Amy L Lenz1, Nicola Krähenbühl1, Kalebb Howell1, Rich Lisonbee1, Beat Hintermann2, Charles L Saltzman1, Alexej Barg3. 1. Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT, 84132, USA. 2. Department of Orthopaedics, Kantonsspital Baselland, Rheinstrasse 26, 4410, Liestal, Switzerland. 3. Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT, 84132, USA. alexej.barg@hsc.utah.edu.
Abstract
OBJECTIVE: Using digitally reconstructed radiographs (DRRs), we determined how changes in the projection angle influenced the assessment of the subtalar joint. MATERIALS AND METHODS: Weightbearing computed tomography (CT) scans were acquired in 27 healthy individuals. CT scans were segmented and processed to create DRRs of the hindfoot. DRRs were obtained to represent 25 different perspectives to simulate internal rotation of the ankle with and without caudal angulation of the X-ray beam. Subtalar joint morphology was quantified by determining the joint space curvature, subtalar inclination angle (SIA), calcaneal slope (CS), and projection of the subtalar joint line on three-dimensional (3-D) reconstructions of the calcaneus. RESULTS: The curvature of the projected joint space was altered substantially over the different DRR projections. Simulated caudal angulation of the X-ray beam with respect to the ankle decreased the SIA and CS significantly. Internal rotation also had a significant impact on the SIA and CS if the X-ray beam was in neutral or in 10° of caudal angulation. An antero-posterior (AP) view of the ankle showed the posterior area of the posterior facet, whereas a more anterior area was visible with internal rotation of the foot and caudal angulation of the X-ray beam. CONCLUSION: Internal rotation of the foot of 20° is recommended to assess the posterior aspect of the posterior facet, whereas a combined 20° internal rotation of the foot and 40° caudal angulation of the X-ray beam is best to assess the anterior aspect of the posterior facet of the subtalar joint.
OBJECTIVE: Using digitally reconstructed radiographs (DRRs), we determined how changes in the projection angle influenced the assessment of the subtalar joint. MATERIALS AND METHODS: Weightbearing computed tomography (CT) scans were acquired in 27 healthy individuals. CT scans were segmented and processed to create DRRs of the hindfoot. DRRs were obtained to represent 25 different perspectives to simulate internal rotation of the ankle with and without caudal angulation of the X-ray beam. Subtalar joint morphology was quantified by determining the joint space curvature, subtalar inclination angle (SIA), calcaneal slope (CS), and projection of the subtalar joint line on three-dimensional (3-D) reconstructions of the calcaneus. RESULTS: The curvature of the projected joint space was altered substantially over the different DRR projections. Simulated caudal angulation of the X-ray beam with respect to the ankle decreased the SIA and CS significantly. Internal rotation also had a significant impact on the SIA and CS if the X-ray beam was in neutral or in 10° of caudal angulation. An antero-posterior (AP) view of the ankle showed the posterior area of the posterior facet, whereas a more anterior area was visible with internal rotation of the foot and caudal angulation of the X-ray beam. CONCLUSION: Internal rotation of the foot of 20° is recommended to assess the posterior aspect of the posterior facet, whereas a combined 20° internal rotation of the foot and 40° caudal angulation of the X-ray beam is best to assess the anterior aspect of the posterior facet of the subtalar joint.
Authors: Alexandre Leme Godoy-Santos; Alessio Bernasconi; Marcelo Bordalo-Rodrigues; François Lintz; Carlos Felipe Teixeira Lôbo; Cesar de Cesar Netto Journal: Radiol Bras Date: 2021 May-Jun
Authors: Arne B M Burssens; Kris Buedts; Alexej Barg; Elizabeth Vluggen; Patrick Demey; Charles L Saltzman; Jan M K Victor Journal: Clin Orthop Relat Res Date: 2020-01 Impact factor: 4.755
Authors: Nicola Krähenbühl; Amy L Lenz; Rich J Lisonbee; Andrew C Peterson; Penny R Atkins; Beat Hintermann; Charles L Saltzman; Andrew E Anderson; Alexej Barg Journal: J Orthop Res Date: 2020-09-07 Impact factor: 3.494