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Centers of excellence and bundled payment models have driven perioperative optimization and surgical site infection (SSI) prevention with decolonization protocols and antibiotic prophylaxis strategies. We sought to evaluate time trends in the incidence of deep SSI and its causative organisms after six orthopaedic procedures in a US-based integrated healthcare system.We conducted a population-level time-trend study using data from Kaiser Permanente's orthopaedic registries. All patients who underwent primary anterior cruciate ligament reconstruction (ACLR), total knee arthroplasty (TKA), elective total hip arthroplasty (THA), hip fracture repair, shoulder arthroplasty, and spine surgery were identified (2009 to 2020). The annual incidence of 90-day deep SSI was identified according to the National Healthcare Safety Network/Centers for Disease Control and Prevention guidelines with manual chart validation for identified infections. Poisson regression was used to evaluate annual trends in SSI incidence with surgical year as the exposure of interest. Annual trends in overall incidence and organism-specific incidence were considered.The final study sample was composed of 465,797 primary orthopaedic procedures. Over the 12-year study period, a decreasing trend in deep SSI was observed for ACLR and hip fracture repair. Although there was variation in incidence rates for specific operative years for TKA, elective THA, shoulder arthroplasty, and spine surgery, no consistent decreasing trends over time were found. Decreasing rates of Staphylococcus aureus infections over time after hip fracture repair, shoulder arthroplasty, and spine surgery and decreasing trends in antibiotic resistance after elective THA and spine surgery were also observed. Increasing trends of polymicrobial infections were observed after TKA and Cutibacterium acnes after elective THA.The overall incidence of deep SSI after six orthopaedic procedures was rare. Decreasing SSI rates were observed for ACLR and hip fracture repair within our US-based healthcare system. Polymicrobial infections after TKA and Cutibacterium acnes after elective THA warrant closer surveillance.IV.

Background The efficacy of commercially available antibiotic-loaded bone cement (ABC) in preventing infection in total knee arthroplasty (TKA) is unclear. We sought to determine the effectiveness of commercially available ABC in reducing the risk of infection following TKA, both overall and among 3 subgroups of patients with a higher risk of infection (diabetes, body mass index ≥35 kg/m, and American Society of Anesthesiologists classification ≥3), and to evaluate the association between the use of ABC and the risks of aseptic revision and revision for aseptic loosening. Methods The Kaiser Permanente Total Joint Replacement Registry was utilized to evaluate 87,018 primary cemented TKAs performed from 2008 to 2016. The primary outcome was time to infection (90-day deep infection or septic revision). Reduced infection risk with ABC relative to regular cement was tested with use of propensity-score-weighted Cox proportional-hazards models with superiority and noninferiority testing. All analyses were replicated for each of the 3 high-risk subgroups. For the secondary revision outcomes, propensity-score-weighted Cox proportional-hazards models were utilized. Results Regular cement was found to be noninferior to ABC with respect to risk infection (hazard ratio [HR], 1.14; 95% confidence interval [CI], 0.93 to 1.40) and cost across all TKA patients. However, a lower risk of infection was observed with ABC among TKA patients with diabetes (HR, 0.72; 95% CI, 0.52 to 0.99). There was no evidence of a difference in risk of revision for ABC compared with regular cement. Conclusions We found that the additional cost associated with the use of commercially prepared ABC in primary TKA was not justified in all patients; however, the risk of reduction was lower among patients with diabetes who received ABC. Further study is warranted to identify the efficacy of ABC among other high-risk populations. Level of evidence Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

BACKGROUND Prior studies have documented racial and ethnic disparities in total hip arthroplasty (THA) outcomes in the U.S. The purpose of this study was to assess whether racial/ethnic disparities in THA outcomes persist in a universally insured population of patients enrolled in an integrated health-care system. METHODS A U.S. health-care system total joint replacement registry was used to identify patients who underwent elective primary THA between 2001 and 2016. Data on patient demographics, surgical procedures, implant characteristics, and outcomes were obtained from the registry. The outcomes analyzed were lifetime revision (all-cause, aseptic, and septic) and 90-day postoperative events (infection, venous thromboembolism, emergency department [ED] visits, readmission, and mortality). Racial/ethnic differences in outcomes were analyzed with use of multiple regression with adjustment for socioeconomic status and other potential confounders. RESULTS Of 72,755 patients in the study, 79.1% were white, 8.2% were black, 8.5% were Hispanic, and 4.2% were Asian. Compared with white patients, lifetime all-cause revision was lower for black (adjusted hazard ratio [HR], 0.79; 95% confidence interval [CI], 0.66 to 0.94; p = 0.007), Hispanic (adjusted HR, 0.73; 95% CI, 0.61 to 0.87; p = 0.002), and Asian (adjusted HR, 0.49; 95% CI, 0.37 to 0.66; p < 0.001) patients. Ninety-day ED visits were more common among black (adjusted odds ratio [OR], 1.15; 95% CI, 1.05 to 1.25; p = 0.002) and Hispanic patients (adjusted OR, 1.18; 95% CI, 1.08 to 1.28; p < 0.001). For all other postoperative events, minority patients had similar or lower rates compared with white patients. CONCLUSIONS In contrast to prior research, we found that minority patients enrolled in a managed health-care system had rates of lifetime reoperation and 90-day postoperative events that were generally similar to or lower than those of white patients, findings that may be related to the equal access and/or standardized protocols associated with treatment in the managed care system. However, black and Hispanic patients still had higher rates of 90-day ED visits. Further research is required to determine the reasons for this finding and to identify interventions that could reduce unnecessary ED visits. LEVEL OF EVIDENCE Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

