Proper mesh size is important in preventing recurrence. Intra-operative observations in recurrent hernia cases have revealed that the mesh slipped away from its medial fixation
. This happens more commonly where a mesh is too large or too small: a large mesh can wrinkle, slipping from where it is anchored; shrinkage of a mesh that is too small can result in its being released from its points of fixation due to tension
Manufacturers worldwide produce meshes in a wide range of sizes and of styles. The availability of a range of products may be desirable and may provide some benefit where it is supportable. However, day-to-day budgeting realities in many contexts, especially in public hospitals in developing countries, mean that hospital purchasers must identify an affordable single product or limited range of products for use for all cases.
In terms of mesh length, the size determined by this study is 6% shorter than the 15.0 cm mesh recommended for use in the Lichtenstein technique. However, the 8.5 cm mesh width determined by this study is 21% wider than the recommended 7.0 cm. That the recommended mesh size may be too narrow in a proportion of the patient population is worrying as this has potential clinical implications: where the mesh is too narrow, in these patients it will not be possible to provide the size of overlap that is recommended to prevent recurrence.
These calculations have used the higher of the 95% confidence intervals to offer some degree of certainty that the true mean has been taken into account. Consideration of the full range of observed measurements further highlights that while the recommended length is appropriate, the recommended mesh width is a cause for concern in some cases. Addition of an 8.0 cm overlap allowance to the highest observed transverse arch aponeurosis measurement in this study results in a highest recommended mesh length of 15.2 cm, which is in line with the 15.0 cm recommendation. However, addition of a 4.0 cm overlap allowance to the observed 6.5 cm width suggests that in some cases a mesh as wide as 10.5 cm may be needed, 50% wider than the recommended mesh size.
A prospective trial would be needed to determine what patient benefit, if any, would result from the adoption of 8.5cm x 14cm as the standard flat mesh size. However, it may be unlikely that such a trial will be conducted, since manufacturers are not required to produce such evidence. In addition, since the provision of a single flat mesh size for all patients is most likely to be the norm in low-resource settings, it is unlikely that a publicly funded trial is possible. Nevertheless, our findings may be of interest to manufacturers in determining the standard size of meshes they produce and to those who make surgical supply purchasing decisions.
This study is rare in its use of direct in vivo measurements of the inguinal floor to determine an optimal dimension for mesh implants. The study also has limitations that must be acknowledged. It is a small sample, but the confidence intervals generated are relatively narrow, indicating consistency in measurements. The population considered is South East Asian (Filipino nationals of varying ethnic origin) and it is uncertain whether there may be regional variations in anatomical measurements that should be considered. That said, previous research has found no significant correlation between inguinal canal measurements and patients’ weight, height and body mass index
. Only a small proportion of patients included had direct inguinal hernias. Further studies in larger samples of different ethnic origin are recommended, as are studies in patients with direct and indirect inguinal hernia in order to determine whether different optimal mesh sizes exist for the two indications.