Dynamic Effect of Hyperpronation on the

tarsal tunnel & posterior Tibial nerve

Michael E. Graham, DPM, FACFASShelby Township, Michigan

Inventor-HyProCure, Founder/CEO GraMedica

How is it that patients with a very diverse medical background or no

medical issues have the same peripheral nerve symptoms?

SameSymptoms

Diabetes

IdiopathicHereditary

MedicationsHeavy Metals

Alcohol

Current Primary Etiologic Factors

What is the “Golden Thread” that connects these individuals?

What are our patients telling us?

• The more active I am the worse the symptoms.• The more I am off my feet, or the less active I

am, the less the symptoms.

• “Functional Symptoms”.• There must be a biomechanical component to

this disease process.

Obviously-where are they in the disease process determines the severity of their symptoms

• Grade 0• Grade I• Grade II• Grade III• Grade IV• Grade V

Posterior Tibial Nerve Study

Excessive Hindfoot Motion

Normal TaloTarsal Motion

• 1/3 Pronation• 2/3 Supination

Tarsal Tunnel Pressures- What do we know?

Neutral STJ 2 (0-7) mmHgMaximally pronated 32 (12-60) mmHgPronation = significantly increases pressure within

the tarsal tunnel with every step taken

Kumar et al: Evaluation of Various Fibro-Osseous Tunnel Pressures in Normal Human Subjects. Indian J Physiol Pharmaol, 32:139-145, 1988

Trepman et al.:Effect of Foot & Ankle Position on Tarsal Tunnel Compartment Pressure. Foot Ankle Int. 20:721-726, 1999

Barker et al: Pressures Changes in the Medial & Lateral Plantar and Tarsal Tunnels Related to Ankle Position: A Cadaver Study. Foot Ankle Int 28:250-254, 2007

Rosson et al: Tibial Nerve Decompression in Patients with Tarsal Tunnel Syndrome: Pressures in the Tarsal, Medial Plantar, and Lateral Plantar Tunnels. Plast Reconstr Surg 124:1202-1210, 2009

Increased Tarsal Tunnel PressuresWhat do we know?

• A pressure of 20 – 30 mmHg has been shown to impair intraneural blood flow

– Gelberman et al: Tissue Pressure Threshold for Peripheral Nerve Viability. Clin Orthop Relat Res 285-291, 1983

– Rydevik et al: Effects of graded comprssion of intraneural blood flow. An in vivo study on rabbit tibial nerve. J Hand Surg AM 6:3-12, 1981

Nerve Strain/TensionWhat do we know?

• Pronation increases the strain/tension on the posterior tibial nerve

– Francis et al: Benign Joint Hypermobility with Neuropathy: Documentation and Mechanism of Tarsal Tunnel Syndrome. J Rheumatol 14:577-581, 1987

– Daniels et al: The Effects of Foot Position and Load on Tibial Nerve Tension. Foot Ankle Int. 19:73-78, 1998

Nerve Strain/TensionWhat do we know?

• 8% venular flow obstructs• 15% complete arterial occlusion occurs

– Kwan el al: Strain, stress, and stretch of peripheral nerve. Acta Orthop Scand, 83:267-272, 1992

– Lundborg, G, Rydevik, B: Effects of stretching the tibial nerve of the rabbit. JBJS 55B:390-401, 1973

Nerve Strain/TensionWhat do we know?

• 6 % Strain decreases the amplitude of the action potential which recovers after removal of the strain.

• 12% strain produced a complete block and showed minimal recovery

– Wall et al: Experimental stretch neuropathy. JBJS 74B:126-129, 1992

Putting it all together

• Pronation increases pressure within the tarsal tunnel which interrupts intraneural blood flow

• Pronation increases nerve strain/tension

• In a normal amount of pronation• What about a hyperpronating foot• Average person takes 7,000-10,000 steps per day• 50 y.o. has taken roughly 152,022,500 steps

How can we eliminate the Hyperpronation?