BACKGROUND Prior studies have identified diabetes and disease severity (defined using hemoglobin A1c [HbA1c]) as potential risk factors for complications after shoulder arthroplasty. Evaluations of diabetes status and risk of adverse outcomes beyond the 30-day window either are limited or have not accounted for disease severity. Further, measures of diabetes severity other than HbA1c have yet to be investigated in a shoulder arthroplasty population. QUESTIONS/PURPOSES (1) Are diabetes status and glycemic control associated with adverse events, including deep infection, all-cause revision, and 90-day readmission after shoulder arthroplasty? (2) Is postoperative HbA1c associated with revision risk? (3) Is there a threshold of preoperative HbA1c that best identifies patients with diabetes who are at higher risk of 3-year deep infection, 1-year all-cause revision, or 90-day readmission? (4) Can the Adapted Diabetes Complications Severity index (aDCSI) be used as an alternative measure of diabetes severity in evaluating the risk of deep infection, all-cause revision, and 90-day readmission and identification of patients with diabetes at higher risk for these events? (5) Is there a difference between elective and traumatic shoulder arthroplasty patients? METHODS We conducted a retrospective registry-based cohort study using Kaiser Permanente's Shoulder Arthroplasty Registry (2005-2015). Primary shoulder arthroplasties were classified as patients with and without diabetes. Patients with diabetes were further evaluated using two disease severity measures (1) HbA1c, with good glycemic control classified as preoperative HbA1c < 7.0% and poor control defined as HbA1c ≥ 7.0%; and (2) aDCSI, classified as mild (score of 0-2) or severe (score ≥ 3) diabetes. Cox regression was used to evaluate the risk of deep infection and revision according to diabetes status and disease severity; conditional logistic regression was used for 90-day readmission. Time-dependent 1-year postoperative HbA1c was used to evaluate revision risk in Cox regression. All models were adjusted for covariates and stratified by elective versus trauma shoulder arthroplasty. Receiver operating characteristic curves were generated for HbA1c and aDCSI to determine whether a threshold exists to identify patients at higher risk of deep infection, all-cause revision, or 90-day readmission. The study sample consisted of 8819 patients; 7353 underwent elective shoulder arthroplasty and 1466 underwent shoulder arthroplasty due to trauma. For elective shoulder arthroplasty, 1430 patients (19%) had diabetes, and among the patients who underwent arthroplasty due to trauma, 444 (30%) had diabetes. RESULTS Patients with diabetes who underwent elective shoulder arthroplasty and had poor glycemic control had a higher likelihood of 90-day readmission compared with patients without diabetes (OR, 1.5; 95% CI, 1.0-2.1; p = 0.032). No association was found for patients with diabetes who underwent shoulder arthroplasty due to trauma. No association was found between postoperative HbA1c and revision risk. Receiver operating characteristic curve analysis suggested preoperative HbA1c performed poorly at differentiating adverse events. When using aDCSI, patients with severe diabetes who underwent both elective and traumatic shoulder arthroplasty had a higher likelihood of 90-day readmission compared with patients without diabetes (OR, 1.6; 95% CI, 1.2-2.2; p = 0.001 and OR, 1.8; 95% CI, 1.2-2.7; p = 0.005, respectively). Similar to HbA1c, the aDCSI was a poor classifier in differentiating adverse events. CONCLUSIONS Of the longer-term outcomes evaluated, more-severe diabetes was only found to be associated with an increase in 90-day readmissions after shoulder arthroplasty; a stronger association was found when using the aDCSI in identifying diabetes severity. Arbitrary cutoffs in HbA1c may not be the best method for determining risk of postoperative outcomes. Future work investigating perioperative diabetes management should work to identify and validate measures, such as the aDCSI, that better identify patients at higher risk for postoperative outcomes and, more importantly, whether outcomes can be improved by modifying these measures with targeted interventions. LEVEL OF EVIDENCE Level III, therapeutic study.

