Difference between revisions of "Wound Healing Inhibition Factors - Donkey"

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Chronic inflammation can be a direct cause of delayed healing or can be an effect of delayed healing.
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{{review}}
  
Although transition through the chronic inflammatory stage is almost
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In clinical practice healing can be achieved in one of three ways:
inevitable in naturally occurring wounds healing by [[Healing Fundamentals - Donkey#Secondary or second intention healing|second intention]], it is the most undesirable event in the healing continuum.
+
* Primary or first intention healing.
Factors that will adversely affect wound healing are described below. The factors listed should always be considered prospectively when an acute wound is being assessed and retrospectively to seek an explanation for possible chronic non-healing wounds. In this way immediate measures may encourage healing and removal of long-standing complications may
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* Secondary or second intention healing.
then encourage natural healing to proceed.  
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* Delayed primary healing.
  
==1. Infection/infestation==
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==Primary or first intention healing==
[[Image:Infected injection abscess.jpg|right|thumb|250px|<small><center>Infected injection abscess (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
 
[[Image:Infected wound after cleaning.jpg|right|thumb|250px|<small><center>Infected wound after cleaning (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
 
Infected wounds certainly heal slower than uninfected ones. Depending
 
on the circumstances, the species of bacteria will vary. For example Gram-negative
 
species from faecal contamination will often infect a wound on
 
the foot or distal limb. [[:Category:Staphylococcus species|Staphylococcal]] and [[:Category:Streptococcus species|Streptococcal]] infections are
 
common contaminants of skin wounds because they may be normal skin
 
commensals.
 
  
During the first few hours after wounding bacteria will not be adherent
+
This is the mechanism that occurs when the edges of a wound can be closely
to the wound and so the wound is considered to be contaminated. Only
+
apposed. Most surgical wounds rely upon this mechanism. In a non-infected
once they adhere and start to replicate is the wound described as infected.
+
surgical wound, healing is reliably accomplished in a predictably short time
Once bacteria are established within the wound they are more difficult to
+
(usually 7 to 14 days).
remove/control and will inevitably have a harmful effect on healing.
 
  
Bacterial species (such as [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas'']], [[Bacillus species|''Baccillus'']] or [[Proteus|''Proteus'']] as well as
+
Elective surgical wounds are probably the current ‘gold standard’ of
some fungi) that produce collagenase (or other destructive) enzymes have
+
wound management, but there are major differences between surgical
a profound effect on healing by destruction of the collagen matrix, and so
+
wounds and accidental injuries (see Table 1 and Table 2 below) and so there are
the inflammatory response cannot effectively close the wound. Infection
+
almost inevitable differences in healing between the surgical situation and
with ''[[Staphylococcus aureus]]'' can cause pyogranuloma within the wound site.
+
the accidental wound.
Clinically this resembles both granulation tissue and [[Sarcoid - Donkey|sarcoid]].
+
[[Image:Wounds table.jpg|center|thumb|450px|<small><center>(Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
 +
[[Image:Table healing.jpg|center|thumb|450px|<small><center>(Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
  
Parasitic and fungal infections can occur under particular circumstances.
+
In primary wound healing, the various tissue structures involved are
Infestation, for example, with [[Spirurids - Donkey|''Habronema musca'']] or the larvae of certain
+
managed by suturing to restore very close normal anatomical relations. The
[[Blowfly Strike|flies (myiasis)]] retards healing. The larvae of ''Lucilia sericata'', however, have
+
underlying tissues are closed carefully to minimize dead space, provide good
been found to have a beneficial debriding effect in some wounds under
+
support for the skin wound itself and to restore function as far as possible.
controlled conditions (Mulder, 1989), but others can be highly destructive
+
Although in most cases this will involve closure of the wound by sutures
(e.g. ''Calliphora spp.'' and ''Sarcophaga spp.'').
+
or staples, this is not a prerequisite. Close apposition of the margins of the
 +
wound using adhesive tabs or even simply by bandaging in a suitable fashion
 +
may have the same effect and may indeed be considered to be advantageous
 +
in that there is no foreign matter in the wound. Minimal granulation tissue
 +
formation and epithelial migration are required and so the wound heals
 +
rapidly. Usually within seven to ten days the wound margin is sufficiently
 +
strong to permit removal of skin sutures.
  
