Siddiqui’s Tips, Tricks, and Pearls for Minimally Invasive Bunionectomy

Hallux valgus deformity is a common forefoot pathology, characterized as a progressive deformity of the first ray with lateral deviation and pronation of the hallux coupled with a medial deviation of the first metatarsal.^1,2 Treatment is typically initiated with conservative modalities such as a change in shoe gear, use of orthotics, or modifications to activity. Given the progressive nature of this deformity, conservative modalities are often insufficient, and surgical intervention is necessary to correct the deformity and restore the mechanical axis of the first ray.²

The mechanical axis is an aid that can be drawn to verify the correction.³ Before hallux valgus surgery, the anatomic axis and mechanical axis will overlap on the first metatarsal. Although this changes after the osteotomy, the mechanical axis can still be drawn and allows for the calculation of the intermetatarsal angle and tibial sesamoid position (see Figure 1).   

Traditional surgical interventions are well-detailed in the foot and ankle literature and are typically represented as open procedures with extensive intra-articular and capsular dissection. Severe deformity even routinely involves first tarsometatarsal joint arthrodesis. It was not until Bösch detailed the minimally invasive approach in 1990 that the idea of a minimally invasive technique without extensive intra-articular dissection was presented.⁴ Ten years later, the authors reported a patient satisfaction rate of 95% at a 7–10-year follow-up period.⁵

Although this was introduced more than 30 years ago, minimally invasive hallux valgus correction has only recently gained traction and popularity. Siddiqui reintroduced the concept in Podiatry Today in 2014 and 2016.^1,6 Since then, stable internal fixation methods popularized by Vernois and Redfern⁷ have eliminated the need for temporary pin fixation.

While there is a plethora of literature available regarding open techniques for hallux valgus correction, there is a relative paucity of literature regarding minimally invasive techniques, largely due to the still-uncommon nature of the procedure. Advantages unique to the minimally invasive technique include minimal soft-tissue disturbance (which preserves vascularity), maintaining relative stability of the osteotomy, and early weight-bearing and mobilization of the metatarsophalangeal joint (MTPJ).² These benefits can lead to increased patient satisfaction and excellent outcomes.

The senior author of this article (NAS) has been performing a minimally invasive approach since 2012 with well-documented positive outcomes of appropriate follow-up.⁸ The goal of this article is to present a systematic case guide that provides surgical tips, tricks, and pearls for our approach to minimally invasive bunion correction.

A Stepwise Surgical Approach to MIS for Bunions

The patient is placed in a supine position, with a sterile bump or trauma triangle placed under the knee allowing for approximately 30–45° of knee flexion. The lower extremity is prepped in the usual aseptic fashion, including above the level of the knee.

The procedure begins with fluoroscopy-assisted identification and marking of the following (see Figure 2):

1. Long axis of the first metatarsal
2. Trajectory of the most proximal screw path
3. First metatarsal neck, angulated in the direction in which the osteotomy is to be performed

Once the above lines have been drawn, the procedure is then completed as follows:

Step 1. A 1–1.5 cm incision is made along the medial aspect of the first metatarsal base at the intersection of the previously demarcated long axis of the first metatarsal and base of the first tarsometatarsal joint. This is typically near the naviculocuneiform joint. The authors prefer to sharply incise with a #64 Beaver blade (Beaver-Visitec International) followed by blunt dissection to the level of bone.

Step 2. At this point, along the previously demarcated trajectory, a 1.6-mm Kirschner wire (K-wire) is then inserted through the incision and the medial base of the first metatarsal, directed distal laterally towards the first intermetatarsal space. The K-wire is advanced just past the lateral cortex of the first metatarsal and remains there until it is advanced into the capital fragment once the osteotomy is complete.

Step 3. A small stab incision is made with a #64 Beaver blade distally along the metatarsal neck at the previously demarcated site for osteotomy.⁹ The osteotomy is then completed along this line and trajectory using a 2.0 mm x 13 mm straight burr (see Figure 3A–C). Once the osteotomy is complete, a small, curved hemostat (the authors prefer to use a Crile hemostat) is then introduced through the incision and used to translate the capital fragment laterally (see Figure 3C). This can be done by placing the hemostat into the medullary canal for translation. If greater correction is needed, place the hemostat at the lateral border of the first metatarsal and then translate. Simultaneously, the surgeon can obtain rotational correction in the frontal plane via supination of the thumb and radial fingers.

