Placement of Plantar Plates for Lapidus Arthrodesis: Anatomical Considerations.

BACKGROUND: The modified Lapidus procedure is an accepted treatment option for patients with moderate to severe hallux valgus. Placing a plate plantar on the tension side of the arthrodesis has been shown to be biomechanically superior and has provided good clinical results. There is some concern about interference of the plantar placed plates on the tendon insertions. The purpose of this study was to determine a "safe zone" for plantar plate placement without irritation of the tendons.

METHODS: Twenty-nine embalmed right feet were used for this study. The anatomy of the insertion of the peroneus longus (PL) tendon and tibialis anterior (TA) tendon on the medial cuneiform and first metatarsal were analyzed. Six different plate designs for plantar plating of the first tarsometatarsal fusion were included. The fit to the bone and contact to tendon insertion were analyzed.

RESULTS: The PL showed a main insertion to the first metatarsal and a lesser insertion to the medial cuneiform. The TA inserted onto the medial cuneiform and first metatarsal in all cases in our series. There was a "safe zone" between the TA and PL insertion areas for plate placement. Straight, Y- and U-shaped plates could be placed without compromising the tendon insertion. Depending on the design, even preshaped plates may have to be bent to allow a good fit to the plantar side of the first tarsometatarsal joint.

CONCLUSION: Plantar plating for modified Lapidus arthrodesis can be safely performed, without damaging the plantar tendon insertion area of the PL and TA.

CLINICAL RELEVANCE: The exact knowledge of the anatomy of the plantar region of the tarsometatarsal joint can help to improve plate placement.