Partial knee replacement surgery involves replacing only part of the joint. A native knee joint has three compartments – medial compartment (inner side of the knee), lateral compartment (outer side of the knee) and patello-femoral compartment (behind the knee cap). If one of the three compartments is significantly worn out due to arthritis, but the other two are very well preserved, partial knee replacement can be considered. Partial knee replacement involves replacing just one compartment out of the three. The components are made of alloys of cobalt and chromium for femur and tibia and a special plastic in the middle.
– Quicker recovery in the initial post-operative phase: Initial recovery period is approximately 3 to 4 weeks in most cases as compared to 6 to 8 weeks for total knee replacement
– Better range of motion: Most patients get 120 degrees of flexion or more after a partial knee replacement as compared to an average of 100-110 degrees of flexion after total knee replacement.
– Survivorship: Average survivorship of partial knee replacement is in the range of 8-10 years. Generally after this period, either the rest of the knee joint develops progressive arthritis or components loosen/wear out, necessitating a total knee replacement surgery
– Ongoing pain/lack of full function: Some patients complain of ongoing pain or lack of full function after partial knee replacement due to some pre-existing arthritis in the other two native compartments of the knee joint.
I choose my patients very carefully for partial knee replacement in order to achieve a successful outcome. This is done by careful history taking, focussed clinical examination and by appropriate investigations. Investigations can include X-rays and occasionally MRI scans. In some cases, knee arthroscopy procedure may need to be carried out to assess the degree of arthritis in the joint and determine the suitability for partial knee replacement.
Physiologically young patients are best suited for this type of procedure; however, age is not the absolute criteria for partial knee replacement surgery.
The most commonly performed partial knee replacement involves replacing the medial compartment (inner part of the knee). Due to the biomechanics of the knee joint, medial compartment of the knee develops progressive arthritis ahead of the other two compartments in vast majority of the patients. Very occasionally, partial knee replacement of either the lateral compartment (outer part of the knee) or of the patello-femoral compartment (behind the knee cap) can be considered.
Based on how the bearing surface is fixed on to the components, partial knee replacement can be mobile bearing or fixed bearing. However, studies have not shown any significant difference in clinical outcome between the two types of knee replacement. In my practice, I use fixed bearing partial knee replacement.
Overall, partial knee replacement is a very successful operation in modern day surgery. In my practice, success rate of a partial knee replacement is around 85-90%. Pain relief and improvement in the quality of life is substantial in vast majority of patients. Partial knee replacement helps patients maintain an active life including sporting activities.
Risks of partial knee replacement include infection (around 1%), bleeding, DVT (clots in your leg), PE (clots in your lung), stiffness, loosening, wear, persistent pain (around 2-3%), need for further surgery, medical and anaesthetic complications. Precautions are taken in order to minimize all the above risks e.g. use of antibiotic prophylaxis and specialized laminar air flow theatres to minimize the risk of infection, use of blood thinning medications and mechanical methods to reduce the risk of clots, etc. Post-operative exercises are extremely important to gain/maintain good range of flexion after the surgery.
You are generally admitted to the hospital on the day of surgery. Average length of stay in the hospital is 2-3 days. During the hospital stay, a multi-disciplinary team including orthopaedic team, ward doctor, nursing staff, physiotherapist and occupational therapist, treats you. Once you and the team are happy with the progress, you are discharged from the hospital.
Post-operative mobilization includes use of walking aids like walker or crutches to begin with. You can subsequently use walking stick/s until independent mobility can be achieved. Most patients can hope to regain independent mobility after 3-4 weeks.
You can expect some swelling and redness around the wound and of the lower leg for few weeks. Generally by 6 to 12 weeks, nearly full recovery can be expected in most patients. Most patients can expect to drive around 3-4 weeks mark.
Currently, my preferred implants are PFC Sigma Higher Performance Partial Knee System (manufactured by Depuy Synthes).