Prior studies have documented racial and ethnic disparities in hip fracture treatment and outcome, and unequal access is commonly cited as a potential mediator. We sought to assess whether disparities in hip fracture outcome persist within a universally insured population of patients enrolled in a managed health-care system.A U.S. integrated health systems registry was used to identify patients who underwent treatment for a hip fracture when they were ≥60 years of age from 2009 to 2014. Patient demographics, procedure details, and outcomes were obtained from the registry. Differences in outcome according to race/ethnicity were analyzed using multivariable regression analysis with adjustment for socioeconomic status and other potential confounders.Of 17,790 patients, 79.4% were white, 3.9% were black, 9.4% were Hispanic, and 7.4% were Asian. Compared with white patients, black patients had a similar 1-year mortality rate (odds ratio [OR] = 0.93, 95% confidence interval [CI] = 0.79 to 1.09, p = 0.37), Hispanic patients had a lower rate (OR = 0.85, 95% = CI = 0.75 to 0.96, p = 0.01), and Asian patients also had a lower rate (OR = 0.65, 95% CI = 0.56 to 0.76, p0.001). There were no differences in terms of surgical delay, 90-day emergency department visits, or reoperations during the patient's lifetime (p0.05) between the groups. Compared with white patients, black and Hispanic patients had fewer 90-day postoperative complications (p = 0.04 and p = 0.01, respectively); 90-day unplanned readmissions were less common among Asian patients (p = 0.03) but more common among black patients (p = 0.01).In this study of hip fractures treated in an integrated managed care system, minority patients were found to have postoperative mortality rates that were similar to, or lower than, those of white patients. These findings may be related to the equal access and/or standardized protocols associated with treatment in this managed care system.Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background Prior studies have examined the relationship between surgeon and hospital volumes and outcome following hip fracture surgical procedures, but the results have been inconclusive. The purpose of this study was to assess the hip fracture volume-outcome relationship by analyzing data from a large, managed care registry. Methods The Kaiser Permanente Hip Fracture Registry prospectively records information on surgically treated hip fractures within the managed health-care system. Using this registry, all surgically treated hip fractures in patients 60 years of age or older were identified. Surgeon and hospital volume were defined as the number of hip fracture surgical procedures performed in the preceding 12 months and were divided into tertiles (low, medium, and high). The primary outcome was mortality at 1 year postoperatively. Secondary outcomes were mortality at 30 and 90 days postoperatively as well as reoperation (lifetime), medical complications (90-day), and unplanned readmission (30-day). To determine the relationship between volume and these outcome measures, multivariate logistic and Cox proportional hazards regression were performed, controlling for potentially confounding variables. Results Of 14,294 patients in the study sample, the majority were female (71%) and white (79%), and the mean age was 81 years. The overall mortality rate was 6% at 30 days, 11% at 90 days, and 21% at 1 year. We did not find an association between surgeon or hospital volume and mortality at 30 days, 90 days, or 1 year (p > 0.05). There was also no association between surgeon or hospital volume and reoperation, medical complications, or unplanned readmission (p > 0.05). Conclusions In this analysis of hip fractures treated in a large integrated health-care system, the observed rates of mortality, reoperation, medical complications, and unplanned readmission did not differ by surgeon or hospital volume. In contrast to other orthopaedic procedures, such as total joint arthroplasty, our data do not suggest that hip fractures need to be preferentially directed toward high-volume surgeons or hospitals for treatment. Level of evidence Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Lack of consensus continues regarding the benefit of anteriorly based surgical approaches for primary total hip arthroplasty (THA). The purpose of this study was to evaluate the risk of aseptic revision, septic revision, and dislocations for various approaches used in primary THAs from a community-based healthcare organization.(1) What is the incidence of aseptic revision, septic revision, and dislocation for primary THA in a large community-based healthcare organization? (2) Does the risk of aseptic revision, septic revision, and dislocation vary by THA surgical approach?The Kaiser Permanente Total Joint Replacement Registry was used to identify primary THAs performed between April 1, 2001 and December 31, 2011. Endpoints were septic revisions, aseptic revisions, and dislocations. The exposure of interest was surgical approach (posterior, anterolateral, direct lateral, direct anterior). Patient, implant, surgeon, and hospital factors were evaluated as possible confounders. Survival analysis was performed with marginal multivariate Cox models. Hazard ratios (HRs) and 95% confidence intervals (CIs) are reported. A total of 42,438 primary THAs were available for analysis of revision outcomes and 22,237 for dislocation. Median followup was 3 years (interquartile range, 1-5 years). The registry's voluntary participation is 95%. The most commonly used approach was posterior (75%, N = 31,747) followed by anterolateral (10%, N = 4226), direct anterior (4%, N = 1851), and direct lateral (2%, N = 667).During the study period 785 hips (2%) were revised for aseptic reasons, 213 (0.5%) for septic reasons, and 276 (1%) experienced a dislocation. The revision rate per 100 years of observation was 0.54 for aseptic revisions, 0.15 for septic revisions, and 0.58 for dislocations. There were no differences in adjusted risk of revision (either septic or aseptic) across the different THA approaches. However, the anterolateral approach (adjusted HR, 0.29; 95% CI, 0.13-0.63, p = 0.002) and direct anterior approach (adjusted HR, 0.44; 95% CI, 0.22-0.87, p = 0.017) had a lower risk of dislocation relative to the posterior approach. There were no differences in any of the outcomes when comparing the direct anterior approach with the anterolateral approach.Anterior and anterolateral surgical approaches had the advantage of a lower risk of dislocation without increasing the risk of early revision.Level III, therapeutic study.

