The pre-operative level of haemoglobin is the strongest predictor
of the peri-operative requirement for blood transfusion after total
knee arthroplasty (TKA). There are, however, no studies reporting
a value that could be considered to be appropriate pre-operatively. This study aimed to identify threshold pre-operative levels of
haemoglobin that would predict the requirement for blood transfusion
in patients who undergo TKA. Analysis of receiver operator characteristic (ROC) curves of
2284 consecutive patients undergoing unilateral TKA was used to
determine gender specific thresholds predicting peri-operative transfusion
with the highest combined sensitivity and specificity (area under
ROC curve 0.79 for males; 0.78 for females).Aims
Patients and Methods
This study demonstrates a significant correlation
between the American Knee Society (AKS) Clinical Rating System and
the Oxford Knee Score (OKS) and provides a validated prediction
tool to estimate score conversion. A total of 1022 patients were prospectively clinically assessed
five years after TKR and completed AKS assessments and an OKS questionnaire.
Multivariate regression analysis demonstrated significant correlations between
OKS and the AKS knee and function scores but a stronger correlation
(r = 0.68, p <
0.001) when using the sum of the AKS knee and
function scores. Addition of body mass index and age (other statistically
significant predictors of OKS) to the algorithm did not significantly
increase the predictive value. The simple regression model was used to predict the OKS in a
group of 236 patients who were clinically assessed nine to ten years
after TKR using the AKS system. The predicted OKS was compared with
actual OKS in the second group. Intra-class correlation demonstrated
excellent reliability (r = 0.81, 95% confidence intervals 0.75 to
0.85) for the combined knee and function score when used to predict
OKS. Our findings will facilitate comparison of outcome data from
studies and registries using either the OKS or the AKS scores and
may also be of value for those undertaking meta-analyses and systematic
reviews. Cite this article:
A total of 445 consecutive primary total knee
replacements (TKRs) were followed up prospectively at six and 18 months
and three, six and nine years. Patients were divided into two groups:
non-obese (body mass index (BMI) <
30 kg/m2) and obese
(BMI ≥ 30 kg/m2). The obese group was subdivided into
mildly obese (BMI 30 to 35 kg/m2) and highly obese (BMI ≥ 35
kg/m2) in order to determine the effects of increasing
obesity on outcome. The clinical data analysed included the Knee
Society score, peri-operative complications and implant survival.
There was no difference in the overall complication rates or implant
survival between the two groups. Obesity appears to have a small but significant adverse effect
on clinical outcome, with highly obese patients showing lower function
scores than non-obese patients. However, significant improvements
in outcome are sustained in all groups nine years after TKR. Given
the substantial, sustainable relief of symptoms after TKR and the low
peri-operative complication and revision rates in these two groups,
we have found no reason to limit access to TKR in obese patients.
We report the ten-year survival of a cemented
total knee replacement (TKR) in patients aged <
55 years at the
time of surgery, and compare the functional outcome with that of
patients aged >
55 years. The data were collected prospectively
and analysed using Kaplan-Meier survival statistics, with revision
for any reason, or death, as the endpoint. A total of 203 patients
aged <
55 years were identified. Four had moved out of the area
and were excluded, leaving a total of 221 TKRs in 199 patients for
analysis (101 men and 98 women, mean age 50.6 years (28 to 55));
171 patients had osteoarthritis and 28 had inflammatory arthritis.
Four patients required revision and four died. The ten-year survival
using revision as the endpoint was 98.2% (95% confidence interval
94.6 to 99.4). Based on the Oxford knee scores at five and ten years,
the rate of dissatisfaction was 18% and 21%, respectively. This
was no worse in the patients aged <
55 years than in patients
aged >
55 years. These results demonstrate that the cemented PFC Sigma knee has
an excellent survival rate in patients aged <
55 ten years post-operatively,
with clinical outcomes similar to those of an older group. We conclude
that TKR should not be withheld from patients on the basis of age.
We report the general mortality rate after total
knee replacement and identify independent predictors of survival. We
studied 2428 patients: there were 1127 men (46%) and 1301 (54%)
women with a mean age of 69.3 years (28 to 94). Patients were allocated
a predicted life expectancy based on their age and gender. There were 223 deaths during the study period. This represented
an overall survivorship of 99% (95% confidence interval (CI) 98
to 99) at one year, 90% (95% CI 89 to 92) at five years, and 84%
(95% CI 82 to 86) at ten years. There was no difference in survival
by gender. A greater mortality rate was associated with increasing
age (p <
0.001), American Society of Anesthesiologists (ASA)
grade (p <
0.001), smoking (p <
0.001), body mass index (BMI)
<
20 kg/m2 (p <
0.001) and rheumatoid arthritis
(p <
0.001). Multivariate modelling confirmed the independent
effect of age, ASA grade, BMI, and rheumatoid disease on mortality.
