Fracture stiffness measurement using the orthometer: reproducibility and sources of error.
OBJECTIVE
To elicit the reproducibility and the common sources of error in the use of the Orthometer, a commercially available goniometer based system, designed to measure the stiffness of healing fractures.


METHODS
A laboratory based study.


BACKGROUND
The Orthometer is widely used to measure the progress of fracture healing in a quantitative manner. It has been shown previously that the bending stiffness of a fracture increases with healing and that a stiffness of 15 Nm/degree equates with the functional union of a tibial fracture.


METHODS
The Orthometer was attached in a standard manner to nylon bars of known stiffness to determine the accuracy of the device. The Orthometer was then set up with changes in a single positional variable to assess the effect of this variable on the measurement accuracy. A number of different clinicians were asked to use the Orthometer before and after a simple training session and any improvements in the measurement accuracy were observed.


RESULTS
Stiffness could be measured to within 10% or less of the true stiffness. Markedly different degrees of error were introduced with the various set-up variables. A simple training session improved clinician accuracy.


CONCLUSIONS
Although the Orthometer does allow some degree of safety margin, it is essential that set-up is performed carefully, and that the clinician has been trained in the use of the device.


CONCLUSIONS
Quantitative measurements of fracture healing have enormous potential benefits over manual and radiological methods of assessments. Provided these are carefully performed, the accuracy of these measurements is good.
Eastaugh-Waring
S J
SJ
Department of Orthopaedic Surgery, University of Bristol, Bristol Royal Infirmary, Bristol, UK.
Hardy
J R
JR
Cunningham
J L
JL
D004548:Elasticity; D004867:Equipment Design; D005069:Evaluation Studies as Topic; D017102:Fracture Healing / Q000502:physiology*; D050723:Fractures, Bone / Q000503:physiopathology*; D006801:Humans; D009983:Orthopedic Equipment; D015203:Reproducibility of Results; D012107:Research Design; D012399:Rotation; D013314:Stress, Mechanical