Importance of Topic 5/17/2013. Rethinking Proprioception Training & Ankle Instability. Dr Emily Splichal, DPM, MS, CES

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1 Rethinking Proprioception Training & Ankle Instability Dr Emily Splichal, DPM, MS, CES Evidence Based Fitness Academy Applying Research Achieving Results Importance of Topic JBJS 2010 study found average 2.5 ankle sprains / 1000 adults. With nearly 49% occurring during athletic activity. 41% of athletic-related ankle sprains occur in basketball 55% of ankle sprains never seek medical treatment Even the most minor ankle sprains have a disruption in the neuromuscular system and proprioceptive response 70% of ankle sprains have recurrent sprains or residual symptoms including joint laxity, pain or giving way With current rehab programming still seeing recurrent injuries is it time to challenge the current programming? 1

2 Evidence-Based Rehab Self-assessment for ankle rehab programs: 1. Are the exercises we choose proven or following evidence-based guidelines to improve ankle stability? 2. Are the exercises we choose effectively targeting the proprioceptive system that is impaired during ankle injury? 3. Are there advances in ankle rehab programming? Can we apply barefoot training concepts to better improve patient and athlete outcome? Ankle & Subtalar Joint Subtalar Joint 2

3 Ankle & STJ Stabilization a. What limits inversion? ATFL, CFL, PTFL, Cervical Ligament, Bifurcate Ligament, Peroneals b. What limits eversion? Deltoid ligament c. Other stabilizing mechanism is neuromuscular control 1. Reflex arc (closed loop system) stretch of peroneals 2. Ankle joint capsule proprioceptors tension dependent 3. Anticipatory contractures of lateral ankle (open loop system) Lateral Ankle Stability Types of Ankle Sprains a. Inversion 1. Plantarflexion (supination) stepping off curb, landing on inverted foot 2. 85% of ankle sprains are inversion b. Eversion (pronation) stepping in a hole 3

4 Classification of Ankle Sprains Grade I - Micro tear of a ligament Mild tenderness and swelling. Slight or no functional loss No mechanical instability (negative clinical stress examination) Grade II Incomplete tear of a ligament, mod functional impairment Mild to moderate ecchymosis Tenderness over involved structures Some loss of motion and function Grade III - Complete tear and loss of integrity of a ligament Severe swelling (more than 4 cm about the fibula) Severe ecchymosis Mechanical instability Acute Ankle Sprain Clinically: ROM, edema, ecchymosis, pain Xray: r/o fracture of styloid process (peroneus brevis), anterior beak of the calcaneus (bifurcate ligament), fibula, metatarsal Ultrasound: r/o ligament tear Typical treatment is RICE: Typically give patient crutches for couple days, then guarded weight bearing with ankle brace, then passive ROM, Day 7 active ROM, single leg exercises, barefoot training Sequalae to Inversion Sprain 1. Hypersupination (inversion) causes disruption to: 1. Ligaments, nerves, tendons and joint capsule 2. 70% of sprains have recurrent sprains and instability 1. Rule out mechanical causes of ankle instability 3. Residual symptoms after 6 months is considered chronic ankle instability 4

5 Chronic Ankle Instability a. Mechanical Instability 1. Ligamentous laxity, longitudinal tear in the PB tendon 2. Anterior drawer test or talar tilt test b. Functional Instability 1. Symptoms of instability and giving way 2. Cannot be associated with mechanical laxity, therefore must look at neuromuscular control Neuromuscular Control Defined as the interaction between nervous and musculoskeletal system to produce a desired effect 1. Open-loop (preparatory) 2. Closed-loop (reactive) Open Loop (Pre-Activation) Muscles contract to stabilize the ankle before the foot lands. Pre-activation contractures are based off of assumed foot position and GRFs established by previous pre-activation patterns during activities Analogy is like transfer of learning mind has experienced this movement pattern or muscle contracture pattern before or in this case this foot position, landing surface, velocity and GRFs Studies have demonstrated that FAI have slower pre-activation state secondary to disruption in the proprioceptive system. Slower pre-activation state is associated with decreased ankle stability at foot contact, greater inversion moment and faster peak GRFs 5

