Determining the effect of deprivation on quality of life after total and unicompartmental knee arthroplasty Quality of life (QoL) following joint replacement is now a national priority, with every patient being assessed using the Oxford Knee Score. The current literature is conflicted as to whether deprivation has any effect on outcome after knee surgery. The type of surgery is another variable that may determine outcome. We set out to investigate which of these factors was a more powerful predictor of outcome. A prospective trial began where, 68 patients were telephoned, (30 TKA’s and 38 UKA’s). Each were asked a series of questions comprising the Oxford Knee Score (post operation), Imperial Knee Score (post operation), EuroQol-5D (pre and post operation) and individual deprivation questions. This was compared with the deprivation status using Townsend scores. A comparison of total and unicompartmental outcomes were also analysed including cost-effectiveness. No correlation was found between outcome and Townsend scores (p < 0.05). Age was seen to be a significant indicator of pre surgical QoL. However, a large and significant difference was found between UKA and TKA when using the EQ-5D (p < 0.05) and the Imperial Knee Score (p < 0.09). This was not reflected in the Oxford Knee Score. UKA’s were also found to be more cost-effective than TKA’s. Deprivation has no major effect on the outcome of knee surgery in London. A clear difference in efficacy exists between TKA’s and UKA’s. Sensitivity of scores needs to be addressed.
Access to health care is a fundamental right and one measure of a functioning and developed society. Inequities in access exist on both a global and a national level. Deprivation in terms of social and economic factors has been shown to reduce access to health care and quality of life after surgery [
There has been a recent interest in the disparity between expectation, outcome and social deprivation after surgery. However, there is only one research paper that specifically compares knee replacement and social deprivation [
Unicompartmental knee replacements have been shown by some to have superior outcomes in comparison to total knee replacements in selected patients, in both function and cost, yet they still only account for 7% of the knee arthroplasty figures nationally [
Age and gender have not been established as major prognostic indicators or limiting factors in knee replacement surgery, however age is known to be associated with lower access to health care [
Quality of life (QoL) can be described as “goodness of life” with “health related quality of life” being one aspect of this wider term. These measures are gaining popularity due to their use as end points in the evaluation of interventional outcomes. Current definitions vary amongst the health care community and the taxonomy has been well described [
To fully evaluate each variable of QoL is a complex task and the measure of quality of life used must be heavily evaluated to justify its use and must fulfil the criterion of sensitivity, reliability responsiveness and validity.
Health related quality of life is notoriously difficult to measure [
It is for these reasons that the EuroQol (EQ-5D) [
Studies looking at the correlation between EQ-5D and SF-36 found a higher dependency in EQ-5D with regards to activities of daily living and have shown similar response rates [
Knee function was assessed via the Oxford Knee Score [
The patient’s outcome was also assessed using a system developed by Weiss et al. (2002) [
The Total Knee Score is multiplied by the UCLA activity scale. This rates the amount of activity possible by the individual on a scale of 1 - 10 with 10 being the most active and able to participate in frequent, impact sports. This novel formula, weights the Total Knee Score, giving a unique measure of quality of life, which we have termed the Imperial Knee Score. This may give a more accurate picture of the patient’s individual ability in the areas that are most important to them.
Currently, a number of methods for assessing deprivation exist. The majority assess “material deprivation” such as the Townsend Score [
Other scores such as the Jarman Index [
It is the purpose of this study to explore whether social deprivation affects health related quality of life (QoL) and knee function after knee replacement. In the current climate, the social divide is attracting media and political attention. The effect of this on orthopaedic outcomes is therefore particularly relevant.
Our primary hypothesis is thus that more deprived patients fare worse following knee arthroplasty.
Our secondary hypotheses are these:
1) That older patients have poorer access to health care, and fare worse after knee arthroplasty;
2) That unicompartmental knee arthroplasty is more effective and more cost effective than total knee arthroplasty;
3) That the imperial knee score is more sensitive than the oxford knee score in detecting significant differences in health related quality of life.
A retrospective, single centre trial was conducted over a period of 6 months which included 68 patients. Patients were included in the trial if they received either a TKA or UKA in the last 12 months. Patient characteristics are given in
Patients were contacted by telephone and the following was assessed:
Outcomes | |||
---|---|---|---|
Total | Uni | Mean | |
N | 30 | 38 | 68 |
Mean Age | 72.4 | 69.4 | 70.9 |
Gender | |||
Male Female | 12 18 | 19 21 | 15.5 19.5 |
Outcome measure | |||
Mean Oxford Knee Score Mean Imperial Knee Score Mean EQ-5D (pre op) Mean EQ-5D (post op) Mean EQ-5D (change) Mean Total Knee Score | 22.3 32.4 0.22 0.59 0.37 6.03 | 20.13 40.87 0.21 0.77 0.53 6.357 | 21.22 73.27 0.215 0.68 0.45 6.19 |
・ Individual factors-age, gender and type of operation.
