Bone radiogrametry: caliper versus magnifying glass.

Radiogrametry was done on 100 hands by two observers using two methods: (1) caliper and (2) magnifying glass measurement. At the mid-point of the second metacarpal, the total width (D) and medullary width (d) were measured and cortical thickness (C) was calculated from the difference (D-d). Statistical analysis disclosed that the intra-observer CV is smaller for both observers using the magnifying glass than with the caliper (1.9 and 2.1% vs. 2.8 and 4.3%, respectively). The inter-observer CV is also less with the magnifying glass (4.2 and 5.7% vs. 6.2 and 6.9%, respectively). Although measurements made with each method correlate significantly, the values (mean +/- SD) obtained in isolated measurements using each method differ significantly, with C for both observers, as well as the intra-observer coefficient of variation (CV), being smaller. These results, which demonstrated different bone mass values as quantitated using a caliper or magnifying glass, indicate the greater reliability and precision of the latter method.