Upload
duongngoc
View
216
Download
0
Embed Size (px)
Citation preview
1
1© Uwe Kersting, 2011
SPECIFIC ACUTE INJURIES:
THE ANKLE
Uwe Kersting – MiniModule 05 – 2011 Idræt – Biomekanik 2
2© Uwe Kersting, 2011
Objectives• Review anatomy and know about the static and dynamic ‘organisation’ of the foot skeleton
• Be able to list major ligaments of the ankle joint and foot complex; describe their dynamic function
• Know about the main mechanisms of ankle injuries –what is know and what is not known
• Learn about biomechanical approach to understand injury mechanism in ‘LPT’ fractures (snowboarding)
• Learn about the effect of slipping on ankle joint loading
2
3© Uwe Kersting, 2011
Contents1. Foot and ankle anatomy and biomechanics:
the framework
2. Injury mechanisms and risk factors: the general idea but there are exceptions
3. Biomechanical research: change in direction tasks
4. Biomechanical research: snow boarding and cutting movements
5. Prevention options
6. Summary
4© Uwe Kersting, 2011
Cross section of a Foot
3
5© Uwe Kersting, 2011
Function of foot and ankle
• Foot skeleton: 26 bones + 2 sesamoids� complex structure
• 33 joints with varying range of motion and degrees of freedom, 112 ligaments
• Stability
– Ligaments and Tendons
– Muscles
• Fat pad
– impact absorption
6© Uwe Kersting, 2011
Joints of the foot- reduced view = main joints
(?)
MP
TM
TN ST
TC
4
7© Uwe Kersting, 2011
Name ligamentous structures & describe their function
1___________
2___________
3___________
Medial view
8© Uwe Kersting, 2011
Name the ligamentous structures and list their function
4____________
5____________
6____________
7______________
Lateral view
5
9© Uwe Kersting, 2011
Anatomical axes
10© Uwe Kersting, 2011
Ankle joint function/functional axesSubtalar joint = oblique hinge joint
(inversion vs. pronation)
6
11© Uwe Kersting, 2011
Foot Segments & major axes
Lisfranck and Chopart joint lines: relatively small ranges of motion
(Kapandji, 1992)
Metatarso-phalangeal joints = hinge joints
12© Uwe Kersting, 2011
7
13© Uwe Kersting, 2011
Limitied
’access’ by
video based
measurement
techniques
14© Uwe Kersting, 2011
Arches of the foot
Longitudinal archWindlass mechanism:Stiffening of the foot during TO
8
15© Uwe Kersting, 2011
Contribution of foot structures to mechanical stiffness
Cadaver experimentSuccessive removal of tissue
a,b - skinc - plantar aponeurosisd - lig. plant. longume - musclesf - ligaments
(Ker et al., 1987)
Load-Displacement Graph
16© Uwe Kersting, 2011
Foot Type/Function Assessment
Qualitative assessment– Visual inspection of foot
• Changes with load bearing
• Walking
– Manual ROM tests
Quantitative assessments– Ink pad + clinical (FPI)
– Pressure platform
– Pressure Insole
– 2D video
– Gait analysis (3D)
9
17© Uwe Kersting, 2011
Foot posture and injury (?)• From FPI paper (Nielsen et al., 2009):
- Leg pain & navicular drop in female sports population (Reinking, 2006)
- Pronated feet � medial tibial stress syndrome after intense training (Yates & White,
2004)
- No relationship of foot posture and various overuse syndromes at knee and shin (Kaufman et al., 1999)
� Dynamic measures might be better suited...
18© Uwe Kersting, 2011
Pressure Distribution Measurement
Dynamic assessment of foot function:- Pressure Platform
10
19© Uwe Kersting, 2011
Pressure distribution measurement
Dynamic assessment of foot function:- Pressure sensor insoles
HLHL
HMHM
MLML
MMMM
M45M45
M23M23
M1M1
TOTO
HAHA
HLHL
HMHM
MLML
MMMM
M45M45
M23M23
M1M1
TOTO
HAHA
20© Uwe Kersting, 2011
Pressure Distribution Changes
Standing
Walking
Does the foot
really have
two arches?
11
21© Uwe Kersting, 2011
So far ...• Static measures do not relate well to injury occurrence
• 3 point support of the foot seems a ’questionable’ concept
• Anatomical setup suggests dynamic function –which requires dynamic measures- Windlass mechanism may be important ...
