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Muscles structure andMuscles structure and function in children with cerebral palsy

Dr Harald BöhmDr Harald Böhm

O th di H it l fOrthopaedic Hospital forChildren, Aschau

Germany

Agendag

• Clinical picture of Cerebral Palsy

T t t f l t t d th• Treatment of muscle contractures and the implication for gait analysis

• Muscle structure and function

• Muscle modelling

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Agendag





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Cerebral Palsy:

Is defined as a nonprogressive insult p gto the immature brain, to areas that affect motor function

Is characterized by motor incoordination that impairs most notably ambulation

2 of 1000 children are affected [1][ ]

[1] Hagberg et al Acta Paediatr. 2001;90:271–277

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Development over time

• Although the brain lesion is static, the effects on the ,musculoskeletal system are not

• Spasticity increases the muscle tone

• Soft tissue contractions develop pover time

• Without therapeutic intervention the level of ambulation cannot b i t i dbe maintained

Equinus gaitq g

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Crouch gait

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Hemiplegia unilateral involvementp g

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muscle atrophy in Hemiplegiap y p gInvolved, dynamic equinus healthy

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Muscle contracture in Hemiplegiap gInvolved side fixed equinus

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SummarySummary

• Cerebral palsy is a brain damage which cannot b d d d lif l thbe cured and needs lifelong therapy

• Muscle tone is increased by spasticityy p y

• Muscles develop contractures (high muscle tiff ) hi h d ROM d t blstiffness) which reduces ROM and notably

affects gait performance

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Agendag





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Equinus gaitq g

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Instrumented gait analysisg y

left right norm

Spatio-temporalparameters

left right norm

step length [cm] 44 52 66

G h i di k it [k /h] 3 6 4 5Geschwindigkeit [km/h] 3,6 4,5

Generation

Power ankle

Generation

Absorption

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Relevance of PlantarflexorsPlantarflexors

• PF generate 40 % of thePF generate 40 % of the total propulsive work Sawicki J Exp Biol 2008

er

Sawicki J. Exp. Biol. 2008

eP

owe

Ank

le

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Conservative therapies

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Orthoses that restrict ankle plantarflexion have good short time effects [1]have good short time effects [1]

8 weeks

[1] Autti-Ramö et al. Literature reviewLiterature review Am. J. Phys. Med. Rehabil.Vol. 85, No. 1

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Equinus: Therapy outcome after 8 weeks wearing orthoses

Passive Dorsiflexion improved from 10° to 20°

Post PreAnkle power at push off PreAnkle power at push-off increased Premature power burstPremature power burst decreased

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Surgical procedures, achilles tendon lengtheningachilles tendon lengthening

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Auswirkungen der Ganganalyse auf OperationsentscheidungenOperationsentscheidungen

52 89 % of descisions based on clinical examination were52 - 89 % of descisions based on clinical examination were changed after gait analysis [1-6]

f th 37 39 % i t ti ll dof those 37 - 39 % interventions were cancelled

28 - 40 % were added

[1] Cook et al. J Pediatr Orthop 2003; 23:292-5 [2] DeLuca et al. J Pediatr Orthop 1997; 17:608-14[3] Fuller et al. Foot & Ankle 2002; 23:738-43 [4] Kay et al. Clin Orthop Relat Res 2000; 217-22[5] Lofterod et al. Acta Orthop 2007; 78:74-80[6] Wren et al. Gait & Posture 2011 in press (randomisiert mit Kontrollgruppe)

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Case examplep

Patient

11 years, bilateral spastic CP, GMFCS II, more involved on the right side, intoeing gait

tt i htpattern right.

OP Indikation:

suprakondylar Derotation right

Clinical examination:

Hip rotation Int/ext (60/0/30) right

Normal tibial torsion

Question Gait analysis:

How much degrees should the hip be rotated?

