Jennifer A. Mayfield, MD, MPH

Frequent foot examinations are widely recommended as a means of reducing the risk of foot ulcers and amputation in patients with type 2 diabetes.¹ This recommendation is primarily based on reports from diabetic foot care programs that provided frequent foot examinations, custom therapeutic footwear, patient education on footwear and foot care, and access to a multidisciplinary team of providers.^2-6 None of these reports, however, attempted to identify the specific contribution of foot examinations to the overall success of the program or the optimum frequency of those examinations. There is little evidence to support the recommendation that primary care physicians should perform foot examinations at every visit; yet this recommendation has almost become a universal mandate of diabetes quality-of-care protocols. Furthermore, there is no evidence for what examination components should be included. We conducted a retrospective evaluation of a population-based foot care program to determine the specific contribution of foot examinations to the risk of amputation.

Methods

Pima Indians of the Gila River Indian community in Arizona have one of the world’s highest reported incidence rates of diabetes and diabetic amputation.^7,8 Previous studies of this population have identified the demographic, pathophysiologic, and diabetes-related risk factors for lower-extremity amputation.⁷ Members of this community have participated in a National Institutes of Health (NIH) longitudinal study of diabetes since 1965.⁸

The Indian Health Service, a branch of the US Public Health Service, provided medical care for this population during the study period. The model diabetes program, started in 1979, included salary support for physicians, diabetes educators, nutritionists, and podiatrists, and culturally appropriate educational materials.⁹ Because of the large number of people with diabetes in this community, people who had had diabetes for less than 5 years were the central focus of the program. During the early years of the program, a podiatrist was in attendance once a week. In 1988 a full-time podiatrist joined the medical staff, and another joined in 1991. Patients with diabetes for more than 5 years and those with renal, cardiac, or other medical complications received care in the general medicine clinic but could also be seen in the model program clinic. Hospitalization for simple conditions was provided in the community at Hu Hu Kam Memorial Hospital and for more complicated conditions or surgical care at the Phoenix Indian Medical Center, 45 miles away. Clinicians in all health care settings were encouraged to conduct foot examinations on all patients with diabetes. The adherence to these recommendations was monitored with an annual chart audit that began in 1985.^10,11

Patients eligible for the study: (1) had diabetes according to World Health Organization criteria,^12,13 (2) lived in districts 1 through 5 of the reservation, (3) were 50% or more Pima or closely related Tohono O’odham Indian, (4) were aged between 25 and 85 years, and (5) participated in the longitudinal diabetes study conducted by the National Institutes of Health. The date of onset of each patient’s diabetes was established at these research examinations or between examinations during the course of routine medical care. Case patients had experienced a first nontraumatic amputation of the lower extremity between January 1, 1985, and December 31, 1992, and control patients had no lower-extremity amputation by December 31, 1992.

Medical records from Hu Hu Kam Memorial Hospital, Phoenix Indian Medical Center, and the Gila River home health agency were obtained by a nurse trained in data abstraction. The pivotal or precipitating event leading to an amputation was identified for each case, and the date of the event was recorded after confirmation by a study podiatrist. A “pivotal event” has been defined as one that triggers others, culminating in an amputation.¹⁴ Examples include acute minor trauma (stepping on a tack) or repetitive minor trauma (new shoes creating a blister). The pivotal event date was then assigned to 3 randomly selected control patients for every case patient.

Typically, a pivotal event results in a break in the cutaneous barrier, leading to a wound or ulcer, which in turn increases health care use and alters the focus of preventive efforts. Because we were interested in the preventive effect of examinations, we restricted our data collection to the 36 months before the pivotal event. All health care use, including ambulatory visits, hospitalizations, and home health care, was abstracted for the 36-month period before the pivotal event. The number of visits to each type of clinic was recorded along with the number of failed (or no-show) appointments.

Every foot examination was abstracted for clinic type, provider discipline, type of examination, findings, and therapeutic interventions. Three types of preventive foot examination were defined: (1) foot scan-a visual scan of the skin for breaks in the cutaneous barrier only; (2) comprehensive foot examination-foot scan plus evaluation of bony deformities and neurologic and vascular status; and (3) therapeutic examination-an examination during a therapeutic maneuver, such as debridement of callus or thick nails, prescription or dispensing of therapeutic footwear, or surveillance of the site of a healed foot ulcer. All examinations for foot wound management (acute injury, chronic foot ulcers, and a final visit to confirm wound healing) or for monitoring pedal edema were excluded.

Patients occasionally had foot examinations by more than one provider on the same day. For example, a patient with a new foot wound might be examined first by a nurse, then by a physician, and finally by a podiatrist. Because this team management approach might inflate the number of preventive examinations, we considered multiple foot examinations on the same day as a single one and assigned it to the provider with the most foot-specific training according to the following hierarchy: (1) health aide, nurse, dietician, pharmacist, or physician assistant; (2) physician; and (3) podiatrist, orthopedic surgeon, or physical therapist. For the same reason, all foot examinations during a hospitalization were counted as only one.

