Surgical options for knee arthritis

Unicompartmental Knee Replacement

This type of knee replacement only replaces the area of the knee where the osteoarthritis has worn away the cartilage, typically the inside of the knee. It has the advantage of preserving the remaining normal part of the knee as well as the ligaments in the middle of the knee joint. 

The advantages of the uni knee replacement in comparison to a total knee replacement are that the recovery is slightly faster and some of the risks of the operation are slightly lower. I would encourage you to read the following research paper related to unicompartmental knee replacements in comparison to total knee replacements https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)31281-4/fulltext.

The procedure takes about 1.5 hours:

• I make a cut down the front of your knee to expose your kneecap. This is then moved to the side so I can access the knee joint behind it.

• The worn areas of bone and cartilage are then removed and the bone is cut so that a metal replacement can be fitted onto the worn compartment. The cruciate ligaments are preserved.

• This metal resurfacing is then fixed using special bone 'cement'. A high density plastic spacer is placed between the pieces of metal, which acts as the articulation of the joint. 

The wound is closed with either stitches or clips and a dressing is applied to the wound. You will be encouraged to mobilise either on the day of your surgery or the following morning, to get the knee moving as soon as possible. 

Total Knee Replacement

This type of knee replacement is used when there is evidence of osteoarthritis affecting large areas of the knee joint. It is indicated when the knee remains very painful despite non-operative measures. In a total knee replacement, both sides of your knee joint are replaced.

The procedure takes 1.5 hours:

• I make a cut down the front of your knee to expose your kneecap. This is then moved to the side so I can access the knee joint behind it.

• The worn areas of bone and cartilage are then removed and the bone is cut so that a metal replacement can be fitted onto both the bottom and top of the knee.

• This metal resurfacing is then fixed using special bone 'cement'. A high density plastic spacer is placed between the pieces of metal, which acts as the articulation of the joint. 

• The back of the knee cap is usually also replaced, depending on the reasons for replacement.

• The wound is closed with either stitches or clips and a dressing is applied to the wound. You will be encouraged to mobilise either on the day of your surgery or the following morning, to get the knee moving as soon as possible. 

Robotic Surgery

Traditionally total knee replacements are performed ‘manually’, i.e. by a surgeon with conventional instruments to help make accurate bone cuts based on pre-operative x-rays, and this remains the most common technique in routine use worldwide. However, as technology has advanced, computer-assisted surgery (CAS) has been increasingly used to assist surgeons to perform hip and knee arthroplasty more accurately.

The Mako robotic-arm system is an example of a haptic robotic system, whereby active participation of the surgeon is required to manipulate the cutting instrument according to an operative plan, within a pre-defined “cutting zone”. The instrument is attached to a robotic arm which provides haptic feedback to the surgeon, limiting the bony resection to the defined limits, and automatically stopping if the surgeon strays outside these. 

The Mako system uses a pre-operative CT scan to create a 3D model of the patient’s anatomy, which is then ‘merged’ with the patient’s actual anatomy during intra-operative registration. The surgeon may then record the range of movement and soft tissue envelope and then fine tune the final planned implant positions to best match the patient’s bony and soft tissue anatomy in order to restore optimum function and maximise bone preservation.

The use of the MAKO robot is an option that is available at the Nuffield for both uni and total knee replacement surgery and I would be happy to discuss its uses further with you.