The Biplanar Effect of the Medial Cuneiform Osteotomy.

Background. The "foot-CORA" (center of rotation of angulation) method confirms the medial cuneiform as the site of deformity in most forefoot/midfoot deformities and is therefore the ideal location to correct those deformities. It has been consistently observed intraoperatively by the senior author that there is a secondary, unintentional deformity created in the transverse plane when dorsiflexion and plantar flexion osteotomies of the medial cuneiform are performed to correct pronation and supination forefoot deformities, respectively. These effects may not be desirable. This biplanar effect of medial cuneiform osteotomies has been observed but not studied. The purpose of this study was to perform the 4 commonly used medial cuneiform osteotomy techniques on cadaveric feet to demonstrate their biplanar effects. Methods. Four formaldehyde preserved cadaveric feet were used to perform 4 techniques of medial cuneiform osteotomy: dorsiflexion plantar-based opening wedge, plantar flexion dorsal-based opening wedge, dorsiflexion dorsal-based closing wedge, and plantar flexion plantar-based closing wedge. Photographs and fluoroscopy were used to assess the angular changes in the sagittal and transverse planes. Angular measurements were made using OsiriX software on fluoroscopic images. Results. The medial cuneiform opening wedge osteotomies produced midfoot abduction in addition to the desired dorsiflexion and plantar flexion. The medial cuneiform closing wedge osteotomies produced midfoot adduction in addition to the desired dorsiflexion and plantar flexion. Conclusion. We confirm that intentional sagittal uniplanar osteotomies of the medial cuneiform create obligate biplanar effects. This is likely a result of tethering by ligaments and the joint capsules on the lateral border of the medial cuneiform. The obligate transverse plane effect can be used to one's advantage or result in an undesired effect if not considered during surgical planning and execution. We propose a simple treatment algorithm for selecting the appropriate medial cuneiform osteotomy for forefoot/midfoot deformities. Levels of Evidence: Level V.