The stability of utility scores: test-retest reliability and the interpretation of utility scores in elective total hip arthroplasty

PURPOSES

Are utility scores for hypothetical health states stable over time even when the health of the patient changes dramatically? Can investigators who use scores for hypothetical states be confident about the stability of those scores? The first purpose is to assess the stability of standard gamble utility scores for three hypothetical health states describing mild, moderate, and severe osteoarthritis (OA) (test-retest reliability). How should investigators interpret utility scores? The second purpose is to provide evidence on the marker-state approach to assist in interpreting utility scores.

BACKGROUND

SG scores for three hypothetical marker states and the patient's current state were obtained at multiple times in a longitudinal study of elective total hip arthroplasty (THA). SG scores for current health increased from a mean of 0.59 pre-surgery to 0.76 post-surgery.

METHODS

Test-retest reliability was assessed using the intra-class correlation coefficient (ICC). The effects of time on scores were analysed using an analysis of covariance.

RESULTS

At the group level the marker-state scores were stable. Mean scores for mild, moderate, and severe OA were 0.69, 0.61, and 0.41. With respect to test-retest reliability, ICCs varied from 0.49 to 0.62. In general, time did not affect the scores for the three marker states.

CONCLUSIONS

Group-level standard gamble scores are stable. At the individual level scores for hypothetical health states are somewhat stable over time. The marker states assist in interpretation indicating that, on average, THA converted moderate OA to better than mild.

Patient satisfaction and outcome after septic versus aseptic revision total knee arthroplasty

A consecutive series of revision total knee arthroplasties performed at 3 university-affiliated centers by 3 surgeons was prospectively studied. The same implant was used in all cases. The evaluation included a Knee Society clinical score (KSCS); SF-36; satisfaction survey; and radiographs preoperatively, at 6 and 12 months postoperatively, and annually thereafter. Follow-up averaging 36 months (range, 24-60 months) was obtained in 125 of 138 knees (91%). Twenty-eight knees were infected, and 26 of 28 knees were treated successfully with 2-stage exchange with an interval of 4 to 6 weeks using an antibiotic-impregnated spacer block and intravenous antibiotics. The remaining 99 knees were revised for reasons other than infection, including aseptic component loosening, progressive osteolysis, and component instability. Preoperatively, patients with infection had a significantly decreased arc of motion compared with patients without infection (79 degrees vs 92 degrees; P<.05). There was a strong trend for the infected knees to have a lower preoperative KSCS than the noninfected knees, although this trend did not achieve statistical significance (76 vs. 92; P =.11). Postoperatively, patients with infection continued to have a significantly decreased range of motion (89 degrees vs. 99 degrees; P =.05). The postoperative KSCS was markedly lower in the septic versus aseptic revisions (115 vs. 135; P =.02). Patients with infection had a significantly lower function score (44 vs. 57; P =.03). A significantly higher percentage of patients stated that they were unable to return to normal activities of daily living after septic versus aseptic revision total knee arthroplasty (24% vs. 7%; P<.05). Despite the inferior functional result, patients expressed an equal degree of satisfaction with the results of their treatment in septic versus aseptic revision cases.

The results of retaining a well-fixed patellar component in revision total knee arthroplasty

The results of revision total knee arthroplasty (TKA) in which a well-fixed patellar component was left in place (retained) were compared with those in which the patellar component was revised to a cemented all-polyethylene component. The patella was retained in 34 cases, 12 of which were metal-backed, and was revised in 39 cases. Data collected on all patients included a Knee Society clinical and radiographic score, SF36, a patellofemoral questionnaire, and a satisfaction survey. There were no differences in clinical score, responses to specific patellofemoral questions, or patient satisfaction between the 2 groups. Retaining a well-fixed patellar component at the time of revision TKA appears to be a viable option with equivalent short-term results to those obtained when the patellar component is revised.

