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Mechanical Hyperkeratosis: Let the Corn and Callus Do You No Harm!

Submitted by on January 14, 2015 – 7:47 PM

cornscallusesHyperkeratosis  is  a  normal  defensive  response  of  the  skin,  which  becomes  pathologic  when  the  callus  or  corn  grows  so  large  that  it  becomes  the  source  of  symptoms.

Abnormal  mechanical  stresses  on  the  skin  will  result  in  the  formation  of  an  accumulation  of  several  horny  layers  of  epithelium  (hyperkeratosis). 



A  corn  is  a  confined  hyperkeratotic  lesion  with  a  central  conical  core  of  keratin  that  causes  pain  and  inflammation.  The  conical  core  in  a  corn,  which  is  a  thickening  of  the  stratum  corneum,   is  a  protective  response  to  the  mechanical  trauma.  This  central  core  distinguishes  the  corn  from  the  callus.



A  callus  is  a  broad-based  or  diffuse  hyperkeratotic  lesion  of  relatively   even  thickness,  usually  found  under  the  metatarsal  heads  at  a  site  of  friction,  irritation,  and  pressure.  Unlike  corns,  the  margins  of  a  callus  are  undefined.  They  are  rarely  painful  and  are often  larger  than  corns.



Abnormal  mechanical  stresses  can  result  from  a  variety  of  intrinsic  factors  (bony prominences  or  hammertoe  deformities)  or  extrinsic  factors  (tight shoes,  irregularities  within  the  shoe,  or  high  activity  levels).  As  mechanical  stresses  on  the  skin  increase,  the  body  attempts  to  protect  irritated  skin  by  forming  a  hyperkeratotic  lesion,  such  as  a  corn  or  a  callus;  however ,  this  lesion  will  increase  the  pressure  in  a  tight  shoe,  thus  creating  a  vicious  cycle:  increased  pressure  increases  the  formation  of  corns  or  calluses,  which  further  increases  the  pressure.



You  may  have  a  corn  or  callus  if  you  notice:

  • A thick,  rough  area  of  skin
  • A hardened,  raised  bump
  • Tenderness or  pain  under  your  skin
  • Flaky, dry  or  waxy  skin



Pressure  and  friction  from  repetitive  actions  cause  corns  and  calluses  to  develop  and  grow.  Some  sources  of  this  pressure  and  friction  include:

  • Wearing ill-fitting  shoes
  • Skipping socks
  • Playing instruments  or  using  hand  tools


Risk  Factors:

These  factors  may  increase  the  risk  of  corns  and  calluses:

  • Bunions: A bunion  is  an  abnormal,  bony  bump  that  forms  on  the  joint  at  the  base  of  your  big
  • Hammertoe: A  hammertoe  is  a  deformity  in  which  your  toe  curls  like  a
  • Other foot  deformities:  Certain  conditions,  such  as  a  bone  spur,  can  cause  constant  rubbing  inside  your
  • Not protecting  your    Using  hand  tools  without  wearing  gloves  exposes  your  skin  to  excessive  friction.



Hyperkeratotic lesions  are  secondary  to  increased  mechanical  stress  and  are  not  a  disease  of  the  skin.  The  principles  of  treatment  should  be  to:

  • Provide symptomatic  relief,
  • Determine the  mechanical  etiology,
  • formulate a  treatment  plan  that  includes  padding  and  modification  of  footwear,
  • consider surgery  if  conservative  measures  fail.

Symptomatic  relief:

  • A  mainstay  of  palliative  treatment  is  sharp  debridement  to  reduce  the  amount  of  hyperkeratotic  tissue.
  • A  chisel  blade  may  be  used  to  pare  down  these  lesions,  providing  almost  complete  relief  to  the  area.
  • A  pad  may  be  used  to  prolong  the  relief  provided  by  sharp  debridement.
  • For  diffuse  hyperkeratotic  lesions  that  are  not  painful,  a  pumice   stone  is  used  to  reduce  the  lesion  after  first  soaking  the  foot  in  warm  water.
  • Over-the-counter  products  that  contain  salicylic  acid  should  be  avoided  because  they  may  damage  surrounding  normal  tissues,  especially  in  neuropathic  and  immunocompromised  patients.


Therapeutic  padding  can  alleviate  the  patient’s  symptoms  by  reducing  the  amount  of  mechanical  irritation  to  the  site  of  the  corn  or  callus.

  • For hard corns: foam  pads  or  silicone  toe  sleeves  offer  the  cushioning  and  protection  needed  after  adequate  debridement  of  the
  • For soft  corns:  After  debridement  of  soft  corns,  relief  can  be  provided  by  padding  the  web  space  with  a  foam  toe  spacer  or  a  small  amount  of  lamb’s
  • for calluses:  Plantar  calluses  caused  by  weight-bearing  stresses  on   the  metatarsal  heads  may  be  relieved  or  eliminated  by  accommodative  metatarsal    padding  may  be  applied  directly  on  the  foot  or  within  the  shoe.

Foot  gear:

Most  mechanical  lesions  can  be  conservatively  managed  with  an  adequate  shoe.

  • Patients should  be  advised  to  wear  low-heeled  shoes  with  a  soft  upper  portion  and  a  roomy
  • Patients with  hammertoe  deformities  may  need  a  shoe  with  an  extra  depth  to  accommodate  hard  corns  that  often  occur  on  the  top  of  the  deformed
  • Patients with  soft  or  hard  corns  on  the  fifth  toe  may  benefit  from  a  shoe  that  has  extra


Surgery  should  concentrate  on  correcting  the  abnormal  mechanical  stresses  and  should  only  be  considered  after  conservative  measures  have  failed.

  • The goal  of  surgical  correction  of  a  hammertoe  deformity,  claw  toe  deformity,  or  mallet  toe  deformity  is  to  reestablish  a  rectus  alignment  of  a  toe  that  is  also  free  of  painful
  • Hard corns  on  the  fifth  toe  and  soft  interdigital  corns  can  be  treated  by  resection  of  the  prominent  condyles  or  excision  arthroplasty  of  the  proximal  phalanx  of  the  fifth
  • Calluses under  the  metatarsal  heads  are  best  managed  conservatively  because  metatarsal  osteotomies  have  unpredictable  results,  and  the  callous  may  transfer  to  an  adjacent  metatarsal


These   approaches   may   help   you   prevent   corns   and   calluses:

  • Wear   shoes   that   give   your   toes   plenty   of   room.
  • Use   protective   coverings.
  • Wear   padded   gloves   when   using   hand   tools.
  • Keep  hands  and  feet  moisturized.


The  formation  of  corns  and  calluses  can  be  caused  by  mechanical  stresses  from  faulty  footgear,  abnormal  foot  mechanics,  and  high  levels  of  activity.  Corns  and  calluses  result  from  hyperkeratosis , a  normal  physiologic  response  of  the  skin  to  chronic  excessive  pressure  or  friction.  Treatment  should  provide  symptomatic  relief  and  alleviate  the  underlying  mechanical  cause.  The  lesions  will  usually  disappear  following  the  removal  of  the  causative  mechanical  forces.  Most  lesions  can  be  managed  conservatively  by  the  use  of  properly  fitting  shoes  and  padding  to  redistribute  mechanical  forces.  Surgery  is  only  indicated  if  conservative  measures  fail  and  should  be  aimed  at  correcting  the  abnormal  mechanical  stresses.


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