3D-printing for the precision assessment of a new medical device

Abstract

Additive manufacturing played a keyrole in investigating the precision of a recently-developed device that measures the elastic characteristics of the trabecular bone by simulating the application of loads on a virtual biopsy obtained from radiographic images of the proximal epiphyses in the patient’s hand fingers. The simulation results are combined in a Bone Structure Index (BSI), which has shown to be able to detect trabecular bone alterations due to osteoporosis or other pathological situations. In order to obtain a large number of measurements without having voluntary patients undergo unnecessary radiations, the precision assessment tests were carried out on a 3D-printed phantom hand, in which different mimicked trabecular structures (chips) were inserted. Each mimicked bone had a unique internal structure and density and was 3D-printed using radiopaque composite materials. Fifteen different chips were additively manufactured; 20 measurements were performed on each chip. BSI and BSI_T-score precision values were computed according to ISO 5725 and ISCD standards. For all the chips, no relationship was found between the mean $m_j$ and standard deviation $s_j$ of the measurements in each chip. The range of the 95% confidence interval ( $CI$ ) was computed assuming the repeatability standard deviation $s_r$ as the known standard deviation of the measurement method (average of $s_j$ values): ${CI}_{\mathit{BSI}}=\pm 8.14$ , corresponding to ${CI}_{\mathit{Tscore}}=\pm 0.36$ . Least Significant Change was evaluated as well: ${\mathit{LSC}}_{\mathit{BSI}}=13.1$ , corresponding to ${\mathit{LSC}}_{\mathit{Tscore}}=0.58$ . The 95% confidence intervals are small when compared to the commonly-accepted diagnostic values, where a patient is classified as osteoporotic if T-score < −2.5, non-osteoporotic if T-score > -1 and osteopoenic if -2.5 < T-score < -1. The LSC results are in line with the requirements for the gold-standard osteoporosis diagnostic systems. Additive manufacturing made it possible to avoid irradiation of humans in this precision assessment.