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Mechanics and control of the pes planus versus normal foot

during jumping and landing

Reporter: Reportor : Zong-Shein Chen

Supervisor : Sai-Wei Yang

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Introduction

Pes planus (flat foot)- the medial longitudinal arch of foot is lower than established normal parameters

~ Forrester D et al. Imaging of the foot and ankle;1988

The terms of pes planus :- Flexible : An observable medial arch during nonweightbearing and a flattening of the arch during weightbearing- Rigid : A stiff, flattened arch on and off weightbearing

~ Lee MS et al. J Foot Ankle Surg; 2005

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Abnormal biomechanical behaviors

The MLA collapses right down Most of the plantar surface of foot contact with the

ground More strain on the plantar aponeurosis Facilitating dorsiflexion Unlocking of the midtarsal joint

~ Prost WJ. Fam Physician; 1979

In clinically and functionally, the rearfoot of flat foot subjects is valgus and the forefoot is varus

~ Bertani A et al. Clin Biomech. 1999

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Greater inversion ankle moment Greater peak plantarflexion ankle moment Less forefoot adduction Less forefoot total transverse plane ROM

~ Hunt AE et al. Clin Biomech; 2004

Greater foot pressure under the second and third metatarsal heads

Greater foot pressure under the subhallucal area ~ Hunt GC. Examination of lower-extremity dysfunction; 1990

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Injuries relate to pes planus

Pes planus are associated with a higher risk of injury among physically active people

~ Kulthanan T et al. J Med Assoc Thai; 2004

Subjects with pes planus feet exhibited greater incidences of soft tissue and medial foot injuries and knee injuries

~ Williams DS et al. Clin Biomech; 2001

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Sesamoiditis Plantar fasciitis Achilles tendinitis Medial shin pain Patello-femoral joint pain Metatarsal stress fractures Navicular and fibular stress fractures

~ Hunt AE et al. Clin Biomech; 2004 Posterior tibialis tendon dysfunction

~ Kulig K et al. Med Sci Sports Exerc; 2005

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Risk sports for foot and ankle injury

~ DeLee et al. Br J Sports Med; 2003

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Jumping and landing Jump-landing protocols have been used to meas

ure postural sway

In an attempt to reduce the landing force the body must anticipate the landing and prepare for it by increasing muscle stiffness

~ McKinely P, Pedotti A. Exp Brain Res ;1992

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Purpose

Few investigations focus on the jumping and landing biomechanical behaviors of pes planus subjects

The purpose in this study is to explore the jumping and landing biomechanical behaviors and the difference between pes planus and normal subjects

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Hypothesis

Pes planus subjects have different jumping and landing biomechanical behaviors from normal foot subjects, including COP excursion way, magnitude and direction of GRF, relative motion of foot-leg-knee and the EMG activity of the muscle

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Methods - Participants

Thirty adult, aged from 18 to 25 years old Inclusion criteria :

- arch index (AI > 0.25) - flexible pes planus

~Williams DS et al. 2000

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Exclusion criteria :- Acute foot injuries- Previous osseous foot surgery- Diagnosed with inflammatory arthritis, diabetes mellitus, congenital defects or neuromuscular disease

Control group - Thirty adult, aged from 18 to 25 years old- normal arch index (0.18<AI<0.25)

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Instrumentation

Vision motion analysis system ~ VICON : to collect kinematic data

AMTI force plate : to collect kinetic data

Surface EMG : to collect muscle activation data, tibialis posterior, peroneus longus, medial and lateral gastrocnemius, vastus medialis and lateralis

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Procedures

Four conditions, and 3 trials for each condition :

1. Vertical jump with both legs at maximum effort and to land with both legs

2. Vertical jump with both legs at maximum effort and to land on the dominant leg

3. Forward jump with both legs and to land with both legs

4. Forward jump with both legs and to land on the dominant leg

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Data analysis

Descriptive statistics and two-way ANOVA tests will be used to compare the difference of testing order effects and four experimental conditions

Tukey’s post-hoc test will be used when an overall significant differences are found

An alpha level of 0.05 will be used to test for significance

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Thanks for your attention

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Reference

Lee MS, Vanore JV et al. Diagnosis and Treatment of Pediatric Flatfoot. J Foot Ankle Surg. 2005;43:341-373

Hunt AE, Smith RM. Mechanics and control of the flat versus normal foot during the stance phase of walking. Clin Biomech. 2004;19:391-397

Ledoux WR, Hillstrom HJ. The distributed plantar vertical force of neutrally aligned and pes planus feet. Gait posture. 2002;15:1-9

Prost WJ. Biomechanics of the foot. Fam Physician. 1979;25:821-31 Hunt GC. Orthopaedic and sports physical therapy. Examination of lower-ex

tremity dysfunction. Second Edition. 1990:395-421 Williams DS, McClay IS et al. Arch structure and injury patterns in runners.

Clin Biomech. 2001;16:341-347 Kulig K, Burnfield JM et al. Effect of foot orthoses on tibialis posterior activat

ion on persons with pes planus. Med Sci Sports Exerc;2005:24-29 Hertel J, Sloss BR et al. Effect of Foot Orthotics on Quadriceps and Gluteus

Medius Electromyographic Activity During Selected Exercises. Arch Phys Med Rehabil. 2005;86:26-30