Modern minimally invasive bunion surgery allows smaller incisions and facilitates easier recovery for patients. Accordingly, this author reviews surgical techniques, proper patient selection, insights from the literature and potential complications.
Minimally invasive bunion surgery offers several advantages over traditional bunionectomy. Modern advances in minimally invasive bunion surgery techniques and technology have allowed for tiny incisions, a walking recovery, less postoperative pain, shorter operative time and an overall easier recovery. The main advantage of minimally invasive bunion surgery is the ability to perform a bunion correction with minimal disruption or trauma to the overlying skin and soft tissue. It is important to properly determine which patients/bunions will benefit from a minimally invasive approach.
The term “minimally invasive bunion surgery” is an extremely vague term that can encompass a variety of bunion correction methods and incisional approaches. Surgeons often use the term minimally invasive interchangeably with “percutaneous” surgery, though they represent somewhat different methods.1
Nonetheless, minimally invasive bunion surgery is loosely defined as a “bunion correction” using very small or tiny incisions (percutaneous incisions) rather than typical large incision(s) with traditional open methods. Minimally invasive incisions usually range from 1/8⅛ inch to ½ inch whereas traditional bunion surgery incisions range from 2 inches to 6 inches (see photo 1). Accordingly, the minimally invasive aspect of the bunion surgery should really only refer to the incisional approach of accessing the bone through these small portal-like incisions rather than the particular method in which one corrects the bunion.
Surgeons can perform most of the common methods of bunion correction with minimally invasive techniques. Depending on the severity of the bunion, correction occurs with a variety or combination of different methods involving bone shaving, bone cutting (realignment osteotomy) and/or bone mending (fusion). The most common bone correction for bunions regardless of incisional approach is realignment osteotomy (distal metatarsal osteotomy) and now surgeons can successfully execute this procedure with minimally invasive techniques.
One would perform minimally invasive bunion surgery with specialized instruments that allow bony correction through these small incisional portals. The surgeon uses tactile senses and real-time intraoperative fluoroscopy to visualize the bone cutting, realignment and stabilization of bony segments. Additionally, with minimally invasive techniques, one would generally use small cone-shaped, high speed bone burs to cut and shave the bone(s) rather than using large flat bone saws (as with a traditional bunionectomy).
What You Should Know About Minimally Invasive Bunion Shaving
Bunion shaving is the simplest of bunion correction methods and surgeons have long performed it with minimally invasive techniques. Since a bunion is caused by a bone malalignment rather than a bone growth, simple bunion shaving has limited use in modern bunion surgery.
However, surgeons routinely perform bunion shaving along with other bone realignment techniques and do not generally perform bunion shaving as an isolated procedure. Nonetheless, there are situations that arise when this procedure is useful (see photo 2). One may do a percutaneous lateral release in conjunction with bone shaving.
Keys To Performing A Minimally Invasive Realignment Osteotomy
When it comes to realignment osteotomy, we have seen the most technological advances with minimally invasive bunion surgery. The basic concept for minimally invasive realignment osteotomy is the same as that of open traditional osteotomy. Cut the bone near the top of the metatarsal bone, realign the bone to a corrected position and fixate it with surgical hardware. However, minimally invasive surgery modifies the bone cut and involves different fixation methods.
The location of the osteotomy is further back on the metatarsal bone than a traditional metatarsal head osteotomy. The bone cut should be at the metatarsal neck, just proximal to the sesamoids, allowing one to reposition the entire big toe joint complex as a single unit. Modify the configuration of the osteotomy to a vertical cut or an “L or V” cut with a dorsal linear segment and an oblique plantar segment. Adding a small plantar shelf allows for more bone to bone contact for healing and may also provide some intrinsic stability to the osteotomy.
As with any bunion surgery, surgical hardware helps stabilize the bones and maintain the corrected position until bone healing occurs. While some early techniques have been performed without any fixation whatsoever, most surgeons would agree that fixation is preferable for an osteotomy. Surgeons have used percutaneous Kirschner wires, which span the osteotomy but lack in construct rigidity. Alternatively, surgeons have used larger percutaneous K-wires or Steinmann pins that stabilize the construct by engaging the medial soft tissues and reside in the metatarsal canal (see photo 3). There are a variety of percutaneous screw placements and currently the most stable constructs involve screw(s) oriented from the proximal medial first metatarsal into the laterally translated metatarsal head (see photo 4). Newer modern screws are designed for a minimally invasive realignment osteotomy with heads that are lower profile and screw pitches that are better suited for this osteotomy.