• Orthotics?• Special Shoes• Braces/splints• Exercises/stretching

Custom-molded “Orthotics”can actually make the condition worse!

Normal to abnormal alignmenttalus drops forward and down

www.hyprocure.com

Two Part Study

Hyperpronating footStabilized Hindfoot

With HyProCure

• Pressure Measurements within the – Tarsal Tunnel– Porta Pedis

• Strain of the Posterior Tibial Nerve Elongation in a hyperpronating foot.

• Pressure Measurements within the – Tarsal Tunnel– Porta Pedis

• Strain of the Posterior Tibial Nerve Elongation in a hyperpronating foot.

Part I findings

Pressure Measurements

Cadaver Set-Up

Tarsal Tunnel

Porta Pedis

 TT Pressures Without HyProCure With HyProCure

% Reduction HyProCure

Specimen No. Neutral

Hyper-Pronated Neutral

Hyper-Pronated

  n = 3 for each reported data value

1 2 31 0 21 31

2 2 15 6 14 9

3 6 21 1 11 46

4 5 21 0 14 34

5 6 31 6 20 34

6 0 26 2 18 30

7 6 38 7 29 25

8 6 35 1 17 53

9 7 68 5 43 37Grand Mean

± 1 S.D. (n = 27) 4 ± 3 32 ± 16 3 ± 3 21 ± 10 34%Range (n =

27) 0 - 13 9 - 72 0 - 8 10 - 53 9 - 53

95% C.I. 3.2 – 5.7 25.6 – 37.9 2.1 – 4.3 16.7 – 24.8

Specimen No. NeutralMaximallyPronated Neutral

MaximallyPronated

HyProCure% Reduction

foot after

HyProCure n = 3 for each reported data value1 2 27 1 20 262 3 25 5 14 433 1 26 1 14 454 1 16 2 7 575 1 25 2 21 166 1 28 0 19 337 2 32 2 19 428 2 15 2 7 549 5 64 7 44 31

Grand Mean ± 1 S.D. (n =

27) 2 ± 2 29 ± 15 2 ± 2 18 ± 11 38%

Range (n = 27) 0 - 7 10 - 73 0 - 7 5 - 51 16 - 5795% C.I. 1.4 - 2.7 23.0 - 34.5 1.6 - 3.3 14 - 22.8

Porta Pedis Study

Overall Results

29 1832 21

34% reduction- Tarsal tunnel38% reduction- Porta pedis

Part II Findings

Strain on the Tibialis Posterior Nerve

Stay Tuned-

Why Posterior Tibial Nerve Involvement

• Increased Pressures within both the tarsal tunnel and porta pedis

• Flattening forces acting on the nerve(s)• Strain/elongation forces placed on nerve(s)• Intraneural damage• Vascular impairment within the nerve• Repetitive Trauma to the nerve fibers

Thoughts

• Patients present with a wide variety of medical backgrounds

• Short/Long-term results of pure decompression*?

• What is the missing piece to the puzzle?• External modalities are less than optimal• Internal stabilization is preferred

*Chaudhry V, Russell J, Belzberg A. Decompressive surgery of lower limbs for symmetrical diabetic peripheral neuropathy. Cochrane Database of Systematic Reviews 2008, Issue 3. Art. No.: CD006152. DOI: 10.1002/14651858.CD006152.pub2.

Next Step-Suggestions

• Early presentation- internal stabilization with HyProCure as a stand-alone procedure

• Significant symptoms- combined neurolysis decompression along with HyProCure

EBM-HyProCure

• 5 year retrospective study- 6% removal rate as a stand alone procedure

• Effect of HyProCure on Navicular Drop• Prospective Outcome Study soon to be

submitted for publication• The findings of this study will be published in 2

parts in Journal of Foot & Ankle Surgery 1st part should be in the Jan/Feb issue 2011.

QuestionsThank You