・ The Oxford knee questionnaire (post operation).
・ The Total Knee Questionnaire (post operation).
・ EuroQoL-5D (pre and post operation).
・ Individual deprivation questions.
Townsend scores were calculated based on the Census data for each postcode.
This essentially consists of two sections-the descriptive system and the EQ-visual analogue scale (EQ-VAS). The descriptive system assesses five dimensions of health: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each dimension having three levels. The EQ-VAS records self-rated health on a vertical visual analogue scale (0 - 100). This is combined into a single summary index by applying a formula that attaches a weight to each of the health states [
Townsend Scores range from −3.17 to 13.27 with 13.27 being the most deprived area. Measures of material deprivation are aggregated including unemployment, housing, over-crowding and car ownership. Each variable is attached the same weight. These are standardised and combined to produce a single index of deprivation based on each electoral ward. The overall score for Hammersmith is +1.8 indicating an area that is above the national average of deprivation.
Each individual was asked: Employment/previous employment, house ownership, number of rooms/people in each house and car ownership. This gave additional information on deprivation status. An additional question of time taken to receive the operation and reasons for delays was also asked to see if a disparity in waiting times existed and whether this has any correlation with outcomes. However, the data proved to be inconsistent and therefore was not included in the correlation analysis. However, all the available data was studied on an individual basis to see if this subjectively correlated with Townsend Scores.
The Oxford Knee Score is a twelve question, quantitative measure of knee function [
This is a combination of the Total Knee Score [
A detailed analysis of the cost effectiveness of each procedure was undertaken. This involved calculating the expected life years remaining for each individual using a life table, provided by the Office of National Statistics (2005) [
A cost effectiveness ratio was calculated by dividing the expected cost for each procedure (data gathered from Charing Cross Hospital) by the average QALY gained.
A power calculation was performed using “DSS research” software. An analysis of 102 knees comparing TKA and UKA conducted by Newman et al. (1998) [
Descriptive statistics were conducted using SPSS. Histograms and box plots were produced allowing for visual analysis of quality of life and knee function scores. These were further analysed using Pearson’s correlation coefficient. This tests for linear correlation which is shown to be valid in this situation. Uni-variate analysis was conducted using a non-paired student t-test after normality was shown using a Kolmogorov-Smirnov test. Multiple linear regression analysis was also conducted on the independent variables as age, gender, type of operation and Townsend Score compared with each outcome measure (dependant variable). This finds whether a linear relationship exists between the response variable and several predictor variables. Multiple Regression correlation coefficients were also produced to assess the proportion of variability explained by the regression in the sample (R2).
Score | Grading |
---|---|
Score 12 to 20 | May indicate satisfactory joint function. May not require any formal treatment. |
Score 21 to 30 | May indicate mild to moderate knee arthritis. Consider seeing your family physician for an assessment and possible x-ray. You may benefit from non-surgical treatment, such as exercise, weight loss, and /or anti-inflammatory medication |
Score 31 to 40 | May indicate moderate to severe knee arthritis. See your family physician for an assessment and X-ray. Consider a consult with an Orthopaedic Surgeon. |
Score 41 to 60 | May indicate severe knee arthritis. It is highly likely that you may well require some form of surgical intervention, contact your family physician for a consult with an Orthopaedic Surgeon. |
Initial analysis of the data using a Kolmogorov-Smirnov test found a normal distribution attributable to the Townsend score (sig. 0.001), age (sig. 0.04), pre-operation EQ-5D (sig. 0.0001) and an equally represented gender distribution. We therefore showed a good spread of deprivation, age and quality of life before surgery within the sample population. This data is reflected in histogram of Townsend Scores provided (
We could not demonstrate either a positive nor negative relationship in any outcome measure compared to Townsend Scores (
Our study demonstrated a significant difference between pre and post op EQ-5D (sig. 0.0001) regardless of type of surgery. We have found a large and significant difference in EQ-5D post surgery between UKA and TKA. UKA showing a higher quality of life after surgery. Our study shows the pre-operation EQ-5D is not significantly different between UKA and TKA’s, neither is age, gender or change in EQ-5D following surgery. This shows equal level of morbidity, gender and age distribution between the TKA and UKA groups before surgery. The difference is not reflected in the Oxford Knee Score or the Total Knee Score but is reflected in both the EQ-5D (sig. 0.05) and the Imperial Knee Score (sig. 0.09) (
The final analysis is the cost effectiveness of each procedure. We find a cost per QALY of £1160.93 for a TKA compared with £711.97 for a UKA.
