Measuring hindfoot alignment in weight bearing CT: A novel clinical relevant measurement method.
BACKGROUND
A precise pre-operative measurement of hindfoot malalignment is paramount to plan and obtain an accurate surgical correction. Hindfoot alignment is currently determined on standard weightbearing radiographs. However this is hampered by the superposition of the skeletal structures. Recent technology developed weightbearing cone beam CT to overcome this problem. The objective is to introduce a clinically relevant and reproducible method to measure hindfoot alignment on weightbearing CT.


METHODS
Sixty malalignments of the hindfoot were divided in to two groups; group one containing a valgus alignment (n=30) and group two a varus alignment (n=30) of the hindfoot. Imaging techniques used were standard radiographs and a weightbearing CT (pedCAT®). Following angles were measured by two different authors: standard long axial hindfoot angle both on standard radiographs and on CT, clinical hindfoot, novel hindfoot angle, talar shift (distance from a neutral alignment), tibial inclination angle, talar tilt and subtalar vertical angle on CT.


RESULTS
Hindfoot alignment angles showed to significantly differ from each other (P<0.001). The novel hindfoot alignment angle showed the highest correlation with the clinical measurement method. Correlation of this novel angle with the talar shift showed a Spearman's correlation coefficient=0.87. Interclass correlation coefficient of the novel hindfoot alignment angle=0.72 and was the highest among the hindfoot alignment angles.


CONCLUSIONS
Weightbearing CT is allows to objectively assess hindfoot alignment. The proposed novel hindfoot alignment angle showed to be both clinically relevant and reproducible as compared to previous methods. The lateral tibiocalcaneal shift, on which the angle is highly correlated to, can help the surgeon in determining how much translation is necessary to obtain a neutral alignment during a calcaneal osteotomy.


METHODS
Level III: retrospective cohort study.
Department of Orthopaedic Surgery, H.-Hartziekenhuis, Mechelsestraat 24, 2500 Lier, Belgium; AZ Monica, Florent Pauwelslei 21, 2100 Deurne, Belgium. Electronic address: arne.burssens@ugent.be.
A
A
Burssens
AZ Monica, Florent Pauwelslei 21, 2100 Deurne, Belgium.
J
J
Peeters
ZNA Middelheim, Lindendreef 1, 2020 Antwerpen, Belgium.
K
K
Buedts
Department of Orthopaedic Surgery, Ghent University Hospital, De Pintelaan 185, 9000 Gent, Belgium.
J
J
Victor
Department of Orthopaedic Surgery, H.-Hartziekenhuis, Mechelsestraat 24, 2500 Lier, Belgium.
G
G
Vandeputte
D000328:Adult; D000368:Aged; D000818:Animals; D017760:Bone Malalignment / Q000000981:diagnostic imaging* / Q000601:surgery; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D005531:Foot Deformities, Acquired / Q000000981:diagnostic imaging* / Q000601:surgery; D006215:Hallux Valgus / Q000000981:diagnostic imaging* / Q000601:surgery; D050488:Hallux Varus / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D019637:Orthopedic Procedures / Q000379:methods; D011300:Preoperative Care / Q000379:methods; D020127:Recovery of Function; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018570:Risk Assessment; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D016474:Weight-Bearing
Hindfoot alignment; Hindfoot correction; Weightbearing CT