CurveBeam is thrilled to announce the launch of its official podcast – CurveBeam Connect.
Each month, CurveBeam will bring its listeners voices from the clinic, the radiology reading room, medical conferences and more.
The featured guest for CurveBeam Connect’s inaugural episode is Dr. Francois Lintz, MD, a foot & ankle orthopedic surgeon at Clinique L’Union in Toulouse, France. He discusses why he believes weight bearing CT imaging should replace conventional radiography as the gold standard for diagnostic imaging of lower extremity conditions. He also discusses how he conceived the idea for TALAS, a semi-automatic tool for measuring hindfoot alignment in three dimensions.
You can listen to the podcast by hitting the play button on the player above.
Make sure to subscribe to CurveBeam Connect on iTunes and Spotify to stay up to date on the latest episodes.
Ankle syndesmosis injury is one of the most common cases seen by foot and ankle specialists. An estimated 11% of all ankle injuries and 8.5-18% of all ankle fractures have injury to the syndesmosis. An inaccurate diagnosis can lead to chronic problems or repeat surgeries. Common indications for delayed surgery or reoperation include improper diagnosis, malreduction and inadequate fixation.
The syndesmosis connects the tibia and fibula above the ankle joint. One of the most difficult distinctions to make is whether the injury is isolated to the syndesmosis itself or if it has affected the stability of the ankle joint as well.
Dr. Daniel Guss, MD, MBA, assistant professor of orthopedic surgery at Harvard Medical School, took a deeper look at syndesmosis and how weight bearing CT imaging could improve diagnostic ability in a presentation he delivered to the WBCT International Study Group in July 2018.
Syndesmosis – Variabilities Are Common
The ankle syndesmosis serves two main functional purposes. First, it is designed to maintain the spatial relationship between the tibia and fibula in order to stabilize the ankle mortise throughout weight bearing activity. Second, it allows for flexibility of the ankle mortise in the coronal plane along the talar dome throughout various degrees and dorsiflexion and plantarflexion.
Dr. Guss reminded clinicians that when assessing the functional ability of the syndesmosis, it is important to note that recent studies have shown considerable variability in the concavity of the incisura, bony overlap, and clear space within the ankle mortise from one patient to another. In this regard, comparative anatomy images of the left and right ankle are essential for a thorough evaluation.
During a physical exam, the most common tests for evaluation of syndesmosis injury are external rotation stress test, calf squeeze test, and cross-legged test. By and large, all of these tests give greater indication of injury, but all have low sensitivity and specificity, Dr. Guss said. In addition, a positive test from any of these maneuvers is not considered diagnostic.
Imaging – Need for Contralateral Evaluation
Once history and physical exam have been completed, most clinicians turn to initial standard radiographs for evaluation. Tibia/fibula overlap, tibia/fibular clear space, and medial clear space are most often the areas of focus for more definitive diagnostic information in regard to instability. Most will attempt dynamic stress radiographs with high level of clinical suspicion.
However, Dr. Daniel Guss explained the importance of contralateral evaluation, as there has been great variability in measurements of the syndesmosis using weight bearing CT imaging within the same joint when measured in neutral, maximum external rotation, and maximum internal rotation. There is also evidence of significant syndesmosis measurement difference in weight bearing versus non-weight bearing images of uninjured ankles. This further illustrates the flexibility of the syndesmosis as a support structure.
Finally, if MRI is believed to be necessary, it is important to remember that this modality is very successful at detecting injury, but it does not shed any light on instability as it is a non-weight bearing image, Dr. Guss said.
Case Study – Undetected on X-Ray
Dr. Guss shared a case in which a 20-year-old male fell down a flight of stairs and thought he had sprained his ankle. He went to his college health services and obtained an X-Ray, which was negative for fracture. However, the X-Ray did show subtle calcifications within the syndesmoses.
X-Rays taken four months later at Dr. Guss’s clinic showed heterotopic ossification in the syndesmotic region.
Dr. Guss ordered a pedCAT weight bearing CT so he could assess the HO further. He was able to see the asymmetry under physiologic load at the distal tibio-fibular articulation and also that the HO was forming posterio-laterally.
The patient ultimately underwent an excision of the HO and fixation.
Case Study – Subtle Asymmetry
Dr. Guss shared another case where a Gentleman in his 50’s presented to the ER complaining of right ankle and lower leg pain after slipping on ice. Traditional x-rays were obtained, and he was diagnosed with a Maisonneuve-type injury with proximal fibula fracture and medial ankle sprain.
Upon follow up, the patient had a weight bearing CT scan done of both ankles that allowed for cross-section comparison under physiologic stress. This scan revealed subtle asymmetry and widening between the distal tibia and fibula of the injured right ankle compared to the non-injured left ankle.