BackgroundAlthough total hip arthroplasty (THA) is a successful procedure, 4% to 11% of patients who undergo THA are readmitted to the hospital. Prior studies have reported rates and risk factors of THA readmission but have been limited to single-center samples, administrative claims data, or Medicare patients. As a result, hospital readmission risk factors for a large proportion of patients undergoing THA are not fully understood.Questions/purposes(1) What is the incidence of hospital readmissions after primary THA and the reasons for readmission? (2) What are the risk factors for hospital readmissions in a large, integrated healthcare system using current perioperative care protocols?MethodsThe Kaiser Permanente (KP) Total Joint Replacement Registry (TJRR) was used to identify all patients with primary unilateral THAs registered between January 1, 2009, and December 31, 2011. The KPTJRR's voluntary participation is 95%. A logistic regression model was used to study the relationship of risk factors (including patient, clinical, and system-related) and the likelihood of 30-day readmission. Readmissions were identified using electronic health and claims records to capture readmissions within and outside the system. Odds ratio (OR) and 95% confidence intervals (CIs) were calculated. Of the 12,030 patients undergoing primary THAs included in the study, 59% (n = 7093) were women and average patient age was 66.5 years (± 10.7).ResultsThere were 436 (3.6%) patients with hospital readmissions within 30 days of the index procedure. The most common reasons for readmission were infection and inflammatory reaction resulting from internal joint prosthetic (International Classification of Diseases, 9(th) Revision, Clinical Modification [ICD-9-CM] 996.66, 7.0%); other postoperative infection (ICD-9-CM 998:59, 5.5%); unspecified septicemia (ICD-9-CM 038.9, 4.9%); and dislocation of a prosthetic joint (ICD-9-CM 996.42, 4.7%). In adjusted models, the following factors were associated with an increased likelihood of 30-day readmission: medical complications (OR, 2.80; 95% CI, 1.59-4.93); discharge to facilities other than home (OR, 1.89; 95% CI, 1.39-2.58); length of stay of 5 or more days (OR, 1.80; 95% CI, 1.22-2.65) versus 3 days; morbid obesity (OR, 1.74; 95% CI, 1.25-2.43); surgeries performed by high-volume surgeons compared with medium volume (OR, 1.53; 95% CI, 1.14-2.08); procedures at lower-volume (OR, 1.41; 95% CI, 1.07-1.85) and medium-volume hospitals (OR, 1.81; 95% CI, 1.20-2.72) compared with high-volume ones; sex (men: OR, 1.51; 95% CI, 1.18-1.92); obesity (OR, 1.32; 95% CI, 1.02-1.72); race (black: OR, 1.26; 95% CI, 1.02-1.57); increasing age (OR, 1.03; 95% CI, 1.01-1.04); and certain comorbidities (pulmonary circulation disease, chronic pulmonary disease, hypothyroidism, and psychoses).ConclusionsThe 30-day hospital readmission rate after primary THA was 3.6%. Modifiable factors, including obesity, comorbidities, medical complications, and system-related factors (hospital), have the potential to be addressed by improving the health of patients before this elective procedure, patient and family education and planning, and with the development of high-volume centers of excellence. Nonmodifiable factors such as age, sex, and race can be used to establish patient and family expectations regarding risk of readmission after THA. Contrary to other studies and the finding of increased hospital volume associated with lower risk of readmission, higher volume surgeons had a higher risk of patient readmission, which may be attributable to the referral patterns in our organization.Level of evidenceLevel III, therapeutic study.

Study design A retrospective review of instrumented spine registry from an integrated US healthcare system. Objective Investigate the 30-day readmission rate and risk factors after instrumented spine surgery. Summary of background data Published readmission rates range from 2% to over 20%. We were interested in learning which patients were at greatest risk, when did readmissions occur, and why. Method 30-day readmission rates were determined for 14,939 patients after an index spine procedure between 1/2009 and 3/2013. Data were analyzed with descriptive statistics, univariate, and multivariate logistic regression analysis. Result The average age of the cohort was 59 (SD = 13.4) and 52% were female. The 30-day readmission rate was 5.5% (821/14,939). The temporal pattern for readmission was: 17% (140) at week 1, 48% (394) at week 2, 72% (591) at week 3, and 100% (821) at week 4. The leading causes were wound complications (infection, hematoma, dehiscence, seroma), sepsis, pain management, pneumonia, and pulmonary emboli/deep venous thrombosis. In a multivariate model, readmission risk factors were: malignancy (OR 2.99, 95% CI: 1.56, 5.73), operative time more than 400 minutes (OR 2.59, 95% CI: 1.66, 4.02), operative time 300-399 minutes (OR 2.33, 95% CI: 1.54-3.52), hospital stay 6-10 days (OR 2.03, 95% CI: 1.31-3.14), hospital stay more than 10 days (OR 1.85, 95% CI: 1.1, -3.08), surgical complications (OR 1.67, 95% CI: 1.18, 2.36), operative time 200-299 (OR 1.52, 95% CI: 1.04, 2.22), depression (OR 1.48, 95% CI: 1.14, 1.93), rheumatoid arthritis (OR 1.45, 95% CI: 1.05, 2.01), deficiency anemia (OR 1.30, 95% CI: 1.05, 1.61), and hypothyroidism (OR 1.29, 95% CI: 1.01, 1.64). Conclusion Surgical complications (dural tear, deep infections, superficial infections, epidural hematoma), malignancy, lengthy operative times, and lengthy initial hospitalizations are all risk factors for 30-day readmission. These findings should be considered during preoperative assessment and surgical planning. Level of evidence 3.