All instances of nail and callus care, advice and fitting of therapeutic footwear, and education on foot care were abstracted, including interventions provided during ulcer care or hospitalization. Any written comment on nonadherence with foot care recommendations or diabetic medication from any visit was also noted.

Health conditions and diabetes complications (diabetic retinopathy, nephropathy, cardiovascular disease) diagnosed before the pivotal event date were recorded,¹⁵ as were the values for the first 3 blood glucose determinations in each of the 3 years preceding that same event.

We compared means of continuous variables with t tests, and categorical variables with chi-square tests. Health care use variables with a large proportion of 0 values were stratified and compared with chi-square tests. A previously developed logistic model controlled for differences in demographics, diabetes severity, and foot risk conditions.¹⁵ We added preventive foot care and patient nonadherence to recommendations to this base model. Competing non-nested models incorporating the 3 types of preventive foot examination variables, either separately or combined, were compared using Schwarz’s Bayesian criterion¹⁶ to identify the best means of modeling preventive foot examinations.

Results

Sixty-one first nontraumatic amputations of the lower extremity were identified.¹⁵ The clinical characteristics of the 61 case patients and 183 control patients are shown in Table 1.

The 61 case patients and 183 control patients received 1857 foot examinations during the 36 months before the pivotal event. Almost one third of the foot examinations were for wound and ulcer care. The number of foot examinations, by type and provider, are shown in Table 2.

After excluding the duplicate examinations conducted on the same day and any examinations for wound care, 1166 preventive examinations were performed during the 36 months of assessment. The distribution of these preventive foot examinations for all patients is shown in Table 3. Case patients were more likely to receive a foot scan or a therapeutic intervention (nonulceration care). Foot scans were performed at least once during the 36 months in 87% of the case patients and 72% of the control patients. Thirty-eight percent of the case patients received one or more therapeutic interventions, compared with only 17% of the control patients. One third of each group received at least one comprehensive examination during the assessment period. The median number of preventive foot examinations was 7 for case patients and 3 for control patients.

Specific therapeutic interventions, including debridement of callus and nails, foot care education, and recommendations and fitting for therapeutic footwear, are shown in Table 4. Foot education was recorded at least once during the 3-year period for 44% of the case patients and 32% of the control patients. Interventions included prescriptions for shoe inserts (15% vs 8%) and recommendations for shoe changes (17% vs 8%). Six subjects with Charcot deformity received molded shoes, and 2 others received in-depth shoes (shoes with extra room over the toes). Education on foot care and footwear was recorded for 39% of the case patients and 21% of the control patients. After controlling for differences in foot risk conditions, foot care education did not differ between the groups (data not shown). Nonadherence with recommendations for foot care or diabetes medication was noted for 41% of the case patients and 23% of the control patients.

The independent effect of foot examinations on the risk of amputation was examined in a logistic model that controlled for the differences in demographics, diabetes severity, and foot risk conditions. The 3 types of preventive foot examinations (scans, comprehensive, and therapeutic) were modeled separately and combined as continuous, stratified, and dichotomized variables. We also explored the impact of examinations in the last year versus the last 36 months. The best fitting model combined preventive foot examinations dichotomized at none versus 1 or more examinations during the observation period Table 5. Receiving 1 or more foot care examinations during the 3 years was suggestive of a benefit (odds ratio [OR]=0.55; 95% confidence interval [CI], 0.17-1.7; P=.31), but the result was not statistically significant. Nonadherence with foot care recommendations or medication was suggestive of an increased risk of amputation (OR=1.9; 95% CI, 0.88-4.3; P=.10), but the effect estimate was not statistically significant. Patient education was not associated with any change in amputation risk, so it was dropped from the final model. No effect modification (interaction) was noted between sex, age, and preventive care examinations.

Discussion

Previous research on foot care has rarely focused on the type, content, and effectiveness of foot examinations and foot care. We attempted to address the limitations of previous foot care evaluations by categorizing the preventive foot examination into 1 of 3 types (scan, comprehensive, therapeutic), identifying and excluding all wound care, and recording all educational and therapeutic interventions. We identified a median of 7 preventive foot examinations for case patients and 3 preventive foot examinations for control patients during the evaluation period. Case patients had their feet examined at approximately half of all medical care visits, and the control patients had a foot examination during approximately one fourth of all visits (including visits at the ophthalmology, renal, and cardiology clinics), suggesting a concerted effort by all providers to examine the feet of patients with diabetes. These examination rates were similar to rates obtained from audits of other primary care settings,^11,17,18 which found that approximately 50% of the population with diabetes reported a foot examination in the past year.

After adjusting for differences in demographics, foot risk conditions, and disease severity, we found that preventive foot examinations in Pima Indians with diabetes may have provided a reduced risk of lower-extremity amputation (OR=.55; 95% CI, 0.17-1.7), but our effect estimate was not statistically significant. Our finding does not preclude the possibility that foot examinations actually increase the risk of amputation, but this is an improbable interpretation. It should be noted that our estimate is of the same magnitude of published reports: a 44% to 85% decline in the incidence of new ulcers or amputation from integrated diabetic foot care programs.^2-6

Risk Identification

Foot examinations are the means for risk identification and should stimulate proven preventive care efforts. Therapeutic footwear, including cushioned inserts, has been shown to be highly effective in preventing ulceration in patients with neuropathy or previous ulceration.^19,20 In our study, shoe inserts were prescribed for 9 case patients and 15 control patients, and shoe changes were recommended 21 times for case patients and 19 times for control patients (primarily for in-depth shoes). However, most patients did not obtain the recommended inserts, only 2 received in-depth shoes, and 6 persons with Charcot foot deformities received a custom shoe. Therapeutic footwear would probably have been indicated for most of the patients with foot ulcers (33 case patients and 8 control patients), foot deformities (19 case patients and 6 control patients), and many of the patients with neuropathy (43 case patients and 14 control patients). The limited availability of therapeutic footwear during the study interval may have reduced the apparent effectiveness of foot examinations in preventing amputation.

Foot Care Education

Other studies have shown that education on footwear and foot care as a sole intervention is effective in reducing the risk of subsequent ulceration and amputation.²¹ In our study, education on foot care and footwear was recorded 1 or more times for 44% of the case patients and 32% of the control patients, but after controlling for foot risk conditions, foot care education was not significantly different between the groups. Education may have been provided more frequently, but if not recorded in the medical record it would not have been identified. Nonadherence to foot care recommendations, which is related to educational efforts, was associated with an amputation risk OR of 1.9 (95% CI, 0.9-4.3).

Limitations

Our attempt to identify the independent effect of foot examination on amputation risk was complicated by methodologic difficulties. Case patients had more foot risk conditions, foot ulcers, diabetes complications, and longer diabetes duration than control patients, all of which may have increased the opportunities for foot examinations. We attempted to control the potential for confounding by indication by adjusting for the differences in disease severity, and we carefully excluded all visits for ulcer care. Although our effect estimate was in the hypothesized direction, the results still lacked statistical significance. The lack of statistical significance most likely reflects the limited power of the study due to limited sample size and the high examination rate in both case and control patients (at least 1 preventive foot examination was recorded in 87% of case patients and 72% of the control patients). Other possibilities include inaccuracies in recording foot examinations. Omissions in recording foot examinations was probably decreased by the annual chart audit, but concern about the audit may have also led to the recording of care that was never performed. In addition, foot examination risk factors were available only on those who had had foot examinations, which limited our ability to control for this important confounder.

Conclusions

Current recommendations from the American Diabetes Association (ADA) suggest that a “comprehensive vascular, neurological, musculoskeletal, and skin and soft tissue evaluation should be done at least annually.”¹ In addition, patients with identified foot risks should be examined quarterly or at each routine diabetes visit several times a year. These recommendations were developed from expert opinion without the benefit of rigorous evidence. Our findings do not either support or refute these recommendations. However, foot examinations are the logical first step in identifying the patients most likely to benefit from specific interventions and preventive care. Future research conducted in a prospective fashion should examine the optimum frequency and type of examination and should incorporate the linkage of risk identification (foot examinations) to management (patient education and footwear) to fully support the current care recommendations.

Acknowledgments

This project was supported in part by the Indian Health Service Diabetes Program (Dr Mayfield) and a grant from the Agency for Health Care Policy and Research (HS 07238). We would also like to thank Ann Etheridge, RN, for her careful chart abstraction, Wes Yamada, DPM, for sharing his podiatric expertise, and Virginia Thomas for her assistance with data entry. Most important, we would like to thank the Pima Indians who graciously allowed us to work with them.

Frequent foot examinations are widely recommended as a means of reducing the risk of foot ulcers and amputation in patients with type 2 diabetes.¹ This recommendation is primarily based on reports from diabetic foot care programs that provided frequent foot examinations, custom therapeutic footwear, patient education on footwear and foot care, and access to a multidisciplinary team of providers.^2-6 None of these reports, however, attempted to identify the specific contribution of foot examinations to the overall success of the program or the optimum frequency of those examinations. There is little evidence to support the recommendation that primary care physicians should perform foot examinations at every visit; yet this recommendation has almost become a universal mandate of diabetes quality-of-care protocols. Furthermore, there is no evidence for what examination components should be included. We conducted a retrospective evaluation of a population-based foot care program to determine the specific contribution of foot examinations to the risk of amputation.

Methods

Pima Indians of the Gila River Indian community in Arizona have one of the world’s highest reported incidence rates of diabetes and diabetic amputation.^7,8 Previous studies of this population have identified the demographic, pathophysiologic, and diabetes-related risk factors for lower-extremity amputation.⁷ Members of this community have participated in a National Institutes of Health (NIH) longitudinal study of diabetes since 1965.⁸

The Indian Health Service, a branch of the US Public Health Service, provided medical care for this population during the study period. The model diabetes program, started in 1979, included salary support for physicians, diabetes educators, nutritionists, and podiatrists, and culturally appropriate educational materials.⁹ Because of the large number of people with diabetes in this community, people who had had diabetes for less than 5 years were the central focus of the program. During the early years of the program, a podiatrist was in attendance once a week. In 1988 a full-time podiatrist joined the medical staff, and another joined in 1991. Patients with diabetes for more than 5 years and those with renal, cardiac, or other medical complications received care in the general medicine clinic but could also be seen in the model program clinic. Hospitalization for simple conditions was provided in the community at Hu Hu Kam Memorial Hospital and for more complicated conditions or surgical care at the Phoenix Indian Medical Center, 45 miles away. Clinicians in all health care settings were encouraged to conduct foot examinations on all patients with diabetes. The adherence to these recommendations was monitored with an annual chart audit that began in 1985.^10,11

Patients eligible for the study: (1) had diabetes according to World Health Organization criteria,^12,13 (2) lived in districts 1 through 5 of the reservation, (3) were 50% or more Pima or closely related Tohono O’odham Indian, (4) were aged between 25 and 85 years, and (5) participated in the longitudinal diabetes study conducted by the National Institutes of Health. The date of onset of each patient’s diabetes was established at these research examinations or between examinations during the course of routine medical care. Case patients had experienced a first nontraumatic amputation of the lower extremity between January 1, 1985, and December 31, 1992, and control patients had no lower-extremity amputation by December 31, 1992.

Medical records from Hu Hu Kam Memorial Hospital, Phoenix Indian Medical Center, and the Gila River home health agency were obtained by a nurse trained in data abstraction. The pivotal or precipitating event leading to an amputation was identified for each case, and the date of the event was recorded after confirmation by a study podiatrist. A “pivotal event” has been defined as one that triggers others, culminating in an amputation.¹⁴ Examples include acute minor trauma (stepping on a tack) or repetitive minor trauma (new shoes creating a blister). The pivotal event date was then assigned to 3 randomly selected control patients for every case patient.

Typically, a pivotal event results in a break in the cutaneous barrier, leading to a wound or ulcer, which in turn increases health care use and alters the focus of preventive efforts. Because we were interested in the preventive effect of examinations, we restricted our data collection to the 36 months before the pivotal event. All health care use, including ambulatory visits, hospitalizations, and home health care, was abstracted for the 36-month period before the pivotal event. The number of visits to each type of clinic was recorded along with the number of failed (or no-show) appointments.

Every foot examination was abstracted for clinic type, provider discipline, type of examination, findings, and therapeutic interventions. Three types of preventive foot examination were defined: (1) foot scan-a visual scan of the skin for breaks in the cutaneous barrier only; (2) comprehensive foot examination-foot scan plus evaluation of bony deformities and neurologic and vascular status; and (3) therapeutic examination-an examination during a therapeutic maneuver, such as debridement of callus or thick nails, prescription or dispensing of therapeutic footwear, or surveillance of the site of a healed foot ulcer. All examinations for foot wound management (acute injury, chronic foot ulcers, and a final visit to confirm wound healing) or for monitoring pedal edema were excluded.

Patients occasionally had foot examinations by more than one provider on the same day. For example, a patient with a new foot wound might be examined first by a nurse, then by a physician, and finally by a podiatrist. Because this team management approach might inflate the number of preventive examinations, we considered multiple foot examinations on the same day as a single one and assigned it to the provider with the most foot-specific training according to the following hierarchy: (1) health aide, nurse, dietician, pharmacist, or physician assistant; (2) physician; and (3) podiatrist, orthopedic surgeon, or physical therapist. For the same reason, all foot examinations during a hospitalization were counted as only one.

All instances of nail and callus care, advice and fitting of therapeutic footwear, and education on foot care were abstracted, including interventions provided during ulcer care or hospitalization. Any written comment on nonadherence with foot care recommendations or diabetic medication from any visit was also noted.

Health conditions and diabetes complications (diabetic retinopathy, nephropathy, cardiovascular disease) diagnosed before the pivotal event date were recorded,¹⁵ as were the values for the first 3 blood glucose determinations in each of the 3 years preceding that same event.

We compared means of continuous variables with t tests, and categorical variables with chi-square tests. Health care use variables with a large proportion of 0 values were stratified and compared with chi-square tests. A previously developed logistic model controlled for differences in demographics, diabetes severity, and foot risk conditions.¹⁵ We added preventive foot care and patient nonadherence to recommendations to this base model. Competing non-nested models incorporating the 3 types of preventive foot examination variables, either separately or combined, were compared using Schwarz’s Bayesian criterion¹⁶ to identify the best means of modeling preventive foot examinations.

Results

Sixty-one first nontraumatic amputations of the lower extremity were identified.¹⁵ The clinical characteristics of the 61 case patients and 183 control patients are shown in Table 1.

The 61 case patients and 183 control patients received 1857 foot examinations during the 36 months before the pivotal event. Almost one third of the foot examinations were for wound and ulcer care. The number of foot examinations, by type and provider, are shown in Table 2.

After excluding the duplicate examinations conducted on the same day and any examinations for wound care, 1166 preventive examinations were performed during the 36 months of assessment. The distribution of these preventive foot examinations for all patients is shown in Table 3. Case patients were more likely to receive a foot scan or a therapeutic intervention (nonulceration care). Foot scans were performed at least once during the 36 months in 87% of the case patients and 72% of the control patients. Thirty-eight percent of the case patients received one or more therapeutic interventions, compared with only 17% of the control patients. One third of each group received at least one comprehensive examination during the assessment period. The median number of preventive foot examinations was 7 for case patients and 3 for control patients.