Pain at the end of the stem after revision total knee arthroplasty

A consecutive series of patients undergoing revision total knee arthroplasty was studied prospectively. Clinical and radiographic assessment was performed preoperatively, 6 and 12 months postoperatively, and annually thereafter. Evaluation consisted of a Knee Society clinical score and assessment of patient satisfaction. In addition, patients completed drawings of their lower extremity regarding the location and severity of the pain they experienced preoperatively and at minimum 2-year followup (mean, 36 months; range, 24-48 months). Pain that was localized to the diaphyseal region of the femur or tibia on the drawing was defined as pain at the end of the stem. Clinical, radiographic, and pain drawing data were completed for patients who had 66 of 78 revision total knee arthroplasties performed during the time of the study (85%). All procedures were performed with the same implant system and instrumentation and included fluted cobalt-chrome stems for all patients in whom the stem was implanted without cement and slightly underreamed (press fit). All femoral components had the surface cemented with the stems press fit. Sixteen of the tibial stems were cemented fully, whereas the remaining 50 tibial components were cemented on the surface only with the stems press fit. Localized pain at the end of the stem was present on the femoral side in seven of 66 patients (11%) and in seven of 50 patients with press fit tibial stems (14%). Patients with pain at the end of the stem at 2 to 4 years postoperatively had significantly lower preoperative function scores and overall Knee Society clinical score. Postoperatively, patients with pain at the end of the stem had a significantly lower clinical score; however the postoperative function score and Knee Society clinical score were not significantly different than scores of patients who did not have pain at the end of the stem. There was no correlation between the stem diameter and the occurrence of pain; however, there was a trend for percent canal fill to be higher on the tibial side in patients with pain (71% versus 63%), but this was not statistically significant. Three of the 16 patients with cemented tibial stems (19%) experienced pain at the end of the stem. Patients with press fit stems who had pain at the end of the stem were more likely to express dissatisfaction with the surgical procedure than patients without pain at the end of the stem.

The Ranawat Award. Comparison of surgical approaches in total knee arthroplasty

A series of 123 revision total knee replacements performed at three centers and followed up for 2 to 4 years was evaluated. In cases in which exposure could be obtained with undue tension on the patellar tendon, the surgical approach was modified using either quadriceps turndown (14 cases) or tibial tubercle osteotomy (15 cases). The remaining 94 patients underwent a standard operative approach that consisted of a medial parapatellar capsular incision which in 31 cases was combined with a quadriceps snip. The results were compared using the Knee Society clinical score, a patient satisfaction survey, and a patellofemoral questionnaire. Postoperatively, the group of patients who had a quadriceps snip was equivalent to the group of patients who underwent a standard approach in every parameter measured, and the groups therefore were combined for comparison purposes. The patients who had quadriceps turndown and the tibial tubercle osteotomy had equivalent scores postoperatively both of which were significantly lower than the standard group. The group of patients who had quadriceps turndown had a significantly greater increase in arc of motion than the tibial tubercle osteotomy group. The tibial tubercle osteotomy group had a lower degree of extension lag but a higher percentage of patients who had difficulty with kneeling and stooping and a higher percentage of patients who had difficulty with kneeling and stooping and a higher percentage of patients who thought the surgery was unsuccessful in relieving pain and unsuccessful in returning them to normal daily activities.

Revision knee arthroplasty with patella replacement versus bony shell

A study was undertaken to assess the clinical results of revision total knee arthroplasty in which an unresurfaced bony shell was left after removing a patellar component versus those in which a patellar component was implanted. Followup was obtained in 123 of 130 consecutive revision total knee replacements (94%) from three centers. In 21 knees a shell of patellar bone was left and 92 knees had a patellar component in place. Ten patients had a patellectomy and were excluded from consideration. The group with the bony shell had a lower postoperative knee score but the preoperative Knee Society clinical score was significantly lower as well in this group of patients. Compared with the group of patients with the patellar component in place, the group of patients with knees left with a bony shell had a significantly higher percentage of patients who had difficulty using stairs, a higher percentage of patients who were not satisfied with their surgery, and a higher percentage of patients who rated their surgery as unsuccessful in returning them to normal daily activities. When a patellar component was not able to be implanted in revision total knee arthroplasty, a lower quality result was observed.

Enhanced cleavage of type II collagen by collagenases in osteoarthritic articular cartilage

We demonstrate the direct involvement of increased collagenase activity in the cleavage of type II collagen in osteoarthritic human femoral condylar cartilage by developing and using antibodies reactive to carboxy-terminal (COL2-3/4C(short)) and amino-terminal (COL2-1/4N1) neoepitopes generated by cleavage of native human type II collagen by collagenase matrix metalloproteinase (MMP)-1 (collagenase-1), MMP-8 (collagenase-2), and MMP-13 (collagenase-3). A secondary cleavage followed the initial cleavage produced by these recombinant collagenases. This generated neoepitope COL2-1/4N2. There was significantly more COL2-3/4C(short) neoepitope in osteoarthritis (OA) compared to adult nonarthritic cartilages as determined by immunoassay of cartilage extracts. A synthetic preferential inhibitor of MMP-13 significantly reduced the unstimulated release in culture of neoepitope COL2-3/4C(short) from human osteoarthritic cartilage explants. These data suggest that collagenase(s) produced by chondrocytes is (are) involved in the cleavage and denaturation of type II collagen in articular cartilage, that this is increased in OA, and that MMP-13 may play a significant role in this process.

