Abstract
Background
A calcaneal medial osteotomy (CMO) is a surgical procedure frequently performed to correct a valgus alignment of the hindfoot. However currently little is known on its accurate influence on hindfoot alignment (HA).
Aim
To assess the influence of a CMO on HA in both 2D and 3D measurements using weightbearing CT (WBCT).
Methods
Twelve patients with a mean age of 49,4 years (range 18–67yrs) were prospectively included. Indications for surgical correction by a CMO with a solitary translation of the calcaneus consisted of an adult acquired flat foot stage II (N=10) and a talocalcaneal coalition (N=2). Fixation of the osteotomy was performed either using a step plate or double screw. A WBCT was obtained pre- and post-operative. HA was assessed by an angle between the anatomical tibia axis and the axis connecting the inferior calcaneus point and the middle of the talus in the coronal plane (HA2D) using Curvebeam® software. The tibia in the HA was separately assessed by the anatomical tibia axis (TAX 2D). The same method was translated in 3D using 3-Matic® software with a Cartesian coordinate system originating in the inferior point of the calcaneus (HA3D and TAx 3D).
Results
Both the mean pre-op HA2D=12.8°± 4.5 and HA3D=21.1°± 8.4 of valgus improved significantly post-operatively to a HA2D=4.2°±4.5 and a HA3D=11,9°± 6.1 (P < 0.001). Additionally, the mean pre-op TAX 2D = 4°± 2.6 and TAX 3D = 7,2 °± 3.2 showed a significant improvement to a TAX 2D = 3.1°± 2.7 and a TAX 3D = 6.1 °± 3.4 post-operatively (P < 0.05). The inter-rater reliability of the 2D measurement method with a mean ICCHA2D=0.74 and a mean ICCTA2D= 0.77 showed to be lower when compared to the 3D measurement method with a mean ICCHA3D=0.94 and a mean ICCTA3D=0.89.
Conclusion
This study shows an effective correction of the valgus position from the calcaneus measured both in 2D and 3D when using a surgical CMO. The novelty is the marked influence on the tibia, which could now be accurately assessed using a weightbearing CT and additional 3D measurements. This resulted in 10% of the achieved HA correction, when analyzed both in 2D and 3D. This information could be of use when performing a pre-operative planning of a hindfoot deformity.
