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1.  Minimal clinically important improvement (MCII) and patient-acceptable symptom state (PASS) in total hip arthroplasty (THA) patients 1 year postoperatively 
Acta Orthopaedica  2014;85(1):39-48.
Background and purpose
The increased use of patient-reported outcomes (PROs) in orthopedics requires data on estimated minimal clinically important improvements (MCIIs) and patient-acceptable symptom states (PASSs). We wanted to find cut-points corresponding to minimal clinically important PRO change score and the acceptable postoperative PRO score, by estimating MCII and PASS 1 year after total hip arthroplasty (THA) for the Hip Dysfunction and Osteoarthritis Outcome Score (HOOS) and the EQ-5D.
Patients and methods
THA patients from 16 different departments received 2 PROs and additional questions preoperatively and 1 year postoperatively. The PROs included were the HOOS subscales pain (HOOS Pain), physical function short form (HOOS-PS), and hip-related quality of life (HOOS QoL), and the EQ-5D. MCII and PASS were estimated using multiple anchor-based approaches.
Of 1,837 patients available, 1,335 answered the preoperative PROs, and 1,288 of them answered the 1-year follow-up. The MCIIs and PASSs were estimated to be: 24 and 91 (HOOS Pain), 23 and 88 (HOOS-PS), 17 and 83 (HOOS QoL), 0.31 and 0.92 (EQ-5D Index), and 23 and 85 (EQ-VAS), respectively. MCIIs corresponded to a 38–55% improvement from mean baseline PRO score and PASSs corresponded to absolute follow-up scores of 57–91% of the maximum score in THA patients 1 year after surgery.
This study improves the interpretability of PRO scores. The different estimation approaches presented may serve as a guide for future MCII and PASS estimations in other contexts. The cutoff points may serve as reference values in registry settings.
PMCID: PMC3940990  PMID: 24286564
The Journal of rheumatology  2011;38(8):10.3899/jrheum.110402.
The Use of Item Response Theory (IRT) and, subsequently, Computerized Adaptive Testing (CAT) under the umbrella of the NIH-PROMIS (Patient-Reported Outcomes Measurement Information System) initiative brings strong new assets to the development of more sensitive, more widely applicable, and more efficiently administered Patient-Reported Outcome (PRO) instruments. We present data on current progress in three crucial areas: floor and ceiling effects, responsiveness to change, and interactive computer-based administration over the internet.
We examined nearly 1000 patients with rheumatoid arthritis and related diseases in a series of studies including a one-year longitudinal examination of detection of change. We compared responsiveness of the Legacy SF-36 and HAQ-DI instruments with IRT-based instruments. We performed a randomized head-to-head trial of four modes of item administration. We simulated the effect of lack of floor and ceiling items upon statistical power and sample sizes.
IRT-based PROMIS instruments are more sensitive to change, resulting in the potential to reduce sample sizes requirements substantially by up to a factor of four. The modes of administration tested did not differ from each other in any instance by more than one-tenth of a standard deviation. Floor and ceiling effects greatly reduce the number of available subjects, particularly at the ceiling.
Failure to adequately address floor and ceiling effects that determine the range of an instrument can result in sub-optimal assessment of many patients. Improved items, improved instruments, and computer-based administration improve PRO assessment and represent a fundamental advance in clinical outcomes research.
PMCID: PMC3827974  PMID: 21807798
Item Response Theory (IRT); Patient Reported Outcomes Measurement Information System (PROMIS); Physical Function, Disability; Computerized Adaptive Testing (CAT); Sample Sizes
3.  Translation, cross-cultural adaptation and validation of the Danish version of the Oxford hip score 
Bone & Joint Research  2012;1(9):225-233.
The Oxford hip score (OHS) is a 12-item questionnaire designed and developed to assess function and pain from the perspective of patients who are undergoing total hip replacement (THR). The OHS has been shown to be consistent, reliable, valid and sensitive to clinical change following THR. It has been translated into different languages, but no adequately translated, adapted and validated Danish language version exists.
The OHS was translated and cross-culturally adapted into Danish from the original English version, using methods based on best-practice guidelines. The translation was tested for psychometric quality in patients drawn from a cohort from the Danish Hip Arthroplasty Register (DHR).
The Danish OHS had a response rate of 87.4%, no floor effect and a 19.9% ceiling effect (as expected in post-operative patients). Only 1.2% of patients had too many items missing to calculate a sum score. Construct validity was adequate and 80% of our predefined hypotheses regarding the correlation between scores on the Danish OHS and the other questionnaires were confirmed. The intraclass correlation (ICC) of the different items ranged from 0.80 to 0.95 and the average limits of agreement (LOA) ranged from -0.05 to 0.06. The Danish OHS had a high internal consistency with a Cronbach’s alpha of 0.99 and an average inter-item correlation of 0.88.
This Danish version of the OHS is a valid and reliable patient-reported outcome measurement instrument (PROM) with similar qualities to the original English language version.
PMCID: PMC3626210  PMID: 23610695
Patient-reported outcome measurement instrument; PRO; PROMs; Oxford hip score; OHS; Validation; Total hip replacement; THR; Danish Hip Arthroplasty Registry (DHR)
4.  Validation of the Spanish version of the hip outcome score: a multicenter study 
The Hip Outcome Score (HOS) is a self-reported questionnaire evaluating the outcomes of treatment interventions for hip pathologies, divided in 19 items of activities of daily life (ADL) and 9 sports’ items. The aim of the present study is to translate and validate HOS into Spanish.
A prospective and multicenter study with 100 patients undergoing hip arthroscopy was performed between June 2012 and January 2013. Crosscultural adaptation was used to translate HOS into Spanish. Patients completed the questionnaire before and after surgery. Feasibility, reliability, internal consistency, construct validity (correlation with Western Ontario and McMaster Universities Osteoarthritis Index), ceiling and floor effects and sensitivity to change were assessed for the present study.
Mean age was 45.05 years old. 36 women and 64 men were included. Feasibility: 13% had at least one missing item within the ADL subscale and 17% within the sport subscale. Reliability: the translated version of HOS was highly reproducible with intraclass correlation coefficient of 0.95 for ADL and 0.94 for the sports subscale. Internal consistency was confirmed with Cronbach’s alpha >0.90 in both subscales. Construct validity showed statistically significant correlation with WOMAC. Ceiling effect was observed in 6% and 12% for ADL and sports subscale, respectively. Floor effect was found in 3% and 37% ADL and sports subscale, respectively. Large sensitivity to change was shown in both subscales.
The translated version of HOS into Spanish has shown to be feasible, reliable and sensible to changes for patients undergoing hip arthroscopy. This validated translation of HOS allows for comparisons between studies involving either Spanish- or English-speaking patients.
Level of evidence
Prognostic study, Level I
PMCID: PMC4064819  PMID: 24884511
5.  Data quality and confirmatory factor analysis of the Danish EUROPEP questionnaire on patient evaluation of general practice 
The Danish version of the 23-item EUROPEP questionnaire measuring patient evaluation of general practice has not been evaluated with regard to psychometric properties. This study aimed to assess data quality and internal consistency and to validate the proposed factorial structure.