This demonstrates a £448.96 saving per quality of life year gained with a UKA compared with a TKA (
Statistic | Pearson’s | p-value | Regression | p-value |
---|---|---|---|---|
Outcome vs. Townsend score | ||||
Oxford Knee Score Imperial Knee Score Total Knee Score EQ-5D (pre-op) (post-op) (Change) | +0.122 −0.036 −0.084 +0.044 −0.059 −0.080 | 0.33 0.784 0.526 0.723 0.635 0.523 | 0.953 −0.161 −0.66 0.074 −0.447 −0.41 | 0.345 0.873 0.512 0.941 0.657 0.683 |
Unicompartmental cf. Total | Pearson’s | p-value | Student t-test | p-value |
Oxford Knee Score Imperial Knee Score Total Knee Score EQ-5D pre-op post-op change | −0.111 0.21 0.069 0.02 0.274 0.193 | 0.369 0.09* 0.595 0.874 0.024** 0.115 | 0.902 −1.724 0.510 −0.163 −2.254 −1.616 | 0.370 0.09 0.595 0.874 0.024** 0.115 |
Other significant results | Regression t value | p-value | ||
Age vs. Pre op EQ-5D | - | - | 2.4 | 0.019** |
Age vs. Change EQ-5D | - | - | −2.274 | 0.026** |
Uni vs. Total post op EQ-5D | - | - | 2.13 | 0.037** |
Pre vs post op EQ-5D | −8.44 | 0.0001** |
The study is limited by the small sample population. However, this study has still shown significant results and can be seen as a preliminary study that demands further investigation in the areas identified.
Errors may also have occurred as two separate data collectors telephoned patients. Therefore, an observer bias may have arisen. However, a reliability study was conducted using 80 observations with an overall 70% similarity in outcome. EQ-5D has an overall inter-rater bias of 0.69 - 0.94, which is consistent with the reproducibility study conducted. Data entry may also be a source of error, this was verified by a random sample of 20 patients who were studied by an independent observer and a parallel of 97% was found. Limitations in terms of outcome measures are discussed in the introduction.
To address the primary objective of this study i.e. to see if deprivation has an effect on outcome after knee surgery, our study failed to demonstrate a relationship between deprivation and any outcome measure. This can be seen to compliment the research by Murray et al. (2005) [
Knee replacement regardless of type of operation can be seen to improve quality of life (p < 0.0001). However, we found a large and significant difference exists between the UKA’s and TKA’s after surgery. This can be seen as comparable to the studies by Laurencin (1996) and Newman (1998) [
Therefore, we can see that the National Health Service provider in the Hammersmith area is providing a high level of satisfaction to all clients regardless of social and economic background. Analysis at Charing Cross has revealed UKA to be indicated for the majority of patients with TKA being reserved for the minority. Expenditure in knee surgery in the UK is set at 300 million pounds with 93% being TKA (UK National Joint Registry). This study has identified a £448.96 pound saving per quality of life year gained in using a UKA in comparison to a TKA. If this data was utilised and UKA replacement was used in 50% of the cases an overall saving of £37 million pounds and a cost utility gain of £11 million is identified.
If this is compared to the cost-effectiveness of other interventions such as renal dialysis which is estimated at £30,000 per QALY gained or chemotherapeutic drugs such as anastrazole being £17,656 per QALY gained UKA can be considered to be a relatively inexpensive and highly effective intervention [
In conclusion, in this study deprivation can be seen to have no effect on either access to or outcome after knee replacement. This has been identified in all outcome measures and upholds the principles of the NHS to provide an equal service to all regardless of economic status.
A clear difference in efficacy between TKA’s and UKA’s has been found in this study. Currently, the UKA knee has fluctuated in popularity; however, with the development of minimally invasive procedures and research into its benefits over TKA, it is the recommendation of this study to promote UKA with equal reflection in the monetary policy of the NHS. This will be both beneficial for the consumer and the NHS.
Finally, the sensitivity of scores for subjective rating of health related quality of life, needs to be addressed. We have shown that the Oxford Knee Score although considered a reliable scoring system and one of the most popular tools in orthopaedics, does not adequately reflect the multidimensional nature of quality of life. This study has shown that the EQ-5D and the Imperial Knee Score are much more sensitive in discriminating post surgical outcomes. The Imperial Knee Score can be seen as a sensitive and specific tool for measuring knee function and warrants further promotion and validation.