Abstract
Background:
Socioeconomic disadvantage is a known contributor to adverse events and higher admission rates in the diabetic population. However, its impact on outcomes after lower extremity amputation is unclear. We aimed to assess the association of geographic socioeconomic disadvantage with short- and long-term outcomes after minor amputation in patients with diabetes.
Materials and methods:
Geographic socioeconomic disadvantage was determined using the area deprivation index (ADI). All patients from the Maryland Health Services Cost Review Commission database (2012–2019) who underwent minor amputation with a concurrent diagnosis of diabetes were included and stratified by the ADI quartile. Associations of the ADI quartile with 30-day readmission and 1-year reamputation were evaluated using Kaplan-Meier survival analyses and multivariable logistic regression models adjusting for baseline differences.
Results:
A total of 7415 patients with diabetes underwent minor amputation (70.1% male, 38.7% black race), including 28.1% ADI1 (least deprived), 42.8% ADI2, 22.9% ADI3, and 6.2% ADI4 (most deprived). After adjusting for demographic and clinical factors, the odds of 30-day readmission were greater in the intermediate ADI groups than those in the ADI1 group, but not among the most deprived. Adjusted odds of 1-year reamputation were greater among ADI4 than those among ADI1. Kaplan-Meier analysis confirmed a greater likelihood of reamputation with an increasing ADI quartile over a 1-year period (P < 0.001).
Conclusions:
Geographic socioeconomic disadvantage is independently associated with both short- and long-term outcomes after minor diabetic amputations in Maryland. A targeted approach addressing the health care needs of deprived regions may be beneficial in optimizing postoperative care in this vulnerable population.
Keywords: Area deprivation index, Minor amputation, Diabetes, Readmission, Reamputation
Introduction
Diabetic foot ulcers (DFUs) are a prevalent and devastating sequela of diabetes mellitus that are associated with poor quality of life, frequent hospitalization, rising costs of treatment, and high mortality rates.1–4 DFU progression frequently leads to lower extremity (LE) amputation, and as a result, over 60,000 diabetes-related amputations are performed annually in the United States alone.5 Prognosis after diabetic amputation is poor, with 1-year mortality after major LE amputation as high as 48% and serious morbidity occurring in approximately 67% of affected patients.6,7 The risk of reamputation for patients with diabetes who undergo amputation is also high; Skoutas et al. demonstrated that 22% of patients with DFU with prior foot amputation required reamputation after a mean follow-up period of 18 months.8 Thus, there is significant interest in optimizing the care of patients after diabetic amputation to ameliorate its high morbidity and mortality.
Socioeconomic factors, including household and neighborhood income, payer status, and education are known predictors of outcomes in surgery.9–12 However, socioeconomic status is a complex and multifactorial construct that cannot be adequately represented by any singular measure. The area deprivation index (ADI) is an aggregate measure of geographical socioeconomic disadvantage that encompasses multiple domains including area household income, education, employment, and housing quality. Initially characterized by Singh in 2003,13 the ADI holds significant promise in disparity outcomes research by integrating elements of both personal and neighborhood disadvantage specific to a relatively small geographic region using patients’ residential zip +4 codes.13,14
Previously, the ADI has been associated with increased incidence of multiple diseases, mortality risk, hospital admission, and readmission.13–16 However, the association of neighborhood disadvantage with outcomes after diabetic LE amputations is still poorly understood. The aims of this study were twofold. First, we examined the association of the ADI with 30-day readmission in patients with diabetes who underwent minor LE amputation. Second, we examined the association of the ADI with 1-year reamputation in patients with diabetes undergoing minor amputation.
Materials and methods
Data source
We performed a retrospective analysis of records from the Maryland Health Services Cost Review Commission (MD HSCRC) database between July 1, 2012 and Jan 31, 2019. The HSCRC database was established by the state in an effort to improve outcomes and reduce the growth in health care spending in the context of Maryland’s unique all-payer model.17 The HSCRC collects detailed medical and billing data on all inpatient and outpatient medical services performed within Maryland. The study design and methods for data collection were approved by the Johns Hopkins University School of Medicine Institutional Review Board.
