Surgical operations and mathematics

Summary: Mathematical models can be used for various aspects of surgical operations in order to predict effects and improve recovery.

Surgery is the branch of science that typically involves medical treatment through an operation. There are a variety of reasons for why a surgery is performed. Diseases such as cancer and various forms of heart disease may be treated through surgical procedures.

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When cancer is found, surgery may be performed to remove a tumor in order to reduce the likelihood of the cancer spreading or to alleviate pressure caused by a tumor pressing against another organ. Heart surgeries include a heart transplant, a coronary artery bypass, or a heart-valve repair or replacement. Injury is usually treated with surgery when the body is unable to repair itself. Torn ligaments or tendons can be surgically treated through reattachment or replacement. Burn victims can be treated with a skin graft as a permanent replacement for the damaged skin. Deformities can also be treated with surgery. Spinal fusion surgery can be used to treat spinal deformities like scoliosis. A cleft lip and palate is a fetal deformation that can be corrected with surgery soon after birth. The surgery usually involves an incision with medical instruments. Surgical incisions can vary in size from large incisions, such as in some open-heart and brain surgeries, to tiny incisions, such as in the case of laparoscopic procedures. The advantage to smaller incisions is that the wound heals faster, leaves a smaller scar, and reduces the likelihood of infection.

Mathematically Modeling Surgery

Improving surgical techniques and devising new surgical procedures is an active area of research. Multidisciplinary approaches are required for developing successful techniques and procedures. The National Institutes of Health (NIH) has stated that these approaches should include computational and mathematical simulations to facilitate this biomedical research. Simulations can be accomplished, in part, through mathematical modeling.

Mathematical modeling is the process of using a mathematical language in order to describe, in this case, a biological phenomenon treated with a biomedical procedure. While any mathematical model is a simplification of reality, computational solutions of the mathematical model may provide useful insights for researchers and clinicians when the model has been formulated under biologically and physically sound principles with realistic treatment strategies.

In order to develop a mathematical model for surgical treatment, it is common to have a team of researchers work closely on a given problem because of the different areas of expertise needed to address what is likely a complex biomedical problem. The first step is for the researchers or clinicians to define, as clearly as possible, the problem or question that they want the modeler to analyze and identify the benefits of the modeling project. From there, they should work to determine the appropriate scales with which to study the problem. Is the most appropriate scale at the molecular, cellular, or tissue level or is it more of a systemic problem? Is the time scale (if there is assumed to be temporal variation) on the order of minutes, days, or years? Answers to these questions will help determine if the model is best described in terms of discrete units or continuous variables, whether temporal or spatial variation should be included, and if a deterministic or statistical approach is more appropriate. This will also help determine what computational platform and method might best be used to analyze the question at hand. Developing a model diagram can help visualize the model formulation and process. From there, the research team needs to decide how best to access the quality of the model. From the model formulation, what are the assumptions and model limitations? Are the assumptions biologically reasonable? Are there data that can be used to quantify some of the model parameters? Are there data that can be used to quantitatively or qualitatively compare to the initial model simulations? If the research team is at the beginning stages of a new surgical treatment, can the model be developed to put forth hypotheses tested for animal experiments or clinical trials? The mathematical model works best as an iterative process when the modeler and experimentalist or clinician exchange ideas. The first set of suggested guidelines for biomedical research teams with mathematical modelers was proposed for the mathematical modeling of acute illness.

Applications

In connection with surgical procedures, mathematical models can be used in a variety of ways. Mathematical models may be used to predict the likelihood of a surgical procedure’s success. For example, in reconstructive microsurgery (where skin tissue is moved from one location to another), a mathematical model was developed to predict successful tissue transfer based on oxygen delivery, tissue volume, and blood-vessel diameter. Mathematical models can be used to explore ways of making existing surgical procedures more successful. Stents are tubes inserted into a blood vessel (or another tubular body part) to keep open the vessel but are associated with a higher risk of a heart attack or a blood clot. A mathematical model was developed to analyze drug delivery to stent locations where two or more arteries meet.

Mathematical models can be developed to analyze controversial questions. For example, a model was developed to analyze whether a more liberal or constrictive allowance of fluid level allows for a more successful recovery from abdominal surgery. Mathematical models can be used to predict changes following surgery. A model was developed to predict changes in the knee joint following a wedge osteotomy, which is the removal of a wedge region of bone around the knee. The model was validated by predicting the results of 30 patients undergoing the surgical procedure, then the results were compared to actual measurements 14 months after surgery. In spite of these efforts, mathematical modeling of surgical procedures (and questions related to the surgical procedures) is still a relatively new concept.

Ideally, mathematical models can be used on individual patients to predict a likely and optimal outcome when considering surgical treatment. With advances and improvements in imaging techniques and computer software, this may be possible for treatment of some diseases and injuries. For example, when dealing with more complex arterial geometries near stent locations, researchers may be able to predict appropriate drug treatment strategies. However, in the absence of patient-specific models, mathematical models may be used to help clinicians make decisions based on patient variability. Patient variability implies that although there are differences in individual patients, there may be common characteristics in subpopulations of patients with a similar disease or injury. These common characteristics might be measured in common biomarkers from urine or blood analysis or similarities in imaging analysis. Mathematical models can be used to investigate surgical treatment strategies for patients with similar characteristics.

Mathematical models can also help with the development of new treatment surgical protocols or the analysis of existing treatment strategies. When exploring these questions, it is common for researchers to conduct experimental trials on animal models. However, animal experiments can be time consuming and costly. Mathematical models used to analyze a given question can provide a significant cost savings. For example, computer simulations of the model can be used to initially screen different experimental trials in order to decide which ones are worth pursuing and which are not. Furthermore, successful experimental results on animals do not guarantee the same level of success in clinical trials on humans. Mathematical models can not only give an idea as to how experimental trials on animals translate into surgical treatment on humans but also provide necessary insights when animal experiments are not possible or clinical trials on humans are unethical.

To help address the many questions that arise from current surgical procedures and the development of new surgical methods, an interdisciplinary team of researchers is required to formulate and analyze the problem at hand. It has been suggested that the team include mathematical modelers. Mathematical modeling can potentially provide a way to investigate novel treatment strategies and predict possible problems that may arise for a given surgical procedure. Furthermore, there exists the possibility of significant cost savings, in part, by reducing the number of animal experiments or clinical trials performed. In these ways, the mathematics underlying the description of the biology can be beneficial to the surgeon or biomedical researcher.

Bibliography

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