The Development of Postoperative Forefoot Ulcerations in Patients Who Underwent a Transmetatarsal Amputation Alone or in Combination with an Achilles Tendon Lengthening Adjunctive Procedure

1,3Mark Bullock, DPM, 1Christopher Gill, DPM, 1Andrew Cohen, DPM, 2John Blebea MD, 1Derek Tesoro, DPM, 1Eric Gaughan, DPM, 1Randy Semma, DPM, 3Danielle Duncan, MD1: Department of Podiatry, Central Michigan University Medical Education Partners; 2: Chair of Surgical Disciplines, Central Michigan University; 3: Covenant Healthcare Orthopedics, Saginaw MI

Statement of PurposeThe primary purpose of this study is to examine the rate of neuropathic forefoot ulceration development in patients who underwent a transmetatarsal amputation (TMA) alone compared to patients who received an additional Achilles lengthening (TAL) procedure. The hypothesis is that using a TAL with TMA will significantly reduce the risk of developing forefoot ulcerations.

Level of EvidenceLevel III

Literature ReviewA TMA creates an imbalance in musculature due to loss of digital extensors, which favors the pull of the Achilles tendon. The unopposed action of the triceps surae results in an equinovarus deformity (McCallum & Tagoe 2012). The resulting decrease in ankle joint dorsiflexion leads to an increase in forefoot plantar pressure, which puts the patient at risk for plantar forefoot ulcerations. Armstrong, et al. (1999) has shown that there is a decrease in peak plantar forefoot pressure with significant increase in ankle joint dorsiflexion when a TAL procedure is performed. Barry, et al. (1993) performed 33 TAL procedures to address chronic forefoot ulcerations after a TMA. They found that 91% of these chronic ulcerations went on to completely heal. Attinger, et al. (2003) found a reduction in rate of re-ulceration after a TMA from 50% to 4% when using either a TAL procedure or a tendon transfer prophylactically. However, La Fontaine and his colleagues (2008) found that 16 of 28 patients who underwent a TAL after TMA developed a new or recurrent ulceration(s). Prophylactic TAL with TMA is often recommended in our profession, but there is little published data to support its use. The aim of this study is to examine the use of the TAL procedure as an adjunct to TMA in reducing forefoot ulcer development.

Methods• 110 feet from 6 different surgeons were identified and examined for development of plantar forefoot ulcerations after a TMA. • 35 of the 110 feet had an additional TAL procedure. All surgeons who performed the TAL procedure did so routinely using a 3-incision technique, with two medial incisions and one lateral incision.• Data was collected from January 1, 2015 through January 1, 2021 using retrospective chart reviews as well as phone interviews in a questionnaire format. • Secondary outcomes were also examined, including but not limited to more proximal amputations, death, Achilles tendon infection and/or rupture, neuropathic plantar heel ulcers, posterior heel ulcers, BMI and HbA1c.• A Chi-square test was used to calculate the p-value and level of significance of the primary outcome.• Non-parametric Fischer’s Exact Test and Parametric Independent Sample’s t-test were used to examined secondary outcomes.• All data was analyzed using the Statistical Package for the Social Sciences (SPSS).

Results (Continued)• 25.3% (19/75) of cases that had a TMA alone were found to develop plantar forefoot ulcers after surgery, compared to 2.8% (1/35) of cases that received an additional TAL.•Average time for ulcer development was 592.50 days, and average follow-up time for all patients was 583.98 days.•45.0% (9/20) of patients with forefoot ulcers developed osteomyelitis, and 15.0% (3/20) of these patients went on to more proximal amputations.•Half of patients who developed forefoot ulcers were 53 years of age or younger.•Of the 4 surgeons that performed the most non-TAL procedures, all had a high incidence of neuropathic forefoot ulceration development, ranging from 12.5% to 40.0%.

