Once a meniscal tear occurs, a fibrin clot forms within its margins, creating a scaffold into which angiogenesis
develops from the perimeniscal capillary plexus. The fibrin clot contains factors, such as platelet-derived growth factor
and fibronectin, that act as chemotactic and mitogenic agents for reparative cells to migrate and develop. Undifferentiated
mesenchymal cells also migrate into the clot and a fibrovascular scar develops, gradually sealing the lesion. Further inflammatory
response and angiogenesis result in healing of the lesion in about 10 weeks in the dog. It may take months or even years for
the scar tissue to change into fibrocartilage, resembling that of the meniscus. Differences between the newly formed fibrocartilage
and mature fibrocartilage are recognizable and include increased cellularity and, at times, increased vascularity in the repair
tissue.
Is Inappropriate Meniscal Surgery Often Recommended & Done?
In my opinion there are many vet surgeons out there who are much too quick to carve
off parts of a damaged meniscus when the dog would be far better off with the joint left alone to recover using its own resources.
The history of surgical intervention is instructive.
The menisci are now known to play an important role in the complex biomechanisms of the knee. But just a few decades ago doctors
believed the menisci were functionless tissue that could be removed without consequence. Surgeons routinely removed the entire
meniscus if there was any indication that it was even slightly damaged or for no reason simply as part of their standard procedure
when doing any stifle surgery. In time this resulted in crippled dogs (and people) as Degenerative Joint Disease developed
in the joints. Eventually the more observant doctors woke up to the fact that the menisci were important joint components,
and in recent years the more enlightened surgeons have become less aggressive in removing all or part of the meniscus. But
there are still many vet surgeons who cut far too much of a meniscus away. Some of these guys just can't stop themselves from
getting in there and excising something. In the course of my research, when I talked with surgeons about their approach to
dealing with an injured meniscus, I often heard "When In Doubt, Cut It Out" as a rule-of thumb they used. They won't usually
tell clients that of course.
---- The history of surgery in general is filled with examples like this of too-aggressive
surgical intervention. Never be too trusting of a surgeon. They became surgeons to cut; not to tell you no cutting is needed.
---- However, sometimes surgery to remove part of the meniscus is best. If your
dog has on-going pain and is not improving, or the joint locks up, surgery may be required. I want to caution you that
unneeded surgery may be recommended by some vets, but not leave you with the impression that the meniscus never requires surgical
intervention.
Clicking & Popping?
'Meniscal Release'?
Surgeons often do something they call "Meniscal Release" along with ligament injury
surgery. 'Meniscal Release' cuts the connection of part of the meniscus, removing it from what would be its functional
position in a normal joint. This decreases the risk of injury to the meniscus at the cost of removing the meniscus from
being a functioning part of the joint. 'Meniscal Release' has been found to be a factor in Degenerative Joint Disease.
Should we be surprised when major alterations in complex structures bring with them unexpected problems?
________________________
"...recent studies done in Germany have suggested
that meniscal release may be ineffective at reducing the incidence of late meniscal tears, and moreover, may, like a spontaneous
meniscal injury, actually result in increased arthrosis in the knee. This remains a controversial area and some surgeons are
now abandoning the practice..."
---TPLO advocate J.M. Fingeroth,
DVM, DACVS
______________________________
"...The
purpose of the meniscal release is to allow the caudal horn of the medial meniscus to move away from the medial femoral condyle
during cranial tibial translation, preventing meniscal impingement. Although meniscal release appears to be effective in reducing
the rate of postliminary [after surgery] meniscal tears, it has the adverse affect of diminishing the load transmission
and stability functions of the meniscus (Pozzi A, et al, 2006). Thus, the efficacy of meniscal
release at diminishing the rate of postliminary meniscal tears must be weighed against its adverse effects on meniscal function
when considering its use on clinical cases. ..." -- Michael P. Kowaleski DVM, DACVS
___________________
"...The
meniscus both cushions the impact of the stifle on the tibia and to degree stabilises the stifle by limiting caudal movement
of the femur on the tibia. Removing these functions by meniscal release must be a bad thing. Where the management of the cruciate
deficient stifle is by some method of tibial plateau geometry altering technique, the stifle becomes stable only under
load. The meniscus is therefore vunerable to impingement between femur and tibia when under partial load or uncontolled loading.
It is presumed that damage, if not already present, will occur. [With meniscal release] The caudal horn is sectioned
allowing it to move caudally, removing it from harm by the femur. The theory of meniscal release is based on the assumption
that no meniscus being better than a damaged (painful) one...."
____________________________________
Beware of Short-Term Solutions
Since many surgeons tend to favor short-term solutions which do not look out past six
months, removing the meniscus or doing a meniscal release may look more like a good idea to these surgeons than it would to
clients who expect their dogs to live at least several more years. A surgeon will cut away part or all of the meniscus,
or do a meniscal release, and 6 months later the dog will have improved post-surgically and will not have had the risk
of possible post-surgical injury to the meniscus. The surgeon calls avoiding that risk a good choice. But a year
later arthritic changes will have started trouble in the joint which will worsen & worsen as time goes on. The meniscus
is an important part of the joint. Removal of all or part of it, or 'release' of the meniscus sets the stage
for inevitable future arthritic changes. Many surgeons are short-term thinkers. "The patient is better 6 months
out" is success as far as they are concerned.
---- Of course there are exceptions to this surgeon sterotype I am presenting, but you
should not assume that a surgeon is looking at your dog's treatment and future in the same way you are.
*************************
Sometimes meniscal injury does require surgical intervention, but it is wisest to be cautious
and skeptical about recommendations for meniscus alteration.
