LESIONI DEL MENISCO

Tear of the Meniscus

Statistics

A tear of the meniscus is one of the most frequent injuries suffered by athletes.

The incidence varies according to the statistics, but on average it is equal to about 60-70 x 100,000, with a prevalence occuring in males (according to a few pubblications with a ratio, 5:1 and to others even 4:1); in terms of age, there are peaks in injuries for those between 20-30 years old (acute tear) and for those over 50 (lesions on a degenerative basis).


ANATOMY
The menisci are structured in a "C" form (with an "anterior horn", a central "body" and a "posterior horn") composed of fibrocartilage. The colagen constitues 60-70% of the dry weight of the meniscus; most of the collagen (90%) is type I; type II,III,V and VI are present in limited quantities. The elastin represents about 0.6% of the dry weight o the meniscus and protiens that are not collagen 8-13%.

The vascularization of the meniscus is very developed in the "wall" portion (or the "red zone"), while there is an absence of vascularization in the peripheral portion ("white zone"); in the central portion ("red/white"), the vascularization diminishes dramatically as you move away from the meniscul wall. This distinction is fondamental when calculating the possibility of spontaneous healing or after the suture of a meniscal lesion; the more the lesion is near the wall it is more likely that it will heal; viceversa, if the lesion is next to the free margin, it can not heal, due to the lack of streaming blood. Two menisci exist in each knee, an internal (medial) and an external (lateral). The lower surface (in contact with the tibia) is flat, while the upper surface is concave and adpats itself perfectly with the curve drawn by the femoral condyles. The menisci have two bone insertions at the tibia (one anterior and one posterior) and they are not "glued" the tibia, but partially mobile: the lateral meniscus is more mobile then the medial meniscus and is more important in stabilizing the knee. Together, the menisci act as a "seal" and a "shock absorber" between the femur and the tibia, they contribute to the stability of the knee, prevent premature degeneration of the cartilage in the joint and thus preserve the knee from arthritis.

Pathogenisis
Many factors contribute to meniscus lesions.
First of all the characteristics are: a valgus knee - "X" - causes an overload of weight on the outside part of the knee and the lateral meniscus, while the varus knee - in brackets "()" - is in the inner compartment causing the medial meniscus to be overloaded.

In both cases, this particolar anatomical axis provokes the progressive degeneration of the menisci, (medial in the varus knee, and lateral in the valgus knee) that over time lead to a lesion when combined with traumas that are not necessarilys evere, such as a banal "sqaut", wrong foot support on the ground or a slight rotation of the knee (underwieght) Often in these cases symptoms are initially scarse or irrelevant (light pain or swelling after sports activities, that dissappear after brief time with a bit of ice and a few days of treatment with antinflammatory medication), but recurs after every physical activity - even to a medium extent - or after particolar movements, when the flexion or rotation is under weight.

"Young" menisci or rather the mensici that are not degenerated are classified as a jeopardy by trauma through hyperextension (through airborne football), from sudden changes of direction, from a tackle with an opponent causing there to be unsynchronized movements between the flexion-extension and the rotation of the knee. In these cases the pain is acute, and often there is immediate swelling, and at times there is a true blocking of the joint or the unability to completely extend or flex the knee, due to a fragment ("flap") in the meniscus that blocks the rotation of the femur on the tibia. When a large portion of the meniscus is "turned inside out" at the center of the knee there is the classic break called "the bucket handle". This type of tear occurs mostly when there is a deficiet in the ACL; this is one of the reasons for which all athletes usually have the ACL reconctructed, even when the knee might seem stable.
In Sports traumatology it is very important to evaluate the risk factors that might not be purely "medical": for example, I sustain that it is fundamental that a doctor (together with the
athletic trainer) verify that the UNIFORM and EQUIPMENT are adapted to the climatic conditions and the terrain, or that there is a possibility for the athlete to HYDRATE properly (even before the sporting event).
Physical and mental fatigue are some of the first causes of athletic accidents, that is why running on a slippery terrain with shoes that are not suitable increases the fatigue and the risk of a tear; or excessive sweating, because of the hot or humid climate conditions and a uniform that does not allow transpiration of sweat, results in progressive dehydration and beyond that increases the risk of muscle injury, reduces the performance and abilities of the athlete to "reason", with and increase in the risk that they will "underevaluate" a dangerous situation.

Diagnosis and Treatment
Diagnosis is usually taken from the patient history and the objective exam (specific tests exist), but it is important to be absolutely sure with the help of an MRI.

If the exam confirms that there is a tear in the meniscus, an arthroscopy must be performed. During the intervention, one must have a complete panoramic of all of the structures of the knee, paying particular attention to the cartilage, the cruciate ligaments (anterior and posterior) and to the menisci.

Lesions in the cartilage can be treated immediately or afterward (but we will speak of these details later); the same is true for the cruciate ligaments (since there is a 5 month difference in recovery time between a meniscectomy and a reconstruction of the ACL, the patient must be prepared...).
Lesions of the menisci must be treated immediately.

If it is a "peripheral" lesion (far away from the joint wall) a "selective meniscectomy" is performed: the broken part is removed and as much of the healthy meniscus as possible is left in place. If the lesion is deep (close to the joint wall), a suture of the meniscus can be considered.

Precisely because of the fundamental importance of the menisci it is always important to try a suture. I say "try", because at times the suture does not have good results. It is worth a try, especially in large "bucket handle" lesions, where otherwise a large portion of the meniscus would be removed.

It is important that the lesion is very deep, because as we have previously explained the vascularization of the meniscus arrives only to the so called meniscus wall.

If the suture is performed in the section of the meniscus that is not vascuralized, it is destined to fail.