Emerging Concepts With Post-Lapidus Bunionectomy Weightbearing
The initial experience of surgeons with plates involved simple linear tubular plates that they seemed to use as a bailout when screw fixation failed intraoperatively. These linear plates were not anatomic and required significant bending to make the plates fit better. Often, these plates invaded the naviculocuneiform joint. The advantage of the linear plates was that the surgeon could achieve a long lever arm on the metatarsal component of the fusion but without the cuneiform stability, the cantilever effect did not appear to be effective. Some surgeons recognized this and used concomitant screws to provide this “extra” stability in a belt and suspenders approach.
Larger T-shaped plates were briefly popular but these plates were developed for distal radius fractures. Accordingly, there is a huge shape mismatch on the medial cuneiform and the plates were prominent and intrusive to the tibialis anterior and the extensor hallucis longus tendon. Additionally, the screw orientation into the medial cuneiform was not ideal.
The first generation of dedicated Lapidus plating systems offered a four-hole design with two periarticular screws and some with various step-offs within the plate considered that final position of the metatarsal on the cuneiform to achieve a better fit. Locking systems offered more stability. Two theoretical disadvantages of periarticular plating systems are that the cantilever forces are not specifically addressed intrinsically within the plate and compression does not occur.
The second-generation systems involved more anatomically minded locking plating systems that had a smaller T-shape to increase the fixation options available in the medial cuneiform. The stem of the T provides a longer metatarsal component for a compression hole. Again, some surgeons still utilized a screw that was not incorporated into the plate, mainly because of previous plate generation habits. Another variation is systems that provide a recessed transfixation screw incorporated into the plate. This recessed screw requires one to bore out the undersurface of bone to allow the flat plate to lay against the bone. Flat plates may require bending to match the shape of the fusion site.
A Closer Look At The Third Generation Of Plating Systems
Third-generation Lapidus plating systems include features of previous generations but are designed (contoured) for the special anatomy of the first tarsometatarsal fusion site. In particular, I would like to discuss the Contours Lapidus Plating System (Orthofix).
There are a few important design features with regard to the shape. First, the plate matches the geographic landscape of the underlying bones. The plate is not flat and is essentially pre-bent. The contour of the plate intrinsically incorporates the final position of the fusion site with the specific consideration that the joint is resected and the metatarsal component either translates inferiorly on the cuneiform or plantarflexes.
Second, this plate was designed to fit within the safe zone on the medial surface of the fusion site, avoiding the extensor hallucis longus tendon course (superiorly) and the tibialis anterior tendon insertion (inferiorly). Accordingly, there is less chance for soft tissue irritation because the plate does not interfere with mobile structures.