Inclusion criteria and factors
All diagnoses, procedures, and comorbidities in this study were defined using International Classification of Disease, ninth and 10th edition, Clinical Modification codes (Table S1). All inpatients with a diagnosis of diabetes mellitus who underwent a minor LE amputation were included. Minor amputation was defined as any amputation below the level of the ankle. Patients undergoing major amputation (n = 2851), those missing a residential zip code (necessary to calculate the ADI; n = 486), and those missing additional key demographic data (n = 2) were excluded.
We calculated the ADI for each patient based on their residential zip code as described previously by Kind et al.14 All 9-digit zip code ADI values were averaged within their respective 5-digit zip code areas to accommodate HSCRC data.18 Patients were subsequently stratified into four quartiles based on their ADI percentile [ADI1 (least deprived): 0–25, ADI2: 26–50, ADI3: 51–75, ADI4 (most deprived): 76–100].
Other patient factors that we included in our analysis included age (categorized as 18–39 years, 40–64 years, and ≥65 years), sex, race, payer status (private, Medicare, Medicaid, other, uninsured), and smoking status (never, current, former). We assessed clinical comorbidities including hypertension (HTN), dyslipidemia, congestive heart failure (CHF), coronary artery disease (CAD), peripheral artery disease (PAD), chronic kidney disease (CKD), peripheral neuropathy, and chronic obstructive pulmonary disease (COPD). We also assessed the number of (LE) endovascular and bypass procedures that patients underwent within the 30 days before surgery. Finally, we evaluated hospital performance for minor amputation; each hospital’s 30-day readmission rate after the index amputation was determined and then stratified into tertiles within our cohort (T1 = least readmissions, T3 = most readmissions).
Outcomes
The primary outcomes of this study were 30-day readmission and 1-year reamputation (either minor or major amputation). Each eligible patient was linked to a unique ID that allowed for identification of all future inpatient admissions and procedures. Thirty-day readmission was defined as the presence of an inpatient record within 30 days of the discharge date of the index amputation. Similarly, 1-year reamputation was defined as the presence of an inpatient record within 1 year of the index amputation containing an International Classification of Disease, ninth and 10th edition, Clinical Modification procedure code for either a major or minor LE amputation.
Statistical analysis
Baseline characteristics for each ADI group were reported using % (count). Thirty-day readmission was reported as a binary outcome and compared between ADI quartiles using Pearson’s chi-squared test. Estimated 1-year reamputation rates were reported using Kaplan-Meier analyses with life tables and compared across ADI quartiles using log-rank tests. A nonparametric test for trend was performed to assess relationship between the ADI quartile and the primary outcomes. Univariable and multivariable logistic regression were used to identify risk factors associated with 30-day readmission and 1-year reamputation after minor amputation. All variables found to be statistically significant on univariable analysis were subsequently included as covariates in the multivariable models. Statistical significance was considered at P < 0.05. All analyses were performed with Stata/MP, version 15.0 (StataCorp, College Station, TX).
Results
Study cohort
A total of 7415 patients with diabetes underwent minor LE amputation during the study period (Table 1). A total of 2084 (28.1%) patients were classified as ADI1 (least deprived), 3172 (42.8%) were ADI2, 1701 (22.9%) were ADI3, and 458 (6.2%) patients were ADI4 (most deprived). The majority of patients were between 40 and 64 years of age (56.3%, n = 4171), male (70.1%, n = 5196), and white (52.3%, n = 3881). More than half of patients used Medicare as their primary payer (52.3%,n = 3881) and were never smokers (58.7%, n = 4352). Comorbid diseases, including HTN (64.3%, n = 4765), dyslipidemia (49.9%, n = 3702), PAD (45.9%, n = 3401), CKD (39.8%, n = 2949), and CAD (34.0%, n = 2518), were common. Thirteen percent (n = 973) of patients underwent a LE endovascular intervention 30 days before amputation, and 6.7% (n = 498) underwent a LE bypass.
