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THE FIBULAR INTRAMEDULLARY NAIL VERSUS LOCKING PLATE AND LAG SCREW FIXATION IN THE MANAGEMENT OF UNSTABLE ELDERLY ANKLE FRACTURES: A CADAVERIC BIOMECHANICAL COMPARISON.

OBJECTIVES
To compare the biomechanical failure properties of the fibular intramedullary nail with locking plate and lag screw fixation in the management of unstable elderly distal fibular fractures.


METHODS
Twelve fresh-frozen cadaveric lower limbs (six matched-pairs) were studied. A simulated OTA/AO 44-B fracture was created, then randomly allocated within each pair to intramedullary nail or locking plate fixation supplemented with an interfragmentary lag screw. The limbs were secured with the foot rigidly held in 20 of supination, loaded to 700N and subjected to progressive external rotation until failure.


RESULTS
The mean specimen age was 86.5 years (61-97). Mean torque to failure was greater in the intramedullary nail group but did not reach statistical significance (23.5 Nm vs. 21.6 Nm; p=0.463). The nail failed at a significantly greater angle of rotation compared with plate fixation (66.5 vs. 53.3; p=0.046). There was no significant difference between the groups with respect to construct stiffness (p=0.673) or energy absorbed (p=0.075). The locking plate specimens failed through plate and screw construct pull off at the implant-bone interface. In contrast, the intramedullary nail specimens failed at the lateral ligament complex, whilst the fracture-implant construct remained intact.


CONCLUSION
Intramedullary nailing and locking plate fixation have similar biomechanical characteristics when tested to failure. The benefits of the minimally invasive surgery offered by the intramedullary nail make it an attractive implant in the management of these patients.


LEVEL OF EVIDENCE
V - Cadaveric study.