Orientation of Cut Angle in Distal Tibia Derotation Osteotomy Can Create Unintended Sagittal and Coronal Plane Deformity at the Ankle

Abstract

Introduction: Distal tibial osteotomy is commonly used for surgically correcting tibial torsion. While the effect of purposeful oblique osteotomies are well described, minimal data exists regarding how variation of distal tibial osteotomy cut angle may inadvertently affect final ankle alignment. Aim: To assess changes in orientation of the cut angle in distal tibial osteotomies on ankle alignment in specimens with existing rotational deformities. Materials and Methods: Using preserved human tibia specimens; we identified ten specimens with the greatest degree of rotational deformity. Surface scanning produced a three-dimensional image of each tibia. Digitally, we created transverse and 10° angled cuts, five centimeters above the distal tibial articular surface. Specimens were three-dimensionally printed and cross-pinned at 0°, 20° and 40° of internal or external rotation. Anterior-posterior and lateral radiographs were obtained at each degree of rotation and the Anterior Distal Tibial Angle (ADTA) and Lateral Distal Tibial Angle (LDTA) were calculated. Results: No significant differences in LDTA or ADTA measurements was found based on degree of rotation in internally and externally rotated specimens using a transverse osteotomy. In angled osteotomies, LDTA and ADTA measurements were significantly different based on the degree of angulation in internally rotated (p=0.02, p=0.007; respectively), but not externally rotated (p=0.74, p=0.40; respectively) specimens. Conclusion: Distal tibia osteotomy cuts parallel to the distal joint surface can result in unanticipated coronal and sagittal plane deformity particularly with correction of internal tibial torsion. Osteotomies made perpendicular to the axis of the tibial shaft maintain native ankle alignment.

Keywords

• axial plane
• cadaveric
• tibial torsion