The Fibular Intramedullary Nail Versus Locking Plate and Lag Screw Fixation in the Management of Unstable Elderly Ankle Fractures: A Cadaveric Biomechanical Comparison

SLR - February 2021 - Trevor R. Klinkner

Level of Evidence: Level 5 - cadaveric study

Scientific Literature Review 

Reviewed By: Trevor R. Klinkner, DPM
Residency Program: Inova Fairfax Medical Campus – Falls Church, VA

Podiatric Relevance: Ankle fractures are the third most prevalent fracture seen in the elderly patient population. Poor bone quality in osteoporotic and diabetic patients may lead to more complicated fracture patterns and problems with fixation. The soft tissue envelope may be compromised through CVD, prolonged steroids, and diminished skin turgor. The fibula intramedullary nail benefits from a minimally invasive technique, resulting in fewer lateral sided soft tissue complications including infection and implant removal. The authors looked to compare the biomechanical failure properties of the fibular intramedullary nail and locking plate in the management of OTA/AO 44-B elderly ankle fractures.

Methods: This is a comparative cadaveric study with 12 fresh-frozen cadaveric lower limbs (six matched-pairs). The mean specimen age was 86.5 years. A simulated 44-B fracture was created by dividing the fibers of the AITFL and PITFL, then performing an oblique fibular osteotomy. The medial malleolus and deltoid ligament were left intact to simulate successful medial sided fixation. These were then randomly allocated within each pair to the two constructs. In the nail group, a 110-millimeter × 3.6-millimeter diameter nail was used with a single 50-millimeter proximal locking screw inserted across the syndesmosis. In the locking plate group, a bicortical 3.5-millimeter fully threaded lag screw was placed and a six-hole precontoured distal fibular locking plate was then secured with a combination of 2.7 and 3.5 millimeter screws. The limbs were secured with the foot rigidly held in 20 degrees of supination, loaded to 700N and subjected to progressive external rotation until failure.

Results: Mean torque to failure was 23.5 Nm in the intramedullary nail group vs. 21.6 Nm in plate fixation group. Angle at failure was the only statistically significant finding between the two groups with a greater angle in the nail group. 5/6 nail specimens failed at the lateral ligament complex, either through ligamentous avulsion or a small bony avulsion from the distal fibula. In the plate fixation group, three specimens failed because of pull-out of the proximal locking screws with an associated diaphyseal fracture and three failed distally via locking screw pull out from the distal fibula.

Conclusions: The findings support use of either construct in a cadaveric specimen with an average age of 86 years. While the intramedullary nail did show a better mean torque to failure of 1.9 Nm, the only statistical significance was demonstrated in the angle of failure, which favored the intramedullary nail by a mean of 13.2 degrees. The values recorded for torque to failure in this biomechanical study are comparable to that found by other authors in biomechanical studies. While this study did have a smaller sample size, this was due to their emphasis on using matched limb pairs to improve the validity of the results. While larger sample size and more human data should be performed to further assess the real-world strength of these two fixation constructs, this study is a nice step toward revealing the efficacy of intramedullary nails, especially in those elderly patients with significant risk factors for wound healing complications.