Research: Impact of Weight-bearing Images in Orthopaedic Imaging

Study favors weight-bearing images for orthopaedic patellofemoral diagnosis and surgery

In clinical orthopedics advanced imaging like computed axial tomography (CT) scanning, has become invaluable to the evaluation and management of patients with musculoskeletal disease. Bone detail is much better visualized with 2D and 3D CT renderings of patients with problems like glenoid fracture, failed shoulder instability surgery, and meniscal root avulsions.

Conventional CT technology requires subject in supine position

High-quality images provide multiplanar 2D and 3D visualization for practitioners who think and work in three dimensions. However, a significant limitation of CT technology has been that it forces image acquisition with the subject in a supine, relaxed position. When imaging an injured knee, for example, the leg is in full extension and the muscles relaxed.

The conventional measures of patellofemoral alignment include the congruence angle, patellar tilt angle, and tibial tubercletrochlear groove offset distance. There are clearly defined limits of normal use for each of these measures, and they are used by surgeons to plan corrective operations on the patellofemoral joint. The degree of knee flexion and activity of the quadriceps are known to influence patellar tracking on the trochlea, but these factors are removed when images are taken with the patient supine.

Some have tried to simulate weight bearing in a CT scanner by custom designing a rig to apply longitudinal  load  through  the  patient  for  imaging  of  the  spine or  lower  extremity. These  methods  are  at worst,  a  poor depiction  of  functional  anatomy;  and  at  best , a cumbersome  and a less-than-accurate simulation of function.

Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo undertake study

Myself and other researchers from the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo are currently performing research on a new  cone  beam CT scanner,  the  CARESTREAM OnSight  3D  Extremity  System,  developed by Carestream Health. The system is designed to offer high-quality, portable,  low-dose  3D  point-of­ care imaging by orthopaedic and sports medicine practices, hospitals, imaging centers, urgent care facilities, and other healthcare providers.

We have been performing institutional IRB-approved clinical trials and basic sciences studies with the prototype model. These studies are being carried out at the Erie County Medical Center, Buffalo’s regional orthopedic tertiary care facility. Based on early data, we are convinced that many imaging studies should be acquired with subjects in positions that represent true human function, such as weight bearing on the lower extremities.

Comparing Carestream OnSight 3D Extremity System to predicate devices

We compared the 2D imaging performance of the CARESTREAM OnSight 3D  Extremity System to the predicate CARESTREAM DRX-1 Detector used with the CARESTREAM DRX-Evolution System. We compared the 3D volumetric imaging performance of the OnSight system to a multiple detector computed  tomography (MDCT) scanner  (“predicate device”). The purpose of the study was to demonstrate equivalent diagnostic  image quality between the investigational and predicate devices, using a Radlex subjective quality rating scale.

The evaluation was performed on equal numbers of knees, ankles, feet, elbows, and hands from 33 cadaveric human specimens and 13 living human subjects. Four independent, board-certified radiologists of varying general reading experience performed evaluations of the images/exams captured using both the investigational and predicate devices.

Results: OnSight 3D Extremity System produced 2D images with equivalent diagnostic image quality to predicate system

In summary, the CBCT system produced 2D images with equivalent diagnostic image quality to the predicate system for a range of exams, and 3D images were rated equal or better when compared to the predicate device for a range of exams on cadaveric specimens and human subjects.

  • More than 80% of all the 2D images were rated diagnostic or exemplary, whereas approximately 98% of all 3D images were rated diagnostic or exemplary.
  • More than 75% of all Radlex rating responses counted for all 2D images were rated equivalent or favored the investigational device.
  • Approximately 85% of the Radlex rating responses counted for the 3D images were rated equivalent or favored the investigational device.

Examples of representative scans are seen below.

2D and 3D orthopaedic renderings generated by the CBCT scanner

Figure 5: 2D and 3D renderings generated by the CBCT scanner

Our conclusion from this study is that for cases of patella instability, it may be desirable to obtain images while the patient is weight bearing on a flexed knee with their quadriceps muscles active. Improvement in objective measures of patella alignment should lead to improved clinical and surgical care of patients with this condition.

New study: comparing measures of ankle stability

A second clinical study is currently under way to take advantage of the unit’s ability to obtain images in weight bearing. The research will compare measures of ankle stability from the investigational weight-bearing cone beam computed tomography scanner to the same measures on gravity stress X-ray in patients who have supination-external rotation ankle fractures.

These and future studies may validate the value of the OnSight 3D Extremity System. Potential benefits include better quality images with a lower radiation dose than conventional computed tomography. The unit is proposed for use in orthopedic offices, but it might have applications to the operating room or at athletic competition sites. The unit is less expensive than a traditional in-hospital or radiology center CT scanner, and can be used with existing electrical systems (220V). Most important however, is the potential to acquire images while bearing weight and in more functionally relevant positions.

