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NEUROPATHY and ARTHROPATHY  
IN THE INSENSITIVE FOOT  
  
PRESENTED IN FOUR PARTS    
  
PART THREE  
  
Peter F. Kelly, D.P.M., F.A.C.F.A.S.  
  
Diplomate, American Board of Podiatric Surgery  
Fellow, American College of Foot and Ankle Surgeons  
  
TABLE OF CONTENTS  
  
PART ONE  
  
Abstract						     3  
Introduction						     4  
Summary of Development of the Neuropathic Joint 	     4  
The Progression of Joint Destructive Hyperlaxity	     5  
The Clinical Appearance of Diabetic Neuropathy		     8  
The Histochemical Basis of Diabetic Neuropathies	     10  
Hereditary Peripheral Neuropathies			     12  
Acquired Peripheral Neuropathies			     13  
The Ulcerative Neurotropic Foot 			     15  
  
PART TWO						     17  
  
Abstract						     18  
Vascular Findings in Diabetic Neuropathy		     19  
Physical Exam						     20  
Clinical Findings of Charcot Joints			     21  
Radiologic Findings of Charcot Joints			     21  
Diagnostic Methods					     22  
  
PART THREE						     26  
  
Abstract						     27  
Principles of Therapy					     28  
Surgical Management					     32  
Conservative Management 				     33  
Medical Management					     37  
Summary 						     38  
  
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ABSTRACT  
  
     In the first of three parts of this paper, the more frequent etiologies of  
the various neuropathies causing arthropathies found in Podiatric  
Medicine were discussed.  Section two surveyed a variety of diagnostic  
modalities along with the clinical features useful in assessing the nature  
and extent of the neuropathies to the physician.  Section three covers  
medical and surgical therapeutic measures relating to the specific nature  
of the neuropathic symptomatology.   
  
PRINCIPLES OF THERAPY  
  
     The most common sequellae of peripheral neuropathy in lower  
extremity are foot ulcerations and osteoarthropathy.  By understanding  
what causes the damage to these tissues, the practitioner will be able to  
administer the most effective way of protection.  The determination of  
the forces creating destructive pressures on soft tissue during normal  
ambulation is nearly impossible because transducers which measure only  
the vertical component of sheer stress do not corellate quantitatively  
with the assessment of stress.  
  
     Much of the trauma is due to shear stresses resulting from  
simultaneous vertical and horizontal or rotary forces.	More than six  
hundred pounds per inch square is needed to produce a break or tear in  
human skin.  However, if there is some shearing stress with it, only 200  
pounds per square inch is necessary to be painful to limbs with normal  
sensation.  Such shear stress occurs at the edge of the area of distribution  
and results twisting or tearing of tissues.(44,45)   
  
     Five types of tissue damage are described by Brand:  
  
	  1. Continuous pressure causing a focal ischemia leading to  
	     necrosis,  
  
	  2. Concentrated high pressures causing a cutting or crushing  
of   
	     tissue,  
  
	  3. Heat or cold causing burning or frost bite,  
  
	  4. Repetitive mechanical stress, and   
  
	  5. Pressure on infected tissues.  
  
     Specific recommendations are given to the neurotropic patient which   
addresses these categories.  To avoid continuous pressure, the patient is   
advised to never wear new shoes for more than two hours at a time and  
then to observe for any area of of redness, swelling or irritation.   
Frequent changing of shoes, at midday and again in the evening, will to  
reduce the possibility of specific pressure sites over prolonged periods of  
time.  
  
     To reduce concentrated high pressure, the problem is not in dealing  
with excess force, but rather having a normal amount of force distributed  
over a reduced area.  It is important to recommend to the patient with  
insensitive limbs the practical applications of every-day living so that  
they can learn to think ahead and prevent such stresses. Practical   
applications such as never to walking barefoot and always shaking out a  
shoe before putting it on in case foreign object fall into the shoe during  
the night.    
  