6 Closed Loop (Reactive) Reactive contractions secondary to proprioceptive (sensory) afferent input that goes to spinal cord and sends efferent signal to motor neurons. Example: Accidentally step off curb foot begins to overinvert, peroneal muscle spindles sense stretch (afferent signal) then reactively contract concentrically to pull foot into eversion (efferent signal) Referred to as peroneal reaction time (PRT) Closed loop or reactive training is basis of many ankle rehab programs What s interesting is this closed-loop feedback that controls PRT is actually not quick enough to prevent ankle sprain. IT TAKES 54 MSECS FOR YOUR PERONEAL MUSCLE PROPRIOCEPTORS TO DETECT THE STRETCH OF AN INVERSION ANKLE SPRAIN? IT TAKES ANOTHER 72 MSECS FOR THE PERONEALS TO REACTIVELY CONTRACT TO TRY AND PREVENT THE ANKLE SPRAIN. TOGETHER THAT'S 126 MSECS. IT TAKES ONLY 80 MSECS TO INVERT AND SPRAIN YOUR ANKLE. (J ATHLETIC TRAINING 2002) Conflict with Targeting PRT 1. Is a delay in PRT always a result of inversion injury? Or could it have been present before injury? 2. Does rehab programming that targets PRT increasing reaction time and improving stability? 3. PRT is a large nerve proprioceptive mechanism, but what about short nerve deficits and ankle instability? 6

7 Delay PRT Cause or Effect? Is a delay in PRT always a result of inversion injury? Or could it have been present before injury? Studies that looked at motor NCV have demonstrated a delay in the superficial peroneal nerve on not only the affected side but also the contralateral side. This suggests that not only can ankle injury impair the motor nerve conduction but perhaps the delayed nerve function predisposed the individual for ankle injury to begin with? Is targeting PRT the most effective for ankle rehabilitation? Should we be pre-screening our athlete s for delayed PRT to assess risk? Targeted PRT & Reaction Time Does rehab programming that targets PRT increasing reaction time and improving stability? 7

8 A 2007 study by Refshauge et al. evaluated the impact of ankle proprioception and stability after 4 weeks of wobble board training in subjects with FAI. What was observed is that wobble board training only improved movement detection velocity at the slowest speed. Studies have suggested that ankle inversion velocities are up to 3.5 degrees per second, however the wobble board program was associated with only a 1.1 degree per second. Large vs. Small Nerve Proprioception PRT is a large nerve proprioceptive mechanism, but what about short nerve deficits and ankle instability? Plantar cutaneous receptors play a key role in the maintenance of balance and stability A 2012 study by Hoch et al. found that those subjects with CAI not only had impaired proprioceptive feedback at the joint level but also as it relates to the skin on the bottom of the foot Study looked at small nerve fibers (Aβ) (plantar receptors) vs. large nerve fibers (Aα) (musculotendinous) and which played more important role in quiet stance and static posture Aβ small nerve fibers / plantar receptors 8

9 Current Treatment Guidelines So if closed-loop feedback and PRT is not fast enough to detect ankle inversion moments and is not specific to the proprioceptive deficits after ankle inversion injury Is it not time to challenge our current ankle rehab guidelines? Rethinking Proprioceptive Training for Ankle Instability Proprioceptive Training The term literally means to receive (-ception) / ones own (proprio) It is a subsystem of the somatosensory or neuromuscular system with proprioceptors found in connective tissue such as ligaments, joint capsules, tendons, fascia and skin Proprioceptors respond to stretch, pressure but also includes pain, touch, texture, temperature, vibration Includes both large nerve and small nerve proprioceptive responses! 9

