Knee and Hip Prostheses – Prof Dr Cengiz Şen

Knee and Hip Prostheses

WHAT IS TOTAL KNEE PROSTHESIS?

Total knee prosthesis is the procedure of generating a superficial joint covering the worn joint surfaces using special metal and polyethylene compounds designed for enabling pain-free joint movement. The first knee prosthesis procedure was performed in 1968. The procedure is a more successful treatment method today thanks to the developments of tecniques in surgeries, materials and design.

Who can be applied a total knee prosthesis ?

Total knee prosthesis is appropriate for patients who have uncontrollable knee pain and extreme restriction on daily activities such as walking and climbing up stairs and advanced destruction on joint cartilage although the treatment procedures such as resting, medications, physical treatment, use of walking stick and intraarticular injections have been recommended earlier. However, the preferred age is between 60-80, replacement may also be applied to younger patients diagnosed with particular diseases such as rheumatoid artritis and osteonecrosis.

How is the total knee prosthesis replaced?

A cut is made from the front part of knee under anesthesia. The worn-out cartilage tissue on the attachment surfaces of three bones(femur, tibia and patella) is cut out and removed together with a thin layer of bone and then, prosthesis compounds in proper dimensions are attached to the bone surfaces using a filling material called polymethyl methacrylate.

Thus, the joint surfaces will be covered with metal and plastic materials again. The surgery lasts in 1-2 hours. Epidural or intravenous pain control pumps are used after the surgery. The next day, knee movements are initiated and the patient is encouraged for mobilization under supervision. The patient is discharged when he/she is able to walk comfortably in the room and in the ward.

A significant relief in knee pain and significant improvements in daily activities such as walking/ climbing up stairs are provided in more than 90% of patients who undergo total knee prosthesis replacement surgery. The period for significant relief in pain and going out indepently, may vary between 4 to 8 weeks. Running, jumping and heavy work must be avoided after surgery because such activities shorten the life of the prosthesis. Driving a car will not cause any problem. Pre-existing curvature and deformity correction procedures may also be applied during the surgery and they prolong the life of the prosthesis. However, the range of motion is smaller particularly in overweight patients. The average range of motion degree is 115, therefore full squatting and performing of salaat(prayer in Islam) may not be possible after surgery. However, the techniques and designs that enable wider range of motion have been used in recent years, it may still be problematic to sit down in salaat position for the long time survival of the prosthesis.

Metal and plastic compounds of prosthesis are worn out by the time due to friction in movement. The prosthesis may detach and loosen with the response of body against tiny compounds of metal and plastic which develop due to friction. The life of knee prostheses, that are designed using proper surgical techniques and modern designs are about 15-20 years. The loose prostheses may be replaced with new prosthesis in most patients with a second surgery but the life of new prosthesis will not be as long as the former.

The Complications

The incidence of serious complications after total knee prosthesis surgery are relatively low. The most common problem is the formation of clots in vessels( deep vein thrombosis) due to the decrease in blood flow. Prophylactic treatment using blood thinners is prescribed to prevent the complication after surgery. The treatment may be lasted until 20 days if required. Initiating the knee movements and walking in early period will reduce the risk.

The risk of prosthesis infection after surgery is about 0.1 to 0.2%. The presence of infection in other parts of the body(urinary tract,teeth etc.), diabetes and other chronic diseases and over consumption of cigarette and alcohol may increase the risk. Pre-existing infections must be treated before surgery. Prophylatic antibiotic treatment is administered during the surgery and infection risk is reduced using specific precautions during the surgery. The procedures such as repeated surgeries, removal of the prosthesis and re-replacement may be required in case of prosthesis infection.

Other than above mentioned complications; wound healing problems, vascular or nerve injuries, displacement of particular compounds of prosthesis, fractures in the neighboring of prosthesis and prosthesis fracture are the other possible complications but the incidence rate is low.

WHAT IS TOTAL HIP PROSTHESIS? HOW IS IT APPLIED AND TO WHOM?

Total hip prosthesis is the procedure of generating a superficial joint by covering the worn joint surfaces using special metal and polyethylene compounds designed for enabling pain-free joint movement. The first hip prosthesis procedure was performed in early 1960s. The procedure is a more successful treatment method today thanks to developments of tecniques in surgeries, materials and design.

Who can be replaced total hip prosthesis ?

Total hip prosthesis is appropriate for patients who have uncontrollable knee pain and extreme restriction on the daily activities such as walking and climbing up stairs and advanced destruction on joint cartilage although the treatment procedures such as resting, medications, physical treatment methods, the use of walking stick and intraarticular injections have been recommended earlier. However, the patients aged between 60 and 80 are preferred, the replacement may also be applied to younger patients diagnosed with particular diseases such as post trauma artritis, rheumatoid arthritis, osteonecrosis and femoral neck fractures.

How is a total hip prosthesis replaced?

A cut is made from the lateral and posterior of hip under anesthesia. The worn-out cartilage tissue on the attachment surfaces of two bones(femural head and acetabulum) is cut out and removed together with a thin layer of bone and then, prosthesis compounds in proper dimensions are attached to the bone surfaces using a filling material called polymethyl methacrylate or using cement free methods such as press-fit.

Thus, the joint surfaces will be covered with metal and plastic materials again. The surgery lasts in 1-2 hours. Epidural or intravenous pain control pumps are used after surgery. The next day, hip movements are initiated and the patient is encouraged for mobilization under supervision. The patient is discharged when he/she is able to walk comfortably in the room and in the ward.

A significant relief on hip pain and significant improvement in daily activities such as walking/climbing up stairs are provided in more than 90% of patients who undergo total hip prosthesis replacement surgery. The period for significant relief in pain and going out indepently may vary between 2 to 3 months. Running, jumping and heavy work must be avoided after surgery because such activities shorten the life of the prosthesis. Driving a car will not cause any problem. Pre-existing curvature and deformity correction procedures may also be performed during the surgery and that will prolong the life of the prosthesis. However, the range of motion is smaller particularly in overweight patients. Full squatting and performing salaat must be avoided due to the risk of prosthesis dislocation.

The joint surfaces of prosthesis may be formed using metal, polyethylene and ceramic compounds. Those implants may worn out by the time due to friction in movement. The prosthesis may detach and loosen with the response of body against tiny compounds of metal and plastic which develop due to friction. The life of hip prostheses, which are designed by the use of proper surgical techniques and modern designs are about 20-25 years. The loose prostheses may be replaced with new prosthesis in most patients with a second surgery but the life of new prosthesis will not be as long as the former.

The Complications

The incidence of serious complications after total hip prosthesis surgery are relatively low. The most common problem is the formation of clots on veins( deep vein thrombosis) due to decrease in blood flow. Prophylactic treatment using blood thinners is prescribed to prevent the complication after surgery. The treatment may be lasted until 30 days if required. Initiating the hip movements and walking in early period will reduce the risk.

The risk of prosthesis infection after surgery is about 0.1 to 0.2%. The presence of infection in one part of the body (urinary tract,teeth etc.), diabetes and the other chronic diseases and over consumption of cigarette and alcohol may increase the risk. Pre-existing infections must be treated before surgery. Prophylatic antibiotic treatment is administered during the surgery and infection risk is reduced by applying specific precautions during surgery. The procedures such as repeated surgeries, removal of the prosthesis and re-replacement may be required in case of prosthesis infection.

Other than above mentioned complications; prosthesis dislocation, wound healing problems, vascular or nerve injuries, displacement of particular compounds of prosthesis, fractures in neighboring of the prosthesis and prosthesis fracture are the possible complications but the incidence rate is low.

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