Infection of any sort should be minimized by rapid attention to
+
Few accidental/ traumatic wounds are amenable to this approach because
a wound and by appropriate use of topical or systemic antimicriobial
+
there are almost always some complicating factors. Where it is possible
agents (see protocol below). Controlling infection can be problematic.
+
however to create a ‘surgical’ situation from a traumatic injury, wounds will
Topical [[Antibiotics|antibiotics]] and antiseptic solutions may help but will also almost
+
heal with an excellent result both functionally and cosmetically.
inevitably affect the healing process. The benefit must be carefully weighed
 
against the disadvantages and only when a clear advantage is present
 
can topical treatment be justified. Delivery of parenteral antibiotics to
 
a wound site is unpredictable; usually it is too slow and too weak to
 
achieve effective minimum inhibitory concentrations (MIC) in the wound
 
to do anything useful. Nonetheless antibiotics form a main pillar of
 
wound management.
 
[[Image:Antibiotic protocol.jpg|center|thumb|450px|<small><center>Protocol for best practice in use of antibiotics (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
 
  
==Foreign body==
+
==Secondary or second intention healing==
  
Foreign bodies (including sand or grit particles, wood or other plant matter,
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Second intention healing is the natural way for a wound to heal. Wounds
metal, glass, etc.) are one of the commonest reasons for non-healing wounds
+
too extensive or contaminated to suture, or those in which primary closure
and may be difficult to identify in a wound bed even when radiography and
+
has failed, must heal in this way.
ultrasonography are available.
 
  
All foreign matter must be removed from a wound site, but the retained
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In second intention healing, a '''healthy bed of granulation tissue is
foreign bodies may be very small, making removal difficult. These cases
+
required before epithelialisation can proceed'''. The quality of the granulation
often benefit from application of delayed primary wound healing.
+
tissue bed and the anatomical site has a strong influence on the rate of
 +
healing of the wound. Because there is a necessary delay in the development
 +
of the granulation tissue bed, there is an inevitable delay in healing.
  
Wound lavage is used to remove adherent and non-adherent bacteria
+
Major factors in the process of second intention healing are the size of
and foreign matter from the wound without compromising the physiological
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the wound, the anatomical location and the extent of '''complicating factors''':
status of the tissues. The type of fluid and the pressure of its delivery
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* Over 70% of donkey wounds are complicated by failure to heal and chronic inflammation
are critical factors. A physiologically sound fluid at body temperature is a
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* Second intention healing relies upon the inflammatory response; the longer the wound takes to heal, the greater will be the scar and the possible cosmetic and functional deficits
significant help. Fluids with tissue toxicity should not be used. To overcome
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* The anticipated problems associated with second intention healing may encourage clinicians to try to close wounds by primary union, although this can be ill-advised
bacterial adhesion, the ideal pressure is 7-10 psi.
 
  
* A 35/50 ml syringe with a 19G needle attached will deliver about 8-10 psi
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<u>Most traumatic wounds create circumstances that preclude primary
* The Mills wound irrigator is a safe and convenient wound irrigation system that can be attached to a bag of sterile saline without any difficulty or delays; the wound can be lavaged with an ideal solution at an ideal pressure
+
closure</u> and so second intention healing is a major clinical aspect of wound
 +
management in donkeys. Factors that disturb normal corrective processes
 +
inevitably complicate and delay wound healing. Early recognition of healing
 +
difficulties allows prompt correction; ideally factors that will result in
 +
non-healing should be recognized pre-emptively at the time of wounding,
 +
but inevitably some will not be apparent until later and possibly when the
 +
wound has failed to heal.
  
