Intraoperative Imaging Pearls for Foot and Ankle Surgeons

When striving to optimize any aspect of the surgical process, thoughtful questioning can lead one to carefully consider relevant existing evidence and one’s practical experience. In this article, we will pose several such questions in hopes of inspiring fellow foot and ankle surgeons to maximize and enhance appropriate use of intraoperative imaging.

How Can We Minimize Radiation Exposure in Foot and Ankle Surgery?

A single intraoperative image of an extremity results in relatively low radiation exposure; however, complex cases may require many images over several hours, and live imaging with a large C-arm is standard practice. Due to the lower soft tissue and bone density in the foot and ankle compared to other parts of the body, one can routinely employ the low dose setting on such an apparatus, although the surgeon typically needs to convey this preference to the radiology technologist. Cases involving live imaging involve the highest exposure risk, and surgeons should consider the pulsed fluoroscopy setting, which significantly lowers radiation exposure. Images created with the pulsed settings have a lower resolution, although still adequate for a high percentage of operative situations. It is also possible to toggle the pulsed setting on or off when one desires higher resolution static views or videos.

What is the Surgeon’s Role in Obtaining Efficient Imaging?

The surgeon’s role in imaging significantly changes when using a mini C-arm versus a large C-arm. Most surgeons consider the mini C-arm as the more efficient option; however, the surgeon then bears a greater responsibility for positioning the tube, and possibly maneuvering the entire unit in and out of the surgical field without the help of a radiology tech. The surgeon may need extra hands when trying to simultaneously position the tube and the extremity, which may impact efficiency. The mini C-arm also has a limited field of view, possibly requiring multiple images to obtain the desired information. The large C-arm allows the surgeon to easily leave the unit in place while working, in contrast to the mini C-arm, which tends to be in the way when operating.

The surgeon relies heavily on the radiology tech to position the tube angle when using a large C-arm. This approach may take multiple images to find the correct AP, lateral or special view as the tech may have less depth of experience with foot and ankle imaging, or the foot may sit in a position that makes imaging difficult. Extremity surgeons have the advantage of positioning the foot or ankle to obtain the desired image, but this requires some degree of surgeon knowledge about image angles and clear communication between the surgeon and the tech.

Therefore, the surgeon’s role is not only to communicate the region of interest (forefoot, rearfoot, entire foot, ankle, etc.) and desired view, but also to position the foot or ankle for efficient and accurate imaging. In syndesmosis repair, the lateral ankle image is a good example where the surgeon may communicate “lateral ankle, show entire plate.” The tech now knows that visualizing the foot is unnecessary but will push the tube close to the ankle for a wider field of view to see the entire plate. The surgeon then uses one hand to dorsiflex the foot at the ankle to place the talus into the ankle mortise and uses the other hand to rotate the knee into position for a proper lateral ankle view. This process should be consistent enough to only need one static lateral image when done correctly. The surgeon and tech both evaluate the image to confirm no internal or external rotation of the extremity by looking at the talus to ensure proper overlap of the medial and lateral domes of the talus (single talar dome). Letting the foot dangle in a plantarflexed and inverted position during lateral ankle imaging is less efficient as the surgeon may not accurately assess tibial/fibular overlap in relation to syndesmotic reduction, which typically occurs leads to 2 to 3 more images. Positioning properly the first time saves time and reduces radiation exposure (see photos below).

Do Surgeons and Radiology Techs Speak the Same Language?

An unofficial language related to C-arm fluoroscopy may lead to miscommunication between the surgeon and rad tech. Team members may commonly use phrases and terms such as “wig-wag,” “rainbow,” “go north,” “more toes,” to direct the movement of the C-arm tube.   Unfortunately, these terms mean different things among different users and are at risk for misinterpretation. In 2013, Pally and Kreder recommended a standardized terminology based on anatomic directions (see illustration below).¹ Some level of preoperative communication between the tech and surgeon is helpful at the start of each case, especially when the team does not work together regularly.

