It is feasible for a single-practitioner podiatry practice to add weight bearing CT (WBCT) imaging and realize economical and operational benefits, Dr. Nicholas Hugentobler, DPM, explained in a webinar titled, “Incorporating Weight Bearing CT Imaging into the Daily Podiatric Practice” on FOOTInnovate.
Dr. Hugentobler took over Animas Foot and Ankle in Durango, Colo., in 2012 and purchased a pedCAT WBCT system three years later. Since then, Animas has grown to seven total locations and eight doctors.
Dr. Hugentobler said the pedCAT makes financial sense if a podiatrist orders on average one CT scan per clinic day, and noted “my criteria for ordering a WBCT has expanded as I have been able to see the benefit.”
Dr. Hugentobler said he regularly orders WBCT studies for post-surgical fusion verification, fracture repair verification, post-surgical alignment verification and pre-surgical planning.
Dr. Hugentobler advised to always bill only what is appropriate and to always provide adequate documentation that would stand up in an audit or a peer-to-peer review.
An unintended benefit of adding the pedCAT to his practice was increased efficiency, Dr. Hugentobler said. An X-Ray study can take as much as 8 minutes depending on the technologist, he said. Often after reviewing the radiographs, a podiatrist will have to send the patient back for additional views. A pedCAT scan takes a little more than a minute, and provides unlimited X-Ray views via its Insta-X feature.
“I have a practice in an adjacent city which has three doctors at any given time,” Dr Hugentobler said. “They order about half as many X-Rays as I do alone [with the pedCAT]. I am earning more on X-Ray than anticipated.”
In the case above, the patient’s pedCAT Insta-X of the foot showed the patient had a mild bunion. Dr. Hugentobler said the X-Ray view did not explain why the patient had severe pain to the point where he could not walk. Navigating through the coronal slices on the the CT volume showed the patient’s sesamoid was directly underneath the crista and was grinding against it. “It won’t take long before that starts deteriorating in the wrong direction,” Dr. Hugentobler said. The pedCAT allowed for prompt and responsive treatment.
In another example, Dr. Hugentobler showed a 34-year-old female who had gotten an open reduction and internal fixation (ORIF) after a motorcycle accident. After surgery, her foot was fixed in a varus position. She was “bounced around” from doctor to doctor after surgery to try to figure out why. Providers suggested bracing, a calcaneal slide, etc. When the patient came to Dr. Hugentobler, he ordered a WBCT, which revealed a large bone mass in the subtalar joint was causing the misalignment. Further evaluation showed arthrosis and subchondral schlerosis.
“This gives you a better understanding of what really will be beneficial,” Dr. Hugentobler said, who recommended a fusion and injections to the patient.
A study found that performing 2D radiographs & traditional medical CT imaging for foot & ankle exams took an extra 800 hours of imaging time per year, as compared to performing only a pedCAT weight bearing CT scan for the same indications.
pedCAT image acquisition is 70% faster than radiographs and 35% faster than CTs. Patient positioning on the pedCAT does not require X-Ray emitter or sliding adjustment.
Some degree of subtalar joint subluxation, as well as sinus tarsi impingement, was found in approximately 70 percent of patients with flexible adult acquired flat foot (AAFD) in a recent imaging study using MRI and weight bearing CT (WBCT) imaging.
Investigators used the imaging to assess which soft tissue structures demonstrating MRI signs of degeneration would correlate and influence more positive findings of bone collapse.
The study results were on display in the poster section of the AAOS Annual Meeting and summarized by the AAOS Daily News.
Investiagators obtained MRI and WBCT imaging for 55 patients. Patients were evaluated for markers of arch collapse including increased valgus alignment of the hindfoot and forefoot abduction. Subfibular impingement was found in only 9 percent of patients.
“The significant and isolated influence of pronounced degeneration of the ligaments as positive indicators of more severe collapse of the bony architecture in AAFD patients, represented by subtalar joint subluxation and subfibular impingement, must be considered essential findings,” Dr. Cesar de Cesar Netto, a coauthor of the study, told AAOS News Daily. “Since we don’t really know which structures degenerate first in AAFD, our results point toward an increased importance of the ligamentous structures in the development and progression of the pathology, with the degeneration of the PTT potentially representing a late finding and only the tip of the ice berg.
The CurveBeam pedCAT is the only weight bearing CT imaging system with a field of view large enough to capture a bilateral foot and ankle scan. Flat foot degeneration is often a bilateral condition.
Injury to the syndesmosis often requires advanced imaging. Up until recently, the most common advanced imaging modality to evaluate this injury has been magnetic resonance imaging (MRI). Dr. Shadpour Demehri, MD, Associate Professor, Russell Morgan Department of Radiology, Johns Hopkins University, discussed the current imaging standards and the evolving role of weight bearing cone beam CT (WBCT) in a presentation he delivered to the WBCT International Study Group in July 2018.
In reviewing recent literature, Dr. Demehri explaind that MRI can reliably and accurately detect syndesmotic injury. There does not appear to be any difference between 3T and 1.5T MRI technologies, and further, there is no advantage to using contrast (MRA) when evaluating the syndesmosis. The biggest limitation of MRI studies is the lack of information regarding the significance of anatomic derangement and biomechanical instability. This limitation is where WBCT technology has emerged as a new tool for evaluation.
Dr. Demehri and his colleges conducted a study of asymptomatic patients to create an atlas of diastasis, rotation, translation, and ankle mortise measurements and range of normals. During this study, they were able to make three conclusions. First, defined syndesmotic measurements can be reliably performed on WBCT. Second, except for medial clear space, syndesmotic measurements did not vary with normal weight bearing. Finally, under physiological load, the relationship between the distal tibia and fibula remains unchanged in the presence of an intact syndesmosis.
The biggest limitation of MRI studies is the lack of information regarding the significance of anatomic derangement and biomechanical instability. This limitation is where weight bearing cone beam CT technology has emerged as a new tool for evaluation.
Considering the conclusions drawn from this initial study, Dr. Shadpour Demehri decided to further evaluate weight bearing versus non weight bearing studies in symptomatic patients. He explains that images were gathered in natural, weight bearing stance to allow for evaluation of comparative anatomy. If apparent syndesmotic injury was evident on plain x-rays or exam, those subjects were removed from the study. This allowed them to evaluate subtle injury more critically and assess the efficacy of typical patients sent for advanced imaging. The findings of this study revealed that in patients with prior ankle injuries, syndesmotic measurements using WBCT are feasible, reproducible, and had moderate to perfect level of agreement between observers. Values of syndesmotic measurements were significantly different between weight-bearing and non-weight bearing images.
As much of the radiology field continues to evolve with technology, Dr. Demehri sees great potential for the utilization of WBCT technology. He hopes to further investigate the role of automated measurements as well as automated bone segmentation and anatomical landmark localization. He believes that using these semi-automated techniques will allow measurements to be obtained using pre-defined anatomic landmarks. Ultimately, this will significantly improve workflow, intra-observer reliability, and level of agreement between radiology readers.
Watch Dr. Demehri’s full presentation here: