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.