Test of Designing and Manufacturing a Polyether Ether Ketone Endoprosthesis for Canine Extremities by 3D Printing

Abstract

Total limb amputation is quite common in small animals, although most of the indicated pathologies do not need such a restrictive procedure. Exo-endoprosthesis is a suggested alternative for the enhancement of the biomechanical situation of these patients. 3D printing of the internal part of exo-endoprostheses in polyether ether ketone (PEEK) is evaluated. Two different shapes of this internal part—one for radius’ and the other for cylindrical medullary cavities—were assessed. Proper PEEK temperature settings for 3D printing, the internal part of exo-endoprostheses, by fused filament fabrication (FFF) were obtained. Printing trials were carried out for different dimensions and printing orientation of these parts to achieve the best bone anchorage and thread strength outcomes. Pull-off strength tests for different surfaces of the internal part were performed with a best outcome for positive surfaces. All printed internal parts were inserted in canine tibiae and radii for an ex vivo assessment of bone anchorage and thread strength parameters. The best printing results were obtained at 410 and 130°C of the nozzle and bed temperatures, respectively. Also, a positive correlation was observed between the printing code, quality, and take-off time, while inverse correlation was shown between the take-off and the printing code, or quality, just like the print-bed temperature and the printing code. The positive surfaces had the best pull-off strength outcomes. Excellent bone anchorage and thread strength outcomes were obtained for one variant of each internal part shape. Designed devices had shown good threaded rod’s fitting inside the PEEK plug and perfect bone anchorage of the PEEK plug for tibiae and radii. In addition, iteration of manufacturing PEEK small devices by FFF technology has been shown due to small standard deviation of most variants.

Biomechanical Test of a New Endoprosthesis for Cylindrical Medullary Canals in Dogs

“…The assessed endoprosthesis was patented by Mendaza et al ( 19 ) and was composed of two main elements: (i) the PEEK sleeve, composed of a base, “umbrella”, neck, and stem ( 36 ), which will be in contact with bone tissue, and (ii) surgical metal threaded rod, made of AISI 316 austenitic stainless steel, which will be attached to an exoprosthesis ( Figure 1 ).…”

“…All 3D models were horizontally oriented with respect to the printing bed ( 36 ). The largest axes of the endoprostheses and tensile test samples with dog bone shapes were oriented parallel to the printing bed ( Figure 2 ).…”

“…After measure, the medullary canal was drilled with a 9 mm bit to homogenize the canal. Two PLA 3D-printed self-designed surgical guides were used to make perpendicular cuts and to align drilling ( Figure 3 ) ( 36 ). Insertion of the endoprosthesis was made by soft blows with a hammer.…”

“…The diameter of the inner cavity of the PEEK sleeve was 6 mm just like the diameter of the threaded rod. This cavity was slightly reduced at the level of the stem for applying extra-radial compression to the bone, such as that described by Mendaza-DeCal et al (36).…”

“…This printer reaches a nozzle temperature of up to 450 • C, bed temperature of up to 160 • C, and chamber temperature of up to 90 • C. Before printing, 3D virtual models were sliced by Simplify 3D software (Cincinnati, USA). All 3D models were horizontally oriented with respect to the printing bed (36). The largest axes of the endoprostheses and tensile test samples with dog bone shapes were oriented parallel to the printing bed (Figure 2).…”