Evaluation of different methods for measuring lateral tibial slope using magnetic resonance imaging.
BACKGROUND
Since lateral tibial slope (LTS) affects the amount of anterior tibial translation and anterior cruciate ligament (ACL) strain during a dynamic maneuver, accurate measurements of LTS may be beneficial in screening people at a higher risk for ACL injury. Methods for measuring LTS on magnetic resonance imaging (MRI) scans of the proximal tibia include the midpoint and circle methods. No current studies have validated different LTS measurement methods using a proximal tibia MRI scan.


OBJECTIVE
We tested the null hypotheses that (1) LTS measurements were independent of the length of tibia imaged using the midpoint method, and (2) LTS measurements calculated from different methods (midpoint, circle, and full tibia) would not differ significantly.


METHODS
Controlled laboratory study.


METHODS
Blinded observers measured LTS from 3-tesla, 3-dimensional MRIs from 40 size-matched donors according to 1 circle method and 3 midpoint methods. Outcomes were then compared with the full-tibial anatomic axis (line connecting the center of 2 circles fit within the proximal and distal tibia) in 11 donors. Bonferroni-corrected paired t tests (significance, P < .005) were used to compare the 5 methods.


RESULTS
The circle and full-tibia methods had the lowest interobserver and intraobserver variability, whereas the midpoint method with 10-cm tibia was the most variable. The midpoint method with 10-cm and 15-cm proximal tibia closely resembled LTS measurements with the full-tibial anatomic axis. The circle method, although repeatable, provided smaller numerical LTS measurements than the full-tibia and midpoint methods.


CONCLUSIONS
Although LTS measurements using the midpoint method can resemble measurements made using the full tibia, the reliability of the midpoint method depends on the length of proximal tibia used. The circle method may be the preferred method for future studies since it was the most repeatable method and is independent of proximal tibial length.


CONCLUSIONS
LTS measurements vary depending on the method used.
Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60611, USA. dlipps@ric.org
David B
DB
Lipps
Annie M
AM
Wilson
James A
JA
Ashton-Miller
Edward M
EM
Wojtys
D000368:Aged; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013977:Tibia / Q000033:anatomy & histology*