     Patients with insensitive limbs should take extra care to their  
environment. Areas of normal travel may present as an accommodating  
walking surface, but in reality may prove to have intollerably high or low  
temperatures.  Barefoot walking on sandy beaches seems an excellent  
surface to walk on for those having plantar calluses, but the high density  
silicone constituents of sand retains a deadly amount of heat for soft  
tissue.  Foot problems may be also caused by burns from the floor of a  
car.  In this case thick carpeting to accommodate the car floor to the  
needs of the patient should be installed in order to provide thermal  
insulation from the floorboard.  
  
     Research by Brand has shown that repeated mechanical stresses on  
normal soft tissue results in moderate levels of inflammation.  The  
repetition continued on inflammed tissue intensifies inflammation,  
bringing in many new cells full of lysozomal enzymes into the area.   
Autolysis resulting in focal necrosis will occur in the area at the center of  
the stress.  The necrosis starts deep beneath the skin and will later form a  
fistula or sinus tract to the surface.  This area of necrosis is frequently  
predisposed by a hyperkaratosis, which initially acts as a biological  
protection but later turns into a source of pressure.     
  
     The remedy is lowering the pressure and redistributing the pressure,  
lowering the number of repetition by walking shorter distances or taking  
more frequent periods of rest with periodic examinations for  
inflammation, redness and swelling.    
  
     When a patient walks on a wound, the wound will become infected. 
	Continued walking on an infected wound spreads the infection  
through soft tissue planes, to bones and joints, and may result in severe  
destruction, sometimes necessitating amputation.  Therapy for infected  
lesions is immediate complete bed rest for a few days so that the  
swelling may be reduced by elevating the foot.  Antibiotic medication  
should be started immediately.    
  
     Once the acute stage is over, a total contact molded plaster cast is  
applied and the patient allowed to walk.  Used a generously padded cast.   
The dorsum of the cast should be cut approximately to the level of the  
metatarsal phalangeal joints to prevent excess pressure across  the  
dorsum of the foot. The cast is changed at weekly intervals and then the  
foot is  placed in extra-depth shoes as described.  A close watch should  
be kept on the ability of the ulcer to reduce and heal over as this is  
otherwise as indication for surgical resection or bone resection.  Periodic  
radiologic examination of Charcot joint changes and periodic vascular  
physiological examinations are performed using including continuous  
wave Doppler ultrasound.(46)      
  
     Chronic ulcerations and infections are discouraging to the patient, but  
these patients often have ample capacity to regenerate tissues and are  
good healers.  They should be encouraged that they will heal well if  
proper recommendations are followed.(47)   
  
     Four categories of foot conditions are seen in Hansens's disease as  
described Enna and co-workers.  However this system is highly  
appropriate to the staging and treatment of the diabetic foot.(48)    
  
     Category 1:  
  
	The foot has decreased or absent sensations but there are no  
soft tissue or skeletal deformities.  Specific stress-concentrated areas can  
be treated by a microcellular rubber insole with extra-depth shoes to  
eliminate pressure over the dorsum of the foot and accommodate the  
larger toe box and the microcellular rubber insole.  Patient education,  
periodic foot and shoe assessment are necessary.  
  
     Category 2:    
  
	The foot is insensitive and scarred on the plantar surface.   
There is a thinning of soft tissue underneath the metatarsal heads and at  
the distal ends of the toes.  This category is similar to that of category 1,  
but with a reduced shock absorbing capacity of the soft tissues.  A  
combination insole of molded polyethylene foam and microcellular  
rubber is recommended if scarring under the metatarsal head is  
pronounced or if the patient is an active walker.  Shoe requirements are  
generally the same as in category 1, with the addition of a metatarsal bar,  
to protect the metatarsal heads adequately and redistribute weight from  
off of the metatarsal heads to the diaphyseal region.  Caution is given to  
these patients against walking barefoot over hard surfaces, even for short  
distances as from the bedroom to the bathroom.  These patients are  
highly subject to trauma in areas of bony projection.  
  
