The Role of Revascularization in Transmetatarsal Amputations

Abstract

Data from 37 patients who underwent a transmetatarsal amputation from January 1993 to April 1996 were reviewed. The mean age and diabetes duration of the subjects were 54.9 (± 13.2) years and 16.6 (± 8.9) years, respectively. The follow-up period averaged 42.1 (± 11.2) months. At the time of follow-up, 29 (78.4%) of the 37 patients still had foot salvage, 8 (21.6%) had progressed to below-the-knee amputation, and 15 (40.5%) had undergone lower-extremity revascularization. Twelve (80%) of the 15 revascularized patients preserved their transmetatarsal amputation level at a follow-up of 36.4 months. The authors concluded that at a maximum of 3 years follow-up after initial amputation, transmetatarsal amputation was a successful amputation level. (J Am Podiatr Med Assoc 91(10): 533-535, 2001)

Bernard and Heute first described the transmetatarsal amputation for trench foot in 1855.[1] In 1949, McKittrick et al[2] proposed the procedure as foot salvage for diabetic patients with infection or gangrene. However, the benefit of performing a partial foot amputation is well established in the medical literature. The more proximal the amputation, the greater the energy cost of ambulation and the lower the level of subsequent independent functioning.[3]

Many reports in the medical literature have discussed the success of transmetatarsal amputations. McKittrick et al[2] reviewed 43 amputations in 40 patients, 30 of which were patients with diabetes. The authors reported a successful rate in 19 (63.3%) of 30 patients with diabetes, but they were unable to find any prognosticating factors in determining the successful versus failed transmetatarsal amputations. The main factor influencing success was the degree of circulatory impairment. Hunter[4] demonstrated that 12 (46%) of 26 transmetatarsal amputations healed at 3 months, concluding that transmetatarsal amputation is not recommended unless successful revascularization has been performed. Effeney et al[5] performed a retrospective chart review of 25 patients who underwent transmetatarsal amputations and found that in 13 (52%) of the 25 patients, the transmetatarsal amputation had healed. Durham et al[6] found successful transmetatarsal amputations in 23 (53%) of 43 patients. Nine (39.1%) of the 23 patients had undergone revascularization. Hobson et al[7] retrospectively evaluated 30 patients with transmetatarsal amputations and found that 15 (50%) patients had progressed to a more proximal amputation, concluding that patient selection is key to a successful transmetatarsal amputation. In 1997, Hosch et al[8] reported a 70% success rate for transmetatarsal amputations, at an average of 1-year follow-up. Although this represents a high success rate, the logical question is to ask what happens to these patients 2 to 3 years later.

The high variability in success rates reported in the medical literature is most likely due to differences in patient selection and how success is defined. Several studies have compiled outcomes in diabetic and nondiabetic patients, as well as traumatic and nontraumatic amputations. The present study reports on long-term follow-up of transmetatarsal amputations in diabetic patients at 3 to 5 years.

Materials and Methods

Inpatient and outpatient medical records were reviewed of 85 patients who underwent transmetatarsal amputation at the University of Texas Health Science Center at San Antonio, Texas, from January 1993 to April 1996. All of the transmetatarsal amputations were performed by the Podiatry Service, Department of Orthopedics, at the University of Texas Health Science Center at San Antonio. Forty-two patients underwent a transmetatarsal amputation as the primary procedure for salvage. Five patients had incomplete medical records; therefore data were collected on 37 patients.

Data collected included the patient’s demographics, past medical history, and duration of diabetes. Lower-extremity examination data included pedal pulses assessment, noninvasive vascular studies, history of lower-extremity revascularization, history of previous pedal amputations, and presence or absence of peripheral neuropathy. Indications for transmetatarsal amputation, diagnosis at the time of subsequent amputation, and current level of amputation were also identified. Patients with traumatic amputations or incomplete medical records were excluded. Success was defined as retention of the transmetatarsal amputation at the time of review. Peripheral vascular disease was defined as an absence of dorsalis pedis or posterior tibial pulse, an ankle-brachial index of less than 0.80, or transcutaneous oxygen pressure of less than 30 mm Hg.

