Neuropathy of the foot has more to do with mechanical trauma than secondary condition such as diabetes, alcoholism, etc. Learn more at www.GraMedica.com.

1. Tibialis Posterior Neuropathy
Michael E. Graham, DPM, FACFAS

2. What is TPN?
• Pathologic condition of the tibialis posterior
nerve.
• Wide variety of symptoms.
• MUST be differentiated from “peripheral
neuropathy”
• Let’s discuss treatment options.

3. Pathway of plantar
foot nerves.

4. What happens when your big toe
touches something, how do you feel it?

5. Following the chemical reaction from the big toe to
your brain and back again in a matter of seconds.

6. Sensory Nerves in the big toe

7. However these signals don’t travel
superficially but traverse deep into the foot.

8. Let’s take a closer look.

10. Abductor Hallucis Brevis Muscle
• Could be a big source
of trouble if it crushes
the plantar nerves.
• Its function is to
stabilize the medial
column of the foot, i.e.
the 1st ray.
• What would happen if
this patient had a
hypermobile medial
column?

12. The porta pedis is a
very concerning area.
As the medial and
lateral plantar nerves
travel towards the
spine their path is
transformed from
horizontal to vertical.

13. Porta Pedis
• Tunnel is created
mostly from fibers
attaching the
abductor hallucis
muscle belly to the
calcaneus along with
dense connective
tissue similar to the
flexor retinaculum.

14. Constriction of the Porta Pedis
• Let’s think about what
is in the porta pedis-
– Medial & Lateral
Plantar nerves
– Medial & Lateral
Plantar arteries
– Medial & Lateral
Plantar veins

15. Contents within the porta pedis in a rectus foot.
LN = Lateral Plantar nerve
MN MA
MN = Medial Plantar nerve
LV= Lateral Planar Vein LA
LN
MV = Medial Plantar Vein
LA = Lateral Plantar Artery LV
MV
MA = Medial Plantar Artery
There is plenty of room and every thing is functioning normally.

16. What could possible happen to
the structures within the porta
pedis if it was constricting with
every step taken or constantly
constricted while standing?

17. Contents within the porta pedis are crushed due to
dislocation of the talus on the tarsal mechanism.
M M
N A
L
Abductor Hallucis
Muscle
N
L M
L
A
Calcaneus
V V
There is less room and the structures are compressed decreasing
blood flow and altering the natural function.

18. Effects of TaloTarsal Dislocation
During the Gait Cycle
What happens to the porta pedis
MN MA M M
N A
L
N
LN LA Excessive L
A
Force
L M
LV
MV V V
Porta Pedis during Porta Pedis during mid-
swing phase or stance in a dislocation
of the talotarsal
non-weightbearing joint/weightbearing

19. Now we have shown what can
happen to the nerve travelling
through the porta pedis.
Let’s take a look at the neurovascular
canal within the flexor retinaculum.

20. Compression of the porta pedis.
• Constricts blood flow
to the plantar aspect
of the foot.
• This will build up the
pressures proximally
within the tarsal
tunnel.
• This will lead to more
destruction
proximally.

21. Rectus Rearfoot Alignment
These feet will NOT place additional strain on the porta pedis or
combined / individual chambers within the flexor retinaculum.

22. What happens if the hindfoot is not
properly aligned?
This will place a tremendous amount of destructive
forces on the contents of the porta pedis & tarsal
tunnels.

23. Normal Talotarsal Alignment
Articular facets are aligned
Sinus tarsi is open
Normal Cyma
Normal Talar declination angle
Normal navicular height

24. Normal to abnormal alignment
Sinus tarsi partially collapses/obliterates

25. Talotarsal Dislocation
• The articular facets of
the talus are no longer
aligned with the
articular facets of the
calcaneus.
• Incomplete dislocation
is present.
• A pathologic event has
occurred, this is NOT a
self-resolving condition.
• It requires physical
intervention.

26. Obviously it is important that nothing compresses the
nerves within the porta pedis or tarsal tunnel.
Nerves exit the
porta pedis and
quickly enter the
distal aspect of the
tarsal tunnel.

27. Distal Tarsal Tunnel
• As the nerves travel
proximally they pass
deep to the flexor
digitorium longus
tendon and enter into
the distal aspect of
the tarsal tunnel.

28. Flexor Retinaculum - roof of tarsal tunnel.
• Purpose:
• Retinaculum is more for the
tendons than for the
nerves.
• In a hypermobile hindfoot it
will have a
s t r e t c h placed on it.
This tissues will either thin out
OR react to these abnormal
forces by thickening. The
thicker the tissues the less
likely it is to fail. However,
due to the chonicity of walking
the tissues cannot prevent the
hypermobility.

29. Flexor Retinaculum/Laciniate Ligament
• Proximal attachment
with the deep fascia
of lower leg
• Distal attachments
are with the plantar
fascia and the
abductor hallucis
muscle

30. Flexor Retinaculum- 4 canals
• Tibialis Posterior
• Flexor Digitorium
Longus
• Posterior-
Artery/nerve/vein
• Flexor Hallucis
Longus

31. Imagine what is occurring to the flexor
retinaculum.
• It is being pulled apart
• The distal end is
being pulled by the
abductor hallucis
muscle and the
plantar fascia.
• This causes major
constriction and
compression of the
structures within the
flexor retinaculum.

32. Contents 3rd tunnel in the flexor retinaculum in a
rectus foot.
TPN TPA
TPV
There is plenty of room and every thing is functioning normally.

33. In response a thicker Flexor Retinaculum will occur to
try and overcome these stretching forces.
• Well, this will immediately
compress the underlying
nerves which flattens it.
• Flattening of the nerve
not only crushes the
nerve fibers it also
decreases the blood flow
within the nerve.
• Think of standing on a
garden hose or repeated
stepping on a garden
hose say 7,000 a day for
50 years.
• Maybe after doing this for
so long there could be
damage to the nerve?