     Category 3:    
  
	Soft tissue thinning and scarring with bony deformities of the   
metatarsal heads or toes. This may be a result of bone reabsorption due  
to distal neuropathic arthropathy or secondary to infection.	With this  
foot it is essential to have molded soft insoles with relief areas  
accommodating pressure on bone prominances.  Essential to prevention  
of plantar ulcers is a semi-rigid inner sole to support and maintain the  
shape of the molded insole.	  
  
    Category 4:    
  
	Extensive bone reabsorption has occurred with a shortening of  
the foot.  Osteophytic proliferation in the tarsal and metatarsal shafts  
produces multiple soft tissue pressure points from inside the foot.   
Complete digital reabsorption may occur, and a close relationship  
between conservative and surgical management is necessary for patients  
in this category.    
  
     Ankle range of motion is important in prevention of plantar  
ulceration.  Patients with equinus will place more stress on the distal end  
of the shortened foot.  The same therapeutic modalities as in category 3  
are used with the addition of toe fillers to prevent excess motion of the  
foot in the shoe and metatasal bars or wedges to shift the stress more  
proximally.  Custom-made shoes are the most effective footwear for  
these patients.  A rigid rocker bottom sole will also distribute weight- 
bearing stresses proximally off of the end of the foot.  The problem with  
conventional shoes is that the toe break is located distal to the hallux in a  
shortened foot as opposed to beneath the metatarsal phalangeal joint in a  
normal foot.(49)   
  
SURGICAL MANAGEMENT  
  
     Successful therapeutic attainment of foot function in the non&- 
ambulatory patient usually involves surgery.  These procedures are done  
to make their feet shoeable and prevent further pressure breakdown areas  
and pain.	The intent of the surgical procedures is to remove the  
unopposed deforming forces and improve foot position to a manageable  
conservative level at which time correction by orthoses may help  
maintain a certain minimum of functioning and ambulation. 
	Otherwise the muscle deterioration is unrelentless and  
progressive despite a patient's being confined to a wheelchair.    
  
     Surgical procedures to correct these fixed contractures should not be  
performed unless the following indications are present:  severe pain, skin  
breakdown or ulcerations, and the inability for the foot and ankle to  
accept reasonably costing and available shoe wear, including ankle-foot  
orthosis which are essential after the surgical releases.  A study by Hsu  
and Jackson suggests that the most common indication for surgical  
correction of the foot is a pressure over the dorsal lateral aspect of the  
foot.   
  
     For patients having Duchenne pseudohypotropic muscular dystrophy   
(DMD), spinal muscular atrophy (SMA), polio, etc., correctional  
procedures consist of the following: tendoachilles lengthening done as a  
first step, release of the posterior tibial tendon just proximal to the  
medial malleolus with occasional indication for transfer through the  
interosseous membrane and a variety of other releases including anterior  
tibial tendon release depending on the results of manual muscle testing.   
A long leg cast, then subsequently short leg cast holds the feet in  
corrected position which is then followed by an ankle foot orthosis  
(AFOs).(50)    
  
     It is unfortunate that there are high risks in this surgery, but this is  
because of the nature of the disability having generalized muscle  
weakness and advanced cardiomyopathy.  This necessitates detailed  
multi-system medical clearances, with special considerations for  
anesthesia.	  
  
     For local treatment, excision, or realignment of the offending bone  
might be indicated.  In addition to resecting old fibrotic tissue,  
ostectomy is indicated in patients having showing sharp osteophyte  
impingement on soft tissue due to hypertrophic tarsal anklylosis.   Split  
thickness skin grafts or microsurgically anastomosed free flaps might be  
necessary regardless of surgical or conservative management.	Molded  
shoes are indicated to try to avoid subsequent ulcerations or pathological  
fractures.(46,51-55)   
  
CONSERVATIVE MANAGEMENT  
  
     The standard of palliative care for the diabetics is periodic   
debridement of calluses and nails as necessary.  A multitude of  
specialized instruments is available and gentle, slow and gradual  
debridement of accumulated keratosis should be approached cautiously.   
Observations for subkeratotis ulcerations and preulcerative changes  
should be measured and documented.  Toenails should be debrided to a  
reasonable thickness as they are often grossly thickened as a result of  
either poor circulation or fungal infection.  A small bone cutter might be  
handy to keep on the tray for the palliative orthopedic work. 
	Treatment of fungal nails if indicated by positive cultures or  
KOH preparation can be by administration of griseofulvin.  Rarely  
should nail avulsion be resorted to in a diabetic.   
  
