Online-Only Appendix

Online-Only Appendix

Table A1: Comorbidities and their Definitions in ICD-9-CM Diagnostic Codes

Co-Existing Condition / ICD-9-CM Diagnostic Codes
Ischemic Heart Disease / 410.x, 411.0, 411.1, 411.8x, 412, 413.0, 413.9, 414.x, V45.81, V45.82
Stroke / 430 – 438
Peripheral Neuropathy / 250.6, 355.x, 337.1, 357.2
Peripheral Vascular Disease / 250.7, 443.9
Congestive Heart Failure* / 398.91, 402.01, 402.11, 402.91, 404.01, 404.11, 404.91, 428.0-428.9
Chronic Pulmonary Disease* / 490-492.8, 493.00-493.92, 494-494.1, 495.0-505, 506.4
Renal Failure* / 403.01, 403.11, 403.91, 404.02, 404.03, 404.12, 404.13, 404.92, 404.93, 585, 586, V42.0, V45.1, V56.0-V56.2, V56.8
Cancer* / 200.00-202.38, 202.50-203.01, 203.8-203.81, 238.6, 273.3,V10.71, V10.72, V10.79, 196.0-199.1,140.0-172.9, 174.0-175.9, 179-195.8, V10.00-V10.59, V10.81-V10.9
Other Neurological Disorders* / 330.0-331.9, 332.0, 333.4, 333.5, 334.0-335.9, 340, 341.1- 341.9, 345.00-345.11, 345.2-345.3, 345.40-345.91, 348.1, 348.3-348.39, 780.3, 780.39, 784.3
Deficiency Anemias* / 280.1-281.9, 285.21-285.29, 285.9
Paralysis* / 342.0-342.12, 342.9-344.9, 438.20-438.53
Liver Disease* / 070.22, 070.23, 070.32, 070.33, 070.44, 070.54, 456.0, 456.1,456.20, 456.21, 571.0, 571.2, 571.3, 571.40-571.49, 571.5, 571.6, 571.8, 571.9,572.3, 572.8, V42.7
Coagulopathy* / 286.0-286.9, 287.1, 287.3-287.5, 289.81-289.82

*Diagnostic codes for these conditions were obtained from

Table A2: Hazard Ratios of Mortality for Foot Ulcer and Diabetes Only Patients Compared to Charcot Arthropathy Patients < 65 Years Old*

Adjustment / Full Sample (N = 4,797) / Restricted Sample 1 (N = 1,638)‡ / Restricted Sample 2 (N = 3,159) §
Foot Ulcer / Diabetes Only / Foot Ulcer / Diabetes Only / Foot Ulcer / Diabetes Only
Unadjusted / 1.214 (0.996 –1.478) / 0.462 (0.371–0.576) / 1.474 (0.994–2.187) / 0.671 (0.439 – 1.025) / 1.132 (0.901– 1.422) / 0.395 (0.305 –0.512)
Adjusted† / 1.169 (0.957–1.429) / 0.595 (0.474– 0.747) / 1.228 (0.816–1.849) / 0.702 (0.457–1.079) / 1.200 (0.951–1.515) / 0.570 (0.433 –0.749)

* Due to the small number of Charcot arthropathy patients < 65 years in age and their considerably lower mortality rates (19.1%) than the overall sample (28.3%), we drew a larger sample using 1-to-4 matching. If a matched stratum contains anyone 65 or older, we dropped that stratum from analysis.

†Adjusted formatched factors (age, sex, race, marital status, and diabetes duration) and co-morbidities (ischemic heart disease, stroke, peripheral vascular disease, congestive heart failure, chronic lung disease, paralysis, other neurological disorders, liver disease, renal failure, cancer, deficiency anemias, and coagulopathy).

‡Restricted sample 1 includes in the Charcot arthropathy group only patients who have not had foot ulcer in 2002 – 2007 and their matched controls (N = 1,638).

§ Restricted sample 2 includes in the Charcot arthropathy group those who experienced foot ulcer in 2002 – 2007 and their matched controls (N = 3,159).

Table A3: Adjusted Hazard Ratios (HR) from the Full Cox Proportional Hazards Regression Model Estimated with Neuropathic Foot Ulcer Patients and their Matches (N = 4,318)*

Variables / HR / 95% CI† / P-Value
Comparison Group [Charcot arthropathy]‡
Foot Ulcer / 1.232 / (1.062 - / 1.429) / 0.006
Diabetes Alone / 0.755 / (0.641 - / 0.889) / 0.001
Age in years / 1.039 / (1.032 - / 1.046) / < 0.001
Race [Non-Hispanic White]
Non-Hispanic Black / 0.976 / (0.806 - / 1.183) / 0.806
Hispanic / 0.881 / (0.581 - / 1.336) / 0.550
Other / 0.693 / (0.537 - / 0.895) / 0.005
Male [Female] / 1.620 / (0.968 - / 2.709) / 0.066
Married [Not married] / 0.773 / (0.687 - / 0.870) / < 0.001
Diabetes ≥6 years / 1.046 / (0.929 - / 1.178) / 0.455
Ischemic Heart Disease / 1.228 / (1.083 - / 1.393) / 0.001
Stroke / 1.171 / (0.989 - / 1.386) / 0.067
Peripheral Vascular Disease / 1.311 / (1.149 - / 1.495) / < 0.001
Congestive Heart Failure / 1.939 / (1.670 - / 2.250) / < 0.001
Chronic Pulmonary Disease / 1.234 / (1.056 - / 1.441) / 0.008
Renal Failure / 1.915 / (1.639 - / 2.238) / < 0.001
Cancer / 1.557 / (1.258 - / 1.926) / < 0.001
Other Neurological Disorders / 1.617 / (1.237 - / 2.112) / < 0.001
Deficiency Anemias / 1.292 / (1.106 - / 1.509) / 0.001
Paralysis / 1.481 / (1.038 - / 2.112) / 0.030
Liver Disease / 2.074 / (1.540 - / 2.792) / < 0.001
Coagulopathy / 1.568 / (1.145 - / 2.148) / 0.005

* There were 949 patients in the Charcot arthropathy group, 1,471 patients in the foot ulcer group, and 1,898 patients in the diabetes only group. All were neuropathic except for 840 patients (44.2%) in the diabetes alone group.

† Confidence Interval

‡ Reference categories are in brackets.