General practice in Denmark.
A total of 703 general practitioners (GPs). Some 83 480 questionnaires were distributed to consecutive patients aged 18 or more attending practice during the daytime. A total of 56 594 eligible patients responded (67.8%).
Main outcome measures
Data quality (mean, median, item response, missing, floor and ceiling effects), internal consistency (Cronbach's alpha and average inter-item correlation), item-rest correlations. Model fit from confirmatory factor analysis (CFA).
The distribution was skewed to the left for almost all items with a small floor effect (0.1–9.3%) and a ceiling effect larger than 15% (18.6–56.3%). Item response was high. For seven items “not applicable/relevant” represented more than 10% of the answers. Internal consistency was good. Item-rest correlations were below 0.60 for three items, and four items had lower correlations with their own domain than with other domains. CFA showed that four domains were highly correlated and that model fit was good for two indices (TLI and SRMR), acceptable for one index (CFI), and poor for three indices (chi-squared, RMSEA and WRMR).
This study revealed high ceiling effects, a few items with low item-rest correlation and low item discriminant validity, and an uncertain model fit. There seems to be a need for developing response categories to bring down the ceiling effect and it is also unclear how to use the proposed domains. Future research should focus on evaluating the factorial structure when ceiling effect has been lowered, on whether items should be deleted, and on assessing the unidimensionality of each domain.
PMCID: PMC3409606  PMID: 18759161
Denmark; factor analysis; family practice; patient evaluation; questionnaires
6.  The Development and Validation of a More Discriminating Functional Hip Score for Research 
HSS Journal  2012;8(3):198-205.
Total hip arthroplasty (THA) is a commonly performed procedure with increasing frequency in the young adult. While most available outcome measures can document postoperative improvement in pain and function, they do not measure the ability to perform high-demand activities.
We present and validate a user-friendly discriminating hip scoring system (the functional hip score) for use in younger, “high-demand” patients undergoing hip arthroplasty surgery.
We studied 38 subjects without any hip symptoms and 72 patients undergoing THA for osteoarthritis of the hip. Preprocedure and postprocedure scores were collected in the latter cohort of patients. SF-36 and WOMAC scores were used to validate our functional scoring system. The functional hip score was tested for internal consistency, reliability, and criterion validity.
The functional hip score had high test–retest reliability, internal consistency, and criterion validity. This can be used to measure functional outcome in the younger high-demand adult patient undergoing THA.
Our discriminating functional hip score can reliably measure improvement in hip function in the younger high-demand adult. Current scoring systems have ceiling effects and are unable to differentiate a high performing hip replacement from the routine hip replacement. The use of functional tasks that are measured objectively allows better documentation of improvement in hip function.
PMCID: PMC3470667  PMID: 24082861
outcomes; functional scores; hip outcomes; young adult hip
7.  The Harris hip score: Do ceiling effects limit its usefulness in orthopedics? 
Acta Orthopaedica  2010;81(6):703-707.
Background and purpose
The Harris hip score (HHS), a disease-specific health status scale that is frequently used to measure the outcome of total hip arthroplasty, has never been validated properly. A questionnaire is suitable only when all 5 psychometric properties are of sufficient quality. We questioned the usefulness of the HHS by investigating its content validity.
We performed a systematic review based on a literature search in PubMed, Embase, and the Cochrane Library for descriptive studies published in 2007. 54 studies (59 patient groups) met our criteria and were included in the data analysis. To determine the content validity, we calculated the ceiling effect (percentage) for each separate study and we pooled data to measure the weighted mean. A subanalysis of indications for THA was performed to differentiate the populations for which the HHS would be suitable and for which it would not. A ceiling effect of 15% or less was considered to be acceptable.
Over half the studies (31/59) revealed unacceptable ceiling effects. Pooled data across the studies included (n = 6,667 patients) suggested ceiling effects of 20% (95%CI: 18–22). Ceiling effects were greater (32%, 95%CI:12–52) in those patients undergoing hip resurfacing arthroplasty.
Although the Harris hip score is widely used in arthroplasty research on outcomes, ceiling effects are common and these severely limit its validity in this field of research.
PMCID: PMC3216080  PMID: 21110703
8.  Recovery Expectations of Hip Resurfacing Compared to Total Hip Arthroplasty: A Matched Pair Study 
Arthritis care & research  2011;63(12):1753-1757.
Expectations of higher activity levels associated with hip resurfacing arthroplasty (HRA) may be driving better outcomes in this group compared to total hip arthroplasty (THA). Previous studies evaluated expectations before consulting with the surgeon, although these expectations are likely unrealistic and would change after the consultation. We compared HRA and THA patient expectation after consultation with the surgeon.
In a prospective registry setting, patients awaiting HRA were matched to THA patients on age, sex, and preoperative Lower Extremity Activity Scale score (range 1–18, 18 highest activity level). Patients completed a validated 18-item expectations survey preoperatively. Mean overall expectations scores were first compared. Exploratory factor analysis (EFA) was then performed to determine if grouping of individual expectations items represented meaningfully different underlying factors in the 2 groups.
We matched 123 pairs. Mean expectation scores were similar (HRA: 85.2±15.5, THA: 87.3±13.9; p-value=0.249). EFA showed that HRA and THA patients shared in common expectations of 1) pain relief and improvement in daily activities (9 items) and 2) eliminating pain medications, the need for cane and improving sexual activity (3 items). THA patients perceived the remaining 6 items as an overall third expectation of participation in higher-level activities. However, HRA patients perceived a fourth expectation of normal range of motion (2 items) independent of the other higher-level activities (4 items).
Even after consulting with a surgeon, patients’ expectations differed between HRA and THA patients regarding higher-level activities. More counseling of patients seeking hip arthroplasty is thus needed.
PMCID: PMC3227755  PMID: 21905257
9.  A New High-flexion Knee Scoring System to Eliminate the Ceiling Effect 
Various scoring systems document improvement after TKA, but most are associated with a ceiling effect that may fail to distinguish between patients having different levels of knee function after TKA. We therefore developed a new scoring system for patients with higher levels of flexion to eliminate ceiling effects observed with current systems.
The purposes of this study were (1) to determine whether the high-flexion knee score eliminates the ceiling effect, (2) to assess the validity and responsiveness of the high-flexion knee score, and (3) to determine whether the high-flexion knee score can aid in differentiation of the knee status of patients at the ceiling level.
We prospectively studied 165 patients with 201 well-functioning knees who had undergone primary TKA. We obtained Knee Society scores, WOMAC scores, Feller scores, SF-36 scores, and high-flexion knee scores for all patients. The high-flexion knee score includes items that reflect knee function in the high functional range, such as sitting on or rising from the floor, squatting, or kneeling. We determined the ceiling effects and score distributions of various scoring systems. We performed a convergent validity test of the high-flexion knee score by correlation analysis with these various scoring systems. Responsiveness of the high-flexion knee score was assessed by correlation analysis of changes in various scoring systems. To determine whether the high-flexion knee score can aid in differentiation of knee status of patients at the ceiling level, relative responsiveness of the various scores in the ceiling versus below the ceiling range was determined.