Once the wound is clean and free from any contamination it can be treated
+
The owner of a donkey with one or more of these factors can be given
according to its [[Wound Types - Donkey|type]].
+
rational advice on the likely prognosis and the time-scale for healing. Most
 +
non-healing wounds are preventable by suitable management in the early
 +
stages after injury and others are understandable or predictable. Failure
 +
to recognize potential reasons for failure of healing in a fresh wound, or
 +
delayed presentation, mean that the wound will become chronically inflamed
 +
and so the healing process will be unnecessarily prolonged.
  
==Necrotic tissue==
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==Delayed primary healing==
  
Necrotic/devitalized tissue of any type (including bone, tendon, ligament,
+
This is a useful procedure that combines the early stages of second intention
skin, connective tissue or muscle) retards healing significantly. Often it is
+
healing with a primary intention healing after a few days. It is applicable to
not possible to identify what tissue is viable and what is not in an acute
+
a few wounds but it is a very rewarding process. If closure is delayed for
traumatic wound, but natural demarcation usually becomes more obvious
+
72 to 96 hours, only a minimal risk of infection exists. The method allows
with time. Although in most cases demarcation of devitalized and necrotic
+
contaminated wounds in which immediate closure may lead to infection to
tissue is a natural part of the healing process, in some cases necrotic tissue
+
heal faster than would be the case for second intention healing.
is slow to manifest. For example, tendon, ligament and bone are often slow
+
The wound is '''initially cleaned and debrided, but is not closed'''. After a
to exhibit patent non-viability and so it may be some weeks or even months
+
variable time (usually two to four days), the wound is '''surgically debrided to
before the necrotic tissue is obvious. Where these tissues are involved in a
+
remove any demarcated tissues and closed by suture as for first intention'''
wound, slow healing and complications can be expected.
+
healing. There is an inevitable delay in the healing process but, where it
 +
is applicable, the healing time is usually shorter than second intention
 +
healing.
  
Careful debridement of all non-viable tissue at the initial stages of a
+
The '''clinical advantages'' of delayed primary healing are considerable:
wound produces a significant benefit and positively aids healing – provided
+
* The wound can be assessed for causes of failure of healing at various stages, allowing the best time for closure to be chosen
of course that the non-viable tissue is recognisable. The key objective of
+
* Acute inflammatory responses and natural debridement can take place before it is ‘driven’ towards healing without the development of a difficult and prolonged chronic inflammatory process
acute wound management is the removal of non-viable tissues, foreign
 
matter and bacteria, and the conversion of the wound to ‘surgical status’.
 
Such an approach will minimize the healing time. However, there are
 
circumstances when removal of tissue must be very carefully considered.
 
For example, no skin should be removed from wounds involving the eyelids
 
because the consequences of deficits are serious.
 
  
Chronic wounds also benefit from surgical debridement; removal
+
The '''disadvantages''' include the need for repeated procedures and an inevitable increase in scarring when compared to first intention healing, even when the time delay is relatively insignificant.
of necrotic tissue, and gross infected granulation tissue encourages the
 
production of a healthy granulation tissue bed that has a maximal chance of
 
healing. Repeated surgical debridement may be needed if the demarcation
 
between healthy and non-healthy tissue is not immediately clear.
 
 
 
==Movement==
 
 
 
Movement at the site or in the attached tissues delays healing. In some cases
 
the threat of movement is obvious. For example wounds involving the digital
 
flexor tendons often fail to heal because the tendon continues to move at
 
every step. Movement over joints and outward excursion of the heels during
 
weight-bearing can place severe strains on the soft granulation tissue bed
 
and non-healing clefts may develop that easily become infected.
 
 
 
In the early stages of a skin wound, measures taken to limit or
 
eliminate local movement may be very helpful. It is common practice to
 
restrict movement as soon as possible by application of a firm restrictive
 
bandage (e.g. Robert Jones Bandage) or even a rigid limb cast. The value
 
of immobility cannot be overstated.
 
 
 
==Tissue deficits==
 
 
 
Wounds that are complicated by large tissue deficits will inevitably heal
 
slowly. Most wounds with tissue deficits are also complicated by disruption
 
of local blood supply.
 
