Technique
A. Longitudinal Cut
- plantar proximal / dorsal distally
- ends up being parallel to sole
- leave strong plantar portion of head to prevent dorsiflexion
- mark centre of head
- distally to a point 2mm prox and 3mm above the centre of the head
B. Transverse cuts
- plantar proximal / dorsal distal
- angle of 45o with the long cut
- directed slightly proximal (10-15o) to aid displacement
Displacement
A. Transverse plane
- Primary direction of displacement
- can be up to ¾ of the surface as the strong lateral strut is preserved
- lateral rotation should be avoided as it increases the DMAA
- medial rotation can be used (to improve DMAA) but limits the amount of lateral displacement
B. Frontal plane
- Lowering of the 1st MT head is achieved via the obliquity of the transverse cut
- It will act to relieve metatarsalgia
C. Sagittal plane
- Lengthening can be done but tends to increase soft tissue tension and lead to stiffness
- shortening can be readily achieved by
- increasing the obliquity of the transverse cuts (max shortening 3mm)
- resecting ends of prox / distal fragments (doesn’t elevate head as II to sole)
Fixation
Cannulated screws over K wires
A. Distal
- start lateral where the bone is string and allows medial resection
- aim obliquely into the MT head
- screw to end 2mm prox to cartilage
B. Proximal
- important to respect the lateral part of the fragment to avoid fracture
- aim transverse from dorso-medial to plantar-lateral
The corner is then taken off the proximal fragment
- rounded with rongeurs where bunion has been sliced off