Weightbearing CT Allows For Advanced Surgical Planning

Written by: Dr. Bob Baravarian, DPM, FACFAS

The foot is an amazing feat of engineering consisting of multiple moving parts controlled by multiple pulleys and levers. The fact that the foot and ankle can withstand such high pressures and weight levels without failure over the course of a lifetime is truly amazing.

Furthermore, the fact that the foot and ankle have such diverse shapes, sizes and mechanical positions in different people, but still tend to function at such a high level is again truly amazing. In the spirit of architectural advancement, I thought it would be interesting to consider the advancements in architecture and compare them to the potential advancements in foot and ankle surgery, and how the thinking of both should be similar.

Within architecture, the computer has created significant advancements in preproduction and preconstruction planning. What used to take several months to years to plan and design with hand drawings, slide rulers and calculators can now happen in mere hours to days through the advancements of computer technology. Three-dimensional schematic designs have become so advanced that we can show a building in slices, rotate it, and even pull it apart to show minute details as part of the planning cycle.

The advent of advanced computer renditions allows for placement of each and every part of large, dynamic buildings in the proper position. Architects can plan interiors and order them prior to breaking ground on the buildings. Rooms can be visible in full color and functional design, which can help in sales and marketing as well as planning. Most critically, architects can plan and calculate the actual building including elevator chutes, floor setup and even outlet placement in minute detail levels that make the construction process exceptionally easy and smooth in comparison to 60 years ago.

I always loved the idea of building things as a teenager. I would make my bike better. I would think about building a house or a building. I loved the details and the process. However, I was drawn to medicine and the combination of the social aspect, the surgical aspect and the compassionate care aspects. Over time, I grew to feel the two fields had a lot in common as I was “constructing a foot and ankle” instead of a building. What was astonishing to me is the fact that we plan and detail a building to such high level, yet we do not plan and detail a surgical procedure to the same level of detail. Why is that? Does it make sense? To me, there has been a need for advancement of preoperative surgical planning in foot and ankle surgery that has not occurred until the introduction of weightbearing 3D computed tomography (CT) scanning.

Reinventing Our Approach To Surgical Planning

The pedCAT (CurveBeam) CT technology allows for significant preparation and makes the surgical process less artistic and more scientific. Much like the use of a computer system to plan our construction of a building with multiple drawings and 3D renderings, the pedCAT CT allows for multiple angle and plane images as well as 3D renderings that make the surgical planning process much easier. As I noted earlier, I have always found myself somewhat feeling that surgery is an art. “You have to have good hands to be a surgeon,” I tell myself. “You have to think outside the box.”

However, as I have become more involved in real estate investments in recent years, I have noticed that the architects of projects are part artist and part planner. They have “good hands” and come up with imaginative and sophisticated ideas for buildings. However, they follow up on this with advanced computer imaging and planning in order to avoid errors, and make sure their thoughts and designs make sense in the real world. Why is this not the case in foot and ankle surgery planning? I have good hands and I believe I am artistic in my surgical concepts, but why am I not planning the surgery out like an architect or engineer to make sure all the pieces make sense and the surgery will go as close to plan as possible?

The process of considering the addition of 3D imaging and weightbearing multi-plane imaging to my surgical process started with advancements in knee and hip surgery. I operate in an OR next to a knee and hip replacement surgeon on some days, and noticed that he had a computer system in the room that would allow him to have an exact planned osteotomy site with surgical exactness that made leg length issues and acetabular rotation and fit issues far less common. He would note that he has not had more than a ¼-inch leg length issue since he started using the computer-assisted system. This technology has cut down his surgery time by 30 percent and his surgeries have become far more reproducible. The “art” of surgery is in the planning stage, not on the fly in the operating room.

I then began performing my ankle replacements using the computer-guided surgical planning system. I found that my surgical time decreased by 40 percent and my ankle replacements became far more reproducible.

What was also astounding is how many times 3D CT imaging saved me from a surgical disaster. I recall one patient who was a very healthy, very active gentleman who ran every day but he had an arthritic ankle. After deciding on ankle replacement, I ordered the preparatory CT scans for the cutting guide designs and found that the patient had a completely hollow distal tibia and talus. There was absolutely no bone in these regions.

If I had not gotten the CT scans, which I would not have done five years earlier, I would have been in the operating room with a disaster on my hands. After this case, I began to consider the planning phase of surgery as the most important phase instead of just a phase to get into the operating room.

How The Author Uses 3D Weightbearing CT

I began using the weightbearing CT primarily for my complicated multi-plane deformities. This included ankle and hindfoot reconstructions and flatfoot multi-planar corrections. The technology was amazing. I would dial in my angles of correction, plan the size of my graft for an Evans procedure and even plan the amount of rotation necessary for anatomic alignment of the foot and ankle. I would often do one scan with the foot in angle and base of gait, and then get a second scan with the foot in the corrected position. This allowed me to compare the preoperative position to the postoperative ideal position and figure out how to go from before to after in a systematic and architectural manner.

Over time, I began to use the CT system for some of my forefoot procedures. I have extensively used the CT for my bunion and hallux rigidus procedures. In hallux valgus cases, I again use a preoperative position scan to a post-corrected hindfoot to forefoot position. By doing so, I can determine if a hindfoot alignment correction is necessary, if the first ray is severely elevated and needs to be plantarflexed, and if there is first ray rotation that I need to consider. In hallux rigidus cases, I have begun to use the CT to plan my osteotomy. I consider the preoperative level of arthritis and articular damage, the possibility of cartilage graft procedures, and if the procedure selection truly makes sense for the level of arthritis present. This is impossible to do at such high levels with plain radiographs. Plain radiographs leave the surgeon blind at the time of surgery and having to plan on the fly what he or she could have planned at the preoperative level.

Finally, I even began to use the 3D CT in my forefoot lesser ray procedures. The Weil osteotomy is extremely strong in correction of metatarsal length but it plantarflexes the metatarsal level to the phalanx level. This subsequently places the angle of the toe above the level of the metatarsal head, resulting in a floating toe. However, with preoperative planning, one can plan the Weil osteotomy with a dual parallel cut technique, which elevates the metatarsal equally with each millimeter of shortening. This allows improved anatomic position and weight distribution of the ray to the toe, resulting in fewer floating toe issues.

In Conclusion

My intention is to make my fellow surgeons consider the surgical procedure similar to a construction project. No contractor would build a building without a full set of plans, cross-sectional diagrams and 3D renderings. We should plan accordingly for our surgeries. As the software programs become more advanced, we may be able to perform osteotomies and shift the bones in our preoperative planning. This will allow even more advanced planning along with far less operative time and less risk to the patient. We owe it to ourselves and our patients to consider these options prior to surgery.

Dr. Baravarian is an Assistant Clinical Professor at the UCLA School of Medicine. He is the Chief of Podiatric Foot and Ankle Surgery at the Santa Monica UCLA Medical Center and Orthopedic Hospital, and is the Director of the University Foot and Ankle Institute in Los Angeles.

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