Assessment of foot deformities in patients with type 2 diabetes mellitus

INTRODUCTION

Diabetes mellitus is a major health problem world-wide, affecting people in all age groups. In India, more than 60 million individuals are currently diagnosed with the disease which is more than any other country in the world.^1,2 Lower extremity problems represent the most common source of morbidity and hospitalization in diabetic population.^3-5 The prevalence of foot ulcer in diabetic population has been reported to be around 4-6%.^2,3 These diabetic ulcers can be easily prevented by identifying the risk factors and taking appropriate preventive measures but once ulceration occurs, its cure is extremely difficult. Furthermore, diabetics are 15 times more likely to undergo a lower extremity amputation when compared to their normal counterparts.⁶

Foot deformity is a known risk factor for development of callosities and ulcers. The abnormal bony prominence developed by these stretched deformities leads to abnormally high pressure and when combined with insensitivity of foot, causes tissue breakdown and ulceration.^7,8 The involvement of the foot in systemic diabetic neuropathy can lead to objective differences in the foot structure and severe alterations in gait cycle patterns which together combine to cause the biomechanical impairment of foot.^9,10 Both sensory and motor components of peripheral nervous system are affected. Motor neuropathy leads to weakness of the intrinsic muscles of foot and disturbs the balance between the flexor and extensor compartments.¹¹ This can cause several deformities like hammer toe, claw toe, pes cavus, flat foot and hallux valgus.¹² These foot complications can be serious and disabling, the most feared consequence being a lower extremity amputation (9.9% to 21.5%).^13,14

The knowledge so far about the prevalence of foot deformity and its association with different clinical parameters in diabetic population is limited. The current study aimed to assess the prevalence of foot deformities in known diabetics and to compare it with non-diabetic population. It also aimed to know the association of foot deformity with various factors like age, sex, duration of disease, mode of treatment, presence of neuropathy and presence of vasculopathy.

METHODS

A prospective study was conducted in the department of orthopaedics and medicine at a tertiary care hospital between 2018 and 2020. The study group included patients with type 2 diabetes mellitus attending diabetic and orthopaedic clinic. Patients with foot ulceration or infection and those who had undergone amputation of lower extremity were excluded from the study. The non-diabetic individuals who were matched for age and gender constituted the control group. The prevalence of foot deformities in both groups was compared. The type of foot deformity and the region of foot involved was noted.

Neurological assessment of foot was done for insensitivity by a 10 gm nylon monofilament which buckled on giving a force of 10 gm when applied perpendicular to various sites of foot (Figure 1). Measurements were taken at plantar aspect of 1st, 3rd and 5th digits, plantar aspect of 1st, 3rd and 5th metatarsal heads, medial and lateral sides of plantar aspect of mid foot, plantar area of heel and dorsal aspect of mid foot. The failure to feel monofilament at four out of ten sites on the foot was taken as an indication of loss of protective sensation (Armstrong 1998).^15,16 The measurement of vibration perception threshold was assessed using a bio-thesiometer (an apparatus used for vibration threshold measurement).^17,18

. Figure 1: 10 gm monofilament used for assessing sensory neuropathy.

Peripheral arterial pulsations of posterior tibial and dorsalis pedis artery were assessed by Doppler ultrasonography using a handheld Doppler and ankle brachial pressure index (ABPI) was measured.

Biochemical test for glycated haemoglobin (HbA1c) indicated control of blood sugar in past three months. It was measured by using Roche Hitachi 904 clinical chemical analyser.

Association between foot deformity and diabetes was calculated using chi square test. Relative risk of diabetes mellitus in causing foot deformities was also determined and 95% confidence interval was calculated. Comparison of other continuous and discrete variables was done using the t-test and Chi square test respectively. Statistical significance was determined by a p value <0.05.

RESULTS

In this prospective study, there were 80 subjects in each group. The prevalence of foot deformity in diabetic and control group was 33.8% (27/80) and 12.5% (10/80) respectively and this difference was statistically significant (p<0.001) (Table 1). There was no significant difference between the prevalence in male and female patients. The difference between the affection of right and left foot was also not significant. We found 66 deformities in total out of which 55 (83.3%) were present in forefoot, seven (10.6%) in mid foot and four (6.1%) in hind foot (Table 2).

There were 28 nail deformities (42.4%), 16 callosities (24.2%), 14 hallux valgus (21.2%), 3 claw toe (4.5%) and 1 hammer to toe (1.5%) (Figure 2). Two patients had Charcot’s foot and both had bilateral involvement. The prevalence of deformities increased with the duration of diabetes. Maximum number of deformities were present in patients with duration of disease between 6-10 years (11 out of 25, 44%) and all 6 patients with duration of disease over 20 years had some kind of foot deformity (100%).