Editor’s note: The CARESTREAM OnSight 3D Extremity System received FDA 510(k) clearance in September 2016 and is available for order in the United States.

Dr. John Marzo, UBMD

Dr. John Marzo is a physician with UBMD Orthopaedics & Sports Medicine, Associate Professor of Clinical Orthopaedics, Jacobs School  of  Medicine  and  Biomedical  Sciences,  University at Buffalo and  former  Medical  Director,  Buffalo Bills. He is also a member of Carestream’s Advisory Group, a collective of medical professionals that advises the company on healthcare IT trends.

[Q&A] Chiropractic and Diagnostic Imaging: Evolving Trends

Dr. Chad Warshal, NYCCDr. Chad Warshal is a Doctor of Chiropractic and Diplomate of the American Chiropractic Board of Radiology and teaches as an Associate Professor at New York Chiropractic College where he also serves as the Director in Diagnostic Imaging Residency. We sat down with him for our most recent edition of an Inside Look magazine to hear his views on the current role of diagnostic imaging within the Chiropractic field.

1. Let’s start by asking you about the continuing focus on evidence-based practice guidelines. Do you see this having an effect on the use of diagnostic imaging by chiropractors to aid in clinical decision-making?

The continued evolution of evidence-based practice has had a significant effect on the use of imaging procedures in chiropractic. With most research demonstrating the limited utility of conventional radiography in spinal pain patients, I’ve seen a general decrease in taking radiographs, as well as fewer requests for advanced imaging modalities. The positive side of this is that with greater use of ‘red flag’ based guidelines, there are fewer ‘normal’ studies. I’ve found that using clinical decision tools has resulted in more studies with findings that affect the prognosis or management of the patient.

2. Chiropractors have several ways they can integrate imaging into their care plans – including referring the patient to an imaging center or offering onsite exams. Do you expect to see more practices bringing imaging in-house?

The trend demonstrated by the NBCE Practice Analysis shows a shift toward fewer chiropractors that own radiographic equipment in favor of referring patients to imaging centers. There are multiple reasons for this shift, such as the ability to refer to an imaging center for high-quality imaging, digital access to imaging via online portals, and the professional interpretation of a radiologist. Other reasons include the overhead costs of in-house imaging, the increasingly stringent quality-assurance/quality-control procedures required and decreasing reimbursements.

3. Many practices that offer onsite imaging use film. What advantages does digital imaging bring to practices?

Having worked in radiology when film was the only option, it’s easy to sing the praises of digital radiographs over film. With film, the only options you have for changing how it looks after the exposure is to use a brighter viewbox or a hot light. Of all the benefits of digital, I believe the greatest is the ability to manipulate the contrast and brightness of the images. Add to that the decrease in patient radiation exposure due to retakes, space savings from records storage, and the long-term cost savings of digital over film, and it makes the conversion to digital a fantastic choice.

Quote from Dr. Chad Warshal, NYCC4. Do chiropractors tend to read their own X-rays, or are the images sent to a radiologist and a report provided to the chiropractor?

The answer to that question is twofold. First, chiropractors receive intensive education in the interpretation of musculoskeletal radiographs. Because of that education, there is a certain degree of comfort in reading their own studies. However, one of the important points stressed in chiropractic education is the use of specialists. I had a diagnostic-imaging consultation practice before moving to academia, and I still maintain an imaging-consultation practice with New York Chiropractic College. I’ve noticed there are two major patterns when chiropractors refer studies for interpretation.

The first (and most common situation) is doctors of chiropractic who read their own films, but refer the problem cases or those with questionable findings to the radiologist for interpretation. The second scenario involves doctors who prefer to have all their imaging read by radiologists. This tends to be seen more with large medical-legal practices.

 5. There’s a perception that when an X-ray exam is needed, it’s usually best to have the exam interpreted by a radiologist and then have the report made available to your chiropractor. How has digital technology changed this?

Digital technology has made professional interpretation simple and convenient in a way that was unimaginable with analog film. If a field practitioner wants an interpretation on film-based images, the films have to be delivered or shipped to the radiologist, leading to a substantial lag in diagnostic evaluation. And there’s always the concern of films being lost or damaged in the mail. With the continued expansion of digital imaging, this allows essentially one-button pushing of images to a radiologist, even allowing reads from 3,000 miles away, two minutes after the images are taken. The interpretation is quick, there’s no chances of lost studies in the mail, and there are cost saving – not only in terms of postage, but also in terms of less staff time packaging and refilling films.

6. You head the radiology residency at New York Chiropractic College. Are you seeing interest grow in chiropractic imaging? What’s driving your students to choose this path?

Chiropractors have always had a strong interest in imaging. Over the years, that has evolved along with radiology, as we discover more about what imaging is – and is not – good for. The people who enter the postgraduate diagnostic imaging residency programs are those who have a strong academic talent, a good eye for interpretation, and have discovered a passion about the diagnostic aspect of health care.