Step 4. With reduction maintained, the osteotomy is then provisionally fixated first by advancing the 1.6-mm K-wire distally into the capital fragment (see Figure 4A). In a parallel manner, a 1.4-mm K-wire is then placed distal to the 1.6-mm K-wire along the same trajectory, advancing across the osteotomy into the capital fragment. If further stabilization is needed, a “Siddiqui stabilization wire” can be placed across the capital fragment into the second metatarsal head (see Figure 4B). This wire stabilizes the sagittal plane position of the metatarsal head and prevents excessive dorsal or plantar translation. If additional lateral translation is needed to further reduce the intermetatarsal angle, the capital fragment can still be translated along that wire, which also can maintain the rotation after translation to realign the sesamoids.    

For the final fixation construct, make sure the proximal screw is bicortical before insertion into the capital fragment. Our preference is to use 4.0-mm and 3.5-mm screws for the two-screw construct (see Figure 5).

Step 5. The medial shelf is then cut by placing the burr into the medullary canal from the incision used to make the osteotomy. The medial corner is reduced using the burr and morselized pieces are placed into the osteotomy site as autograft (see Figure 6).  

Step 6. Finally, a Beaver blade is used to make a stab incision at the level of the base of the proximal phalanx medially. The burr is then inserted and brought to the lateral cortex of the proximal phalanx to create a wedge osteotomy, and fixation is then placed perpendicular to the osteotomy (see Figure 7).

Step 7 (Bonus Step). If needed, a lateral capsulotomy is made through a percutaneous incision at the first intermetatarsal space.

What the Postoperative Protocol Entails

Postoperatively, patients are placed in a flat surgical shoe and weight-bearing as tolerated is allowed, with care taken to avoid heel-toe propulsive gait. The patient can bear weight on the heel for comfort if preferred. The first postoperative visit is generally at 2 weeks, at which time patients are advanced to weight-bearing in supportive athletic shoe gear if edema and incision allow. The senior author prefers to get the patient into sneakers at 2 to 4 weeks, depending on swelling (see Figure 8 and Figure 9). At 10–12 weeks, impact activities can be started, dependent upon clinical and radiographic healing (see Figure 10). Anecdotally, pediatric patients tend to return to activity 2–3 weeks sooner. Most notably, our use of narcotic medication is limited to the first few days after surgery.

In Conclusion

The minimally invasive bunionectomy has come a long way since our previous publications^1,6 and has been modified over the years from publications by Bösch, Vernois and Redfern, Giannini, and Magnan.^4,5,7,12,13 We have transitioned away from using Steinmann pins for fixation and have moved toward screw fixation as demonstrated by others.⁷ Our patients report satisfaction and moreover, they are excited about being able to walk in a postoperative shoe immediately after surgery, then transitioning into sneakers within two weeks. Patients further attribute their satisfaction to the cosmetic incision, immediate postoperative weight-bearing, and return to full activity. The high rate of patient satisfaction directly contributes to the surgeon’s satisfaction, as does the decreased narcotic use and the reproducibility with this procedure.This minimally invasive surgery is a safe, reproducible, and viable method to correct hallux valgus. The procedure has been further validated in the literature to have equivalent healing and correction when compared with open bunionectomies.¹⁴ We continue to make improvements to this method, and these new advances in minimally invasive bunion surgery can be performed effectively if surgeons do not deviate from the surgical technique.

Dr. Thomas is a Fellow at the International Center for Limb Lengthening in the Rubin Institute for Advanced Orthopedics at Sinai Hospital of Baltimore.

Dr. Ravine is affiliated with the Division of Podiatry in Cambridge Health Alliance at Harvard Medical School Teaching Hospital in Cambridge, MA.

Dr. Siddiqui is the Chief of the Division of Podiatry at the International Center for Limb Lengthening at Rubin Institute for Advanced Orthopedics at Sinai Hospital of Baltimore. He is the Director of the Foot and Ankle Deformity Correction and Orthoplastics Fellowship and the Director of Podiatric Surgery at the International Center for Limb Lengthening at Rubin Institute for Advanced Orthopedics at Sinai Hospital of Baltimore. He is also the Chief of the Division of Podiatry at Northwest Hospital in Randallstown, MD.

References
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2.    Siddiqui NA, LaPorta GA. Minimally invasive bunion correction. Clin Podiatr Med Surg. 2018; 35(4):387–402.
3.    Siddiqui NA, Fink JN, Sharma P, D’Andelet A, LaPorta GA. Mechanical axis method to determine first intermetatarsal angle and tibial sesamoid position. J Foot Ankle Surg. [published online ahead of print April 4, 2022] doi: 10.1053/j.jfas.2022.03.013.
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