February 01, 2015
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No significant improvement in functional outcomes seen with navigated TKA

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DALLAS — Research using data from the New Zealand National Joint Registry on one modern implant design indicates that use of computer navigation for patients undergoing total knee arthroplasty did not improve functional outcomes at midterm follow-up.

“In this cohort of 9,000 total knee arthroplasties performed for primary osteoarthritis using a single implant, we found no difference in functional outcome, no difference in mortality and no difference in implant survivorship at 5 years,” Simon W. Young, MD, FRACS, said during his presentation at a recent meeting. “It may be mid-term follow-up is too early to identify the impact of improved alignment in the navigated group, and we will continue to follow this cohort with interest.”

Navigation vs conventional methods

Researchers analyzed the results of 9,054 primary total knee arthroplasties (TKAs) performed between 2006 and 2012 using Stryker’s Triathlon knee.  Of these, 3,329 TKAs were implanted using computer navigation and 5,725 were performed using conventional instruments. The investigators studied Oxford Knee Scores (OKS) at 6 months and 5 years postoperatively and used a multivariate model that adjusted for patella resurfacing, cementation, approach, implant type, theater ventilation, bearing type,  hospital, surgeon experience, and patient age, sex, comorbidities to analyze the effect of surgical duration on functional and revision rates.

Univariate analysis showed the navigation group had a higher OKS at 6 months vs. the conventional group. However, a multivariate analysis showed this difference was not statistically significant. At 5 years, researchers also found no difference in mean OKS between groups. Although results showed lower volume surgeons had lower OKS, functional outcome in high- or low-volume surgeons was not improved by the use of navigation. Investigators found no significant difference in 5-year revision rates between navigated and non-navigated TKA.

Analysis of patients younger than 65 years showed a trend toward worse outcomes in the navigated group; however, multivariate analysis showed no statistical differences in survivorship between the groups in this cohort of patients.

The investigators also studied the potential impact of navigation on patient mortality. “We cannot see evidence of this improvement in navigation in terms of mortality at either 30 days or 6 months, again controlling for factors such as age and gender,” Young said. “What is clear is that navigation increases surgical duration on average by 12 minutes, with mean skin-to-skin time in a navigated knee is 91 minutes [for a] convention knee, 79 minutes.”

Future research

Young told Orthopedics Today, “Recent data from the Australian Registry on other implants with 10-year follow-up is starting to show a survivorship benefit to navigation. It may be that with longer follow-up, we will start to see this in our cohort also.”

He added, “We had hoped to see an improvement in short-term functional outcomes with navigation, as this has been reported in some randomized trials, admittedly with a small number of patients. However, with the outcome instrument we used, the Oxford Knee Score at 6 months, we did not see a difference in functional outcome with navigation.”

Although this study showed no difference in functional outcome between computer navigation and conventional instruments, the researchers hypothesize that a longer follow-up may show better results.

Young told Orthopedics Today, “In New Zealand, 37% of this particular prosthesis are implanted using navigation, meaning it is an excellent comparative group with which to assess the effect of navigation.” – by Casey Tingle

References:

Young SW. Paper #6. Presented at: American Association of Hip and Knee Surgeons Annual Meeting; Nov. 6-9, 2014; Dallas.

For more information:

Simon W. Young, MD, FRACS, can be reached at the North Shore Hospital, Private Bag 93-503, Takapuna, Auckland City 0740, New Zealand; email: simonwyoung@gmail.com.
Disclosure: Young received research support from Vidacare and institutional support from Stryker.