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pedCAT: Early Diagnosis of Osteomyelitis in the Diabetic Patient

The pedCAT weight bearing CT imaging system could identify bone infection at an early stage, and possibly prevent amputations, researchers at the California School of Podiatric Medicine at Samuel Merritt University determined in a report.

The researchers outlined two cases where “the use of CBCT device enabled us to diagnose and treat osteomyelitis in a timely manner, preventing its spread to adjacent bone and soft tissue, and minimizing the amount of required surgical resection.”

Plain radiograph is the primary imaging modality for the osteomyelitis diagnosis, the report states, but X-Rays may not reveal osteolytic changes for up to 20 days from the onset of infection or until the bone density is reduced by 30 – 50 percent.

Osteomyelitis is one of the most feared complications of diabetic foot ulceration, which often leads to lower extremity amputation and disability. Early diagnosis of osteomyelitis increases the likelihood of successful treatment and preserving ambulatory function. Unfortunately, most of the currently available imaging modalities are of limited use in assessing early stages of bone infection due to their low specificity and sensitivity for early osteolytic changes.

Magnetic resonance imaging (MRI) is more sensitive and specific than X-Ray, and yields greater accuracy in detecting soft tissue abscesses or early osteomyelitis in patients with high clinical suspicion and negative radiographs. In controversial or uncertain cases where MRI is not available, other imaging techniques such as indium-labeled leukocyte imaging combined with radionucleotide bone scan can be used as an alternative. (“Preventive and Therapeutic Strategies for Diabetic Foot Ulcers” – Foot & Ankle International® 2016, Vol. 37(3) 334– 343 – Chris C. Cychosz, BS, Phinit Phisitkul, MD, Daniel A. Belatti, BS, and Dane K. Wukich, MD).

Nuclear Imaging and MRI perform well in detecting early onset of osteomyelitis; but they are expensive to own and operate, are time-consuming in their acquisition of images.

What is desirable for early detection is a method that is accurate, inexpensive, and readily available. Cone beam CT, and the pedCAT in particular, fills this gap nicely.  The device is small enough to fit into most practices, offers high-resolution 3D imaging capabilities, and has a reduced radiation dose compared to traditional CT, according to the report.

Lead author Alexander M. Reyzelman, DPM,  and his associates reported on two diabetic patients who presented with infected neuropathic foot ulcers and were evaluated for potential osteomyelitis using plain film radiographs and the pedCAT CBCT scanner. In both cases, the “pedCAT was instrumental in identifying bone infection. The diagnosis of osteomyelitis was later confirmed by positive findings on bone biopsy. The use of CBCT device enabled us to diagnose and treat osteomyelitis in a timely manner, preventing its spread to adjacent bone and soft tissue, and minimizing the amount of required surgical resection.”

Case 1

A 49 year old diabetic female presented with an infected neuropathic ulcer at the lateral aspect of her fourth digit. The ulcer demonstrated malodor, cellulitis that extended to fourth metatarsophalangeal joint and positive probe-to-bone test. The plain film radiographs and CBCT were utilized in order to rule out osteomyelitis and assess the extent of soft tissue infection. The weight-bearing X-rays of the affected foot revealed subtle lucency at the lateral aspect of the proximal phalanx of the fourth digit, which was contiguous with the ulcer location. However, this finding alone was not sufficient to yield a conclusive diagnosis.  The images obtained using PedCAT clearly demonstrated the break in the cortex and the area of osteolysis involving the proximal phalanx of the fourth digit. The head of the fourth metatarsal and adjacent digits appeared intact. These findings, in conjunction with the clinical appearance of the affected digit, led to a preliminary diagnosis of osteomyelitis. The patient was treated with an arthroplasty of the fourth proximal interphalangeal joint, and has fully recovered. The bone specimens obtained intraoperatively were sent for biopsy, which confirmed our preliminary diagnosis of osteomyelitis.

