Digital Amputations in the Diabetic Foot

Today, 50-70% of all non-traumatic amputations occur in persons with diabetes. Most of the studies on amputation describe primarily major amputations. We performed a retrospective study digital amputations in the diabetic foot in which gangrene was the most common cause for toe amputation. Out of 114 amputations, 48 patients who had undergone a single toe amputation were studied. The average age of subjects undergoing toe amputation was 61.23 years, while 72.9% of subjects in our series were males. The great toe was the most common toe to be amputated followed by the fourth toe.

Address of Correspondence: Dr. Ajit Kumar Varma, Professor, Department of Endocrinology, Diabetic Lower Limb and Podiatric Surgery, Amrita Institute of Medical Sciences & Research Center, Amrita Vishwa Vidy Apeetham University Elammakara, Kochi, Kerala-682041, India. Email ajitkumarvarma@aims.amrita.edu

1 Postdoctoral Fellow in diabetic lower limb & podiatric surgery. Department of Endocrinology, Diabetic Lower Limb and Podiatric Sugery, Amrita Institute of Medical Sciences & Research Center, Elammakara, Kochi, Kerala, India.

2 Professor. Department of Endocrinology, Diabetic Lower Limb and Podiatric Sugery, Amrita Institute of Medical Sciences & Research Center, Elammakara, Kochi, Kerala, India.

3 Podiatry Assistant. Department of Endocrinology, Diabetic Lower Limb and Podiatric Sugery, Amrita Institute of Medical Sciences & Research Center, Elammakara, Kochi, Kerala, India.

4 Associate Professor. Department of Endocrinology, Diabetic Lower Limb and Podiatric Sugery, Amrita Institute of Medical Sciences & Research Center, Elammakara, Kochi, Kerala, India.

5Professor. Department of Endocrinology, Diabetic Lower Limb and Podiatric Sugery, Amrita Institute of Medical Sciences & Research Center, Elammakara, Kochi, Kerala, India.

6 Professor & HOD. Department of Endocrinology, Diabetic Lower Limb and Podiatric Sugery, Amrita Institute of Medical Sciences & Research Center, Elammakara, Kochi, Kerala, India.

Introduction

Amputations are more commonly performed in persons with diabetes than in non-diabetic patients.1 In fact, one study reported that five out of six amputations occurred in diabetic subjects.2 Once considered a crude mundane procedure, amputation can be viewed as a reconstructive procedure on par with any other limb reconstruction.3

In the past, digital amputations were performed almost exclusively for trauma. Today, 50-70% of all non-traumatic amputations occur in diabetic patients4 and the most common cause of digital amputation is wet gangrene due to infection. Patients who have undergone digital amputation are at a greater risk of undergoing further amputation in the same limb as well as in the contralateral limb. Mortality rates at 3 and 5 years approach fifty percent in diabetic amputees, with more proximal amputations having worse survival.

The amputation rates differ widely across geographic regions within countries as well as between countries. The amputation rates range from 0.7 per 1000 in East Asian populations to 31.0 per 1000 in U.S Pima Indians.5-10 Even though the frequency of minor amputations is greater, most of the data on amputations involves major amputation. Many minor amputations such as digital amputation that usually occur in outpatient facilities are excluded when prevalence of amputation is considered. Therefore, the purpose of this study was to evaluate the incidence of digital amputations for diabetic foot infections.

CAUSES	NUMBER	PERCENTAGE
OSTEOMYELITIS	8	16.67%
NON HEALING ULCER	19	39.58%
GANGRENE	20	41.67%
ABSCESS	1	2.08%
TOTAL	48	100%

Table 1 Distribution of amputated toes by causes of amputation.

Materials and Methods

A retrospective study was carried out from September 2008 to February 2009 in the Department of Endocrinology, Diabetic lower limb and Podiatric surgery at Amrita Institute of Medical Sciences, Kerala, which is a tertiary care superspeciality hospital. All patients who had undergone a single toe amputation were studied during this period. Age, sex, site, side and lesion involved were recorded. Additionally, the ankle – brachial index [ABI] and vibration perception were obtained. All the patients who had undergone more than single toe amputation with or without debridement, traumatic amputation and multiple digital amputations were excluded from this study.

Results

A total of 114 patients had undergone amputation (minor and major) during this period. The minor amputations included toe amputations, ray and partial foot amputation. The study group consists of 48 (42.12%) of the patients who had undergone a single toe amputation. There was no partial amputation of toes during this period. The average age was 61.23 years with a range of 42 to 77 years. There were 35 males and 13 females with a ratio of 2.7:1.The distribution of patients according to sex, side of foot, toe involved, lesion and ankle-brachial index is summarized in Tables 1, 2, and 3.

