First tarsometatarsal (TMT) joint arthrodesis, also known as the Lapidus bunionectomy, is an increasingly popular procedure for addressing the moderate to severe hallux valgus deformity. The procedure is a powerful way to reduce a high first intermetatarsal (IM) angle and prevent long-term recurrence by addressing the etiology of the deformity instead of just addressing the bump.
While the procedure has its advantages, the execution of the procedure is more involved than other procedures for hallux valgus. First tarsometatarsal arthrodesis requires the surgeon to address the deformity in multiple planes. This requires surgeons to do more than just shift the metatarsal head laterally and fixate with two screws as can be the case with a distal metatarsal osteotomy. The rotation of the first metatarsal to reduce the sesamoid complex while simultaneously reducing the IM angle and then temporarily fixating the reduced deformity can prove challenging at times. When you compound this with the fact that many surgeons may not have an extra set of eager resident hands available to help, it is no wonder that many avoid the procedure altogether. If the surgeon opts for a different approach, in some cases, one may under-correct the deformity.
When I was a fellow, I picked up a great technique for reducing and temporarily fixating the first metatarsal that did not require any extra hands, was quick and reproducible, and allowed me to use any fixation construct I chose once I had achieved adequate positioning. The following steps demonstrate how you can adopt this technique in your OR.
First, one should achieve adequate joint preparation and exposure. I typically use two medial incisions for the Lapidus procedure (see first photo to right), one incision measuring about three cm at the first tarsometatarsal joint and another measuring about two cm at the medial eminence. I typically use a Hintermann distractor to open the joint from medial to lateral and then use a reciprocating power rasp to denude all cartilage from the joint surface. Of note, I also make sure to properly take down the plantar lateral portion of the joint that can often hold up the reduction (see second photo to right). Then I proceed to use a 2.0 mm drill bit to fenestrate the metatarsal and cuneiform sides of the joint. Then I pack in cancellous bone graft previously harvested from the patient into the prepared joint before removing the Hintermann distractor.
Second, I take the pins that I used in the Hintermann distractor, place them back into their tracking holes without the Hintermann distractor and use them to derotate the first metatarsal and reduce the sesamoid position (see third to right). While doing this, I use a large Weber clamp with one arm around the second metatarsal head and the other directly on the distal first metatarsal head, clamping it down until I adequately reduce the first IM angle and sesamoid position (see fourth photo set to right).
Third, placement of a temporary fixation wire or guide wire for a 4.0 mm screw can hold and reduce the position permanently. I typically like to use a first metatarsal to intermediate cuneiform screw to hold my reduction in place and then supplement with a medial plate at the first tarsometatarsal joint (see fifth photo set to right). I finally resect any excess bone from the medial eminence as necessary and do any capsular work before closing the incisions. This step is subject to surgeon preference in terms of fixation construct as the reduction technique does not force the surgeon into any one final construct over another.
That is it! Those are three easy steps for a quick and reproducible Lapidus procedure!
Dr. Rahnama is a fellowship-trained foot and ankle surgeon and an Assistant Professor at the Georgetown University School of Medicine in Washington, D.C. You can follow him on Instagram @DrAliRahnama for interesting cases and educational material.
A special thank you to our local Arthrex team for supplying us with their facility, hardware and cadaver limb for the production of this article's images. Dr. Rahnama discloses he was previously a consultant for Arthrex.