How Does Procedure Type and Laterality Impact C-arm Positioning?

Due to limited reach, one typically places the mini C-arm on the ipsilateral side of the operation. The large C-arm is usable on either side since many foot and ankle surgeons stand at the foot of the bed. We find that the large C-arm often comes in from the contralateral side, which allows the surgeon or assistant to stand on the ipsilateral side. There are situations where ipsilateral positioning is useful, primarily when one desires to place fixation on the medial side of the foot or ankle under imaging. Ipsilateral positioning allows the surgeon to be on the contralateral side, the assistant to stand at the foot of the bed, and the C-arm to be out of the way when placing screws in cases like medial column fusion or medial tibial fracture plating. Handedness of the surgeon may also impact these decisions. It is important to communicate these preferences during the preoperative briefing since the OR staff and radiology tech will likely assume that the C-arm will always come in on the opposite side, as is the case for most orthopedic cases.

Patient positioning also impacts imaging efficiency. The lack of reach with a mini C-arm can create imaging challenges when bumping into the OR bed or contralateral limb. Having the heel hang off the end of the bed can make AP foot imaging easier due to less interference with the bed. A rolled blanket or hip bump under the ipsilateral hip can also prove very helpful to rotate the limb out of external rotation and achieve better imaging consistency.

How Does the Surgeon Obtain a Wider Field of View?

One can easily control field of view in standard X-ray imaging by adjusting the head tube aperture, but how does the surgeon or radiology tech control field of view when performing intraoperative C-arm imaging? Imaging the entire foot and ankle on one view can be challenging, even when using a large C-arm, which hinders intraoperative alignment assessment during reconstructive surgery. Here the surgeon can obtain maximum field of view by fully opening the tube head aperture and then placing the foot or ankle as close to the image intensifier as possible. In our experience, this will capture the greatest amount of the foot or ankle and will allot the surgeon the highest quality image possible (see images below).

Moving the head tube away from the body results in a narrow field of view, but the area of interest becomes magnified. Both of these maneuvers are useful depending on the circumstance, but the radiology tech will need guidance from the surgeon as to the preferred image. Most mini C-arm units have control settings that allow either magnification or a wider field of view, but the field of view will be smaller than when using a large C-arm if using the magnification setting. One should note that using the magnification setting will increase the radiation exposure; therefore, moving the body part closer to the intensifier is the ideal method.

Can Surgeons Simulate Weight-Bearing During Imaging for Foot and Ankle Surgery?

Boffeli and Mahoney described a simulated weight-bearing lateral imaging technique for midfoot fusion, which correlates with the 10-week postoperative weight-bearing images regarding sagittal plane alignment.² Using the same technique in reconstructive flatfoot surgeries, Boffeli and Duelfer correlated intraoperative images with the 10-week postoperative weight-bearing images regarding sagittal plane alignment.³ A flat surface loads the foot during lateral imaging rather than using a mallet or the surgeon’s hand alone (see photos below).

Visual assessment for proper lateral alignment involves:

• a singular talar dome;

• clear visualization of the fifth metatarsal styloid process; and

• mild superimposition of the navicular and cuboid.

These criteria should serve as a checklist intraoperatively to ensure obtainment of an appropriate simulated weight-bearing lateral radiograph. The plate position is at 90 degrees to the image intensifier, and the surgeon loads the foot using the palm the hand with the ankle dorsiflexed to 90 degrees and the toes pointed to the ceiling by internally rotating the knee. Once positioned, the image intensifier should move in as close as possible to the foot to capture the greatest area possible in one view.⁴