The high-flexion knee score showed no ceiling effect, whereas the other systems did. Addition of the high-flexion knee score to the other scoring systems eliminated these ceiling effects and resulted in more normalized score distributions. The high-flexion knee score correlated (r = −0.77) with WOMAC in postoperative scores, and it also correlated with the changes in WOMAC (r = −0.69) and SF-36 physical functioning (r = 0.62). The correlation of WOMAC score with SF-36 physical function score was lower in patients at the ceiling level of the Knee Society knee score and Knee Society function score, compared with the correlation at below-ceiling range, whereas the high-flexion knee score maintained a correlation with the SF-36 physical function score, even at the ceiling level of the Knee Society knee score and Knee Society function score.
Compared with other systems, the high-function knee score appears valid for evaluating the knee status in the high-flexion range. Our data suggest the high-flexion knee score differentiates among the knee status in the high-function range. Furthermore, the high-function knee score eliminates the ceiling effect of the currently used scoring tools, and thus may be useful when combined with other scoring systems.
Level of Evidence
Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
Electronic supplementary material
The online version of this article (doi:10.1007/s11999-011-2203-5) contains supplementary material, which is available to authorized users.
PMCID: PMC3254737  PMID: 22125252
10.  Metal-on-Metal Total Hip Resurfacing Arthroplasty 
Executive Summary
The objective of this review was to assess the safety and effectiveness of metal on metal (MOM) hip resurfacing arthroplasty for young patients compared with that of total hip replacement (THR) in the same population.
Clinical Need
Total hip replacement has proved to be very effective for late middle-aged and elderly patients with severe degenerative diseases of the hips. As indications for THR began to include younger patients and those with a more active life style, the longevity of the implant became a concern. Evidence suggests that these patients experience relatively higher rates of early implant failure and the need for revision. The Swedish hip registry, for example, has demonstrated a survival rate in excess of 80% at 20 years for those aged over 65 years, whereas this figure was 33% by 16 years in those aged under 55 years.
Hip resurfacing arthroplasty is a bone-conserving alternative to THR that restores normal joint biomechanics and load transfer. The technique has been used around the world for more than 10 years, specifically in the United Kingdom and other European countries.
The Technology
Metal-on-metal hip resurfacing arthroplasty is an alternative procedure to conventional THR in younger patients. Hip resurfacing arthroplasty is less invasive than THR and addresses the problem of preserving femoral bone stock at the initial operation. This means that future hip revisions are possible with THR if the initial MOM arthroplasty becomes less effective with time in these younger patients. The procedure involves the removal and replacement of the surface of the femoral head with a hollow metal hemisphere, which fits into a metal acetabular cup.
Hip resurfacing arthroplasty is a technically more demanding procedure than is conventional THR. In hip resurfacing, the femoral head is retained, which makes it much more difficult to access the acetabular cup. However, hip resurfacing arthroplasty has several advantages over a conventional THR with a small (28 mm) ball. First, the large femoral head reduces the chance of dislocation, so that rates of dislocation are less than those with conventional THR. Second, the range of motion with hip resurfacing arthroplasty is higher than that achieved with conventional THR.
A variety of MOM hip resurfacing implants are used in clinical practice. Six MOM hip resurfacing implants have been issued licences in Canada.
Review Strategy
A search of electronic bibliographies (OVID Medline, Medline In-Process and Other Non-Indexed Citations, Embase, Cochrane CENTRAL and DSR, INAHTA) was undertaken to identify evidence published from Jan 1, 1997 to October 27, 2005. The search was limited to English-language articles and human studies. The literature search yielded 245 citations. Of these, 11 met inclusion criteria (9 for effectiveness, 2 for safety).
The result of the only reported randomized controlled trial on MOM hip resurfacing arthroplasty could not be included in this assessment, because it used a cemented acetabular component, whereas in the new generation of implants, a cementless acetabular component is used. After omitting this publication, only case series remained.
Summary of Findings
Health Outcomes
The Harris hip score and SF-12 are 2 measures commonly used to report health outcomes in MOM hip resurfacing arthroplasty studies. Other scales used are the Oxford hip score and the University of California Los Angeles hip score.
The case series showed that the mean revision rate of MOM hip resurfacing arthroplasty is 1.5% and the incidence of femoral neck fracture is 0.67%. Across all studies, 2 cases of osteonecrosis were reported. Four studies reported improvement in Harris hip scores. However, only 1 study reported a statistically significant improvement. Three studies reported improvement in SF-12 scores, of which 2 reported a significant improvement. One study reported significant improvement in UCLA hip score. Two studies reported postoperative Oxford hip scores, but no preoperative values were reported.
None of the reviewed studies reported procedure-related deaths. Four studies reported implant survival rates ranging from 94.4% to 99.7% for a follow-up period of 2.8 to 3.5 years. Three studies reported on the range of motion. One reported improvement in all motions including flexion, extension, abduction-adduction, and rotation, and another reported improvement in flexion. Yet another reported improvement in range of motion for flexion abduction-adduction and rotation arc. However, the author reported a decrease in the range of motion in the arc of flexion in patients with Brooker class III or IV heterotopic bone (all patients were men).
Safety of Metal-on-Metal Hip Resurfacing Arthroplasty
There is a concern about metal wear debris and its systemic distribution throughout the body. Detectable metal concentrations in the serum and urine of patients with metal hip implants have been described as early as the 1970s, and this issue is still controversial after 35 years.
Several studies have reported high concentration of cobalt and chromium in serum and/or urine of the patients with metal hip implants. Potential toxicological effects of the elevated metal ions have heightened concerns about safety of MOM bearings. This is of particular concern in young and active patients in whom life expectancy after implantation is long.
Since 1997, 15 studies, including 1 randomized clinical trial, have reported high levels of metal ions after THR with metal implants. Some of these studies have reported higher metal levels in patients with loose implants.
Adverse Biological Effects of Cobalt and Chromium
Because patients who receive a MOM hip arthroplasty are shown to be exposed to high concentrations of metallic ions, the Medical Advisory Secretariat searched the literature for reports of adverse biological effects of cobalt and chromium. Cobalt and chromium make up the major part of the metal articulations; therefore, they are a focus of concern.
Risk of Cancer
To date, only one study has examined the incidence of cancer after MOM and polyethylene on metal total hip arthroplasties. The results were compared to that of general population in Finland. The mean duration of follow-up for MOM arthroplasty was 15.7 years; for polyethylene arthroplasty, it was 12.5 years. The standardized incidence ratio for all cancers in the MOM group was 0.95 (95% CI, 0.79–1.13). In the polyethylene on metal group it was 0.76 (95% CI, 0.68–0.86). The combined standardized incidence ratio for lymphoma and leukemia in the patients who had MOM THR was 1.59 (95% CI, 0.82–2.77). It was 0.59 (95% CI, 0.29–1.05) for the patients who had polyethylene on metal THR. Patients with MOM THR had a significantly higher risk of leukemia. All patients who had leukemia were aged over than 60 years.
