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Published on: July 2, 2021
Defining normal joint space width in essential joints of the foot and ankle using an objective weight bearing CT
Hannah J Zeller1, Donald D Anderson2, Tutku Tazegul1
1Departments of Orthopedics and Rehabilitation, The University of Iowa, 200 Hawkins Dr, Iowa City, IA 52242, United States.
Background:
The tibiotalar (TT), subtalar (ST), talonavicular (TN), and first metatarsophalangeal (MTP) joints of the foot and ankle are essential for foot mobility and function. Assessing progression of osteoarthritis (OA) in these joints involves subjective radiographic grading that lacks reliability and reproducibility. The purpose of this prospective comparative study was to define normal articular features and joint space width (JSW) in four joints of the foot and ankle using objective analysis of weight-being CT (WBCT) intensity profiles in healthy, non-arthritic subjects.
Methods:
This was a cross-sectional IRB-approved study (ID #201904825) where bilateral WBCT scans of the foot and ankle were performed in 20 healthy subjects (40 feet, 9 females, 11 males) with no clinical or radiographic evidence of OA, bony abnormalities, or foot deformities. Five parallel linear spatial projections were generated across the joint space to measure WBCT intensities extending from subchondral bone, to cartilage, through the joint space, then to opposing cartilage and subchondral bone. The software graphically plotted WBCT intensity profiles of these projections which were then interpreted to measure the joint space width (JSW) and Michelson contrast of Hounsfield unit (HU) intensities, two relevant metrics of joint preservation, for each joint.
Results:
The average JSW for healthy TT, ST, TN, and first MTP joints were 3.97 (95 % CI 3.73 - 4.20), 4.20 (3.96 - 4.44), 3.33 (3.07 - 3.58), and 3.87 (3.64 - 4.12) mm, respectively. The average Michelson contrast was 71.8 (95 % CI 67.32 - 76.26), 92.5 (87.82 - 97.08), 84.1 (79.25 - 88.85), and 101.4 (96.87 - 105.81), respectively.
Conclusion:
We utilized a novel 3D analysis of WBCT intensity profiles to assess normal JSW and HU intensities in four joints of the foot and ankle to provide a foundation for future work developing an objective grading system for osteoarthritis.
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