In-hospital mortality of surgical patients: is there an empiric basis for standard setting?

Several public and private groups have set minimum procedure-specific volume standards. Such standards reflect concerns about hospital quality and cost. In-hospital mortality rates are often taken as one measure of quality. To learn about variations in in-hospital mortality rates, we analyzed data on patients who underwent any of seven surgical procedures from a national cohort of 521 hospitals observed continuously between 1972 and 1981. On the average, mortality rates fell as the number of procedures performed annually at the hospital rose. Volumes at which mortality rates reached minimum levels were far higher than actual volumes achieved by the vast majority of hospitals. However, knowledge of hospital volumes left the major part of variation among hospitals' procedure-specific mortality rates unexplained. Many hospitals with low volumes of certain procedures had no associated deaths. Hospitals experienced appreciable year-to-year variation in mortality even though mortality rates fell with the number of years the procedure was performed at the hospital. Correlations among mortality rates for the procedures were low, suggesting that variation in rates is procedure rather than hospital specific. State rate-setting programs had no effect on mortality rates associated with the procedures analyzed. For several reasons, we conclude that an adequate statistical basis for setting minimum volume standards does not presently exist.

Complications, comorbidities, and mortality: improving classification and prediction.

OBJECTIVE: First, to compare the distribution of complications and comorbidities associated with 17 common surgical procedures. We then describe the effect of augmenting an ICD-9-CM version of the Charlson comorbidity index, given the possible confounding of comorbidities and complications, for three common inpatient surgical procedures: coronary artery bypass surgery, pacemaker surgery, and hip fracture repair. DATA SOURCES AND STUDY SETTING: Individuals having one of the above procedures between April 1, 1990 and March 31, 1994, identified from Manitoba Health hospital discharge data, and their extracted records. STUDY DESIGN: Design was cross-sectional and longitudinal using Manitoba data on hospital utilization and mortality. DATA COLLECTION/EXTRACTION: Manitoba hospital discharge abstracts permit identifying whether or not the diagnosis represents an in-hospital complication of care. Two data sets were created for each procedure, one including complication diagnoses and another with complications removed. PRINCIPAL FINDINGS: The degree to which complications contaminated estimation of comorbidity depended both on the procedures studied and on the covariates selected. The unique structure of the algorithm for the Charlson comorbidity index led to complication diagnoses having only a minor effect on the comorbidity score generated. Unless a data set affords the opportunity to remove complication diagnoses, the improvement in comorbidity detection afforded by augmenting the Charlson index, combined with the potential for overestimation of comorbidity, seem sufficiently modest to contraindicate such augmentation.

Assessment of HCFA's 1992 Medicare hospital information report of mortality following admission for hip arthroplasty.

OBJECTIVE: The Health Care Financing Administration (HCFA) produced annually from 1987 through 1994 mortality data information as part of the Medicare Hospital Information Project (MHIP) report. We assessed the validity of these data for hip arthroplasty for one state Medicare population and we analyzed the accuracy of the predictions derived from the Bailey-Makeham mortality model for this procedure. DATA SOURCES AND STUDY SETTING: The study sample consisted of claims and model data from 1,421 Medicare patients who underwent hip arthroplasty at acute care Arkansas hospitals from October 1990 through September 1991. STUDY DESIGN: Patients were stratified into two groups based on reason for surgery (fracture status): reconstruction or fracture management. Patient survival experience was compared between the two groups. The effect of fracture status on the HCFA model's predictive ability was examined empirically and via a simulation study. RESULTS: Our results indicate that hip arthroplasty patients are not uniform with regard to outcome, depending on the reason for the surgery. Patients with fracture had a much higher 30-day mortality rate than those who underwent reconstruction (p < .001). The empirical data and the simulation study suggest that the Bailey-Makeham model underestimates mortality for reconstructive surgery in fracture patients, providing a false benchmark for those institutions that perform hip arthroplasty on predominantly one category of patients. CONCLUSION: Published HCFA data concerning mortality for hip arthroplasty combines two different patient populations into one statistic. Casual examination of these data could result in a false benchmark for analysis of institutional performance. An important implication from this study for policymakers who base decisions on "report cards" or performance measurement reports is that, although they are necessary,generic case-mix, comorbidity, and severity of illness adjustments may not be sufficient to achieve accurate representations of outcomes, and that more disease/procedure--specific adjustments may be needed to avoid inappropriate conclusions.