Table 1 –
Demographic and clinical characteristics of 7589 patients with diabetes who underwent minor lower extremity amputation in Maryland (2013–2019), stratified by the ADI quartile.
| ADI percentile | ADI1 (least deprived) | ADI2 | ADI3 | ADI4 (most deprived) |
|---|---|---|---|---|
| Characteristics, % | n = 2084 (28.34%) | n = 3172 (43.16%) | n = 1701 (23.13%) | n = 458 (5.37%) |
| Age | ||||
| 18–39 | 2.30 | 4.19 | 5.11 | 8.08 |
| 40–64 | 49.62 | 56.94 | 60.73 | 65.07 |
| ≥65 | 48.08 | 38.87 | 34.16 | 26.86 |
| Sex | ||||
| Male | 72.74 | 68.85 | 70.25 | 65.72 |
| Female | 27.26 | 31.15 | 29.75 | 34.28 |
| Race | ||||
| White | 62.14 | 53.40 | 46.68 | 21.40 |
| Black | 29.99 | 36.25 | 45.33 | 70.74 |
| Other/unknown | 7.87 | 10.34 | 8.00 | 7.86 |
| Insurance | ||||
| Private | 28.89 | 25.57 | 19.17 | 15.50 |
| Medicare | 54.94 | 52.18 | 51.21 | 45.85 |
| Medicaid | 12.09 | 18.13 | 25.87 | 35.15 |
| Other | 1.06 | 1.36 | 0.65 | 0.66 |
| Uninsured | 3.02 | 2.77 | 3.12 | 2.84 |
| Smoking status | ||||
| Never | 62.52 | 59.90 | 52.79 | 54.80 |
| Current | 15.07 | 20.05 | 26.81 | 30.35 |
| Former | 22.41 | 20.05 | 20.40 | 14.85 |
| Comorbidities | ||||
| HTN | 63.63 | 63.62 | 65.78 | 65.94 |
| DLD | 50.29 | 49.02 | 52.44 | 45.20 |
| CHF | 21.59 | 21.28 | 21.93 | 20.09 |
| CAD | 36.32 | 34.21 | 32.75 | 25.98 |
| PAD | 46.79 | 45.40 | 46.09 | 44.10 |
| CKD | 42.42 | 38.30 | 39.80 | 37.77 |
| PN | 25.10 | 26.83 | 23.22 | 25.33 |
| COPD | 9.93 | 11.57 | 13.29 | 7.64 |
| LE endovascular procedure <30 days | 14.11 | 13.05 | 12.17 | 12.45 |
| LE bypass procedure <30 days | 5.52 | 6.56 | 8.23 | 7.64 |
| Hospital readmission rate, by tertile | ||||
| First | 44.58 | 28.66 | 22.28 | 14.85 |
| Second | 43.38 | 44.77 | 40.45 | 43.89 |
| Third | 12.04 | 26.58 | 37.27 | 41.27 |
Abbreviations: DLD = dyslipidemia; PN = peripheral neuropathy.
Crude outcomes
The incidence of 30-day readmission after minor LE amputation was 22.1% overall (n = 1635) and increased with the ADI quartile (P < 0.001 for trend; Table 2). The incidence of reamputation within 1 year of the original minor amputation across all ADI groups was 23.6% (n = 1747) and also increased with the ADI quartile (P < 0.001 for trend; Table 2). Kaplan-Meier analysis of reamputation rates confirmed that a higher ADI quartile (i.e., more deprivation) was associated with a higher rate of reamputation (P < 0.001; Fig. 1).
Table 2 –
Rates of 30-day readmission and 1-year reamputation after diabetic minor lower extremity amputation in Maryland (2013–2019), stratified by the ADI quartile.
| Event rate, n (%) | ADI1 | ADI2 | ADI3 | ADI4 | P | P-trend |
|---|---|---|---|---|---|---|
| (Least deprived) | (Most deprived) | |||||
| 30-day readmission | 409 (19.63) | 698 (22.01) | 417 (24.51) | 111 (24.24) | 0.002 | <0.001 |
| 1-year reamputation | 436 (20.92) | 730 (23.01) | 438 (25.75) | 143 (31.22) | <0.001 | <0.001 |
Fig. 1 –
The Kaplan-Meier curve showing association of the area deprivation index (ADI) with lower extremity reamputation after minor foot amputation in patients with diabetes. Patients with more deprivation (i.e., ADI 4) had a higher risk of reamputation than patients with less deprivation.
