Ground Reaction Force Calcaneal Offset: A new measurement of hindfoot alignment.
BACKGROUND
The tibio-calcaneal angle (TCA) does not measure individual forefoot contributions to the overall foot balance. Using standard radiographs we calculated the ideal hindfoot alignment based on ground reaction force (GRF), independently from the tibial axis.


METHODS
Thirty-six patients (40ft.) were included. Mean age was 56. Weight bearing radiographs were taken. Calcaneal offsets were measured using tibio-calcaneal angles and GRF algorithms. Measurements were compared using the Bland-Altman method.


RESULTS
Both methods agreed (p>0.05) but individual discrepancies were found. Mean measured offsets were -11.5mm (SD: 10.2) using TCA and -8mm (SD: 9.3) using GRF. Mean bias between the methods was -0.88mm.


CONCLUSIONS
The GRF algorithm successfully measured hindfoot alignment. The absence of a previous gold standard and radiographic variability are a limit. The TCA underestimated calcaneal offset. Discrepancies showed that forefoot position data provided increased accuracy. This could be of particular relevance for surgical planning.
Avon Orthopaedic Center, Southmead Hospital, Westbury-on-Trym, Bristol BS10 5NB, United Kingdom. francoislintz@gmail.com
Francois
F
Lintz
Tristan
T
Barton
Mark
M
Millet
William J
WJ
Harries
Stephen
S
Hepple
Ian G
IG
Winson
D001696:Biomechanical Phenomena; D002111:Calcaneus / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D005545:Forefoot, Human / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D016059:Range of Motion, Articular; D025321:Surgery, Computer-Assisted / Q000379:methods; D016896:Treatment Outcome; D016474:Weight-Bearing / Q000502:physiology