Limb alignment in computer-assisted minimally-invasive unicompartmental knee replacement

J Bone Joint Surg Br. 2006 Jan;88(1):44-8. doi: 10.1302/0301-620X.88B1.16266.


Twenty patients underwent simultaneous bilateral medial unicompartmental knee arthroplasty. Pre-operative hip-knee-ankle alignment and valgus stress radiographs were used to plan the desired post-operative alignment of the limb in accordance with established principles for unicompartmental arthroplasty. In each patient the planned alignment was the same for both knees. Overall, the mean planned post-operative alignment was to 2.3 degrees of varus (0 degrees to 5 degrees ). The side and starting order of surgery were randomised, using conventional instrumentation for one knee and computer-assisted surgery for the opposite side. The mean variation between the pre-operative plan and the achieved correction in the navigated and the non-navigated limb was 0.9 degrees (sd 1.1; 0 degrees to 4 degrees ) and 2.8 degrees (sd 1.4; 1 degrees to 7 degrees ), respectively. Using the Wilcoxon signed rank test, we found the difference in variation statistically significant (p < 0.001). Assessment of lower limb alignment in the non-navigated group revealed that 12 (60%) were within +/- 2 degrees of the pre-operative plan, compared to 17 (87%) of the navigated cases.Computer-assisted surgery significantly improves the post-operative alignment of medial unicompartmental knee arthroplasty compared to conventional techniques in patients undergoing bilateral simultaneous arthroplasty. Improved alignment after arthroplasty is associated with better function and increased longevity.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Aged
  • Ankle Joint / diagnostic imaging
  • Ankle Joint / pathology
  • Arthroplasty, Replacement, Knee / methods*
  • Bone Malalignment / diagnostic imaging
  • Bone Malalignment / prevention & control*
  • Female
  • Hip Joint / diagnostic imaging
  • Hip Joint / pathology
  • Humans
  • Knee Joint / diagnostic imaging
  • Knee Joint / pathology
  • Male
  • Middle Aged
  • Osteoarthritis, Knee / diagnostic imaging
  • Osteoarthritis, Knee / pathology
  • Preoperative Care / methods
  • Prospective Studies
  • Radiography
  • Surgery, Computer-Assisted / methods*
  • Treatment Outcome