Partial knee replacement (medial compartment)

By
Chelsea and Westminster Hospital, The Lister Hospital
Published November 22nd, 2011  |  Last updated April 30th, 2012

This article describes a new treatment option for patients with degenerative knee joint diseases such as osteoarthritisA disease mainly of the large joints of the body, as a result of wear and tear of the surface cartilage.: partial knee replacement. This will be of help to those patients who are looking for an alternative to a total knee replacement in order to, for example, have a shorter rehabilitationThe treatment of a person with an illness or disability to improve their function and health. period.

Contents

Introduction

Partial knee replacement is a viableCapable of survival. surgical treatment option in some patients with isolated degenerative joint disease, when wear is confined to a particular area of the knee and the remainder of the articular cartilage is in good condition. Surgical treatment for degenerative conditions of the knee can include arthroscopic knee surgery (keyhole surgeryA type of minimally invasive surgery.), osteotomyA surgical procedure whereby bone is cut or broken to straighten, shorten or lengthen the bone. (cut is made in bone to improve alignment), partial and total knee replacement.

There are several types of partial knee replacement surgery including medial (resurfacing of the inner medial weight-bearing area of the knee), patellofemoral (behind the knee cap) and lateral joint replacement (outer lateral weight bearing area of the knee). The most common type of partial knee replacement surgery is medial unicompartmental resurfacing. This is where the worn surface is prepared and a metal implant is placed on either side of the medial joint with a polyethylene bearing in between.

The aims of surgery are to relieve pain and improve function with long term survival of the prosthesisAn artificial device attached to the body..

Usual symptoms

Medial compartment osteoarthritis often develops gradually and causes pain over the anteromedial aspect of the knee on weight bearing and exercise. Walking distance is often reduced with difficulty climbing or descending stairs.

X-rays will show narrowing of the joint space on the medial (inner weight bearing area) side due to thinning of articular cartilage (which normally covers the bone in joints).

What are the benefits of partial knee replacement over total knee replacement?

The main benefit of partial knee replacement is that it involves less invasive surgery with a smaller incision which results in less time in hospital and a quicker progression to functional walking. However, it still takes a minimum of six weeks for early soft tissueA group of cells with a similar structure and a specialised function. healing and resolving of surgical incision pain.

What type of medial replacement do you use?

I use the Oxford medial knee replacement which has excellent long term survival rates in the literature. The anterior cruciate ligament (ACL) is preserved which is a further advantage of partial knee replacement (allows a more physiological mechanical result).

Is everyone suitable for medial knee replacement?

No. Patients with early wear and tear of the medial aspect of the knee and an intact ACL are suitable.  Patients with very advanced wear may not be suitable and may need total knee replacement.

Is there an age limit to this type of surgery?

No. Patients in their early 40’s to 80 year olds may be suitable.

When can I start walking after surgery?

The day after surgery you will get up and fully weight bear with the physiotherapistA healh professional who specialises in physical therapies, such as exercise, massage and manipulation.. Most patients stay in hospital between 3 and 5 days.

Surgical approach

The surgical approach is a medial approach approximately 10 cm long on the medial edge of your knee cap. Dissolvable suture or clips are used to close the wound and a dressing stays on the knee for 2 weeks.

The risks of having treatment

There are small risks with all types of surgery. A regional or general anaestheticAny agent that reduces or abolishes sensation, affecting the whole body. would be required and the small risk of wound inflammationThe body’s response to injury. or infectionInvasion by organisms that may be harmful, for example bacteria or parasites. is 1% or less. You would also be given an injection or tablet to reduce the small risk of deep vein thrombosisObstruction of one of the deep veins, often in the calf, by a blood clot. Often abbreviated to DVT..

Post-treatment follow up

Clinical review is necessary at two weeks to remove dressings and assess early function of the knee. Further reviews are organised at six weeks, four months and at one year after surgery. Physiotherapy would be beneficial for the first two months.

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