Nelson F. SooHoo

Factors Predicting Complication Rates Following Total Knee Replacement

BACKGROUND The purpose of this investigation was to expand on previous studies by more fully examining the role of a variety of patient and hospital characteristics in determining adverse outcomes following total knee replacement. METHODS With use of data from all hospital admissions in California from 1991 through 2001, multiple logistic regression was performed on the information regarding patients treated with total knee replacement. Rates of mortality and readmission due to infection and pulmonary embolism during the first ninety days after discharge were regressed against a variety of independent variables, including demographic factors (age, gender, race, ethnicity, and insurance type), burden of comorbid disease (Charlson comorbidity index), and provider variables (hospital size, teaching status, and surgical volume). A separate baseline probability analysis was then performed to compare the relative importance of all predictor variables. RESULTS The sample size for this analysis was 222,684. A total of 1176 deaths (rate, 0.53%), 1586 infections (0.71%), and 914 pulmonary emboli (0.41%) occurred within the first ninety days after discharge. The average age of the patients at the time of surgery was sixty-nine years. Sixty-two percent of the patients were women, and 32% had a Charlson comorbidity index of >0. The significant predictors for complications (p < 0.05) included age, gender, race/ethnicity, Charlson comorbidity index, insurance type, and hospital volume. A baseline probability analysis was performed with the base case considered to be a white woman who was over the age of sixty-five years, had a Charlson comorbidity index of 0, had Medicare insurance, and was treated at a high-volume, non-teaching hospital. For a patient with the baseline case characteristics, the probability of death was 31/10,000, the probability of infection was 59/10,000, and the probability of pulmonary embolism was 41/10,000 in the first ninety days after discharge. Altering the base case by assuming that care was received at a low-volume hospital increased the expected mortality rate by a factor of 26%. Increasing the Charlson comorbidity index to 1 increased the mortality rate by 170%, whereas decreasing the age to younger than sixty-five years lowered the mortality rate by 73%. Hospital volume, comorbidity, and age had similar effects on the expected rates of readmission due to infection and pulmonary embolism. CONCLUSIONS The effects of age and the Charlson comorbidity index on the baseline probability of adverse outcomes following total knee replacement were shown to be similar to or greater than the effect of hospital volume. This study elucidates and compares the relative importance of the effects of several different factors on outcome. This information is important when considering the conclusions and implications of this type of policy-relevant outcomes research.

Complication rates following open reduction and internal fixation of ankle fractures.

BACKGROUND Ankle fractures are among the most common injuries treated by orthopaedic surgeons. The purpose of the present investigation was to examine the risks of complications after open reduction and internal fixation of ankle fractures in a large population-based study. METHODS With use of Californias discharge database, we identified 57,183 patients who had undergone open reduction and internal fixation of a lateral malleolar, bimalleolar, or trimalleolar ankle fracture as inpatients in the years 1995 through 2005. Short-term complications were examined on the basis of the rates of readmission within ninety days after discharge. The intermediate-term rate of reoperation for ankle fusion or arthroplasty was also analyzed. Logistic regression and proportional hazard regression models were used to determine the strength of the relationships between the rates of complications and fracture type, patient demographics and comorbidities, and hospital characteristics. RESULTS The overall rate of short-term complications was low, including the rates of pulmonary embolism (0.34%), mortality (1.07%), wound infection (1.44%), amputation (0.16%), and revision open reduction and internal fixation (0.82%). The intermediate-term rates of reoperation were also low, with ankle fusion or ankle replacement being performed in 0.96% of the patients who were observed for five years. Open fractures, age, and medical comorbidities were significant predictors of short-term complications. The presence of complicated diabetes was a particularly strong predictor (odds ratio, 2.30; p < 0.001), as was peripheral vascular disease (odds ratio, 1.65; p < 0.001). The intermediate-term rate of reoperation for ankle fusion or replacement was higher in patients with trimalleolar fractures (hazard ratio, 2.07; p < 0.001) and open fractures (hazard ratio, 5.29; p < 0.001). Treatment at a low-volume hospital was not significantly associated with either the aggregate risk of short-term complications or the risk of intermediate-term reoperation. CONCLUSIONS By analyzing a large, diverse patient population, the present study clarifies the risks associated with open reduction and internal fixation of ankle fractures. Open injury, diabetes, and peripheral vascular disease were strong risk factors predicting a complicated short-term postoperative course. Fracture type was a strong predictor of reoperation for ankle fusion or replacement. Hospital volume did not play a significant role in the rates of short-term or intermediate-term complications.