Case 2

A 53 year old diabetic male presented with an infected neuropathic ulcer at his fifth metatarsal head, which exhibited malodor, edema and erythema extending through tthe plantar lateral aspect of  fifth metatarsal shaft and probed to joint capsule. The X-rays demonstrated no signs of bone involvement, while CBCT revealed distinct areas of cortical lysis and bony fragmentation of the fifth metatarsal head. The proximal two thirds of the shaft of the fifth metatarsal appeared unaffected, with intact cortex, uniform bony density and lack of osseous fragmentation. The patient was treated with partial resection of the fifth metatarsal. The bone biopsy has confirmed our preliminary diagnosis of osteomyelitis.

In the concluding discussion, Dr Reyzelman noted: “Though in our case studies we have not taken advantage of the option allowing to scan the patient in both, a weight-bearing and a non-weight bearing positions, this option could be highly useful for evaluation of complex fractures and dislocations of the foot and ankle.”

Orientation of the Subtalar Joint: Measurement and Reliability Using Weight Bearing CT Scans

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.

Panel Recap: Dr. Michael Chin, DPM, Speaks about pedCAT at FABI

Dr. Michael Chin, DPM, and Arun Singh, President & CEO of CurveBeam
Dr. Michael Chin, DPM, and Arun Singh, President & CEO of CurveBeam

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. Michael Chin, DPM, at FABI

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.

Webinar Recap: “Using Weight Bearing CT to Guide Clinical Decisions”

Dr. Steven K Neufeld, MD, presented “Using Weight Bearing CT to Guide Clinical Decisions” on FOOTInnovate™  in late 2015. In one of his opening statements, Dr. Neufeld described why he decided to give the webcast: “This talk was put together really out of my enthusiasm and excitement and interest in this technology.”

The pedCAT saves time

“… (It’s) quicker for me to get a cat scan in my office, and show the results to my patient,” Dr. Neufeld said.  By the time the patient leaves the X-Ray room and gets back to the exam room, the images are ready.

Also, it helps streamline his pre-op planning. “I don’t have to send the patient to the hospital for a CT. I don’t have to schedule another appointment to review the results,” he said. “All the information is right there. It also saves the patient money. The cost of a CT scan in my office is much less than a big hospital or institution.”

Immediate feedback to the patient also helps put the patient at ease. “The patient feels comfortable with me, that I have a plan and that I know what we were going to do, and I go in there and I execute it,” Dr. Neufeld said.

The in-office workflow has improved accuracy and consistency in imaging for him as well, “Instead of getting a standard Saltzman or heel view … the weight bearing CT scan is much easier for the technician,” he said. “You don’t have to position the foot in any particular way, you don’t have to angle your beam in a particular way. You just have them stand on the machine and you then push the button, and you can determine alignment very easily.”

The pedCAT aids in definitive diagnosis and evaluation

In his webcast, Dr Neufeld proposed the following: “Based on our knowledge, it’s pretty much understood that the standard of care for any Orthopaedic foot and ankle or Podiatric evaluation of a foot and ankle problem is a weight-bearing radiograph – at least currently. The big question again is: does this X-Ray give enough?”

When it comes to alignment, weight-bearing is deemed necessary to properly evaluate the ankle under load. This is especially true when superimposition of structures does not allow you to properly determine position, rotation, translation, and joint space. In the case shown below, only weight-bearing CT allows you to see the impingement in the subtalar region; a 2D x-ray would not allow you to properly evaluate the joint spaces.



A Total Ankle Replacement (TAR) is another surgical procedure where weight-bearing CT is a must, according to Dr Neufeld. “A non weight-bearing CT scan would really not give me information about the implant position… (The PedCAT is) a great modality for post-op,” he said. The convenience of having 3D imaging on hand for follow-up exams, even if they are non-weight-bearing, makes it easier to follow the progress of healing post-op. Failed hardware and non-unions are more readily diagnosed this way.

Dr Neufeld also regularly prescribes weight-bearing CT scans for unknown pain. “The other way that I use weight-bearing CT scan is … sometimes a patient comes in the office, and they just hurt! And you just can’t figure it out!” he said. “You know – X-Rays are normal, the exam is very vague … we’re all faced with this patient. You just can’t figure out what is going on sometimes.”

Other uses for his weight-bearing CT include Lisfanc, navicular & other hard to evaluate fractures, sesamoid problems (especially when coupled with Metatarsalgia), and arthritis. The fact that you can scan a foot in a shoe with an Orthotic also makes it easier to determine if the Orthotic is accomplishing what it is supposed to do, as shown in the image below.


