Week 7: Fibular Flaps and Farewells

Biomedical Engineering applications in the OR

Tuesday's case was an excellent example of biomedical technologies used during surgeries including 3D printed bone guides, optical systems, and Doppler probes.  The patent had oral cancer with a tumor that invaded into the jaw which requited a partial mandibular resection. The plastics team used the patients fibula to create a new jaw and repair the oral defect after the resection.   Virtual surgical planning was used to model patient specific anatomy from CT scans of the fibular and facial features. The company 3D systems uses the patient specific data to create templates for cutting the fibula and mandible and to create the metal plates that hold the new mandible together. The surgical planning models the segments to cut the fibula into and it models them fit back together in the desired jaw shape with the metal brace. These models and surgical plan come with guides and templates so the bone can be cut in the right angle in the right place with aligned drill holes. To summarize: the mandible is cut at the predetermined modeled spots and removed, the Fibula is cut at specific spots into pieces that will fit together in the desired geometry to take the shape of the jaw, then the hardware designed to hold together the fibula pieces is installed to fix the new jaw to the surrounding bone.

Fibular isolation: The fibula needs to be removed and cut into 3 segments and then bent into the shape and contour of the jaw while maintaining contact between the segments. Incisions were made to isolate the fibula and its periostuim from the surrounding muscle while preserving the blood supply. I personally was surprised by the appearance of the bone surrounded by the periosteum and the thickness of the periosteum with all its vasculature.  The fibula was cut at both ends to separate out the middle section of bone. From the ends the periostum was peeled back  to reveal the bone but the middle section that would be used for the reconstruction was left untouched. This was an important distinction because for the bone to be healthy and heal in its new anatomic location, there needs to be a blood supply to each segment left intact. The proximal and distal ends of the fibula that interface with the knee and ankle were left in place with the cut ends left loose as if the middle section was still there.

Tumor and Jaw resection: The head and neck team removed the tumor and sent it off to pathology to check the margins. The pathology results indicated more needed to be removed so they excised more. The mandible cutting template was used to cut the bone and removed the section of jaw along with attached soft tissue.

Fibular reconstruction: The cut fibular pieces were placed in the metal plate guide and screwed into place. This piece with the attached vasculature was then it into the jaw and screwed into the remaining sections of the mandible.

Vascular microsurgery: To restore blood flow and increase the chance that the fibular flap would take, the vasculature of the periosteum was connected to the vasculature in the neck by hand sewn techniques of the use of a vascular coupling device. All of this work is done under a surgical microscope because the vessels can be 2mm in diameter. In brief, the vascular coupler can be fed two ends of a vessel and then it closes bringing the ends together and uses a junction to create a seal. The blood flow is critical to the patient outcome and the survival of the flap so it must be monitored every hour for the first day and then at longer time intervals for days after. To monitor the flow implantable doppler probes are used. They are made of a biodegradable cuff attached to the probe and the wire which exits through an incision. This is placed around the vessel during the surgery and allows for flow monitoring. If the flow stops more surgical intervention would be needed to salvage the flap. 

Resident Lecture

Monday morning I went to the resident lecture about skin cancer. Plastic surgeons see an abundance of skin and they commonly remove cancerous legions. This week's lecture was about non-melanoma skin cancer. Skin cancer is diagnosed more than any all other cancers combined and is an economic burden of over $8.1 billion. The most common kind is basal cell carcinoma followed by squamous cell carcinoma. Causes of skin cancer include chronic wounds, immunosupression, HPV, Inherited disease, melanogenesis, UV Radiation with UVA and UVB rays.  Different skin types confer different risks, a ranking of skin types is Fitzpatrick skin types that ranges from types I-VI and is how likely you are to burn. It was interesting to learn about cancer treatments for these diseases and the role plastic surgeons play.

Project update

I was able to isolate, freeze, and send 3 cell populations to my lab back in Ithaca. I stained and imaged samples of lean and obese tissue to use for an analysis of differences in the native tissue due to BMI. Preliminary results of my second decell method show promise in the technique even though there were some issue related to tissue processing and fixation that I learned from to make future iterations better.  

A big thanks to Dr. Spector for being a great mentor and giving me the opportunity to shadow in both the clinic and OR. I learned so much this summer and gained a much better appreciation of clinical practices, biomaterials, and tissue engineering products currently used. I had a great time working in the Laboratory of Bioregenerative Medicine and Surgery with helpful, fun, and smart labmates. I'm looking forward to continued collaboration with them in the future! 

Figure 1: H&E staining of breast adipose tissue