10 What is Proprioceptive Training? Ask your average fitness professional or physical therapist what are some examples of proprioceptive exercises and you will probably get the wobble board, Airex pad, the Bosu Critics of these exercises argue: 1. These proprioceptive exercises only target PRT and large nerve function 2. Are these the most effective exercises for improving our foot & ankle proprioception? 3. Do proprioception exercises that target large nerve PRT translate to improved ankle stability and reduce the risk of re-injury? Small Nerve Proprioceptive Training With the popularity of minimalist footwear and barefoot running, have to take some of the same barefoot concepts into ankle rehabilitation programs. Benefits of barefoot science exceed barefoot running and need to be applied in the rehabilitation and athletic performance setting! Barefoot Science - beyond running beyond minimalist! One of the most important sensory input systems is human body is skin on the bottom of the foot. Thousands of mechanoreceptors that are sensitive to light touch, texture, vibration, pressure and skin stretch are stimulated with every shift of the body and each step we take. 10

11 Sensory Receptors Receptor Sensation Mechanoreceptors Touch, Proprioception Joint Receptors Joint Position Ruffini s Corpuscles Skin Stretch Merkel s Disks Texture Perception Pacinian Corpuscles Deep Pressure/Vibration Meissner s Corpuscles Light Touch Golgi Tendon Organs (GTO) Muscle Tension Muscle Spindles Muscle Length Small Nerve Proprioception Plantar cutaneous receptors play a key role in the maintenance of balance and stability Study looked at small nerve fibers (Aβ) (plantar receptors) vs. large nerve fibers (Aα) (musculotendinous) and which played more important role in quiet stance and static posture Aβ small nerve fibers / plantar receptors FAI & Small Nerve Dysfunction The 2012 study by Hoch et al. found that those subjects with CAI not only had impaired proprioceptive feedback at the joint level but also as it relates to the skin on the bottom of the foot! Hoch et al. found that he greatest impairment in tactile detection was between 10 Hz and 50 Hz which correlates with specific plantar mechanoreceptors such as: Ruffini organs (skin stretch), Merkel disks (texture perception), and Meissner corpuscles (light touch). If plantar cutaneous receptor sensitivity is so significantly impaired in those with CAI, wouldn t a more effective proprioceptive training integrate stimulation of the plantar receptors. 11

12 Rate of Small Nerve Discrimination 2000 study compared ability to detect inversion moments when shod vs. barefoot Found more accurate and faster moment detection in a barefoot environment vs. shoes Took this concept to textured insoles ability to detect moments remained faster than control Small nerve response i.e. skin stretch, texture, pressure sensory information is faster than relying on large nerve musculotendinous feedback Waddington G. et al. Textured insoles effects on ankle movement discrimination while wearing athletic shoes. Phy Ther Spor, (4): New Concepts Ankle Rehab Programming Goals of our ankle rehabilitation program a. A program that will more effectively enhance our foot & ankle small nerve proprioceptive system vs. only large nerve PRT programming b. A program that will challenge the openloop (pre-activation) system vs. only closedloop (reactive) system c. A program that will train the fastest input system and mechanisms which can detect faster inversion moments Barefoot Stimulation Fitness Rx Skin stretch J strap, Kinesio tape Textures Astroturf, textured insoles Vibrations Powerplate 12

13 Vibration Training Fitness Rx 2-3 times week All vibration training barefoot Do not exceed 60 seconds per stimulus Alternate feet Remember prolonged exposure to vibrations can dull mechanoceptors Lower frequency (Hz) preferable Oscillating vibrations preferable Perform balance / single leg exercises Perturbation Training Fitness Rx Perturbation training is a type of neuromuscular training that refines neural pathways to promote effective muscular recruitment patterns and dynamic joint stability - Strength Cond J 2011 Biggest difference between perturbation training and balance training is anticipation Initially introduce in a double leg stance, then to single leg stance then double leg on wobble board/bosu, then single leg on wobble board/bosu Begin low velocity and low frequency Do not exceed 30 seconds per side 38 For more great tips on building foot strength, barefoot training and barefoot rehab techniques