Abstract
Introduction
PSI technology have proved helpful in difficult primary Total Knee Replacement. However applying it to revision was impossible due to multiple factor. To Start with the landmark We usually destroy it. There is an extensive damage at the bone at the epiphysis, the implant prevent an accurate visualization and debridement usually change the surface of the bone as well which make applying the psi dyed impossible, we are proposing a new way of using psi in revision where we don't depend on the all masses adjusted in primary. However we depend on the metaphysical area of the bone.
Material & method
We have reviewed 56 MRI & CT scans for cases posted for revision and showed clearly that in spite of the extensive bony destruction and metal presence the MRI / CT scan we were able to visualize well the metaphysical area in the intramedullary canal in both tibial and femoral we have established a special external guide that depends on the outside surface of the metaphysis of the femur. We have tried this model on six plastic bone and showed that this external guide can give the accurate details that the surgeon is looking for in a revision surgery
Result & discussion
We have performed revision surgery on six bony model utilizing the new external guide that depend on the metaphysical bone mark. In all cases we were able to have a good lock for the external guide enabling us to precisely indicate the flexion extension joint line as well as the femoral rotation accurately. The guide established to us were the trial component should be seated and the surgery after that was quite easy filling the gap with necessary block and augment based on the accurate joint line. Furthermore, performing the surgery this way enabled us to offreem in order to correct the deformity that may result from the fixed angle of the stem in both femoral and tibial component. Our suggested way of performing the revision surgery is to use the metaphysical guide to indicate the entry point for reaming. this will allow the surgeon to offream after which the external guide also block the phantom or trial component indicating both flexion and extension joint line and rotation. After that the surgeon build up to the joint line.
Conclusion
Depending on a new landmark outside metaphysical and suggesting a new type of guide will make psi possible regardless of the amount of bony destruction in the epiphyseal area. Furthermore performing the surgery this way will decrease the error that is based on the judgment of the surgeon for his joint line and rotation and point of entry. We believe that further work and development is needed to make it durable for commercial.
