PATHOETIOLOGY OFPATHOETIOLOGY OFLATERAL ANKLE INSTABILITIESLATERAL ANKLE INSTABILITIES

Jay Hertel, PhD, ATCPennsylvania State University

Eastern Athletic Trainers’ Association Meeting

January 3, 2003

SPECIAL ISSUE ON ANKLE

INSTABILITY

2002, vol. 37(4)

OUTLINEOUTLINE

• Acute Ankle Sprains

• Chronic Ankle Instability• Mechanical Instability• Functional Instability

PREDISPOSITIONS TO PREDISPOSITIONS TO INITIAL ANKLE SPRAININITIAL ANKLE SPRAIN

Poor postural control (Tropp 1984, McGuine 2000)

Altered strength ratios (Baumhauer 1995)

Poor proprioception (Payne 1997)

Increased tibial varum (Beynnon, 2001)

Non-pathological talar tilt (Beynnon, 2001)

MECHANISM OF ACUTE MECHANISM OF ACUTE ANKLE SPRAINANKLE SPRAIN

Supination of the rearfoot coupled with external rotation of the lower leg– Plantar flexion– Inversion– Internal Rotation

More plantar flexion increases likelihood of a sprain (Wright et al, 2000)

MECHANISM OF INJURYMECHANISM OF INJURY

CONSEQUENCES OF AN CONSEQUENCES OF AN ACUTE ANKLE SPRAINACUTE ANKLE SPRAIN

ATFL Injury

CFL Injury

“Rotational Instability”

Subtalar Instability

PATHOMECHANICAL PATHOMECHANICAL MODEL OF ACUTE SPRAINMODEL OF ACUTE SPRAIN

Vertical ground reaction force medial to the subtalar axis of rotation will cause a “supination moment” (Fuller, 1999)

If supination moment exceeds pronation moment, potential for injury exists

SUBTALAR AXIS OF ROTATION & VERTICAL SUBTALAR AXIS OF ROTATION & VERTICAL GROUND REACTION FORCE RELATIONSHIPGROUND REACTION FORCE RELATIONSHIP

THE CRITICAL PERIODS:THE CRITICAL PERIODS:Terminal Swing & Initial ContactTerminal Swing & Initial Contact

Position of the foot at initial contact dictates ground reaction forcesIf the foot is inverted too far at initial contact, injury mechanism is inevitable

THE CRITICAL PERIODS:THE CRITICAL PERIODS:Terminal Swing & Initial ContactTerminal Swing & Initial Contact

In full weight bearing, the stability of the talus is due to the articular surfaces, not ligaments (Stormant et al, 1985)

Cadaver experiments have shown that the talus is stable during full weight bearing even in the presence of bimalleolar fracture (Michelson et al, 2002)

Can the Can the peroneals peroneals respond quickly respond quickly enough to prevent injury?enough to prevent injury?

54 msec needed for reaction to inversion perturbation

Additional 72 msec needed to generate force in tendon

Total time to maximal inversion may be <45 msec

Preparatory activity of the peroneals is essential if hyperinversion is to be prevented

Konradsen et al, 1997

CHRONIC ANKLE INSTABILITY: CHRONIC ANKLE INSTABILITY: TRADITIONAL PARADIGMTRADITIONAL PARADIGM

Mechanical Instability– Pathological Laxity

Functional Instability– Proprioceptive and

neuromuscular deficits

ChronicAnkle Instability

MechanicalInsufficiencies

Functional Insufficiencies

Pathological LaxityArthro-

kinematicRestrictions

SynovialChanges

DegenerativeChanges

ImpairedProprioception Impaired

NeuromuscularControl

StrengthDeficits

ImpairedPosturalControl

RecurrentAnkle Spain

TALOCRURAL TALOCRURAL LAXITYLAXITY

Talar Tilt

Anterior Drawer

Rotational Instability

SUBTALAR SUBTALAR LAXITYLAXITY

Anterior Drawer

Subtalar Tilt

Rotational Instability

Approximately 66% of those with talocrural instability also have subtalar instability (Hertel et al, 1999)

MECHANICAL INSUFFIENCIES: MECHANICAL INSUFFIENCIES: ARTHROKINEMATIC IMPAIRMENTSARTHROKINEMATIC IMPAIRMENTS

Hypomobility

Inferior Tibiofibular Joint Positional Fault

Limited Posterior Talar Glide

POSITIONAL FAULT OF POSITIONAL FAULT OF INFERIOR TIBINFERIOR TIB--FIB JOINTFIB JOINT

Distal fibula is “stuck” anteriorly and inferiorly (Mulligan)

Preliminary evidence supports this phenomenon in some patients with chronic instability (Kavanagh, 1999)

RESTRICTED POSTERIOR RESTRICTED POSTERIOR TALAR GLIDETALAR GLIDE

Posterior talar glide restricted 12 weeks after ankle sprain (Denegar et al, 2002)

Patients treated with posteriortalar mobilization regaineddorsiflexion ROM quicker (Greene et al, 2001)

