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A functional classification of spinal instrumentation
1Cherry Way Orthopaedics, P.C., 425 First Avenue @ Cherry Way, Pittsburgh, PA 15219, USA. cherryway@pol.net
Background Context:
Spinal instrumentation systems have evolved far beyond the original Harrington design, with increasing complexity and capabilities. This review attempts to de-emphasize the "product names," as systems are often generically and inappropriately referred to as "Harrington rods," by introducing a functional classification for current systems.
Purpose:
The aim of this paper is to review the intended design purpose of current spinal instrumentation systems for more accurate interpretations of radiographs and complications.
Study Design:
The principles involved in each type of instrumentation system are described, followed by the characteristic components and the normal appearance radiographically, with examples of complications, which should be recognized.
Methods:
The historical contribution of specific systems in the developing art of internal fixation of the spine is provided as a background to understand the biomechanical forces imparted by spinal hardware. Recognizing the functional intent of spinal constructs will enhance descriptions of those images.
Results:
Spinal instrumentation has been categorized into five functional types: Distraction and compression, segmental stabilization, coupled or derotation systems, translational or pedicle screw systems, and anterior instrumentation.
Conclusions:
Analysis of radiographs from a functional viewpoint can enhance the descriptive interpretation and specifically allow assessment of the success or of the presence of complications, which are crucial to the analysis of instrumentation effectiveness.
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