How Can We Reduce The Alarming Re-Amputation Rate In Patients Who Have TMA Procedures?

A study recently published in the Journal of Foot and Ankle Surgery provided eye-opening insight regarding the outcome of transmetatarsal amputation (TMA).¹ Patients who undergo a TMA have a greater than 30 percent chance of undergoing a major (above ankle) amputation within five years.¹

An additional 30 percent of TMA patients can expect to have some type of reoperation and another 30 percent will have a re-amputation of some part of their foot below the ankle.^2,3 This means that up to 90 percent of all patients who undergo a TMA will be facing further surgery.

This excellent systematic review conducted by Thorud and coworkers provided much needed insight into the results of many studies of patients who have a TMA procedure.¹ The authors reviewed 24 published reports on the outcomes of patients undergoing TMA with attention to documentation of rates of reoperation, re-amputation and subsequent major amputation. While these studies differed in follow-up duration, over 1,000 patients were eligible to be evaluated for the rate of occurrence of re-operation and amputation.

Studies of 1,200 patients who had a TMA revealed that 430 patients required further amputations, which included proximal foot amputation as well as major below-knee and above-knee amputation.¹ This demonstrates a 35 percent re-amputation rate, which predominately occurred within the first year of the primary TMA.

There are many reasons that can possibly explain this alarming rate of re-amputation in patients with TMAs. First of all, ischemia was identified as a major reason that TMA patients require re-amputation.² However, other studies did not show that ankle brachial index (ABI) was a factor in determining re-amputation risk.^3,5 Renal failure and elevated glycosylated hemoglobin are also risk factors for amputation.^6,7 However, this systematic review by Thorud found no consistent risk factor to explain the high incidence of reoperation and re-amputation in patients undergoing TMA.¹

With few predictors of failure yet unpredictable outcome, there must be some skepticism when it comes to selecting TMA as a treatment option for patients with serious foot ulceration and infection. Perhaps it is time to re-evaluate the way we manage these patients postoperatively and realize that biomechanical factors may come into play, something we clearly overlook as a causative factor for failure of the TMA procedure.

There are several reasons for the high ulceration rate in patients who have undergone a TMA procedure. Studies have documented high plantar pressures in the residual foot in comparison to the contralateral foot in patients who have had TMA procedures.^8,9 This may be related to the substantial gait disturbances that researchers have observed in this patient population.¹⁰ Mueller and coworkers studied patients with diabetes and TMA, and found less range of motion, lower peak moments and diminished power at the ankle in comparison to age-matched controls.¹¹

The standard of care for the patient with a TMA is protecting the residual foot with therapeutic footwear including a total contact foot orthosis with a toe filler.^12,13 Given the high incidence of failure with this preventive intervention, is it not time for us to investigate other options to prevent re-amputation in patients who have undergone a TMA procedure?     

References

1. Thorud JC, Jupiter DC, Lorenzana J, et al. Reoperation and reamputation after transmetatarsal amputation: A systematic review. J Foot Ankle Surg. 2016; 55(5):1007–1012
2. Hosch J, Quiroga C, Bosma J, et al. Outcomes of 
transmetatarsal amputations in patients with diabetes mellitus. J Foot Ankle Surg. 1997; 
36(6):430–434. 

3. Toursarkissian B, Hagino RT, Khan K, et al. Healing of transmetatarsal amputation in the diabetic patient: is angiography predictive? Ann Vasc Surg. 2005; 19(6):769–773. 

4. Blume P, Salonga C, Garbalosa J, et al. 
Predictors for the healing of transmetatarsal amputations: retrospective study of 
91 amputations. Vascular. 2007; 15(3):126–133.
5. Anthony T, Roberts J, Modrall JG, et al. Transmetatarsal amputation: assessment of current selection criteria. Am J Surg. 2006; 192(5):e8–e11.
6. Younger AS, Awwad MA, Kalla TP, de Vries G. Risk factors for failure of trans metatarsal amputation in diabetic patients: a cohort study. Foot Ankle Int. 2009; 30(12):1177–1182.
7. Landry GJ, Silverman DA, Liem TK, et al. Predictors of healing and functional outcome following transmetatarsal amputations. Arch Surg. 2011; 146(9):1005–1009.
8. Mueller MJ, Strube MJ, Allen BT. Therapeutic footwear can reduce plantar pressures in patients with diabetes and transmetatarsal amputation. Diabetes Care. 1997; 20(4):637–41. 

9. Garbalosa JC, Cavanagh PR, Wu G, et al. Foot function in diabetic patients after partial amputation. Foot Ankle Int. 1996; 17(1):43–8. 

10. Hirsch G, McBride ME, Murray DD, et al. Chopart prosthesis and semirigid foot orthosis in traumatic forefoot amputation: Comparative gait analysis. Am J Phys Med Rehabil. 1996; 75(4):283–91.

11. Mueller MJ Salsich GB, Bastian AJ. Differences in the gait characteristics of people with diabetes and transmetatarsal amputation compared with age-matched controls. Gait Posture. 1998; 7(3):200–206
12. Mueller MJ, Allen BT, Strube MJ. Therapeutic footwear: Enhanced function in people with diabetes and transmetatarsal amputation. Arch Phys Med Rehabil. 1997; 78(9):952–6.
13. Ayyappa E. Postsurgical management of partial foot and Syme’s amputation. In Lusardi MM, Nielsen CC (eds): Orthotics and Prosthetics in Rehabilitation. Butterworth-Heinemann, Woburn, MA, 2000, pp. 379–93.