Analysis & Discussion25.3% of cases that had a TMA developed a neuropathic forefoot ulcer compared to only 2.8% when a TAL was added (p=0.01). Patients that developed forefoot ulcers were significantly younger compared to patients that did not develop forefoot ulcers, 54.6 vs 63.8 (p=0.001). Although age was a potential confounding variable, it did not differ between groups with or without a TAL. Average follow-up time was less for patients with a TAL; however, it is unlikely this would explain the large effect size. The long average time for ulcer development (592.50 days) may be due to delayed contracture, and future studies require longer follow-up. Patients who had plantar heel ulcers and Achilles tendon ruptures healed without complications.

Data shows that the addition of an Achilles lengthening procedure reduces the risk of diabetic neuropathic forefoot ulcers and our data supports it’s use prophylactically with TMAs, especially in the younger patient population. Our data also shows that patients who developed neuropathic ulcers after TMA alone had significant morbidity and were likely to develop osteomyelitis with a risk of needing more proximal amputation. Although the study shows that adding a TAL to a TMA will help to reduce the development of forefoot ulcers, every surgical plan should be chosen carefully based on the individual patient.

References1. McCallum, Ryan, and Mark Tagoe. Transmetatarsal amputation: a case series and review of

the literature. Journal of aging research 2012;2012:797218.2. Armstrong, David G., et al. Lengthening of the Achilles tendon in diabetic patients who are at

high risk for ulceration of the foot. The Journal of Bone and Joint Surgery 1999;81.4:535-538.3. Barry DC, Sabacinski KA, Habershaw GM, et al. Tendo Achillis procedures for chronic

ulcerations in diabetic patients with transmetatarsal amputations. J Am Podiatr Med Assoc 1993;83:96–100.

4. Attinger C, Venturi M, Kim K, et al. Maximizing the length and optimizing biomechanics in foot amputations by avoiding cookbook recipes for amputation. Semin Vasc Surg 2003;16(1):44–66.

5. La Fontaine J, Brown D, Adams M, et al. New and recurrent ulcerations after percutaneous Achilles tendon lengthening in transmetatarsal amputation. J Foot Ankle Surg 2008;47(3):225–9.

Table 2: Demographics for Patients with & without Neuropathic Forefoot Ulcers

VariablePlantar Forefoot Ulcer

Positive (n=20)Plantar Forefoot Ulcer

Negative (n=90)p-value

Gender (male) 18/20 (90%) 67/90 (74.4%) 0.236

Gender (female) 2/20 (10.0%) 23/90 (25.6%) 0.236

Diabetes 19/20 (95.5%) 85/90 (94.4%) 1.00

Smoker 3/20 (15.5%) 5/90 (6.7%) 0.360

PVD 4/20 (20.0%) 44/90 (48.9%) 0.024

Age (years) 54.65 (mean) 63.77 (mean) 0.001

HbA1c 8.73 (mean) 8.40 (mean) 0.600

GFR 69.26 (mean) 60.84 (mean) 0.333

BMI 32.64 (mean) 30.88 (mean) 0.359

Figure 3: Plantar forefoot ulceration after TMA alone

Figure 1: Achilles tendon lengthening technique

Figure 2: Increased dorsiflexion after TAL at 6-month follow-up

Financial Disclosures: None

Table 1: Primary & Secondary Outcomes After TMA with or without TAL

Variable TMA Alone (n=75)TMA with TAL

(n=35)p-value

Neuropathic Forefoot Ulcer Development

19/75 (25.3%) 1/35 (2.8%) 0.004

New Plantar Heel Ulceration

0/75 (0.0%) 1/35 (2.9%) 0.141

New Posterior Heel Wounds

3/75 (4.0%) 0/35 (0.0%) 0.230

Average Follow-Up Time (days)

641.11 495.11 ----

Achilles Tendon Rupture 0/75 (0.0%) 2/35 (5.7%) 0.037

Age at Surgery (years) 61.97 (mean) 62.40 (mean) 0.366

Time Between Surgery & Ulcer Development (days)

587.11 695.00 ----

Proximal Amputation 7/75 (9.3%) 1/35 (2.8%) ----

Death 21/75 (28.0%) 3/35 (8.5%) 0.022

Special thanks to Neli Ragina, PhD, Stephen Zyzanski, PhD and Ronald Thomas, PhD for their contributions to study design and statistical analyses.

Results