The knee is a complex joint, permitting flexion, extension and slight internal and external rotation. It is the point of meeting of three bones: femur, tibia and patella. The friction between the bones is minimized by synovial fluid and cartilage, covering the contacting areas. Between femur and tibia there are two more, wedge-shaped, cartilaginous structures – the menisci, whose function it is to absorb vibrations and stabilize the joint. The bones are connected to each other with ligaments, mainly the two cruciates – anterior and posterior- and the two collaterals – medial and lateral. These ligaments are also important for the stability of the joint. Tendons attach muscles to the bones, making movement possible.
If, for any reason, the articular cartilage is damaged, a condition appears, which is called osteoarthritis. The friction between the bones, that are no longer protected by the cartilage, produces the osteoarthritis symptoms: pain, swelling, stiffness, movement restriction. Osteoarthritis is the most common type of arthritis, as a rule affecting people over the age of 45.
Other factors, besides age, related to its appearance are:
– Sex – women over the age of 55 are affected more often than men
– Repeated injuries associated with loading of the joint, due to sporting activities or work-related
– Coexistence with other types of arthritis, such as rheumatoid arthritis, or certain metabolic disorders.
Diagnosis is made by clinical examination and X-rays, while in some cases magnetic resonance imaging (MRI) may be additionally indicated.
The initial therapeutic approach is conservative: weight loss recommendation, strength training, analgesics, anti-inflammatory drugs, corticosteroid injections, physiotherapy, and alternative therapies such as acupuncture.
However, in advanced situations, when there is considerable pain, the best solution is surgical treatment. In this way deformity is corrected, function is restored and pain is relieved.
The surgical techniques that can be used are mainly three:
– Total knee arthroplasty
– Unicompartmental knee arthroplasty
Total Knee Arthroplasty
This is a surgical procedure by which the entire joint – the lower end of the femur, the upper end of the tibia and the meniscus between them – is replaced by metal and plastic implants. Its application started more than fifty years ago, with constant development and improvement of materials and surgical techniques.
MINIMALLY INVASIVE TOTAL KNEE ARTHROPLASTY – MIS
minimize the injury to the soft parts of the joint upon insertion of the artificial prosthesis. This is achieved by the use of special instruments that allow manipulations through a small skin incision.
The most important benefit is that the quadriceps tendon is not cut through, as is done when the classic technique is used. Instead, it is raised with the aid of appropriate instruments. The integrity of this tendon is a prerequisite for rapid recovery after surgery, as the quadriceps is the largest muscle of the lower limb and responsible for the extension of the knee, but also very important for movements such as walking, running, jumping and squatting.
The operation is performed under either general or spinal anaesthesia (the latter affects the lower half of the body) and has a duration of about 90 minutes. At the end of the procedure, while the patient is still under the influence of anaesthesia, the nerves that innervate the knee are blocked with the use of a long acting local anaesthetic. This ensures analgesia without side effects for the first 24 hours. From the next day the pain is mild, due to the surgical technique, and can be effectively treated with simple analgesics.
Summing up, the benefits of soft tissue protection are:
– minimal blood loss – 95% of the patients do not need transfusion
– postoperative pain is significantly reduced compared to conventional techniques
– greater range of postoperative movement
– immediate mobilization. The patient can stand up on the first postoperative day, and on the fourth day he is ready to be released from hospital
– The length of time that the patient needs to have physiotherapy at home is limited by half, so that about a month later, the patient is ready to return to normal everyday activities such as walking or driving, and to work.
UNICOMPARTMENTAL KNEE ARTHROPLASTY
The knee joint comprises three compartments: inner (medial), outer (lateral) and patellofemoral. It often happens, that knee arthritis does not affect all parts of the joint simultaneously, instead it appears in only one compartment, due to local injury of bone and cartilage. For example, in patients with valgus (X-shaped) knees, degenerative lesions affect the outer compartment, while in patients with valus (O-shaped) knees the inner compartment is more often affected. In this case, as in the case of avascular necrosis of one of the two femoral condyles, replacement of only one – the damaged- part of the joint, with an operation known as unicompartmental knee arthroplasty may be advisable, under certain conditions, which we will mention later. During this procedure, the damaged surface is replaced by metal and plastic implants, while the healthy part of the joint (cartilage, ligaments, bone) is kept intact. This has some important advantages:
– Minimal invasiveness
– Small incision
– Zero blood loss
– Minimal postoperative pain
– Faster recovery
– Immediate weight bearing
– Better range of motion postoperatively
Requirements for a unicompartmental arthroplasty to be indicated are
– arthritis affecting only one part of the joint
– the ligaments are functional
– There has been no previous menescectomy in the other compartment
– there is no significant knee stiffness
– there is no inflammatory arthropathy, such as rheumatoid arthritis/p>
Preoperative control includes simple x-rays and MRI of the joint. Duration of surgery is about 1-1,5 hours and hospitalization 2-3 days. The life span of a unicompartmental arthroplasty, based on present experience, is 10-15 years. For this reason, it is best avoided in young patients, for whom osteotomy is preferable. However, age is not a strict contraindication, as a unicompartmental permits delaying of a total knee arthroplasty, with excellent quality of life in the meantime.
CORRECTIVE KNEE OSTEOTOMY
Corrective knee osteotomies are another alternative for treatment of initial stage osteoarthritis, affecting a single joint compartment (inner or outer). They are applied in young, active patients (usually less than 50 years of age), in whom total knee arthroplasty is expected to have a shorter life span compared to older people, due to greater strain of the joint. After a detailed pre-operative check (including simple x-rays and / or axis measurement of the lower limbs with a CT scan), the placement of osteotomy and its type will be decided. In general, in cases of osteoarthritis of the inner compartment (valus knee) the osteotomy is placed in the tibia (either on the outer surface with removal of a wedge of bone, or on the inner surface with bone dilation), while in osteoarthritis of the outer compartment (valgus knee) the osteotomy is placed on the femur (either on the outer surface with dilation of the bone or on the inner surface with removal of a wedge). Once the desired bone axis correction has been achieved, it is stabilized with a special metal plate.
Correction of the axis results in a better distribution of loads between the joint compartments. Thus, the progression of osteoarthritis is slowed down and total arthroplasty only becomes necessary after many years, while a good bone substrate has been maintained.