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Internal Fixation of Dorsally Displaced Fractures of the Distal Part of the Radius

A Biomechanical Analysis of Volar Plate Fracture Stability

¹ Tri-County Orthopaedics and Sports Medicine, 160 East Hanover Avenue, Morristown, NJ 07962
² Biomechanics Laboratory, Division of Orthopedic Research, Mayo Clinic, 200 First Street S.W., Rochester, MN 55905
³ Department of Orthopedic Surgery, Mayo Clinic, 200 First Street S.W., Rochester, MN 55905. E-mail address: cooney.william{at}mayo.edu

Investigation performed at Mayo Clinic, Rochester, Minnesota

NOTE: The present study was supported by a research grant from the Department of Orthopedics, Mayo Clinic/Foundation, Rochester, Minnesota. The authors thank Synthes and Hand Innovations for donating the plating systems tested.

In support of their research for or preparation of this manuscript, one or more of the authors received grants or outside funding from the Department of Orthopedics, Mayo Clinic/Foundation, Rochester, Minnesota. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated. The plating systems were donated by Synthes and Hand Innovations.

Methods: With use of a previously validated Sawbones fracture model, a dorsally comminuted extra-articular distal radial fracture was created. The fracture fixation stability of four volar plates (an AO T-plate, an AO 3.5-mm small-fragment plate, an AO 3.5-mm small-fragment locking plate, and the Hand Innovations DVR locking plate) were compared under axial compression loading and dorsal and volar bending simulating the in vivo stresses that are generated at the fracture site during early unopposed active motion of the wrist and digits. A single dorsal plate (an AO pi plate) was used for comparison, with and without simulated volar cortical comminution. The construct stiffness was measured to assess the resistance to fracture gap motion, and comparisons were made among the implants.

Results: The volar AO locking and DVR plates had greater resistance to fracture gap motion (greater stiffness) compared with the volar AO nonlocking and AO T-plates under axial and dorsal loading conditions (p < 0.01), with no significant difference between the AO volar locking and DVR plates. The volar AO locking plate had greater resistance to fracture gap motion than did the volar AO nonlocking plate under axial loading and dorsal bending forces (p < 0.01). The dorsal pi plate had the greatest resistance to fracture gap motion under axial loading and volar and dorsal bending forces (p < 0.01). However, the pi plate was significantly less stable to axial load and dorsal bending forces when the volar cortex was comminuted (p < 0.01).

Conclusions: In this model of dorsally comminuted extra-articular distal radial fractures, dorsal pi-plate fixation demonstrated better resistance to fracture gap motion than did the four types of volar plate fixation. The AO volar locking and DVR plates conferred the greatest resistance to fracture gap motion among the four volar plates tested. Volar locking technology conferred a significant increase in resistance to fracture gap motion as compared with nonlocking plate technology.

Clinical Relevance: The present study provides comparative biomechanical data that may be helpful for individualizing plate fixation techniques and postoperative rehabilitation protocols for the treatment of dorsally comminuted extra-articular distal radial fractures. While the dorsal pi plate had the highest resistance to fracture gap motion, the locked volar plates showed significantly higher resistance to fracture gap motion than the unlocked plates did, suggesting that either surgical approach (dorsal or volar) combined with rigid plate fixation should allow for early assisted finger and wrist motion in the treatment of comminuted distal radial (Colles-type) fractures.

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