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.
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.
Gaining an accurate and complete measurement of the hindfoot alignment of a patient with adult acquired flatfoot deformity (AAFD) is difficult when using traditional clinical assessment. In a paper published in the journal Foot and Ankle Surgery, Dr. Cesar de Cesar Netto, MD, PhD, and his colleagues posit that weight-bearing cone beam computed tomography (CBCT) scanning technology may give a more complete, three-dimensional view of the deformity and its underlying causes.
In the article, “Hindfoot Alignment of Adult Acquired Flatfoot Deformity,” the team studied twenty patients with AAFD, twelve men and eight women. All participants had to undergo a clinical assessment of their hindfoot alignment and got a weight-bearing CBCT scan. After all tests were completed, the team found that the weight-bearing CBCT scans provided far more accurate, reliable and repeatable measurements than those of the clinical assessments, thus making a strong case for the use of cone beam technology in AAFD diagnosis and treatment.
In the video below, Dr. de Cesar Netto describes how WBCT assists in AAFD evaluation. “We have been finding really interesting things while studying the flat foot deformities in the weight bearing CT images, most of them related to coronal plane assessment. But it’s not just that,” Dr. Cesar de Netto says. “We are trying to use the three dimensional environment to find out how the deformity progresses.”
The problem with current practices, according to de Cesar Netto and his colleagues, is that they rely on two systems that make it difficult to obtain universally accepted results. The first is radiographic examinations. These are two-dimensional and cumbersome, with further difficulty added when trying to discern hindfoot alignment due to the complexity of the subtalar joint. Not only that, but these examinations are especially prone to improper positioning which would throw off the results. The other traditional system used for hindfoot alignment measurement is made up of a series of clinical measurements including simple visual evaluation. These measurements have consistently been shown to be inaccurate and highly variable from physician to physician.
Recent advancements in CBCT technology now allow physicians to obtain a three-dimensional, highly detailed view of a patient’s lower extremities. They also allow for a complete picture of both the soft-tissue and bone within the foot, so that no issues go overlooked. Of particular interest to the study at hand was the fact that CBCT allows for scans to be taken of the foot in a natural, weight-bearing state. As AFFD is highly dynamic, analysis of the condition with the effects of a patient’s full body weight can be immensely beneficial when developing a treatment plan.
Leading the way with weight-bearing cone beam technology is CurveBeam. The CurveBeam LineUP is revolutionizing how physicians approach diagnosis and treatment plan development as their technology provides complete views of the lower extremities with high image quality.
A study published in the International Journal of Biomedicine concludes Cone Beam CT (CBCT) imaging is the “method of choice” for compound anatomical structures, such as the wrist, and post-traumatic changes in bone tissue.
“Considering the low dose radiation and high image quality,” CBCT could be used as a priority method of choice to assess the structure of wrist and hand bones and be done as a first step in diagnostics, replacing standard radiography,” according to the study, which was led by A. Yu Vasiliev PhD, MD, at Moscow State University of Medicine and Dentistry.
The wrist and hand are one of the regions in the human body most prone to injury and disease. Only one-fifth of incapacitation is the direct result of injury or disease. Many cases of incapacitation are instead due to mistakes made in diagnosis and treatment, according the study. Vasiliev and his team examined the capabilities of cone-beam computed tomography (CBCT) in the assessment of the structure of wrist and hand bones.
The study appeared in a 2013 issue of the International Journal of Biomedicine.
Vasiliev obtained a Cone-beam CT scan of the wrist and hand of a group of voluntary patients, which included 40 members aged 22 – 68 years. A Magnetic resonance imaging (МRI) exam was also performed on 80 percent of the volunteers, multi-slice CT scan was performed on 40 percent of the volunteers, and digital microfocus radiography and standard radiography exams were performed on 63 percent of the volunteers.
When all 40 CBCT scans were examined, structural changes of wrist and hand bones were detected in 77.5 percent of cases, and consolidated fractures and false joints of bones were detected in 10 percent of cases. All the changes were also detected by the multi-slice CT images and digital microfocus X-Rays, but were not defined on standard X-Rays.
