SLR - February 2018 - Pegah Samouhi

Biomechanical Comparison of Intramedullary Fibular Nail Versus Plate and Screw Fixation

Reference: George Smith, Samual Peter Mackenzie, Robert James Wallace, Timothy Oliver White. Biomechanical Comparison of Intramedullary Fibular Nail Versus Plate and Screw Fixation. Foot and Ankle International. 2017, Vol 38(12)1394–1399.

Scientific Literature Review

Reviewed By: Pegah Samouhi, DPM
Residency Program: Cedars Sinai Medical Center, Los Angeles, CA

Podiatric Relevance: Podiatric physicians are faced with treating patients with comorbidities, including diabetes, hypertension, rheumatoid arthritis and vascular insufficiencies, which negatively affect the quality of skin and compromise tissue healing. Recent clinical studies have demonstrated that fibular intramedullary nail fixation results in fewer wound complications and infections. However, there has not been biomechanical evidence comparing the strength of intramedullary fixation and the standard care (ORIF) of plate and screw fixation.

Methods: Twenty cadaveric limbs (10 cadavers) with surgically created SER IV injury patterns were treated with intramedullary nail on one leg, and the other leg was fixated with plate and screw fixation. Ankle fracture was created by releasing the AiTFL, PiTFL, transverse ligament and osteotomy of distal fibula at a 45-degree angle. Medial malleolus was left intact and deltoid left intact to simulate a successful medial malleolar fixation. All specimens had one ankle randomly allocated to the nail group (Acumed) and the other to the standard ankle fixation with 1/3 tubular plate and screws. Testing apparatus was used to determine the force to failure with axial loading and supination and external rotation. The failure point was taken when the recorded torque demonstrated a sudden drop. Specimens were then visually inspected to describe the mode of failure.   

Results: The fibular nail was found to be superior (P = .028) to a standard lag screw and neutralization plate in torque to failure testing. No significant difference could be detected in energy absorbed (P = .09) or angle at failure (P = .88) between the two groups. All 10 of the standard plate group failed at the bone-metal interface; that is, the screw/plate construct was pulled off the bone. No nailed fibula construct failed; in the nailed group, eight ankles failed by rupture of the lateral ligament complex, one by avulsion of the lateral ligament of fibula and one by a subtalar dislocation. No specimen had a medial-sided injury on inspection.

Conclusion: The biomechanics of the fibular nail represents a substantial departure from orthodox AO teaching regarding ankle fracture fixation, with two significant elements. The first is the fact that the technique is a percutaneous, fluoroscopic reduction of the mortise, resulting in relative stability at the fracture, with healing by callus, rather than an open reduction with primary bone healing. The second is the use of the proximal locking screw, stabilizing the syndesmosis. In summary, the factor that most strongly supports the nail in having superior biomechanical attributes is its mode of failure. Plate constructs failed due to disruption of the hardware/bone interface whereas the nails maintained their bony fixation, failing as a result of the soft tissues. This strongly corroborates the torque at failure data derived from our mechanical testing in finding the nail as a superior construct to the plate. Using a fibular nail to fixate a Weber B, SER 4 ankle fracture has substantial benefit, especially for the elderly population and patients with comorbidities that affect their skin quality. 

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