Subsequently, this patient went on to have surgical fixation performed despite being told originally that he had simply sprained his ankle.
In conclusion, syndesmosis injury can be easily missed and yet carries long term implications for functional instability and chronic pain. When considering what imaging studies are necessary, it is essential to look at weight bearing and contralateral images to obtain a thorough picture of functional anatomy specific to that patient. As weight bearing CT technology becomes more widely available, this may be the most streamlined way to evaluate bilateral, weight bearing images to diagnose ankle syndesmosis instability.
Daniel J. Cuttica, D.O. will share his experience using weight bearing CT in clinical practice in this webinar titled, “Applications of weight bearing CT in common foot & ankle disorders“. Dr. Cuttica is a foot and ankle surgeon practicing at the Orthopaedic Foot & Ankle Center division of the Centers for Advanced Orthopaedics, in Falls Church, Virginia. He is an Assistant Professor of Clinical Orthopaedic Surgery at Georgetown University School of Medicine, and the author of numerous publications in foot and ankle journals.
The University of Kansas Medical Center Research Institute Department of Rehabilitation Medicine has received a grant from the National Institute of Arthritis Musculoskeletal and Skin Diseases (NIAMS), one of the 27 Institutes and Centers at the National Institutes of Health (NIH), to fund three years of research on the usefulness of bilateral weight bearing CT imaging and the critical need for more sensitive and affordable imaging biomarkers.
Osteoarthritis (OA) is the most prevalent form of arthritis, and the knee is the most commonly affected weight-bearing joint. The high cost of clinical trials creates a barrier for effective treatment development. Therefore, introduction of more specific and sensitive biomarkers could help to advance therapeutic development by reducing the time and sample sizes required for clinical trials.
There is an urgent need for imaging biomarkers that allow for identification of the best time in which patients will respond to treatment, and a means to analyze the efficiency of interventions. Early studies demonstrated the diagnostic value of bilateral weight-bearing CT in identifying knee OA symptoms accurately, as well as the feasibility to detect meniscal tears not detected by non-weight bearing MRI.
The grant from NIAMS will fund a study to validate the proposed imaging biomarkers and begin the qualification process for more responsive OA imaging biomarkers acquired using low-dose, bilateral standing CT imaging. Substantial advantages are offered over traditional radiographic biomarkers, including increased responsiveness to temporal changes in the joints, and a better reflection of the symptoms and severity of the disease. Additionally, this research will determine the prognostic validity of standing CT findings for detecting progression and worsening pain in people who currently suffer from or are at risk for knee OA.
With the support of NIAMS, this research holds promise to detect joint damage earlier, and accelerate the pace of scientific discovery and clinical trials. The continuing impact will be evident through a shift in knee joint imaging with an improved biomarkers for monitoring knee OA disease features. If the additional meniscal extrusions detected on bilateral standing CT are clinically relevant, then standing CT could improve identification of the most appropriate patients for clinical trials – those at risk of rapid OA progression. Successful completion will provide improved biomarkers that will help those who suffer from knee OA through making clinical trials more affordable and accelerating therapeutic improvement.
For more information on visualizing cartilage and menisci in the knee using standing CT arthrogram versus MRI, click here.
The Radiological Society of North America (RSNA) commenced its 103rd Annual Meeting in Chicago on Sunday, Nov. 26, 2017.
Attendees from around the world gathered to learn about the latest advances in imaging.
In an afternoon session titled “Open Gantry Systems: Advances, Challenges, and New Applications,” Dr. Jeffrey H. Siewerdsen, PhD, of Johns Hopkins Biomedical Engineering, discussed the vast applications of cone beam CT for interventional and diagnostic imaging. The devices presented included C-arms for image guided surgery, Cone Beam CT guided radiation therapy systems, and diagnostic imaging devices for breasts, dental/ENT, and orthopedic extremities. Siewerdsen emphasized the revolutionary potential of weight-bearing extremity devices in orthopedic specialties, and mentioned the CurveBeam pedCAT and LineUP systems. He also discussed the image quality parameters of Cone Beam CT and artifacts specific to this type of imaging. He offered suggestions on how to quantify image performance of such systems, many of which are relatively new and do not have established quality metrics in the imaging community. Finally, he presented some of the newest Cone Beam CT devices to come to market, including the extremely compact CurveBeam InReach made primarily for hand and wrist imaging.
When a patient appears to have a bunion, a physician typically orders traditional foot X-Rays as part of the clinical evaluation. The X-Rays capture three views of the foot- dorsoplantar, medial oblique, and lateral. But is this enough information to understand complex, three-dimensional object such as the foot?
