MOTOR CONTROL IN ANKLE INSTABILITY

Presenter: Dr Pooja Joshi Moderator : Dr D.N.Bid

Functional Anatomy

Ankle is a stable hinge joint Medial and lateral displacement is

prevented by the malleoli Ligament arrangement limits inversion

and eversion at the subtalar joint Square shape of talus adds to stability of

the ankle Most stable during dorsiflexion, least

stable in plantar flexion

Degrees of motion for the ankle range from 10 degrees of dorsiflexion to 50 degrees of plantar flexion

Normal gait requires 10 degrees of dorsiflexion and 20 degrees of plantar flexion with the knee fully extended

Normal ankle function is dependent on action of the talocrural joint and subtalar joint

Stability

1. static stability2.dynamic stability

1.static stability Mechanical static or passive stability of a joint

may be due to geometry of the articular restraints as well as primary and secondary static restraints.

The lateral ligaments provide static stabilization of the AJC, along with the medial deltoid ligament, distal anterior tibiofibular ligament, interosseous membrane, and joint capsule.

The unique AJC bony articulation of the tibia, fibula, talus and calcaneus defines the articular restraints. Passive structures such as ligaments and capsule provided passive stiffness at the extremes of motion

2.Dynamic ankle stability can be defined as the ability of the ankle joint to maintain equilibrium in response to an external perturbation.

Maintaining ankle stability during gait and other activities is necessary in order to prevent any injuries.

Dynamic ankle stability is influenced by passive mechanisms such as ligamentous stiffness, active mechanisms such as muscle stiffness, and neuromotor mechanisms such as reflex and voluntary control.

Instability

Types : 1.mechanical 2.functional

1.functional joint instability If a patient complains of instability, but has

a normal physical exam (no laxity) the instability may be a result of the deficits in the sensorimotor system (proprioception or neuromuscular control) and has been diagnosed as functional ankle instability.

2.mechanical joint instability excessive laxity and subjective instability

of the AJC suggest mechanical tissue damage (ligament and/or capsule) that may be accompanied by reduced sensorimotor control. These patients have been diagnosed with mechanical ankle instability.

Prevalence

Prevalence of ankle instability is 35% in normal population

In sports population it is 50% 80% of ankle instability because of

ankle sprain

causes

Ankle sprain Repetitive trauma Change in muscle tone Sensory-motor disturbance

Symptoms 1.pain 2.swelling 3.repetitive injury 4.balance problem 5.feeling of giving away

Assessment

History Past history Mechanism of injury Type of, quality of, duration of pain? disability Previous treatments

Examination

Ankle joint complex range of motion (ROM) is determined in each of the six degrees of freedom of a joint.

Excessive ROM or laxity may be inversion/eversion, plantarflexion/dorsiflexion, and abduction adduction rotations, or anterior/posterior, medial/lateral and upward/downward translations.

Ligament, capsule, muscle and tendon length will affect the AJC ranges of motion.

Many clinicians attempt to determine if the ROM was normal or abnormal based on their “feel” and clinical experience with comparisons to the other side.

Ankle Stability Tests Anterior drawer test

Used to determine damage to anterior talofibular ligament primarily and other lateral ligament secondarily

A positive test occurs when foot slides forward and/or makes a clunking sound as it reaches the end point

Talar tilt test Performed to determine extent of

inversion or eversion injuries With foot at 90 degrees calcaneus is

inverted and excessive motion indicates injury to calcaneofibular ligament and possibly the anterior and posterior talofibular ligaments

If the calcaneus is everted, the deltoid ligament is tested

Anterior Drawer Test Talar Tilt Test

Kleiger’s test Used primarily to determine extent of

damage to the deltoid ligament and may be used to evaluate distal ankle syndesmosis, anterior/posterior tibiofibular ligaments and the interosseus membrane

With lower leg stabilized, foot is rotated laterally to stress the deltoid

Medial Subtalar Glide Test Performed to determine presence of

excessive medial translation of the calcaneus on the talus

Talus is stabilized in subtalar neutral, while other hand glides the calcaneus, medially

A positive test presents with excessive movement, indicating injury to the lateral ligaments

Kleiger’s Test Medial Subtalar Glide Test

Stress RadiographsAnterior drawer – Absolute Displacement: 10mmSide to side: >3mmTalar Tilt – Side to side: >10º

Functional Tests While weight bearing the

following should be performed Walk on toes (plantar flexion) Walk on heels (dorsiflexion) Walk on lateral borders of

feet (inversion) Walk on medial borders of

feet (eversion) Passive, active and resistive

movements should be manually applied to determine joint integrity and muscle function

If any of these are painful they should be avoided

Motor control

According to Brooks, a neurophysiologist, “Motor control is the study of posture and movements that are controlled by central commands and spinal reflexes, and also to the functions of mind and body that govern posture and movement.”

among motor control theorists. Bernstein is most well-known for his “degrees of freedom” problem: How does the brain control so many different joints and muscles of the body?

The statement of the degrees of freedom problem brought renewed focus on the physical aspects of the body, particularly the musculoskeletal system and its role in motor control.

Motor control problems may include deficits in initiation of movement, termination of movement, and speed and direction control.

These difficulties often are associated with abnormal movement patterns. Many factors may contribute to a patient exhibiting an abnormal movement pattern.

These contributing factors may originate centrally, peripherally, or both.

Central factors may include damage to the neural circuitry that generates the movement pattern, aberrant input (inhibition or facilitation) to the circuitry, or abnormal motor neuron recruitment.