Risk factors associated with 30-day readmission after minor lower extremity amputation
Unadjusted logistic regression analysis demonstrated that ADI3 and ADI4 were both associated with higher odds of 30-day readmission than ADI1 (least deprived) (both, P < 0.05; Table 3). Other demographic factors associated with increased odds of 30-day readmission included older age, female sex, black race (versus white), and having Medicare or Medicaid insurance (versus private insurance) (all, P < 0.05; Table 3). Clinical comorbidities that were significantly associated with 30-day readmission included HTN, CHF, CAD, PAD, CKD, and COPD (all, P < 0.05; Table 3).
Table 3 –
Risk factors associated with 30-day readmission among patients with diabetes undergoing minor lower extremity amputation in Maryland (2013–2019).
| Characteristics | 30-day readmission | |||
|---|---|---|---|---|
| Unadjusted | Adjusted | |||
| OR (95% CI) | P | OR (95% CI) | P | |
| ADI quartile | ||||
| 1 | Ref | Ref | ||
| 2 | 1.16 (1.01, 1.32) | 0.039 | 1.15 (1.00, 1.32) | 0.059 |
| 3 | 1.33 (1.14, 1.55) | <0.001 | 1.28 (1.09, 1.50) | 0.003 |
| 4 | 1.31 (1.03, 1.66) | 0.027 | 1.25 (0.97, 1.61) | 0.081 |
| Age | ||||
| 18–39 | Ref | Ref | ||
| 40–64 | 1.04 (0.77, 1.39) | 0.815 | 0.93 (0.69, 1.26) | 0.648 |
| ≥65 | 1.42 (1.05, 1.91) | 0.021 | 0.95 (0.68, 1.31) | 0.739 |
| Sex | ||||
| Male | Ref | Ref | ||
| Female | 1.23 (1.09, 1.38) | 0.001 | 1.13 (1.00, 1.27) | 0.051 |
| Race | ||||
| White | Ref | Ref | ||
| Black | 1.29 (1.15, 1.45) | <0.001 | 1.21 (1.07, 1.38) | 0.002 |
| Other/unknown | 1.17 (0.96, 1.43) | 0.119 | 1.17 (0.95, 1.43) | 0.135 |
| Insurance | ||||
| Private | Ref | Ref | ||
| Medicare | 1.88 (1.62, 2.17) | <0.001 | 1.43 (1.20, 1.69) | <0.001 |
| Medicaid | 1.47 (1.23, 1.75) | <0.001 | 1.48 (1.15, 1.66) | 0.001 |
| Other | 1.16 (0.64, 2.10) | 0.618 | 1.17 (0.64, 2.13) | 0.610 |
| Uninsured | 0.90 (0.60, 1.34) | 0.604 | 0.96 (0.64, 1.44) | 0.829 |
| Smoking status | ||||
| Never | Ref | - | ||
| Current | 0.90 (0.78, 1.04) | 0.160 | - | |
| Former | 1.11 (0.97, 1.27) | 0.146 | - | |
| Comorbidities | ||||
| HTN | 0.86 (0.77, 0.96) | 0.008 | 0.93 (0.82, 1.05) | 0.225 |
| DLD | 1.01 (0.90, 1.12) | 0.924 | - | |
| CHF | 2.05 (1.81, 2.32) | <0.001 | 1.50 (1.31, 1.72) | <0.001 |
| CAD | 1.65 (1.47, 1.84) | <0.001 | 1.26 (1.11, 1.43) | <0.001 |
| PAD | 1.62 (1.45, 1.80) | <0.001 | 1.38 (1.22, 1.56) | <0.001 |
| CKD | 1.71 (1.53, 1.92) | <0.001 | 1.29 (1.14, 1.46) | <0.001 |
| PN | 0.94 (0.82, 1.06) | 0.314 | - | |
| COPD | 1.70 (1.45, 1.99) | <0.001 | 1.38 (1.16, 1.62) | <0.001 |
Abbreviations: DLD = dyslipidemia; PN = peripheral neuropathy.