Evaluation of the validity of the AOFAS Clinical Rating Systems by correlation to the SF-36

This study evaluates the validity of the AOFAS Clinical Rating Systems by examining their level of correlation to the Medical Outcomes Study Short Form-36 (SF-36) in patients with foot and ankle complaints. The SF-36 is an extensively validated outcomes tool that has been used as a benchmark in examining the validity of outcomes instruments designed for the upper extremity, knee, shoulder, and general orthopaedic conditions. The study sample was 91 patients seen at the foot and ankle clinic of a university-based orthopaedic practice. Patients were administered both the AOFAS Clinical Rating Systems and SF-36 instruments. Pearson correlation coefficients of the AOFAS scores to the SF-36 sub-scales ranged from 0.02 to 0.36 in the overall study population. Correlation was higher for the sub-set of patients with ankle-hindfoot disorders (0.11 to 0.53) than patients with forefoot disorders (−0.05 to 0.25). The low levels of correlation seen in this study suggest poor construct validity of the AOFAS Clinical Rating Systems.

Comparison of Reoperation Rates Following Ankle Arthrodesis and Total Ankle Arthroplasty

BACKGROUND The role of ankle arthroplasty in the treatment of ankle arthritis is controversial. Ankle fusion is commonly performed, but there is ongoing concern about functional limitations and arthritis in the adjacent subtalar joint following ankle arthrodesis. The use of ankle arthroplasty as an alternative to ankle fusion is expanding, but reported results have been limited to those in case series. The purpose of this study was to compare the reoperation rates following ankle arthrodesis and ankle replacement on the basis of observational, population-based data from all inpatient admissions in California over a ten-year period. Our hypothesis was that patients treated with ankle replacement would have a lower risk of undergoing subtalar fusion but a higher overall risk of undergoing major revision surgery. METHODS We used Californias hospital discharge database to identify patients who had undergone ankle replacement or ankle arthrodesis as inpatients in the years 1995 through 2004. Short-term outcomes, including rates of major revision surgery, pulmonary embolism, amputation, and infection, were examined. Long-term outcomes that were analyzed included the rates of major revision surgery and subtalar joint fusion. Logistic and proportional hazard regression models were used to estimate the impact of the choice of ankle replacement or ankle fusion on the rates of adverse outcomes, with adjustment for patient factors including age and comorbidity. RESULTS A total of 4705 ankle fusions and 480 ankle replacements were performed during the ten-year study period. Patients who had undergone ankle replacement had an increased risk of device-related infection and of having a major revision procedure. The rates of major revision surgery after ankle replacement were 9% at one year and 23% at five years compared with 5% and 11% following ankle arthrodesis. Patients treated with ankle arthrodesis had a higher rate of subtalar fusion at five years postoperatively (2.8%) than did those treated with ankle replacement (0.7%). Regression analysis confirmed a significant increase in the risk of major revision surgery (hazard ratio, 1.93 [95% confidence interval, 1.50 to 2.49]; p < 0.001) but a decreased risk of subtalar fusion (hazard ratio, 0.28 [95% confidence interval, 0.09 to 0.87]; p = 0.03) in patients treated with ankle replacement compared with those treated with ankle fusion. CONCLUSIONS This study confirms that, compared with ankle fusion, ankle replacement is associated with a higher risk of complications but also potential advantages in terms of a decreased risk of the patient requiring subtalar joint fusion. Additional controlled trials are needed to clarify the appropriate indications for ankle arthrodesis and ankle replacement.

Responsiveness of the Foot Function Index, AOFAS Clinical Rating Systems, and SF-36 after Foot and Ankle Surgery

Background: There is uncertainty regarding which outcomes tools should be used to report the results of treatment for patients with foot and ankle disorders. This study compared the responsiveness of the Foot Function Index (FFI), American Orthopaedic Foot and Ankle Society (AOFAS) Clinical Rating Systems, and Medical Outcomes Study Short Form-36 (SF-36) in patients with foot and ankle surgery. Methods: Twenty-five patients were recruited at a tertiary referral foot and ankle practice. The mean age of the patient sample was 40 years (range 21 to 69) and 19 were women (76%). Thirteen patients (52%) had conditions affecting the ankle, hindfoot, or midfoot, while 12 patients (48%) had conditions affecting the forefoot. Patients completed packets preoperatively and 6-months postoperatively which included informed consent forms, the FFI, the AOFAS, and the SF-36 questionnaires. Standardized response means (SRM) and effect sizes (ES) were used as the measures of responsiveness and were calculated for the AOFAS scores, the three domains of the FFI, the eight SF-36 sub-scales, and the two SF-36 summary scales. Results: The standardized response mean (SRM) for the AOFAS scores was 1.10 and the effect size (ES) was 1.12. The SRM for the three FFI domains ranged from −0.39 to −0.83, while the ES ranged from −0.55 to −0.86. The SRM for the SF−36 ranged from 0.09 to 0.72 (ES ranged from 0.09 to 0.77) with the highest values occurring with the Bodily Pain sub-scale (SRM 0.72, ES 0.77) and Physical Component Summary scale (SRM 0.76, ES 0.68). Conclusions: This study demonstrated increased responsiveness of foot and ankle specific outcomes tools compared to the SF-36. However, the Bodily Pain sub-scale and Physical Component Summary scale of the SF-36 had levels of responsiveness approaching those of the FFI and AOFAS Systems after foot and ankle surgery. This suggests that the SF-36 may be used alone to monitor the outcomes in these patients without sacrificing adequate sensitivity to clinical change.