 
 
Management procedures for such wounds involve reconstructive
 
surgery. Restoration and reconstruction of as much tissue as possible is
 
usually a good objective, but every decision needs to be considered as part
 
of the healing process. Moist wound healing methods involving the use of
 
hydrogels or moisture donating or preserving wound dressings will help
 
to preserve the exposed tissues and thereby prevent further ‘die-back’ of
 
the injured structures.
 
 
 
==Poor blood supply/oxygenation==
 
 
 
Blood is an essential component of the healing process. From the moment
 
of injury it plays a vital role in the repair mechanisms. Disruption of major
 
veins may have limited harmful effects on the wound, but laceration of an
 
artery may be very serious especially if (as in the case of the distal limb) there
 
is a poor or absent collateral circulation. Disruption of end-arteries can be
 
catastrophic with the development of ischaemia (gangrene). The lack of a
 
pulse in distal major arteries or a much lower temperature of the structures
 
distal to the injury can identify this in the early stages. '''Assessment of distal pulses''' is therefore a critical aspect of wound management, especially where
 
there is a history of major bleeding and/or an anatomical possibility of
 
arterial damage.
 
 
 
Where a skin flap is considered non-viable, but is retained as a
 
biological cover, the skin margins should probably not be sutured because
 
the disruption/dehiscence of the wound will have an adverse effect on
 
the proximal edge of the wound. It is common practice to suture the skin
 
flap slightly distal to the original wound line so that the flap has no tension
 
and primary contraction can be tolerated. Naturally the wound must be
 
surgically clean before the flap is placed over the wound site. Once the
 
flap has become necrotic and is serving no useful purpose then it can be
 
removed and the wound dealt with accordingly.
 
 
 
Oxygen is a vital part of the wound repair process. Anaerobic conditions
 
may arise if the wound contains both a disrupted blood supply and an
 
enclosed surface. Puncture wounds are notorious for the development of
 
these conditions and this provides an ideal circumstance for some of the
 
most serious [[:Category:Clostridium species|Clostridial infections]]. [[Clostridium tetani|''Clostridium tetani'']] is the classic anaerobic
 
wound contaminant and is widely feared. [[Penicillins|Penicillin]] is highly effective
 
against ''Clostridium spp.'' bacteria and there is no rationale for using any other
 
antibiotic. A fully vaccinated donkey will not contract tetanus because
 
vaccination is highly effective.
 
 
 
Wounds with impaired oxygen delivery require careful management
 
to eliminate anaerobic conditions and encourage a good oxygen delivery
 
through angiogenesis. The health status of the donkey with respect to
 
anaemia and cardiovascular function must be considered.
 
 
 
==Repeated trauma==
 
[[Image:Friction wound.jpg|right|thumb|250px|<small><center>Friction wound (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
 
[[Image:Flushing a friction wound.jpg|right|thumb|250px|<small><center>Flushing a friction wound with saline (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
 
[[Traumatic Skin Disorders - Donkey|Repeated trauma]] to a wound site is a common cause of failure of wound
 
healing in donkeys. Direct trauma from tack or harness is a common
 
feature of wounds that arise directly from this in the first place and is a
 
particularly common feature of wounds in working animals with ill-fitting
 
or inappropriate harness.
 
 
 
The management of such wounds centres on elimination of the repeated trauma. Alteration of the type of use or the tack arrangements may be just as helpful as any sophisticated wound management system and dressings.
 
 
 
==Local factors==
 
 
 
Each wound will have local factors that may either be a valuable aid in the
 
process of healing or may have potentially harmful effects. Local exudation
 
and accumulation of wound exudate and other body fluids in the wound
 
site may be important inhibitors of normal wound healing. Some significant
 
local factors that inhibit healing include:
 
* Excessive tension in the margins of the wound (often due to incorrect suturing techniques)
 
* Accumulated exudate/dead space/pocketing
 
* pH variations (usually alkaline). Ideally the pH of a wound should be around normal physiological pH or very slightly acidic (i.e. between pH 6.5 and 7.0). Alteration of the pH of a wound site is often a consequence of infection or wound dressings and solutions. A physiological state should be maintained as far as possible unless there are specific and defined reasons to alter this, for example, [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas spp.'']] infection, where a more acidic environment will help control the bacterial replication.
 