What The Literature Reveals About Minimally Invasive Bunion Surgery
Minimally invasive bunion surgery techniques have been evolving over the past two decades, making it challenging to do comparative studies. However, we can garner much by looking at the studies both individually and collectively. With a renewed interest in minimally invasive techniques by both surgeons and patients, more studies have been performed in recent years.
Surgeons have been performing percutaneous bunionectomy since the 1940s.2 The basis for minimally invasive bunion surgery traces back to the Kramer osteotomy, in which one stabilizes a laterally translated distal metatarsal osteotomy with a K-wire within the medial soft tissues extending to the proximal metatarsal canal. It was not until the early 1990s that Bösch and colleagues performed a percutaneous subcapital modified Kramer osteotomy.3,4 Magnan introduced a high speed power bur for the metatarsal osteotomy.5 Vernois and Redfern’s contribution to minimally invasive bunion surgery introduced stable screw fixation along with a subcapital osteotomy.6
In 2005, Magnan and coworkers looked at 118 consecutive percutaneous distal osteotomies (in 82 patients) for mild to moderate hallux valgus.7 Ninety-one percent of patients were satisfied and there was significant improvement in radiographic measures. Sixty-one percent of the patients had dorsal or plantar displacement of the capital fragment. Complications included hallux valgus recurrence in three patients, first metatarsophalangeal joint (MPJ) stiffness in eight patients and one deep infection.
Gianni and colleagues popularized the SERI (simple, effective, rapid, inexpensive) technique with their prospective study of 1,000 feet with hallux valgus in 2013.8 They demonstrated a statistically significant average increase in American Orthopaedic Foot and Ankle Society (AOFAS) score from 47 preoperatively to 89 postoperatively. In this large series of patients, there were no nonunions and all patients had complete healing of the osteotomy. Hallux varus did not occur and no deep wound infection occurred despite the presence of a 2 mm percutaneous K-wire, which surgeons removed at 30 days. In 2013, Vernois and Redfern radiographically analyzed 100 feet with hallux valgus after a minimally invasive chevron and Akin osteotomy and demonstrated a mean correction of 9 degrees.6 The mean preoperative intermetatarsal angle was 14.5 degrees and 7.3 degrees postoperatively.
In 2013, Ianno and colleagues reported on 85 feet with hallux valgus using the Bösch technique with a statistically significant improvement in AOFAS scores and radiographic measures.9 Patients had a high complication rate of 29.4 percent, which included three cases of avascular necrosis and 16 recurrences. Brogan and coworkers reported on combined screw and K-wire fixation in 45 consecutive patients with symptomatic hallux valgus.10 There was a low rate of complications with 2 percent requiring repeat operation.
In 2017, Jowett and Bedi published their results of a prospective study of a single surgeon’s first 106 consecutive procedures for symptomatic hallux valgus using the minimally invasive chevron/Akin technique.11 Eighty-seven percent of patients were satisfied. Fourteen percent of patients had prominent hardware, scar sensitivity, nonunion and recurrence. The authors also identified that nearly twice as many complications or postoperative events were in the surgeon’s first 53 patients, further illustrating the steep learning curve of minimally invasive bunion surgery.
In a retrospective study, Maffulli and coworkers compared 36 scarf osteotomies to 36 minimally invasive Bösch technique osteotomies for hallux valgus with similar radiographic results.12 The mean operative time was significantly less in the minimally invasive group. Three pin tract infections occurred with the minimally invasive group. Radwan and Mansour compared the percutaneous distal metatarsal osteotomy versus an open chevron osteotomy for patients with mild to moderate hallux valgus, and both groups had improved AOFAS scores.13 However, patients who had minimally invasive surgery were happier with the cosmetic results (89.6 percent versus 64.5 percent respectively).