Background: The survivorship of implants after revision total hip arthroplasty and risk factors associated with re-revision are not well defined. We evaluated the re-revision rate with use of the institutional total joint replacement registry. The purpose of this study was to determine patient, implant, and surgeon factors associated with re-revision total hip arthroplasty. Methods: A retrospective cohort study was conducted. The total joint replacement registry was used to identify patients who had undergone revision total hip arthroplasty for aseptic reasons from April 1, 2001, to December 31, 2010. The end point of interest was re-revision total hip arthroplasty. Risk factors evaluated for re-revision total hip arthroplasty included: patient risk factors (age, sex, body mass index, race, and general health status), implant risk factors (fixation type, bearing surface, femoral head size, and component replacement), and surgeon risk factors (volume and experience). A multivariable Cox proportional hazards model was used. Results: Six hundred and twenty-nine revision total hip arthroplasties with sixty-three (10%) re-revisions were evaluated. The mean cohort age (and standard deviation) was 57.0 ± 12.4 years, the mean body mass index (and standard deviation) was 29.5 ± 6.1 kg/m2, and most of the patients were women (64.5%) and white (81.9%) and had an American Society of Anesthesiologists score of

Although studies have reported lower radiological wear in highly crosslinked polyethylene (HXLPE) versus conventional polyethylene in total hip arthroplasty (THA), there is limited clinical evidence on the risk of revision of these polyethylene THA bearing surfaces.We asked: (1) Do primary THAs with a metal-on-conventional polyethylene bearing surface have a higher risk of revision (all-cause or aseptic) than metal-on-HXLPE? (2) Is the risk of revision (all-cause or aseptic) higher for conventional polyethylene versus HXLPE when the effect of femoral and acetabular components is controlled for in prosthesis-specific analyses?The Kaiser Permanente's Total Joint Replacement Registry was used to identify metal-on-conventional polyethylene and metal-on-HXLPE primary THAs (N = 26,823) performed between April 2001 and December 2011. The registry has 95% voluntary participation and 8% were lost to followup during the 10-year study period. Endpoints of interest were all-cause and aseptic revisions. Descriptive statistics and marginal Cox regression models with propensity score adjustments were applied to compare risk of revision for metal-on-conventional polyethylene versus metal-on-HXLPE THAs and to evaluate two specific manufacturers' hip implant designs while controlling for femoral and acetabular components. Of the 26,823 THAs included in the study, 1815 (7%) were metal-on-conventional polyethylene and 25,008 (93%) were metal-on-HXLPE.At 7 years followup, the cumulative incidence of revision was 5.4% (95% confidence interval [CI], 4.4%-6.7%) for metal-on-conventional and 2.8% (95% CI, 2.6%-3.2%) for metal-on-HXLPE. There was a higher adjusted risk of all-cause (hazard ratio [HR], 1.75; 95% CI, 1.37-2.24; p0.001) and aseptic (HR, 1.91; 95% CI, 1.46-2.50; p0.001) revisions among metal-on-conventional polyethylene bearing surface hips compared with metal-on-HXLPE. Results were similar within manufacturer hip designs with the same femoral and acetabular components. Conclusions Metal-on-conventional polyethylene THA bearing surfaces have a higher risk of revision compared with metal-on-HXLPE bearing surfaces. Clinicians should consider the use of HXLPE when using a polyethylene bearing in THA.Level II, cohort study.

HXLPE (highly cross-linked polyethylene) has greater wear resistance compared with UHMWPE (ultra-high molecular weight polyethylene), which may contribute to improving the outcomes of total hip arthroplasty with a large femoral head. However, no information is available regarding the effect of femoral head size on the survivorship of HXLPE hip prostheses. The aim of the present study was to provide evidence regarding whether femoral head size has an effect on the risk of revision when an HXLPE liner is used on a metal head.A distributed health data network was developed by the ICOR (International Consortium of Orthopaedic Registries). Six national and regional registries are participating in this network: Kaiser Permanente, HealthEast, the Emilia-Romagna region in Italy, the Catalan region in Spain, Norway, and Australia. Data from each registry were standardized and provided at an aggregate level for each of the variables of interest. Patients with osteoarthritis who were forty-five to sixty-four years of age and had undergone uncemented total hip arthroplasty were included in the present study. Analyses were performed on the basis of individual patient profiles, utilizing the variables collected from each registry. The outcome of interest was the time to the first revision (for any reason). Survival probabilities and their standard errors were extracted from each registry for each unique combination of the covariates and were combined through multivariate meta-analysis utilizing linear mixed models to compare survivorship for32-mm, 32-mm, and32-mm femoral head sizes.A total of 14,372 total hip arthroplasties were included in the study. The five-year rate of revision surgery varied from 1.9% to 3.2% among registries. The risk of revision did not differ significantly between32-mm and 32-mm head sizes (HR [hazard ratio] = 0.91, 95% CI [confidence interval] = 0.69 to 1.19) or between32-mm and 32-mm sizes (HR = 1.05, 95% CI = 0.70 to 1.55).The results of our study provide relevant data to orthopaedic surgeons deciding on the use of a larger articulation in a metal-on-polyethylene bearing. A larger head diameter should not be considered a detriment to device survival when an HXLPE liner is used. However, efforts to force the use of a large-size implant appear unsupported, as similar survivorship was observed for all head diameter groups.