Peripheral factors may include muscle fiber atrophy, changes in muscle stiffness, and muscle shortening

Types of concepts

1.open loop control 2.closed loop control 3.voluntary control

Open-loop control

The open system model is characterized by a single transfer of information without feedback loops

This model is used in the traditional reflexive hierarchical theory of motor control

before stimulus onset muscle activation to prepare oneself for the stimulus .

In the ankle, this consists of activating the musculature surrounding the joint before stimulus onset (landing) to control dynamic stability.

Closed-loop control

the closed system model has multiple feedback loops and supports the concept of distributed control

In the closed model, the nervous system is viewed as an active agent with structures that enable the initiation and generation of movement

They proposed that damage to the proprioceptive ligamentous structures. after LAS created a void in the proprioceptive feedback to the central nervous system and predisposed those individuals to episodes of the ankle “giving way”

Arthrogenic muscular inhibition

It has been postulated that altered neuromuscular control patterns may be due to residual arthrogenic muscle inhibition

which is described as a continuing inhibition of the musculature surrounding a joint after swelling or damage to the structures of that joint

Swearingen and Dehne , who found the decreased stress tolerance of an injured joint triggers a reflexive inhibition which affects muscles that are capable of increasing tensile stress on the damaged ligaments.

It follows that the ankle invertors would be inhibited after lateral ankle joint injury because they can initiate movement in the same direction as the initial injury.

ANKLE JOINT MECHANORECEPTORS Type I: slow adapting, low

threshold Convey postural sense Type II: rapid adapting, low

threshold Convey sense at beginning of joint movement

Type III: slow adapting, high threshold Convey sense at extreme end ROM

JOINT MECHANORECEPTORS

• influence gamma motor neuron output:

determine length of muscle spindle fibers

• Influence discharge of spindle afferents and input on alpha motor neurons adjust muscle length or tension to protect joint from injury

Role of Proprioception in Sensorimotor Control of Functional Joint Stability

Motor control for even simple tasks is a plastic process that undergoes constant review and modification based upon the integration and analysis of sensory input, efferent motor commands, and resultant movements.

Proprioceptive information stemming from joint and muscle receptors, as previously demonstrated, plays an integral role in this process.

Underlying the execution of all motor tasks are particular events, often very subtle, that are aimed at preparing, maintaining, and restoring stability of both the entire body (postural stability) and the segments (joint stability).

neuroplastisity

CNS is massively adaptable. If we can drive both spontaneous and purposeful changes in structure and function with attended, repetitive, rewarded behaviors, then we should be able to reverse negative musculoskeletal and neurological behaviors through focused, selective, goal-directed repetitive behaviors

Use of external ankle support to provide sensory motor input during exercise

1

Motor imagery and mirror therapy

Types of imagery

1. Affirmation imagery2. Healing imagery3. Treatment imagery4. Performance imagery

Tapping and bracing

Taping the AJC prior to participation in high-risk sports such as football, basketball, soccer, and volleyball has been successful in preventing ankle injuries

summary

After reducing pain and swelling motor control training is necessary to give to prevent further injury

Concepts Open loop control Closed loop control Muscular inhibitionRecent techniques Motor imagery Mirror therapy Tapping

References . Delahunt, E. & Physiotherapy, Ã., 2007. Neuromuscular contributions to functional

instability of the ankle joint. , pp.203–213.

Gutierrez, G.M., Kaminski, T.W. & Douex, A.T., 2009. Clinical Review : Focused Neuromuscular Control and Ankle Instability. PMRJ, 1(4), pp.359–365. Available at: http://dx.doi.org/10.1016/j.pmrj.2009.01.013.

Mckeon, P.O. & Hertel, J., 2008. Ankle Instability , Part I : Can Deficits Be Detected. , 43(3), pp.293–304.

Noronha, M.D. et al., 2007. Loss of proprioception or motor control is not related to functional ankle instability : an observational study. , 53(Gross 1987), pp.193–198.

Rodriguez-merchan, E.C., 2012. Chronic ankle instability : diagnosis and treatment. , pp.211–219.

Vaes, P., Gheluwe, B.V. & Duquet, W., Control of Acceleration During Sudden Unstable Ankle Supination in People. , 31(12).

Michelson JD, Hutchins C: Mechanoreceptors in human ankle ligaments. J Bone Joint Surg (Br) 1995: 77-B : 210-24.

Bulluss, C. et al., Foot and Ankle Session. Gutierrez, G.M., Kaminski, T.W. & Douex, A.T., 2009. Clinical Review : Focused

Neuromuscular Control and Ankle Instability. PMRJ, 1(4), pp.359–365. Available at: http://dx.doi.org/10.1016/j.pmrj.2009.01.013.

Hoch, M.C. & Mckeon, P.O., Integrating Contemporary Models of Motor Control and Health in Chronic Ankle Instability. , pp.82–88.

Mckeon, P.O. & Hertel, J., 2008. Ankle Instability , Part I : Can Deficits Be Detected. , 43(3), pp.293–304.

Munn, J., Sullivan, S.J. & Schneiders, A.G., 2010. Evidence of sensorimotor deficits in functional ankle instability : A systematic review with meta-analysis. , 13, pp.2–12.

Noronha, M.D. et al., 2007. Loss of proprioception or motor control is not related to functional ankle instability : an observational study. , 53(Gross 1987), pp.193–198.

Rodriguez-merchan, E.C., 2012. Chronic ankle instability : diagnosis and treatment. , pp.211–219.

Ross, S.E. et al., 2011. Gait & Posture Balance assessments for predicting functional ankle instability and stable ankles. Gait & Posture, 34(4), pp.539–542. Available at: http://dx.doi.org/10.1016/j.gaitpost.2011.07.011.

Vaes, P., Gheluwe, B.V. & Duquet, W., Control of Acceleration During Sudden Unstable Ankle Supination in People. , 31(12).