Specific therapeutic interventions, including debridement of callus and nails, foot care education, and recommendations and fitting for therapeutic footwear, are shown in Table 4. Foot education was recorded at least once during the 3-year period for 44% of the case patients and 32% of the control patients. Interventions included prescriptions for shoe inserts (15% vs 8%) and recommendations for shoe changes (17% vs 8%). Six subjects with Charcot deformity received molded shoes, and 2 others received in-depth shoes (shoes with extra room over the toes). Education on foot care and footwear was recorded for 39% of the case patients and 21% of the control patients. After controlling for differences in foot risk conditions, foot care education did not differ between the groups (data not shown). Nonadherence with recommendations for foot care or diabetes medication was noted for 41% of the case patients and 23% of the control patients.

The independent effect of foot examinations on the risk of amputation was examined in a logistic model that controlled for the differences in demographics, diabetes severity, and foot risk conditions. The 3 types of preventive foot examinations (scans, comprehensive, and therapeutic) were modeled separately and combined as continuous, stratified, and dichotomized variables. We also explored the impact of examinations in the last year versus the last 36 months. The best fitting model combined preventive foot examinations dichotomized at none versus 1 or more examinations during the observation period Table 5. Receiving 1 or more foot care examinations during the 3 years was suggestive of a benefit (odds ratio [OR]=0.55; 95% confidence interval [CI], 0.17-1.7; P=.31), but the result was not statistically significant. Nonadherence with foot care recommendations or medication was suggestive of an increased risk of amputation (OR=1.9; 95% CI, 0.88-4.3; P=.10), but the effect estimate was not statistically significant. Patient education was not associated with any change in amputation risk, so it was dropped from the final model. No effect modification (interaction) was noted between sex, age, and preventive care examinations.

Discussion

Previous research on foot care has rarely focused on the type, content, and effectiveness of foot examinations and foot care. We attempted to address the limitations of previous foot care evaluations by categorizing the preventive foot examination into 1 of 3 types (scan, comprehensive, therapeutic), identifying and excluding all wound care, and recording all educational and therapeutic interventions. We identified a median of 7 preventive foot examinations for case patients and 3 preventive foot examinations for control patients during the evaluation period. Case patients had their feet examined at approximately half of all medical care visits, and the control patients had a foot examination during approximately one fourth of all visits (including visits at the ophthalmology, renal, and cardiology clinics), suggesting a concerted effort by all providers to examine the feet of patients with diabetes. These examination rates were similar to rates obtained from audits of other primary care settings,^11,17,18 which found that approximately 50% of the population with diabetes reported a foot examination in the past year.

After adjusting for differences in demographics, foot risk conditions, and disease severity, we found that preventive foot examinations in Pima Indians with diabetes may have provided a reduced risk of lower-extremity amputation (OR=.55; 95% CI, 0.17-1.7), but our effect estimate was not statistically significant. Our finding does not preclude the possibility that foot examinations actually increase the risk of amputation, but this is an improbable interpretation. It should be noted that our estimate is of the same magnitude of published reports: a 44% to 85% decline in the incidence of new ulcers or amputation from integrated diabetic foot care programs.^2-6

Risk Identification

Foot examinations are the means for risk identification and should stimulate proven preventive care efforts. Therapeutic footwear, including cushioned inserts, has been shown to be highly effective in preventing ulceration in patients with neuropathy or previous ulceration.^19,20 In our study, shoe inserts were prescribed for 9 case patients and 15 control patients, and shoe changes were recommended 21 times for case patients and 19 times for control patients (primarily for in-depth shoes). However, most patients did not obtain the recommended inserts, only 2 received in-depth shoes, and 6 persons with Charcot foot deformities received a custom shoe. Therapeutic footwear would probably have been indicated for most of the patients with foot ulcers (33 case patients and 8 control patients), foot deformities (19 case patients and 6 control patients), and many of the patients with neuropathy (43 case patients and 14 control patients). The limited availability of therapeutic footwear during the study interval may have reduced the apparent effectiveness of foot examinations in preventing amputation.

Foot Care Education

Other studies have shown that education on footwear and foot care as a sole intervention is effective in reducing the risk of subsequent ulceration and amputation.²¹ In our study, education on foot care and footwear was recorded 1 or more times for 44% of the case patients and 32% of the control patients, but after controlling for foot risk conditions, foot care education was not significantly different between the groups. Education may have been provided more frequently, but if not recorded in the medical record it would not have been identified. Nonadherence to foot care recommendations, which is related to educational efforts, was associated with an amputation risk OR of 1.9 (95% CI, 0.9-4.3).

