Development and validation of a prognostic model for stump healing in major lower limb amputation
Ashraff, S. (2016) Development and validation of a prognostic model for stump healing in major lower limb amputation, no. 319.
Introduction Stump healing is essential in patients with a lower limb amputation in order for them to mobilize again. Little research has been being done on factors affecting stump healing. The aim of this paper is to explore the effect of haematological makers as well as patient characteristics on stump healing after patients have undergone an amputation procedure. In addition, a practical model regarding factors that affect stump healing was developed. Methods Patients who underwent a major lower limb amputation (above knee and below knee) at the Royal Infirmary of Edinburgh from the period of 2006 to 2009 were included in this study. A prognostic model utilizing backward stepwise logistical regression was developed to measure the probability of lower limb stump healing. The relationship between the dependent and independent variables was identified using univariate and multivariate logistic regression. Hosmer and Lemeshow goodness of fit test and Receiver Operating Curve (ROC) was used in order to measure the effectiveness of the model. The model was validated with the prospective data of 100 patients that had undergone major lower limb amputation from the year 2010 and 2011 in Royal Infirmary of Edinburgh prospectively. Results In this study healing of the stump as defined was achieved in sixty three percent (63%) of patients. Univariate analysis found seven variables to be associated with lower limb stump healing (type of amputation, gender, hypertension, smoking, serum sodium, serum creatinine and serum High Density Lipid cholesterol (HDL)). A further four variables (age, diabetes xxv mellitus, white cell count and Prothrombin Time) were added to the model secondary to their strong clinical association with the stump healing. Three variables, namely serum sodium, serum creatinine and serum High Density Lipid cholesterol were identified which influenced stump healing. Patients with normal serum sodium were 75% more likely to have lower limb stump healing compared to that of patients with abnormal serum sodium (odds ratio [OR] 1.756; 95% confidence interval [CI] 1.048-2.942). Patients with normal serum creatinine were 66% more likely to have their stump healed (OR 1.664; 95% CI 0.94 to 2.946). The healing rate of patients with a normal level of serum High Density Lipid cholesterol was 75%, in contrast to patients with an aberrant level of serum High Density Lipids cholesterol (OR 1.753; 95% CI 1.061 to 2.895). The effectiveness of the retrospective stump-healing model was demonstrated by the area under the Receiver Operator Curve (0.612), which was supported by the Hosmer and Lemeshow goodness-of-fit test (p=0.879). In the prospective study, the model's discriminatory power was verified by the area under the Receiver Operator Curve (0.584) and Hosmer and Lemeshow goodness-of-fit test (p>0.05). Conclusion Serum sodium, serum High Density Lipid cholesterol and serum creatinine have a strong correlation with lower limb stump healing. However, serum sodium and serum High Density Lipid cholesterol secondary to multiple co-morbidities in this cohort group could be altered secondary to disease pathology itself. Further clinical research is necessary to evaluate the association of the risk factors with lower limb stump healing.