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Transversal plane j i t t tijoint rotations Hip rotation within

Normal range

Increased tibial torsion rightg

Fot internal progression

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p og ess oright

Descision +Foot correction (Evans, NC-

Arthrodese)Arthrodese)

+Achilles tendon lengthening (Baumann)(Baumann)

+supramalleoläre External rotation Osteotomy (15°)rotation-Osteotomy (15°).

-Hip rotation not required

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SSummary

• Plantarflexors generate about 40% of work for propulsion

• Gait analysis helps to indentify appropriate• Gait analysis helps to indentify appropriate Plantarflexor power

• Gait analysis significanty influences surgical descision making

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Agendag





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Introduction

The muscle is a highly adaptive tissue, it responds p , prapidly to mechanical stress and changes in activity [1].

In hemiplegic patientsIn hemiplegic patients muscle volume was significantly reduced at the g yinvolved leg and biarticular muscles were predominantly ff t d [2]affected [2].

[1] Ponten et al. 2008, J. Neurol Sci 266:52-56 [2] Lampe et al. 2008, Brain Dev 28:500-506

purpose

Differences in the muscle tendon unit structure in the involved leg have been reportedinvolved leg have been reported.

It is unknown whether structural changes in the muscleIt is unknown whether structural changes in the muscle tendon unit are directly related to pathologic function during gait

Hypothesis:Th i l ti b t t i l t tThere is a relation between gastrocnemius muscle structure and ankle power production during gait in children with cerebral palsycerebral palsy.

MethodsPatients: • 12 children and adolescents age 12 (SD=5.2)

years 7 females with cerebral palsy (10 diplegia 2 hemiplegia with involvement in both(10 diplegia, 2 hemiplegia with involvement in both legs)

• GMFCS I+II (able to walk without walking aids)

• Exclusion: ataxia, athetosis, Botulinum-toxin injections and previous casting of the lower limbs within 6 months as well as any surgicalwithin 6 months as well as any surgical procedures.

Gait analysis: • Vicon MX Camera system, 2 forceplates• “Plug-in-Gait” model

Clinical test:Clinical test: • Passive ankle plantar and dorsiflexion (3 times,

knee extended)

• Sonography of gastrocnemius medialis both legs

Methods: sonography

2 Angle of pennation1 Tendon length 2. Angle of pennation3. Fascicle length

1. Tendon length (distance MTJ to heel marker attachment point )marker attachment point )

Method: sonograpy data evaluationg py

Common ROM of all patients was 5 -15° plantarflexionp p

10° plantarflexion was used to determine individual muscle t f th i liparameters from the regression line

Lengths were normalized to shank lengths31

Lengths were normalized to shank lengths.

Methods: gait data evaluation g

1. Push-off energy was determined as the integraldetermined as the integral of the positive ankle power in late stance phase

left side2. Muscle parameters were

correlated to the push offleft sideright side

correlated to the push-off energy for the corresponding legcorresponding leg

Predictors of ankle joint energy at push-offPredictors of ankle joint energy at push off

n=24 (legs) R p

angle of pennation [°] 0.03 0.87

fascicle length [%] 0.26 0.21

tendon length [%] ‐0.58 0.003

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Predictors graphsg p

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Peak ankle dorsiflexion

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Summary results

The stronger legs with greater push-off h d h t t d denergy showed shorter tendons and

longer fascicles

Significant and excellent correlation of t d l th ith th t i h fftendon length with the concentric push-off energy

Comparison to other studies Longer tendon lengths on the weaker legs

Corresponds to shorter muscle belly lengths on the more involved side [1,2]

Shorter fascicle lengths on the weaker legs

Corresponds to [2,3] but not to [1] showing similar fascicle lengthg

[1] Malayia et al. J Electromyography and Kinesiology 2007,17, 657–63[2] Mohagheghi et al. Clin Biomech 2007, 22, 718-24 [3] Williams and Goldspink J Anat. 1978; 127: 459–68.