Cobalt Cardiotoxicity
Epidemiological Studies of Myocardiopathy of Beer Drinkers
An unusual type of myocardiopathy, characterized by pericardial effusion, elevated hemoglobin concentrations, and congestive heart failure, occurred as an epidemic affecting 48 habitual beer drinkers in Quebec City between 1965 and 1966. This epidemic was directly related the consumption of a popular beer containing cobalt sulfate. The epidemic appeared 1 month after cobalt sulfate was added to the specific brewery, and no further cases were seen a month after this specific chemical was no longer used in making this beer. A beer of the same name is made in Montreal, and the only difference at that time was that the Quebec brand of beer contained about 10 times more cobalt sulphate. Cobalt has been added to some Canadian beers since 1965 to improve the stability of the foam but it has been added in larger breweries only to draught beer. However, in small breweries, such as those in Quebec City, separate batches were not brewed for bottle and draught beer; therefore, cobalt was added to all of the beer processed in this brewery.
In March 1966, a committee was appointed under the chairmanship of the Deputy Minister of Health for Quebec that included members of the department of forensic medicine of Quebec’s Ministry of Justice, epidemiologists, members of Food and Drug Directorate of Ottawa, toxicologists, biomedical researchers, pathologists, and members of provincial police. Epidemiological studies were carried out by the Provincial Ministry of Health and the Quebec City Health Department.
The association between the development of myocardiopathy and the consumption of the particular brand of beer was proven. The mortality rate of this epidemic was 46.1% and those who survived were desperately ill, and recovered only after a struggle for their lives.
Similar cases were seen in Omaha (Nebraska). The epidemic started after a cobalt additive was used in 1 of the beers marketed in Nebraska. Sixty-four patients with the clinical diagnosis of alcoholic myocardiopathy were seen during an 18-month period (1964–1965). Thirty of these patients died. The first patient became ill within 1 month after cobalt was added to the beer, and the last patient was seen within 1 month of withdrawal of cobalt.
A similar epidemic occurred in Minneapolis, Minnesota. Between 1964 and 1967, 42 patients with acute heart failure were admitted to a hospital in Minneapolis, Minnesota. Twenty of these patients were drinking 6 to 30 bottles per day of a particular brand of beer exclusively. The other 14 patients also drank the same brand of beer, but not exclusively. The mortality rate from the acute illness was 18%, but late deaths accounted for a total mortality rate of 43%. Examination of the tissue from these patients revealed markedly abnormal changes in myofibrils (heart muscles), mitochondria, and sarcoplasmic reticulum.
In Belgium, a similar epidemic was reported in 1966, in which, cobalt was used in some Belgian beers. There was a difference in mortality between the Canadian or American epidemic and this series. Only 1 of 24 patients died, 1.5 years after the diagnosis. In March 1965, at an international meeting in Brussels, a new heart disease in chronic beer drinkers was described. This disease consists of massive pericardial effusion, low cardiac output, raised venous pressure, and polycythemia in some cases. This syndrome was thought to be different from the 2 other forms of alcoholic heart disease (beriberi and a form characterized by myocardial fibrosis).
The mystery of the above epidemics as stated by investigators is that the amount of cobalt added to the beer was below the therapeutic doses used for anemia. For example, 24 pints of Quebec brand of beer in Quebec would contain 8 mg of cobalt chloride, whereas an intake of 50 to 100 mg of cobalt as an antianemic agent has been well tolerated. Thus, greater cobalt intake alone does not explain the occurrence of myocardiopathy. It seems that there are individual differences in cobalt toxicity. Other features, like subclinical alcoholic heart disease, deficient diet, and electrolyte imbalance could have been precipitating factors that made these patients susceptible to cobalt’s toxic effects.
In the Omaha epidemic, 60% of the patients had weight loss, anorexia, and occasional vomiting and diarrhea 2 to 6 months before the onset of cardiac symptoms. In the Quebec epidemic, patients lost their appetite 3 to 6 months before the diagnosis of myocardiopathy and developed nausea in the weeks before hospital admission. In the Belgium epidemic, anorexia was one of the most predominant symptoms at the time of diagnosis, and the quality and quantity of food intake was poor. Alcohol has been shown to increase the uptake of intracoronary injected cobalt by 47%. When cobalt enters the cells, calcium exits; this shifts the cobalt to calcium ratio. The increased uptake of cobalt in alcoholic patients may explain the high incidence of cardiomyopathies in beer drinkers’ epidemics.
As all of the above suggest, it may be that prior chronic exposure to alcohol and/or a nutritionally deficient diet may have a marked synergistic effect with the cardiotoxicity of cobalt.
MOM hip resurfacing arthroplasty has been shown to be an effective arthroplasty procedure as tested in younger patients.
However, evidence for effectiveness is based only on 7 case series with short duration of follow-up (2.8–3.5 years). There are no RCTs or other well-controlled studies that compare MOM hip resurfacing with THR.
Revision rates reported in the MOM studies using implants currently licensed in Canada (hybrid systems, uncemented acetabular, and cemented femoral) range from 0.3% to 3.6% for a mean follow-up ranging from 2.8 to 3.5 years.
Fracture of femoral neck is not very common; it occurs in 0.4% to 2.2% of cases (as observed in a short follow-up period).
All the studies that measured health outcomes have reported improvement in Harris Hip and SF-12 scores; 1 study reported significant reduction in pain and improvement in function, and 2 studies reported significant improvement in SF-12 scores. One study reported significant improvement in UCLA Hip scores.
Concerns remain on the potential adverse effects of metal ions. Longer-term follow-up data will help to resolve the inconsistency of findings on adverse effects, including toxicity and carcinogenicity.
Ontario-Based Economic Analysis
The device cost for MOM ranges from $4,300 to $6,000 (Cdn). Traditional hip replacement devices cost about $2,000 (Cdn). Using Ontario Case Costing Initiative data, the total estimated costs for hip resurfacing surgery including physician fees, device fees, follow-up consultation, and postsurgery rehabilitation is about $15,000 (Cdn).
Cost of Total Hip Replacement Surgery in Ontario
MOM hip arthroplasty is generally recommended for patients aged under 55 years because its bone-conserving advantage enables patients to “buy time” and hence helps THRs to last over the lifetime of the patient. In 2004/2005, 15.9% of patients who received THRs were aged 55 years and younger. It is estimated that there are from 600 to 1,000 annual MOM hip arthroplasty surgeries in Canada with an estimated 100 to 150 surgeries in Ontario. Given the increased public awareness of this device, it is forecasted that demand for MOM hip arthroplasty will steadily increase with a conservative estimate of demand rising to 1,400 cases by 2010 (Figure 10). The net budget impact over a 5-year period could be $500,000 to $4.7 million, mainly because of the increasing cost of the device.
Projected Number of Metal-on-Metal Hip Arthroplasty Surgeries in Ontario: to 2010
PMCID: PMC3379532  PMID: 23074495
11.  Sense of competence questionnaire among informal caregivers of older adults with dementia symptoms: A psychometric evaluation 
The Sense of Competence Questionnaire (SCQ) was originally developed for informal caregivers of patients with diagnosed dementia. In order to study the validity and usefulness of the SCQ when applied to informal caregivers of older adults with dementia symptoms (i.e. cognitive impairment, pre-diagnostic dementia or dementia in its early stages), we investigated the construct validity, feasibility, subscales, homogeneity, and floor and ceiling effects in this new target population.
