Prediction of Wound Radius Reductions and Healing Times in Neuropathic Diabetic Foot Ulcers

Defining reliable predictors for wound healing in diabetic foot ulcers is an important issue. Usually, the percentage of wounds healed within a defined time period is used for this purpose, but this approach does not predict the time needed for healing in individual patients (1). We have recently established an equation to estimate the healing time in diabetic neuropathic foot ulcers (2).

This prospective study aimed to verify this approach by evaluating wound healing in 41 consecutive type 1 or type 2 diabetic patients (29 men, 12 women, aged 61.3 ± 11.1 years) with neuropathic but not angiopathic plantar foot ulcers (3). All patients received identical standard ulcer wound care, including use of proper footwear, non-weight-bearing limb support by half-shoes, debridement, daily careful monitoring of the ulcer, and antibiotic treatment when necessary. All patients were on insulin therapy. Ulcer healing was assessed by planimetric measurement of the wound area (in mm²) after thorough wound debridement. Ulcer depth was assessed semiquantitatively using the Wagner grading system, with 13 ulcers grade 1 and 28 ulcers grade 2. The mean wound radius (R) was calculated from the mean wound area (A, in mm²) by the equation R =

(2). The time course of wound healing was determined by plotting the mean wound radius derived from the measurements every fortnight against the time. The slope of the regression curve is interpreted as the weekly reduction of the mean wound radius. To predict the healing times, the wound area at beginning was transformed into the wound radius using the described formula and divided by the value of the wound radius reduction (0.45 mm/week) derived from our previous study (2).

The initial average wound area was 96.9 ± 13.1 mm², as compared with 3.61 ± 1.6 mm² after 10 weeks. The observed weekly wound radius reduction was 0.39 mm (95% CI 0.32–0.48) with an observed average healing time of 75.9 (95% CI 71–81) days, which was slightly less than the predicted healing time of 86.9 (95% CI 73–101) days. The observed and predicted healing times were significantly correlated with each other (r = 0.55, P = 0.0002). Both the wound area and the wound radius at study entry were significantly correlated with the healing times (area: r = 0.94, P = 0.005; radius: r = 0.99, P = 0.0001). The wound area reduction follows a second degree exponential function, with most of the wound area reduction taking place within the first weeks of treatment.

The results of this study confirm that the healing time in neuropathic foot ulcers can reliably be predicted by using the equation R =

/0.45. Such calculations may be regarded as a useful tool in daily clinical practice, both to give an estimation of the time period needed for healing, and to recognize early those ulcers that do not respond adequately to the treatment.