Discussion weakPA

Longer tendon length (TL) reduces the muscle belly length, and therefore the muscle volume which might explain a lower push-offvolume which might explain a lower push-off force

Shorter fascicle length (FL) reducesShorter fascicle length (FL) reduces contraction speed an therefore push-off power

FL

strongTL

Interpretation: On the weaker side the muscle transformed into a passive force

i i i h l d d h f i l li dtransmitting structure with longer tendon and shorter fascicles aligned along the tendon line of action. This might be useful for passive energy transmission, storage and recoil rather than active force production.

Function of elastic energyFunction of elastic energy ‘storing energy at one stage in the stride and releasing it

h ’ Al d N 1977at another’ Alexander Nature 1977

‘the stored mechanical energy can be used in producing a final velocity greater than that at which the contractilea final velocity greater than that at which the contractile component itself can shorten’ Hill A.V. Proceedings of the Royal Society of London 1950.

Use of elastic energy is important during walking at push-off Ishikawa J. Appl. Physiol. 2005, Hof J. Biomech 1983Biomech. 1983

Use of elastic energy of plantarflexors increases gait effciency about 2.4 times Sawicki J. Exp. Biol. 2009y p

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DiscussionP blProblem: fascicle length was not correlated with ankle push-off energy !

Possible reason: a passive test was used in this study. The tendon is a passive structure and not that much influenced by the muscle activation such as fascicle length or angle of pennation.

Implications for muscle modellingp g

Hill-type Muscle Model [1] Series elastic element length changes the force generation abilities of the contractile

series elastic elementelement [1-3].

contractile elementThe length should be adapted in simulation models of

[1] Hill A V Proc Royal Soc London 1950 137 273-280

in simulation models of cerebral palsy patients

[1] Hill, A.V. Proc Royal Soc London 1950, 137, 273-280.[2] Epstein & Herzog, Theoretical models of skeletal Muscle, Wiley, 1998, pp 80.[3] Böhm et al. 2006. J. Appl. Biomech. 22, 3-13.

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SSummary

• Gastrocnemius tendon length correlates with ankle power production

• Longer tendons and shorter fascicles are• Longer tendons and shorter fascicles are associated with more impairment during gait

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Agendag





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Human Models in diagnosis and gtreatment of CP

1. Inverse dynamics models

2. Kinematic models to determine muscle lengths g

3. Muscle induced acceleration method

4. Muscle driven forward dynamic simulationsimulation

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1. Inverse dynamic models y

45Vicon Plug-in-Gait Model, . Kadaba et al. J Orthop Res 1990: 383-92.

2. Kinematic models to determine muscle lengthslengths

Application: Hamstrings in crouch gait: Allison et al. Gait & posture 2006: 273-81

Further Application: quantifyFurther Application: quantify length changes and effects of body deformities on moment arm (Arnold & Delp J Biomech

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arm (Arnold & Delp J Biomech 2001: 437-47)

2. Muscle induced acceleration methodProcedure: forces are applied to single muscle paths and the resulting accelerations in ankle knee and hip joint are analysed (Zajac & Gordon Exerc Sport Sci Rev 1989: 187-230Exerc Sport Sci Rev 1989: 187 230

Application: Muscles can accelerate joints they do not acce e a e jo s ey do ocross, e.g. Soleus “plantarflexion knee extension” couple Kimmel pGait & Posture 2006 211-21.

47Allison et al. Gait & posture 2006 273-281

4. Muscle driven forward simulation modelsmodels

Procedure: Use mathematical optimization to find a solution for the set of muscles that drives the model to follow a specific gait pattern

Application : simulate surgical procedures. Limitation to overcome is that spastic muscle parameters and activation are not well known

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SSummary

• Kinematic models of muscle length calculations are helpful to support clinical decision making

• Continued work is needed to ensure that the• Continued work is needed to ensure that the results generated by musculoskeletal simulations are accurate and clinically relevantsimulations are accurate and clinically relevant

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Recommended literature

The Identification and Treatment of Gait P bl i C b l P l 2 d Edi iProblems in Cerebral Palsy 2nd Edition 2009. Edited by James R. Gage, Michael H. Schwartz, Steven E. Koop and Tom F. Novacheck, MacKeithPress.

[email protected]/ganglabor

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