The validity of survivorship analysis in total joint arthroplasty.

The use of survivorship analysis requires an assumption that patients who are lost to follow-up are no more or less likely to be at risk of failure of an operation or a procedure than are patients who are still being followed. This is a major assumption in long-term orthopaedic studies, in which a high percentage of patients are usually lost to follow-up. We compared the survivorship curve for the first 100 Tharies replacements done at our institution (which were completed by September 1977), using data that were collected in the standard way up to 1985, through a letter requesting a follow-up visit, with the curve for the same patients that was based on almost complete follow-up data that were gathered by telephone from 1985 on. The similarity of the two curves suggested that the assumptions that are necessary for the validity of survivorship analysis are reasonable, even in the orthopaedic setting, in which many patients are lost to follow-up. The usefulness of the survivorship curve for prediction was also evaluated by comparing the curve based on the first forty-six of the 100 Tharies replacements (before 1977) with the curve based on the last fifty-four such operations (from January 1977 to September 1977). The results of these two comparisons suggest that survivorship analysis is a valid technique to use in the long-term evaluation of patients who have had a joint replacement.

Hip arthroplasty in hemophilic arthropathy.

As hemophilic arthropathy infrequently affects the hip joint, we performed a multicenter retrospective study to determine the results of hip arthroplasty in hemophilic patients. Thirty-four hip arthroplasties were performed in twenty-seven male patients at four major hemophilia centers from October 1972 through September 1990. Twenty-six patients had classic hemophilia and one had factor-IX deficiency. The mean age of the patients at the time of the operation was thirty-eight years (range, fifteen to seventy-three years). The mean duration of follow-up was eight years, with a minimum of two years for all patients who were still alive at the time of this review. Four patients were seropositive for the human immunodeficiency virus at the time of the operation, and sixteen patients were seropositive at the time of the most recent follow-up examination. Nine patients (33 per cent) died before the time of this review; seven had been seropositive for the human immunodeficiency virus. There were twenty-six total hip arthroplasties performed with cement, six total hip arthroplasties performed without cement, one total hip arthroplasty in which the femoral component was inserted with cement and the acetabular component was inserted without it (so-called hybrid arthroplasty), and one bipolar arthroplasty performed with cement. There were no early infections after these thirty-four primary arthroplasties. There were three late infections around prostheses inserted with cement, and all led to a resection arthroplasty. Six (21 per cent) of the twenty-eight cemented femoral components and six (23 per cent) of the twenty-six cemented acetabular components were revised because of aseptic loosening.(ABSTRACT TRUNCATED AT 250 WORDS)

Geographic variations in the rates of elective total hip and knee arthroplasties among Medicare beneficiaries in the United States.

We analyzed the variations in the rates of elective total hip and total knee arthroplasties for 1988 in the United States to determine whether the rates correlated with the numbers of surgeons. There were 56,204 total hip arthroplasties and 68,491 total knee arthroplasties, performed in the home states of the patients among all of the Medicare beneficiaries. Medicare beneficiaries include most people who are more than sixty-five years old in the United States and a small proportion of younger people who are eligible for Medicare for other reasons. Seventy-nine per cent of the patients who had had a total hip arthroplasty and 89 per cent of those who had had a total knee arthroplasty had been managed with the operation because of osteoarthrosis. Both operations were most common in the seventy to seventy-four-year age-group. We calculated the rate of operations per 100 beneficiaries for each state and age-adjusted the results. Across all of the states, bilateral procedures constituted 1.6 per cent of the total hip arthroplasties and 4.8 per cent of the total knee arthroplasties. The in-hospital rates of mortality were 0.72 per cent for total hip arthroplasties and 0.45 per cent for total knee arthroplasties. The destinations after discharge from the hospital were similar for the two groups of patients, with more than 65 per cent of the patients being discharged directly to their homes. There were no significant differences among states in terms of the length of stay in the hospital or reimbursement of the hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Outcomes after displaced fractures of the femoral neck. A meta-analysis of one hundred and six published reports.