* Poor surface oxygenation (this can be a result of dressings but more often is due to abnormal biofilms over the wound site that reduce surface gas exchange)
 
* Low or high temperature
 
* Low humidity (desiccation) or over hydration (maceration)
 
 
 
These factors may be more or less easily identified but every wound
 
should be critically assessed to see if any of them could or will result in
 
reduced healing. Measures to correct the problem will involve specific local
 
management of the wound.
 
 
 
==Poor nutritional and health status==
 
 
 
The health status of the animal itself is a vital part of the healing process.
 
A healthy, well nourished and fit animal will always heal better than one that
 
has concurrent disease or malnutrition. Poor body condition is a common
 
and serious problem in many parts of the world where there are working
 
horses, mules and donkeys. Old age, malnutrition and overwork is often
 
complicated by other factors that retard healing. Even a modicum of rest
 
and nutritional improvement usually has a dramatic positive effect and so
 
this should be encouraged.
 
 
 
==Iatrogenic factors/idiopathic failure==
 
 
 
All physiologically unsound materials are unacceptable in modern
 
wound management practice. The concept of physiological compatibility
 
should be the overriding sentiment when dealing with a wound and any
 
non-physiological substance must have a distinct clinical advantage to
 
compensate for the certain physiological harm.
 
 
 
One of the commonest iatrogenic inhibitors of wound healing is the
 
use of harmful chemicals. There are no truly bland chemicals! And there is
 
certainly no place in modern wound management for strong or weak acids
 
or caustic chemicals. Over-strength antiseptics can be just as harmful as the
 
more obvious ‘bad’ solutions and applications.
 
 
 
==Genetic factors==
 
 
 
Individual horses (and genetic lines) heal less well than others. Larger
 
horses heal less efficiently than ponies, especially in the distal limb regions.
 
Horses with [[Genetic and Developmental Skin Disorders - Donkey|congenitally weakened skin]] (e.g. hyperelastosis cutis/Erlos-Danloss Syndrome) have fragile skin that is more easily traumatized than normal,
 
and wound healing may be very protracted. Most of these congenital
 
conditions are very rare but should be considered when a horse or donkey
 
consistently fails to heal and/or is ‘liable to trauma’ that consistently fails
 
to heal for no apparent reason.
 
 
 
==[[Sarcoid - Donkey#Cell Transformation|'''Cell transformation/sarcoid''']]==
 
  
 
==References==
 
==References==
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|linkpage =Wound Management - Donkey
 
|linktext =Wound Management - Donkey
 
|linktext =Wound Management - Donkey
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|rspace={{Donkey}}
 
|pagetype=Donkey
 
|pagetype=Donkey
 
}}
 
}}
{{infotable
 
|Maintitle = [[Sponsors#The Donkey Sanctuary|This section was sponsored and content provided by '''THE DONKEY SANCTUARY''']]
 
|Maintitlebackcolour = B4CDCD
 
}}
 
[[Category:Donkey]]
 
[[Category:Wound_Management_-_Donkey]]
 

Revision as of 11:39, 20 February 2010


In clinical practice healing can be achieved in one of three ways:

  • Primary or first intention healing.
  • Secondary or second intention healing.
  • Delayed primary healing.

Primary or first intention healing

This is the mechanism that occurs when the edges of a wound can be closely apposed. Most surgical wounds rely upon this mechanism. In a non-infected surgical wound, healing is reliably accomplished in a predictably short time (usually 7 to 14 days).

Elective surgical wounds are probably the current ‘gold standard’ of wound management, but there are major differences between surgical wounds and accidental injuries (see Table 1 and Table 2 below) and so there are almost inevitable differences in healing between the surgical situation and the accidental wound.

