Why Would You Cut The Plantar Fascia To Prevent Diabetic Foot Ulcerations?

I recently participated in a discussion on LinkedIn after a young podiatrist posted a video demonstrating a percutaneous plantar fasciotomy performed on a patient with diabetes. I inquired why the practitioner would ever cut the plantar fascia and the response was that this patient had a previous ulceration under the first metatarsal and that the plantar fasciotomy was an attempt to offload the metatarsal to prevent future ulceration. This podiatrist cited a Level IV study reporting outcomes of the procedure.¹   

Several other young podiatric surgeons posted their support of the practice of cutting the plantar fascia in patients with diabetes in order to treat or prevent foot ulcerations. This discussion suggested to me that podiatric medical education and surgical training programs may be failing to teach the importance of the plantar fascia for healthy foot function and reduction of plantar pressure in the forefoot of patients with diabetes.

It turns out that the study cited by the young podiatrist in his post described a new technique of a “selective” percutaneous plantar fasciotomy performed at the level of the Lisfranc joint to treat active non-healing ulcerations.¹ It was not a procedure intended to prevent re-ulceration. 

There were many shortcomings to this study, including the fact that the study authors performed the selective plantar fasciotomy as a treatment for ulcerations on the digits as well as under the metatarsals. The pathomechanics and offloading strategies are entirely different for an ulceration under the head of the proximal phalanx of the hallux versus the plantar aspect of the head of a metatarsal. Also, 50 percent of the patients in this study had a tendo-Achilles lengthening procedure (TAL) in addition to the selective plantar fasciotomy so one cannot entirely attribute the end result of wound healing to the plantar fascia release.

As expected, the selective plantar fascia release, performed with or without a tendo-Achilles lengthening, seemed to work better for healing ulcers located on the plantar surface of a toe in comparison to ulcers located on the plantar aspect of a metatarsal head.¹ Cutting the plantar fascia will negate the function of the plantar plate and result in a floating toe. A floating toe without plantar purchase may exert less pressure on a plantar ulcer located on the head of the proximal phalanx but the subsequent transfer of load to the forefoot has significant negative consequence to the high-risk foot. Furthermore, this study showed that despite the surgical procedures, healing failed to occur in 40 percent of the digital ulcers and 66 percent of the metatarsal ulcers.¹

Attempting to rationalize a partial plantar fasciotomy to offload a metatarsal ulceration, the study authors said they believed the procedure would weaken the windlass effect on the selected toe and decrease the pressure under the metatarsal head during walking.¹

The validity of this assumption is contradicted by several important studies that show that plantar loads on the metatarsal actually increase after plantar fasciotomy. Sharkey and coworkers showed that after a plantar fasciotomy, dorsal bending moments actually increased in the metatarsals.² Additionally, they concluded that the plantar fascia, inserting on the digits via the plantar plate, provides significant stability and resistance to dorsally directed ground reaction forces during terminal stance and pre-swing.   

Hamel and coworkers performed a plantar fasciotomy and observed significant loss of load bearing of the digits due to lack of engagement of the windlass mechanism.³ The windlass mechanism increases tension in the plantar fascia as the toes dorsiflex at the metatarsophalangeal joints.⁴ When loading the plantar fascia in the weightbearing foot, tension in the plantar fascia will provide plantarflexion moment to the digits across the metatarsophalangeal joints. The result is increased plantar purchase of the digits and shielding of the adjacent metatarsal from dorsally directed ground reaction forces. 

This contradicts the assumption made by Kim and colleagues that weakening the windlass mechanism via plantar fasciotomy would actually decrease pressure under the metatarsal.¹ Unfortunately, Kim and coworkers did not perform plantar pressure measurements as they likely would have seen the transfer of increased load to the metatarsals as documented by other studies.^2,3

What The Literature Reveals About The Impact Of Plantar Fasciotomy On Digital Stability And The Plantar Fat Pad

To answer any question about the sequela of plantar fasciotomy on stability of the toes, one only needs to look at the profound effects of plantar plate rupture.^5-7 This has led most authorities on reconstructive foot and ankle surgery to conclude that the plantar fascia, via the plantar plate, is the most important structure to provide static stability to the toes.^8-10

Besides providing essential plantar purchase and load bearing by the digit, the plantar fascia anchors to the distal plantar fat pad to prevent migration resulting from shear forces during heel rise.¹¹ Sharkey and coworkers propose that after plantar fasciotomy, the plantar fat pad destabilizes under the metatarsals and migrates anteriorly as seen in the rheumatoid foot.² Elaborating further, Sharkey and colleagues note that after a plantar fasciotomy: “Tissues formerly located under the metatarsal heads, and modeled to accommodate and distribute the higher forces in these regions, are translated forward and replaced by tissues normally located more posteriorly.”

