Pegging Porous Polyethylene Implants

I have a number of concerns with a recent ARCHIVES article by Rubin et al.¹ I would like to boldasize that their technique is for the flat-surfaced, conical, porous polyethylene-type implant and is based on the observation that "the flattened anterior surface of the conical orbital implant does not move significantly from the intraoperative to the final postoperative position." This technique may not necessarily be successful with a spherical implant. The authors acknowledge that "similar stability may occur with placement of spherical implants, but that would be more difficult to assess clinically." Furthermore, they point out, "with secondary placement of a motility post on spherical surfaces, the desired centration has been difficult to achieve." It is important for the reader to appreciate this distinction. If this technique is applied to a spherical porous polyethylene implant, I suspect that decentration or misdirection of the peg (so that the peg is on an angle) will commonly occur. A peg that is decentrated or ends up on an angle may lead to difficulty creating a good coupling between the peg and posterior surface of the prosthesis, which subsequently leads to poor motility, discomfort, and a possible clicking sound as the peg moves in and out of the couple with the prosthesis.²