Trust But Verify: Design Differences in The Prevention of Targeting Errors in Cephalomedullary Nails

Abstract

Objectives: To evaluate insertional damage on explanted cephalomedullary nails and to differentiate typical from atypical wear to characterize outliers. Design: Therapeutic. Setting: Level II trauma center. Participants: Patients who underwent removal of an implanted cephalomedullary nail for any reason from 2015 to 2023. Methods: Inspection of implants was performed at ×1000 magnification with a light microscope. Benchtop testing was performed with Gamma3, Gamma4, Intertan, TFN, and TFNa instrumentation. Results: One hundred nine cephalomedullary nails were inspected. Insertional damage was observed in more than 95% of the implants recovered. In 34% (37 of 109) of implants, damage to the proximal aperture was severe enough to cause a chamfer or “notch.” Chamfers were also encountered along the distal locking aperture in short stem implants in 44% (19 of 43). Guidewire chamfers to the proximal implant external to the aperture and damage to preinserted set screws were outliers. Evidence of set screw fracture or deformity was encountered in 12 specimens. Four anomalous set screw variants were encountered within 1 implant design, each variant exhibiting maltracking with deployment that could result in malfunction. Conclusions: Insertional damage to cephalomedullary implants was encountered routinely among the explants and should not always be categorized as preventable surgical error. Surgeons should be familiar with technical and design factors that contribute to chamfering of implants to reduce failures. Level of Evidence: Therapeutic, Level III