A growing number of foot & ankle specialists are advocating that there may be better way to evaluate this common deformity.
“Weight bearing computed tomography scans are beginning to take our understanding to the next level,” Dr. Paul Dayton, DPM, of Des Moines, IA, said in a roundtable discussion on bunions published in the Foot & Ankle Specialist academic journal. “Once you see the connection between coronal rotation and what we have traditionally evaluated on AP radiographs, it opens up a whole new understanding.”
On X-Rays, physicians have to “mentally interpolate” the valgus component of the bunion because they do not adequately capture the frontal plane, said Dr. Robert Weinstein, DPM, FACFAS, of Atlanta, explained in a CurveBeam case study.
“Since the condition is a tri-plane deformity, we need to understand all of the components and their angular values contributing to the deformity,” Weinstein said. “Better deformity analysis leads to better pre-operative planning, surgical execution, and post-operative results.”
The new data on the coronal position is “exciting” because it explains so many of foot and ankle specialists’ previous questions, Dayton said.
Weight bearing CT imaging also allows for evaluating deformities that involve external rotation. Rotation of one or more metatarsals, including displacement of the sesamoids, cannot be clearly seen in standard foot X-ray imaging. The lack of the weight-bearing aspect in traditional medical CT imaging means the physician cannot evaluate displacement and rotation under load.
“It has long been known that in hallux valgus or bunions the relationship between the metatarsal head and the sesamoids is altered,” Andy Goldberg, MD, MBBS, FRCS (TR and Orth), of Stanmore, United Kingdom, told Lower Extremity Review magazine. he said. “The sesamoid bones should sit underneath the metatarsal head, while in hallux valgus the big toe drifts off the sesamoids and the tip of the big toe points outwards. But our research has shown that in many cases the cartilage is worn, which in essence is localized arthritis, and we believe that this could affect the outcome of surgery.”
Weight bearing CT images could have an impact on the technique a physician selects to repair a bunion, Dr. Dayton said.
“The knowledge that the sesamoids can be in normal position medial and lateral to the crista yet look dislocated on the AP X-ray because of pronation completely changes our mindset about the need for capsular balancing,” Dayton said. “We can see that in those cases supination corrects the deformity.”
Is there a reliable method to predict the type and perhaps the extent of osteoarthritis one might find in the ankle? Based on a recent article, which the examined the varus and valgus orientation of the talus and the configuration of the subtalar joint under weight bearing conditions, the possibility is there.
“A majority of the patients with ankle osteoarthritis present with an asymmetric wear pattern (eg, varus or valgus type),” according to a study published in 2009 by Valderrabano V, Horisberger M, Russell I, Dougall H, Hintermann B. titled, “Etiology of ankle osteoarthritis.”
Evaluation of these wear patterns, however, remained a challenge until recently, when Nicola Krähenbühl, MD, Michael Tschuck, Lilianna Bolliger, MSc, Beat Hintermann, MD, and Markus Knupp, MD published “Orientation of the Subtalar Joint: Measurement and Reliability Using Weightbearing CT Scans.” (Foot & Ankle International® 2016, Vol. 37(1) 109–114.)
Osteoarthritis of the ankle joint is relatively common and found in 1 percent of the world’s population, and a majority of those patients present with an asymmetric wear pattern (eg, varus or valgus type), according to the authors. Furthermore, up to 60 percent of the patients suffering from an osteoarthritic ankle joint develop talar tilt with progression of the osteoarthritic process.
Current research suggests this condition is caused by deformities of the lower leg and knee joint, ligamentous laxity, tendon dysfunction and neurologic disorders. Recently, it has been proposed that the adjacent joints and, particularly, the subtalar joint may have a major influence on this process. “However, it is rather difficult to evaluate the orientation
of the subtalar joint using conventional radiographs; CT scans would be more appropriate,” the authors posit.
To distinguish between varus/valgus configuration of the subtalar joint, Van Bergeyk et al introduced the subtalar vertical angle (SVA) in 2002 using non weight bearing CT scans. “Today, weight bearing CT scans can be performed, leading to a better understanding of the functional anatomy of the hindfoot,” the article states.
Weight bearing CT technology became available in 2012. Weight bearing imaging only had been available in 2-dimensional X-Ray imaging prior to this, but weight bearing combined with computed tomography was needed to properly measure the SVA without superimposition of non-relevant anatomy that might throw off the measurement, including analyzing the shape of the subtalar joint. The subtalar joint is especially difficult to clinically and radiographically assess in 2D, due to the superimpositions, and attempts to artificially stress the joint and then scan using a conventional (non weight bearing) CT produced inconsistent results.