After adjusting for significant baseline differences between groups, multivariable analysis revealed that 30-day readmission was independently associated with ADI3 [versus ADI1; odds ratio (OR) 1.28, 95% confidence interval (CI) (1.09, 1.50)]. There was a nonsignificant association between 30-day readmission and ADI4 [versus ADI1; OR 1.25, 95% CI (0.97, 1.61); P = 0.08]. Other factors associated with 30-day readmission included black race [versus white race; OR 1.21, 95% CI (1.07, 1.38)], Medicare insurance [versus private; OR 1.43, 95% CI (1.20, 1.69)], Medicaid insurance [versus private; OR 1.38, 95% CI (1.15, 1.66)], CHF [OR 1.50, 95% CI (1.31, 1.72)], CAD [OR 1.26, 95% CI (1.11, 1.43)], PAD [OR 1.38, 95% CI (1.22, 1.56)], CKD [OR 1.29, 95% CI (1.14, 1.46)], and COPD [OR 1.38, 95% CI (1.16–1.62)].
Risk factors associated with 1-year reamputation
Based on unadjusted analysis, ADI3 and ADI4 (i.e., more deprived) were associated with significantly higher odds of reamputation within 1 year after minor amputation than ADI1 (both, P < 0.05; Table 4). Additional demographic factors associated with reamputation included black race (versus white race), having Medicare or Medicaid insurance (versus private insurance), and being a current or former smoker (all, P < 0.05; Table 4). Significant clinical factors associated with 1-year reamputation included CHF, CAD, PAD, and CKD (all, P < 0.05; Table 4). Undergoing amputation at a hospital with a higher readmission rate (i.e., T2 or T3) was also associated with 1-year reamputation (P < 0.05).
Table 4 –
Risk factors associated with 1-year reamputation among patients with diabetes undergoing minor lower extremity amputation in Maryland (2013–2019).
| Characteristics | 1-year reamputation | |||
|---|---|---|---|---|
| Unadjusted | Adjusted | |||
| OR (95% CI) | P | OR (95% CI) | P | |
| ADI quartile | ||||
| 1 | Ref | Ref | ||
| 2 | 1.13 (0.99, 1.29) | 0.074 | 1.05 (0.92, 1.21) | 0.475 |
| 3 | 1.31 (1.13, 1.53) | <0.001 | 1.12 (0.95, 1.31) | 0.168 |
| 4 | 1.72 (1.37, 2.15) | <0.001 | 1.40 (1.10, 1.77) | 0.006 |
| Age | ||||
| 18–39 | Ref | - | ||
| 40–64 | 1.03 (0.78, 1.36) | 0.828 | - | |
| ≥65 | 1.04 (0.79, 1.38) | 0.765 | - | |
| Sex | ||||
| Male | Ref | - | ||
| Female | 0.94 (0.84, 1.06) | 0.315 | - | |
| Race | ||||
| White | Ref | Ref | ||
| Black | 1.35 (1.21, 1.51) | <0.001 | 1.25 (1.11, 1.41) | <0.001 |
| Other/unknown | 1.03 (0.84, 1.25) | 0.794 | 0.97 (0.79, 1.19) | 0.741 |
| Insurance | ||||
| Private | Ref | Ref | ||
| Medicare | 1.45 (1.26, 1.66) | <0.001 | 1.22 (1.06, 1.41) | 0.006 |
| Medicaid | 1.36 (1.15, 1.61) | <0.001 | 1.19 (1.00, 1.42) | 0.048 |
| Other | 0.90 (0.50, 1.63) | 0.731 | 0.88 (0.49, 1.60) | 0.683 |
| Uninsured | 0.86 (0.59, 1.25) | 0.429 | 0.84 (0.58, 1.23) | 0.370 |
| Smoking status | ||||
| Never | Ref | Ref | ||
| Current | 1.36 (1.19, 1.55) | <0.001 | 1.37 (1.19, 1.58) | <0.001 |
| Former | 1.25 (1.09, 1.43) | 0.001 | 1.24 (1.08, 1.42) | 0.003 |
| Comorbidities | ||||
| HTN | 1.02 (0.91, 1.14) | 0.717 | - | |
| DLD | 1.01 (0.91, 1.13) | 0.793 | - | |
| CHF | 1.19 (1.04, 1.35) | 0.009 | 0.96 (0.83, 1.11) | 0.571 |
| CAD | 1.34 (1.20, 1.50) | <0.001 | 1.23 (1.09, 1.40) | 0.001 |
| PAD | 1.67 (1.50, 1.86) | <0.001 | 1.56 (1.40, 1.75) | <0.001 |
| CKD | 1.28 (1.15, 1.43) | <0.001 | 1.14 (1.01, 1.29) | 0.030 |
| PN | 0.99 (0.87, 1.12) | 0.845 | - | |
| COPD | 1.09 (0.93, 1.29) | 0.288 | - | |
| Hospital readmission rate, by tertile | ||||
| T1 | Ref | Ref | ||
| T2 | 1.26 (1.11, 1.44) | <0.001 | 1.25 (1.09, 1.43) | 0.001 |
| T3 | 1.59 (1.37, 1.83) | <0.001 | 1.48 (1.27, 1.73) | <0.001 |
Abbreviations: DLD = dyslipidemia; PN = peripheral neuropathy.
