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.

Humerus - nailing - biomechanics

References

• 1 Blum J, Machemer H, Högner M, Baumgart F, Schlegel U, Wahl D, Rommens P M. Biomechanics of interlocked nailing in humeral shaft fractures. Comparison of 2 nail systems and the effect of interfragmentary compression with the unreamed humeral nail.  Unfallchirurg. 2000;  103 183-190
• 2 Blum J, Rommens P M, Janzing H, Langendorff H S. Retrograde Nagelung von Humerusschaftfrakturen mit dem UHN.  Unfallchirurg. 1998;  101 342-352
• 3 Blum J, Machemer H, Baumgart F, Schlegel U, Wahl D, Rommens P M. Biomechanical comparison of bending and torsional properties in retrograde intramedullary nailing of humeral shaft fractures.  J Orthop Trauma. 1999;  13 344-350
• 4 Blum J, Janzing H, Gahr R, Langendorff H S, Rommens P M. Clinical performance of a new medullary humeral nail: antegrade versus retrograde insertion.  J Orthop Trauma. 2001;  15 342-349
• 5 Brand D, Knopf U, Seidel H, Schneider E. Stabilisierung von Humerusschaftfrakturen - vergleichende biomechanische Untersuchungen.  Osteosyn Int. 1996;  4 235-245
• 6 Dalton J E, Salkeld S L, Satterwhite Y E, Cook S C. A biomechanical comparison of intramedullary nailing systems for the humerus.  J Orthop Trauma. 1993;  7 367-374
• 7 Henley M B, Monroe M, Tencer A F. Biomechanical comparison of methods of fixation of a midshaft osteotomy of the humerus.  J Orthop Trauma. 1991;  5 14-20
• 8 Lin J, Inoue N, Yi-Shiong H. Biomechanical comparison of antegrade and retrograde nailing of humeral shaft fractures.  Clin Orthop Rel Res. 1998;  351 203-213
• 9 Rommens P M, Blum J, Runkel M. Retrograde nailing of humeral shaft fractures.  Clin Orthop Rel Res. 1998;  350 26-39
• 10 Schopfer A, Hearn T C, Malisano L, Powell J F, Kellam J F. Comparison of torsional strength of humeral intramedullary nailing: a cadaveric study.  J Orthop Trauma. 1994;  8 414-421
• 11 Zimmerman M C, Waite M, Deehan M, Tovey J, Oppenheim W. A biomechanical analysis of four humeral fracture fixation systems.  J Orthop Trauma. 1994;  8 233-239