The results demonstrated that CBCT provides high efficiency in detection of form, measurements and structural changes of bones of the anatomic region. The cone beam CT images of wrists and hands provided high-resolution, detailed mapping of bone structure, as well as accurate differentiation of bone trabeculae and minor structural changes and defects.
A new generation of cone-beam scanners makes it possible to obtain high-quality images without exposing the patient to a high dose of radiation. This facilitates more and better examinations in orthopedics and traumatology for better patient outcomes.
CurveBeam designs and manufactures Cone Beam CT imaging equipment for the orthopedic and podiatric specialties. To access the full study, please click here.
The team knew that the ability to assess OA with 2D radiographs was not good enough to detect subtle changes that could have important implications for patients, doctors, and researchers. To meet this challenge, they worked to develop a new algorithm for the structural assessment of joints including hips, knees and ankles in 3D. Their recent technical validation study showed the technique was successful.
The algorithm maps joint space width to the nearest tenth of a millimeter. Mapping joint space width in 3D from clinical CT data has the potential to enhance understanding of osteoarthritis and how patients progress to joint failure—leading to better and earlier interventions.
Early Detection Gives Osteoarthritis Patients More Options
The 3D mapping technique has the potential to be more than twice as sensitive as radiographs in detecting small changes in joint space widths. Using the algorithm, clinicians will be able to use CT scans to map a marker of osteoarthritis across a joint. Why does it matter? Because early detection leads to earlier treatment. Doctors could identify patients with disease earlier than the current gold standard, allowing important interventions to be started before the joint fails. Patients will have the opportunity to try lifestyle changes and physiotherapy instead of immediately facing surgery.
All clinical CT imaging was performed on a 64-slice Siemens Definition AS system.
“It will be an important next step to use JSM to investigate whether differences in positioning and load-bearing have any effect on joint space width in 3D,” the authors wrote. “A straightforward solution for prospective studies would be to perform knee and ankle CT in a standing position (as used in clinical practice), and to standardise supine hip positioning by strapping feet together.”
Evaluating New Therapies
In addition, the new 3D method will likely allow researchers to determine whether new therapies in development are effective in a realistic timescale for clinical trials. This is something that has not been possible using radiographs.
CurveBeam designs and manufactures Cone Beam CT imaging equipment for the orthopedic and podiatric specialties. Bilateral, weight bearing scans of the foot and ankle give physicians the information necessary to assess the biomechanical spatial relationships and alignment of the lower extremities.
To learn about a recent grant awarded to the University of Kansas to study joint space biomarkers via weight bearing CT, click here.
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.
Foot and Ankle Specialist (FAS), a bi-monthly journal for orthopedic surgeons and podiatrists, recently published a roundtable discussion focused on providing insight into the difficult process of deformity correction. For surgeons dealing with the lower extremities, even the central principles of understanding and treating deformities can be extremely complex. Noman Siddiqui, Guido Laporta and John Herzenberg, all of whom carry numerous distinctions in the field of podiatry, all weighed in on the discussion.
Deformity management in cases involving the lower limb can involve high levels of pain. Because of this, while analysis is fairly similar to deformity analysis in other regions of the body, treatment is as much an art as a science. Much of the discussion involves presentation of cases and remarks by the specialists as to how they would care for the patient.
The roundtable ranges from topics on improving education in the field to proper care of patients who are treated with external fixation. Of particular interest is the repeated insistence by the panel that the most essential way to improve the field is to increase the amount of information available to a surgeon before an operation occurs. They remark that, even though patients receive a thorough physical as well as a biomechanical exam, gait analysis, and functional testing, more extensive testing and imaging is needed.
All three of the medical experts point out the need for a computed tomography (CT) scan for the more difficult cases. These scans help to erase any gray areas in the diagnosis and help to evaluate the “mal-union” or “non-union” present in malformed feet and ankles. Dr. Herzenberg even recommended 3D CT technology in order to get a complete picture of the situation, and both a weight and non-weight bearing evaluation.
“[Foot] deformity is complex and may require second-level radiographic studies such as a CT scan,” remarked Herzenberg. “Recently, we have added a standing 3D CT machine in our office, which offers the same advantage from a CT standpoint that we get from plain films taken weight bearing versus non–weight bearing.”
