Reversed Z-effect and Z-effect phenomena in femoral neck fracture treated with a dynamic locking plate fixation: Case report.

The aim of this case report is to present an unusual mechanism of failure of a dynamic locking plate (DLP), previously reported in dual lag screw proximal femoral nails. A 78-year-old female patient experienced a displaced right femoral neck fracture (FNF) which was managed with DLP. At the postoperative sixth-week appointment, her hip radiographs showed that two of three telescoping screws had slid within the telescrew barrel, and one screw was fully extended and cutting through the femoral head. At the third-month checkup, radiographs revealed an unhealed FNF and 12 mm sliding on all three telescoping screws. At the final 11th-month follow-up, two screws were completely collapsed and the previously nonpenetrating screw was partially extended and cutting through the femoral head. Femoral neck shortening and femoral neck nonunion were noticed as well. In conclusion, the postoperative course of the case supports the hypothesis of a specific pattern of DLP failure resembling reversed Z- and Z-effects found in dual lag screw proximal femoral nails.