Leg Axis After Computer-Navigated Total Knee Arthroplasty: A Prospective Randomized Trial Comparing Computer-Navigated and Manual Implantation

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Abstract

To compare the alignment after computer-navigated total knee arthroplasty, 52 patients were randomly allocated to 2 groups. Twenty-seven patients received a total knee arthroplasty with the aid of a kinematic computer-navigation system, and 25 patients received a total knee arthroplasty with the conventional method. Both groups were well balanced concerning demographic data and preoperative scores. At 3-month follow-up, the mechanical alignment of the leg reached the desired straight axis in more cases with the computer-navigated implantation. This difference was statistically significant. The femoral and tibial mechanical anteroposterior axis and the femoral and tibial sagittal tilt (slope) measured on sagittal x-rays were not significantly improved in this patient group.

Section snippets

Patients and Methods

We compared 25 manually-implanted TKAs with 27 computer-navigated implantations. Patients included in the study had primary or secondary knee osteoarthritis severe enough for total knee arthroplasty. The study protocol and consent forms were approved by the local ethical committee. Sixty patients were considered for inclusion in the study. Six patients met 1 or 2 of the exclusion criteria defined and 2 patients did not give their consent, so that, finally, 52 patients entered the study. The

Demographic Data

The demographic data for the 2 groups of patients were similar. The mean age of the 25 patients who had a manual TKA was 67.3 years (SD, 3.3 years) compared with 64.7 years (SD, 9.4 years) for the 27 patients with a computer-navigated TKA. This difference was not significant (P = .30). The body mass index in the first group was calculated at 30.2 (SD, 4.95), compared with 27.9 (SD, 3.55) in the second group. This was not significantly different (P = .08). The demographic features of both groups

Clinical Evaluation and Scores at 3-Month Follow-Up

At the 3-month follow-up evaluation, the mean range of motion for the entire study group was 104° (SD, 17°). The differences in range of motion between the group that had a manually implanted prosthesis compared with the group who had a computer-navigated procedure were not significant (P = .369). We could not detect a significant difference in the overall clinical score of the Knee Society and the WOMAC as a disease-specific outcome measurement, as shown in Table 4.

Discussion

Basically, there are two fundamentally different ways of navigation in total knee arthroplasty. Some of the new navigation systems available today rely on reconstructed, 3-dimensional, Computer tomography-based models of the leg. Typically, these “image-based” models can be used for an intraoperative navigation, after matching bony landmarks, over an infrared link to a computer. These systems depend on a computer tomography, which leads to a higher dose of radiation and an increase in the

Acknowledgment

The authors thank Dr R. Muche of the Department of Biometrics and Medical Documentation of the University of Ulm for his help with the randomization and the statistical evaluation.

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