There was no statistically significant difference between the patients on regular treatment and those who were taking treatment irregularly. Also, there was no significant difference between the patients on oral hypoglycaemic agents (OHA), those on insulin or those on both OHA and insulin. The prevalence in the patients who were aware about the foot care measures was 17.9% whereas it was 48.8% in those who were unaware about it (p<0.004). However, awareness about the diabetic footwear had no significance. All 27 patients having foot deformity also had neuropathy and its prevalence increased with the duration of disease. Two patients with deformity had absent distal pulsations whereas 5 had ankle brachial index less than 0.9. The average ABI in diabetic group was 1.0045 on left side and 1.0111 on right side. The HbA1c in our study was 8.81% and 18 patients having deformity (67%) had HbA1c more than 9.

DISCUSSION

Prior studies have mentioned the prevalence of lower extremity complications in the diabetic population by focusing on the number of limb amputations performed annually.¹⁹ The prevalence of lower extremity complications was twice in diabetics as compared to non-diabetics and it affected 30% of diabetic population over 40 years of age.^20,21 Ogbera et al reported prevalence of foot deformities as 26.4% in patients with type 2 diabetes mellitus, while the study by Mansour et al mentioned 46.7% prevalence of diabetic foot abnormalities.^22,23 In a similar study by Ababneh et al Hallux valgus was found in 17.4%, claw/hammer toe in 16%, prominent metatarsal head in 14.2%, limited joint mobility in 9.4%, pes cavus in 3.2%, and Charcot foot in 2.1% of patients with type 2 diabetes mellitus.²⁴ Mekonnen et al had reported an overall prevalence of diabetes related foot deformities to be 36.5%.²⁵ In their study, the most common structural foot deformities were claw/hammer toe (12%), followed by callus (9%), hallux valgus (8.5%) and pes cavus (7%). However, none of these studies have compared the results with normal population. In our study, prevalence of foot deformity in diabetic population was 33.8% as compared to 12.5% in control. While prior studies, Ogbera et al had reported a slight male preponderance, there was no such trend in our study. In current study, forefoot was most commonly involved with a prevalence of 83.3% followed by mid foot and hind foot. Nail deformities were most common (42.4%) followed by callosities (24.2%) and hallux valgus (21.2%). Although higher duration has been considered a high-risk sign, none of the studies had made a direct correlation between duration of diabetes and development of foot deformities. The current study proved a direct correlation between development of foot deformities and duration of disease. Patients with diabetes for 6-10 years had maximum number of deformities and all patients having duration more than 20 years had one or more foot deformity. The fact that the patient was diabetic was more important. The regularity of treatment did not seem to change the results. Patients developed deformities despite being on regular treatment. Though insulin use had been considered as a predictor of foot deformities by Mansour et al we did not come across any previous study showing any co-relation between the development of foot deformities and the treatment modality or the regularity of treatment.²³ Our study being an outpatient study, most of the patients were on OHA. There was no significant difference between the prevalence of deformities in the patients on OHA and those on insulin or on both modalities of treatment. Also, there was no familial predisposition regarding development of foot deformities. Earlier studies by Barth et al, Litzclman et al and Pieber et al had reported reduced foot problems with foot care education.^26-28 The current study also evidenced low prevalence of foot deformities in the patients having foot care awareness. However, awareness regarding type of diabetic footwear didn’t prove useful.

Earlier studies had indicated that the prevalence of neuropathy may vary between 14-63% depending upon the type of population studied and the criteria used to define diabetic neuropathy.^29-31 In Seattle diabetic foot study, monofilament insensitivity in diabetic patients was as high as 60%.³² Vibration threshold more than 25 V was a potential indicator of neuropathy and development of foot ulcers. In current study, three indicators were used to access neuropathy, sensory perception using monofilament, vibration potential threshold more than 25 V and absence of deep tendon reflexes. Decreased sensory perception was found in 37% population, 44% had vibration potential over 25 V and 40% had absent deep tendon reflexes. This showed that foot deformities developed only in the presence of advanced neuropathy as evidenced by above indicators.

Peripheral vascular disease (PVD) had been noted in 18.4% of the subjects with diabetes.²⁵ Ankle brachial pressure index (ABPI) of 0.9 or less was usually considered to be diagnostic of PVD.³³ In a study by Holewski et al only 22% of diabetic patients showed ABI less than 0.9, which was similar to the finding in current study (16.25%).³⁴ Moreover, only 7.4% cases with foot deformities had bilateral pedal pulses absent. This showed that checking pulses alone may not be enough to identify patients with peripheral vascular disease since two-third of patients with abnormal ankle brachial index had palpable pedal pulsations. This also showed that the majority of patients do have neuropathic foot rather than a neuro-ischaemic foot.

