Revision Total Knee Replacement

Revision Knee Replacement: A future epidemic for which we already have solutions

Primary total knee replacement in many studies offers greater than 90% survival of the implants at 15 years. Knee replacement is a highly successful operation with over 55,000 operations performed in the UK last year (National Joint Registry). In the same year over 3,000 knee replacements needed revision. This amounts to just over 5% or 1-in-20 knee replacements that have failed and need to be revised. As the number of knee replacements increases, inevitably the number of revision operations will also increase.

Revision knee replacement involves opening the joint, removing all the components, cleaning out any plastic or metal debris and rebuilding the joint using metal stems and augments to support the new knee replacement. Revision knee replacement utilises significantly greater hospital resources than primary replacement (Bozic et al). Longer operative time, longer length of hospital stay, greater blood loss and diminished function have all been reported with revision compared with primary joint replacement.

The number of revision knee replacements has increased dramatically since 1990 (Kurtz, Mowat et al). Furthermore it is anticipated that there will be a massive expected demand for revision knee surgery in the next two decades. Knee revisions are projected to grow by 601% between 2005 and 2030 ( Kurtz, Lau et al.).

The survival rate following revision total knee arthroplasties is 95% at two years, 89% at five years and 79% at ten years. (Pu-Yi Sheng et al). The most significant predictors of prosthetic survival was age of the patient (greater than 70 years) and the life of service of the primary total knee replacement (greater than five years or more between primary surgery and revision). The average age at revision is 70 with no difference between men and women

CAUSES OF FAILURE

INFECTION

Infection in a prosthetic joint is a major cause of early failure and significant suffering for patients. Infection can be broadly divided into two categories. Firstly, and counting for the vast majority, is infection at the time of surgery. Secondly and much less common is late infection caused by organisms in the blood stream (bacteraemia) settling on a joint replacement.

Introduction of organisms at the time of surgery can never be totally excluded. There are, however, many precautions which can lower the risk significantly. These include an experienced specialist surgeon, operations performed within a ‘clean air enclosure’, dedicated theatre and ward staff, surgical time less than one hour, minimal disturbance of the post-operative dressings and lastly (and definitely least) antibiotic cover (prophylaxis).

Late infection resulting from blood borne infection, again, can never be totally excluded. However the risk is minimised by antibiotic cover at the time of other surgical interventions e.g. dental root canal work, abdominal or bladder surgery. Antibiotics are also indicated if there is a proven infection either in the same limb as the knee replacement or elsewhere.

Infected knee replacements present with pain, swelling, loss of movement, localised redness and warmth and occasionally a discharging sinus (a link between the joint and the skin that drains pus). Infection should always be excluded as a cause of failed joint replacement.

STIFFNESS

Stiffness results from two causes. Firstly, arthrofibrosis (excessive scar formation within the knee joint). This can be a natural phenomenon but is exacerbated by poor patient compliance with post-operative physiotherapy. The second cause of joint stiffness is a poorly balanced replacement i.e. the implants are poorly sized and positioned and result in inappropriate tension of the knee ligaments and capsule. Stiffness is often, but not always, accompanied by pain and significant loss of function.

LOOSENING

With time all implants will loosen i.e. break the bond between the cement or implant and bone. This can occur late (10 to 15 years) merely as the result of time and activity. Unfortunately some joints loosen early (2 to 5 years) as a result of poorly positioned or poorly balanced implants at the time of surgery. Poorly positioned or balanced implants will result in excessive wear of the polyethylene liner and abnormal loading of the fixation to bone. The result will be loosening of the implant which may present with a variety of symptoms. These include: Pain from the loss of fixation to bone; Instability due to loss of polyethylene thickness and/or subsidence of the implants; Swelling caused by polyethylene and/or metal debris within the joint.

RESOLVING THE CAUSES OF FAILURE

INFECTION

An infected total knee replacement cannot be resolved by antibiotics alone. Rarely in an acute early infection the joint can be salvaged by surgical debridement, lavage and exchange of the polyethylene liner.