Boffeli and Waverly described a simulated weight-bearing long-leg axial (WB LLA) image, primarily used to evaluate the frontal plane alignment of the calcaneus in relation to the long axis of the tibia.5 The simulated WB LLA imaging protocol often applies to rearfoot osteotomy or arthrodesis, calcaneal osteotomy or fracture repair, rearfoot arthrodesis, ankle arthrodesis, total ankle arthroplasty, and supra-malleolar osteotomy. This image aims to superimpose the second metatarsal through the tibia while attempting to capture a simulated weight-bearing resting foot position. The ankle position is at 90 degrees, with the foot loaded in a simulated weight-bearing position using a radiolucent flat plate. One positions the C-arm at a 45-degree angle, with the leg rotated to position the second metatarsal at 90 degrees to the floor to achieve the desired tibia-through-second metatarsal alignment (see images below). There is no attempt made to alter the foot-to-leg position, which is held in simulated resting calcaneal stance position. The goal is to capture as much of the tibia as possible without cutting off the heel. Positioning the image intensifier close to the toes helps in this regard.⁵

What Considerations Apply to Ankle Replacement Surgery?

Each total ankle replacement (TAR) implant brand has unique specifications and built-in visual assessments that serve as cues to indicate proper alignment of a cutting jig or step in the procedure. This may involve razor-thin edges along the implant surface or lining up of “perfect circles” along the jig or the implant, denoting achievement of proper imaging. It is important that the surgeon is intimately familiar with these visual cues. This often requires a great deal of imaging to obtain proper alignment. We find live imaging is common practice in TAR surgery, and this is an excellent scenario in which to consider the pulsed fluoroscopy setting for live imaging. The tech can then toggle back to the standard low-dose setting when there is a desire for a higher contrast image. It is helpful when the tech understands what the surgeon is trying to see, as they may be able to improve imaging efficiency by adjusting the head tube angle. One can achieve this understanding through proper surgeon-tech communication.

Closing Thoughts

Efficient intraoperative imaging equates to obtaining the proper views, in the optimal order, in the least amount of time, and with the lowest radiation exposure. Efficient imaging lowers the overall radiation exposure to the patient, surgeon, and OR staff, while accurate imaging is a predictive measure for postoperative outcomes in simple and complex surgical interventions. A core principle in intraoperative imaging is to obtain radiographic views similar to those one will obtain postoperatively and develop a protocol that assures that the highest quality images through proper foot and ankle positioning and proper imager positioning.

Dr. Boffeli is director of the Foot and Ankle Surgical Residency program at Regions Hospital/ Health Partners Institute for Education and Research in St. Paul, MN.

Dr. Duelfer is a third year resident at the Foot and Ankle Surgical Residency at Regions Hospital/ HealthPartners Institute for Education and Research in St. Paul, MN.

Dr. Lubek is a third year resident at the Foot and Ankle Surgical Residency at Regions Hospital/ HealthPartners Institute for Education and Research in St. Paul, MN.

1. Pally E, Kreder H. Survey of terminology used for the intraoperative direction of C-arm fluoroscopy. Can J Surg. 2013;56(2):109-112. doi: 10.1503/cjs.015311

2. Boffeli T, Mahoney K. Intraoperative simulated weightbearing lateral foot imaging: the clinical utility and ability to predict sagittal plane position of the first ray in Lapidus fusion. J Foot Ankle Surg. 2016;55(6):1158-1163. doi: 10.1053/j.jfas.2016.06.004

3. Boffeli T, Duelfer K. Predicting postoperative sagittal plane alignment of the foot using intraoperative simulated weightbearing lateral imaging during flatfoot reconstructive surgery: a short-term retrospective analysis. J Foot Ankle Surg. 2021;60(4):718-723. doi: 10.1053/j.jfas.2021.01.007

4. Sanner WH. Foot segmental relationships and bone morphology. In: Christman RA. Foot and Ankle Radiology. Churchill Livingstone;2003:287-296.

5. Boffeli T, Waverly B. Angle and base of gait long leg axial and intraoperative simulated weightbearing long leg axial imaging to capture true frontal plane tibia to calcaneus alignment in valgus and varus deformities of the rearfoot and ankle. J Foot Ankle Surg. 2016;55(5):1043-51. doi: 10.1053/j.jfas.2015.09.002