A psychometric evaluation was performed among 99 informal caregivers. To investigate construct validity, hypotheses were tested, concerning the association between sense of competence and burden, mental quality of life, depressive symptoms, and mastery. To investigate feasibility, response rate and the proportion of missing data were explored for each item. An exploratory principal component analysis was used to investigate whether the SCQ comprises the three subscales established in previous studies. Homogeneity was assessed for each subscale with Cronbach's α and item-total correlations. Floor and ceiling effects were explored.
Most hypotheses on construct validity were rejected. Only the subscale 'consequences of involvement in care' was found to be partly valid. Feasibility: 93 out of 99 persons completed the SCQ. The proportion of unanswered items per item ranged from 0 – 3%. Subscales: the SCQ comprises the three expected subscales. Homogeneity: Cronbach's alpha and item-total correlations of the three subscales were satisfactory. A ceiling effect occurred on the subscale 'satisfaction with the care recipient'.
The three subscales of the SCQ showed good homogeneity and feasibility, but their validity is insufficient: only the subscale 'consequences of involvement' was found to be partly valid. The two other subscales might not be relevant yet for the new target population, since many of the items on these scales refer to problem behaviour and problematic interactions. Our message to clinicians is not to use these subscales.
PMCID: PMC1947979  PMID: 17645790
12.  Neck Pain and Disability Scale and Neck Disability Index: validity of Dutch language versions 
European Spine Journal  2011;21(1):93-100.
To investigate the validity of the Neck Pain and Disability Scale Dutch Language Version (NPAD-DLV) and the Neck Disability Index (NDI)-DLV.
NPAD–DLV, NDI–DLV, Short-Form-36 Health Survey (SF-36)-DLV, visual analog scale (VAS)pain and VASdisability were administered to 112 patients with non-specific chronic neck pain in an outpatient tertiary rehabilitation setting. Twenty seven hypotheses were formulated regarding validity. NPAD–DLV and NDI–DLV were evaluated for content validity (normal distribution total scores, missing items, floor and ceiling effects), internal consistency (Cronbach’s alpha and Spearman Item–total correlations), construct validity (Pearson correlations with SF-36 domains, VASpain and VASdisability and Pearson correlation between total scores of NPAD–DLV and NDI–DLV).
NPAD–DLV and NDI–DLV scores were distributed normally. Missing items were negligible. Floor and ceiling effects were absent in NPAD–DLV and in NDI–DLV two items had floor effects and one item had a ceiling effect. Cronbach’s alpha of NPAD–DLV was 0.93 and of NDI–DLV 0.83. Item–total correlations ranged for NPAD–DLV from 0.45 to 0.73 and for NDI–DLV from 0.40 to 0.64. The correlation between, respectively, NPAD–DLV and NDI–DLV and: SF-36 domains ranged from −0.36 to −0.70 and from −0.34 to −0.63; VASpain was 0.54 and 0.43; VASdisability was 0.57 and 0.52. The correlation between the total scores of NPAD–DLV and NDI–DLV was 0.77. Twenty six hypotheses were not rejected and one hypothesis was rejected.
The NPAD–DLV and NDI–DLV are valid measures of self-reported neck-pain related disability.
PMCID: PMC3252449  PMID: 21814745
Validation study; Assessment; Chronic pain; Short-Form-36 health survey
13.  Development and assessment of floor and ceiling items for the PROMIS physical function item bank 
Arthritis Research & Therapy  2013;15(5):R144.
Disability and Physical Function (PF) outcome assessment has had limited ability to measure functional status at the floor (very poor functional abilities) or the ceiling (very high functional abilities). We sought to identify, develop and evaluate new floor and ceiling items to enable broader and more precise assessment of PF outcomes for the NIH Patient-Reported-Outcomes Measurement Information System (PROMIS).
We conducted two cross-sectional studies using NIH PROMIS item improvement protocols with expert review, participant survey and focus group methods. In Study 1, respondents with low PF abilities evaluated new floor items, and those with high PF abilities evaluated new ceiling items for clarity, importance and relevance. In Study 2, we compared difficulty ratings of new floor items by low functioning respondents and ceiling items by high functioning respondents to reference PROMIS PF-10 items. We used frequencies, percentages, means and standard deviations to analyze the data.
In Study 1, low (n = 84) and high (n = 90) functioning respondents were mostly White, women, 70 years old, with some college, and disability scores of 0.62 and 0.30. More than 90% of the 31 new floor and 31 new ceiling items were rated as clear, important and relevant, leaving 26 ceiling and 30 floor items for Study 2. Low (n = 246) and high (n = 637) functioning Study 2 respondents were mostly White, women, 70 years old, with some college, and Health Assessment Questionnaire (HAQ) scores of 1.62 and 0.003. Compared to difficulty ratings of reference items, ceiling items were rated to be 10% more to greater than 40% more difficult to do, and floor items were rated to be about 12% to nearly 90% less difficult to do.
These new floor and ceiling items considerably extend the measurable range of physical function at either extreme. They will help improve instrument performance in populations with broad functional ranges and those concentrated at one or the other extreme ends of functioning. Optimal use of these new items will be assisted by computerized adaptive testing (CAT), reducing questionnaire burden and insuring item administration to appropriate individuals.
PMCID: PMC3978724  PMID: 24286166
14.  A randomized pilot study of a comprehensive postoperative exercise program compared with usual care following primary total hip arthroplasty in subjects less than 65 years of age: feasibility, selection of outcome measures and timing of assessment 
Total Hip Arthroplasty (THA) is being used more commonly in younger higher demand patients. The purpose of this randomized pilot study was to explore a) feasibility of comprehensive postoperative rehabilitation compared to usual care following primary THA in subjects <65 years, b) appropriate outcome measures including performance-based measures and c) timing of assessments.
21 subjects who underwent primary THA were randomized to receive a three-month out-patient rehabilitation program (Intervention) or usual postoperative care (Control). Subjects were assessed preoperatively, six-weeks postoperatively (Pre-intervention) and four and 12 months postoperatively (Post-intervention). Self-report measures were the Western Ontario McMaster Osteoarthritis Index (WOMAC) and Rand 36-Item Health Survey (RAND-36). Performance-based measures included lower extremity strength, walking speed and endurance, and gait laboratory assessment.
Ten Control and 11 Intervention subjects with an average age of 53.4 (SD9.3) years were randomized. All Intervention subjects completed the program without adverse effects. Although no statistically significantly results were reported, four months postoperatively, Intervention subjects had clinically important differences (CID) in strength compared with Control subjects. Walking endurance, WOMAC and RAND scores improved significantly with no CID noted between groups. Ten (48%) subjects reported a ceiling effect on the WOMAC (9 (43%) subjects on Pain; 1 (5%) subject on Function). No group CID were noted in gait measures.
