Total Joint Replacement

Hip Joint

Hemi-arthroplasty for a hip joint usually involves replacement of the ball in this ball and socket joint. This procedure is very infrequently used for treatment of a symptomatic, arthritic hip joint and most commonly employed in treatment of a displaced femoral neck fractures.
Newer hemi-arthroplasty implants have replaceable parts and can be, if needed, later converted from a hemi-arthroplasty to a total hip replacement (please see below).

Hip resurfacing is based on a concept which is very similar to the concept of a tooth crown. On the side of the femur thfe ball is not replaced but covered with a cap. This is not a new procedure unlike some people are led to believe. It has been used in one form or the other since early 20th century. The biggest improvement for this implant has been in development of new materials and new manufacturing processes. This technique recently became popular for younger and more active patients, but there are significant limitations in the ability to correct deformities, availability of strong bone to support the cap and increased byproducts of metal shavings in the blood stream. The long term advantage of this procedure over the modern total hip replacement has not yet been proven.

Hip replacement Left: X-ray of the pelvis after both hips replaced by prosthetic implants. Right: Hip replacement

Total Hip Replacement is the most widely used procedure for treatment of advanced painful hip joint destruction. Much advancement was made in the designs of the implants, fixation options of the implants to the bone, implant and materials and the bearing surface materials.

The implants can be fixed with and without cement. In the past most of the joint implants were cemented into the pelvic and thigh bones, however over the past twenty years biologic or “cementless” (without the use of the cement) fixation of the implants became progressively more popular. Until recently cementless implants were reserved for the younger patients (< 60 years old) mainly because it was believed that the bones of the older patients (> 65years old) did not have potential for the biologic fixation, cementless fixation required protective weight bearing and the cemented prosthesis were more expensive. On the other hand it was observed that the use of cement was not infrequently associated with potentially concerning drop in blood pressure during the surgery, especially in older patients, and an increase in postoperative confusion. Also if the hip implants had to be revised, removal of cement usually resulted in more extensive procedures, an increased bone loss when compared with the cementless implants revision.

Knee Joint

Arthroscopic surgery most commonly used in patients with mild to moderate arthritis for removal of portions of torn menisci. It can also be used for removal of loose fragments of cartilage or bone similarly to hip joint. The procedure can be very effective in improving the symptoms.

Knee anatomy Knee Anatomy

Unicompartmental Joint Replacement (replacement of only one compartment of the knee joint) was available before the total knee replacements more the 30 years ago. It was minimally used in the US over the past 25 years but remained very popular in Europe. With improvements in the implants and the instrumentation as well as the current trend to replace only damaged portions of the joint, the use of this type of implant dramatically increased in the US during the past 5 years. The surfaces of the femur and the tibia are replaced only in the damaged portion of the knee joint with metal parts and either fixed or mobile plastic spacers is placed between the metal parts.

Three knees Partial knee replacement

Total Knee Replacement (TKR) has become the most frequently performed joint replacement procedure. There has been significant improvement in the implant design, implant materials and surgical techniques for the TKR. The weight bearing surfaces of the joint are replaced with metal components and a polyethelyn insert is placed to decrease the friction.

Knee replcement x-rays Knee Replacement x-rays

Computers and Robots
Computer navigation and “robot assisted” techniques for total knee replacement had been developed. These techniques are promising; however they had not yet proven to improve the functional outcome of the TKR. Currently the use of this equipment usually results in prolonging the surgical time for the primary TKR. There also is an increased risk of fractures through the holes drilled for the placement of extra pins for the computer navigation. The risk of infection may also be increased due to longer procedure time and presence of extra equipment and personnel in the operating room. These technological advancements may prove themselves very useful when a TKR needs to be redone.

Source: “Everything You Ever Wanted to Know About Shoulder, Hip and Knee Arthritis but Didn't Know What to Ask” by M.D. Alexander D Rosenstein, M.D., William D Ratnoff, M.D. and Stehpen S. Yang.