Transmetatarsal Amputations and Risk Factors for Complications

The prevalence of diabetes mellitus in the U.S. is continuing to grow, affecting an estimated 10% of the population. As this number increases, the number of diabetes-related, minor, lower extremity amputations is expected to rise as well, with a 62% increase between 2009 and 2015 alone. But while transmetatarsal amputations (TMA) are a common type of minor amputation due to diabetes for limb salvage, the long-term durability of this procedure remains largely unknown.

In their 2022 retrospective study, Tokarski et al. sought  to address this gap in knowledge by analyzing diabetic patients who had undergone TMAs over an 11-year period to determine the long-term durability of the limb salvage procedure.

Assessing the Durability of Transmetatarsal Amputations

Tokarski et al. examined 79 patients (83 TMAs), all of which had been previously diagnosed with type I or type II diabetes. Patients were required to have had a successful transmetatarsal amputation, defined by the authors as having demonstrated clinical healing in the one-year post-surgery. In all cases, the TMA had been performed due to a diabetic foot ulcer infection.

Here are some of their key findings on timing of healing and re-ulceration:

• • Average time to healing after transmetatarsal amputation: 109.80 days
  • Average follow-up time: 4 years
  • 44% of TMAs had at least one re-ulceration event during follow-up
  • Average time to the re-ulceration from the successful date of healing: 467 days
  • Days to re-ulceration ranged from 21 days to 2,069 days (or 5.67 years)

They also found the below factors significant in assessing durability of TMAs:

• • Younger age was found to be a significant factor in re-ulceration, with the mean age of the re-ulceration group at 54.6 years, and the mean age of the non-re-ulcerated group being 60.4 years
  • The re-ulceration group also had a significantly higher mean pre-procedure hemoglobin A1c at 9.1% vs. 7.7%
  • There was significantly shorter time to healing for those who had underwent tendon balancing procedures compared to those who had not (81.23 days vs. 130.62 days)
  • 12 transmetatarsal amputations progressed to a lower extremity amputation below the knee after the initial success at one year, and 13 TMAs needed a revision procedure

Tokarski et al. conclude that having “tight glycemic control” will reduce the likelihood of re-ulceration after successful healing, and patient age and elevated hemoglobin A1c could help determine whether a successful transmetatarsal amputation will be durable.

Overall, however, they consider a successful transmetatarsal amputation to be a durable procedure for amputation due to diabetes and diabetic limb salvage but note that with high re-ulceration rates and likelihood of a more proximal amputation, surgeons should be aware that patients can be at risk. The study authors recommend lifelong follow-up, revision surgery and tendon balancing as needed.

Amputation Due to Diabetes: Are There Modifiable Factors Linked to Wound Complications?

While Tokarski et al. determined that re-ulceration and more proximal amputation is a risk for specific TMA patients, are there factors that could cause other complications as well?

In their retrospective analysis published in the Journal of Surgical Research, Kantar et al. identified 2,316 diabetic patients who had undergone TMA from 2009 to 2015 using the American College of Surgeons National Surgical Quality Improvement Database.

The rate of wound complications was found to be 11.9% in these lower limb amputations. They found that patients who had a significantly longer operative time were more likely to develop post-operative wound complications. Additionally, patients who developed post-operative wound complications were significantly more likely to be obese (47.1% vs 41.5%).

Kantar et al. note that while obesity may not be a rapidly modifiable risk factor, having patients acknowledge the additional risk it poses for post-operative complications may improve pre-operative care, counseling and planning. Surgeons, they acknowledge, should have “heightened clinical vigilance” when performing a TMA in an obese patient.

They also acknowledge that Daley et al., who used a subset of the national database used in their study, found that the risk of complications in this patient population increases with every extra hour of operative time. Kantar et al. therefore suggest that modifiable factors that could affect operative time, such as technical challenges, surgeon experience and patient characteristics should be addressed preoperatively.

This would not only help to reduce complications but could also reduce hospital cost and resource utilization as well. Further prospective studies, they note, should aim to establish causality between operative time, obesity and wound complications within this patient population.

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