34. Comparison- there is stretched placed on these
structures as the talus slips off the tarsal mechanism.
Normal Abnormal

35. Talotarsal instability is not kind to the
structures within the tarsal tunnel.

36. Contents 3rd tunnel in the flexor retinaculum with
talotarsal instability.
P M
N A
MV
There is compression of the neurovascular structures.

37. During Walking
However, as soon as the
With no weight on the heel touches the ground the
foot there are no talus slips off the tarsal
abnormal forces acting mechanism and the
on the structures excessive abnormal forces
begin to take effect on the
within the tarsal structures within the tarsal
tunnels. tunnels.

38. DID YOU KNOW
Active person takes 8,500 steps/day
A 50 year old has taken
152,022,500
steps.

39. Just think about all that damage
being inflicted onto the nerves.

40. Eventually Damage occurs to the nerve
• The outer most fibers
are affect first
• Due to the constricted
blood flow within the
nerve the outer most is
first to loose the blood
flow.
• Also the physical
trauma to the nerve
damages the myelin
sheath decreasing
nerve impulses.

41. Nerve Injury cycle.
During the walking cycle the nerve is intermittently
compressed.

42. Nerve Injury cycle.
While standing the nerve is
continuously compressed.

43. If the chemical signal is able to pass
through the porta pedis and the tarsal
tunnel it will continue up the leg

44. Eventually the nerve signal travels
proximally up the leg...
…that if its allowed to pass
through the porta pedis
and tarsal tunnel.

45. How can we fix this problem?
• Observation?
• Shoes?
• Arch supports/Orthotics?
• Pills- vitamin supplements, nerve
“desensitizers” (lyrica, cymbalta,
gabapentin)
• Microvas?
• Magnets?
• Nerve Testing?

46. This is an internal problem that
demands an internal solution!
• The nerve damage is a secondary
condition not primary.
• Diabetes, alcoholism, and chemotherapy
are not going to make this condition any
better but they can make it worse. Even if
controlled there is no evidence of
improved/cure nerve disease.

47. Tarsal Tunnel Pressures-
What do we know?
Neutral STJ 2 (0-7) mmHg
Maximally pronated 32 (12-60)
mmHg
Pronation = 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

48. Increased Tarsal Tunnel Pressures
What 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

49. Nerve Strain/Tension
What 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

50. Nerve Strain/Tension
What 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

51. Nerve Strain/Tension
What 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

52. 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

53. How can we eliminate the
hyperpronation?
• Orthotics?
• Special Shoes
• Braces/splints
• Exercises/stretching

54. Custom-molded “Orthotics”

55. Internal deformity = Internal Correction

56. Two Part Study
Stabilized Hindfoot
TaloTarsal Dislocation With HyProCure
• Pressure Measurements • Pressure Measurements
within the within the
– Tarsal Tunnel – Tarsal Tunnel
– Porta Pedis – Porta Pedis
• Strain of the Posterior • Strain of the Posterior
Tibial Nerve Elongation in Tibial Nerve Elongation in
a hyperpronating foot. a hyperpronating foot.

57. The Effect of HyProCure Sinus Tarsi Stent
on Tarsal Tunnel and Porta Pedis Pressures.
Journal of Foot and Ankle Surgery, Volume 50, Issue1 Pages 44-
49, January 2011
Part I findings
Pressure Measurements

58. Cadaver Set-Up

59. Tarsal Tunnel

60. Porta Pedis

61. TT Pressures Without HyProCure With HyProCure
Specimen Hyper- Hyper-
No. Neutral Pronated Neutral Pronated % Reduction
n = 3 for each reported data value HyProCure
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 37
Grand 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

62. Maximally
Specimen Maximally Pronated % Reduction
No. Neutral Pronated Neutral HyProCure foot
after
n = 3 for each reported data value HyProCure
1 2 27 1 20 26
2 3 25 5 14 43
3 1 26 1 14 45
4 1 16 2 7 57
5 1 25 2 21 16
6 1 28 0 19 33
7 2 32 2 19 42
8 2 15 2 7 54
9 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 - 57
95% C.I. 1.4 - 2.7 23.0 - 34.5 1.6 - 3.3 14 - 22.8
Porta Pedis Study

63. Overall Results
32 21 29 18
34% reduction- Tarsal tunnel
38% reduction- Porta pedis

64. Effect of Extra-Osseous TaloTarsal
Stabilization on Posterior Tibial Nerve Strain
in Hyperpronating Feet: A Cadaveric
Evaluation
Journal of Foot and Ankle Surgery, Volume 50, Issue 6 , Pages
672-675, November 2011
Part II Findings
Strain on the Tibialis Posterior
Nerve

65. 9 Cadaver Specimens
%
Reduction
in
Elongation Strain Elongation
Without With Without With
HyProCure® HyProCure® HyProCure® HyProCure®
in mm in %
Mean ± 1
S.D. 5.91 ± 0.91 3.38 ± 1.20 26.81 ± 4.6 15.38 ± 5.65 43%
Range 3.02 - 7.19 1.25 - 5.23 12.5 - 33.87 5.24 - 23.57

66. Significant Decrease with Talotarsal
Stabilization

67. 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
• Repetitive Trauma to the nerve fibers

68. 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.

69. Next Step-Suggestions
• Early presentation- internal stabilization
with HyProCure® as a stand-alone
procedure
• Significant symptoms- combined
neurolysis decompression along with
HyProCure®

70. to be continued…

71. Thanks
For more information please visit:
www.HyProCure.com