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Two different TKA alignment techniques yielded similar functional outcomes
Tibial components were more in varus and femoral components were more in valgus in the kinematic alignment vs the mechanical alignment group.
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ORLANDO, Fla., USA — Among patients who underwent total knee arthroplasty, researchers found no difference in 2-year functional outcomes between when they used kinematic alignment or mechanical alignment techniques during implantation, according to results presented at the Knee Society Specialty Day Meeting, here.
“We found no difference in 2-year patient-reported outcome scores in [total knee arthroplasties] TKAs implanted using the kinematically aligned vs. mechanically aligned technique,” Simon W. Young, MD, FRACS, of the University of Auckland in New Zealand, told Orthopedics Today Europe. “We did not find evidence for the theoretical advantages of improved pain and function that form the basis of the design rationale for kinematic alignment. Longer term follow-up is needed to see if the alterations in component alignment seen with [kinematic alignment] will compromise the long-term survivorship of TKA.”
Mechanical vs kinematic alignment
Young and colleagues received The Chitranjan S. Ranawat, MD, Award for this research.
They randomly assigned 99 patients undergoing primary TKA with the Triathlon prosthesis (Stryker) to either a mechanical alignment or kinematic alignment group and then assessed all patients’ preoperative alignment with full-length MRIs and their postoperative alignment with CT scans. In addition, Young and colleagues assessed the functional scores for these patients preoperatively and at 6-weeks, 6-months, 1-year and 2-years postoperatively.
To ensure mechanical alignment accuracy, researchers used computer navigation in the mechanical alignment group and in the kinematic alignment group. They manufactured patient-specific cutting blocks based on patients’ individual preoperative MRI data.
Oxford Knee Score results
Results of the study showed similar baseline scores and demographics between the two groups.
“For Oxford Knee Score, which was our main outcome, we saw no difference in the clinical outcome score at 2 years between the kinematic and mechanically aligned groups,” Young said in his presentation.
He noted there were no differences between the groups for Knee Society pain score, WOMAC and EuroQol-5D scores, and both groups had similar complication rates.
Although both groups had a similar postoperative hip-knee-ankle axis, results showed the mean varus of the tibial component was 2.1° greater in the kinematic group than in the mechanical alignment group and the mean valgus of the femoral component was 1.4° greater in the kinematic group than in the mechanical alignment group.
The investigators also analyzed the Forgotten Joint Score.
“We were interested in this because it is a score that showed early reduced ceiling effect, so it should be able to tell you the difference between a good knee and a great knee, and just a good knee and a bad knee,” Young said in his presentation. “All patients had similar baseline scores. We saw no difference in the 2-year outcome score for Forgotten Joint Score in either the kinematic [or] mechanically aligned groups.” – by Casey Tingle
- Reference:
- Young SW, et al. No difference in 2-year functional outcomes using kinematic versus mechanical alignment in TKA. Presented at: The Knee Society Specialty Day Meeting; March 5, 2016; Orlando, Fla., USA.
- For more information:
- Simon W. Young, MD, FRACS, can be reached at University of Auckland, Department of Orthopaedic Surgery, North Shore Hospital, 124 Shakespeare Rd., Takapuna Private Bag 93-503, Auckland 0740, New Zealand; email: simon.young@auckland.co.nz.
Disclosure: Young reports research support from Stryker and Vidacare.