Our recommendations would be that performance-based strength measures should be considered for the primary outcome in this younger cohort. Because of the ceiling effects with WOMAC Pain, a different pain measure is indicated. Other more challenging functional performance-based tests should be considered such as a more prolonged endurance test. There is merit in one-year follow-up as strength improved after four months in both groups.
PMCID: PMC4060584  PMID: 24889213
Total hip arthroplasty; Rehabilitation; Performance-based; Health related quality of life; Complex interventions
15.  Operative diagnosis for revision total hip arthroplasty is associated with patient-reported outcomes (PROs) 
Little is known about the impact of the reason for revision total hip arthroplasty (THA) on the outcomes following revision THA. In this study, our objective was to assess the association of operative diagnosis with patient-reported outcomes (PROs) after revision THA.
We used prospectively collected data from the Mayo Clinic Total Joint Registry that collects pre- and post-operative pain and function outcomes using a validated Hip questionnaire, on all revision THAs from 1993–2005. We used logistic regression to assess the odds of moderate-severe index hip pain and moderate-severe limitation in activities of daily living (ADLs) 2- and 5-years after revision THA. We calculated odds ratios (OR) and 95% confidence intervals (CIs).
For the 2- and 5-year cohorts, the operative diagnosis was loosening/wear/osteolysis in 73% and 75%; dislocation/bone or prosthesis fracture/instability or non-union in 17% and 15%; and failed prior arthroplasty with components removed/infection in 11% and 11%, respectively. In multivariable-adjusted analyses that included preoperative ADL limitations, compared to patients with loosening/wear/osteolysis, patients with dislocation/fracture/instability/non-union had OR of 2.2 (95% CI, 1.3-3.5; p = 0.002) for overall moderate-severe ADL limitation and those with failed prior arthroplasty/infection had OR of 1.6 (95% CI, 1.0-2.8; p = 0.06). At 5-years, ORs were lower and differences were no longer significant. Moderate-severe pain did not differ significantly by diagnosis, at 2- or 5-years in multivariable adjusted analyses, with one exception, i.e. failed prior arthroplasty/infection had a trend towards significance with odds ratio of 1.9 (95% CI, 0.9-3.8; p = 0.07).
Operative diagnosis is independently associated with ADL limitations, but not pain, at 2-years after revision THA. Patients should be informed of the risk of poorer short-term outcomes based on their diagnosis.
PMCID: PMC3722075  PMID: 23866848
Total hip replacement; Arthroplasty; Joint replacement; Patient-reported outcomes; Diagnosis
16.  Surgery-Induced Changes and Early Recovery of Hip-Muscle Strength, Leg-Press Power, and Functional Performance after Fast-Track Total Hip Arthroplasty: A Prospective Cohort Study 
PLoS ONE  2013;8(4):e62109.
By measuring very early changes in muscle strength and functional performance after fast-track total hip arthroplasty (THA), post-operative rehabilitation, introduced soon after surgery, can be designed to specifically target identified deficits.
Firstly, to quantify changes (compared to pre-operative values) in hip muscle strength, leg-press power, and functional performance in the first week after THA, and secondly, to explore relationships between the muscle strength changes, and changes in hip pain, systemic inflammation, and thigh swelling.
Prospective, cohort study.
Convenience sample of patients receiving a THA at Copenhagen University Hospital, Hvidovre, Denmark, between March and December 2011.
Thirty-five patients (65.9±7.2 years) undergoing THA.
Main outcome measures
Hip muscle strength, leg-press power, performance-based function, and self-reported disability were determined prior to, and 2 and 8 days after, THA (Day 2 and 8, respectively). Hip pain, thigh swelling, and C-Reactive Protein were also determined.
Five patients were lost to follow-up. Hip muscle strength and leg press power were substantially reduced at Day 2 (range of reductions: 41–58%, P<0.001), but less pronounced at Day 8 (range of reductions: 23–31%, P<0.017). Self-reported symptoms and function (HOOS: Pain, Symptoms, and ADL) improved at Day 8 (P<0.014). Changes in hip pain, C-Reactive Protein, and thigh swelling were not related to the muscle strength and power losses.
Hip muscle strength and leg-press power decreased substantially in the first week after THA – especially at Day 2 – with some recovery at Day 8. The muscle strength loss and power loss were not related to changes in hip pain, systemic inflammation, or thigh swelling. In contrast, self-reported symptoms and function improved. These data on surgery-induced changes in muscle strength may help design impairment-directed, post-operative rehabilitation to be introduced soon after surgery.
Trial Registration NCT01246674.
PMCID: PMC3628341  PMID: 23614020
17.  Impact of co-existent lumbar spine disorders on clinical outcomes and physician charges associated with total hip arthroplasty 
The Spine Journal  2012;12(5):363-369.
Background Context
Despite the common prevalence of lumbar spine and degenerative hip disorders, there are few descriptions of patients with coexisting hip and lumbar spine disorders. The independent economic burden of each disorder is substantial but the financial burden when the disorders are coexisting is unknown.
The purpose of this study is to determine the prevalence of coexisting hip and lumbar spine disorders (LSD) in a large cohort of patients with hip osteoarthritis treated with total hip arthroplasty (THA) and determine the impact on pain and functional THA outcomes and physician charges.
Study Design/Setting
This is a retrospective study performed at a tertiary university.
Patient Sample
3206 patients who underwent total hip replacement from 1996-2008.
Outcome Measures
Self-report measures: Visual Analog Scale. Functional measures: modified Harris Hip Score (mHHS), UCLA hip questionnaire. Economic impact measures: physician medical charges.
International Classification of Diseases (ICD-9) billing codes related to LSDs were cross referenced with the 3206 patients who had undergone a THA to determine which patients were also evaluated by a spine specialist. Demographic, hip clinical outcomes and physician charges for patients with THA alone (THA alone) were compared to patients treated with THA and diagnosed with a LSD (THA + LSD).
Of 3206 patients who underwent THA, 566 (18%) were also evaluated by a spine specialist. Of those with a LSD, 334 (59%) were women with an older average age (64.5+13.3yrs) compared to patients treated with THA alone (51%, 58.5+15.5 yrs, P=0.0001). Patients in the THA alone group as compared to the THA+ LSD group had greater improvement in the mHHS (P =0.0001), UCLA score (P =0.0001) and pain (P=0.0001). Patients in the THA+LSD group incurred on average $2,668 more in charges per episode of care as compared to patients in the THA alone group. (P<0.001) Patients in the THA+LSD group had more days per episode of care (P=0.001).
Patients undergoing THA alone had greater improvement in function and pain relief with fewer medical charges as compared to patients undergoing a THA and treatment for a LSD. The prevalence of coexisting hip and spine disorders is likely higher than currently documented. Further study is needed in order to improve therapeutic recommendations and determine the potential for reduction in medical expenses associated with concurrent treatment of hip osteoarthritis and lumbar spine disorders.
PMCID: PMC3340523  PMID: 22227176
hip; arthroplasty; lumbar spine; low back pain; osteoarthritis; hip-spine syndrome
18.  Bosworth hip shelf arthroplasty in adult dysplastic hips: ten to twenty three year results 
International Orthopaedics  2012;36(12):2425-2431.
