SLR - April 2018 - Laura Y. Lee

Flexible Adult Acquired Flatfoot Deformity Comparison Between Weightbearing and Nonweightbearing Measurements Using Cone-Beam Computed Tomography

Reference: Cesar de Cesar Netto, MD, Lew C. Schon, MD, Gaurav K. Thawait, MD, Lucas Furtado da Fonseca, MD, Apisan Chinanuvathana, MD, Wojciech B. Zbijewski, PhD, Jeffrey H. Siewerdsen, PhD, and Shadpour Demehri, MD. Flexible Adult Acquired Flatfoot Deformity Comparison Between Weightbearing and Nonweightbearing Measurements Using Cone-Beam Computed Tomography. J Bone Joint Surg Am. 2017;99:e98(1–12).

Reviewed By: Laura Y. Lee, DPM
Residency Program: DVA-New Mexico Healthcare System, Albuquerque, NM

Podiatric Relevance: The diagnosis of adult acquired flatfoot entails a wide spectrum of deformities, being a complex pathology consisting of both posterior tibial tendon insufficiency and failure of multiple other soft-tissue structures. Weightbearing CT allows for a more detailed understanding of the complex, three-dimensional deformity. The authors showed that weightbearing 3D extremity cone-beam CT outperforms multidetector CT for evaluation of the foot and ankle, with less radiation exposure.

Methods: This is a prospective study that recruited 20 adult patients (12 men, eight women) from September 2014 to June 2016 with symptomatic flexible adult acquired flatfoot deformity. Participants underwent two consecutive scans of the symptomatic foot: one NWB scan (sitting) and one WB scan (standing). Measurements were performed by two fellowship-trained foot and ankle surgeons and one fellowship-trained radiologist in an independent, random and blinded fashion.

Results:

  • Almost perfect intraobserver and interobserver reliability on both the NWB images (mean intraclass correlation coefficient (ICC), 0.80; range, 0.49 to 0.99) and the WB images (mean intraclass correlation coefficient (ICC), 0.81; range, 0.39 to 0.99). An ICC of 0.81 to 0.99 was classified as almost perfect homogenous agreement among observers.
  • Significant difference between the WB and NWB images with regard to the mean values of every measurement performed except for the calcaneal inclination angle.
  • Axial plane: WB measurements resulted in a significant increase in forefoot abduction with an increased talus-first metatarsal angle and talonavicular coverage angle.
  • Coronal plane: WB measurements showed increased collapse of the longitudinal and transverse arches of the foot and increased hindfoot valgus alignment with a decreased mean forefoot arch angle and decrease in navicular-to-skin distance, navicular-to-floor distance, medial cuneiform-to-floor distance. There were increased subtalar horizontal angles at the posterior position, middle position and anterior position of the subtalar joint.
  • Sagittal plane: WB images demonstrated increased collapse of the longitudinal arch of the foot, with an increased mean talus-first metatarsal angle and decreased in all other parameters: navicular-to-skin distance, navicular-to-floor distance, cuboid-to-skin distance, cuboid-to-floor distance, medial cuneiform-to-skin distance, medial cuneiform-to-floor distance and calcaneal inclination angle.
Conclusions: WB CT imaging is being more readily adopted because of its ability to create 3D images better able to demonstrate the full complexity of the structural failures of adult acquired flat foot deformity. This study demonstrated that weightbearing images better demonstrated the severity of osseous deformity. While it was a small sample size, the differences were significant to adequately support the authors’ conclusions. 

Educational Opportunities

Upcoming