• Hip and knee surgery

This thesis aims to evaluate the relatively newly introduced TKA. The fully cemented, uncemented, and hybrid fixated implants were evaluated with MBRSA measurements to determine the risk of aseptic loosening, DEXA measurements to determine the adaptive bone remodeling close to the implants, and CT scans to estimate the positioning of the tibial implants.

TKA is today a very successful treatment with an implant survival of >90% after 10 years. Despite high implant survival TKA surgery tends to have a lower patient satisfaction when compared with other orthopedic procedures, with patient satisfaction of around 80%. The dissatisfaction is found to be multifactorial of which approximately 20% complain of persistent postoperative pain.
The main cause of persistent postoperative pain has been investigated but no clear etiology without conclusive evidence. However, the positioning of the tibial implant in an inward rotation or/and the femoral component with an overhang is considered to cause persistent postoperative pain.
The prosthesis was designed with the aim of minimizing the group of patients with persistent postoperative pain by optimizing the positioning of the tibial implant due to its asymmetrical design and also herby aiming for better coverage of the tibial plateau.

When introducing new orthopedic implants for clinical use a phased instruction as described by Malchau is recommended. Migration studies are the first step to assessing the risk of aseptic loosening.

Through this thesis, four different studies will be presented. Study I is a prospective study of the hybrid fixated TKA. We found acceptable values of migration for both the uncemented femoral implant as well as the cemented tibial implant although these were marginally higher. Study II was a randomized controlled trial comparing migration values of the fully cemented TKA components with the uncemented fixation. We did not find any significant difference between the two fixation types in the tibial implants. However, we did find a significant difference between the femoral implants although not reaching clinical relevance. For both the femoral and tibial implants and for both fixations types acceptable migration values were reported.
Study III evaluated the adaptive bone remodeling close to the implants. We found a decrease in BMD in the anterior femur and medial tibia regardless of fixation type and additionally a statistically significant difference for the femoral implants.
Study IV evaluated the coverage and rotation of the implants using CT-scans. Coverage and rotation values were found to be acceptable.

In conclusion, the studies in this thesis assessed the risk of aseptic loosening in the femoral and tibial implants regardless of fixation mode and found a low risk of aseptic loosening, why the implants can be used in clinical settings. Positioning of the implant regarding coverage and rotation was acceptable. Longer follow-up is recommended to evaluate if the observed decrease in BMD will have any clinical implications long-term.

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