What kind of cartilage makes up the meniscus
Meniscus Damage and its Treatment
The meniscus of the knee joint is a fiber cartilage made of collagen fiber bundles and has a buffering and stabilizing function between the thighbone (femur) and the shinbone (tibia). The meniscus of the knee joint is divided into the larger C-shaped, less mobile inner meniscus, and the smaller, almost circular, more mobile outer meniscus. From an epidemiological point of view, men are affected somewhat more frequently; non-gender specific, there are around 70 meniscus lesions per 100,000 people per year. The ratio of internal to external meniscus injuries is about 5: 1. On the one hand, meniscus lesions can be caused by an accident (e.g. due to shearing off when the knee joint is twisted), since the meniscus is mainly stressed by turning the knee joint in a bent position. On the other hand, older patients often show wear-related, so-called degenerative meniscus tears. A meniscus tear develops here without an adequate accident event. Meniscus tears can occur in the anterior, posterior and central parts. In the case of meniscus tears, a distinction is made between longitudinal, basket-handle, flap, transverse, radial and horizontal tears.
In the anamnesis (history) of meniscus injuries, pain at the level of the knee joint gap during or after exercise, with overstretching or forceful flexion of the knee joint. This can also lead to joint blockages in the form of (resilient) extension or flexion inhibitions. In addition, recurrent joint effusions are an indirect sign of possible meniscus injuries.
|MRI of the knee joint: tear of the lateral meniscus posterior horn|
After the physical examination with special meniscus tests, an X-ray image of the knee joint in two planes can be performed as a basic diagnosis in the case of a previous injury in order to rule out a bony injury. Here, narrowing of the joint space can also be detected, which can give the examiner an indication of meniscus or cartilage wear. The menisci themselves are radiolucent and can only be seen on x-rays in the presence of meniscus lime (chondrocalcinosis).
However, the method of choice for detecting meniscus injuries is magnetic resonance imaging (MRI, magnetic resonance imaging). The MRI allows a good assessment of the menisci and possible accompanying injuries (cruciate ligaments, collateral ligaments, cartilage) with an accuracy (sensitivity) of approx. 95% (see figure).
In contrast to X-rays and computed tomography (CT), MRI does not use ionizing radiation and is therefore harmless to the human organism.
The goals of treating meniscus lesions are, on the one hand, to eliminate the symptoms and restore joint function. On the other hand, the stable and functional meniscus tissue should be spared and the marginal ridge preserved. The aim here is to prevent or delay premature cartilage wear.
Conservative (non-surgical) therapy:
In the case of small, rather asymptomatic meniscus lesions, which, for example, are an incidental finding in the MRI, conservative therapy may be possible. The conservative measures include the temporary reduction of the load with the help of forearm crutches and physiotherapy therapy, such as proprioception and coordination training and muscle building. In addition, anti-inflammatory pain relievers (e.g. diclofenac, ibuprofen) are recommended to alleviate acute symptoms. Spontaneous healing of small, stable traumatic tears close to the base is theoretically possible, but not to be expected in the case of degenerative (wear-related) lesions, as these progress. The conservative measures are rarely successful here.
Arthroscopy of the knee joint: meniscal tear
In the case of symptomatic meniscus lesions with pain, extension or flexion inhibitions, joint effusion and / or accompanying injuries, surgical therapy should be carried out. Meniscus surgery is a domain of arthroscopic surgery (= keyhole technique). All meniscal interventions today should be performed arthroscopically (see illustration).
It depends on the type, location and blood flow of the meniscus tear, whether the meniscus can be sutured or whether the torn area has to be removed (so-called partial meniscus resection). Fresh meniscus tears in the well-perfused meniscus base can be reattached (refixed) directly or with the help of special meniscus suture systems (suture anchors) (see illustration). Only partial meniscus resection can be performed in areas with poor or no blood supply, as healing after suturing does not take place here.
Arthroscopy of the knee joint: meniscus refixation with suture anchor
The treatment of extensive meniscus damage is recommended, as a torn meniscus leads to an early destruction of the articular cartilage and, as a result, to osteoarthritis of the knee joint.
If the entire meniscus has been destroyed or several partial removals have already taken place, there is the option of meniscus transplantation or insertion (implantation) of an artificial meniscus, which can be performed simultaneously as part of knee arthroscopy. The meniscus implant consists of a three-dimensional collagen framework and is immunologically ineffective (see illustration).
Meniscus graft in various sizes
|Arthroscopy of the knee joint: implantation of a meniscus graftit|
The graft, adapted to the size and configuration of the defect, is inserted through a mini-open access through one of the arthroscopic portals and then sutured to the healthy parts of the meniscus with anchor sutures as with meniscus refixation (see illustration).
In the further course of the meniscus transplantation, the body's own cells grow into the fiber structure to form a collagen matrix and ultimately a replacement meniscus. The indication for meniscus transplantation, however, must be viewed very strictly and is reserved for young, active patients with an intact marginal ridge.
Partial meniscus removal (resections):
In the case of partial resections of the meniscus, postoperative immobilization of the knee joint is usually not necessary. However, first a pain-adapted load on forearm crutches with thrombosis prophylaxis should be carried out for about 2-3 days. Subsequently, a load up to full load is allowed. Physiotherapy to improve mobility, function and muscular strengthening of the affected knee joint is permitted from the first postoperative day.
In the case of a meniscus suture, an initially restricted mobility orthosis must then be placed on the knee joint in order to restrict the range of motion of the knee joint and thus the force during the rotary sliding movement. This is followed by a fixed treatment regimen with the leg coming into contact with the ground on forearm crutches with thrombosis prophylaxis for a further six weeks so that the sewn meniscus has the opportunity to grow back onto the intact meniscus parts (week 1 + 2 extension / flexion 0/0/30 °, weeks 3 + 4 0/0/60 °, week 5 + 6 0/0/90 °). From the 7th week the movement is released and the load can be increased slowly up to full load. Isometric exercises to strengthen the muscles are allowed with physiotherapy immediately after the operation.
Meniscus transfer / implantation:
Even with a meniscus transplant, a fixed postoperative treatment regimen with knee joint orthosis and floor contact of the leg on forearm crutches and thrombosis prophylaxis must be adhered to for six weeks in order to be able to ensure healing of the artificial meniscus (week 1 + 2 extension / flexion 0/0/20 °, week 3 +4 0/0/40 °, week 5 + 6 0/0/60 °). From the 7th week onwards, movement is cautiously released and the load can be increased slowly up to full load. Isometric exercises to strengthen the muscles are also permitted directly postoperatively with physiotherapy.
Arthroscopic partial resections of the meniscus can usually be performed on an outpatient basis (admission and surgery in the morning, discharge postoperatively in the afternoon). In elderly patients with severe secondary diseases, meniscus sutures or meniscus transplantation, a short inpatient stay of 1 to a maximum of 3 days is often advisable.
Chances of Success:
The chances of success with partial meniscus resections are consistently positive with up to 95% subjectively and functionally good to very good results. Negative prognostic factors after partial meniscus resections are pre-existing chronic instability of the knee joint, accompanying damage to the articular cartilage, the extent of the loss of meniscus substance as well as existing leg axis deformities, e.g. pronounced bow or knee positions. A final result after meniscus suturing or meniscus transplantation can only be assessed one year postoperatively by means of an MRI control. The success rate of meniscus transplants on the outer meniscus is generally to be classified as higher than that on the inner meniscus. If the meniscus graft heals without problems, the risk of osteoarthritis can be reduced.
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