The National Institute for Clinical Excellence is examining mini-incision surgery for total knee replacement and will publish guidance on its safety and efficacy to the NHS in England, Wales and Scotland. The Institute’s Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisors, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about mini-incision surgery for total knee replacement. This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

• comments on the preliminary recommendation
• the identification of factual inaccuracies
• additional relevant evidence.

Note that this document is not the Institute’s formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows:

• The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
• The Advisory Committee will then prepare draft guidance which will be the basis for the Institute’s guidance on the use of the procedure in the NHS in England, Wales and Scotland.

For further details, see the Interim Guide to the Interventional Procedures Programme, which is available from the Institute’s website (www.nice.org.uk/ip).

Closing date for comments: 26 October 2004

Target date for publication of guidance: January 2005

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

Mini-incision surgery for total knee replacement aims to reduce trauma and hasten recovery. However, evidence on the procedure’s safety and efficacy is currently inadequate for it to be undertaken without special arrangements for consent and for audit or research.

Clinicians wishing to undertake mini-incision surgery for total knee replacement should take the following actions.

• Inform the clinical governance leads in their Trusts.
• Ensure that patients understand the uncertainty about the procedure’s safety and efficacy and provide them with clear written information. Use of the Institute’s Information for the Public is recommended.
• Audit and review clinical outcomes of all patients having mini-incision surgery for total knee replacement. Clincians are encouraged to submit data to the National Joint Registry (www.njrcentre.org.uk) for all patients having this procedure.

Training is particularly important and the British Orthopaedic Association has been asked to produce standards for training.

Further research will be useful in reducing the current uncertainty. Clinicians are encouraged to enter patients in well-defined randomised controlled trials and to collect longer-term follow-up data. The Institute may review the procedure upon publication of further evidence.

The most common indication for a total knee replacement is degenerative arthritis (osteoarthritis) of the knee joint.

Conservative treatments for arthritis symptoms include oral or topical medications for pain and inflammation, and physiotherapy. In addition, corticosteroids may be injected into the knee joint to relieve inflammation. If these therapies do not work, a partial or total knee replacement may be necessary.

Mini-incision total knee replacement involves an incision 10–12 cm long over the knee. A padded bolster is used to flex the hip, or a knee holder is used to support the leg, allowing the weight of the leg to open the joint space and push the tissue away. The surgeon can extend or flex the joint, to expose different parts of the knee. The surfaces of the tibia and femur are removed using specially designed instruments.

This technique is distinct from a standard knee replacement because the incision is much smaller (about 10–12 cm rather than 20–30 cm). The same prostheses are inserted, but in this procedure specialised instruments are used to manoeuvre around the soft tissue rather than cut through it. In addition, the kneecap can be moved to one side rather than inverted. This type of exposure reduces the need to cut muscle.

Some surgeons combine mini-incision total knee replacement surgery with computer-guided navigation to assist in the accurate placement of the prosthesis.

Two non-randomised controlled trials and three case series were identified. Two studies were reported from the same centre, but the extent of the overlap in the patient groups is unclear. In one study, 50 patients with a mini-incision total knee replacement were compared with 20 patients who had a standard total knee replacement. At 6 weeks, patients with the mini-incision procedure had a greater range of movement than patients with standard surgery, but the difference was not statistically significant. One case series of 166 patients (216 knees) with a minimum 2-year follow up reported that 98% (195/216) of knees had ‘good’ or ‘excellent’ objective patient satisfaction indices. For more details, refer to the Overview (see Appendix).

The Specialist Advisors stated that there was some uncertainty regarding the long-term functional outcome of this procedure compared with a standard total knee replacement.

There was limited information on safety outcomes for most of the studies. In a case series of 66 patients, 4.5% (3/66) patients had a complication arising from the procedure. These complications were pulmonary embolism (1 patient), transient peroneal nerve palsy (1 patient) and intraoperative myocardial infarction (1 patient). In a case series of 20 patients, 10% (2/20) of patients had painful crepitus and 5% (1/20) had haemarthrosis. In a case series of 166 patients, 2.3% (5/216) knees required re-operation. For more details, refer to the Overview (see Appendix).

The Specialist Advisors stated that poor positioning of the components was the main safety concern.

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

• Interventional procedure overviews of mini-incision surgery for total knee replacement, April 2004

Available from: www.nice.org.uk/ip247overview