Abstract
INTRODUCTION
The magnitude of knee flexion angle is a relevant information during clinical examination of the knee, and this item is a significant part of every knee scoring system. It is generally performed by visual analysis or with manual goniometers, but these techniques may be neither precise nor accurate. More sophisticated techniques are only possible in experimental studies. Smartphone technology might offer a new way to perform this measurement with increased accuracy.
MATERIAL
20 patients operated on for unicompartmental or total knee replacement with help of a navigation system participated to the study. There were 13 women and 7 men with a mean age of 72.1 years.
METHODS
All patients were operated on for unicompartmental or total knee replacement. All patients were operated on with help of a non-image based navigation system. The navigation system is able to measure very accurately the knee flexion angle. The Smartphone application allows measuring this angle in two steps 1) recording the reference position by putting the Smartphone on the operating table, 2) recording the knee flexion angle by putting the Smartphone against the tibial crest. Two observers participated to the study. The first observer performed three independent navigated measurements followed by three independent Smartphone measurements while positioning the knee under visual control in full extension, at 0°, 30°, 60°, 90° of knee flexion and at maximal flexion; the second observer performed only one set of measurements. The intra- and inter-observer variability was assessed by calculation of the intra-class correlation coefficient. Navigated and Smartphone data were compared by a paired Wilcoxon test and calculation of the Spearman coefficient of correlation at a 5% level of significance.
RESULTS
There was no significant difference between paired navigated and Smartphone measurements at any degree of knee flexion. There was a strong correlation between the two data sets. The intra- and inter-observer reproducibility was high.
DISCUSSION-CONCLUSION
There was a high agreement between the navigated measurements considered as the reference and the Smartphone measurements. This new technology is easy to use and extensively available. It allows improving significantly the precision and the accuracy of the measurement of the knee flexion angle without technical difficulties. This technique might allow a self-control by the patient of the progression of the post-operative rehabilitation.
SUMMARY
The Smartphone application allows improving significantly the precision and the accuracy of the measurement of the knee flexion angle without technical difficulties.
