Do the outcomes of MIS justify the learning curve vs. open foot and ankle procedures?
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Click here to read the Cover Story, "Advances catalyze minimally invasive foot, ankle surgery."
Steep learning curve, complications
In the past decade, MIS foot and ankle procedures have undergone several advancements that make it an excellent option for various procedures.
MIS has gained popularity for procedures such as bunions, calcaneal osteotomies, Charcot plantar cheilectomies, combined first metatarsophalangeal arthroscopy/MIS cheilectomies and lesser metatarsal osteotomies. The benefits of using MIS have been supported throughout the literature. However, before diving into using MIS, it is important to acknowledge it is still not perfect and it comes with a steep learning curve, which has been described in several papers treating various pathologies. The learning curve associated with becoming proficient in MIS also translates to increased operative time as well as increased use of fluoroscopy.
In a study of 50 MIS chevron/Akin procedures, Ezequiel Palmanovich, MD, and colleagues evaluated the learning curve of a single surgeon inexperienced in MIS during the course of 3 years and found that it took approximately 27 procedures for an inexperienced surgeon to acquire the skill of performing minimally invasive chevron/Akin osteotomy. Surgery duration decreased from more than 2 hours in the initial cases to a mean of about 45 minutes in the third year.
A high learning curve also means potentially undesirable surgical outcomes for those surgeons who “dabble” in trying out MIS. As with all surgical techniques, complications exist, and the MIS literature has identified different types of poor outcomes specific to the technique. For example, Kar Hao Teoh, FEBOT, FRCS(T&O), and colleagues evaluated clinical outcomes following MIS cheilectomy in 98 cheilectomy procedures and described various complications, such as permanent numbness to the dorsomedial cutaneous nerve, revision cheilectomies and return to OR for removal of residual loose bodies. In their discussion, the authors comment on their personal learning curve with the procedure as a reason for their relatively high revision rate and incomplete bony resection earlier on in the series. In a later paper, Jorge Javier Del Vecchio, MD, and colleagues commented on how technique modification can help prevent these nerve complications, including blunt dissection to bone and ensuring proper burr size. Malunion, specifically plantar flexion of the capital fragment, has also been described and can easily occur if the fixation is not placed in the proper position immediately after the lateral translation of the distal metatarsal.
Although incisions for MIS are small and act as one of the main arguments for MIS procedures along with minimal soft tissue stripping, persistent drainage and delayed closure can occur. Michelle M. Coleman, MD, PhD, and colleagues specifically assessed risk factors of complications associated with MIS medial displacement calcaneal osteotomy in a consecutive single-surgeon series of 189 osteotomies and found that healing complications were present in 7% of cases during a 6-year study period. During this study period, there was a 12-month case cluster of osteotomy healing complications during which complication rates were 28%. Outside of this cluster healing, complication rates were 0.7%. The authors did not find a definitive cause for the case cluster, but based on the discussion, they suspected heat necrosis from the burr along with certain technique modifications to be involved.
The steep learning curve associated with MIS procedures should not preclude its use as MIS has some advantages vs. open surgery based on the surgeon’s training and experience. To optimize MIS operative outcomes and master surgical techniques, a surgeon unfamiliar with MIS systems should gain knowledge at instructional courses and cadaver labs.
- References:
- Coleman MM et al. Foot Ankle Int. 2021;doi:10.1177/1071100720961094.
- Del Vecchio JJ et al. Foot Ankle Int. 2019;doi:10.1177/1071100719846070.
- Palmanovich E, et al. J Foot Ankle Surg. 2020;doi:10.1053/j.jfas.2019.07.027.
- Teoh KH, et al. Foot Ankle Int. 2019;doi:10.1177/1071100718803131.
Eric Giza, MD, is a professor of orthopedic surgery, and Yvonne Conway, MD, is a foot and ankle fellow at the University of California, Davis in Sacramento, California.
Expertise needed in open techniques
MIS of the foot and ankle aims to accelerate postoperative recovery time, allow early weight-bearing, decrease postoperative pain and complications, and minimize surgical scars. Because the goal of MIS is to perform the indicated procedure through the smallest possible incision with minimal soft-tissue injury, surgeons must adopt special instrumentation and learn new surgical techniques. As with any new surgical technique and set up surgical tools, the implementation of MIS is associated with a learning curve.
Although each MIS procedure may be associated with a different learning curve, it is widely accepted that the number of cases required to reach technical proficiency in MIS of the foot and ankle ranges from 27 to 40. In a systematic review, Anthony N. Baumann, DPT, and colleagues reported an average of 35.5 surgeries were needed to reach the plateau phase of the learning curve of MIS for hallux valgus. This is similar to the learning curve of open orthopedic surgical procedures, including ACL reconstruction and shoulder arthroplasty, which may range from 20 to 50 cases. Hence, it can be argued that MIS procedures of the foot and ankle are not associated with an excessively long learning curve.
In many scenarios, MIS of the foot and ankle is comparable to open surgery in terms of clinical and radiographic outcomes. There is growing evidence in the literature supporting MIS over open foot and ankle surgery in decreasing early postoperative pain, wound complications and improving patient satisfaction. In a randomized controlled trial of 50 patients undergoing bunion correction with either scarf osteotomy or MIS chevron/Akin procedure, Moses Lee, MD, and colleagues demonstrated both groups had similar corrections in the hallux valgus and intermetatarsal angles, whereas the MIS group had markedly less pain in the first 6 weeks. Adrian R. Kendal, MA, BMBCh, MRCS, DPhil, and colleagues compared MIS with open calcaneal osteotomy in a group of 81 patients and found markedly fewer wound complications in the MIS group. In a prospective, randomized controlled trial of patients with hallux valgus deformity, Gerhard Kaufmann, MD, and colleagues found no difference between MIS and open chevron osteotomy in terms of VAS of pain, American Orthopaedic Foot & Ankle Society forefoot score, radiographic outcome measures and range of motion. Regarding patient satisfaction, statistically significant differences were found between MIS and open surgery 12 weeks postoperatively in favor of the MIS group.
Paralleling technological advances, MIS techniques are rapidly expanding in foot and ankle surgery. Surgeons should have expertise in traditional open techniques before exploring MIS alternatives. It is crucial to take hands-on MIS courses to gain exposure and develop the skills needed to use MIS techniques. Safely performed MIS may provide comparable outcomes, limited complications and improved patient satisfaction.
- References:
- Avendano JP, et al. JSES Rev Rep Tech. 2022;doi:10.1016/j.xrrt.2022.12.001.
- Baumann AN, et al. Foot Ankle Surg. 2023;doi:10.1016/j.fas.2023.07.012.
- Kaufmann G, et al. Int Orthop. 2019;doi:10.1007/s00264-018-4006-8.
- Kendal AR, et al. Foot Ankle Int. 2015;doi:10.1177/1071100715571438.
- Lausé GE, et al. J Am Acad Orthop Surg. 2023;doi:10.5435/JAAOS-D-22-00608.
- Lee M, et al. Foot Ankle Int. 2017;doi:10.1177/1071100717704941.
- Luthringer TA, et al. Phys Sportsmed. 2016;doi:10.1080/00913847.2016.1154448.
- Toepfer A, et al. Foot Ankle Surg. 2022;doi:10.1016/j.fas.2022.07.006.
Christopher E. Gross, MD, is a professor of orthopedic surgery and director of foot and ankle division, and Kivanc Atesok, MD, MSc, is a foot and ankle surgery fellow at the Medical University of South Carolina in Charleston, South Carolina.
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