     Most of the lesions lie under the metatarsal heads where weight  
bearing is highest at heel-off.  Ulcers are found most frequently beneath  
the first metatarsal head, then the hallux, followed by the second and the  
third, then fifth metatarsal, and the heel.  The lateral plantar boarder and  
the distal aspects of the toes are other expected areas for  
ulcerations.(47,44,56)    
  
     Initial treatment for ulcers is soaking in either saline or betadyne-and- 
water and sterile dressing changes, with a surgical scrub brush scrubbing  
for five to ten minutes two or three times a day for debridement.  The  
base of the ulcer should be scrubbed vigorously to stimulate hyperemia  
and free bleeding.  Should a hyperkaratosis be present at the ulcer edge,  
sharp dissection is necessary to the point of free bleeding which will  
enable granulation tissue to grow.  Antibiotics should be continued  
several days after negative cultures.  Septic ulcers usually respond within  
seven to fourteen days.	Patients with osteomyelitis take anywhere  
from three to six weeks.    
  
     For topical ulcer therapy, polyurethane dressings are important in  
essentially maintaining a moist environment for healing.  Polyurethane is  
a thin polymer membrane which is semi-permeable to oxygen, CO2 and  
water vapor.  Its intent is to promote optimal conditions for wound  
healing that would otherwise exist beneath a naturally formed scab, but  
without the disadvantage of dehydration.  The dressing is applied and  
left undisturbed for seven to ten days at which point exudate rich in  
proteins, hormones and enzymes, and most importantly, epithelialization  
and fibroblasts migration is promoted more efficiently while  
oxygenation is optimized.  It has been the experience of some that there  
is striking reduction in treatment time and a reduction in costs  
expenditures during the ulcer therapy.(57)	  
  
     The loss of sudomotor function causes the skin to become dry and  
scaly.  Cracks develop in the flexion creases and subsequent infections  
are quite likely.  The patient should rehydrate the skin by daily water  
soaks for twenty minutes in mildly warm water twice a day, then treat the  
area to maintain hydration by covering with petroleum jelly.  At night a  
method of  decreasing the rate of evaporation for extremely anhydrotic  
feet is to place plastic bags over the feet after soaking and applying the  
petroleum jelly.  This can be done conveniently during sleeping hours  
and will keep the skin supple and less susceptible to injury and  
infection.(58)      
  
     Principles of shoe alterations and changing the location of stress is  
very important to apply to the neurotropic.	Reduction or elimination of  
the stress of the plantar surface of the forefoot is most effectively  
accomplished by a custom-made shoe which has a rigid rocker bottom  
sole.  There are certain features of this type of shoe.  The insole and the  
upper part must be molded to a model of the particular foot.  The shoe  
should be rigid and the distal end of the shoe turned upward.  Lastly, the  
rocker axis must be near the center of the foot and the rocker bottom  
must be thick enough to minimize contact between the end of the shoe  
and the floor during the toe-off phase of gait.  An additional advantage is  
the reduction of stride length thus earlier knee flexion as the weight line  
of the body progresses anterior to the rocker axis, reducing the impact of  
heel strike.(49)    
  
     The design of these devices is also supplemented by a Harris foot  
print recording.  These foot print impressions are made by means of a  
painted paper imprint laid upon a white sheet of paper which is placed  
on a rubber mat.  The transferred image of foot contact assumes a  
proportional size of the applied pressure.  This tool can increase the  
physician's ability to evaluate and prevent many of the areas of increased  
pressure or maldistributions that occur on the plantar surface.  
  
     A polyethylene-foam material, Plastazote, has been utilized in  
making insoles in normal custom-made footwear for patients with  
anesthetic feet.  It is economical and cheaper than ordinary microcellular  
rubber shoes and represents a significant advance in the care of the  
insensitive foot.  However before using Plastazote buildup, obtain  
footprints using the Harris footprint mat.    
  
