The Author Replies
The relatively low recurrence rate (4%) reported in our study can be attributed to 3 main reasons: the technique of injection we followed to ensure complete filling of the entire sinus cavity with thrombin gelatin matrix (TGM), the meticulous curettage of the sinus cavity to create a raw bleeding surface that allows TGM to activate the hemostatic cascade, and form an insoluble fibrin clot that fills the dead space. Subsequently, this fibrin clot gets organized forming a fibrous plug, obliterating the sinus cavity and preventing any future hair entrapment and thus recurrence of PSD. Also, we evaluated a different sealant than the previous trials of fibrin glue, which may explain the better outcome. It is important to remember that the recurrence rate in our study reflects the short-term follow-up (median, 24 months) and not the definite recurrence rate, because PSD is known to recur many years, up to 20 years, after surgical treatment.3
In their systematic review, Kayaalp et al4 reported an 80% success rate of the use of fibrin sealant for PSD, which increased to 85% after adding the results of our study. Viewing the heterogeneity test of their meta-analysis, we found that the high level of inconsistency (I2), more than 67%, and the significant (p = 0.015) degree of heterogeneity among the studies analyzed made the calculation of a weighted mean success rate unreliable statistically, even with the use of the random-effects model. Moreover, because we used TGM, a different material than the fibrin glue used in the other 4 trials, we do not think that combining the results of 2 different sealants in a quantitative manner is appropriate.
Finally, the authors advise that sealants, in general, should not be used for the treatment of PSD on the basis of their cost and success rates that are not greater than other cost-effective, minimally invasive methods such as phenol injection. The injection of phenol 80%, albeit cheaper than fibrin glue and TGM, has some shortcomings that include its corrosive nature, which may warrant protection of the surrounding skin, and the intense inflammatory reaction induced by phenol that destroys the epithelial lining of the sinus, yet could be quite painful and require hospitalization of the patient overnight.5,6
However, fibrin glue and TGM are considered safer to use, and less painful, allowing discharge of the patient within a few hours after the injection. Furthermore, the success rates of phenol injection range between 60% and 95%6; this implies that the recurrence of PSD after phenol injection can be as high as 40%, higher than the highest reported incidence of recurrence after the use of sealants. To elucidate the cost-effectiveness of each entity, well-powered randomized trials comparing TGM with either conventional surgery (eg, off-midline closure) or phenol 80% injection are required to reach solid conclusions about its clinical efficacy and safety.