About total knee replacement (TKR) surgery.

When is knee replacement surgery necessary?

Total knee replacement (also referred to as total knee arthroplasty) is offered to patients whose knee joint has degenerated (usually caused by arthritis). When the cartilage wears, the patient experiences pain. Sometimes cartilage completely wears away causing “bone-on-bone” articulation. There may be stiffness (loss of motion) and bow-leg (varus) deformity or knock-knee (valgus) deformity.

What does knee replacement surgery involve?

This surgery involves removing damaged bone and cartilage from the femur and the tibia and replacing with artificial joint components. The components may be attached to the bone using polymethylmethacrylate bone cement or using cementless fixation. The joint components are commonly made from cobalt chrome and polyethylene. Find out more about knee implants.

Success rates in knee replacement

Total knee replacement is generally very successful procedure with 95% satisfaction and 90% of patients experiencing a dramatic reduction in pain and a significantly increased ability to participate in activities of daily living. Patients are often able to resume activities such as walking, golf and doubles tennis. The chances of still having your total knee replacement after 12 years without having a revision procedure is 93.5%

How long will I take to recover from knee replacement surgery?

Patients are generally get up and walk within 6 hours of the surgery and stay in hospital for 3 to 5 days. The important things in the early postoperative period are to get moving and to allow the wound to heal. Moving the knee early will result in a better range of motion in the long run and getting up and walking prevents blood clots, constipation and lung problems, however, the wound at the front of the knee does need to heel. Some patients over do it and need to be slowed down a bit. It is a good idea to use crutches or a walking stick for the first 4 to 6 weeks after surgery although this is not an absolute requirement.

Knee replacement design concepts.

There are several different design classes when it comes to total knee replacement. The geometry of the articular surface is particularly important as is governs the biomechanical function of the replaced knee. Professor Walter believes better functional results are achieved by designs that allow the tibia to rotate about an axis, which is located in the medial compartment (medial pivot concept). This concept is not the most widely used by other knee surgeons. Professor Walter has used a variety of different types of medial pivot knee designs over the last 10 years based on this concept and currently uses a design that he developed with a team of surgeons from United Kingdom and Australia. Sophisticated kinematic research shows that medial pivot knees move more like the normal (unreplaced) knee, particularly with activities such as stair climbing, lungeing, pivoting and kneeling, without paradoxical forward movement of the femur in the tibia as occurs with other designs.  Clinical follow-up studies with patient reported outcomes show superior function with medial pivot knee designs. Studies in patients who have had both knees replaced with a different type of knee replacement in each knee have shown that patients prefer medially pivoting design to other design. They say things like: feels more normal; stronger on stairs; superior single-leg weight bearing; flexion stability; feels more stable overall.

 

References

1. Fluoroscopic motion assessment of stability of a medial conforming (SAIPH TM) total knee replacement. Andrew Shimmin1 FRACS, Sara Martinez Martos1 MD PhD, John Owens 2, Alex D Iorgulescu BS 3, Scott A Banks PhD 3

2. Knee arthroplasty with a medially conforming ball-and-socket tibiofemoral articulation provides better function.Hossain F1, Patel S, Rhee SJ, Haddad FS. Clin Orthop Relat Res. 2011 Jan;469(1):55-63. doi: 10.1007/s11999-010-1493-3.

3. Pritchett J W (2011) J Arthroplasty, 26:224-228