Sinus Tarsi Syndrome– Subtalar Joint

Anterolateral Impingement Syndrome– Talocrural Joint

Normal Sinus Tarsi

Sinus Tarsi Syndrome

MECHANICAL MECHANICAL INSUFFIENCIES: INSUFFIENCIES: SYNOVIAL CHANGESSYNOVIAL CHANGES

MECHANICAL INSUFFIENCIES: MECHANICAL INSUFFIENCIES: DEGENERATIVE CHANGESDEGENERATIVE CHANGES

Patients undergoing surgical stabilization of the ankle are 3.3 times as likely to have osteophytes & loose bodies than controls (Scranton et al, 2000)

More osteophytes and subchondral sclerosis in patients with history of recurrent ankle sprains (Gross & Marti, 1999)

ChronicAnkle Instability

MechanicalInsufficiencies

Functional Insufficiencies

Pathological LaxityArthro-

kinematicRestrictions

SynovialChanges

DegenerativeChanges

ImpairedProprioception Impaired

NeuromuscularControl

StrengthDeficits

ImpairedPosturalControl

RecurrentAnkle Spain

CutaneousReceptors

Articular Receptors CNS Extrafusal

MuscleFibers

Gammamotor

neurons

IntrafusalMuscleFibers

PROPRIOCEPTION & NEUROMUSCULARCONTROL MODEL

DY

SFUN

CTIO

N

DYSFUNCTION

DYSFUNCTION

Alphamotor

neurons

Tendon & Muscle

Receptors

FUNCTIONAL INSUFFIENCIES: FUNCTIONAL INSUFFIENCIES: IMPAIRED PROPRIOCEPTIONIMPAIRED PROPRIOCEPTION

Impaired kinesthesia

Impaired joint position sense

Muscle spindles of peroneals may be key

FUNCTIONAL INSUFFIENCIES: FUNCTIONAL INSUFFIENCIES: IMPAIRED NEUROMUSCULAR IMPAIRED NEUROMUSCULAR

CONTROLCONTROLDelayed firing of theperoneals

Impaired activity of proximal muscles?

Unilateral versus bilateral deficits

CutaneousReceptors

Articular Receptors

Tendon & Muscle

Receptors

CNS

Alphamotor

neurons

ExtrafusalMuscleFibers

Gammamotor

neurons

IntrafusalMuscleFibers

PROPRIOCEPTION & NEUROMUSCULARCONTROL MODEL

DY

SFUNC

TION

DYSFUNCTION

DYSFUNCTION

FUNCTIONAL INSUFFIENCIES: FUNCTIONAL INSUFFIENCIES: STRENGTH DEFICITSSTRENGTH DEFICITS

Eversion strength deficits

Inversion strength deficits

Muscle damage vs. Neuromuscular inhibition?

FUNCTIONAL INSUFFIENCIES: FUNCTIONAL INSUFFIENCIES: IMPAIRED POSTURAL CONTROLIMPAIRED POSTURAL CONTROL

Modified Rhomberg Test

Unilateral vs. bilateral differences

Is quiet standing sensitive enough to detect functional deficits?

ChronicAnkle Instability

MechanicalInsufficiencies

Functional Insufficiencies

Pathological LaxityArthro-

kinematicRestrictions

SynovialChanges

DegenerativeChanges

ImpairedProprioception Impaired

NeuromuscularControl

StrengthDeficits

ImpairedPosturalControl

RecurrentAnkle Spain

DIFFERENTIAL DIAGNOSIS:DIFFERENTIAL DIAGNOSIS:WHEN IT ISN’T AN ANKLE SPRAINWHEN IT ISN’T AN ANKLE SPRAIN

Fractures– Fibula– Tibia– Talus– 5th metatarsal

Osteophytes

Osteochondral lesionsPeroneal retinaculum tearsPeroneal tendon lesionsNerve injuryGout Rheumatoid arthritis

PRACTICAL APPLICATIONS:PRACTICAL APPLICATIONS:ASSESSMENTASSESSMENT

Laxity– Look beyond the

talocrural joint

Arthrokinematics– Role of hypomobility

PRACTICAL APPLICATIONS:PRACTICAL APPLICATIONS:REHABILITATIONREHABILITATION

Neuromuscular Retraining – Proprioception &

Neuromuscular Control

– Postural Control – Strengthening

PRACTICAL APPLICATIONS:PRACTICAL APPLICATIONS:PREVENTIONPREVENTION

Completion of structured neuromuscular rehabilitation program significantly reduces recurrent ankle sprains (Holme et al., 1999)

Ankle bracing significantly reduces recurrent ankle sprains (Surve et al., 1994)

WHAT WE DON’T KNOWWHAT WE DON’T KNOWWhat are the relationships between individual insufficiencies?

Which insufficiencies are most predictive of development of chronic instability?

How can we best prevent chronic ankle instability?

CONCLUSIONSCONCLUSIONS

Residual impairments after lateral ankle sprain remain problematic

Multifactorial etiology of chronic ankle instability is not entirely understood

Specific mechanical and functional insufficiencies should be assessed and treated accordingly on a per patient basis

THANKTHANKYOUYOU