The “PAMFOSS” framework: guidance for the design and application of 3D-printed implants for segmental bone defects

Reconstruction of a large segment defect resulting from an en bloc resection of an aggressive or malignant tumor in the long bones has always been difficult. 3D printing technology can overcome many of the limitations encountered with traditional implants produced using conventional manufacturing processes. It can produce metal prostheses that meet necessary standards for biocompatibility, mechanical strength, and elastic modulus. They can also realize stable fixation, conformational matching and excellent osseointegration. Taken together, 3D-printed implants offer many of the conventional implant offerings, with added value of patient-specific and custom designed flexibility. To better characterize and define the process by which a of 3D-printed prosthesis is designed and printed, we have introduced 7 fundamental considerations, which are collectively termed the “PAMFOSS framework”. These include “Precision”, “Articulation”, “Materials”, “Fixation”, “Osseointegration”, “Soft-tissue coverage and reconstruction”, and “Sustainability”. Using this framework, we have been able to consider, plan and implement 3D-printed metal prostheses successfully for reconstruction across a wide array of defects, including defects of the humerus, radius, ulna, femur and tibia. Additional efforts are required to further improve the design and manufacture time, to optimize the fixation method and osseointegration, to maximize soft-tissue coverage or attachment, and to address limb length discrepancy encountered in the skeletally immature patient population.