Foot radiography and serum markers to assess foot impairment risk across CKD-MBD stages

Poster Title: Using foot radiography and serum markers to assess foot impairment risk across CKD-MBD stages

Student: Tyler George Class of 2024

Faculty Mentor and Department: Michael Jones, DPM; Department of Orthopaedic Surgery – Podiatry Services

Funding Source: National Institute of Diabetes and Digestive and Kidney Diseases, T35 Training Grant DK007400

ABSTRACT

Background: Approximately 34.2 million Americans live with diabetes, which is the leading cause of end-stage renal disease (ESRD), and patients with ESRD from diabetes have the highest rates of non-traumatic lower extremity amputation (LEA). While bone disorders are well established in ESRD, it is less clear how earlier stages of chronic kidney disease (CKD) impact bone health. Chronic kidney disease – mineral bone disorders (CKD-MBD) is a syndrome describing the effect of kidney disease on bone health. CKD-MBD is defined by laboratory abnormalities (in calcium, phosphorus, parathyroid hormone (PTH), and vitamin D metabolism, as well as bone disease and calcification of vascular/soft tissue.

Hypothesis: We hypothesize that progression from early to late stages of CKD-MBD will reflect similar impairments in pedal buckling ratio, prior amputation, and vessel calcification as seen on radiography and in serum biomarkers.

Methods: This retrospective chart review assessed patients with diabetes mellitus, CKD-MBD, and at least one foot radiograph treated at Wake Forest University Baptist Hospital from 2012 to 2021. Patient demographics, serum biomarkers (e.g. calcium), and pedal radiograph measurements were extracted from the patient chart. Buckling ratio, an estimate of fracture risk, was calculated using diameter measurements of the 2nd and 5th metatarsal as seen on radiograph. Radiograph also allowed for pedal vessel calcification identification.

Results: A total of 152 patients were assessed with at least 25 patients in each stage of CKD-MBD. In higher stages of CKD-MBD there were increased odds of vessel calcification (Adjusted OR: 2.3 (95% CI: 1.7, 3.0), p < 0.001), increased odds of foot amputation (Adjusted OR: 2.3 (95% CI: 1.6, 4.5), p < 0.001), and increases in 2nd metatarsal buckling ratio (Adjusted OR: 2.1 (95% CI: 1.1, 3.2), p < 0.001) and 5th metatarsal buckling ratio (Adjusted OR: 1.1 (95% CI:1.0, 1.2)), even after controlling for age, gender, and BMI. Serum calcium levels were inversely related to buckling ratios of the 2nd (Adjusted OR: -1.9 (95% CI: -3.1,- 0.6), p = 0.004) and 5th metatarsal (Adjusted OR: -1.7 (95% CI: -2.9,- 0.4), p = 0.010,), after controlling for age, gender, and BMI.

Conclusions: Worsened CKD-MBD stage was associated with greater odds of radiographic evidence of pedal calcification and increased buckling ratio of the 2nd and 5th metatarsal, as well as increased risk of amputation. Lower serum calcium was associated with higher fracture risk. Earlier identification of low serum calcium and radiographic pedal disease in patients with CKD-MBD may help identify those at greater risk of vessel calcification, amputation, and fracture. In aggregate these findings suggest possible use of radiography and serum markers as a screening tool for poor outcomes in this population. Further analysis should assess the effects of other common serum metabolites on pedal bone health. 

Source of mentor’s funding or other support that funded this research: none