In a prospective randomized study of 50 patients with hallux valgus published in 2017 by Lee and colleagues, the authors compared the percutaneous chevron/Akin to open scarf/Akin up until six months postoperatively.14 Both groups demonstrated good to excellent clinical and radiographic results although fewer patients in the percutaneous group had perioperative pain. Lai and coworkers also compared percutaneous chevron/Akin osteotomy (29 feet) to open scarf/Akin osteotomy (58 feet) for hallux valgus at a 24-month follow-up.15 Both groups demonstrated comparable radiographic outcomes. Three patients in the open osteotomy group developed wound complications whereas the percutaneous group did not have any wound complications and had less pain perioperatively. In a randomized controlled trial of 47 patients in 2018, Kaufmann and colleagues demonstrated a significantly significant improvement in patient satisfaction with the minimally invasive chevron osteotomy versus an open technique for hallux valgus.16
The overall consensus seems to be that minimally invasive techniques provide radiographic outcomes and patient satisfaction rates that are at least similar or better than those of open procedures. Some evidence suggests that patients are happier with the cosmetic result and experience less pain perioperatively. Larger randomized controlled trials are needed and likely underway.
Which Patients Are The Best Candidates For Minimally Invasive Bunion Surgery?
Most bunions are amenable to minimally invasive techniques. However, surgeon experience and skill level dictates what one may achieve with these techniques. Moderate bunions seem to be the sweet spot in terms of surgical ease of correction. Small and large bunions may be more challenging for inexperienced surgeons. For small bunions, in which translation of the capital fragment is limited, it may be more difficult to orient surgical hardware. Large bunions require significant translations and stable fixation.
Any patient with a bunion may be a candidate for minimally invasive bunion surgery. The procedure is ideal for healthy, active, responsible patients. Patients with arthritis of the big toe joint may require different procedures. Depending on the method of minimally invasive bunion surgery, some patients may not be the best candidates.
As with any bone surgery, patients who smoke remain at risk for delayed bone healing though smoking is not an absolute contraindication. Consider bone quality as patients with osteopenia or osteoporosis may require a more restrictive postoperative course and/or immobilization. Patients with diabetic neuropathy should have careful monitoring and probably be immobile. Non-adherent patients always have problems after any bunionectomy.
What Are The Potential Complications?
Minimally invasive bunion surgery is not immune to postoperative complications, just like traditional open bunionectomy. Minimally invasive surgery amplifies some complications and lessens others. Surgeons not familiar with these advanced techniques experience more complications during the “learning” period.
Experienced surgeons have even abandoned the procedure (percutaneous Kirschner wire Bösch method) due to an “unacceptable rate of complications” as researchers noted in one study of mild to moderate hallux valgus.17 It is clear that the learning curve is steep.
In a systematic review of percutaneous osteotomies involving 18 studies and a total of 1,594 feet with hallux valgus, Bia and colleagues identified the following complication rates: infection (1.6 percent, K-wire cases only), recurrence (1.8 percent), nonunion (0.4 percent, K-wire cases only), complex regional pain syndrome (0.9 percent, K-wire and unfixated cases), transfer metatarsalgia (1.2 percent, mostly unfixated cases), osteonecrosis (0.1 percent, K-wire cases only) and joint stiffness (1.9 percent, K-wire and unfixated cases).1
The use of screw fixation in minimally invasive bunion surgery appears to offer far fewer complications in comparison to the percutaneous K-wire technique. Surgeon experience may reduce complications.
Minimally invasive bunion surgery is an excellent method for bunionectomy in the hands of an experienced surgeon. A minimally invasive realignment osteotomy with screw fixation appears to be the best method of correction with fewer complications and better outcomes. The procedure and technique will continue to evolve as more specialized instruments and surgical screws emerge. Nonetheless, today’s minimally invasive bunion surgery allows for a walking recovery, tiny incisions and an overall easier recovery.
Dr. Blitz, the creator of the Bunionplasty® procedure, is in private practice in both Midtown Manhattan, New York and Beverly Hills, Calif. He is board-certified by the American Board of Foot and Ankle Surgery, and is a Fellow of the American College of Foot and Ankle Surgeons. To learn more about minimally invasive bunion surgery, visit www.bunionplasty.com.
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