Chapter 5
The Healing Process
Overview

Injuries to the musculoskeletal system
can result from a wide variety of
causes. Each of the major components
of the musculoskeletal system have
varying capacities to heal
Musculoskeletal Injuries

Injuries to the soft tissues can be
classified as primary or secondary:
– Primary injuries can be self-inflicted,
caused by another individual or entity, or
caused by the environment
Acute
 Chronic
 Acute on chronic

Musculoskeletal Injuries

Secondary injuries are essentially the
inflammatory response that occurs
with the primary injury
Wound healing


Fortunately, the majority of soft tissue
injuries heal without complication in a
predictable series of events
However, healing abnormalities can occur.
These abnormalities can be due to such
complications as:
– Infection
– Compromised circulation
– Neuropathy
Wound healing

Three main phases:
– Inflammatory
– Proliferative
– Remodeling
Inflammatory phase

The reaction that occurs immediately
after wounding includes a series of
defensive events that involves the
recognition of a pathogen and the
mounting of a reaction against it. This
reaction involves both coagulation and
inflammation
Inflammatory phase


Coagulation. Apart from an initial period of
vasoconstriction lasting for 5-10 minutes,
tissue injury causes vasodilation, the
disruption of blood vessels and
extravasation of blood constituents,
including platelets
The main functions of the exudate are to:
– Provide cells capable of tissue reconstruction
– Dilute microbial toxins
– Remove contaminants present in the wound
Inflammatory phase

Inflammation. Inflammation is mediated by
chemotactic substances, including
anaphylatoxins, which attract neutrophils
and monocytes
– Neutrophils are white blood cells that bind to
microorganisms, internalize them, and kill them
– Monocytes are white blood cells that develop
into macrophages, and provide immunological
defences against many infectious organisms
Inflammatory phase


The complete removal of the wound
debris marks the end of the
inflammatory process
This stage can last from 1-6 days to
longer than 6 months

Common causes for a persistent chronic
inflammatory response include:
–
–
–
–
–
–
–
–
Infectious agents
Persistent viruses
Hypertrophic scarring
Poor blood supply
Edema
Repeated direct trauma
Excessive tension at the wound site
Hypersensitivity reactions
Inflammatory phase

Clinically, during the inflammatory phase
there is pain:
– At rest
– With active motion
– When specific stress is applied to the injured
structure

The pain, if severe enough, can result in
muscle guarding, and a loss of function.
Proliferative phase

Characteristic changes during this
phase include:
– Capillary growth
– Granulation tissue formation
– Fibroblast proliferation with collagen
synthesis and increased macrophage and
mast cell activity
Proliferative phase

This phase lasts from 5 to 15 days,
and often up to 10 weeks depending
on the type of tissue, and the extent
of damage.
Remodeling phase


The remodeling phase of wound
healing involves a conversion of the
initial healing tissue to scar tissue
This lengthy phase of contraction,
tissue remodeling and increasing
tensile strength in the wound lasts for
up to a year
Remodeling phase



Imbalances in collagen synthesis and
degradation during this phase of healing
may result in hypertrophic scarring or keloid
formation
If left untreated, the scar formed is less
than 20% of its original size
Scarring that occurs parallel to the line of
force of a structure is less vulnerable to reinjury than a scar, which is perpendicular to
those lines of force
Muscle healing


The capacity of muscle for regeneration is
based primarily upon the type and extent of
injury
Broadly speaking, there are three phases in
the healing process of an injured muscle:
– The destruction phase
– The repair phase
– The remodeling phase
Ligament and tendon
healing

Healing of ligaments and tendons
generally can be broken down into
four overlapping phases:
– I. Hemorrhagic
– II. Inflammatory
– III. Proliferation
– IV. Remodeling and maturation
Articular cartilage healing


The capacity of articular cartilage for
repair is limited
The repair response of articular
cartilage varies with the depth of the
injury
Articular cartilage healing


Injuries of the articular cartilage that
do not penetrate the subchondral
bone become necrotic and do not heal
These lesions usually progress to the
degeneration of the articular surface
Articular cartilage healing


Injuries that penetrate the
subchondral bone undergo repair due
to access to the bone’s blood supply
These repairs are usually characterized
as:
– Fibrous
– Fibrocartilaginous
– Hyaline-like cartilaginous
Bone healing


The striking feature of bone healing,
compared to healing in other tissues,
is that repair is by the original tissue,
not scar tissue
Bone healing involves a combination of
intramembranous and endochondral
ossification
Bone healing

In classic histologic terms, fracture
healing has been divided into two
broad phases:
– Primary fracture healing
– Secondary fracture healing
Bone healing


Primary healing involves a direct
attempt by the cortex to reestablish
itself once it has become interrupted
Bone on one side of the cortex must
unite with bone on the other side of
the cortex to reestablish mechanical
continuity
Bone healing


Secondary healing involves responses
in the periosteum and external soft
tissues with the subsequent formation
of a callus
The majority of fractures heal by
secondary fracture healing