Load-Displacement Behavior in a Distal Radial Fracture Model. The Effect of Simulated Healing on Motion

External fixation of fractures of the distal end of the radius neutralizes external forces and maintains axial alignment during healing. As far as we know, there have been no biomechanical studies of the effects of early removal of the fixator in a partially healed fracture model. The purpose of the...

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Bibliographic Details
Published in:Journal of bone and joint surgery. American volume 1999-01, Vol.81 (1), p.53-59
Main Authors: WOLFE, SCOTT W, LORENZE, MARK D, AUSTIN, GREGORY, SWIGART, CARRIE R, PANJABI, MANOHAR M
Format: Article
Language:English
Subjects:
Biological and medical sciences
Bone Wires
Cadaver
Colles' Fracture - physiopathology
Colles' Fracture - surgery
External Fixators
Fracture Fixation - methods
Fracture Healing - physiology
Humans
Medical sciences
Models, Biological
Osteotomy
Range of Motion, Articular - physiology
Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases
Technology. Biomaterials. Equipments
Weight-Bearing - physiology
Wrist Joint - physiopathology
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Summary:External fixation of fractures of the distal end of the radius neutralizes external forces and maintains axial alignment during healing. As far as we know, there have been no biomechanical studies of the effects of early removal of the fixator in a partially healed fracture model. The purpose of the present study was to observe the load-displacement behavior of a distal radial fracture model in which we had simulated partial healing by injection of butyl-rubber caulk and augmented this simulated healing with Kirschner-wire fixation. Sixteen fresh-frozen hand-wrist-forearm specimens from cadavera were mounted in mid-rotation in resin pots, and a load was applied. An osteotomy was used to simulate the fracture. Relative motion at the site of the osteotomy was compared, with use of a three-dimensional Optotrak kinematic device, during physiological loading of six constructs with Kirschner-wire transfixion or outrigger fixation. In the experimental group, partial healing was simulated by injection of butyl-rubber caulk into the site of the osteotomy and testing with simulated muscle-loading was performed through a full range of motion of the wrist. No difference could be detected between the relative motion at the osteotomy sites that had been treated with standard fully augmented external fixation and that in the experimental group (p > 0.05). T test analysis revealed that motion was equivalent regardless of whether Kirschner-wire transfixion or outrigger fixation had been used (p = 0.62) and that all of the augmented constructs had significantly less relative motion than all of the nonaugmented constructs (p < 0.001). CLINICAL RELEVANCEIn clinical practice, early removal of a standard external fixator is desirable to prevent stiffness, provided that the removal does not decrease the stability of the fracture. We found that the combination of partial simulated healing and augmentation with Krischner wires in vitro provided stability that was comparable with that provided by full fixation without simulated healing in an acute-fracture model. These findings support the concept of modular disassembly of the external fixator to allow an early range of motion of the wrist.
ISSN:0021-9355
1535-1386
DOI:10.2106/00004623-199901000-00008