Cost-Effectiveness Analysis of Unicompartmental Knee Arthroplasty as an Alternative to Total Knee Arthroplasty for Unicompartmental Osteoarthritis

BACKGROUND The purpose of this study was to compare the cost-effectiveness of unicompartmental knee arthroplasty as an alternative to total knee arthroplasty in patients with degenerative arthritis limited to either the medial or lateral compartment. METHODS A decision model was created for the treatment of end-stage unicompartmental knee arthritis. A literature review was used to identify possible outcomes and their probabilities following treatment with either unicompartmental or total knee arthroplasty. Each outcome was weighted for quality of life with use of a utility factor, and effectiveness was expressed in units of quality-adjusted life years. Gross costs were estimated from Medicare reimbursement data for the relevant Current Procedural Terminology and Diagnosis-Related Group codes. RESULTS Sensitivity analysis demonstrated that the cost-effectiveness of unicompartmental knee arthroplasty is dependent on the assumption that its durability and functional outcomes approach those of total knee arthroplasty. Specifically, it is necessary for the survival of unicompartmental implants to be within three to four years of the assumed survival of total knee implants for unicompartmental arthroplasty to remain a cost-effective alternative. Under these assumptions, the use of unicompartmental arthroplasty is a cost-effective choice as it results in incremental gains in effectiveness at a cost of less than US dollars 50,000 (in 1998 United States dollars) per quality-adjusted life year gained. CONCLUSIONS This study supports unicompartmental knee arthroplasty as a cost-effective alternative for the treatment of unicompartmental arthritis when the durability and function of a unicompartmental replacement are assumed to be similar to those of a primary total knee replacement. This suggests that, with appropriate patient selection, the currently available literature supports unicompartmental arthroplasty as a cost-effective alternative to total knee arthroplasty. LEVEL OF EVIDENCE Economic and decision analysis, Level II.

Evaluation of the Validity of the Foot Function Index in Measuring Outcomes in Patients with Foot and Ankle Disorders

Background: There is uncertainty regarding which outcomes tools should be used to report the results of treatment for patients with foot and ankle disorders. This study evaluates the validity of the Foot Function Index (FFI) by examining its level of correlation to the Medical Outcomes Study Short Form-36 (SF-36). The SF-36 is an extensively validated outcomes tool that has been used as a benchmark in examining the validity of several orthopaedic outcomes tools. Methods: Seventy-three patients were recruited at a tertiary referral foot and ankle practice. Patients completed packets which included informed consent forms, the FFI, and the SF-36 questionnaires. The questionnaires were scored and Pearson correlation coefficients were determined between the three domains of the FFI and the eight SF-36 sub-scales, as well as the two SF-36 summary scales. Results: Sixty-nine patients completed an adequate number of items to be included in the study. The mean age of the patient sample was 46 (range 16 to 82) years and 44 were women (64%). Twenty-one patients (30%) had conditions affecting the forefoot, while 48 patients (70%) had conditions affecting the ankle or hindfoot. All three FFI domains had moderate to high levels of correlation to many of the SF-36 scales. The Disability domain of the FFI had the most consistent level of correlation to the SF-36 with Pearson coefficients in the range of −0.23 to −0.69. The Activity Limitation (r = −0.28 to −0.64) and Pain domains (r = −0.10 to −0.61) also demonstrated moderate levels of correlation to several of the SF-36 scales. Conclusions: The consistently moderate to high levels of correlation of the FFI to the SF-36 seen in this study support the FFI as a valid measure of health status. This suggests that the FFI is a reasonable method to monitor patient outcomes. Future studies should focus on determining if the FFI improves responsiveness to clinical change when used in combination with generic instruments like the SF-36.

