Friday, August 05, 2005

Jeff Ballyns 4th Week

Monday: I reported to the OR at HSS at 8:30 to shadow Dr. Bostrom. While with Dr. Bostrom I was able to observe 2 total knee replacements, 2 total hip replacements and finally a total knee revision.

For those not familiar with the logistics involved in a total hip operation the basic procedures include an incision on the lateral side of the hip where the femur is dislocated so that the femoral head can be removed. The acetabulum, the surface that the femoral head articulates on, is then reamed to enlarge the area for prosthesis insertion. Finally, the prosthetic femoral head is inserted and the incision closed. The images below give a better visual representation of what would be seen on the operation table.

These images provided by Bringham and Women’s Hospital and The Legal and Legislative Resource Center

Below can be seen what some typical prosthetic hip implants look like consisting of a femoral head and an acetabular cup along with an articulating surface usually made out of polyethalyn.

Image provided by Wright

Below can be seen how these implants are viewed on an x-ray.

Image provided by Mar Vista Animal Medical Center

The total hip replacements were much different from the first surgery I had watched at HSS which was with Dr. Padget. Dr. Padget allowed Tunde, Satish, and I to observe a total hip of a dwarf woman which necessitated the use of a custom implant due to her small size. This procedure took about 2 hours because of the delicacy required when installing the artificial femoral head. Dr. Bostroms patients where of normal stature and each operation took less than an hour. Standard sized brushes were used to clear out the cortical bone from the femur and the implant was inserted with ease since a generic implant could be used making it a routine procedure.

Tunde has already described what is involved in a total knee replacement so I will not repeat what she has already presented. What I did appreciate this time around when viewing the operations was the presence of a camera that allowed me to get a birds eye view of what Dr. Bostrom was doing. I could see just exactly how each tool was attached to the knee to provide aid in making precise cuts when shaving off the femoral condyles and the tibial plateu. My final experience on Monday Dr. Bostrom allowed me to scrub in and view a total knee revision up close. Typically knee revisions are done in the case of infection, trauma, or loosening. In this case it was simply loosening of the implant due to Osteolysis. Osteolysis is bone resorption around the implant such that the implant becomes unstable and must be revised. An example can be seen below as seen by the clearing out of bone in the medial femoral condyle.

Images provided by Duke Othopeadics

Scrubbing in was quite an experience seeing just how careful one has to be once washing your hands and putting the head gear on along with the smock and gloves. Seeing the operation up close is quite a different sensation with all the new smells and seeing all the debris that is removed when changing the implant. The final implant that the patient was left with was an off center hinge joint.

One interesting things that had happened during 2 of the operations was that the patients woke up during the procedure. This typically happens to people who abuse alcohol or have high drug use. What I found so interesting was that they felt no pain in their legs even though the surgeon was using a saw and cutting bone. The reason they felt no pain in their legs was because a neurostimulator was being used. The stimulator sends electrical signals to the great sciatic nerve and its two branches the tibial nerve and the common peroneal nerve preventing any sensations of pain being delivered to the patient during the surgery.

Tuesday: Chemical Lab safety meeting for HSS

Wednesday: Dr. Potters MRI physics lecture. We discussed fat suppression techniques, truncation artifact, wrap around, and gradient echo imaging. Fat has a high signal on magnetic resonance images (MRI). This high signal, easily recognized on MRI, may be useful to characterize a lesion. However, small amounts of lipids are more difficult to detect on conventional MRI. In addition, the high signal due to fat may be responsible for artifacts such as ghosting and chemical shift. Lastly, a contrast enhancing tumor may be hidden by the surrounding fat. To improve the image fat can be suppressed by canceling out the RF peek that is representative of fat.

Truncation artifact is when part of one image crosses over to the next and it has uneven overlap. Wrap around artifact or aliasing is when tissues outside the field of view do not get properly phase encoded relative to their actual position. This excited tissue gives up signal during readout but as it has not been correctly phase encoded appears in a position other than its actual location. Anatomy outside the field of view "wraps" into the opposite side of the image. This can be corrected by scanning with a larger field of view, applying presaturation pulses to the undesired tissue, or by correctly phase encoding the extraneous tissue then discarding that information. The image below represents wrap around artifact and was provided by UBC .

Thursday: Tunde and I attended the Sports Medicine Conference. The topic was Ligaments of the Knee (conference center) viewed on MRI and was held by Dr. Potter. We then went to the Soft Tissue Lab Meeting where they discussed various articles that were recently published. Finally, we attended the Biomechanics Lab Meeting where one of the medical interns, Owen, presented his summer research project. The project consisted of analyzing the glenoids retrieved from people who had total shoulder replacements. Finally Dr. Myers gave her lecture on Statistics.

Friday: Tunde and I met with Lionel B. Ivashkiv, MD to tour his lab and discuss the summer immersion program. His laboratory studies a major signal transduction pathway utilized by many cytokines. The laboratory is characterizing molecular mechanisms that regulate signaling by the Jak-STAT pathway and attempting to develop the idea that modulation of cytokine signaling during inflammation is an important determinant of the balance of cytokine action. We are studying the mechanisms and the impact of modulation of cytokine signaling on cell function and gene expression, and on the severity of inflammation and related tissue damage. One example, is systemic lupus erythematosus (SLE), IL-10 signaling is reprogrammed such that IL-10 acquires pro-inflammatory functions and thus contributes to inflammation instead of suppressing it. A new area of investigation in our laboratory is the analysis of cytokine regulation of tissue destruction and remodeling.

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