Related Experiment Video
Updated: Jun 16, 2026
In Vitro Application of a Wireless Sensor in Flexion-Extension Gap Balance of Unicompartmental Knee Arthroplasty
Published on: May 5, 2023
Computer-assisted navigation for the assessment of fixed flexion in knee arthroplasty
Price A M Gallie1, Edward T Davis, Kelly Macgroarty
1Department of Orthopaedic Surgery, Gold Coast Hospital, Queensland, Australia.
Background:
Correction of a fixed flexion deformity is an important goal when performing total knee arthroplasty. The purpose of this study was to assess the accuracy of clinical assessment compared with imageless computer navigation in determining the degree of fixed flexion.
Methods:
We performed navigation anatomy registration using 14 cadaver knees.The knees were held in various degrees of flexion with 2 crossed pins. The degree of flexion was first recorded on the computer and then on lateral radiographs. The cadaver knees were draped as they would be for a total knee arthroplasty, and 9 examiners were asked to clinically assess by visual observation the amount of fixed flexion.Three examiners repeated the process 1 week later.
Results:
The mean error from the radiographs in the navigation group was 2.18 degrees (95% confidence interval [CI] 1.23 degrees -3.01 degrees) compared with 5.57 degrees (95% CI 4.86 degrees -6.29 degrees) in the observer group. The navigation was more consistent, with a range of error of -5 degrees to +5.5 degrees compared with -18.5 degrees to +17.5 degrees in the observer group. The observers tended to underestimate the amount of knee flexion (median error -4 degrees), whereas the navigation group was more evenly distributed (median error 0). The highest concordance coefficient was found between navigation and radiography (0.96). The concordance coefficient was 0.88 for the 3 surgeons who repeated the measurements 1 week later (mean error 3.5 degrees , range 15 degrees ).
Conclusion:
The use of computer navigation appears to be a more accurate method for assessing the degree of knee flexion, with a reduced range of error compared with clinical assessment. The use of computer-assisted surgery may therefore provide surgeons with the information required to more consistently restore full extension during total knee arthroplasty.
Insights
Computer navigation accurately measures knee flexion, outperforming clinical assessment in total knee arthroplasty. This technology offers improved consistency for restoring full knee extension.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
- Surgical Navigation Systems
Background:
- Fixed flexion deformity correction is crucial in total knee arthroplasty (TKA).
- Accurate assessment of knee flexion is vital for successful TKA outcomes.
Purpose of the Study:
- To compare the accuracy of clinical assessment versus imageless computer navigation.
- To determine the degree of fixed knee flexion in cadaveric models.
Main Methods:
- 14 cadaver knees were used for navigation anatomy registration.
- Knees were positioned in varying flexion degrees, measured by computer navigation and lateral radiographs.
- Nine examiners visually assessed fixed flexion, with three repeating measurements for reliability.
Main Results:
- Computer navigation showed a mean error of 2.18 degrees, significantly lower than clinical assessment (5.57 degrees).
- Navigation offered a narrower error range (-5 to +5.5 degrees) compared to observers (-18.5 to +17.5 degrees).
- Navigation demonstrated higher consistency, with a concordance coefficient of 0.96 with radiography.
Conclusions:
- Imageless computer navigation is more accurate for assessing knee flexion than clinical evaluation.
- Computer navigation reduces the range of error, aiding consistent restoration of full knee extension in TKA.
- This technology can enhance surgical precision and patient outcomes in total knee arthroplasty.