Humeral Nailing: A Biomechanical Comparison of Stryker T2 and Synthes UHN

Abstract

Intramedullary nailing of humeral shaft fractures has become a treatment of choice in the management of humeral shaft fractures over the last years. To reach a sound bony fusion high mechanical stiffness is mandatory in these nails. Previous clinical and biomechanical studies have shown the Synthes UHN to have the most adequate stiffness within the field of competition. In the present biomechanical study the Stryker Trauma T2 humeral nail, which represents the newest generation of humeral shaft nails, was compared to the Synthes UHN. The implant stiffness was determined in a test set-up using human cadaver bones. For nail implantation the unreamed technique in a retrograde approach was chosen. During the implantation procedure the instrumentation of both systems was assessed. In bending and torsional stiffness no significant differences were found between UHN and T2 groups. However, the T2 showed smaller values in torsional play between nail and locking screws which increased its overall high torsional stiffness. The tests also showed that UHN- and T2-implants are both able to restore the torsional and bending stiffness of fractured bones to almost 50 % of the intact ones. A high torsional stiffness guarantees a minimum of undesired shear forces in the fracture zone. As shown in the present and in previous studies the torsional stiffness found for UHN and now T2 is comparatively high and more adequate for sound healing when compared to competitors such as the Russell Taylor, expandable nail types or any non-locking nails. Especially in cases of transverse and short oblique fractures a high torsional stiffness is beneficial to prevent pseudarthrosis. Concerning instrumentation both systems are characterized by a high degree of sophistication. However, the T2 system shows advantages in preparation of the entry portal by an efficient conical rigid reamer as well as by a target device with a safe and easy-to-use clamping mechanism. Summarizing, these results indicate the T2 humeral nail system to be mechanically adequate for sound healing and advantageous in its instrumentation vs. the competition.

Key words

Humerus - nailing - biomechanics

References

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