The locked intramedullary fibula nail: a biomechanical cadaveric evaluation

G. Smith, R. Wallace, G. Findlater, T. White

Introduction: Locked intramedullary nail fixation of fibula fractures has many attractive qualities. Not only is it a minimally invasive procedure but, as a consequence of its location, there is little prominent metalwork.

Hypothesis: To date there are no biomechanical studies assessing the strength of fixation in a rotational torque where previous generations of smooth, unlocked intramedullary devices have failed. Prior to recommending this treatment modality we aimed to assess whether there is a biomechanical advantage to fixing the most common unstable ankle fracture - the OTA 44-B2 - with an intramedullary device in a cadaveric model.

Methods: Twenty cadaveric lower limbs (ten cadavers) had an OTA 44-B2 type injury created surgically with a fibula osteotomy and appropriate soft tissue release. The deep deltoid was preserved to represent fixation of the medial side. One leg was randomly allocated to fixation with a locked intramedullary fibula nail and the other a lag screw (3.5mm) and neutralisation plate (one-third tubular). A tensile tester subjected all samples to an axially loaded (800Nm) supination external rotation force (30degs/s) to failure (point of sudden downturn in torque).

Results: Superior ultimate tensile strength and energy absorption were seen in the nail group (Students't-test, p=0.03 and 0.07 respectively). This equated to a mean improvement in biomechanical properties of approximately 20%.

Conclusion: Enhanced biomechanical attributes are of particular advantage when managing osteoporotic ankle fractures. The results of this study complement the growing body of research recommending the fibula nail.