Most of the earlier studies had mentioned poor glycaemic control as one of the most important factors in the genesis of diabetic complications.^32,35 Peters et al reported mean HBA1C level as 8.8±2% in patients with peripheral neuropathy.³⁵ In another study by Perkins et al HbA1c level of more than 9% was taken as cut off for poor glycaemic control which was a significant predictor of severity of distal sensory motor polyneuropathy.³⁶ The average glycaemic index in current study was 8.81% and 67% of patients had a value over 9%. This suggested a co-relation between poor glycaemic control and development of foot deformities.

CONCLUSION

The prevalence of foot deformity is significantly more in patients with type 2 diabetes mellitus when compared to their normal counterparts. A longer duration of disease increases the risk of developing peripheral neuropathy and foot deformity. All patients with diabetes should be screened for presence of peripheral neuropathy as this is the most common factor for development of a foot deformity and hence a foot ulcer. Other helpful screening measures include assessment of peripheral vascular disease by measuring ankle brachial index and monitoring HcA1c. Educating the patients about diabetic foot care measures can be helpful in avoiding potential complications.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

REFERENCES

1. 1. Joshi SR, Parikh RM. India-diabetes capital of the world: now heading towards hypertension. J Assoc Physicians India. 2007;55:323-4.
2. 2. Kumar A, Goel MK, Jain RB, Khanna P, Chaudhary V. India towards diabetes control: Key issues. Australas Med J. 2013;6(10):524-31.
3. 3. Naidoo P, Liu VJ, Mautone M, Bergin S. Lower limb complications of diabetes mellitus: a comprehensive review with clinicopathological insights from a dedicated high-risk diabetic foot multidisciplinary team. Brit J Radiol. 2015;88(1053):1053.
4. 4. Gregg EW, Beckles GL, Williamson DF, Leveille SG, Langlois JA, Engelgau MM, et al. Diabetes and physical disability among older U.S. adults. Diabetes Care. 2000;23(9):1272-7.
5. 5. Dolan NC, Liu K, Criqui MH, Greenland P, Guralnik JM, Chan C, et al. Peripheral artery disease, diabetes, and reduced lower extremity functioning. Diabetes Care. 2002;25(1):113-20.
6. 6. Muller IS, Grauw WJ, van Gerwen WH, Bartelink ML, van Den Hoogen HJ, Rutten GE. Foot ulceration and lower limb amputation in type 2 diabetic patients in Dutch primary health care. Diabetes Care. 2002;25(3):570-4.
7. 7. Veves A, Murray HJ, Young MJ, Boulton AJ. The risk of foot ulceration in diabetic patients with high foot pressure: a prospective study. Diabetologia. 1992;35(7):660-3.
8. 8. Reiber GE, Vileikyte L, Boyko EJ, Aguila MD, Smith DG, Lavery LA, et al. Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care. 1999;22(1):157-62.
9. 9. Fernando ME, Crowther RG, Cunningham M, Lazzarini AP, Sangla KS, Golledge J. Lower limb biomechanical characteristics of patients with neuropathic diabetic foot ulcers: the diabetes foot ulcer study protocol. BMC Endocr Disord. 2015;15:59.
10. 10. Chantal N, DaSilva M, Carvalho LC, Lunes DH. Foot reflexology in feet impairment of people with type 2 diabetes mellitus: randomized trial. Rev Lat Am Enfermagem. 2015;23(4):603-10.
11. 11. Runfeld GC. Diabetic foot ulcers. Etiology, treatment, and prevention. Adv Intern Med. 1992;37:103-32.
12. 12. Caselli A, Pham H, Giurini J, Armstrong D, Veves A. The forefoot-to-rearfoot plantar pressure ratio is increased in severe diabetic neuropathy and can predict foot ulceration. Diabetes Care. 2002;25(6):1066-71.
13. 13. Moss SE, Klein R, Klein BK. The 14-year incidence of lower-extremity amputations in a diabetic population: the Wisconsin Epidemiologic Study of Diabetic Retinopathy. Diabetes Care. 1999;22:951-9.
14. 14. Li X, Xiao T, Wang Y, Gu H, Liu Z, Jiang Y, et al. Incidence, risk factors for amputation among patients with diabetic foot ulcer in a Chinese tertiary hospital. Diabetes Res Clin Pract. 2011;93:26-30.