Limitations

Our attempt to identify the independent effect of foot examination on amputation risk was complicated by methodologic difficulties. Case patients had more foot risk conditions, foot ulcers, diabetes complications, and longer diabetes duration than control patients, all of which may have increased the opportunities for foot examinations. We attempted to control the potential for confounding by indication by adjusting for the differences in disease severity, and we carefully excluded all visits for ulcer care. Although our effect estimate was in the hypothesized direction, the results still lacked statistical significance. The lack of statistical significance most likely reflects the limited power of the study due to limited sample size and the high examination rate in both case and control patients (at least 1 preventive foot examination was recorded in 87% of case patients and 72% of the control patients). Other possibilities include inaccuracies in recording foot examinations. Omissions in recording foot examinations was probably decreased by the annual chart audit, but concern about the audit may have also led to the recording of care that was never performed. In addition, foot examination risk factors were available only on those who had had foot examinations, which limited our ability to control for this important confounder.

Conclusions

Current recommendations from the American Diabetes Association (ADA) suggest that a “comprehensive vascular, neurological, musculoskeletal, and skin and soft tissue evaluation should be done at least annually.”¹ In addition, patients with identified foot risks should be examined quarterly or at each routine diabetes visit several times a year. These recommendations were developed from expert opinion without the benefit of rigorous evidence. Our findings do not either support or refute these recommendations. However, foot examinations are the logical first step in identifying the patients most likely to benefit from specific interventions and preventive care. Future research conducted in a prospective fashion should examine the optimum frequency and type of examination and should incorporate the linkage of risk identification (foot examinations) to management (patient education and footwear) to fully support the current care recommendations.

Acknowledgments

This project was supported in part by the Indian Health Service Diabetes Program (Dr Mayfield) and a grant from the Agency for Health Care Policy and Research (HS 07238). We would also like to thank Ann Etheridge, RN, for her careful chart abstraction, Wes Yamada, DPM, for sharing his podiatric expertise, and Virginia Thomas for her assistance with data entry. Most important, we would like to thank the Pima Indians who graciously allowed us to work with them.

Frequent foot examinations are widely recommended as a means of reducing the risk of foot ulcers and amputation in patients with type 2 diabetes.¹ This recommendation is primarily based on reports from diabetic foot care programs that provided frequent foot examinations, custom therapeutic footwear, patient education on footwear and foot care, and access to a multidisciplinary team of providers.^2-6 None of these reports, however, attempted to identify the specific contribution of foot examinations to the overall success of the program or the optimum frequency of those examinations. There is little evidence to support the recommendation that primary care physicians should perform foot examinations at every visit; yet this recommendation has almost become a universal mandate of diabetes quality-of-care protocols. Furthermore, there is no evidence for what examination components should be included. We conducted a retrospective evaluation of a population-based foot care program to determine the specific contribution of foot examinations to the risk of amputation.

Methods

Pima Indians of the Gila River Indian community in Arizona have one of the world’s highest reported incidence rates of diabetes and diabetic amputation.^7,8 Previous studies of this population have identified the demographic, pathophysiologic, and diabetes-related risk factors for lower-extremity amputation.⁷ Members of this community have participated in a National Institutes of Health (NIH) longitudinal study of diabetes since 1965.⁸

The Indian Health Service, a branch of the US Public Health Service, provided medical care for this population during the study period. The model diabetes program, started in 1979, included salary support for physicians, diabetes educators, nutritionists, and podiatrists, and culturally appropriate educational materials.⁹ Because of the large number of people with diabetes in this community, people who had had diabetes for less than 5 years were the central focus of the program. During the early years of the program, a podiatrist was in attendance once a week. In 1988 a full-time podiatrist joined the medical staff, and another joined in 1991. Patients with diabetes for more than 5 years and those with renal, cardiac, or other medical complications received care in the general medicine clinic but could also be seen in the model program clinic. Hospitalization for simple conditions was provided in the community at Hu Hu Kam Memorial Hospital and for more complicated conditions or surgical care at the Phoenix Indian Medical Center, 45 miles away. Clinicians in all health care settings were encouraged to conduct foot examinations on all patients with diabetes. The adherence to these recommendations was monitored with an annual chart audit that began in 1985.^10,11

Patients eligible for the study: (1) had diabetes according to World Health Organization criteria,^12,13 (2) lived in districts 1 through 5 of the reservation, (3) were 50% or more Pima or closely related Tohono O’odham Indian, (4) were aged between 25 and 85 years, and (5) participated in the longitudinal diabetes study conducted by the National Institutes of Health. The date of onset of each patient’s diabetes was established at these research examinations or between examinations during the course of routine medical care. Case patients had experienced a first nontraumatic amputation of the lower extremity between January 1, 1985, and December 31, 1992, and control patients had no lower-extremity amputation by December 31, 1992.

Medical records from Hu Hu Kam Memorial Hospital, Phoenix Indian Medical Center, and the Gila River home health agency were obtained by a nurse trained in data abstraction. The pivotal or precipitating event leading to an amputation was identified for each case, and the date of the event was recorded after confirmation by a study podiatrist. A “pivotal event” has been defined as one that triggers others, culminating in an amputation.¹⁴ Examples include acute minor trauma (stepping on a tack) or repetitive minor trauma (new shoes creating a blister). The pivotal event date was then assigned to 3 randomly selected control patients for every case patient.