Reliability of the Foot Function Index: A Report of the AOFAS Outcomes Committee

Background: There currently is no widely used, validated, self-administered instrument for measuring musculoskeletal functional status in individuals with nonsystemic foot disorders. The purpose of this paper was to report on the assessment of reliability of one of these instruments. We wanted to determine if the Foot Function Index (FFI), which has been validated in rheumatoid patients without fixed foot deformity or prior foot surgery, would be reliable for a population of patients with foot complaints without systemic disease. Methods: Patients were recruited from five orthopaedic offices where the physicians were members of the American Orthopaedic Foot and Ankle Society. Patients were asked to complete the FFI at the time of their initial office visit and then were givena second copy to complete and return by mail 1 week after their visit. Results: Ninety-six patients completed the first questionnaire, and 54 patients completed the second. Reliability in this population was acceptable with an average of 23.5% of the patients providing retest values within one point of the initial response and an average of 45.3% of the patients providing the same response, for a total of 68.8% of all respondents answering within one point between their initial and second questionnaire. In two of the three categories, there were frequent nonresponses or no applicable responses. Four questions, two in the pain section and two in the activity limitation section, generated 20% or more of the nonapplicable answers. Conclusions: The FFI appears to be a reasonable tool for low functioning individuals with foot disorders. It may not be appropriate for individuals who function at or above the level of independent activities of daily living.

Factors predicting complication rates after primary shoulder arthroplasty.

HYPOTHESIS Shoulder arthroplasty is an effective treatment for arthritic conditions and intraarticular fractures of the proximal humerus. Treatment options include total and hemiarthroplasty of the shoulder. They hypothesis of this study was that a mandatory statewide discharge database could identify the epidemiology of primary shoulder arthroplasty, 90 day complication rates, implant survival rates, and patient and hospital characteristics associated with complications. MATERIALS AND METHODS We identified patients undergoing primary total shoulder replacement and hemiarthroplasty between 1995 and 2005. We report rates of complications within 90 days of surgery and performed survival analysis using revision surgery as the endpoint. Logistic and proportional hazard regression models were used to estimate the effect of patient and provider factors in predicting the rates of adverse outcomes. RESULTS During the study period, 15,288 patients underwent shoulder arthroplasty. Patients undergoing total shoulder arthroplasty and hemiarthroplasty had no statistically significant difference in the aggregate risk of 90-day complications or the risk of implant failure within the study period. Fracture patients were shown to have a higher risk of short-term complications (odds ratio, 3.2; P < .001). Implant failure rates were lower in patients with fracture, rheumatoid arthritis, increased comorbidity, and advanced age. CONCLUSION This study reports similar rates of short-term complications and implant failure in patients undergoing total or hemiarthroplasty, an overall mortality rate of 1.3%, and a pulmonary embolism rate of 0.6%. The findings of our study indicate that the risk of short-term complications is highest in patients undergoing total or hemiarthroplasty for a fracture compared with nonfracture indications. Our results also indicate that longer-term, implant survival is largely driven by factors associated with increased activity, such as age. In patients undergoing surgery for arthritis of the shoulder, we found no difference in implant survival rates between total and hemiarthroplasty of the shoulder.

Which Factors Influence Preservation of the Osteonecrotic Femoral Head

BackgroundAlthough surgeons use many procedures to preserve the femoral head in patients with hip osteonecrosis, there is no consensus regarding the best procedure.Questions/purposesWe raised the following questions: (1) Is one surgical treatment preferred based on published data? (2) What are the rates of radiographic progression or conversion to THA after treatment of pre- and postcollapse hips? (3) Does lesion size in the femoral head influence progression? And (4) does the extent of involvement of the weightbearing surface of the femoral head influence outcome?MethodsWe searched MEDLINE and Scopus for articles published between 1998 and 2010. We included only articles assessing an operative intervention for hip osteonecrosis and having a level of evidence of I to IV. We included 54 of the 488 reviewed manuscripts.ResultsNo procedure was superior to others. In pre- and postcollapse hips, 264 of 864 hips (31%) and 419 of 850 hips (49%), respectively, exhibited radiographic disease progression. There were lower failure rates when the lesion involved less than 15% of the femoral head or had a necrotic angle of less than 200° (14%–25%) and when the osteonecrotic lesion involved only the medial 1/3 of the weightbearing surface (4.6%).ConclusionsThe best treatment of precollapse lesions is difficult to determine due to the limitations of the available literature. However, the data suggest operative intervention prevents collapse of small lesions of the femoral head or when there is a limited amount of the weightbearing surface involved. Patients with head collapse have a high progression rate after a femoral head-saving procedure.