In a continuing effort to decrease variability in surgical technique, as an investigator, I endeavoured to further defined the merits and drawbacks of navigation.
The two main technologies currently available to “guide” the surgical decision-making during a total knee arthroplasty are
- computer navigation
- and case-specific cutting jigs.
Both technologies aim to eradicate the natural variation in surgeon technique.
One of the main recent areas of focus has been demonstration of the importance of the mechanical axis as a predictor of function and longevity after total knee arthroplasty.
Two studies demonstrated advantages in terms of functional outcome and implant survival following total knee arthroplasties with a neutral mechanical axis.
I reach in Guadeloupe, the same conclusions as Fang’s : Fang et al., in a report on 6070 knees, showed that outliers in terms of overall mechanical alignment were associated with a significantly higher failure rate.
The authors observed an average failure rate of 0.84% at a mean of 6.6 years after total knee arthroplasty.
Knees that were implanted in 3° to 7° of coronal anatomic alignment had the lowest failure rate (0.5%), whereas knees outside of this range had a risk of failure that was more than three times greater.
This study was larger than previous studies with conflicting conclusions.
Our own - same – conclusions are drawn from a 700 hundreds cases serie.
However, I am not so lucky as Choong et al., who performed a randomized prospective study comparing
- computer-assisted surgery (sixty knees)
- with conventional surgery (fifty-five knees).
As we did, they also demonstrated a functional advantage when implants that were implanted within 3° of a neutral mechanical axis were compared with outliers.
Furthermore, computer-assisted total knee arthroplasty was associated with a higher number of knees within 3° of neutral mechanical alignment (88% versus 61%).
As we did, Longstaff et al. also demonstrated that the functional outcome after total knee arthroplasty was significantly better for patients who had neutral mechanical alignment.
1/ Kim et al.
prospectively compared computer navigation with conventional total knee arthroplasty in a bilateral total knee arthroplasty study model involving 160 patients (320 knees).
After a mean of 3.4 years follow-up, the authors found no differences in terms of knee scores or function.
They also found no differences in terms of implant alignment between techniques with use of radiographs and computed tomography.
However, the total knee arthroplasties that were performed with computer navigation required an average of almost twenty minutes of additional surgical time.
2/ Weng et al.
also prospectively compared computer navigation with conventional total knee arthroplasty with use of a bilateral knee study model involving sixty patients (120 knees).
The authors found that computer navigation was associated with a much higher rate of knees within 3° of a neutral mechanical axis (87% versus 50%) but also increased the surgical duration by an average of about twenty minutes.
3/ In a third such study, Seon et al.
prospectively compared function and implant alignment in a study involving thirty-one knees that were treated with navigation-assisted unicondylar knee arthroplasty and thirty-three knees that were treated with conventional unicondylar arthroplasty.
After a minimum duration of follow-up of two years, there were no significant differences between the groups in terms of knee scores or function; however, there were significantly more outliers in alignment (>3° from neutral) in the conventional unicondylar arthroplasty group.
The authors also reported two stress fractures due to the creation of pin tracks in the navigation group.
While most studies have demonstrated that navigation successfully reduces the number of outliers of implant alignment,
navigation requires more operative time,
and additional study will be necessary to determine whether the improvement in implant alignment impacts long-term function or survival to offset the increased surgical time and the potential for fracture.
