Non-invasive computer-assisted measurement of knee alignment

Jon V Clarke, Philip E Riches, Frederic Picard, Angela H Deakin

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The quantification of knee alignment is a routine part of orthopaedic practice and is important for monitoring disease progression, planning interventional strategies, and follow-up of patients. Currently available technologies such as radiographic measurements have a number of drawbacks. The aim of this study was to validate a potentially improved technique for measuring knee alignment under different conditions. An image-free navigation system was adapted for non-invasive use through the development of external infrared tracker mountings. Stability was assessed by comparing the variance (F-test) of repeated mechanical femoro-tibial (MFT) angle measurements for a volunteer and a leg model. MFT angles were then measured supine, standing and with varus-valgus stress in asymptomatic volunteers who each underwent two separate registrations and repeated measurements for each condition. The mean difference and 95% limits of agreement were used to assess intra-registration and inter-registration repeatability. For multiple registrations the range of measurements for the external mountings was 1° larger than for the rigid model with statistically similar variance (p=0.34). Thirty volunteers were assessed (19 males, 11 females) with a mean age of 41 years (range: 20-65) and a mean BMI of 26 (range: 19-34). For intra-registration repeatability, consecutive coronal alignment readings agreed to almost ±1°, with up to ±0.5° loss of repeatability for coronal alignment measured before and after stress maneuvers, and a ±0.2° loss following stance trials. Sagittal alignment measurements were less repeatable overall by an approximate factor of two. Inter-registration agreement limits for coronal and sagittal supine MFT angles were ±1.6° and ±2.3°, respectively. Varus and valgus stress measurements agreed to within ±1.3° and ±1.1°, respectively. Agreement limits for standing MFT angles were ±2.9° (coronal) and ±5.0° (sagittal), which may have reflected a variation in stance between measurements. The system provided repeatable, real-time measurements of coronal and sagittal knee alignment under a number of dynamic, real-time conditions, offering a potential alternative to radiographs.

LanguageEnglish
Pages29-39
Number of pages11
JournalComputer Aided Surgery
Volume17
Issue number1
Early online date30 Nov 2011
DOIs
Publication statusPublished - 2012

Fingerprint

Volunteers
Knee
Mountings
Orthopedics
Disease Progression
Reading
Leg
Technology
Stress measurement
Angle measurement
Navigation systems
Time measurement
Infrared radiation
Planning
Monitoring

Keywords

  • knee alignment
  • non-invasive
  • infrared tracking
  • femoral-tibial angle
  • computer-assisted measurement

Cite this

Clarke, Jon V ; Riches, Philip E ; Picard, Frederic ; Deakin, Angela H. / Non-invasive computer-assisted measurement of knee alignment. In: Computer Aided Surgery. 2012 ; Vol. 17, No. 1. pp. 29-39.
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Non-invasive computer-assisted measurement of knee alignment. / Clarke, Jon V; Riches, Philip E; Picard, Frederic; Deakin, Angela H.

In: Computer Aided Surgery, Vol. 17, No. 1, 2012, p. 29-39.

Research output: Contribution to journalArticle

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