Results

Thirty-seven diabetic patients underwent transmetatarsal amputation from 1993 to 1996. Thirty (81.1%) of the patients were men; 7 (18.9%) were women. The mean (± SD) age of the patients was 54.9 ± 13.2 years. The average duration of diabetes was 16.6 ± 8.9 years. Thirty-three (89.2%) of the 37 patients had type 2 diabetes and 4 (10.8%) had type 1 diabetes mellitus. The study group consisted of 27 (73%) Hispanics, 2 (5.4%) whites, and 8 (21.6%) blacks. Mean follow-up was 42.1 ± 11.2 months with a range of 27 to 60 months. The mean glycosylated hemoglobin was 10.05%.

Eight (21.6%) patients had progressed to a below-the-knee or above-the-knee amputation. Twenty-five (67.6%) patients had previous distal forefoot amputations on the same foot. The preoperative diagnosis at the time of surgery was osteomyelitis in 18 (48.6%) patients, soft-tissue infection was present in 13 (35.1%) patients, and critical ischemia only was present in 6 (16.2%) patients. Twenty (64.5%) of 31 patients with a diagnosis of osteomyelitis and soft-tissue infection also had peripheral vascular disease. Therefore, 26 (70.3%) patients had some degree of peripheral vascular disease.

Fifteen (57.7%) of the 26 patients with peripheral vascular disease underwent lower-extremity revascularization prior to transmetatarsal amputations. Twelve (80%) of the 15 revascularized patients preserved the transmetatarsal level at an average follow-up of 36.4 months. Three (20%) of these patients progressed to a below-the-knee amputation. All eight patients with high-level amputation had ischemia as their primary diagnosis prior to the below-the-knee amputation with TcPO₂ < 30 mm Hg at the transmetatarsal level. At the time of follow-up 29 (78.4%) patients retained part of their foot, 25 (67.6%) with transmetatarsal amputation and 4 (10.8%) with Chopart’s amputation.

Discussion

In the present study, 29 (78.4%) patients retained their transmetatarsal amputations at the time of follow-up. Additionally, only 3 (20%) of the patients who were revascularized progressed to a high proximal amputation. Moreover, these three patients were revascularized after the transmetatarsal amputations. Eleven patients were considered to have ischemia as their primary diagnosis and the eight patients who went on to a high proximal amputation had ischemia as their primary diagnosis. Three of these patients were considered non-bypassable because of a mild degree of ischemia. Therefore, the study’s findings confirm that revascularization, and especially early revascularization, plays an important role in limb salvage. It also suggests that in patients with mild degrees of peripheral vascular disease, revascularization may also play an important role in preserving a partial foot amputation.

The limb salvage rate was 80% at an average follow-up of 3 years for the patients in the study group. Recent reports have shown good results using transmetatarsal amputations for foot salvage in diabetic patients. In general, good results are defined as good healing at the amputation site. This increased rate of success may be due to different definitions of success, closer follow-up after amputation, better patient selection, or all of the above. Hosch et al[8] showed that patients with ischemia were more likely to progress to a below-the-knee amputation than patients with infection alone. A majority of the previous studies included both diabetic and nondiabetic patients with peripheral vascular disease. The poor results of transmetatarsal amputations in these studies may be due to severe vascular disease rather than the inherent problems associated with transmetatarsal amputations. The high success rate seen in this study may be due not only to patient selection but also to early vascular intervention, which improves distal flow.

Conclusion

Transmetatarsal amputation is a viable and successful treatment option for diabetic limb salvage. Proper patient selection based on the severity of macrovascular disease and timely bypass increases the success rate of midfoot amputations. Additionally, the long-term review in this study suggests that patients diagnosed with peripheral vascular disease prior to amputation have a greater likelihood of requiring a subsequent, more proximal amputation.