Does coating an intramedullary nail with polymethylmethacrylate improve mechanical stability at the fracture site?

BACKGROUND

Treatment of tibia diaphyseal fractures with intramedullary nail fixation has proven to be effective. An increasingly popular practice is to coat the nail with bone cement incorporating antibiotics for the purpose of treating and/or preventing infection. To date, the effect of coating on the mechanical performance of the intramedullary nail once implanted is unknown. We hypothesize that cement coating does not change the cross-sectional stiffness of the nail, so that, when fixing tibia diaphyseal fracture with gapping, cement coated intramedullary nail provide stiffness comparable to that of standard conventional uncoated ones.

METHODS

Tests of 4-point bending were conducted to compare the cross-sectional stiffness of uncoated to coated nails. In addition, mechanical tests of compression and torsion on tibia bone phantoms instrumented with coated and uncoated nails were performed, and the proximal-to-distal bone fragment rotations were compared.

FINDINGS

The 4-point bending tests indicated that the cross-sectional stiffness of coated nails was not significantly different from that of the uncoated ones (p-value >0.05). Mechanical tests of compression and torsion corroborated these results by showing no statistical difference in the proximal-to-distal bone rotations attained with uncoated nails when compared to those measured for the coated ones (p-value >0.05).

INTERPRETATION

Cement coating on the nail cannot be relied upon for increased mechanical stiffness of the implant, and should be solely considered as a vehicle for topic delivery of antibiotics.