Based on multivariable analysis, individuals in ADI4 had 1.40-times greater odds of reamputation within 1 year than those in ADI1 [95% CI (1.10, 1.77)]. Other significant factors associated with 1-year reamputation were black race [versus white race; OR 1.25, 95% CI (1.11, 1.41)], having Medicare [versus private; OR 1.22, 95% CI (1.11, 1.41)] or Medicaid [versus private; OR 1.19, 95% CI (1.00, 1.42)] insurance, being a current smoker [versus nonsmoker; OR 1.37, 95% CI (1.19, 1.58)] or former smoker [versus nonsmoker; OR 1.24, 95% CI (1.08, 1.42)], having CAD [OR 1.23, 95% CI (1.09, 1.40)], PAD [OR 1.56, 95% CI (1.40, 1.75)], CKD [OR 1.14, 95% CI (1.01, 1.29)], and undergoing amputation at a hospital with a high 30-day readmission rate [versus T1 (low); T2, OR 1.25, 95% CI (1.09, 1.43); T3 (high), OR 1.48, 95% CI (1.27, 1.73)].
Discussion
The ADI is a robust and multifaceted measure of geographic socioeconomic deprivation that can provide additional insight into patient socioeconomic status that other singular measures do not capture. It is a known predictor of poor outcomes in a variety of medical and surgical settings.13–16,18 However, its association with postoperative morbidity after LE amputation has not been characterized. In the present study, using longitudinal data from over 7000 patients with diabetes who underwent minor LE amputation in the state of Maryland, we demonstrate that the higher ADI (i.e., more socioeconomic deprivation) is independently associated with increased odds of both 30-day readmission and 1-year reamputation.
To our knowledge, this study is the first to directly assess the impact of socioeconomic deprivation on readmission and reamputation rates in patients with diabetes who underwent minor LE amputation. The only study that we know of to evaluate the impact of the ADI on wound healing in patients with DFU was not significant.19 However, that study focused on the outcome of wound healing in a single-institution cohort that uses a multidisciplinary care model. In contrast, we demonstrated a significant correlation between the ADI quartile and both 30-day readmission and 1-year reamputation after minor LE amputation.
There are a few potential explanations for our findings. First, patients with greater socioeconomic deprivation likely have worse access to care. This can manifest as poor access to follow-up appointments, a lack of social support, and/or lack of community resources.20–22 Our results are consistent with this notion in that insurance status was also significantly associated with readmission and readmission rates. Second, patients with low socioeconomic status may present with more advanced DFU, thus leading to more proximal amputations that are at high risk for readmission. Several studies have demonstrated that patients with diabetes with poor access to care tend to present with more advanced LE disease.23–25 Giacovelli et al. found that insurance status (i.e., Medicaid and uninsured) is a predictor of worse severity of disease in patients presenting for LE revascularization.25 There may also be higher stigma of disease in patients of low socioeconomic status, which results in a hesitancy to receive appropriate preemptive care.26 Finally, patients with a higher ADI may have more underlying comorbidities that could increase their risk of poor perioperative outcomes.27 Although we did not find significant differences in baseline comorbidity profiles across ADI groups in our study, patients with poor access to care often have undiagnosed comorbidities. We found that several comorbid conditions, including CHF, CAD, PAD, CKD, and COPD, impact postoperative outcomes after minor amputation and thus may play a role in the disparity of outcomes that we report.