     Plastazote is warmed to temperature of 130 to 140 degrees farenheit   
for three to five minutes, after which point it becomes very flexible.  A   
thin plastic sheating is placed between the Plastazote and the patient  
places their foot on the Plastazote while the technician exerts an even  
pressure on the patient's knee and over the toes for about one minute.   
The plantar impression is obtained and margins of the foot cut out.  A  
combination of rubber dust, saw dust and rubber cement can be used on  
the bottom of the Plastazote to build the concave points to ground level.   
This is then used in conjunction with a custom-made shoe or  
boot.(59,60,61)  
  
     Plastazote would seem to be the ideal answer from the standpoint of   
economy, rapidity of preparation and application to pressure  
distribution. However, it has been found with certain practitioners that  
Plastazote quickly loses its resilliance so that the area beneath the insole  
or under a pressure point can quickly become compressed to be as solid  
as the sole of the shoe itself.  To remedy this, a higher density Plastazote  
cradle was then developed in England which was also molded to the  
shape of the foot, windows were cut out underneath the pressure points  
and filled in with 6mm of Neoprene.  Neoprene has proven to be the  
most resilliant of the cushioning materials maintaining its recovery and  
provided that it's thick enough it will not "bottom out" under pressure.   
With these insoles the recurrence rate of ulcers has been negligible.(62)  
  
MEDICAL MANAGEMENT  
  
     If abnormalities of flow are response for lesions of the neuropathic  
foot, what can be done to influence them?  Lefaucher reported ligating  
the dorsalis pedis artery with resolution of ulcers in the neuropathic foot.   
Egotamine, an alpha-adrenergic agonist theoretically proves to be useful  
and has been shown to divert this blood flow from the arteriovenous    
anastomosies, however more research needs to be done in this area  
before such therapy is initiated in the treatment of the diabetic foot and  
microangiopathic peripheral vascular diseases.(63,64)  
  
     For relief of the burning foot syndrome, pantothenic acid has been  
administered.  To relieve the causalgic pain, cooling lotions, aspirin,  
propoxyphene and codeine are needed.  However, increased vitamin  
dosages have not proven to be of a therapeutic benefit if the neuropathy  
is not secondary to avitaminosis.  Trials of pyridoxine (vitamin B6) on  
neuropathic diabetic patients produce no objective improvement in  
sensory nerve conduction.  Results of any improvement in these patients  
not suffering from avitaminosis represent a placebo phenomena.  The  
only measurable improvement that may be obtained is in subjects  
suffering from true vitamin depletion.(62,65,66)   
  
SUMMARY  
  
     The triphasic nature of the peripheral neuropathy, with regards to     
motor, sensory and autonomic function, produces multiple  
manifestations that may elude the clinician to easily diagnose other  
significant disease  pathologies of the neurotropic patient, particularly  
the diabetic, while avoiding recognition of the Charcot joint entirely.   
These presentations may lead to a diagnosis of phlebitis, cellulitis,  
lymphedema, anhydrosis, in addition to the painful dysesthesias, motor  
loss, and painless ulcers.  Oftentimes the correct diagnosis is not made at  
the initial visit and several doctors may be consulted before the  
diagnosis of Charcot joint is even considered in the differential.  
  
     The surgical management of neuropathic arthropathy should attempt  
to focus, on a osseous reconstruction or realignment plan together with  
muscle balancing tendon transfer procedures.  Local treatment may  
indicate soft tissue resection with ostectomy for non-closing ulcers or  
deformities.  A surgical management of arthrodesis, arthroplasties, and  
osteosynthesis procedures, combined with dedicated physical therapy  
should have the intent of stabilizing and balancing the soft tissue  
structures.  This will help in the absorbtion and distribution of shock so  
that it might be more uniformly directed through more appropriate,  
stronger portions of the foot and leg.  Success of surgical procedures  
would be correspondingly increased.   
  
END PART THREE  
  
SEE REFERENCES PART FOUR