Foot and ankle radiographic parameters: validity and reproducibility of biplane imaging system versus conventional radiography Chamnanni Rungpai, MD; Jessica E. Goetz, PhD; Marut Arunakul, MD; Yubo, Gao, PhD; John E. Femino, MD; Annunziato Amendola, MD; Phinit Phisitkul, MD University of Iowa Hospital and Clinics
Foot and ankle radiographic parameters: validity and reproducibility of biplane imaging system versus conventional radiography Chamnanni Rungpai, MD My disclosure is in the Final AOFAS Mobile App. I have no potential conflicts with this presentation.
Introduction Accurate understanding of foot and ankle alignment is important in the clinical diagnosis, surgical planning, and post-operative follow up. However, there is currently no radiographic technique that allows complete threedimensional evaluation of the entire lower limbs. Conventional (2D) radiography is commonly used with some limitations such as 1.Magnification error 2.Difficulty in obtain lone leg film 3.Lack of three dimensional information CT scan is alternative option and provides high resolution 3D data but it is not routine practical use due to 1. High cost 2. High radiation exposure 3.Non-weight bearing technique except PedCAT but it is confined only 20 cm from the floor.
Biplane Imaging system Recently, can simultaneously capture two orthogonal AP and lateral view results in better understanding of lower limb in 3D. In addition, it is Weight bearing technique No magnification error Low doses of radiation exposure. Propose The purpose of this study was to evaluate the validity and reproducibility of a biplane imaging system for 2D angular and distance measurements of commonly used foot and ankle radiographic parameters compared to conventional radiography. In addition, lower limb alignment, limb length, and limb length discrepancy was compared between the and non feet position.
Materials and methods 50 consecutive patients (69 feet) indicated for foot and ankle realignment surgeries were included. Radiographic studies included weight bearing AP and lateral ankle using conventional X-rays Long leg AP non- feet using 2D imaging system. Long leg AP and lateral feet position 2D imaging system. All radiography were performed at the same day. All measurements were measured by two blinded observers. One observer repeating all the measurements at 6 weeks apart.
Common foot and ankle parameters, lower limb alignment, and limb length measurement 1. Talocrural angle 2. Tibiofibular clear space 3. Medial clear space 4. Talar tilt angle 5. Lateral distal tibial angle (LDTA) 6.Calcaneal pitch 7. Lateral talo-calcaneal angle 8. Lateral talo-1 st metatarsal angle 9. Medial cuneiform-5 th metatarsal height 10. Anterior distal tibial angle (ADTA) 11. Hip Knee Shaft angle (HKS) 12. Hip Knee Ankle angle (HKA) 13. Femoral Neck Shaft Angle (FNSA) 14. Femur length (front and rear leg) 15. Tibia length (front and rear leg) 16. Entire lower limb length (front and rear leg) 17. Mechanical axis discrepancy technique 18. Total limb length discrepancy technique
Optimal foot positioning in long leg lateral view Long leg lateral view weight bearing Long leg AP view weight bearing Staggered feet position: Illustrating osseous structures starting from the 1st metatarsal head of front foot (A) and ending with lowest part of calcaneus of rear foot (B). These pictures showed all parameters in the AP view
Comparing between convention X-ray and imaging and non feet position Intraclass Correlation Coefficient (ICCs) AP View Result: One-way ANOVA conventional radiograph compared with non Intra-observer ICC non- Inter-observer ICC non Talocrural angle 0.901 0.791 0.997 0.987 0.998 0.976 Talar tilt 0.991 0.991 0.990 0.998 0.988 0.999 Tibio-fibular clear space Medial clear space Lateral distal tibial angle 0.963 0.981 0.993 0.955 0.986 0.927 0.916 0.926 0.993 0.938 0.992 0.930 0.913 0.996 0.995 0.954 0.997 0.949
Hip Knee Ankle angle (HKA)* 0.585 0.999 1.000 0.997 1.000 Femoral Neck Shaft Angle (FNSA)* 0.370 0.999 1.000 0.999 1.000 (*) HKS, HKA, FNSA were compared between and non- feet position in AP view but the rest of the lateral parameters compared between conventional radiography with the feet position in lateral view. Comparing between conventional x-ray and feet position Intraclass Correlation Coefficient (ICCs) Lateral view Paired t-test p-value Intra-observer ICCs Conventional / non- Inter-observer ICCs Conventional / non- Calcaneal pitch angle 0.180 0.999 0.998 0.991 0.995 Lateral talo-calcaneal angle 0.067 0.999 0.999 0.990 0.993 Lateral talo-1st metatarsal angle 0.795 1.000 1.000 1.000 0.999 Medial cuneiform- 5th metatarsal height 0.068 1.000 1.000 1.000 0.998 Anterior distal tibial angle 0.856 0.998 0.998 0.991 0.994 Hip Knee Shaft angle (HKS)* 0.863 0.989 0.989 0.987 0.978
Comparing between and non- feet position Limb length Limb length discrepancy pair t-test p-value Intraclass Correlation Coefficient (ICCs) Intra-observer ICC non- Inter-observer ICC non- Femur length (front leg) 0.464 1.000 1.000 0.999 0.999 Tibial length (front leg) 0.305 1.000 1.000 0.999 0.998 Entire lower limb length (front leg) 0.650 1.000 1.000 1.000 1.000 Femur length (rear leg) 0.002 1.000 1.000 1.000 1.000 Tibial length (rear leg) 0.049 1.000 1.000 0.999 0.999 Entire lower limb length (rear leg) Limb length discrepancy using mechanical axis technique Limb length discrepancy using entire lower limb technique 0.001 1.000 1.000 1.000 1.000 0.000 1.000 1.000 0.999 1.000 0.000 1.000 1.000 0.999 0.999
Limitation Conclusion No patients younger than 15 years old the findings cannot be extrapolated to skeletally immature patients. Difficulties in obtaining acceptable images in some patients. Six percent (4/69) of the subjects were excluded improper positioning within the or poor image quality. The biplane imaging system or TM imaging was a valid and reliable measurement of commonly used foot and ankle radiographic parameters when compared to conventional radiographic methods. Staggered foot positioning allowed simultaneous imaging of both feet in lateral view without affecting limb alignment Except femur length, tibial length, entire lower limb length of the rear leg, and limb length discrepancy measurement.
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