Impact of Different Methods of Measuring Abdominal Wall Hernia Defect Size On Mesh Selection

Deepa V Cherla, MD, BS, Julie L Holihan, MD, MS, BS, Lillian S Kao, MD, MS, BS, Tien C Ko, MD, BS, Mike K Liang, MD, MS, BA. The University of Texas Health Science Center at Houston

INTRODUCTION: Hernia defect size affects surgical technique, the size of mesh selected, and outcomes. Despite the importance of defect size, there is no standardized measurement technique, and little literature exists that assesses different methods of determining hernia area. Current strategies to measure defects include radiographic (CT) and intraoperative (with abdomen desufflated or insufflated, from the intra-abdominal or extra-abdominal aspects). Our aims were to determine 1) if any significant differences existed between different methods of measuring hernias and 2) the effect of these alternate methods of measurement on mesh size selection.

METHODS AND PROCEDURES: A prospective study of all patients enrolled in a randomized trial assessing laparoscopic ventral hernia repair at a single institution from 3/2015 to 7/2016 were eligible for inclusion. Abdominal wall hernia defect size was determined by multiplying defect length and width obtained separately using each of 4 methods: radiographic (CT), intraoperative with abdomen desufflated, intraoperative with abdomen insufflated (intra-abdominal aspect), and intraoperative with abdomen insufflated (extra-abdominal aspect). All measurements were determined by 2 faculty surgeons. Mesh size for each measurement was calculated based on the smallest mesh needed to achieve at least 5 cm of mesh overlap in all directions utilizing the following mesh size categories: 10×15 cm, 15×20 cm, 20×30 cm, and 25×30 cm. Two-way mixed-effect model was used to calculate the intraclass correlation between the 4 methods of measurement.

RESULTS: Fifty-two patients met the inclusion criteria for assessment and the median (range) hernia defect areas measured by the 4 techniques were radiographic (CT) 19.9 (9.8-39.6) cm², intraoperative with abdomen desufflated 19.6 (11.3-43.5) cm², intraoperative with abdomen insufflated from the intra-abdominal aspect 20.0 (12.0-49.0) cm², and intraoperative with abdomen insufflated from the extra-abdominal aspect 26.0 (14.0-56.0) cm². The 4 different measurement methods had an intraclass correlation of 0.702 (0.581-0.806). Different measurements affected mesh selection in 28.9% of cases (Table 1).

CONCLUSION(S): The 4 methods of measuring abdominal wall hernia defect sizes are imperfectly correlated. Due to the impact of these differences in measurement on selected mesh size, additional studies are needed to determine which method results in optimally-sized abdominal wall prostheses and superior hernia repair. Further investigation is needed to identify a standardized method of assessing hernia size and to correlate the ratio of mesh size to hernia size and clinical outcomes.