Standardizing the evaluation of scientific and academic performance in neurosurgery--critical review of the "h" index and its variants.

Assessing the academic impact and output of scientists and physicians is essential to the academic promotion process and has largely depended on peer review. The inherent subjectivity of peer review, however, has led to an interest to incorporate objective measures into more established methods of academic assessment and promotion. Journal impact factor has been used to add objectivity to the process but this index alone does not capture all aspects of academic impact and achievement. The "h" index and its variants have been designed to compensate for these shortcomings, and have been successfully used in the fields of physics, mathematics, and biology, and more recently in medicine. Leaders in academic neurosurgery should be aware of the advantages offered by each of these indices, as well as of their individual shortcomings, to be able to efficiently use them to refine the peer-review process. This review critically analyzes indices that are currently available to evaluate the academic impact of scientists and physicians. These indices include the total citation count, the total number of papers, the impact factor, as well as the "h" index with eight of its most common variants. The analysis focuses on their use in the field of academic neurosurgery, and discusses means to implement them in current review processes.