Nearly every American will be exposed to a medical device during his or her life, and tens of millions of people will be treated with an implantable device. However, regulatory and public health systems in the United States and internationally have critical gaps. The U.S. Food and Drug Administration (FDA) has released a national medical device postmarket surveillance plan1, in which the agency identifies as a main priority the goal of promoting the development of national and international medical device registries for selected products. Another top priority of the FDA is the creation of a unique device identification (UDI) system for medical devices in response to a 2007 federal law2.

Background: The rapid decline in use of conventional total hip replacement with a large femoral head size and a metal-on-metal bearing surface might lead to increased popularity of ceramic-on-ceramic bearings as another hard-on-hard alternative that allows implantation of a larger head. We sought to address comparative effectiveness of ceramic-on-ceramic and metal-on-HXLPE (highly cross-linked polyethylene) implants by utilizing the distributed health data network of the ICOR (International Consortium of Orthopaedic Registries), an unprecedented collaboration of national and regional registries and the U.S. FDA (Food and Drug Administration). Methods: A distributed health data network was developed by the ICOR and used in this study. The data from each registry are standardized and provided at a level of aggregation most suitable for the detailed analysis of interest. The data are combined across registries for comprehensive assessments. The ICOR coordinating center and study steering committee defined the inclusion criteria for this study as total hip arthroplasty performed without cement from 2001 to 2010 in patients forty-five to sixty-four years of age with osteoarthritis. Six national and regional registries (Kaiser Permanente and HealthEast in the U.S., Emilia-Romagna region in Italy, Catalan region in Spain, Norway, and Australia) participated in this study. Multivariate meta-analysis was performed with use of linear mixed models, with survival probability as the unit of analysis. We present the results of the fixed-effects model and include the results of the random-effects model in an appendix. SAS version 9.2 was used for all analyses. We first compared femoral head sizes of >28 mm and ≤28 mm within ceramic-on-ceramic implants and then compared ceramic-on-ceramic with metal-on-HXLPE. Results: A total of 34,985 patients were included; 52% were female. We found a lower risk of revision associated with use of ceramic-on-ceramic implants when a larger head size was used (HR [hazard ratio] = 0.73, 95% CI [confidence interval] = 0.60 to 0.88, p = 0.001). Use of smaller-head-size ceramic-on-ceramic bearings was associated with a higher risk of failure compared with metal-on-HXLPE bearings (HR = 1.36, 95% CI = 1.09 to 1.68, p = 0.006). Use of large-head-size ceramic-on-ceramic bearings was associated with a small protective effect relative to metal-on-HXLPE bearings (not subdivided by head size) in years zero to two, but this difference dissipated over the longer term. Conclusions: Our multinational study based on a harmonized, distributed network showed that use of ceramic-on-ceramic implants with a smaller head size in total hip arthroplasty without cement was associated with a higher risk of revision compared with metal-on-HXLPE and >28-mm ceramic-on-ceramic implants. These findings warrant careful reflection by regulatory and clinical communities and wide dissemination to patients for informed decision-making regarding such surgery.

The International Consortium for Orthopaedic Registries is a multinational initiative established by the United States Food and Drug Administration to develop a health data network aimed at providing a robust infrastructure to facilitate evidence-based decision-making on performance of medical devices. Through the International Consortium for Orthopaedic Registries, individual data holders have complete control of their data and can choose to participate in studies of their choice. In this article, we present an overview of the data extraction process and the analytic strategy employed to answer several device performance-related questions in total hip arthroplasty and total knee arthroplasty. In the process, we discuss some nuances pertinent to International Consortium for Orthopaedic Registries data that pose certain statistical challenges, and we briefly suggest strategies to be adopted to address them.

Background: Mobile-bearing total knee prostheses were designed to reduce wear and improve implant survivorship following total knee arthroplasty. However, the benefit of mobile-bearing total knee arthroplasty remains unproven. Both mobile-bearing and fixed-bearing total knee arthroplasty implants are available in posterior-stabilized and non-posteriorstabilized designs. With the latter, the implant does not recreate the function of the posterior cruciate ligament (PCL) with a posterior-stabilizing cam mechanism. The purpose of the present study was to compare mobile-bearing, non-posteriorstabilized devices with fixed-bearing, non-posterior-stabilized devices used in total knee arthroplasty through a novel multinational study design. Methods: Through the use of a distributed health data network, primary total knee arthroplasties performed for osteoarthritis from 2001 to 2010 were identified from six national and regional total joint arthroplasty registries. Multivariate meta-analysis was performed with use of linear mixed models, with the primary outcome of interest being revision for any reason. Survival probabilities and their standard errors were extracted from each registry for each unique combination of the covariates. Results: A total of 319,616 patients (60% female) underwent non-posterior-stabilized total knee arthroplasty. A fixedbearing, non-posterior-stabilized design was used in 258,190 (81%) of the knees and a mobile-bearing, non-posteriorstabilized design in 61,426 (19%) of the knees. Sixty-nine percent of the patients who received a fixed-bearing implant were over sixty-five years of age, compared with 63% of those who received a mobile-bearing implant. Mobile-bearing designs had a higher risk of revision, with a hazard ratio of 1.43 (95% confidence interval, 1.36 to 1.51; p < 0.001). Conclusions: Previous comparisons of mobile-bearing and fixed-bearing total knee arthroplasty outcomes have been inconclusive. The current study utilized an advanced, harmonized distributed analysis of six national and regional jointreplacement registries. To our knowledge, it is the largest analysis of mobile-bearing total knee arthroplasty to date. Mobile-bearing, non-posterior-stabilized designs presented a greater risk of failure than was found for fixed-bearing, nonposterior-stabilized designs. Caution should be used in the selection of the mobile-bearing non-posterior-stabilized design for total knee replacement.

