Based on my thinking and study, I do not believe that this verse is referring to Old Testament saints and do not believe that what is being described here is "resurrection" (a la Christ). My reasons are:
1) 1 Corinthians 15:23 gives a clear order to resurrections, and Christ is first. Second is those who are his AT HIS COMING. As such this cannot be a "resurrection".
2) The Greek here does not really demand such an interpretation. In fact, the verses strongly imply that those raised came out of graves opened by the "crucifixion earthquake" which struck the Jerusalem environs as described in v52.
What I am thinking with regards to this passage is that what occured was the raising of many disciples (by the time Matthew wrote his Gospel disciples of Christ were referred to as "saints") who had passed away during Christ's ministry but whose bodies were not yet fully decomposed. They were raised in the same manner as Lazarus and Dorcas (body and spirit rejoined but body not made incorruptible) and hence were not Resurrected in the sense of having their incorruptible bodies. Admittedly it is speculation but it is definitely permissable within the text and harmonizes properly with the other Scriptural data on the Resurrection.