Methods of meta-analysis, a technique for the combination of data from multiple sources, were applied to analyze 106 reports of the treatment of displaced fractures of the femoral neck. Two years or less after primary internal fixation of a displaced fracture of the femoral neck, a non-union had developed in 33 per cent of the patients and avascular necrosis, in 16 per cent. The rate of performance of a second operation within two years ranged from 20 to 36 per cent after internal fixation and from 6 to 18 per cent after hemiarthroplasty (relative risk, 2.6; 95 per cent confidence interval, 1.4 to 4.6). Conversion to an arthroplasty was the most common reoperation after internal fixation and accounted for about two-thirds of these procedures. The remaining one-third of the reoperations were for removal of the implant or revision of the internal fixation. For the patients who had had a hemiarthroplasty, the most common reoperations were conversion to a total hip replacement, removal or revision of the prosthesis, and débridement of the wound. Although we observed an increase in the rate of mortality at thirty days after primary hemiarthroplasty compared with that after primary internal fixation, the difference was not significant (p = 0.22) and did not persist beyond three months. The absolute difference in perioperative mortality between the two groups was small. An anterior operative approach for arthroplasty consistently was associated with a lower rate of mortality at two months than was a posterior approach. Some reports showed promising results after total hip replacement for displaced fractures of the femoral neck; however, randomized clinical trials are still needed to establish the value of this treatment.

The results of revision of total hip arthroplasty.

The results of 140 total hip revision procedures for "non-septic" loosening, dislocation, and fracture of the femoral stem or shaft have been personally reviewed and rated by the Harris method. The minimum follow-up period was six months: thirty-three (24 per cent) showed excellent or good results, seventy-two (51 per cent) showed fair or poor results. Subsequent excision arthroplasty was performed in thirty-one patients. The infection rate for these revision procedures was very high, suggesting that many were already infected at the time of revision, and that every "loose" hip must be assumed to be infected until proved otherwise. The mortality rate of 3 per cent was surprisingly low after more than one major surgical procedure in these elderly patients.

Evaluation of new technologies for total hip replacement. Economic modelling and clinical trials.

Cost is a factor in the choice of prosthetic components in joint replacement. For a given performance, the least expensive components are the most cost-effective. When evaluating a new prosthesis with an unknown outcome, the use of an economic model allows estimation of potential cost-effectiveness. We used published data for the survival of cemented total hip replacements from Sweden, and cost and demographic information from New South Wales, Australia, in such a model. In young active total hip recipients a new prosthetic design which offered a 90% improvement in survivorship over 15 years and a 15% reduction in the cost of revision surgery, could be sold at a price of 2 to 2.5 times that of conventional cemented components such as the Charnley Low Friction Arthroplasty and still be cost-effective. Using more likely estimates of the improved performance of new technology, however, the upper limit of cost-effectiveness is an increase of 1.5 to 1. Only a very small increase in the cost of a prosthesis could ever be justified for older patients of either sex. Most of the potential benefits of a better level of survivorship appear towards the end of the 15-year period. The results of modelling may be incorporated in clinical trial design. Given the known performance of some well-established and relatively inexpensive designs of prostheses, very large randomised studies would be required to prove an improvement in performance.

Internal fixation versus hemiarthroplasty for the displaced subcapital fracture of the femur. A prospective randomised study.

A prospective randomised trial of surgical treatment for the displaced subcapital femoral fracture in patients of 70 years or more is presented. Two hundred and eighteen patients were randomly allocated into one of three treatment groups: manipulative reduction and internal fixation using Garden screws; Thompson hemiarthroplasty through a posterior (Moore) approach; and Thompson hemiarthroplasty through an anterolateral (McKee) approach. There is no significant difference in the mortality of the internal fixation and posterior arthroplasty groups. Both groups showed a significantly higher mortality than patients operated on through the anterior approach. The technical results of operation were worse in the internally fixed group, with only 40 per cent being satisfactory. Mobilisation was best achieved after the posterior approach. It is concluded that Thompson hemiarthroplasty, using an anterolateral approach, is the safest operation in this group of patients.

Alumina-on-alumina hip replacement. Results and survivorship in young patients.

Total hip replacement using an alumina head and socket and a titanium alloy stem is evaluated in a series of patients under 50 years of age. Between April 1977 and December 1986, 86 such replacements were performed in 75 patients, but mainly because patients had difficulty travelling from Africa, only 71 hips were followed up adequately; of these, 56 were primary procedures and 15 revisions. Survivorship analysis showed that 98% of the prostheses were retained for 10 years. On clinical and radiological examination 51 of the 71 hips were stable and acceptable, 15 had radiological changes on the acetabular side, and one on the femoral side; four other cases had clinical and radiological changes suggesting impending failure, possibly because fixation of the socket was inadequate. There were no differences between the results of the primary procedures and those of revisions. In these young patients, the results seem better with alumina-on-alumina hips than with other varieties, possibly because of their remarkably low wear.

