Three-dimensional computer analysis of the modified Ludloff osteotomy.

Background: The Ludloff first metatarsal osteotomy is used to correct the increased 1-2 intermetatarsal angle associated with hallux valgus deformity. We studied the spatial geometry of this osteotomy to determine the ideal parameters of the osteotomy saw cut and its rotation to give an optimal correction.

Methods: Three-dimensional computer modeling software was used to perform a virtual Ludloff osteotomy of the first metatarsal. Different geometric parameters of the osteotomy were studied. The osteotomy was rotated in virtual space and the geometric changes occurring in the virtual bone were then measured by the software.

Results: The optimal Ludloff osteotomy started at the dorsum of the first metatarsal base at the first tarsometatarsal joint and extended distally and plantarly to a point just proximal to the sesamoid articulation. A tilt of 10 degrees in the coronal plane of the osteotomy was necessary to limit first metatarsal head elevation. The best axis of rotation was within 5 mm of the proximal end of the osteotomy.

Conclusions: The optimal geometric parameters of a modified Ludloff osteotomy limited first metatarsal shortening, elevation, and sagittal plane rotational malalignment that may occur with the use of this osteotomy.