22© Uwe Kersting, 2011
Foot & ankle injuries
12
23© Uwe Kersting, 2011
Frequency of ankle injury• Netball 45% - 54%
• Basketball 45%
• Soccer 26%
• Gymnastics 23%
• Rugby 12-16%
14% of all sport injuries>>20% in team sports and track and field
current review: Fong et al. (2007)
24© Uwe Kersting, 2011
Ankle sprain
• Overstretching or tear of one or more ankle ligaments
• The ankle is the most commonly injured body region in sport
• Sprains to the lateral ankle make up 85% of all ankle sprains– Medial ankle sprains are rare
13
25© Uwe Kersting, 2011
Cost of Ankle Sprain Injury
• 2 million people each year in USA
• $318 - $914 per sprain
• ACC – NZ (1999)
• 3,657 new claims $5,363,000
• 2,684 on-going claims $9,947,000
• $147 and $370 per person35 000 per year in Denmark
� 20 – 40% develop chronically
instable ankle
� 33% develop long-term
complications like OA
(Larsen et al., 1999)
26© Uwe Kersting, 2011
Mechanism (?) & Risk factors
Mechanism: Forced plantarflexion and inversion of ankle
Situations: Landing on uneven surface or players footHigh velocity stops
Risk Factors:• Previous injury• Cutting movements• Inappropriate / worn footwear• Surface• Fatigue• Proprioception• Strength, ....
Commonly described injury mechanism:
Combined inversion and plantarflexion of the foot
14
27© Uwe Kersting, 2011
Risk factorsIntrinsic:
• Proprioception - repositioning- reflex latencies- balance
• Strength - calf, in- and everters
• Joint laxity �very general and inconsistent!
Largest risk factor = previous injury
28© Uwe Kersting, 2011
Video evidence
16
31© Uwe Kersting, 2011
ComparisonGrey: normal __ injury trial
Rather dorsiflexion than plantarflexion involved (?)
32© Uwe Kersting, 2011
Preliminary summary• The foot is complex, made up by 26 bones stabilised by a system of ligaments and muscles.
• The ankle joint combines two hinge joints –joint axes not aligned with anatomical planes of movement.
• The ankle joint is one of the most injured joints in sports. Most commonly the lateral ligaments get strained – mechanism is not quite clear.
• Question: How can biomechanical research help in injury prevention?
17
33© Uwe Kersting, 2011
Introduction
• Combined plantar-flexion & inversion �supination torque exceeds structural limits of ankle joint complex
Factors?
• Passive stiffness of ankle joint
• Muscle activation pre and during contact � reflexes
• Foot position at TD (Wright et al., 2000)
34© Uwe Kersting, 2011
Research using a simple model
• Combined plantar-flexion & inversion �supination torque exceeds structural limits of ankle joint complex
Factors?
• Passive stiffness of ankle joint
• Muscle activation pre and during contact � reflexes
• Foot position at TD (Wright et al., 2000)
• Joint loading in early contact phase
18
35© Uwe Kersting, 2011
PURPOSE
Validation of centre of pressure calculations in
a force platform actuator
Effect of small slip episodes during early ground contact in turning movements
• CoP location during slips?
• Effect on external loading � GRF?
• Effect on joint kinematics and joint loading � net joint torques?
36© Uwe Kersting, 2011
Methods• Subjects
• Perturbator:
4 hydraulic actuators
AMTI force plate on
top
reaction time: 13 – 15
ms
(Doornik & Sinkjær,
NBM [kg]
Height [m]
Age [y]
Shoe Size
current train [h/w]
previous train [h/w]
Mean 13 73.3 1.75 32 41.2 3.5 6.4
SD 12.5 0.09 8.3 2.7 2.5 3.1
19
37© Uwe Kersting, 2011
Data Collection
• Validation of inertia compensation: simultaneous recording of pressure distribution (RS Scan 1m plate, 250 Hz; Force plate, 1000 Hz)
• Subject trials:
�GRF (AMTI, 2400 Hz)
�3D kinematics (240 Hz, Qualisys pro reflex);
corrected for inertia effects of
moving platform (MatLab 7.4, filtered at 70 Hz)
Frame Cover
FP
PP
38© Uwe Kersting, 2011
Data Analysis
• 10 marker leg & foot model (Qualisys)
• 3D rigid body model – 2 segments, foot & leg (AnyBody modelling environment)
• Min & Max in 3 phases(Min1, Max1, ...; Gehring, 2007)
• Statistics: repeated measures ANOVA; post hoc Newman Keuls & correlation coefficients
1 32
20
39© Uwe Kersting, 2011
Experimental procedure• Warm up – instructions & no platform movement
• Familiarization – incl. platform movement
• Measurement - 40 valid trials, 8 per condition
– foot on platform, no double contact
– random application of platform movements:
still (ST)
3 cm/242 ms (SS) 3 cm/121 ms (SM)
6 cm/242 ms (LM) 6 cm/121 ms (LF)
40© Uwe Kersting, 2011
Ground Reaction Forces
vertical GRF decreases with increasing slip amplitude and velocity (15%)
horizontal GRF decreases ’similarly’ but minimum amplitude at LM slip (16%)
Vertical GRF - Max1
10
15
20
25
30
35
ST SS SM LM LF
Forcel [N/kg]
*ns
Horizontal GRF - Min1
-25
-20
-15
-10
-5
0
ST SS SM LM LF
Force [N/kg]
*
21
41© Uwe Kersting, 2011
Horizontal Impulse
-4.5
-4.0
-3.5
-3.0
-2.5
-2.0
ST SS SM LM LF
Impulse [Nm/kg]
Contact Time & Impulse