These orthopedic specialists are not alone in their desire for more comprehensive scanning technology when treating deformities. More and more clinics are taking similar steps to those used by Herzenberg’s clinic, The Pediatric Orthopedics Department at Sinai Hospital in Baltimore, which now uses the CurveBeam pedCAT. It is quick, efficient and thorough, and was designed with patients in mind, limiting their discomfort. This is especially important since, as mentioned earlier in the roundtable, pain can be significant when dealing with foot and ankle deformities.
The discussion presents a comprehensive look at the current practices in a complex corner of healthcare, and presents insights into the best way to manage orthopedic deformities in the lower extremities. The specialists involved even go so far as to give advice for those preparing to deal with these cases, and examine current technology that allows them to do so to the best of their ability. To read the roundtable discussion in its entirety, click here.
A new study, led by famous Belgian M.D. A. Burssens, emerged in the February issue of Foot and Ankle Surgery. The study examines the use of traditional hindfoot angle measurements versus weight bearing CT and shows how weight bearing CT can help contribute to the pre-operative planning by providing further insights into a physiological hindfoot alignment.
Hindfoot malalignment is a widely-accepted cause of foot and ankle disability and problems. For preoperative planning and clinical follow-up, reliable radiographic assessment of hindfoot alignment is of utmost importance and can affect future health. The long axial radiographic view and the hindfoot alignment view are commonly used for this purpose. The main goal of this study is to obtain measurements from a population with clinical and radiological absence of hindfoot pathology. These values were then compared to hindfoot measurements obtained from the long axial view based on the anatomical axis of the tibia and the calcaneal axis, to point out possible differences attributed to that measurement method.
The study has many key findings related to traditional hindfoot predictive measurements. One major finding questions the commonly held belief that non-symptomatic feet have a slight valgus. When traditional hindfoot angle measurements were applied, the study showed that non-symptomatic feet have a neutral alignment. These results show a more neutral alignment of the hindfoot as opposed to the generally accepted constitutional valgus.
Another major finding was that the weight bearing CT clearly showed the talus. The talus is usually superimposed in plain x-rays and hard to see and can affect the mathematical calculations of the predicted hindfoot angle. So, unlike the Saltzman view, these calculations included the talus.
The ultimate goal of all orthopedic surgeons is to influence the correct alignment of bones. Even the slightest miscalculation in measurement can have lasting consequences on post-surgery recovery and future mobility. As the study notes, “Although surgical hindfoot corrections are frequently performed either extra-articular by osteotomies or intra-articular by arthrodesis, still numerous debate exists on the amount of correction and the ideal foot position after arthrodesis.” This finding could have repercussions on hindfoot position during fusion or in quantifying the correction of a malalignment. Due to the use of weight bearing CT, the inferior calcaneus point can be used during pre-operative planning of a hindfoot correction as an anatomical landmark due to its shown influence on load transfer.
A disadvantage of the study was that it was not truly spatial, as only the coronal plane was used in measurements. In the future, 3D segmentation models will allow for better spatial calculations. Until 3D weight bearing CT is an available option, it is recommended foot & ankle specialists exercise caution when planning from 2D radiographs. This study will contribute to the pre-operative planning by providing further insights into a physiological hindfoot alignment. For more detail, access the article here.
Cone beam computed topography (CBCT) systems are becoming popular with orthopedists and podiatrists because they quickly provide high-quality, low-dose, 3D imaging of musculoskeletal conditions. Dentists and podiatrists have been using CBCT technology for years, but the pedCAT by CurveBeam is designed specifically for extremities: especially knees, ankles, and feet. This compact, affordable unit gives specialists bilateral, weight-bearing 3D views of the foot and ankle, allowing physicians to create comprehensive treatment plans. In a Radiology Today article titled “Imaging in the Extremities,” Beth W. Orenstein, a freelance medical writer, examines this new technology.
