Custom Foot Orthotics After Arthrodesis of the Foot and Ankle

We have noted a growing prevalence in foot and ankle arthrodesis procedures including of the first metatarsophalangeal joint (MTPJ), tarsometatarsal joint, ankle, and triple arthrodeses. As one artificially unites 2 bones, there are resultant gait changes to consider beforehand. To account for these biomechanical changes, we feel it is imperative to consider modifications in shoe gear and the use of custom foot orthotics. This also requires a patient-specific approach.
 
In this blog, we aim to provide a general review of different shoe gear modifications that, along with use of custom orthotics, may help compensate for gait changes after foot and ankle arthrodesis procedures.

Focusing on First MTPJ Fusion

The first MTPJ absorbs a large part of ground reactive forces, as it is involved in propulsion during gait. Approximately 55–65 degrees of hallux dorsiflexion is required in gait.¹ During static stance the first metatarsal carries 40% of one’s body weight.¹ The first MTPJ absorbs 60–80% of one’s weight when propelling.² When there is loss of range of motion at the first MTPJ, compensation occurs via two mechanisms:²

• External rotation of the hips and feet, propelling off the lateral aspect of the heel, followed by the forefoot
• Propulsion off the lesser metatarsal heads 

To compensate for changes in the gait after first MTPJ arthrodesis, one may consider a carbon fiber plate insert. This accounts for heel-to-forefoot drop, thereby acting like a rocker sole.³ Therefore, the majority of the ground reactive forces are absorbed by the shoe gear.³ Another consideration is the use of a Morton's extension, which functionally may again allow one to propulse off the first MTP more evenly. Munteanu and colleagues demonstrated in their randomized assessor, blinded style study that carbon fiber inserts were superior in outcomes to sham type inserts to reducing pain and patients favoring the carbon fiber insert.³ Lastly, one can also consider modifying the shoe and adding a rigid rocker sole.

Thoughts on Considerations Related to Lapidus Arthrodesis

While the motion at the first tarsometatarsal joint is limited, one of the indications for an arthrodesis at this joint is hypermobility. Therefore, we have noted an increase in the number of Lapidus arthrodesis in recent times for hallux valgus deformity, midfoot arthritis, hypermobility of the first ray and post traumatic arthritis. After union of the first metatarsal base and the medial cuneiform, we find the foot does not lose a large amount of motion. The biomechanics of the first ray don’t change significantly, as one is still able to propel off the first MTPJ.⁴ One additional consideration to take into account is that the peroneus longus causes significant frontal plane eversion after a Lapidus procedure, and that there is also an increase in efficiency of the peroneus longus.⁴ Custom foot orthotics may be indicated to support the midtarsal joint to redistribute weight, stress and ground reactive forces.

What to Keep in Mind for Isolated Tibiotalar Arthrodesis

Post-traumatic arthritis, osteoarthritis, inflammatory arthritis, angular deformities due to ligament insufficiency are amongst some of the reasons that one may undergo tibiotalar arthrodesis. When assessing joint motion, one must keep in mind that the ankle is a triplanar, highly congruent joint with unique surface anatomy. Our goal after an ankle fusion is to allow for heel strike and propulsion off the midtarsal joint.
 
A solid ankle, cushioned heel (SACH) modification to a shoe is going to compress and allow one to ambulae without applying to much stress at the ankle fusion site. It is able to allow an individual with a fused ankle to do this because it has a midfoot rock to it. One can shorten their stride length by propelling off the first MTPJ, but since the ankle joint is locked up in an arthrodesis, using a SACH modification may be beneficial for these individuals.⁵
 
A second option is to use an ankle-foot orthotic (AFO) gauntlet brace.⁶ A gauntlet-type brace would provide stability to the ankle fusion site and allow an individual to rock off the midtarsal joint for propulsion.⁶

Triple Arthrodesis Considerations

Triple arthrodesis remains one of the mainstays of treatment for hindfoot arthritis, advanced pes planus, and pes cavus deformities. Individuals with a triple arthrodesis will lose motion predominantly in the frontal and transverse planes, and a few biomechanical options are available, in our experience:
 

• We typically choose a rigid rocker sole in these individuals. This allows one to propulse after heel strike. A gauntlet AFO device may again help redistribute pressure.
• Another consideration for these patients is that the ankle joint may start to adapt during gait, undertaking greater stress. One way to allow for better stability at the ankle joint after a triple arthrodesis may be through the use of a Richie-type brace. We hypothesize that the use of a Richie brace would allow for better impaction, thereby potentially reducing the risk of periarticular joint arthritis.
• Custom foot orthotics remain a mainstay of treatment in our practice for these cases.

