Mechanical axis and TKA survival (Parratte)

Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern, cemented total knee replacements.

Parratte S, Pagnano MW, Trousdale RT, et al. The Journal of bone and joint surgery. American volume 2010 · PMID 20844155 · doi:10.2106/jbjs.i.01398

Question

Does restoring a neutral mechanical axis (within 0 plus or minus 3 degrees) improve long-term survival of cemented TKA?

Design

Retrospective cohort study from the Mayo Clinic with 15-year follow-up.

Patients

Patients with modern cemented primary TKA and postoperative long-leg alignment measurements.

Intervention

Postoperative mechanical axis within 0 plus or minus 3 degrees

Comparison

Mechanical axis outside that range (outliers)

Primary outcome

Implant survival free of revision at 15 years

Key result

There was no significant difference in 15-year survival between knees aligned within the neutral range and outliers.

Limitations

Retrospective design, radiographic measurement error and a single-centre cohort with modern implants that may tolerate malalignment.

Impact on practice

Questioned the dogma that neutral mechanical alignment is essential for survival and opened the door to alternative alignment philosophies.