Surgeons performing the Lapidus bunionectomy often consider the sagittal and frontal plane position of the first metatarsal bone. However, surgeons place less attention on the frontal plane position. It’s not that surgeons do not consider frontal plane position but it is a more subtle technical aspect of the procedure that has not been discussed much in the literature.
Frontal plane position is not as “critical” as sagittal or transverse plane as patients will better tolerate a slight deviation in the frontal plane. Frontal plane malalignment will manifest itself as sesamoiditis and/or unexplained pain in the first metatarsophalangeal joint several months after the surgery.
Clearly, gross frontal plane malalignment will be evident to the surgeon. However, a slight rotation may not be visible intraoperatively. The following intraoperative maneuver will help you align the first metatarsal in the proper frontal plane position.
Once the first tarsometatarsal joint is exposed, create a linear mark perpendicular to the joint. You can do this with a marker or the cautery (see photo).
Then you can prepare the joint for fusion. As you place the first metatarsal in a corrected position, use these hash marks to align the frontal plane position. It is important to understand that the sagittal plane position of the hash marks may change as one may translate the first metatarsal inferiorly as part of the Lapidus bunionectomy. These hash marks should remain parallel to each other. However, if you use a sagittal saw to create a wedge, then this technique may not be as reliable.
I have found this technique very helpful as it provides me with a reference point for the frontal plane position when performing a Lapidus bunionectomy.