More commonly an infected knee replacement will require two operations to eradicate the infection. In the first operation the knee replacement and all infected tissue are removed. A temporary joint replacement is constructed to allow the patient home, mobilising freely whilst the wounds and soft tissues settle. The second stage is then planned to permanently rebuild the joint. The timing of the second operation will depend on the type of temporary joint used and the confidence that the infection has been cleared. Historically infected knee replacements have been treated by inserting a spacer of acrylic cement. This meant that patients were often hospitalised and immobile for greater than 6 weeks. The timing of the second operation being determined by the incapacity of the patient, rather than certainty that the infection has cleared. Surgery performed at or around 6 to 8 weeks being performed before the soft tissues have recovered from the first operation, thus increasing the risk of recurrent infection.

At Cardiff Knee Clinic a technique has been developed for reconstructing a temporary interval replacement at the first operation. This allows the patient to be discharged within 5 to 7 days of surgery to complete an antibiotic course at home. The temporary joint allows full immediate weight bearing and movement. The second operation can then be timed to maximise the clearance of infection, often 6 to 12 months after the first. In a growing number of cases the ‘temporary’ joint is such an improvement over the infected replacement that no further surgery is required.

STIFFNESS

Stiffness of a knee resulting from arthrofibrosis may respond to physiotherapy, hard work and time. Failure to improve over 6 to 12 months should be considered for surgical excision of scar tissue with significant improvement expected.

Stiffness resulting form malpositioning of the knee replacement will not improve with physiotherapy over any length of time. Malpositioning can only be improved by removing the replacement and revising the knee to establish soft tissue balance thus allowing the knee to move.

LOOSENING

A loose knee replacement can only be resolved by removal of the implants and revising the knee. Usually the revision will need stems to increase the surface area over which fixation to bone can be achieved. Augments will be required to restore the joint line and stabilise the soft tissues and ligaments. The cause of joint loosening should be established before surgery. Infection in particular should be excluded.

EXAMPLE

Revision Total Knee Replacement Revision Total Knee Replacement

An 81 year old man presented five years after breaking his leg beneath a total knee replacement. The broken leg resulted from loosening of the knee replacement produced by polyethylene and metal debris from the failing joint. The surgeons treating the initial break were unable to offer a revision operation and advised a brace and crutches. The X-rays below show the loose knee replacement, bone cyst beneath the joint and the unhealed break.

After five years on crutches the patient was referred by his General Practitioner to the specialist knee replacement clinic in Cardiff. The knee was successfully revised using a hinged joint with long uncemented stems to bypass the bone defect and the unhealed fracture. The patient walked out of hospital five days after the operation and was off crutches by six weeks.

Revision Total Knee Replacement

CONCLUSION

Total knee replacement is an excellent operation for pain relief and return of function. However, as increasing numbers of knee replacements are performed each year the number of failing joint replacements will also increase. Revision knee replacement is a specialised operation with good long term results when performed by experienced knee surgeons in dedicated units.

Mr Rhidian Morgan-Jones FRCS (Trauma & Orthopaedics)
Revision Knee Replacement Surgeon
BUPA Hospital Cardiff & University Hospital of Wales, Cardiff
Founder of Cardiff Knee Clinic (www.cardiffkneeclinic.com)

REFERENCES

National Joint Registry Clinical Summary 2006

Bozic et al. differences in patient and procedure characteristics and hospital resource use in primary and revision total joint Arthroplasty: a Multicenter study. J. Arthroplasty. 2005; 20: 17-25

Kurtz et al. prevalence of primary and revision total hip and Arthroplasty in the United States from 1990 through 2002. J Bone Joint Surg Am. 2005; 87: 1487-97

Kurtz, S et al.

The future burden of hip and knee revisions: US projections from 2005 to 2030. In 73rd Annual Meeting of the American Academy of Orthopaedic Surgeons. Edited, Chicago, IL, 2006.

Pu-Yi Sheng et al. Revision Total Knee Arthroplasty: 1990 through 2002. A review of the Finnish Arthroplasty registry. J Bone and Joint Surgery. Volume 88-A. Number 7, July 2006: 1425-1430.