THE FREQUENCY OF VENOUS THROMBOSIS IN CEMENTED AND NON-CEMENTED HIP ARTHROPLASTY

We randomised 250 patients undergoing unilateral, elective hip arthroplasty for osteoarthritis to receive either a cemented or a non-cemented Mallory Head prosthesis. Aspirin was used as prophylaxis against thromboembolism during the first half of the study and adjusted-dose warfarin during the second half. Postoperatively, all patients were asked to have bilateral venography and 80% agreed. All were evaluated clinically for pulmonary embolism.

There was no difference in the frequency of deep-venous thrombosis between the two groups (50% cemented v 47% non-cemented, p = 0.73; 95% CI of the difference −13.6% to 19.3%). Three of the 64 patients (5%) in whom venography had demonstrated isolated distal thrombi developed pulmonary emboli.

The frequency of venous thrombosis in cemented and non-cemented hip arthroplasty

We randomised 250 patients undergoing unilateral, elective hip arthroplasty for osteoarthritis to receive either a cemented or a non-cemented Mallory Head prosthesis. Aspirin was used as prophylaxis against thromboembolism during the first half of the study and adjusted-dose warfarin during the second half. Postoperatively, all patients were asked to have bilateral venography and 80% agreed. All were evaluated clinically for pulmonary embolism. There was no difference in the frequency of deep-venous thrombosis between the two groups (50% cemented nu 47% non-cemented, p = 0.73; 95% CI of the difference -13.6% to 19.3%). Three of the 64 patients (5%) in whom venography had demonstrated isolated distal thrombi developed pulmonary emboli.

Damage to type II collagen in aging and osteoarthritis starts at the articular surface, originates around chondrocytes, and extends into the cartilage with progressive degeneration

Enhanced denaturation of type II collagen fibrils in femoral condylar cartilage in osteoarthritis (OA) has recently been quantitated immunochemically (Hollander, A.P., T.F. Heathfield, C. Webber, Y. Iwata, R. Bourne, C. Rorabeck, and A.R. Poole. 1994. J. Clin. Invest. 93:1722-1732). Using the same antibody that only reacts with denatured type II collagen, we investigated with immunoperoxidase histochemistry (results were graded for analysis) the sites of the denaturation (loss of triple helix) of this molecule in human aging (at autopsy, n= 11) and progressively degenerate (by Mankin grade [MG]) OA (at arthroplasty, n= 51) knee condylar cartilages. Up to 41 yr, most aging cartilages (3 of 4) (MG 0-4) showed very little denaturation. In most older cartilages, (4 of 7) (MG 2-4), staining was observed in the superficial and mid zones. This pattern of collagen II denaturation was also seen in all OA specimens with increased staining extending to the deep zone with increasing MG. Collagen II staining correlated directly both with MG and collagen II denaturation measured by immunoassay. Cartilage fibrillation occurred in OA cartilages with increased penetration of the staining for collagen II denaturation into the mid and deep zones and where denaturation was more pronounced by immunoassay. Thus in both aging and OA the first damage to type II collagen occurs in the superficial and upper mid zone (low MG) extending to the lower mid and deep zones with increasing degeneration (increasing MG). Initial damage is always seen around chondrocytes implicating them in the denaturation of type II collagen.

Costs of elective total hip arthroplasty during the first year. Cemented versus noncemented

The cost-effectiveness of the Mallory Head (Biomet, Warsaw, IN) cemented versus noncemented total hip arthroplasty was determined as part of a randomized trial. Costs were assessed during the first postoperative year. In-hospital resource use was determined using a chart review of 60 randomly selected patients. Costs were determined using a fully allocated costing model. Outpatient resource use was determined using patient diaries, and appropriate costs were allocated for outpatient visits, admissions to hospital, and patient-borne costs. There was no difference in costs between the cemented and noncemented prostheses. The average cost of the initial hospitalization was $9,990 (1988 Canadian dollars), and outpatient costs during the first year were $1,137 (total cost during the first year was $11,127). The cost per quality adjusted life year was $27,139 during the first year and $8,031 during the first 3 years.

