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TIBIAL SLOPE AND ACL RUPTURE: MRI ASSESSMENT

163

Two independent reviewers calculated the

angles on each MRI using a modified Hashemi

method which published previously by Lustig

et al.

[5].

According to the procedure described by those

authors, to establish the tibial slope, we used

the proximal tibial anatomic axis (PTAA),

which demonstrates the best correlation with

the tibial shaft anatomic axis (TSAA) [17]. The

PTAA is calculated on the mi-sagittal cut by a

line joining the midpoint between the anterior

and posterior tibial cortices at the level of tibial

tuberosity and at another level 5cm below it.

The angle subtended between the tibial axis to

the horizontal was calculated (Angle TA-H).

The MTP and LTP cuts were used to measure

the medial and lateral tibial slope (MTS, LTS)

respectively.

The PTAA was superimposed on these cuts by

means of TA-H angle. The tibial slope in each

compartment was measured as the angle

between a tangent line connecting the highest

points in the anterior & posterior parts of the

tibial and the perpendicular to the PTTA.

All measurements were positioned as an

overlay and remained in a fixed position on the

complete image series. The meniscal slope

(MS) was defined in the same manner as the

PTS. A tangent to the superior edge of the

meniscosynovial border of the anterior and

posterior meniscus on the sagittal plane was

chosen instead of the tibial plateau cortices.

A posterior inclination to the horizontal was

assigned a positive value, while an anterior

inclination was assigned a negative value. The

measurements were done by two observers and

repeated again after interval of two weeks.

The average PTS and MS angles are reported

as mean angles with standard deviation.The

data was statistically analyzed and the

differences between the bony and soft tissue

slope were compared between the two groups

using independent

t

-test.

RESULTS

The average PTS and MS angles are reported

as mean angles with standard deviation.The

data were initially analyzed for each reviewer

and then the parameters were compared

between the two groups. The maximum and

minimum values for each parameter were also

reported.

Statistical Analysis

The assumption of normality was assessed

with Kolmogorov-Smirnov tests which

revealed that all the measured parameters of

both groups were within normal distribution

(

p

<0.0001).

Inter-observer reliability:

Repeated measures analysis of variance and

95% confidence limits were used to establish

whether the mean slope was altered between

reviewers by means of Intra class Correlation

Coefficient (ICC) and the results showed high

ICC for all the variants which reveal strong

agreement between the observers for all

measurements (table 1).

VARIANT

ICC (95 % CI)

LTS ACL Group

0.9349

MTS ACL Group

0.9148

MMS ACL Group

0.9252

LMS ACL Group

0.9713

LTS CNT Group

0.8841

MTS CNT Group

0.9186

MMS CNT Group

0.8857

LMS CNT Group

0.9159

Table 1:

Inter-observer reliability of the bony and

soft tissue slope for ACL and control (

CNT

) groups.