Purpose of study: The purpose of the study was to determine the influence of patient’s pre-operative mental state on post-operative physical outcomes in primary and revision total knee arthroplasty (TKA).

Methods: 100 Primary and 60 Revision TKA patients were prospectively assessed using SF-12 and WOMAC outcome measures. They were assessed pre-operatively and at six and twelve months post-operatively.

All surgery was performed by a single surgeon, using one prosthesis design in each group.

The data were assessed for any correlation between the pre-operative MCS and post-operative PCS, Pain, Stiffness and Function scores using Spearman’s Rank Correlation.

Results: There was a significant positive correlation between pre-operative MCS and post-operative PCS scores at six and twelve months (P=0.01 and P=0.031 respectively) in the primary TKA patients. There was no correlation in the revision patients.

There was a statistically significant negative correlation between pre-operative MCS and six month WOMAC Pain, Stiffness and Function scores (P=0.025, P=0.019 and P=0.011 respectively) in the primary patients. There was no significant correlation with twelve months WOMAC scores.

There was no significant correlation in terms of pre-operative MCS and six months WOMAC scores in the revision patients, but there was a statistically significant negative correlation between pre-operative MCS and the twelve months pain score (P=0.039).

Conclusion: The results support the concept that high generic mental health scores in patients prior to primary TKA are associated with good physical outcomes in terms of both generic health outcome measures and disease-specific outcome measures.

There has been speculation as to whether the outcome of revision total knee arthroplasty (TKA) is as successful as primary TKA, this study was designed to compare the outcomes of primary and revision TKA in order to address this question.

The study collected data prospectively from patients operated upon by one surgeon using one prosthesis design in each group. All patients undergoing revision TKA between 1997 and 2000 were included in the study. 100 consecutive patients undergoing primary TKA between 1997 and 1999 were included in the study. All surgery was performed by the senior author.

Patients completed SF-12 and WOMAC questionnaires pre-operatively and at six and twelve months post-operatively. Mean scores were calculated for the different areas within both outcome measures (WOMAC pain, stiffness and function; SF-12 – physical constant score [PCS] and mental constant score [MCS])

The results were entered into a database and analysed using a combination of two way and simple repeated measures analysis of variance (ANOVA) and t-tests. Only if the result of the ANOVA was significant were post-hoc adjusted t-tests performed on the data values.

WOMAC scores did not differ between the two groups pre-operatively. Both patient groups showed a significant improvement in WOMAC scores at six months (P< 0.0005). In the primary group the pain and function scores improved significantly between six and twelve months (P=0.0258 and P=0.0019 respectively). This was not the case in revision patients.

SF-12 PCS scores were significantly better in the primary patients pre-operatively (P< 0.0005). Both groups showed a significant improvement at six months assessment (P< 0.0005). Neither group demonstrated an improvement between six and twelve months. SF-12 MCS scores did not show any difference between the two groups pre-operatively. No significant change in MCS score occurred during the study in either the primary or revision patients.

The SF-12 and WOMAC health questionnaires are valid, reliable and responsive outcome measures. The study has collected data prospectively from patients operated upon by one surgeon using one prosthesis design in each group. These findings support the concept that revision TKA leads to a comparable improvement in patient perceived outcomes of physical parameters as does primary TKA in both generic health outcome measures and disease specific outcome measures.