Background: Differences in survivorship of non-posterior-stabilized compared with posterior-stabilized knee designs carry substantial economic consequences, especially with limited health-care resources. However, these comparisons have often been made between relatively small groups of patients, often with short-term follow-up, with only small differences demonstrated between the groups. The goal of this study is to compare the outcomes of non-posterior-stabilized and posterior-stabilized total knee arthroplasties with use of a unique collaboration of multiple established knee arthroplasty registries. Methods: A distributed health data network was developed by the International Consortium of Orthopaedic Registries and was used in this study to reduce barriers to participation (such as security, propriety, legal, and privacy issues) compared with a centralized data warehouse approach. The study included only replacements in osteoarthritis patients who underwent total knee procedures involving fixed-bearing devices from 2001 to 2010. The outcome of interest was time to first revision. Results: On average, not resurfacing showed a more harmful effect than resurfacing did when posterior-stabilized and non-posterior-stabilized knee replacements were compared, while the risk of revision for posterior-stabilized compared with non-posterior-stabilized knees was highest in year zero to one, followed by year one to two, years eight through ten, and years two through eight. Posterior-stabilized knees did significantly worse than non-posterior-stabilized knees did when the patella was not resurfaced. This difference was most pronounced in the first two years (year zero to one: hazard ratio [HR] = 2.15, 95% confidence interval [CI] = 1.56 to 2.95, p < 0.001; year one to two: HR = 1.61, 95% CI = 1.48 to 1.75, p < 0.001). When the patella was resurfaced, posterior-stabilized knees did significantly worse than non-posterior-stabilized knees did. This was again most pronounced in the first two years (year zero to one: HR = 1.75, 95% CI = 1.27 to 2.42, p = 0.001; year one to two: HR = 1.31, 95% CI = 1.19 to 1.45, p < 0.001). There was a reduced risk of revision with a patient age of more than sixty-five years (HR = 0.57, 95% CI = 0.55 to 0.60, p < 0.001). Conclusions: We found that fixed non-posterior-stabilized total knee arthroplasty performed better with or without patellar resurfacing than did fixed posterior-stabilized total knee arthroplasty. This effect was most pronounced in the first two years. The risk of revision for posterior-stabilized total knee arthroplasties was reduced with patellar resurfacing. Also, a patient age of more than sixty-five years and female gender reduced the risk of revision.

The regulation of medical devices has attracted controversy recently because of problems related to metal-on-metal hip implants. There is growing evidence that metal-on-metal implants fail early and cause local and systemic complications. However, the failure associated with metal-on-metal head size is not consistently documented and needs to be communicated to patients and surgeons. The purpose of this study is to compare implant survival of metal on metal with that of metal on highly cross-linked polyethylene.Using a distributed health data network, primary total hip arthroplasties were identified from six national and regional total joint arthroplasty registries (2001 to 2010). Inclusion criteria were patient age of forty-five to sixty-four years, cementless total hip arthroplasties, primary osteoarthritis diagnosis, and exclusion of the well-known outlier implant ASR (articular surface replacement). The primary outcome was revision for any reason. A meta-analysis of survival probabilities was performed with use of a fixed-effects model. Metal-on-metal implants with a large head size of36 mm were compared with metal-on-highly cross-linked polyethylene implants.Metal-on-metal implants with a large head size of36 mm were used in 5172 hips and metal-on-highly cross-linked polyethylene implants were used in 14,372 hips. Metal-on-metal total hip replacements with a large head size of36 mm had an increased risk of revision compared with metal-on-highly cross-linked polyethylene total hip replacements with more than two years of follow-up, with no difference during the first two years after implantation. The results of the hazard ratios (and 95% confidence intervals) from the multivariable model at various durations of follow-up were 0.95 (0.74 to 1.23) at zero to two years (p = 0.698), 1.42 (1.16 to 1.75) at more than two years to four years (p = 0.001), 1.78 (1.45 to 2.19) at more than four years to six years (p0.001), and 2.15 (1.63 to 2.83) at more than six years to seven years (p0.001).We conducted a comparison of large-head-size, metal-on-metal implants and metal-on-highly cross-linked polyethylene implants in younger patients with uncemented fixation. We found consistent and strong evidence worldwide that large-head-size, metal-on-metal implants were associated with increased risk of revision after two years compared with metal-on-highly cross-linked polyethylene implants, with the effect becoming more pronounced over time.