Typically, a pivotal event results in a break in the cutaneous barrier, leading to a wound or ulcer, which in turn increases health care use and alters the focus of preventive efforts. Because we were interested in the preventive effect of examinations, we restricted our data collection to the 36 months before the pivotal event. All health care use, including ambulatory visits, hospitalizations, and home health care, was abstracted for the 36-month period before the pivotal event. The number of visits to each type of clinic was recorded along with the number of failed (or no-show) appointments.

Every foot examination was abstracted for clinic type, provider discipline, type of examination, findings, and therapeutic interventions. Three types of preventive foot examination were defined: (1) foot scan-a visual scan of the skin for breaks in the cutaneous barrier only; (2) comprehensive foot examination-foot scan plus evaluation of bony deformities and neurologic and vascular status; and (3) therapeutic examination-an examination during a therapeutic maneuver, such as debridement of callus or thick nails, prescription or dispensing of therapeutic footwear, or surveillance of the site of a healed foot ulcer. All examinations for foot wound management (acute injury, chronic foot ulcers, and a final visit to confirm wound healing) or for monitoring pedal edema were excluded.

Patients occasionally had foot examinations by more than one provider on the same day. For example, a patient with a new foot wound might be examined first by a nurse, then by a physician, and finally by a podiatrist. Because this team management approach might inflate the number of preventive examinations, we considered multiple foot examinations on the same day as a single one and assigned it to the provider with the most foot-specific training according to the following hierarchy: (1) health aide, nurse, dietician, pharmacist, or physician assistant; (2) physician; and (3) podiatrist, orthopedic surgeon, or physical therapist. For the same reason, all foot examinations during a hospitalization were counted as only one.

All instances of nail and callus care, advice and fitting of therapeutic footwear, and education on foot care were abstracted, including interventions provided during ulcer care or hospitalization. Any written comment on nonadherence with foot care recommendations or diabetic medication from any visit was also noted.

Health conditions and diabetes complications (diabetic retinopathy, nephropathy, cardiovascular disease) diagnosed before the pivotal event date were recorded,¹⁵ as were the values for the first 3 blood glucose determinations in each of the 3 years preceding that same event.

We compared means of continuous variables with t tests, and categorical variables with chi-square tests. Health care use variables with a large proportion of 0 values were stratified and compared with chi-square tests. A previously developed logistic model controlled for differences in demographics, diabetes severity, and foot risk conditions.¹⁵ We added preventive foot care and patient nonadherence to recommendations to this base model. Competing non-nested models incorporating the 3 types of preventive foot examination variables, either separately or combined, were compared using Schwarz’s Bayesian criterion¹⁶ to identify the best means of modeling preventive foot examinations.

Results

Sixty-one first nontraumatic amputations of the lower extremity were identified.¹⁵ The clinical characteristics of the 61 case patients and 183 control patients are shown in Table 1.

The 61 case patients and 183 control patients received 1857 foot examinations during the 36 months before the pivotal event. Almost one third of the foot examinations were for wound and ulcer care. The number of foot examinations, by type and provider, are shown in Table 2.

After excluding the duplicate examinations conducted on the same day and any examinations for wound care, 1166 preventive examinations were performed during the 36 months of assessment. The distribution of these preventive foot examinations for all patients is shown in Table 3. Case patients were more likely to receive a foot scan or a therapeutic intervention (nonulceration care). Foot scans were performed at least once during the 36 months in 87% of the case patients and 72% of the control patients. Thirty-eight percent of the case patients received one or more therapeutic interventions, compared with only 17% of the control patients. One third of each group received at least one comprehensive examination during the assessment period. The median number of preventive foot examinations was 7 for case patients and 3 for control patients.

Specific therapeutic interventions, including debridement of callus and nails, foot care education, and recommendations and fitting for therapeutic footwear, are shown in Table 4. Foot education was recorded at least once during the 3-year period for 44% of the case patients and 32% of the control patients. Interventions included prescriptions for shoe inserts (15% vs 8%) and recommendations for shoe changes (17% vs 8%). Six subjects with Charcot deformity received molded shoes, and 2 others received in-depth shoes (shoes with extra room over the toes). Education on foot care and footwear was recorded for 39% of the case patients and 21% of the control patients. After controlling for differences in foot risk conditions, foot care education did not differ between the groups (data not shown). Nonadherence with recommendations for foot care or diabetes medication was noted for 41% of the case patients and 23% of the control patients.

The independent effect of foot examinations on the risk of amputation was examined in a logistic model that controlled for the differences in demographics, diabetes severity, and foot risk conditions. The 3 types of preventive foot examinations (scans, comprehensive, and therapeutic) were modeled separately and combined as continuous, stratified, and dichotomized variables. We also explored the impact of examinations in the last year versus the last 36 months. The best fitting model combined preventive foot examinations dichotomized at none versus 1 or more examinations during the observation period Table 5. Receiving 1 or more foot care examinations during the 3 years was suggestive of a benefit (odds ratio [OR]=0.55; 95% confidence interval [CI], 0.17-1.7; P=.31), but the result was not statistically significant. Nonadherence with foot care recommendations or medication was suggestive of an increased risk of amputation (OR=1.9; 95% CI, 0.88-4.3; P=.10), but the effect estimate was not statistically significant. Patient education was not associated with any change in amputation risk, so it was dropped from the final model. No effect modification (interaction) was noted between sex, age, and preventive care examinations.