Hip shelf arthroplasty is currently considered to be a salvage procedure. The aim of the study is to present outcomes of Bosworth hip shelf arthroplasty in adolescent dysplastic hips with a minimum ten-year follow-up.
The basic group comprised 25 hips in 18 patients with the mean age of 31 years (range, 16–52) at the time of operation. Subgroup A included 20 hips that were evaluated prior to operation as spherical, centric hips without osteoarthritic changes (acetabular dysplasia). The heterogeneous subgroup B comprised five hips. Of these, three hips were evaluated as aspheric, without osteoarthritic changes, and two hips as aspheric, with osteoarthritic changes of grade 2 according to Tönnis. In addition, two hips in subgroup B were evaluated as decentred (subluxated), one hip without and one hip with osteoarthritic changes. The mean follow-up was 15 years (range, ten–23).
In subgroup A, the positive effect of operation had lasted at the time of the final follow-up for ten to 22 years postoperatively (average follow-up 14 years) in 19 hips. Only one female patient, 46 years old at the time of operation, developed hip osteoarthritis within ten years, that was treated by THA. In subgroup B, a lasting positive effect of operation was recorded in two cases at the time of the final follow-up (12 and 15 years). The third female patient with an aspheric and decentred hip developed severe hip osteoarthritis 21 years after shelf procedure that was treated by THA. In two patients who had hip osteoarthritis already before the operation, the positive effect of the shelf procedure survived over 13 and 20 years. Although hip osteoarthritis progressed, THA was performed as late as 15 and 23 years after the shelf procedure. The mean Harris hip score in 21 hips with a still functional hip shelf was 68 (range, 56–82) before and 90 (range, 76–100) after the surgery.
The best outcomes of Bosworth hip shelf arthroplasty may be expected in a dysplastic spherical centred hip without osteoarthritic changes. In the presence of asphericity, decentration and osteoarthritic changes, neither the effect of the surgery nor its survival can be clearly predicted.
PMCID: PMC3508042  PMID: 23093289
19.  The value of short and simple measures to assess outcomes for patients of total hip replacement surgery 
Quality in Health Care : QHC  2000;9(3):146-150.
Objectives—To evaluate the performance of a patient assessed outcome measure, the Oxford Hip Score, in a national study of primary hip replacement surgery.
Design—A survey of patients' health status before undergoing primary hip replacement surgery and three months and one year after surgery.
Setting—143 hospitals in three NHS English regions.
Patients—7151 patients admitted for primary total hip replacement surgery over a period of 13 months from September 1996.
Main measures—For patients, Oxford Hip Score and satisfaction with hip replacement and, for surgeons, American Anesthiologists' Society (ASA) classification of physical status.
Results—The response rates to the postal questionnaire at three and 12 months follow up were 85.2% and 80.7%, respectively. Including all three administrations of the questionnaire, all except two items of the Oxford Hip Score were completed by 97% or more respondents and only one item at one administration appeared marginally to reduce the reliability of the score. The effect sizes for changes in the score from baseline to three months was 2.50 and to 12 months was 3.05. Patients rated by surgeons as being healthy preoperatively by the ASA classification were somewhat more likely to return a completed questionnaire at three months (79.4% versus 75.3%) and 12 months (72.4% versus 70.3%) than those rated as having poorer health.
Conclusions—Overall there was little evidence of difficulties for patients in completing the Oxford Hip Score or of unreliable data, except in relation to one questionnaire item. The instrument was very responsive to change over time and score changes for the Oxford Hip Score related well to patients' satisfaction with their surgery. The instrument is an appropriate measure in terms of validity, responsiveness, and feasibility for evaluating total hip replacement from the perspective of the patient.
Key Words: total hip replacement surgery; Oxford Hip Score; questionnaire; assessment
PMCID: PMC1743526  PMID: 10980074
20.  Reliability and validity of the cross-culturally adapted Italian version of the Core Outcome Measures Index 
European Spine Journal  2011;21(Suppl 6):737-749.
Patient-orientated outcome questionnaires are essential for the assessment of treatment success in spine care. Standardisation of the instruments used is necessary for comparison across studies and in registries. The Core Outcome Measures Index (COMI) is a short, multidimensional outcome instrument validated for patients with spinal disorders and is the recommended outcome instrument in the Spine Society of Europe Spine Tango Registry; currently, no validated Italian version exists. A cross-cultural adaptation of the COMI into Italian was carried out using established guidelines. 96 outpatients with chronic back problems (>3 months) were recruited from five practices in Switzerland and Italy. They completed the newly translated COMI, the Roland Morris disability (RM), adjectival pain rating, WHO Quality of Life (WHOQoL), EuroQoL-5D, and EuroQoL-VAS scales. Reproducibility was assessed in a subgroup of 63 patients who returned a second questionnaire within 1 month and indicated no change in back status on a 5-point Likert-scale transition question. The COMI scores displayed no floor or ceiling effects. On re-test, the responses for each individual domain of the COMI were within one category in 100% patients for “function”, 92% for “symptom-specific well-being”, 100% for “general quality of life”, 90% for “social disability”, and 98% for “work disability”. The intraclass correlation coefficients (ICC2,1) for the COMI back and leg pain items were 0.78 and 0.82, respectively, and for the COMI summary index, 0.92 (95% CI 0.86–0.95); this compared well with 0.84 for RM, 0.87 for WHOQoL, 0.79 for EQ-5D, and 0.77 for EQ-VAS. The standard error of measurement (SEM) for COMI was 0.54 points, giving a ‘‘minimum detectable change’’ for the COMI of 1.5 points. The scores for most of the individual COMI domains and the COMI summary index correlated to the expected extent (0.4–0.8) with the corresponding full-length reference questionnaires (r = 0.45–0.72). The reproducibility of the Italian version of the COMI was comparable to that published for the German and Spanish versions. The COMI scores correlated in the expected manner with existing but considerably longer questionnaires suggesting adequate convergent validity for the COMI. The Italian COMI represents a practical, reliable, and valid tool for use with Italian-speaking patients and will be of value for international studies and surgical registries.
PMCID: PMC3535210  PMID: 21409562
Back pain; Outcome questionnaire; Cross-cultural adaptation; Reliability; Validity
21.  Validity, reliability, and responsiveness of a self-reported foot and ankle score (SEFAS) 
Acta Orthopaedica  2012;83(2):197-203.
Background and purpose
A questionnaire was introduced by the New Zealand Arthroplasty Registry for use when evaluating the outcome of total ankle replacement surgery. We evaluated the reliability, validity, and responsiveness of the modified Swedish version of the questionnaire (SEFAS) in patients with osteoarthritis or inflammatory arthritis before and/or after their ankle was replaced or fused.
