A Straightforward Guide To The Lapidus Bunionectomy
The popularity of the Lapidus bunionectomy seems to ebb and flow over the years. When we compare the Lapidus to other bunionectomy procedures, such as an Austin or similar distal metaphyseal osteotomies, there seems to be more reasons not to do a Lapidus.
The main reason not to do an Austin bunionectomy may be that the deformity is too large or too flexible/unstable. For a Lapidus bunionectomy, the reasons for not choosing the procedure include: fear of excessive metatarsal shortening; delayed union or nonunion of the fusion site; malunion with excessive dorsiflexion or plantarflexion of the first metatarsal; cast immobilization (and associated sequelae). Other reasons are a lack of experience with the procedure and a greater degree of technical difficulty with the Lapidus in comparison to a distal metaphyseal osteotomy.
Like anything else, there is a learning curve when doing a procedure a few times a year versus every week. If you are like me, you probably do at least one Austin bunionectomy a week. How many tarsal coalitions are you going to do? How many intramedullary nails are you going to put in? Certainly, it depends on your practice and if you have a referral practice from other podiatrists to do the “tough” cases.
The majority of podiatric surgeons are doing forefoot surgery including bunionectomies. We choose to do what we do best. We choose procedures we feel confident that we can technically perform well. I hear all the time from colleagues that “I pushed the Austin” or “I did an Austin but probably needed a base wedge or Lapidus.” So for those cases, maybe we should hone our skills to perform a Lapidus when necessary.
Lapidus bunionectomies certainly have their merits and I do them on occasion. For the right patient, you can get great correction, especially in larger deformities. So I want to break it down for you, namely how to make the Lapidus easy. My technique allows excellent visualization of the entire joint and eliminates wedging and the removal of any “significant” bone.
First, there is some debate as to whether a lateral release is necessary. My opinion is that if you have a young patient, there probably is not a significant hypertrophic metatarsal head (i.e. bunion) and if you can realign the great toe joint, then you do not need to do the distal metatarsophalangeal joint (MPJ) dissection. In older patients, I tend to do a modified McBride as I feel there is hypertrophy of the medial metatarsal head and significant contractures/adaptation on the lateral MPJ.
In this scenario, the lateral release is beneficial. Remember, the key to a successful long-term result in bunion surgery is that the metatarsal head is sitting on top of the sesamoids and the medial condyle of the base of the proximal phalanx is sitting in the sagittal groove of the metatarsal head. If you obtain that, then the joint is congruent. Older patients have frozen sesamoids, joint contractures and hypertrophy of bone. It order to realign the joint, one is going to need to do more than just reduce the intermetatarsal angle.
Pertinent Pearls On Surgical Technique
For illustration purposes, let us assume that we are going to do a modified McBride with the Lapidus. I start the procedure with a standard modified McBride through a dorsomedial incision. Once that is complete, I will do a medial incision for the Lapidus. I will mark the midline bisecting the dorsal and plantar margins of the foot.
Then I make an incision over the proximal metatarsal and medial cuneiform. The incision is typically 4 to 5 cm in length. After making the incision, you will encounter small veins, which you can cauterize. Next, you will encounter the pseudo deep fascia layer, which you can cut with scissors. The larger veins are now in this layer of the fat. Tributaries from the medial marginal vein are running dorsal to plantar. One will need to clamp, cut and tie these tributaries. The dorsal tissues will have the main vein trunk, which surgeons can protect with retractors.
Now that we have appropriately managed the vein, use a scalpel to incise the capsule and periosteum layer. The tibialis anterior tendon will always be in the way and you may need to partially release some of the inferior attachments. Then reflect the capsule and periosteum, and it is paramount to release the dorsal joint ligaments. A simple trick is to take a Freer elevator or mini-Hohmann retractor to tent up the dorsal tissues and then you can slip the scalpel blade inside to outside of the joint, releasing soft tissues and ligaments. Complete mobilization of the first metatarsal base is required to get the correction you need.
After releasing the first metatarsal base from soft tissues, I will use a mini-joint distractor to open the joint. You can use an AO mini-joint distractor or a Hintermann type device. When the joint is distracted, you will know if you have any remaining soft tissues that need to be released. If so, you can do that now. I generally will remove the cartilage with curettes down to the subchondral bone plate. You can do the subchondral drilling at this time or you can fish scale with a narrow osteotome.
The next step is to remove the joint distractor and to use a small periarticular clamp, placing it on the medial first and lateral second metatarsal necks. Gently squeeze the clamp until the intermetatarsal angle reduces to zero or the first metatarsal is parallel to the second metatarsal. I will generally make a small stab incision on the lateral border of the second metatarsal neck for the placement of the clamp.
After obtaining the desired correction, I will use a sagittal saw to plane the joint in the corrected position. Insert the saw medial to lateral, making sure the dorsal and plantar edges are planed as well. Typically, one is taking more bone off the cuneiform at the lateral side to “straighten” out the joint. Once I have prepared the surfaces with the saw, I will use a rongeur to remove bone and cartilage fragments. At this point, it is imperative to make sure there is not a ledge of bone on the plantar aspect of the fusion site. You can always use the joint distractor to visualize the joint surfaces better.
Leave the clamp intact while placing a 0.062 K-wire for temporary fixation. At this time, you can implement whatever permanent fixation you like. I prefer two Nitinol compression staples, one dorsal and one medial. The staples provide extra-articular fixation as well as bicortical compression. Technically, this is much easier and quicker than inserting lag screws with or without a plate. Apply standard layer closure and dressings in addition to a well padded, below knee posterior splint.
Regardless of the type of fixation I use, I will typically keep these patients non-weightbearing for four to six weeks. After the first postoperative check-up, I will place patients in a fracture boot. They can subsequently do range of motion exercises of the great toe joint and ankle joint motion to prevent deep venous thrombosis and minimize calf atrophy.
Hopefully, this technique guide breaks down the Lapidus bunionectomy into something simple and straightforward.