Based on the predicted average mortality, 114 patients were predicted
to have died, whereas 217 actually died. This resulted in an overall
excess standardised mortality ratio of 1.90. Patient mortality after
TKR is predicted by their demographics: these could be used to assign
an individual mortality risk after surgery.
In Scotland, the number of primary total knee replacements performed annually has been increasing steadily. The price of the implant is fixed but the length of hospital stay is variable. We prospectively investigated all patients who underwent primary unilateral total knee replacement in the Scottish region of Fife, between December 1994 and February 2007 and assessed their recorded pre-operative details. The data were analysed using univariate and multiple linear regression statistical analysis. Data on the length of stay were available from a total of 2106 unilateral total knee replacements. The median length of hospital stay was eight days. The significant pre-operative risk factors for an increased length of stay were the year of admission, details of the consultant looking after the patient, the stair score, the walking-aid score and age. Awareness of the pre-operative factors which increase the length of hospital stay may provide the opportunity to influence them favourably and to reduce the time in hospital and the associated costs of unilateral total knee replacement.
Pain is the main indication for performing total knee replacement (TKR). In most patients after TKR there is an improvement, but a few continue to have pain. Generally, the cause of the pain can be addressed when it is identified. However, unexplained pain can be more difficult to manage because revision surgery is likely to be unrewarding in this group. In our study of 622 cemented TKRs in 512 patients with a mean age of 69 years (23 to 90) treated between January 1995 and August 1998, we identified 24 patients (knees) with unexplained pain at six months. This group was followed for five years (data was unavailable for 18 knees) and ten patients (55.5%) went on to show an improvement without intervention. In the case of unexplained pain, management decisions must be carefully considered, but reassurance can be offered to patients that the pain will improve in more than half with time.
The results of 41 consecutive total knee replacements performed on morbidly obese patients with a body mass index >
40 kg/m2, were compared with a matched group of 41 similar procedures carried out in non-obese patients (body mass index <
30 kg/m2). The groups were matched for age, gender, diagnosis, type of prosthesis, laterality and pre-operative Knee Society Score. We prospectively followed up the patients for a mean of 38.5 months (6 to 66). No patients were lost to follow-up. At less than four years after operation, the results were worse in the morbidly obese group compared with the non-obese, as demonstrated by inferior Knee Society Scores (mean knee score 85.7 and 90.5 respectively, p = 0.08; mean function score 75.6 and 83.4, p = 0.01), a higher incidence of radiolucent lines on post-operative radiographs (29% and 7%, respectively, p = 0.02), a higher rate of complications (32% and 0%, respectively, p = 0.001) and inferior survivorship using revision and pain as end-points (72.3% and 97.6%, respectively, p = 0.02). Patients with a body mass index >
40 kg/m2 should be advised to lose weight prior to total knee replacement and to maintain weight reduction. They should also be counselled regarding the inferior results which may occur if they do not lose weight before surgery.
A total of 370 consecutive primary total knee replacements performed for osteoarthritis were followed up prospectively at 6, 18, 36 and 60 months. The Knee Society score and complications (perioperative mortality, superficial and deep wound infection, deep-vein thrombosis and revision rate) were recorded. By dividing the study sample into subgroups based on the body mass index overall, the body mass index in female patients and the absolute body-weight. The outcome in obese and non-obese patients was compared. A repeated measures analysis of variance showed no difference in the Knee Society score between the subgroups. There was no statistically-significant difference in the complication rates for the subgroups studied. Obesity did not influence the clinical outcome five years after total knee replacement.
We investigated fixed flexion deformity (FFD) after total knee replacement (TKR). Data relating to 369 cruciate-retaining unilateral TKRs performed at a single institution were collected prospectively. Fixed flexion was measured pre-operatively and at one week, six months, 18 months, three years and five years after surgery. Using binary logistic regression, pre-operative FFD was a predictor of post-operative FFD >
10° at one week (p = 0.006) and six months (p = 0.003) following surgery. Gender was a predictor at one week (p = 0.0073) with 24% of women showing a FFD >
10° compared with 37% of men. We have shown that a gradual improvement in knee extension can be expected up to three years after surgery in knees with FFD. By this time residual FFD is mild or absent in the majority of patients, including those who had a severe pre-operative FFD.