(Image courtesy of The Donkey Sanctuary)
(Image courtesy of The Donkey Sanctuary)

In primary wound healing, the various tissue structures involved are managed by suturing to restore very close normal anatomical relations. The underlying tissues are closed carefully to minimize dead space, provide good support for the skin wound itself and to restore function as far as possible. Although in most cases this will involve closure of the wound by sutures or staples, this is not a prerequisite. Close apposition of the margins of the wound using adhesive tabs or even simply by bandaging in a suitable fashion may have the same effect and may indeed be considered to be advantageous in that there is no foreign matter in the wound. Minimal granulation tissue formation and epithelial migration are required and so the wound heals rapidly. Usually within seven to ten days the wound margin is sufficiently strong to permit removal of skin sutures.

Few accidental/ traumatic wounds are amenable to this approach because there are almost always some complicating factors. Where it is possible however to create a ‘surgical’ situation from a traumatic injury, wounds will heal with an excellent result both functionally and cosmetically.

Secondary or second intention healing

Second intention healing is the natural way for a wound to heal. Wounds too extensive or contaminated to suture, or those in which primary closure has failed, must heal in this way.

In second intention healing, a healthy bed of granulation tissue is required before epithelialisation can proceed. The quality of the granulation tissue bed and the anatomical site has a strong influence on the rate of healing of the wound. Because there is a necessary delay in the development of the granulation tissue bed, there is an inevitable delay in healing.

Major factors in the process of second intention healing are the size of the wound, the anatomical location and the extent of complicating factors:

  • Over 70% of donkey wounds are complicated by failure to heal and chronic inflammation
  • Second intention healing relies upon the inflammatory response; the longer the wound takes to heal, the greater will be the scar and the possible cosmetic and functional deficits
  • The anticipated problems associated with second intention healing may encourage clinicians to try to close wounds by primary union, although this can be ill-advised

Most traumatic wounds create circumstances that preclude primary closure and so second intention healing is a major clinical aspect of wound management in donkeys. Factors that disturb normal corrective processes inevitably complicate and delay wound healing. Early recognition of healing difficulties allows prompt correction; ideally factors that will result in non-healing should be recognized pre-emptively at the time of wounding, but inevitably some will not be apparent until later and possibly when the wound has failed to heal.

The owner of a donkey with one or more of these factors can be given rational advice on the likely prognosis and the time-scale for healing. Most non-healing wounds are preventable by suitable management in the early stages after injury and others are understandable or predictable. Failure to recognize potential reasons for failure of healing in a fresh wound, or delayed presentation, mean that the wound will become chronically inflamed and so the healing process will be unnecessarily prolonged.

Delayed primary healing

This is a useful procedure that combines the early stages of second intention healing with a primary intention healing after a few days. It is applicable to a few wounds but it is a very rewarding process. If closure is delayed for 72 to 96 hours, only a minimal risk of infection exists. The method allows contaminated wounds in which immediate closure may lead to infection to heal faster than would be the case for second intention healing. The wound is initially cleaned and debrided, but is not closed. After a variable time (usually two to four days), the wound is surgically debrided to remove any demarcated tissues and closed by suture as for first intention healing. There is an inevitable delay in the healing process but, where it is applicable, the healing time is usually shorter than second intention healing.

The 'clinical advantages of delayed primary healing are considerable:

  • The wound can be assessed for causes of failure of healing at various stages, allowing the best time for closure to be chosen
  • Acute inflammatory responses and natural debridement can take place before it is ‘driven’ towards healing without the development of a difficult and prolonged chronic inflammatory process

The disadvantages include the need for repeated procedures and an inevitable increase in scarring when compared to first intention healing, even when the time delay is relatively insignificant.

References

  • Knottenbelt, D. (2008) The principles and practice of wound mamagement In Svendsen, E.D., Duncan, J. and Hadrill, D. (2008) The Professional Handbook of the Donkey, 4th edition, Whittet Books, Chapter 9


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