In vitro and in vivo radiomorphometric analyses of distal screw hole position of the solid tibial nail following insertion

Objective. The objective of this study was to analyse the position of the distal interlocking holes of an unreamed solid tibial nail relative to the adjacent cortices of the tibial bone. Design. In vitro and in vivo radiographic-morphometric analysis. Background. To date, ‘radiation-independent’ intramedullary distal interlocking aiming systems have not been successful, primarily because proximally mounted aiming devices cannot account for the deformation of the nail during insertion; therefore the distal interlocking holes relative to the adjacent cortices must be understood. Methods. A two-dimensional radiographic-morphometric analysis was performed in 40 tibiae after in vitro (n = 20) and in vivo (n = 20) implantation of unslotted stainless steel unreamed 8- and 9-mm diameter intramedullary nails. Results. The combined in vitro and in vivo results showed average distances between the upper distal transverse hole and the anterior aspect of the tibia of 12.3 mm (image 1.7 mm; variance 2.9 mm2; range 7.6 mm). Conclusions. The distances between the upper distal transverse hole and the anterior aspect of the tibia are the most reliable parameters of distal nail hole position.