Influence of lower limb rotation on hindfoot alignment using a conventional two-dimensional radiographic technique.
BACKGROUND
Rotation is one of the variables explaining lack of reproducibility in assessing hindfoot alignment. The hypothesis for this study was that a mathematical model predicts how this modifies radiographic hindfoot alignment measurements.


METHODS
A cadaveric lower limb, disjointed at knee level, was used. Sagittal and coronal planes were fixed using a custom clamp. Standard AP views were shot every five degrees and measured hindfoot alignments were compared to theoretical values obtained from a mathematical simulation.


RESULTS
Hindfoot angle was 7.04° at 0° rotation and 2.11° at -90°. Intra-class and inter-investigator correlation was 0.863. The t-test showed no significant difference (p=0.73). Intra-investigator correlation was 0.957. The R2 correlation index was 0.852.


CONCLUSIONS
The mathematical model accurately predicted the variations of the hindfoot angle which was maximum when the foot was aligned with the X-rays source. It then decreased when the foot rotated away, following a parabolic curve.
CHU de Nantes, 1 place Alexis Ricordeau, Nantes, France.
L
L
Baverel
CHRU de Tours, 37044 Tours, France.
J
J
Brilhault
Avicenne University Hospital, 125 rue de Stalingrad, 93000 Bobigny, France.
G
G
Odri
CHU de Nantes, 1 place Alexis Ricordeau, Nantes, France.
M
M
Boissard
Ankle and Foot Surgery Centre, Clinique de l'Union, 31240 Saint Jean, France. Electronic address: francois.lintz@clinique-union.fr.
François
F
Lintz
D000368:Aged; D000843:Ankle Joint / Q000000981:diagnostic imaging* / Q000502:physiology*; D002102:Cadaver; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000000981:diagnostic imaging* / Q000502:physiology*; D008962:Models, Theoretical; D011237:Predictive Value of Tests; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results
Alignment; Foot; Forefoot; Hindfoot; Meary; Radiography