“Using weight bearing CT scans, we assessed the reproducibility of the SVA and analyzed the orientation of the subtalar joint in patients with asymmetric ankle osteoarthritis. We hypothesized that the SVA would provide reliable and reproducible measurements in varus ankles presenting with a varus subtalar joint and valgus ankles with a valgus orientation of the subtalar joint, respectively,” the authors said.
Using the new technology to view the joints, including utilization of the SVA measurement, the authors concluded the SVA measurements were reliable and consistent. “In our cohort, varus osteoarthritis of the ankle joint occurred with varus orientation of the subtalar joint whereas in patients with valgus osteoarthritis, valgus orientation of the subtalar joint was found,” the study said.
The authors found the results for the healthy cohort were significantly different, suggesting the orientation of the subtalar joint may play an important role in the development of ankle joint osteoarthritis.
Weight bearing CT not only allowed the authors to clinically and radiographically assess the ankle joints under the patient’s normal weight bearing conditions, but it also enabled them to make consistent and reproducible measurements.
His decade old X-Ray system was failing, and feeling like a warrior without his weapon, Dr. Michael Chin, DPM, knew it needed to be replaced fast.
“We could have gotten a DR system, but at the end of the day, I wanted something that was unique, and something that would change the way I practice,” Dr. Chin said.
Dr. Chin participated in a panel discussion about new technology at the Foot and Ankle Business Innovations meeting in Chicago on Jan. 30. Dr. Chin practices at The Running Institute in downtown Chicago.
Dr. Chin uses the pedCAT for all of his X-Ray and CT imaging. His X-Ray revenues cover the device’s monthly capital lease payment, and the approximately 20 CTs he and his associate order every month provide his practice with an additional revenue stream.
Dr. Chin said he is able to order a CT scan and his staff can get payer authorization in the same day. This saves his patients from having to come in for a follow-up visit.
“We can fill that slot that we would have used for a follow up with another patient,” Dr. Chin said.
Dr. Michael Chin, DPM, presented how weight bearing CT imaging has changed how he evaluates cuboid subluxations at the American Academy of Podiatric Sports Medicine meeting held near the West Point Military Academy campus in early September, 2015.
Dr. Chin began using the pedCAT in his office in February of this year.
Not much research is out there on how to use plain radiographs to measure cuboid subluxations, Dr. Chin said in his lecture, titled, “Cuboid Syndrome…The Other Side of Heel Pain.”
Dr. Chin has tested using a bilateral oblique projection to understand the cuboid/ metatarsal relationship, and has been able to observe a slide between the head of the fourth metatarsal and the head of the cuboid.
An MRI could be ordered to see the condition of the peroneal tendon, but the study would be limited because the scan would not be weight bearing, he said.. A traditional CT scan would provide great visualization of the bone, but would provide no information on anatomic alignment.
The pedCAT weight bearing CT imaging system is excellent for evaluating stress fractures, sesamoids, periosteal changes, or anything medullar, Dr. Chin said. Another benefit is he can measure the exact degree of subluxation between the cuboid and the fourth metatarsal head.
Dr. Chin displayed pedCAT images depicting pre and post-reduction views of a cuboid subluxation.
Dr. Chin practices at The Running Institute in Chicago.
Weight bearing CT is a vital tool for determining the cause of inexplicable pain, and also for avoiding painful surgical complications.
That was the takeaway message from a talk by Dr. Phinit Phisitkul, a clinical associate professor of orthopaedics at the University of Iowa. He shared some of his most interesting cases at a CurveBeam sponsored symposium held during the AOFAS Annual Meeting in Long Beach during the evening session.
We’ve selected three of his cases to share on this blog:
18-year-old male with Noonan Syndrome & severe flat foot: The patient presented with an unusual amount of pain that was difficult to diagnose on plain X-Ray. A weight bearing CT scan revealed he had a severe deformity – a congenital vertical talus. He also had severe impingement.
58 year-old male with ankle arthritis: The patient presented with a lot of pain in the ankle joint. A weight bearing CT scan showed a subluxation of the ankle joint and dramatic impingement of the calcaneal fibula. Interestingly, the subtalar joint was in pristine condition. Dr. Phisitkul determined the patient was a good candidate for ankle replacement and hindfoot realignment, and that his subtalar joint could be spared.
41-year-old female with Hallux Valgus: A weight bearing CT scan revealed a bone spur on the patient’s first metatarsal head. If the doctor had done a normal release, the spur may have ended up pinching the sesamoid. Instead, he performed a lateral release and excised the bone spur.