Loss to follow-up matters.

Survival analysis of joint replacement relies on the assumption that surgical procedures in patients lost to follow-up have the same chance of failing as those in patients who continue to be assessed. Our study questions that assumption. During the 16-year follow-up of 2268 patients who had received total hip replacements 142 (6%) were lost to follow-up. The cumulative loss at 15 years was 20%. At their last assessment, patients who subsequently failed to attend for follow-up had significantly worse pain, range of movement and opinion of their progress (p < 0.001) and significantly worse radiological features than a matched control group (p < 0.01). Patients lost to follow-up have a worse outcome than those who continue to be assessed. Consequently, a survival analysis that does not take into account such patients is likely to give falsely optimistic results. It is therefore essential that vigorous attempts are made to minimise loss to follow-up, and that the rate of such loss is quoted. The overall loss to follow-up disguises the magnitude of the problem, which is best quantified by a cumulative rate of follow-up. The reliability of a study can be assessed by a loss-to-follow-up quotient, calculated by the number of failures: the lower the quotient the more reliable the data. Ideally, the quotient should be less than 1.

Total hip replacement in renal transplant patients.

Of 1197 renal transplant recipients on the Oxford Transplant Programme, 25 (2%) needed arthroplasties for painful osteonecrosis of the hip. Nine of them had bilateral operations, giving a total of 34 primary total hip replacements (THR). The mean time from onset of symptoms to THR was 2.4 years and from transplantation to THR 5.1 years. The mean follow-up was 5.1 (1 to 14) years. THR relieved the pain in all the patients, but survival analysis indicated a lower survival rate than is usual for primary THR. There were eight major complications. One graft-related problem, early acute tubular necrosis, resolved rapidly after immediate treatment. One patient developed deep infection at 3.5 years after THR which settled with conservative treatment. Five hips developed aseptic loosening requiring revision arthroplasty at a mean of 8.8 years' follow-up. One patient had a non-fatal pulmonary embolism. THR is the treatment of choice for patients with painful osteonecrosis of the hip after renal transplant, but has higher rates of both early and late complications. Surgery should be performed in close association with a renal transplant unit.

Unipolar or bipolar prosthesis for displaced intracapsular hip fracture in octogenarians: a randomised prospective study.

We performed a randomised prospective trial to compare a cemented unipolar prosthesis (Thompson) with a cemented bipolar prosthesis (Monk) in the treatment of displaced intracapsular fractures of the hip in patients over 80 years of age. Patients with a mental test score of less than 5/13 were excluded but the mortality was still about 30% at one year in both groups. We therefore feel that subjective criteria such as the level of pain and the return to the preinjury state are of paramount importance. Two years after operation there was no statistical difference between the rate of complications in the two groups. After adjusting for confounding factors such as differences in the level of function before injury between the groups, the degree of return to the preinjury state was significantly greater (p = 0.04) when using the unipolar prosthesis, which is one-quarter of the price of the bipolar. We cannot therefore justify the use of an expensive bipolar prosthesis in patients over 80 years of age.

The long-term results of the Howse total hip arthroplasty. With particular reference to those requiring revision.

We present the results of 506 consecutive Howse hip arthroplasties with a minimum follow-up of 10 years. The mortality within one month of surgery was 0.79%. The early dislocation rate was 1.38%, two hips requiring revision. Nine hips developed deep sepsis (1.78%), eight of which required revision. At 10 years 42 hips (8.3%) had required revision, including 14 with aseptic acetabular loosening and 11 with femoral stem fractures. We feel that as judged by the dislocation rate and the need for subsequent revision, the Howse arthroplasty is an acceptable form of total hip replacement, particularly in the older patient and in those requiring total replacement for femoral neck fractures.

Stanmore total hip replacement in younger patients: review of a group of patients under 50 years of age at operation.

