REVISION WITHIN THE FIRST 5 YEARS AFTER PRIMARY TOTAL KNEE ARTHROPLASTY

Abstract

This study was conducted to investigate the cases which were obliged to receive revision surgery within the first 5 years after primary Total Knee Arthroplasty (TKA).

The subjects of this study were 15 patients (5 males & 10 females, mean age at revision 72 years) who had undertaken revision surgery within 5 years since 1996. Intervals between primary and revision TKA averaged 29.8 months. Prosthesis used for primary TKA was as follows; 11 Zimmer NexGen LPS-flex fixed bearing, 2 mobile bearing, 2 CR type.

Revised components, cause of revision, JOA score as clinical results and FTA as radiographic evaluation were examined.

Revised parts were as follows;

1. All components: 2,

2. Both Femoral and Tibial components: 4,

3. only Femoral component: 2,

4. only Tibial component: 5,

5. only patella component: 1,

6. only articular surface: 1.

Stemmed Femoral components were used in 6 out of 8 knees, stemmed Tibial components in 9 out of 11 knees.

The causes of revision were as follows;

1. infection: 1,

2. loosening: 7,

3. inadequate component position: 4,

4. instability: 2,

5. pain: 1.

JOA scores improved from 45 points to 78 points, and FTA proved to be 176 deg., postoperatively.

Primary TKA remains one of the most successful orthopedic procedures. Survivorship was generally reported over 15 years in the previous article. However, there are some cases in which revision TKA is necessary by some causes. There seems to be various types of causes for revisions, such as loosening, inadequate position, abrasion of components and others. Though loosening of components due to traumatic cause was inevitable, other causes, such as inadequate position of component, imbalanced soft tissues and infection, which depend on our technique, should be cared during and after surgery. From our study, except for 7 (2 trauma, 5 unknown) out of 15 knees, almost half of revision TKA (8 knees) might be due to technical demand. As for surgical techniques, in the case of poor bony quality, we routinely use stemmed components and should try not to impact strongly on setting component to prevent from sinking. In the case of non-traumatic cause, 3 out of 12, though the position of tibial component was acceptable, tibial component sunk because of bony weakness and/or imbalanced soft tissues resulting pain.

Adequate position and balance of components should be achieved during primary TKA. In our department, we are trying to revise and routinely use stemmed components as soon as possible, when loosening of component is confirmed. Metal augmentation, if necessary, is mainly used for bone defect to do early rehabilitation.

We concluded that adequate position of components and soft tissue balance was very important at the time of primary TKA. Clinical results of revision TKA were almost equal to those of primary TKA, however, long term follow-up will be needed.