Clinical Results

Parallax-Free Measurement of the Leg Axis

Precision measurement of the navigated, reconstructed mechanical leg axis in implanting a total knee prosthesis. Ritschl et. al. Poster CAOS 2002, Santa Fe

The post-operative full standing x-ray is not accurate enough to quantify axial malalignment of less than 3°, a range which can be expected with navigated TKR.

Material and Method
For the intra-operative determination of the leg axis and its intersection with the center of the hip joint on one side and the ankle on the other side, a parallax-corrected projection method was developed using a calibrated c-arm. The method allows the measurement of the leg axis with a validated accuracy of 0.5°. PiGalileo was used for the implantations.

Results
Intra-operative measurements in 54 consecutive cases showed on average a reconstruction accuracy of 0.95° in 68.3% of the cases (3.1° in 99.9%). On the tibia the axis was reconstructed with an accuracy of 1.2° in 68.3% of 25 consecutive cases (4.1° in 99.9%).

Discussion
With the proposed method, the accuracy of the axis reconstruction can be determined with precision. PiGalileo allows the reconstruction of the mechanical leg axis within a desired range of ±3°.

Resection Accuracy and OR-Time

Computer-assisted cutting guide for total knee replacement. First clinical experiences Gellner et. al. Poster CAOS 2001, Davos

Influence of PiGalileo CAS on resection accuracy, OR-timeand surgical preparation.

Material and Method
During 20 TKR surgeries, each conventional and CAS-supported, the resection accuracy was determined using a template and a feeler gage. Furthermore the incision length and the OR-time were measured.

Result
The measurement showed on average smaller gaps in all CAS-supported TKR cases. The incision on average was approx. 1.5 cm longer due to the femoral clamp of the CAS. 10 minutes additional OR-time were required for the PiGalileo cases, however this can be reduced by frequent use of the system.

Discussion
Using the electro-mechanical positioning device PiGalileo CAS leads to more precise bone resection compared to conventionally performed resections. This is an important prerequisite for higher primary stability and improved bone apposition.