Discussion

Previous research on foot care has rarely focused on the type, content, and effectiveness of foot examinations and foot care. We attempted to address the limitations of previous foot care evaluations by categorizing the preventive foot examination into 1 of 3 types (scan, comprehensive, therapeutic), identifying and excluding all wound care, and recording all educational and therapeutic interventions. We identified a median of 7 preventive foot examinations for case patients and 3 preventive foot examinations for control patients during the evaluation period. Case patients had their feet examined at approximately half of all medical care visits, and the control patients had a foot examination during approximately one fourth of all visits (including visits at the ophthalmology, renal, and cardiology clinics), suggesting a concerted effort by all providers to examine the feet of patients with diabetes. These examination rates were similar to rates obtained from audits of other primary care settings,^11,17,18 which found that approximately 50% of the population with diabetes reported a foot examination in the past year.

After adjusting for differences in demographics, foot risk conditions, and disease severity, we found that preventive foot examinations in Pima Indians with diabetes may have provided a reduced risk of lower-extremity amputation (OR=.55; 95% CI, 0.17-1.7), but our effect estimate was not statistically significant. Our finding does not preclude the possibility that foot examinations actually increase the risk of amputation, but this is an improbable interpretation. It should be noted that our estimate is of the same magnitude of published reports: a 44% to 85% decline in the incidence of new ulcers or amputation from integrated diabetic foot care programs.^2-6

Risk Identification

Foot examinations are the means for risk identification and should stimulate proven preventive care efforts. Therapeutic footwear, including cushioned inserts, has been shown to be highly effective in preventing ulceration in patients with neuropathy or previous ulceration.^19,20 In our study, shoe inserts were prescribed for 9 case patients and 15 control patients, and shoe changes were recommended 21 times for case patients and 19 times for control patients (primarily for in-depth shoes). However, most patients did not obtain the recommended inserts, only 2 received in-depth shoes, and 6 persons with Charcot foot deformities received a custom shoe. Therapeutic footwear would probably have been indicated for most of the patients with foot ulcers (33 case patients and 8 control patients), foot deformities (19 case patients and 6 control patients), and many of the patients with neuropathy (43 case patients and 14 control patients). The limited availability of therapeutic footwear during the study interval may have reduced the apparent effectiveness of foot examinations in preventing amputation.

Foot Care Education

Other studies have shown that education on footwear and foot care as a sole intervention is effective in reducing the risk of subsequent ulceration and amputation.²¹ In our study, education on foot care and footwear was recorded 1 or more times for 44% of the case patients and 32% of the control patients, but after controlling for foot risk conditions, foot care education was not significantly different between the groups. Education may have been provided more frequently, but if not recorded in the medical record it would not have been identified. Nonadherence to foot care recommendations, which is related to educational efforts, was associated with an amputation risk OR of 1.9 (95% CI, 0.9-4.3).

Limitations

Our attempt to identify the independent effect of foot examination on amputation risk was complicated by methodologic difficulties. Case patients had more foot risk conditions, foot ulcers, diabetes complications, and longer diabetes duration than control patients, all of which may have increased the opportunities for foot examinations. We attempted to control the potential for confounding by indication by adjusting for the differences in disease severity, and we carefully excluded all visits for ulcer care. Although our effect estimate was in the hypothesized direction, the results still lacked statistical significance. The lack of statistical significance most likely reflects the limited power of the study due to limited sample size and the high examination rate in both case and control patients (at least 1 preventive foot examination was recorded in 87% of case patients and 72% of the control patients). Other possibilities include inaccuracies in recording foot examinations. Omissions in recording foot examinations was probably decreased by the annual chart audit, but concern about the audit may have also led to the recording of care that was never performed. In addition, foot examination risk factors were available only on those who had had foot examinations, which limited our ability to control for this important confounder.

Conclusions

Current recommendations from the American Diabetes Association (ADA) suggest that a “comprehensive vascular, neurological, musculoskeletal, and skin and soft tissue evaluation should be done at least annually.”¹ In addition, patients with identified foot risks should be examined quarterly or at each routine diabetes visit several times a year. These recommendations were developed from expert opinion without the benefit of rigorous evidence. Our findings do not either support or refute these recommendations. However, foot examinations are the logical first step in identifying the patients most likely to benefit from specific interventions and preventive care. Future research conducted in a prospective fashion should examine the optimum frequency and type of examination and should incorporate the linkage of risk identification (foot examinations) to management (patient education and footwear) to fully support the current care recommendations.

Acknowledgments

This project was supported in part by the Indian Health Service Diabetes Program (Dr Mayfield) and a grant from the Agency for Health Care Policy and Research (HS 07238). We would also like to thank Ann Etheridge, RN, for her careful chart abstraction, Wes Yamada, DPM, for sharing his podiatric expertise, and Virginia Thomas for her assistance with data entry. Most important, we would like to thank the Pima Indians who graciously allowed us to work with them.