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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.

Dr. Gary Briskin: The pedCAT is the Future

“It’s the future – embrace it. It’s your future – control it.”

Dr. Briskin lectures on weight bearing CT imaging for foot 7 ankle
Dr. Briskin lectures on weight bearing CT imaging for foot 7 ankle

Dr. Gary Briskin delivered this motivating message at the Foot & Ankle Business Innovations conference in Chicago on Jan. 23.

Dr. Briskin, of University Foot & Ankle Institute in Santa Monica, Cali,  discussed how the pedCAT weight bearing CT system has improved his practice since his group acquired one last year.

His main take-away points were:

– The pedCAT gives you the advantage when it comes to diagnosing pathology.

“You can solve that Lisfranc case no one else can,” Dr. Briskin said. “It opens up the midfoot, which historically has been a problem for us.”

– The pedCAT allows him to clearly determine if bones and joints are completely fused after surgery.

“I do a lot of lapidus procedures,” Dr. Briskin said. “My concern; is this patient fused adequately to start bearing weight?” The exact level of fusion is visible with a pedCAT scan 5 – 6 weeks later, and with minimal scatter.

– Radiologists like the pedCAT images

“I think I’m getting a better CT, because it’s weight bearing and I think the quality is far superior. We get all of our CTs read by a radiologist. We have everything sent digitally. And the feedback we get is they are also impressed with the quality of the images.”

pedCAT: Optimal Visualization of Metal Implants and Hardware

hardware in midfoot1 charcot hardware


One advantage of CT imaging over MRI imaging is the ability to scan patients with metal implants. However, the CT scans may still suffer from severe artifacts that usually show up as streaks or dark, obscured areas. Although artifact reduction technologies continue to improve image quality, metal implants can still pose a major challenge to diagnosis.

Radiologists and foot and ankle specialists are routinely impressed with the pedCAT’s ability to visualize complex post-surgical cases. To schedule an in-office demo to view these cases in more detail, contact your CurveBeam sales representative today.

The pedCAT cone beam CT imaging system for the foot and ankle provides high resolution, high quality imaging, even with metal implants and hardware.


pedCAT: Visualizing the Sesamoids in a Hallux Valgus Deformity

rotated sesamoids

Dr. Robert Weinstein, DPM,  recently lectured at The International Foot & Ankle Foundation for Education and Research meeting in Maui, Hawaii, and presented an illuminating finding from his clinical practice: the pedCAT can be a useful diagnostic tool for a very common foot condition.

When it comes to Hallux Valgus, or bunions, a 3D scan could make a major difference in the surgical plan.

Valgus, by definition is a three-dimensional problem, since there is a rotational component, Dr. Weinstein explained.

And “sesamoids, in my mind, drive the whole deformity,” Dr. Weinstein said. “You have to be able to look at them very carefully.”

However, the standard positioning for the “sesamoid view” on plain X-Ray places the patient in an abnormal position, and therefore is not clinically relevant, he added.

“Sesamoid condition is just as important as sesamoid position,” Dr. Weinstein said. “If I see sesamoids that are diseased, it doesn’t matter how good I am at reconstructing those MPJs, that I can get that metatarsal back to zero or two degrees, it’s going to be a failure. So it’s very important to look at the crista and the condition of each of those sesamoids.”

Dr. Weinstein practices at the Ankle & Foot Centers of Georgia.

Dr. Matthew Welck, MD, FRCS, of the Royal National Orthopedic Hospital in London, presented on a similar topic at the AOFAS/IFFAS Annual Meeting in Chicago in a lecture titled, “The Metatarsosesamoid ‘The Empty Crista Sign’ – Could This be a Predictor of Deformity Recurrance after Hallux Valgus Surgery?”

Case Study: pedCAT vs. Radiographs

Surgeons often make assumptions based upon plain radiographs.  But plain radiographs often hide or distort significant radiographic findings due to bony superimposition.

Take, for example, the case below:

A patient sought  a second opinion for the cause of her medial foot and ankle pain.  The treating physician used plain radiographs to diagnose her with posterior tibial tendon dysfunction/partial tear and degenerative joint disease of the 1st, 2nd, and 3rd tarsometatarsal joints.  The treating physician also noted a “chip” of bone on the inside of the ankle.

The treating physician planned on performing a flat foot reconstruction, a posterior tibial tendon repair, and a tarsometatarsal joint fusion.

The physician performing the second opinion noted the patient’s discomfort over the medial ankle gutter was much more significant than over the posterior tibial tendon and the spring ligament.  The patient had minimal discomfort through the tarsometatarsal joints. The physician performing the second opinion ordered a weight bearing pedCAT study to assess the midfoot DJD and to better evaluate the midtarsal joint and ankle joint.  The pedCAT study clearly documented a degenerative process in the medial ankle gutter with a bony impingement.  On secondary exam, the majority of the symptoms arose from the medial ankle gutter.

If the flat foot reconstruction was performed as planned, the talus would have been dorsiflexed and the tibio-talar impingement would have been worsened.  The pedCAT images helped prevent an un-necessary surgery, while directing the physician to the appropriate pathology.

tibio talar impingement
The patient was prescribed a pedCAT diagnostic weight bearing CT scan when the patient sought a second opinion.