Choices After Tibiotalocalcaneal Arthrodesis

Tibiotalocalcaneal arthrodesis remains an effective salvage procedure for complex hindfoot and ankle deformities in foot and ankle surgery. Chou and team demonstrated in their cohort of 55 patients that the average AOFAS score was 66.⁷ They found that 48/55 of these patients were satisfied with their outcomes.⁷ Tibiotalocalcaneal arthrodesis is also a reasonable alternative to amputation for the treatment of a non-braceable, neuropathic, degenerative hindfoot and ankle. We have noted its growing popularity of use, particularly in individuals diagnosed with stage IV Sanders/Frykberg classification of Charcot neuroarthropathy. Once the hindfoot and ankle joint have fused, individuals may complain of stiffness.⁷ One consideration is to add a rocker sole with a SACH modification. While these individuals may have compensation at the midtarsal joint, this often may not be enough to allow them to propel through the midstance phase of gait and may as a result, increase stress along the fused ankle joint. Therefore, adding a rocker sole with a SACH modification will allow them to propel with less stress over the fused ankle joint.⁵ This may be a good alternative for individuals who complain of stiffness after tibiotalocalcaneal arthrodesis, particularly in non-neuropathic patients, as the SACH modification gives cushion along the subtalar join and adding a midfoot rocker can provide support to the midtarsal joint.⁵

In Conclusion

There is a growing number of fusion procedures being performed by foot and ankle surgeons. In a study by Best and colleagues, they demonstrated a 146% increase in arthrodeses being performed between 1994 and 2006, per capita.⁸ The population-adjusted rate increased by 416%.⁸ This study effectively demonstrates the growing prevalence in foot and ankle arthrodesis. While it remains a mainstay as a treatment choice for a wide variety of pathology, considerations should be given to foot and ankle accommodative devices after surgery. The consideration of custom foot orthotics, and devices such as Richie braces, gauntlet AFOs, SACH modifications, rocker soles, and carbon fiber plates may help reduce pain, improve function and ultimately improve patient satisfaction.

Dr. Shamim is the current fellow at the Northwest Illinois Foot & Ankle Fellowship in Illinois. He is board qualified by the American Board of Foot & Ankle Surgery in Foot and Reconstructive Rearfoot and Ankle Surgery.

Michael Fishkin is a board certified Pedorthotist at the Northern Illinois Foot and Ankle Specialists in Illinois.

Dr. McEneaney is a Diplomate of the American Board of Foot and Ankle Surgery, President of the Illinois Podiatric Medical Association and Co-Director of the Northwest Illinois Foot and Ankle Foundation Fellowship. He is a Fellow of the American College of Foot and Ankle Surgeons and is the owner and CEO of Northern Illinois Foot and Ankle Specialists.

References
1.    Halstead J, Redmond AC. Weight-bearing passive dorsiflexion of the hallux in standing is not related to hallux dorsiflexion during walking. J Orthop Sports Phys Ther. 2006;36(8):550-6. doi: 10.2519/jospt.2006.2136. PMID: 16915976.
2.    Allan JJ, McClelland JA, Munteanu SE, et al. First metatarsophalangeal joint range of motion is associated with lower limb kinematics in individuals with first metatarsophalangeal joint osteoarthritis. J Foot Ankle Res. 2020;13(1):33. doi: 10.1186/s13047-020-00404-0. PMID: 32513212; PMCID: PMC7278053.
3.    Munteanu SE, Landorf KB, McClelland JA, et al. Shoe-stiffening inserts for first metatarsophalangeal joint osteoarthritis: a randomised trial. Osteoarthritis Cartilage. 2021;29(4):480-490. doi: 10.1016/j.joca.2021.02.002. Epub 2021 Feb 12. PMID: 33588086.
4.    Bierman RA, Christensen JC, Johnson CH. Biomechanics of the first ray. Part III. Consequences of Lapidus arthrodesis on peroneus longus function: a three-dimensional kinematic analysis in a cadaver model. J Foot Ankle Surg. 2001;40(3):125-31. doi: 10.1016/s1067-2516(01)80077-6. PMID: 11417593.
5.    Wu WL, Rosenbaum D, Su FC. The effects of rocker sole and SACH heel on kinematics in gait. Med Eng Phys. 2004;26(8):639-46. doi: 10.1016/j.medengphy.2004.05.003. PMID: 15471691.
6.    Feger MA, Donovan L, Hart JM, Hertel J. Effect of ankle braces on lower extremity muscle activation during functional exercises in participants with chronic ankle instability. Int J Sports Phys Ther. 2014;9(4):476-87. PMID: 25133076; PMCID: PMC4127510.
7.    Chou LB, Mann RA, Yaszay B, et al. Tibiotalocalcaneal arthrodesis. Foot Ankle Int. 2000;21(10):804-8. doi: 10.1177/107110070002101002. PMID: 11128009.
8.    Best MJ, Buller LT, Miranda A. National Trends in Foot and Ankle Arthrodesis: 17-Year Analysis of the National Survey of Ambulatory Surgery and National Hospital Discharge Survey. J Foot Ankle Surg. 2015;54(6):1037-41. doi: 10.1053/j.jfas.2015.04.023. Epub 2015 Jul 26. PMID: 26213159.

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