Kinematic and contact

pressure changes in the ankle

joint with syndesmosis injury:

a cadveric study

Braden J. Criswell, MD, Yannick Goeb, B.S., Anthony

Behn, MS, Loretta Chou, MD, Kenneth Hunt, M.D.

Stanford University Medical Center, Palo Alto,

California

Kinematic and contact pressure changes in

the ankle joint with syndesmosis injury: a

cadaveric study

Braden J. Criswell, MD

My disclosure is in the

Final AOFAS Mobile App.

I have no potential conflicts with

this presentation.

Introduction • Ankle Injuries are among the most common injuries incurred by all levels of

athletic competition.

• Syndesmosis injures have been reported to range from 1% to 24% of ankle

ligamentous injuries1-3

• Ligamentous injuries to the distal tibiofibular syndesmosis are predictive of

long-term ankle dysfunction4

• Mild and moderate syndesmotic injuries can be difficult to stratify

• The impact of syndesmosis injury on the magnitude and distribution of

forces within the ankle joint during athletic activities is unknown

Introduction • The distal tibiofibular syndesmosis is stabilized by five structures:

– The anterior-inferior tibiofibular ligament (AITFL)

– The interosseous ligament (IOL)

– The transverse ligament (TL)

– The interosseous membrane (IOM)

– The posterior-inferior tibiofibular ligament (PITFL).

• The deltoid ligament helps to stabilize the talus in the mortise and indirectly

supports the syndesmosis by preventing lateral translation of the talus

• Depending on the magnitude of the external rotational force encountered,

the syndesmosis and deltoid ligament sequentially fail in a predictive

pattern:

– AITFL

– Anterior Deltoid Ligament

– IOL and TL

– IOM

– PITFL

– Then the full deltoid ligament, which can then lead to dislocation of the

tibiotalar joint

Purpose and Hypothesis • The purpose of this study is to examine ankle joint kinematics and contact

area distribution during axial loading and during axial loading with external

rotation, in a cadaveric model

• Our secondary objective is to measure fibular and talar displacement with

increasing severity of syndesmotic injury with simulated weight-bearing

• Our tertiary objective is to stratify mild (AITFL and/or anterior deltoid),

moderate (IOL, TL, and/or PITFL), and severe (complete deltoid)

syndesmosis injuries in terms of intra-articular force and contact

biomechanics change with increasing injury severity

• We hypothesize that progressive ligamentous syndesmosis injury will

significantly

– Increase fibular and talar rotation

– Increase syndesmotic widening

– Increased tibiotalar contact pressure

– Reduce contact area when undergoing axial loading with external

rotation

Methods • Eight below knee cadaveric specimens were

obtained for testing (Mean Age: 54 ± 4 yrs,

Range: 51 to 60 yrs, all male)

• Figure 1 illustrates the test set-up employed

in the study

• Biomechanical testing was conducted on an

Instron ElectroPuls E10000 (Instron

Corporation, Norwood, MA) with a 10 KN,

100 Nm Dynacell biaxial load cell

• A motion capture system was used to identify

landmark points on the tibia, fibula, and talus

in order to define local bone coordinate

systems

• Intra-articular tibiotalar pressure data was

acquired using an I-SCAN pressure

measurement system (software version 5.23)

with model 5033 sensors (Tekscan Inc,

South Boston, MA)

Figure 1: Photograph of experimental set-

up used for mechanical testing. Motion

trackers were rigidly attached to the tibia,

fibula, and talus. Axial and torsional Loads

were applied to the IM rod inserted into the

proximal tibia.

Methods • The eight below knee cadaveric specimens were tested in the intact state

• The specimens were then tested after sequential sectioning of the

anterior-inferior tibiofibular (AITFL), anterior deltoid (1 cm), interosseous

and transverse (IOL/TL), posterior-inferior tibiofibular (PITFL), and full

deltoid ligaments

• In each condition, the specimen was loaded in axial compression (AL) to

700 N and then externally rotated (ER) to 20 Nm torque.

• Paired t-tests were performed to compare mean contact pressure, peak

pressure, and contact area

• A mixed-effects regression was used to evaluate the effects of each test

condition.

