Failure of Locked Design-Specific Plate Fixation of the Pubic Symphysis

Abstract

Physiological pelvic motion has been known to lead to eventual loosening of screws, screw breakage, and plate breakage in conventional plate fixation of the disrupted pubic symphysis. Locked plating has been shown to have advantages for fracture fixation, especially in osteoporotic bone. Although design-specific locked symphyseal plates are now available, to our knowledge, their clinical use has not been evaluated and there exists a general concern that common modes of failure of the locked plate construct (such as pullout of the entire plate and screws) could result in complete and abrupt loss of fixation. The purpose of this study was to describe fixation failure of this implant in the acute clinical setting. Retrospective analysis of multicenter case series. Multiple trauma centers. Six cases with failed fixation, all stainless steel locked symphyseal plates and screws manufactured by Synthes (Paoli, PA) and specifically designed for the pubic symphysis, were obtained from requests for information sent to orthopaedic surgeons at 10 trauma centers. A four-hole plate with all screws locked was used in 5 cases. A six-hole plate with 4 screws locked (two in each pubic body) was used in one. Fixation for disruption of the pubic symphysis using an implant specifically designed for this purpose. Radiographic appearance of implant failure. Magnitude of failure ranged from implant loosening (3 cases), resulting in 10-mm to 12-mm gapping of the symphyseal reduction, to early failure (range, 1-12 weeks), resulting in complete loss of reduction (3 cases). Failure mechanism included construct pullout, breakage of screws at the screw/plate interface, and loosening of the locked screws from the plate and/or bone. Backing out of the locking screws resulting from inaccurate insertion technique was also observed. Failure mechanisms of locked design-specific plate fixation of the pubic symphysis include those seen with conventional uniplanar fixation as well as those common to locked plate technology. Specific indications for the use of these implants remain to be determined. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.