In the diabetic foot, loss of digital stability is the primary cause of elevated plantar pressures under the metatarsals.^12,13 A series of studies conducted by Bus and colleagues showed that anterior migration of the plantar fat pad, accompanied by digital deformity in patients with diabetes, is strongly associated with increased plantar pressure under the heads of the metatarsals.^14,15

In Conclusion

Given this large body of research validating the role of the intact plantar fascia to facilitate load sharing of the digits and reduce plantar pressure under the heads of the metatarsals, I will continue to question why anybody would cut the plantar fascia to prevent diabetic foot ulcerations.

Dr. Richie is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is a Fellow and Past President of the American Academy of Podiatric Sports Medicine. Dr. Richie is a Fellow of the American College of Foot and Ankle Surgeons, and the American Academy of Podiatric Sports Medicine. 

References  

1. Kim JY, Hwang S, Lee Y. Selective plantar fascia release for nonhealing diabetic plantar ulcerations. J Bone Joint Surg Am. 2012;94(14):1297-1302.
2. Sharkey, NA; Donahue, SW; Ferris, L. Biomechanical consequences of plantar fascial release or rupture during gait - Part II: Alterations in forefoot loading. Foot Ankle Int. 1999;20(2):86-96.
3. Hamel AJ, Donahue SW, Sharkey NA. Contributions of active and passive toe flexion to forefoot loading. Clin Orthop Relat Res. 2001;393:326-334
4. Hicks JH. The mechanics of the foot: II. The plantar aponeurosis and the arch. J Anat. 1954;88(1):25–30.
5. Suero EM, Meyers KN, Bohne WHO. Stability of the metatarsophalangeal joint of the lesser toes: A cadaveric study. J Orthop Res. 2012;30(12):1995–1998.
6. Bhatia D, Myerson MS, Curtis MJ, Cunningham BW, Jinnah RH. Anatomical restraints to dislocation of the second metatarsophalangeal joint and assessment of a repair technique. J Bone Joint Surg Am. 1994;76(9):1371–1375.
7. Chalayon O, Chertman C, Guss AD, Saltzman CL, Nickisch F, Bachus KN. Role of plantar plate and surgical reconstruction techniques on static stability of lesser metatarsophalangeal joints: A biomechanical study. Foot Ankle Int. 2013;34(10):1436–1442.
8. Barca F, Acciaro AL. Surgical correction of crossover deformity of the second toe: A technique for tenodesis. Foot Ankle Int. 2004;25:620-624.
9. Deland JT, Lee KT, Sobel M, DiCarlo EF. Anatomy of the plantar plate and its attachments in the lesser metatarsal phalangeal joint.  Foot Ankle Int. 1995;16(8):480-486.
10. Ford LA, Collins KB, Christensen JC. Stabilization of the subluxed second metatarsophalangeal joint: flexor tendon transfer versus primary repair of the plantar plate. J Foot Ankle Surg. 1998;37(3):217-222.
11. Bojsen-Moller F, Flagstad KE. Plantar aponeurosis and internal architecture of the ball of the foot. J Anat. 1976;121(Pt 3):599-611. 
12. Lavery LA, Armstrong DG, Vela SA, Quebedeaux TL, Fleischli JG. Practical criteria for screening patients at high risk for diabetic foot ulceration. Arch Intern Med. 1998;158(2):157–162.
13. Holewski JJ, Moss KM, Stess RM, Graf PM, Grunfeld C. Prevalence of foot pathology and lower extremity complications in a diabetic outpatient clinic. J Rehab Res Dev. 1989;26(3):35–44.
14. Bus SA, Maas M, Cavanagh PR, Michels RP, Levi M. Plantar fat pad displacement in neuropathic diabetic patients with toe deformity: a magnetic resonance imaging study. Diabetes Care. 2004;27(10):2376-2381.
15. Bus S, Maas M, de Lange A, Michels R, Levi M. Elevated plantar pressures in neuropathic diabetic patients with claw/hammer toe deformity. J Biomech. 2005;38(9):1918–1925.