Evaluation of the Ventral Hernia Working Group classification for long-term outcome using English Hospital Episode Statistics: a population study

Purpose The Ventral Hernia Working Group (VHWG) classification of ventral/incisional hernia (IH) was developed by expert consensus in 2010. Subsequently, Kanters et al. have demonstrated the validity of a modified version of the system for predicting short-term outcomes. This study aims to evaluate the modified system for predicting hernia recurrence. Methods Patients undergoing IH surgery (defined by OPCS codes) in the England Hospital Episode Statistics (HES) database, from 1997 to 2012, were identified. Baseline demographics at index hernia operation and episodes of further hernia surgery (FHS) were recorded. Risk factors for FHS were identified using cox regression and evaluated against the modified-VHWG grade using receiver-operating characteristics (ROC). Results The final analysis included 214,082 index IH operations. Of these, 52.6% were female and mean age was 56.59 (SD15.9). An admission for FHS was found in 8.3% cases (17,714 patients). Multi-variate cox regression revealed contaminated hernia (p < 0.0001), pre-existing IBD (p < 0.0001) and hernia comorbidity (p = 0.05) to be significantly related to long-term FHS. Classifying patients using these factors, according to the modified-VHWG classification, revealed that compared to Grade 1, the hazard ratio (HR) of FHS increased in Grade 2 (HR 1.19; p < 0.0001) and further increased in Grade 3 (HR 1.79; p < 0.0001). ROC analysis revealed the area under the curve to be 0.73 (95% CI 0.73-0.74). Conclusion This analysis demonstrates the broad validity of the modified-VHWG classification in discriminating risk for FHS. Inclusion of pre-existing IBD as a factor defining Grade 2 patients would be recommended. This analysis is limited by the absence of certain factors within the HES database, such as BMI.