A new technique for measurements on long bones: development of a new instrument and techniques comparison

In this paper we present a new instrument for measurements on long bones. The instrument is based on the use of a digital coordinatometer-goniometer connected to an optical collimator: such device allows angles as well as lengths to be measured. With regard to observing procedures, an innovative method for bone axis location by points has been applied. It is also possible to locate an axis using a symmetry and tangency criterion. As for torsion angles, the proposed technique is absolutely new; it utilizes a reference plane, which the bone must be leaned against, and the symmetry conditions that are generated by rotating the bone around an axis orthogonal to this plane. In order to verify the precision of the new instrument (digital osteogoniometer), several tests were performed. For this purpose we have studied the results of measurements carried out with the new instrument as well as with traditional apparatuses by four different observers on a sample of 10 skeletons (humerus, radius, ulna, femur, tibia of left side). The analysis of intrapersonal and interpersonal differences points out that the new osteogoniometer is more precise in angular measurements than traditional instruments. Moreover the time requested for carrying out measurements prooved to be shorter, above all with regard to torsion angles measurements.