To learn how more about how the pedCAT could benefit your patients, contact CurveBeam today.

pedCAT CubeVue: Automatic X-Ray Views

CurveBeam pedCAT Weight Bearing CT

It takes less than a minute to scan a patient in the pedCAT, but that’s enough time for the pedCAT system to collect enough data to create a 3D reconstruction of the foot and ankle, as well as .3 mm slices in all three planes.

COMING SOON: A new feature will let you take that data one step further – pedCAT’s CubeVue software will automatically generate the data into common X-Ray views, including the Saltzman hindfoot view, the dorsoplantar view, and left and right lateral views.

The automatic X-Ray view feature will save the physicians valuable time when analyzing their patient data.

To learn more about this and other CubeVue features,  contact your CurveBeam representative!

Distinguishing Categories of Medial Column Ligamentous Fracture

Weight bearing CT scans offer new, three-dimensional perspectives that reveal a better understanding of the biomechanics of flat foot. That was a finding on an academic poster on display at The American Orthotic and Prosthetic Association’s National Assembly in Las Vegas (Sept. 4 – 9).

“IRD, PTTD, Posterior Tib, Flat Foot, Pronation…these are all terms that various professions use to describe some sort of medial column ligamentous breakdown,” according to the poster. “The purpose of this study is to better distinguish some types of pathomechanics of the foot. By categorizing and redefining them, it makes the description of pathology more useful for Orthotic Treatment. This was possible through the use of 3D rendering of the pedCAT machine and CurveBeam software.”

The study was conducted by Ian Engelman, M.S. CPO, and Harold Chamberlin, DPM. They looked at 3D renderings of the bony structures in flat feet, and came up with some new descriptions, as well as their possible ligamentous causes.

For example:

Lisfranc Breakdown
Lisfranc Breakdown – Tarsometatarsal Ligamentous Failure
Lateral Foot Dislocation - Deltoid Ligament Fracture
Lateral Foot Dislocation – Deltoid Ligament Fracture











The study concluded that while the exterior contours of the foot suggest certain bony pathologies, the 3D renderings provided by the pedCAT would allow for orthotists to better distinguish the pathomechanics of the foot and ankle.

An unexpected result showed a moderately strong correlation (-0.68) between the vertical position of the navicular and medial displacement in a patient population with ranging degrees of medial column breakdown.

Moderately strong correlation of -0.68
Moderately strong correlation of -0.68






pedCAT: Weight Bearing CT Views of Lisfranc conditions

Lisfranc injuries can easily be missed on traditional radiographs.

One research study tried to determine the level of accuracy when using plain radiographs to assess midfoot conditions. Their results confirmed a high incidence of missed diagnosis even by experienced observers.¹

“Radiographic evaluation is crucial in the diagnosis…Weight bearing views are more sensitive since tarso-metatarsal instability may be revealed…The threshold for cross sectional imaging such as multi-detector CT should be low,” according to the study.

With the pedCAT, it is possible to get a weight bearing, three dimensional scan at the point of care. The tarso-metatarsal joint can be viewed without any superimposition from surrounding anatomy.

Delaying a 3D scan can be detrimental to recovery.

“The identification of Lisfranc joint injury can be difficult and is often not detected on initial presentation to the accident department. This is important because of the correlation between delay in treatment, particularly more than six months, and poor functional outcome,” the study reported.

Midfoot dislocation, fracture, pedCAT

In this pedCAT scan, the 3D rendering shows the 2nd metatarsal is pushing on the 3rd metatarsal. The multi-planar slices reveal the fracture that is causing the dislocation. The sagittal and axial slices show a bone fragment as well. It would be impossible to see this information on a plain radiograph.

lisfranc AP

This pedCAT scan clearly depicts the gap between the first and second metatarsals.

¹ Sherief, Tamer. “Lisfranc injury: How frequently does it get missed? And how can we improve?” International Journal of the Care of the Injured. Elsevier Ltd. 10.106/j.injury.2006.10.002

Webinar: Dr. Erik Nilssen – A New Paradigm in Foot & Ankle Diagnosis

FAI webinar

“Patients come to my practice with an expectation of a higher level of care, that they’re getting the best. With the pedCAT, I am able to give them information immediately, and they leave feeling this was well worth the trip.” – Dr. Erik Nilssen

Learn how the pedCAT has changed Dr. Nilssen’s clinical practice in a webinar hosted by Foot & Ankle International and Foot & Ankle Specialist.

We hope you can join us! Sign up here.

CurveBeam Reception at AOFAS: You’re Invited!

If you’re attending the AOFAS/IFFAS Annual Meeting 2014 in Chicago from September 19 – 23, be sure to plan to attend the CurveBeam reception on September 21 at 7:30 p.m.

Sip cocktails and dine on hors d’oeuvres while mingling with colleagues who have integrated the pedCAT into their practices. Meet like-minded forward thinking peers who are considering a pedCAT acquisition at their facilities.

This informal event will feature brief talks by Prof. Dr. med. Martinus Richter, who has published studies on the pedCAT’s efficacy, as well as Dr. Erik Nilssen, MD and Dr. Martin O’Malley, MD.

When: Sept. 21, 7: 30 p.m.

Where: Hyatt Regency Wrigley’s Room (Bronze Level, West Tower)

If you can’t attend the seminar, you can visit us at booth #307 all conference long.