15. 15. Armstrong DG, Lavery LA, Vela SA, Quebedeaux TL, Fleischli JG. Choosing a practical screening instrument to identify patients at risk for diabetic foot ulceration. Arch Intern Med. 1998;158:289-92.
16. 16. Saltzman CL, Rashid R, Fellner C, Fitzpatric D, Klapach A. 4.5 gm monofilament sensation beneath both first metatarsal heads indicates protective foot sensation in diabetic patients. J Bone Joint Surg. 2004;86:717-23.
17. 17. Catherine LM, Barbara HW, Rodica PB, Patricia AC, Sarah C, James WA, et al. Vibration perception threshold as a measure of distal symmetrical peripheral neuropathy in type 1 diabetes. Diabetes Care. 2010;33(12):2635-41.
18. 18. Young MJ, Every N, Boulton AJ. A comparison of the neurothesiometer and biothesiometer for measuring vibration perception in diabetic patients. Diabetes Res Clin Pract. 1993;20(2):129-31.
19. 19. Tantisiriwat N, Janchai S. Common foot problems in diabetic foot clinic. J Med Assoc Thai. 2008;91(7):1097-101.
20. 20. Deshpande AD, Hayes MH, Schootman M. Epidemiology of diabetes and diabetes-related complications. Phys Ther. 2008;88(11):1254-64.
21. 21. Cook JJ, Simonson DC. Epidemiology and health care cost of diabetic foot problems. The Diabetic Foot: Medical and Surgical Management. Contempor Diabet. 2012;17:779-91.
22. 22. Ogbera AO, Adedokun A, Fasanmade OA, Ohwovoriole AE, Ajani M. The foot at risk in Nigerians with diabetes mellitus-the Nigerian scenario. Int J Endocrinol Metab. 2005;4:165-73.
23. 23. Mansour AA, Imran HJ. Foot abnormalities in diabetics: prevalence and predictors in Barsah, Iraq. Pak J Med Sci. 2006;22(3):229-33.
24. 24. Ababneh A, Bakri FG, Khader Y, Lazzarini P, Ajlouni K. Prevalence and associates of foot deformities among patients with diabetes in Jordan. Curr Diabetes Rev. 2020;16(5):471-82.
25. 25. Mekonnen BE, Wirtu AT, Kebede MA, Tilahun AG, Degaga TK. Diabetics-related foot deformity: prevalence, risk factors, knowledge and practice. Trends Anat Physiol. 2021;4:10.
26. 26. Barth R, Campbell LV, Allen S, Jupp JJ, Chisholm DJ. Intensive education improves knowledge, compliance, and foot problems in type 2 diabetes. Diabet Med. 1991;8:111-7.
27. 27. Litzelman DK, Slemenda CW. Reduction of lower extremity clinical abnormalities in patients with non-insulin-dependent diabetes mellitus. A randomized, controlled trial. Ann Intern Med. 1993;119:36-41.
28. 28. Pieber TR, Holler A, Siebenhofer A, Brunner GA, Semlitsch B, Schattenberg S, et al. Evaluation of a structured teaching and treatment programme for type 2 diabetes in general practice in a rural area of Austria. Diabet Med.1995;12(4):349-54.
29. 29. Davies M, Brophy S, Williams R, Taylor A. The prevalence, severity, and impact of painful diabetic peripheral neuropathy in type 2 diabetes. Diabetes Care. 2006;29(7):1518-22.
30. 30. Bansal V, Kalita J, Misra UK. Diabetic neuropathy. Postgrad Med J. 2006;82(964):95-100.
31. 31. Bansal D, Gudala K, Muthyala H, Esam H, Nayakallu R, Bhansali A. Prevalence and risk factors of development of peripheral diabetic neuropathy in type 2 diabetes mellitus in a tertiary care setting. J Diabetes Investig. 2014;5(6):714-21.
32. 32. Boyko EJ, Nelson KM, Ahroni JH, Heagerty PJ, Cohen V. Prediction of diabetic foot ulcer occurrence using commonly available clinical information. Seattle Diabet Foot Stud. 2006;29:1202-07.
33. 33. Singh N, Armstrong DG, Lipsky BA. Preventing foot ulcers in patients with diabetes. JAMA. 2005;293(2):217-28.
34. 34. Holewski JJ, Moss KM, Stress RM, Graf PM, Grunfeld C. Prevalence of foot pathology and lower extremity complications in a diabetic outpatient clinic. J Rehabil Res Dev.1989;26:35-44.
35. 35. Peters EJ, Lavery LA. Effectiveness of the diabetic foot risk classification system of the International Working Group on the Diabetic Foot. Diabetes Care. 2001;24(8):1442-7.
36. 36. Perkins BA, Douglas AG, Bril V. Glycemic control is related to the morphological severity of diabetic sensorimotor polyneuropathy. Diabetes Care. 2001;24:748-52.