Increased damage to type II collagen in osteoarthritic articular cartilage detected by a new immunoassay

A new immunoassay was developed to detect denaturation of type II collagen in osteoarthritis (OA). A peptide, alpha 1 (II)-CB11B, located in the CB11 peptide of type II collagen, was synthesized and used to produce a monoclonal antibody (COL2-3/4m) of the IgG1 (kappa) isotype. This reacts with a defined epitope in denatured but not native type II collagen and the alpha 3 chain of type XI collagen. The latter is present in very small amounts (about 1% wt/wt) in cartilage relative to the alpha 1 (II) chain. By using an enzyme-linked immunosorbent assay, type II collagen denaturation and total type II collagen content were determined. The epitope recognized by the antibody was resistant to cleavage by alpha-chymotrypsin and proteinase K which were used to extract alpha 1 (II)-CB11B from the denatured (alpha-chymotrypsin soluble) and residual native (proteinase K soluble) collagen alpha-chains, respectively, present in human femoral articular cartilage. Type II collagen content was significantly reduced from a mean (range) of 14% (9.2-20.8%) of wet weight in 8 normal cartilages to 10.3% (7.4-15.0%) in 16 OA cartilages. This decrease, which may result in part from an increased hydration, was accompanied by an increase in the percent denaturation of type II collagen in OA to 6.0% of total type II collagen compared with 1.1% in normal tissue. The percent denaturation was ordinarily greater in the more superficial zone than in the deep zone of OA cartilage.

The effect of elective total hip replacement on health-related quality of life

The effect of total hip replacement on the health-related quality of life of patients who have osteoarthrosis was examined as part of a randomized, controlled trial comparing femoral head prostheses that were inserted with or without cement. One hundred and eighty-eight patients were followed for three months: 179 of them, for six months; 156, for one year; and ninety, for two years. The health-related quality of life was assessed with use of the Harris hip score, the Merle d'Aubigné hip score, the Sickness Impact Profile, the Western Ontario and McMaster University (WOMAC) Osteoarthritis Index, the McMaster--Toronto Arthritis (MACTAR) Patient Preference Disability Questionnaire, and the time trade-off technique as a measure of utility. Patients also took the six-minute-walk test. The mean age of the patients in the study was sixty-four years (range, forty to seventy-five years); ninety-seven patients (53 per cent) were men and ninety-four (50 per cent) had a prosthesis inserted with cement. Only three of 188 patients refused to return for quality-of-life assessments. There was significant improvement in all health-related quality-of-life measures and in the six-minute-walk test after the operation (p < 0.01 for all items, except for the work dimension of the Sickness Impact Profile at three months [p = 0.07]). Most of the improvement had occurred by three months postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Osteoarthritis in the human knee: a dynamic process of cartilage matrix degradation, synthesis and reorganization

The matrix of articular cartilage undergoes degenerative changes in osteoarthritis which involve a number of matrix molecules. The structural and mechanical integrity is organized around the composite collagen II, IX, XI fibrillar organization. The small proteoglycan decorin that binds to these fibrils may influence their structure and mechanical properties. Aggrecan interacts indirectly via hyaluronic acid and possibly directly through unknown mechanisms. When collagen is cleaved at the articular surface in early osteoarthritis, decorin and aggrecan are lost. Increases in decorin and aggrecan content occur deeper in the cartilage. This is accompanied by evidence for increased formation of collagen fibrils and increased degradation and synthesis of aggrecan and type II collagen. The net contents of these proteoglycan per tissue do not, however, change until advanced degeneration occurs. These degradative processes are likely catalyzed by metalloproteinases and cysteine proteases. Cartilage exhibits significant capacity for remodelling which may be enhanced by therapeutic management of this process.

A technology assessment study design

Randomized controlled trials of drug therapies are now required before the licensing and use of almost all medications. Other health care technologies should be similarly evaluated. The area of competing technologies requires more research, and cemented and noncemented hip prostheses have recently been identified as an important example of such a technology. Although trials such as ours require considerable care in their planning and execution, they can be conducted on a busy clinical teaching ward without adversely affecting the quality and quantity of clinical care.