There are a number of advantages to these new compact CBCT units. First, they have a larger area detector by which to image the patient in a single rotation, rather than taking many slices as with a tradition CT scanner. This feature eases system operation and reduces scan time. The pedCAT, for example, scans a patient in about one minute. Second, CBCT units can be located outside radiology departments, since they typically don’t require a lead-lined room or a special power source. Third, providers will find that CBCT positively impacts their practice, with improved diagnostic capabilities, streamlined workflow, and greater productivity. Finally, patients benefit with an easy-access unit that provides same-day results from a single brief visit.
CBCT provides other benefits to orthopedists and podiatrists, as well, such as the ability to produce load-bearing images. Load-bearing images of extremities, such as feet and ankles, may reveal alignment abnormalities that a conventional CT scan might miss. And CBCT offers improved spatial resolution over other methods, such as traditional CT scans or X-rays. One of the biggest benefits, though, is the transmission of a far smaller radiation dose. The tube current on a conventional CT scan typically ranges between 50 mA and 300 mA, and even an ultralow-dose setting would be between 20 mA and 60 mA. CurveBeam’s pedCAT, by contrast, has a fixed tube current of just 3mA, and the patient is exposed to 2 to 5 micro Sieverts per scan—less than the average background radiation a U.S. resident experiences daily.
Of course, there are also several challenges in adopting CPCT technology. For example, since CBCT uses a completely different image acquisition technology, comparing scans with conventional CT is difficult. The lack of dose and image quality assessment standards for CBCT limits accreditation. And since a unit like the pedCAT automatically generates all standard X-Ray views in addition to the full CT volume, many orthopedists and podiatrists feel they can interpret the images themselves in-house. In fact, some radiologists fear that point-of-care units could negatively impact their role as specialists. But other radiologists argue that the sophistication required in interpreting CT scan results will keep their expert services in demand.
In the future, CBCT units may even be used in emergency departments, as well, since the unit takes up so little space. The pedCAT’s footprint, for example, is about four feet by five feet. This means a CPCT scanner could be easily relocated where needed since it is relatively lightweight and mobile.
Recent work by Dr. Neil H. Segal examined the potential of a low-dose standing CT scan for evaluating changes in tibiofemoral joint space of patients suffering from knee osteoarthritis.
The results of Dr. Segal’s study were recently published in the medical journal Skeletal Radiology and reveal that when taken two weeks apart, standing CT images are even more reliable than plain radiographs. The insightful, 3-D, information-packed images suggest that the modified foot/ankle scanner by CurveBeam used to capture the data may soon become a valuable tool for doctors to evaluate and track the disease’s progression, as well as for researchers wanting to study it.
Measurements of the tibiofemoral joint space were obtained from two bilateral fixed-flexed standing CT images taken two weeks apart, utilizing a modified version of a CurveBeam scanner more commonly used to capture images of the foot and ankle. Participants were exposed to an extremely low dose of effective radiation, O.2 mSv – no more than the average person is typically exposed to from the natural environment itself in any two-week period.
The main purpose of the study was to determine whether or not standing CT scans might be a viable alternative to plain radiographs for studying patients’ knee osteoarthritis – and how reliable such scans might be. Thirty people with a range of osteoarthritis features took part, and the Institutional Review Board approved all aspects of the study.
The results suggest the data obtained is extremely reliable. Moreover, the 3D imaging of both the tibiofemoral and patellofemoral joints the standing CT scanner produces offers a wealth of enhanced information for doctors and researchers to draw upon.
All this, the study shows, without a clinically significant increase in either acquisition time or radiation dose.
Dr. Segal’s work comes as a response, in part, to the difficulties and challenges in acquiring meaningful, reliable tibiofemoral joint space measurements using traditional radiographs.
Past studies have shown that the replication of measurements has been poor, with limited information obtained. More aggravating still is the fact that months if not years are usually required between radiographs before any change in the patient’s condition can be detected. An efficient, accurate, time-saving alternative has long been needed.
The modified CurveBeam scanner, by contrast, has the potential to address these challenges. As evidence from the study showed, the standing scanner provided exceptionally reliable images with insignificant doses of radiation emitted.
The next step will be to assess the responsiveness of the standing CT scanner to changes in the tibiofemoral joint over time. If effective, the protocol will no doubt become an invaluable tool for doctors and researchers alike in their work to combat the ravages of knee osteoarthritis and related ailments.