Evaluating a scientific paper often starts with an assessment of the manuscript’s technical construction and the project design; these elements often characterize the reader’s “first impression.” From this perspective, the article by McKeon et al. makes a good first impression. In this cadaver dissection study, stability of the thumb metacarpophalangeal joint is assessed after progressive release of the proper and accessory collateral ligaments. The authors identify radiographic parameters that correlate with metacarpophalangeal joint instability, noting in particular that radial translation of the proximal phalanx relative to the thumb metacarpal head correlates with disruption of both collateral ligament structures.

     This paper is easy to read, and the technical details of the experimental environment and anatomic dissection are detailed and clear. The radiographic reproductions, which are especially critical to the presentation of the data, are well prepared and simple to understand. The authors wrote a good Discussion section in which they properly frame the practical considerations related to a reliable radiographic finding that correlates with complete ulnar collateral ligament disruption. Furthermore, this project is important because ulnar collateral ligament injuries of the thumb are very common and general orthopaedic surgeons as well as hand surgeons will continue to see these injuries at the time of first presentation.

     Beyond a first impression, however, are other considerations that enhance this project’s value. An accurate and prompt evaluation of thumb ulnar collateral ligament injury is important because many of these injuries represent structural damage to the ligament complex that is best treated with surgery. Missing a completely unstable injury can lead to an instability arthritis pattern that might have been otherwise prevented. Traditional assessment of thumb ulnar collateral ligament injury has relied primarily on stress testing of the thumb in both extension and flexion and comparing the findings with those of a comparison examination of the uninjured side1. The presence of valgus laxity of the thumb with the metacarpophalangeal joint positioned in flexion alone correlates with damage to the proper collateral ligament2. Valgus laxity that is present with the thumb in both extension and flexion correlates with loss of integrity of both the accessory and the proper collateral ligament and more likely is associated with proximal entrapment of the ligament behind the adductor aponeurosis as described by Stener3.