Test Condition Ligaments Sectioned

1 None (Intact State)

2 AITFL

3 AITFL, Ant. Deltoid

4 AITFL, Ant. Deltoid, IOL/TL

5 AITFL, Ant. Deltoid, IOL/TL, PITFL

6 AITFL, Full Deltoid, IOL/TL, PITFL

*Note that Condition 6 was not included in the analysis. See text for details

Table 1: Definitions of the 6 ankle conditions examined in the study.

Results • For each specimen, after complete

deltoid release (i.e., condition 6), the

ankle joint dislocated completely

with even a small amount of external

rotation and thus only conditions 1

through 5 are presented

• During AL + ER testing, both the

fibula and talus rotated significantly

after each ligament sectioning

compared to the intact condition

(Figure 2A)

• After IOL/TL release, a significant

increase in posterior translation of

the fibula was observed (Figure 2B)

• There was no lateral translation of

the fibula relative to the tibia during

AL+ER relative to AL alone for any

condition tested (Figure 2C)

0

5

10

15

20

25

30

Fibula Talus

(Deg

)

External Rotation

1 2 3 4 5

A)

-5

0

5

10

15

Fibula Talus

An

teri

or

- P

oste

rio

r (m

m)

A-P Translation

1 2 3 4 5

B)

-1

0

1

2

3

4

Fibula Talus

Late

ral

- M

ed

ial (m

m)

M-L Translation

1 2 3 4 5

C)

Figure 2: (A) Rotation about the long axis and (B,C) axial plane translations

of fibula and talus with respect to tibia during external rotation to 20 Nm with a

constant axial load of 700 N for five ankle conditions. (Mean ± SD)

Results • Mean tibiotalar contact

pressure increased

significantly after IOL/TL

release, and the center of

pressure shifted

posterolaterally, relative

to more stable conditions,

after IOL/TL release

(Figure 3)

• During AL+ER, the center

of pressure (COP) shifted

anteriorly and medially on

the talus (Figure 5)

• The relative location of

the center and pressure

was posterior and slightly

lateral in conditions 4 and

5, after the IOL/IOM and

PITFL were sectioned,

respectively

Figure 3: Representative intra-articular tibiotalar pressure

distribution during axial loading only and combined axial loading with

external rotation. Images recorded during testing of condition 3.

Figure 5: (A) M-L and (B) A-P COP translations recorded by

pressure sensors during external rotation to 20 Nm with a constant

axial load of 700 N for five ankle conditions. (Mean ± SD)

0

2

4

6

8

Med

ial (m

m)

M-L COP Translation

1 2 3 4 5

A

-4

-2

0

2

4

6

8

Po

ste

rio

r -

A

nte

rio

r (

mm

)

A-P COP Translation

1 2 3 4 5

B

Results • There were significant increases in mean contact pressure and peak

pressure along with a reduction in contact area with AL + ER compared

to AL alone for all 6 conditions (Figure 4)

0

1

2

3

4

5

6

7

8

AL Only AL + ER

(MP

a)

Mean Contact Pressure

1 2 3 4 5

A)

0

5

10

15

20

25

AL Only AL + ER

(MP

a)

Peak Pressure

1 2 3 4 5

B)

0

100

200

300

400

500

600

AL Only AL + ER

(mm

2)

Contact Area

1 2 3 4 5

C)

Figure 4: (A) Mean contact pressure, (B) peak pressure, and (C)

contact area recorded by pressure sensors during axial loading

only and combined axial loading with 20 Nm external Rotation for

five ankle conditions. (Mean ± SD)

Conclusion • Our study characterizes the magnitude and distribution of forces within the

ankle joint during axial loading and external rotation in a cadaveric model

of successive syndesmosis injuries

• We show:

– A significant reduction in contact area and a significant increase in mean and peak

pressure during axial loading and external rotation relative to axial loading alone in all

testing conditions

– Significant increases in tibiotalar contact pressures occur when external rotation stresses

are added to axial loading

– Moderate and severe injuries are associated with a significant increase in mean contact

pressure combined with a shift in the center of pressure, and rotation of the fibula and

talus

• Considerable changes in ankle joint kinematics and contact mechanics

may explain why athletes with even moderate syndesmosis injuries take

longer to heal and are more likely to develop long term dysfunction and

potentially arthritic changes after these injuries

• This study suggests the importance of limiting rotational forces in the

rehabilitation of moderate and severe syndesmosis injuries

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