MD
Department: Plastic Surgery
Room number: WA4.230
Mail Code: 9132
Phone number: 214-645-3115
E-mail: michel.saint-cyr@utsouthwestern.edu

Project # 1

Project title: 3D and 4D vascular anatomy and perfusion of perforator flaps

Project Type

Basic Research (cadaver dissections)

Brief Description of Project:

Introduction:

Two-dimensional lead oxide radiography is the standard for investigation of the vascular anatomy of surgical flaps. The angiosome, however, is a three-dimensional concept, and the perforator flap era demands a detailed understanding of the anatomy and physiology of the vasculature superficial to the deep fascia. The understanding of the vascular anatomy and physiology of perforator flaps is limited conceptually by imaging in two-dimensions. Static three-dimensional CT angiography enables perforator flap anatomy to be evaluated in three dimensions without the conceptual constraints imposed by traditional two-dimensional radiography. Four-dimensional CT angiography allows dynamic imaging of the vascular filling to be visualized. This study will investigate the use of 3D and 4D imaging of all major perforator flaps pertaining to the head and neck, trunk, upper and lower extremities in the cadaver human body in order to determine their vascular territory, vascular axiality, and potential for new flap designs. Results from this study will also improve our understanding of how perforator flaps and the skin are vascularized and will form the basis for the perforasome theory of skin vascularity.

Methodology:

All cadavers will be acquired through the Willed Body Program at The University of Texas Southwestern Medical Center, in Dallas, Texas. Each perforator flap will be dissected based on the largest perforator originating from the main vascular pedicle, and the perforator will be cannulated using a 24-gauge butterfly catheter (0.7mm diameter; BD Insyte; Becton Dickinson S.A., Madrid, Spain). The flaps will be placed in a jig to present the flap axially with respect to the CT scanner, and on a GE Lightspeed 16 slice scanner (General Electric, Milwaukee, WI) with the scanner set to perform helical scans. Omnipaque 300 (iohexol; 300 mg/ml; Amersham, Princeton, NJ) will be placed in a Harvard precision pump (PHD 2000, Harvard Apparatus, Inc.) and will be injected injected at an optimal filling rate. Irrigation with warmed saline will be used to allow washout of the contrast medium an enable the flaps to be rescanned following thinning. To obtain a static image we will use a barium sulphate/ gelatin mixture for vascular injection, which provides images of high contrast resolution.

Results obtained so far

1. There are marked regional differences in the vascular perfusion patterns of perforator flaps.
2. It is possible to identify morphologically distinct patterns perforator complexes. The perfusion of each layer of the flap relative to the perforator has been analysed using contrast density analysis software that we have written and has confirmed the presence of the three complex types.
3. Retrograde blood flow from the subdermal plexus, which has previously been regarded as a filling artifact, may be the dominant mechanism for perfusion of the suprafascial plexus, although micro-CT will be necessary to evaluate the detailed changes at the level of the subdermal plexus.
4. Adjacent angiotomes are linked by large diameter anastomotic channels, which in turn supply branches that feed the subdermal plexus between adjacent angiotomes, a phenomenon that has not been described previously.

Project # 2

Project title: Free muscle flaps versus free fasciocutaneous flaps in reconstruction of Gustilo 3B lower extremity injuries. Clinical results and indications.

Human subjects IRB approved project numbe): 072006-073

Project Type

(patient-based research

Brief Description of Project:

Devastating lower extremities injuries involving the middle and lower thirds of the leg have been traditionally been treated with free muscle flaps. The use of free fasciocutaneous flaps in lower extremity reconstruction has been recently introduced and is gaining wider acceptance amongst reconstructive surgeons. Advantages and disadvantages of both flap types exist and both have very specific indications. A paucity of information is available concerning the indications and contra-indications for use of both flap types. This study will consist of a retrospective chart analysis of all lower extremity injuries treated with either fasciocutaneous or muscle free flaps to obtain stable coverage and wound coverage. This study will examine the indications, contra-indications, complications, and results of using either muscle or fasciocutaneous free flaps in reconstruction of the lower limb following trauma. Predictors of outcome will also be determined in both groups and clear guidelines will be established to improve outcome and lower the complication rates associated with treating these devastating injuries. Student's T test will be used for statistical analysis.

Previous Research Activities or Publications with Medical Students:

I have 6 years experience with teaching medical students prior to recent appointment at UTSW. I supervised 1 medical student for the summer of 2006 on a project looking at flexor tendon repair using barb sutures which was presented as a poster at the medical student summer research symposium. I also supervised 2 medical students last summer for the projects listed below. Two of these projects were presented as posters at the annual medical student summer research symposium. All of these projects are in the final draft status and will be submitted for publication shortly.

Use of the muscle sparing latissimus dorsi flap in immediate and delayed breast reconstruction: anatomical and clinical study (IRB: 072006-072)

Outcomes of Implant-Based Breast Reconstruction using Subserratus and Subpectoral Fascia (IRB: 042007-017)

Alloderm vs. DermaMatrix in Immediate Expander- Based Breast Reconstruction: A Comparative Analysis

Use of pedicled subpectoral fascia flap for expander coverage in post-mastectomy breast reconstruction - a novel technique