| Abstract / Summary | Total Knee Arthroplasty (TKA) is considered a good well established treatment for patients with
painful gonarthroisis. The number of TKA performed in Denmark has been increasing during the
recent years, and now more than 7500 are performed each year. The survival probability of a TKA
is far above 90 % after 10-years. The most common reasons for a TKA to fail are aseptic loosening,
infection, wear-particle disease and pain without loosening..
Revision Total Knee Arthroplasty (rTKA) is sometimes difficult and especially if reconstruction of
major bone loss is needed to secure a stable platform for fixation of the new implants. Conventional
surgical options for reconstruction of the bone loss are cement filling or the use of bone grafting. A
new porous Tantalum biomaterial shaped as a cone is commercially available under the trademark
“Trabecular Metal Cone” (TM Cone, Zimmer, Warsaw, IN). It is designed and developed for
reconstruction of bone loss in the proximal tibia during rTKA. Tantalum is well documented as a
highly biocompatible material with the appearance similar to cancellous bone. Porous tantalum has
the advantage to allow osseointegration, while filling out bone defects and tolerate physiological
loads. At the department of Orthopaedic U, Rigshospitalet patients are admitted from large parts of
Denmark to received rTKA due to failed TKA combined with severe bone loss. The use of TM
Cone in rTKA in patients with considerable bone loss of the proximal tibia is evaluated in a
randomized study where 40 patients were allocated to receive rTKA with or without TM Cone.
In a study using Roentgenstereometric Analysis (RSA) micromotion of the tibial implants in the
two randomized groups were evaluated. In two studies using Dual Energy X-ray Absorptiometry
(DEXA) changes in Bone Mineral Density (BMD) of the tibia and distal femur were measured. Due
to the potential of osseointegration of the TM Cone implants our hypothesis was that less migration
of the tibial implants and an increase (or less decrease) in BMD of the tibia was expected in the
group of patients that received rTKA with TM Cone.
In the first study we found a tendency of less migration in the TM Cone group, but this was not a
significant finding, and all implants seemed to stabilize between 6 months and 1 year of follow-up.
In this study we also evaluated the knee - and function scores and both showed a significant
increase, but no difference between the two study groups was found.
In the next study, we found that the bone remodelling pattern was the same in the two groups, with
a significant decrease in BMD found along the stemmed tibial implant in both groups. There was
no significant difference in BMD changes between the two groups after 1 year of follow-up. The
second DEXA study only evaluated BMD changes at the distal femur after rTKA with the use of a
100 mm stemmed implant and a potential difference between rTKA with or without TM Cone was
not evaluated. We found a significant increase in BMD in one ROI (Region of interest) after 1 year
of follow-up.
Our preliminary results have shown that the use of TM Cone in rTKA in patients with severe bone
loss of the proximal tibia gives the same early clinical outcome as conventional surgical
management. The adaptive bone remodelling of the tibia and migration of the tibial component of
the two study groups within the first postoperative year was not statistically different and further
investigation with long term follow-up is warranted.
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