A new press-fit stem concept to reduce the risk of end-of-stem pain at revision TKA: A pre-clinical study

Revision total knee arthroplasty presents numerous technical challenges, with lower patient outcomes compared with those obtained in primary surgery. Extended stems have been used in revision total knee arthroplasty to improve component alignment and fixation. Hybrid fixation with cemented tibial tray and press-fit stem has shown good results. One of the disadvantages of this technique is pain related to the presence of a cementless diaphyseal engaging stem, often designated as end-of-stem pain. Patients with this pain have reported a decrease in overall satisfaction, as well as demonstrate a lower clinical outcome score. Clinical findings suggest that stem material and design are important factors in the development of end-of-stem pain. Therefore, a question can be raised: can a novel press-fit stem concept minimize bone strain changes at the stem tip? The hypothesis here considered lies upon the fact, that if periosteal cortex strain changes are minimized at the stem tip comparatively to the intact situation, the risk of end-of-stem pain might be minimized.

This pre-clinical study was accomplished using synthetic tibiae to experimentally predict the periosteal cortex strains at the proximal and stem tip regions, with a commercial press-fit stem and a new stem concept.

The results demonstrated that the new stem concept has the ability to minimize strain changes induced by the stem tip at the distal periosteal cortex and consequently, at the periosteal layer of bone tissue, which is highly pain sensitive, probably contributing to the reduction of the risk of end-of-stem pain.

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