Fifty-seven Stanmore Total Hip replacements were implanted between 1974 and 1986 in patients under the age of 50 years. We have reviewed the results in terms of survivorship and function, and assessed the reasons for revision. Of the original 57, 22 (39%) have been revised at an average of 12 years from implantation, usually for aseptic loosening. Most of them had originally been implanted for osteoarthritis. Prostheses cemented with second-generation techniques have lasted significantly longer, and acetabular loosening emerged as a continuing problem. The overall survivorship was 90% at 10 years and 68% at 15 years. Cemented hip replacement appears to be a viable option in younger patients and the Stanmore implant is comparable with other cemented prostheses in this age group.

Cementless versus cemented total hip arthroplasty. A scientific controversy?

The controversy surrounding cementless versus cemented total hip arthroplasty cannot be resolved at this stage on a strictly scientific basis. Various aspects of this controversy are presented. The focus of some specific discussion sections include acrylic cement, component design of both the socket and the stem, and function and wear.

The rationale for cemented total hip arthroplasty.

Long-term follow-up of early Charnley cemented THAs demonstrates excellent survival (Table 1). New techniques in cementing have improved the quality of the femoral cement fixation and have shown consistently good performance at 10-year follow-up. Noncemented designs have not yet demonstrated similar long-term results. Recent reports reveal osteolysis in noncemented prostheses, which is observed earlier than in cemented designs. This implies a greater role for polyethylene debris in the etiology of osteolysis. Polyethylene debris is produced not only at the articulation but also at the nonarticular metal-polyethylene interface in modular metal-backed acetabular components. This results in the production of additional plastic debris. Metal backing has not demonstrated any clinical improvement in the long-term performance of cemented acetabular components. Furthermore, it may be detrimental due to decreased polyethylene thickness, increased stress within the polyethylene, and an increased rate of polyethylene wear of both the articular and nonarticular surfaces. Multiple reports have demonstrated that titanium alloy is not an acceptable articulating surface because it has a poor resistance to abrasion. It can result in severe metallosis in the periarticular tissues, leading to progressive osteolysis and early failure of the arthroplasty. Caution is suggested in the widespread application of polymodular femoral components because the production of metallic debris may prove excessive. Cemented THA remains the gold standard by which other methods of fixation must be assessed. The enviable long-term results with early cementing techniques and the Charnley prosthesis will be difficult to match, even with developing technology.

A temporary antibiotic-loaded joint replacement system for management of complex infections involving the hip.

Management of the infected hip replacement associated with substantial loss of bone, especially segmental loss of the proximal femur, is a challenging problem. In this report, the authors outline the development of an immediate-fit, custom-made, antibiotic-selective replacement system for the hip and proximal femur, to help maintain limb length, joint stability, and mobility of the patient. Despite the initial relatively crude design, it was a valuable adjunct in the management of 15 consecutive cases. A more sophisticated and versatile system has since been developed for use in straightforward and complex cases.

Bipolar hemiarthroplasty for fracture of the femoral neck.

Controversy in the treatment of displaced femoral neck fractures in the elderly focuses on the use of fixation versus the use of a prosthesis. Beginning in 1980, at The New York Hospital-Cornell Medical Center, it became routine to treat elderly patients for displaced fractures with bipolar hemiarthroplasty. This retrospective study evaluates the morbidity, mortality, and clinical and social functioning of 246 consecutive patients treated with bipolar hemiarthroplasty for Garden III and Garden IV nonpathological fractures. Follow-up ranged from 1 to 6 years. Of the 246 patients with 247 femoral neck fractures, 201 were female and 45 were male; the average age was 78 years. Fourteen patients (5.7%) died during the postoperative hospitalization. Thirty-one patients (13.3%) died within the first year following surgery. Mortality was related to the number of preexisting medical conditions: patients with four or more preexisting conditions had a significantly higher mortality than others (p less than 0.001: chi 2). The overall wound infection rate was 3.2%. There were only two failures (0.9%), both for deep infection, requiring Girdlestone debridement. One patient was revised for infection with successful reimplantation. There were two postoperative dislocations (0.9%), both reduced closed. Only one bipolar (0.4%) required conversion to a total hip replacement for a fractured acetabulum, none for arthritic wear. No radiographic evidence of significant acetabular erosion or protrusion nor femoral component loosening was noted. Clinical results were evaluated using the Hospital for Special Surgery Hip Rating Scale.(ABSTRACT TRUNCATED AT 250 WORDS)