gms | German Medical Science

Questionnaire: The aim of the study is to give proof whether a fully mobile knee design would result in adequate clinical and functional performance as well as in higher degrees of flexion in comparison to conventional fixed tibial bearing designs.

Methods: The e.motion FP knee is a floating platform design. The design of the femoral components is based on two main radii, one anterior radius for a long and deep patellar groove and only one radius for the main segment of both condyles. The condylar parts of the femoral component have the same transverse radius so that the condyles, together with the floating tibial PE platform, represent a ball in socket design. By this design high areal contact which is maintained from 5° of hyperextension to 90° of flexion was achieved. The tibial platform allowes for rotational movements of plus/minus 15° and 4.5 to 8 mm of sagittal displacement. The baseplate of the tibial metal tray is asymmetric. This design guarantees perfect coverage of the tibial resection plane and no lateral dorsal overhang is likely to occur. The stem shows a medial offset of 3.5% and allows the use of stem extensions.

The mid-term results include the first clinical series of 130 consecutive cases using the e.motion FP design. Clinical and radiographical data from the most recent review were entered in the study. The follow-up period was 66.4 months with a maximum of 78 and a minimum of 55 months. Diagnoses were 70% osteoarthritis (OA) and 30 % inflammatory joint diseases (IJD).

Results and Conclusions: The KSS was 98.6 points preoperatively (min. 60, max. 164, SD 18.7). The clinical score was 48.6 (min. 19, max. 90, SD 13.7), the functional score was 49.9 (min. 10, max. 90, SD 11.2).

The postoperative KSS was 184.3 points (min. 120, max. 200, SD 18.7). The clinical score was 93.8 (min. 46, max. 100, SD 8.8), the functional score was 90.5 (min. 50, max. 100, SD 14.3). ROM ranged from 80° to 140° (SD 10.3) with an average of 121.3°. 74.4% of cases had a postoperative ROM of 120° and more.

Alignment represented by the mechanical axis was excellent in 89.8% and only 3.4% were unacceptable. With manual instrumentation, an excellent result was achieved in only 71.2% and 6.1% outliers were observed.

The mid-term results using the e.motion knee system are promising. A great majority of patients show excellent function with nearly three quarters of patients with a ROM of 120° to 140°. Consequently, the knee design presented here fulfils the criteria of a high flexing knee. However, it is believed that with regard to patient selection the fully mobile floating platform design is the adequate replacement for the younger more active patient with sufficient muscular control of the kinematics of such design.Knee navigation clearly facilitates proper alignment of the components and only few outliers had to be observed. Therefore, the over-all results of the e.motion knee system, also including the use of a navigation system, favourably compare with literature data.