If the title of Rajiv Joseph’s new play Gruesome Playground Injuries isn’t off-putting enough, what transpires onstage certainly is. This dark comedy about two friends who compare the all-too-visible scars from various physical traumas over the course of many years might have worked as an outrageous one-act. But drawn out to a full-length evening it becomes the theatrical equivalent of rubbernecking at a highway car crash.

The playwright--whose Pulitzer-Prize nominated Bengal Tiger at the Baghdad Zoo, soon to arrive on Broadway, is apparently far more substantial—does display a facility for dark humor in this two-character work about  Kayleen (Jennifer Carpenter) and Doug (Pablo Schreiber), who first meet in their parochial school infirmary. The ensuing vignettes depict their equally ill-fated encounters over the ensuing years, in which the clearly foolhardy Doug has, among other things, blown out one of his eyes with a firecracker and been hit by lightning, while the troubled Kaylee has developed a propensity for self-mutilation.

With little besides the results of these horrific incidents on display, the characters emerge as little more than cipher-like devices fueling the evening’s nasty humor. The detached, clinical nature of the proceedings is further accentuated by Neil Patel’s antiseptic set design--resembling a hospital room and including several rows of audience members onstage as if observers at an operating theater--and by the decision to have the actors doing their costume and make-up changes in full view.      

The performers do what they can with their schematic roles, with Carpenter, in particular, displaying the sort of edge charisma edginess that she uses to such fine effect on TV’s Dexter. But their efforts are not enough to overcome this deliberately provocative but ultimately shallow exercise.

Second Stage Theatre, 305 W. 43rd St. 212-246-4422. www.2st.com.