An investment worth the regulatory hurdles

Dr Neufeld, Director of the Orthopedic Foot and Ankle Center in Falls Church, Virginia, began using his pedCAT in August of 2015. The state of Virginia requires medical facilities to obtain a Certificate of Need to purchase CT systems. The approval process can be challenging. However, Dr Neufeld was both persistent and patient in his determination to bring the new weight-bearing technology into his office.

“It is brand new,” he said. “There is nothing like it out there in the state. If you can prove and show that this technology is different than what they have out there- you’re not competing with the hospitals, you are not competing with the radiology centers – and that it is unique and essential for your practice, then you can put up a fight. And if you have perseverance and some patience, you can get it, and that’s what we did.”

So why persist? Dr Neufeld’s answerer is simple.“The PedCAT has been a game-changer for my practice and one of the best investments,” he said. “It has really become a crucial part of my practice, and I would say it’s probably one of the most profitable, influential investments in modalities that I’ve added.”

Weight Bearing CT Imaging for Cuboid Subluxations

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.

pedCAT scan of a pre-surgical patient with cuboid subluxation. Dr. Chin was able to reduce the subluxation to 2.18 mm.

Dr. Chin practices at The Running Institute in Chicago.

AOFAS Annual Meeting – CurveBeam Symposium Recap

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.

Vertical Talus - Weight Bearing CT
Vertical Talus – Weight Bearing CT
Impingement - weight bearing CT
Impingement – weight bearing CT

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.

Calcaneal-fibular impingement and arthritis - Weight Bearing CT
Calcaneal-fibular impingement and arthritis – Weight Bearing CT

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.

1st MT Bone Spur - Weight Bearing CT
1st MT Bone Spur – Weight Bearing CT





pedCAT: A Positive User Experience


Baravarian Western

“After using the pedCAT for a year, I am very impressed with how much I need it, and how many different things I use it for,” Dr. Bob Baravarian said at the 2015 Western Foot and Ankle Conference held in Anaheim, Cali. The California Podiatric Medical Association hosted the meeting at the end of June.

Dr. Baravarian cited Hallux Rigidus as one example where pedCAT imaging has been helpful because he is able to properly assess the sesamoids.

Dr. Baravarian confirmed his practice is realizing positive revenue streams as a result of the device.

Diagnostic Options for Freiberg’s Avascular Necrosis

The underlying causes of avascular necrosis of the second metatarsal head are not totally understood, but early diagnosis is essential. Delayed treatment can result in a collapse of the articular surface, making treatment more difficult.

Dr. Bob Baravarian, DPM, explained his preferred methods for diagnosing the condition in the May 2015 issue of Podiatry Today.

An X-Ray will show the overall contour and alignment of the metatarsal head.

MRI is one option for a secondary study, but edema and swelling can limit visualization of the surrounding bone region, Dr. Baravarian explained.

Weight bearing CT scans, meanwhile, clearly show the bones and joints and how they are aligned. Weight bearing CT is “our go-to imaging study,” Dr. Baravarian said in the article.

Source: Podiatry Today
Source: Podiatry Today
Source: Podiatry Today
Source: Podiatry Today

“With adequate diagnostic testing and proper patient and procedure selection, one can treat avascular necrosis of the metatarsal head with good to excellent outcomes,” Dr. Baravarian said.

Dr. Baravarian is the director of University Foot and Ankle Institute in Los Angeles. His practice offers weight bearing CT imaging services.

Weight Bearing CT in Everyday Practice

“In my opinion, weight bearing CT will be the standard of care in the next couple of years,” Dr. Alex Tievsky, DPM, said in a lecture at the Graham International Implant Institute 8th Annual Symposium in Miami, on April 17. “This is really the future of not just foot and ankle, but the future of medicine.”

“2D is beginning to be phased out,” Tievsky said. “Now we’re beginning to see the problem from all angles and all planes, so this is super helpful from that respect.”

Dr. Tievsky presented a number of cases where he benefited from access to weight bearing 3D technology in his office.