contact time decreases with minimum at LM (10%)
Contact time
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
ST SS SM LM LF
t [s]
*
only LM shows reduced magnitude (6%)
*
42© Uwe Kersting, 2011
Joint Torque
significant redu-ction for SM and LF (~20%)
significant increase
in magnitude for
early contact and
push-off;
LF (16% / 33%)
Ankle Inversion Torque - Max1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
ST SS SM LM LF
T [Nm/kg]
**
Dorsal Extension Torque - Min3
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
ST SS SM LM LF
T [Nm/kg]
*
*-0.2 0 0.2 0.4 0.6 0.8 1 1.2
-40
-20
0
20
40
60
80
100
-0.2 0 0.2 0.4 0.6 0.8 1 1.2-40
-20
0
20
40
60
80
100
t/tcontact []
T
[Nm]
Example – Inversion
ST
SM
LF
22
43© Uwe Kersting, 2011
From this:• New method; suited to comprehensively assess loading under controlled slipping conditions
• Slipping reduces GRF maxima and changes alignment of force vector
• Horizontal impulse and joint torque indicate a 3cm slip over 121 ms as safest and most efficient – aligned with perception
• Further research perspectives: – muscle contributions - slip at different timesduring contact – variation of foot placement –ground work for product development
44© Uwe Kersting, 2011
Subtalar joint torque
0 10 20 30 40 50 60 70 80 90 100-40
-35
-30
-25
-20
-15
-10
-5
0
T [Nm]
TD TO
t [% tcontact]
example
23
45© Uwe Kersting, 2011
Using anatomical joint axes
• The ankle joint experiences eversion torque during the whole contact
• This torque is accounted for by triceps surae contraction
• Therefore the ankle joint appears safe during planned turning tasks
• What happens when it goes wrong?
46© Uwe Kersting, 2011
Example from the Biomechanics Lab: Snowboarding Ankle Injuries
• Significant subset of injuries in the snowboarder (Assenmacher & Hunter 2002)
• 15% of all Injuries
– Fractures a major component (Kirkpatrick et al, 1998)
• Soft shell boots allow greater ankle ROM
• Lead foot absorbs majority of impact & is most frequently injured
(Frymoyer et al, 1982; Young & Niedfeldt, 1999)
• Snowboard specific injury →→→→ fracture of lateral process of talus (LPT)
24
47© Uwe Kersting, 2011
The Snowboarders Fracture
• Fracture to the lateral process of the talus (LPT)
• 34% of all snowboarding ankle fractures– (Kirkpatrick et al, 1998)
• Unique to snowboarders
• Often misdiagnosed - ongoing pain and disability
• Often involves articular surface of subtalar joint
48© Uwe Kersting, 2011
Classification of Injury
Three types of fracture; depending on severity
Type 1 Type 2 Type 3
25
49© Uwe Kersting, 2011
Mechanism of InjuryHigh impact injury
–Landing of aerial maneuvers thought to be a major cause (Bladin & McCrory, 1995; Boon et al, 1999)
Two potential injury causing movement patterns
• External tibial rotation + axial load to inverted, dorsiflexed ankle
Boon et al. (2001)
• Forced eversion of loaded, dorsiflexed ankle
Funk et al. (2003)
50© Uwe Kersting, 2011
LPT Fracture Research• Mechanism of injury is understood (mostly)
• Lack of research evaluating the relationship between snowboarding equipment and the fracture mechanism
• Binding alignment determined solely by personal preference
• How does stance (binding arrangement) affect LPT fracture risk?
26
51© Uwe Kersting, 2011
Methodology• 8 subjects, mean age 25 yrs
– - All experienced snowboarders
• Simulated landing task
• 3D video analysis
• Joint force / torque calculations
• Three ‘stance’ conditions
– - Standard (ST) � 15° front foot, 0° rear foot
– - Duck Stance (DU) � 24° front foot, -24° rear foot
– - Duck Stance with forward lean (DF) � same as DU but with addition of ‘forward lean’ on binding Achilles support.
52© Uwe Kersting, 2011
Results
• No difference found in ankle dorsiflexion or inversion/eversion movement between conditions
• Increased lateral shear forces and external tibial rotation seen with standard stance
– possibly due to knee/shank movement over the foot
– Increased injury risk?
• No differences seen between the ‘duck’ conditions
27
53© Uwe Kersting, 2011
Future Directions
Field testing – the only possible approach (?)
– Quantification of lower body motion and forces involved during real jump landings
54© Uwe Kersting, 2011
28
55© Uwe Kersting, 2011
Short review on interventions
• External stabilisers work for ankle injury prevention
• They are more effective for chronically instable or previously injured ankles
• Wobble board training and other ‘proprioceptive’ training was shown to reduce the risk for injury/reinjury
56© Uwe Kersting, 2011
Summary• Ankle injuries can be considered as one of the most common sports injuries
• Acute injuries in most cases affect ligaments
• Interventions: Training & Braces/Tape do work
• Injury & intervention mechanisms are not fully understood
• In snowboarding a special form/mechanism of ankle injury has been identified