All the patients [100%] who underwent toe amputation had neuropathy as detected by vibration perception threshold whereas only 12.5% of patients had peripheral arterial disease as measured by ankle brachial index. The most common toe amputation was of the great toe and the most frequent cause of digital amputation was gangrene. (Figure 1) The other causes were non-healing ulcer (Figure 2), abscess and osteomyelitis with ulcer. The 4th toe was the second most common toe that underwent amputation. (Figure 3)

TOES AFFECTED	NUMBER	PERCENTAGE
GREAT TOE	23	47.92%
2ND TOE	3	39.58%
3ND TOE	7	14.58%
4TH TOE	11	22.92%
5TH TOE	4	8.44%
TOTAL	48	100%

Table 2 Distribution of amputation by site of amputation.

ABI	TOES	PERCENTAGE
0.9 – 1.3[NORMAL]	42	87.5%
0.6 – 0.89	26	12.5%
0.3 – 0.59	0	0%
< 0.3	0	0%

Table 3 Distribution of toe amputations according to ankle brachial index (ABI).

Discussion

The Human foot is a mechanical marvel. It has 26 bones, 29 joints, and 42 muscles. The bones include 7 tarsal, 5 metatarsals and 14 phalanges. The plantar pressure on a foot of a normal man of 60 kg who is standing on one foot is 61 kilopascals. In a normal walking speed, the plantar pressure at the 1st metatarso-phalangeal (MTP) joint is about 299 kilopascals.11

The normal walking cycle consists of two phases; the stance phase, which takes 60% of entire gait cycle, and the swing phase, which takes 40 % of the gait cycle. The stance phase is divided into heel strike, midstance and toe off. During toe off, the great toe bears about 70% of body weight.

A mputation of the great toe leads to a disturbance in the biomechanics of the foot where the pressure is transferred to the next toe.12 A hammertoe deformity of the second toe frequently ensues and is subject to ulceration.

The prevalence of amputation in diabetic individuals is ten-fold higher compared with non diabetic subjects, 2.8% versus 0.29%.13 Foot lesions are perhaps the most common cause of hospitalization in persons with diabetes. As there is a trend towards a decline in amputations in developed countries, this is not so in the developing and underdeveloped countries.

Figure 1 4th toe gangrene. There is already a 4th toe amputation noted on the opposite foot.

Figure 2 Non-healing ulcer of the great toe.

Figure 3 4th toe injury requiring subsequent amputation.

India, with a population of greater than 1.1 billion, reportedly has the highest number of diabetic individuals in the world. It was estimated in the year 2000 that there were 32 million people with diabetes mellitus in India.14 Due to a rising diabetic population in India, the incidence of amputation is also increasing. Furthermore, barefoot walking, poor footwear and culture habits render the diabetic Indian to an increased risk of amputation of the toes.

Amputation of a single toe is associated with complications like transfer lesions, deviation of the toes and reulceration thereby altering the biomechanics. (Figure 4) This renders the other toes and the foot at a greater risk of amputation.15 When the hallux is lost due to amputation, the weight is transferred to the 2nd toe and 2nd metatarsal head. Approximately 65 % of hallux amputations develop new ulcerations, with 53 % requiring further proximal amputation.

Lesser metatarsal fractures may be seen after hallux amputation. Amputation of the hallux results in a reduction in the ability of the first metatarsal head to bear weight.

Figure 4 Deviation of toes to fill the gap after 3rd toe amputation.

This weight is then transferred to the lesser metatarsals. This increases the risk of lesser metatarsal head ulceration and is associated with a greater risk of lesser metatarsal stress fracture.16

Conclusion

Toe amputation is the most commonly performed amputation in the diabetic foot with the great toe being the commonest toe (47.92%) involved followed by the 4th toe (22.92%). Gangrene was the most frequent cause for toe amputation. All patients who underwent toe amputation had peripheral neuropathy as determined by vibration perception threshold and relatively few had vasculopathy (12.5%).

Cultural habits in India and the customary use of open footwear (sandals) contribute to the incidence of digital trauma and subsequent amputation in our patients. Although difficult in this population, behavioral and footwear changes need to be encouraged as primary preventive measures to reduce the burden of ulceration and amputation in this high-risk population.

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AUTHORS’ CONTRIBUTIONS

Dr Amit Kumar- Data collection, Conceptualization, design and preparation of manuscript. Dr
Viswanath – critical revision and data collection.