Our overall 30-day readmission rate of 22.1% is comparable with previously reported readmission rates after minor LE amputations.28–31 For example, Curran et al. reported a 30-day readmission rate of 17% among patients undergoing transmetatarsal resection.28 That rate, which was derived using a nationally representative cohort, is similar to ours, demonstrating that our findings may be generalizable outside the state of Maryland. Our 1-year reamputation rate of 23.6% was also consistent with previous reports.8,31,32 In a systematic review of 435 patients, Borkosky et al. found that the rate of reamputation after partial first ray amputation was 19.8% after a mean follow-up time of 26 months.31 Thorud et al. found that reamputation occurred in 28.4% of patients who underwent transmetatarsal amputation, with most of them occurring within 6 months of the index operation.32 Based on our and other studies, it appears that reamputation will occur in approximately one-fourth of minor amputees. Thus, identifying and mitigating the effects of specific patient-level risks is critical.
Notably, the baseline deprivation of our cohort, as defined by the ADI, is likely greater than that of the national average. Kind et al. initially characterized the ADI as a predictor of 30-day rehospitalization in the Medicare population and found that patients who belonged in the least disadvantaged quartile (corresponding to ADI1 in this study) comprised 85% of their study population.14 This is very different compared with our cohort, in which only 28% of patients resided in an ADI1 zip code. Almost one-third of patients in our study resided in highly disadvantaged neighborhoods (ADI3 or 4), which is likely reflective of the disease we are studying. Diabetic foot amputations are morbid procedures that occur more frequently in patients with significant comorbidities and worse socioeconomic status.33 In addition, our cohort only captured inpatient cases, likely representing a subset of patients with greater complexity of disease who required a higher level of perioperative care.
Given the current trend toward value-based care and capitation payment models, it is essential to identify and prevent risk factors of readmission and reoperation for procedures with high postoperative morbidity, such as diabetic amputations. We have previously demonstrated that treatment in a multidisciplinary care setting is associated with lower rates of admission for DFUs and mitigates the likelihood of amputation for high-risk wounds.33,34 Furthermore, within the same cohort, the ADI was not associated with DFU healing.19 This suggests that utilization of a multidisciplinary model for the treatment of DFU may provide optimal care coordination and better empower patients to handle their postoperative care needs irrespective of socioeconomic status, thus mitigating the effects of socioeconomic deprivation that we observed in our study.
There are a few limitations of our study. The HSCRC is a powerful database that contains detailed information regarding all inpatient and outpatient hospital visits within the state of Maryland. However, it is an administrative database that lacks information regarding clinically relevant factors such as obesity status, disability status, and severity of disease. In particular, we are unable to directly assess the extent and severity of LE disease or status of diabetes management. In addition, because the database only captures hospital cases within the state of Maryland, patients who seek follow-up care outside of the state or at an ambulatory care setting are not accounted for. Certain subgroup analyses in our study may also be somewhat underpowered. For example, the association of worsened health outcomes among uninsured diabetics has been well described35,36; however, we demonstrate nonsignificant results among this subgroup, which only composed 2.93% of our population. Finally, the unique payer system in the state of Maryland may impact our results. Maryland is the only state in the nation to operate under an “all-payer” system, where all patients, regardless of insurance status, are billed an identical amount for the same service. Thus, the generalizability of our results to other states in which reimbursement is dependent on payer status is unclear, although the crude readmission and reamputation rates that we report are aligned with those from national databases.8,28–32
Conclusions
We demonstrate that socioeconomic deprivation, as determined by the ADI, is an independent predictor of 30-day readmission and 1-year reamputation in patients with diabetes who undergo minor LE amputation in Maryland. A targeted multidisciplinary approach addressing the health care needs of individuals from socioeconomic deprived locations may improve perioperative care in this vulnerable population.
Supplementary Material
Disclosure
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Footnotes
Supplementary data
Supplementary data to this article can be found online at https://doi.org/10.1016/j.jss.2020.08.039.
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