Patients and methods
The questionnaire was translated into Swedish and cross-culturally adapted according to a standardized procedure. It was sent to 135 patients with ankle arthritis who were scheduled for or had undergone surgery, together with the foot and ankle outcome score (FAOS), the short form 36 (SF-36) score, and the EuroQol (EQ-5D) score. Construct validity was evaluated with Spearman’s correlation coefficient when comparing SEFAS with FAOS, SF-36, and EQ-5D, content validity by calculating floor and ceiling effects, test-retest reliability with intraclass correlation coefficient (ICC), internal consistency with Cronbach’s alpha (n = 62), agreement by Bland-Altman plot, and responsiveness by effect size and standardized response mean (n = 37).
For construct validity, we correlated SEFAS with the other scores and 70% or more of our predefined hypotheses concerning correlations could be confirmed. There were no floor or ceiling effects. ICC was 0.92 (CI 95%: 0.88–0.95), Cronbach’s alpha 0.96, effect size was 1.44, and the standardized response mean was 1.00.
SEFAS is a self-reported foot and ankle score with good validity, reliability and responsiveness, indicating that the score can be used to evaluate patients with osteoarthritis or inflammatory arthritis of the ankle and outcome of surgery.
PMCID: PMC3339537  PMID: 22313352
22.  The Self-Administered Patient Satisfaction Scale for Primary Hip and Knee Arthroplasty 
Arthritis  2011;2011:591253.
Introduction. The objective of this study was to develop a short self-report questionnaire for evaluating patient satisfaction with the outcome of hip and knee replacement surgery. Methods. This scale consists of four items focusing on satisfaction with the extent of pain relief, improvement in ability to perform home or yard work, ability to perform recreational activities, and overall satisfaction with joint replacement. This instrument does not measure satisfaction with process of care. The responses are scored on a Likert scale, with the total score ranging from 25 to 100 per question. The instrument was tested on 1700 patients undergoing primary total hip and total knee replacement surgery, evaluated preoperatively, at 12 weeks, and one year postoperatively. Psychometric testing included internal consistency, measured with Cronbach's alpha, and convergent validity, measured by correlation with changes in measures of health status between the preoperative, 12-week, and one-year evaluations. Results. The internal consistency (reliability) of the scale, measured by the Cronbach's alpha, ranged from 0.86 to 0.92. The scale demonstrated substantial ceiling effects at 1 year. The scale scores correlated modestly with the absolute SF-36 PCS and WOMAC scores (ρ = 0.56–0.63 and also with the WOMAC change scores (ρ = 0.38–0.46) at both 12-week and 1-year followups. Conclusions. This instrument is valid and reliable for measuring patient satisfaction following primary hip and knee arthroplasty and could be further evaluated for use with other musculoskeletal interventions.
PMCID: PMC3199955  PMID: 22046521
23.  Does Impact Sport Activity Influence Total Hip Arthroplasty Durability? 
Return to sport is a key patient demand after hip arthroplasty and some patients are even involved in high-impact sports. Although polyethylene wear is related to the number of cycles and the importance of the load, it is unclear whether high-impact sport per se influences THA durability.
Therefore, we compared (1) function between the patients involved in high-impact sports and the patients with lower activities as measured by the Harris hip score (HHS) and the Hip Osteoarthritis Outcome Score (HOOS); (2) linear wear rates; and (3) survivorships considering revision for mechanical failure with radiographic signs of aseptic loosening as the end point.
We retrospectively identified 70 patients who engaged in high-impact sports and 140 with low activity levels from among 843 THAs from a prospectively collected database performed between September 1, 1995, and December 31, 2000. Patients were evaluated at a minimum followup of 10 years (mean, 11 years; range, 10–15 years) by two independent observers. We obtained a HHS and HOOS at each followup.
The mean HOOS was higher in the high-impact group for three of the five subscales of the HOOS. Mean linear wear was higher in the high-impact group than in the low-activities group. We also found a higher number of revisions in the high-activity group.
Our observations confirm concern about the risk of THA mechanical failures related to high-impact sport, and patient and surgeons alike should be aware of these risks of mechanical failures.
Level of Evidence
Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC3462849  PMID: 22535588
24.  Translation, adaptation and validation of the American short form Patient Activation Measure (PAM13) in a Danish version 
BMC Public Health  2009;9:209.
The Patient Activation Measure (PAM) is a measure that assesses patient knowledge, skill, and confidence for self-management. This study validates the Danish translation of the 13-item Patient Activation Measure (PAM13) in a Danish population with dysglycaemia.
358 people with screen-detected dysglycaemia participating in a primary care health education study responded to PAM13. The PAM13 was translated into Danish by a standardised forward-backward translation. Data quality was assessed by mean, median, item response, missing values, floor and ceiling effects, internal consistency (Cronbach's alpha and average inter-item correlation) and item-rest correlations. Scale properties were assessed by Rasch Rating Scale models.
The item response was high with a small number of missing values (0.8–4.2%). Floor effect was small (range 0.6–3.6%), but the ceiling effect was above 15% for all items (range 18.6–62.7%). The α-coefficient was 0.89 and the average inter-item correlation 0.38. The Danish version formed a unidimensional, probabilistic Guttman-like scale explaining 43.2% of the variance. We did however, find a different item sequence compared to the original scale.
A Danish version of PAM13 with acceptable validity and reliability is now available. Further development should focus on single items, response categories in relation to ceiling effects and further validation of reproducibility and responsiveness.
PMCID: PMC2712471  PMID: 19563630
25.  Hip disability and osteoarthritis outcome score (HOOS) – validity and responsiveness in total hip replacement 
The aim of the study was to evaluate if physical functions usually associated with a younger population were of importance for an older population, and to construct an outcome measure for hip osteoarthritis with improved responsiveness compared to the Western Ontario McMaster osteoarthritis score (WOMAC LK 3.0).
A 40 item questionnaire (hip disability and osteoarthritis outcome score, HOOS) was constructed to assess patient-relevant outcomes in five separate subscales (pain, symptoms, activity of daily living, sport and recreation function and hip related quality of life). The HOOS contains all WOMAC LK 3.0 questions in unchanged form. The HOOS was distributed to 90 patients with primary hip osteoarthritis (mean age 71.5, range 49–85, 41 females) assigned for total hip replacement for osteoarthritis preoperatively and at six months follow-up.
The HOOS met set criteria of validity and responsiveness. It was more responsive than WOMAC regarding the subscales pain (SRM 2.11 vs. 1.83) and other symptoms (SRM 1.83 vs. 1.28). The responsiveness (SRM) for the two added subscales sport and recreation and quality of life were 1.29 and 1.65, respectively. Patients ≤ 66 years of age (range 49–66) reported higher responsiveness in all five subscales than patients >66 years of age (range 67–85) (Pain SRM 2.60 vs. 1.97, other symptoms SRM 3.0 vs. 1.60, activity of daily living SRM 2.51 vs. 1.52, sport and recreation function SRM 1.53 vs. 1.21 and hip related quality of life SRM 1.95 vs. 1.57).
The HOOS 2.0 appears to be useful for the evaluation of patient-relevant outcome after THR and is more responsive than the WOMAC LK 3.0. The added subscales sport and recreation function and hip related quality of life were highly responsive for this group of patients, with the responsiveness being highest for those younger than 66.
PMCID: PMC161815  PMID: 12777182

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