Clinical Case #1

A 50-year-old female presented with bilateral flat feet for 20 years. She had heard about the HyProCure procedure, which corrects hindfoot misalignment through a minimally invasive procedure. She was eager to have the procedure done, no matter the cost. Dr. Tievsky took a pedCAT scan, and found she had a severe talar coalition.

talar calc coalition coronal left

“How many times do you catch a coalition on an X-Ray? It’s hard,” Dr. Tievsky said. “Sometimes you can see a halo sign, but it’s often missed. On the first visit, I was able to tell her, we either have to resect this coalition or we have to do a fusion. It’s impossible to get this level of information on an X-Ray.”

Clinical Case #2

A 16-year old girl came in with first metatarsal head pain. She had already been to two other podiatrists in the last six months, and they had prescribed steroid injections.

The pedCAT revealed a fracture on her fibular sesamoid that is extremely easy to miss on X-Ray.

fractured sesamoid

“Within her first 10 minutes in the office, we had a diagnosis,” Dr. Tievsky said. “We treated her appropriately. We immobilized her for eight weeks and gave her a bone stimulator. And she was pain free, three podiatrists later. She was happy, her mom was happy, and she never came back.”

Clinical Case #3

A patient presented with a lateral plantar fasciitis, a talo-tarsal dislocation, back pain for five years, knee pain, and hip pain.

A pedCAT revealed she had a tumor in her bone and it was eroding it. “There was no way we would have caught it on X-Ray,” Dr. Tievsky said. “We sent her out for oncology. It could have a malignant tumor, and we could have saved her life.”

Cyst Coronal

The scan is quick to take and you have a full work-up in about three minutes, Dr. Tievsky said as a closing statement. “This is a super important tool,” he said. “I’m kind of biased. I love this now. I can’t practice without it.”

Weight Bearing CT Scans for the Evaluation of Implant Arthroplasty Candidates

Weight bearing CT scans can be critical to a proper diagnosis, even for routine procedures.

In the following case, for example, a patient’s X-Rays indicated that he would be a good candidate for a metatarsal head hemi-implant arthroplasty. However, when the patient sought a second opinion, a weight bearing CT (pedCAT) scan revealed the true condition of the metatarsal head, and the surgical plan was considerably altered as a result.

A 60 year-old male presented complaining of a many year history of 2nd metatarsophalangeal joint pain, especially joint stiffness and pain. His pain increased with attempted 2nd MTPJ dorsiflexion.  In gait, he felt pain when rolling onto the ball of the foot.  His first surgical opinion recommended a metatarsal head hemi-implant arthroplasty .

Due to the excessive bony superimposition on the patient’s lateral X-Ray, it is difficult to accurately assess the shape of the 2nd metatarsal head.  A bone fragment can be visualized over the dorsum of the first or second metatarsal heads.  The AP weight bearing images demonstrate 2nd metatarsophalangeal  joint space narrowing.

Implant Arthroplasty Candidate X-Ray X-Ray 2

The patient sought a second opinion from a podiatric surgeon who offers in-office weight bearing CT services. The podiatrist performed a pedCAT scan and found the 2nd metatarsal head had sustained an old fracture. The pedCAT scan revealed that the dorsal 50% of the 2nd metatarsal head had been avulsed dorsally and a portion of the metatarsal head presented as a dorsal loose body.  The 2nd metatarsal head didn’t have the bone stock or bone volume to support a hemi-implant. The second opinion recommended recontouring the metatarsal head and performing an interpositional arthroplasty. The patient chose to have the second surgeon perform his surgery.

fractured 2nd MT head pedCAT weight bearing CT

A CT scan is not typically ordered to evaluate feet preoperatively.

“We are all trained to believe our eyes and to believe the information present in X-Ray images.  In this case it is assumed that the 2nd metatarsal head has a normal contour, length and bone volume.  The X-Rays demonstrate joint space loss and justify the hemi-implant arthroplasty, but adequate bone volume is required for implant stability and fixation. You just assume it’s going to be OK,” said Dr. Kent Feldman, DPM. “And if you do that as a routine, you’re going to get caught over and over and over in the operating room making mistakes or making assumptions that aren’t necessarily true.”

Dr. Feldman integrated a pedCAT into his surgical practice in 2012.