A Retrospective Cohort Study on Using Fully Threaded, Cortical Screws in Locking SIGN Intramedullary Nails

Abstract

The Surgical Implant Generation Network (SIGN) produces solid and straight intramedullary nails used for femoral or tibial fractures. These utilize interlocking screws with proximal and distal threads to purchase at the cortices. When SIGN interlocking screws are unavailable, 4.5 mm, fully threaded, stainless steel, cortical screws are sometimes used to lock the nails. This study compared the alignment, fracture healing, and screw failure rates between cases which solely used SIGN interlocking screws and those which incorporated fully threaded, cortical screws. The SIGN census from January 2018 to August 2021 was reviewed. 79 cases were included in this study. 59 solely used SIGN interlocking screws and 20 incorporated fully threaded, cortical screws. The former group had acceptable alignment in 91.5%, 3-4 bridging cortices by the 12th week in 81.4%, and no screw failure in 96.8%. The latter group had acceptable alignment in 90.0%, 3-4 bridging cortices by the 12th week in 80.0%, and no screw failure in 95.0% of cases. The chi-square test showed no significant difference in outcomes between the two groups with p= .836 for fracture alignment, p= .894 for fracture healing, p= .745 for screw failure. This study concluded that 4.5 mm, fully threaded, stainless steel, cortical screws may be incorporated to lock SIGN nails when SIGN interlocking screws are unavailable.