BACKGROUND The United States Food and Drug Administration (FDA) has proposed creating a unique device identification (UDI) system for medical devices to facilitate postmarket surveillance, quality improvement, and other applications. Although a small number of health care institutions have implemented initiatives comparable with the proposed UDI system by capturing data in electronic health record (EHR) systems, it is unknown whether institutions with fewer resources will be able to similarly implement UDI. OBJECTIVE AND METHODS This paper calls attention to organizational, workflow, and technological challenges in UDI system implementation by drawing from the literature on EHR and clinical research systems implementation. FINDINGS Organizational challenges for UDI system implementation include coordinating multiple stakeholders to define UDI attributes and characteristics for use in EHRs, guiding organizational change within individual institutions for integrating UDI with EHRs, and guiding organizational change for reusing UDI data captured in EHRs. Workflow challenges include capturing UDI data in EHRs using keyboard entry and barcode scanning. Technological challenges involve interfacing UDI data between EHRs and surgical information systems, transforming UDI and related patient data from EHRs for research, and applying data standards to UDI within and beyond EHRs. DISCUSSION AND CONCLUSIONS We provide recommendations for regulations, organizational sharing, and professional society engagement to raise awareness of and overcome UDI system implementation challenges. Implementation of the UDI system will require integration of people, process, and technology to achieve benefits envisioned by FDA, including improved postmarket device surveillance and quality of care.

Background: The reported revision rates for cemented unicompartmental knee arthroplasties have varied widely. The effect of implant selection, patient characteristics, and surgeon characteristics on revision risk has not been evaluated fully. The purpose of the present study was to determine the impact of these variables on the risk for aseptic revision arthroplasty. Methods: We identified all cemented primary unicompartmental knee arthroplasties performed in our health-care system from 2002 to 2009 (median follow-up time = 2.6 years) to assess the risk for aseptic revision. A multivariate marginal Cox proportional-hazards model with robust standard errors (to adjust for the nesting of surgical cases within surgeons) was used to calculate the differential risk for revision of implants after adjusting for surgeon and hospital volume of unicompartmental knee arthroplasties performed; surgeon experience with unicompartmental knee arthroplasties at the time of surgery; surgeon fellowship training; and patient age, sex, weight, body mass index, and American Society of Anesthesiologists (ASA) score. Results: A total of 1746 unicompartmental knee arthroplasties were identified. The overall revision rate during the study period was 4.98% (95% confidence interval [CI], 4.0% to 6.1%). In a multivariate Cox model, the hazard ratio (HR) for aseptic revision relative to a modern, fixed, metal-backed tibial bearing was significantly higher for an all-polyethylene tibial tray (HR = 3.85, 95% CI = 1.54 to 9.63, p = 0.004) but not significantly higher for a mobile-bearing implant (HR = 2.42, 95% CI = 0.55 to 10.65, p = 0.242) or an older-design, fixed, metal-backed bearing (HR = 1.89, 95% CI = 0.67 to 5.33, p = 0.23). Younger age was associated with increased risk (age less than fifty-five years compared with more than sixty-five years: HR = 4.83, 95% CI = 2.60 to 8.96, p < 0.001), and a higher ASA score (≥3 compared with

Accurate prosthesis classification is critical for total joint arthroplasty surveillance and assessment of comparative effectiveness. Historically, prosthesis classification was based solely on the names of the prosthesis manufacturers. As a result, prosthesis designs changed without corresponding name changes, and other prostheses' names changed over time without substantial design modifications. As the number of prostheses used in total joint arthroplasty on the market increased, catalog and lot numbers associated with prosthesis descriptions were introduced by manufacturers. Currently, these catalog and lot numbers are not standardized, and there is no consensus on categorization of these numbers into brands or subbrands. Classification of the attributes of a prosthesis also varies, limiting comparisons of prostheses across studies and reports. The development of a universal prosthesis classification system would standardize prosthesis classification and enhance total joint arthroplasty research collaboration worldwide. This is a current area of focus for the International Consortium of Orthopaedic Registries (ICOR). National joint arthroplasty registries play a critical role in the detection of total joint arthroplasty revision rates, identification of patients during recalls and advisories, and comparative effectiveness research. In order to monitor and evaluate total joint arthroplasty procedures, the specific prostheses associated with the procedure must be accurately identified and classified. This is necessary to determine and report the outcome of those prostheses either alone or in combination with other prostheses and also to determine outcomes relevant to specific attributes and characteristics of the prostheses. In order to organize and store information specific to each prosthesis, registries have developed databases of prostheses reported to the registry. These have usually been developed in an ad hoc way by each registry, and there has been no standardized way of creating these databases. At the recent International Consortium of Orthopaedic Registries (ICOR) meeting, it was determined that developing a standardized approach would enable the development of a universal prosthesis database that all registries could use, which would not only ensure consistency of reporting between registries but also enhance inter-registry collaboration. Refereed/Peer-reviewed

Background: Some surgeons believe that they can identify patients who are at high risk for shoulder redislocation and that these patients are best served by immediate surgical stabilization. This natural history study was performed to examine the validity of this concept and to determine whether it is possible to predict the need for future surgery at the time of the index injury and examination. Methods: One hundred and thirty-one patients were followed for an average of four years after their first shoulder dislocation. An extensive history was recorded and a thorough physical examination was performed on each patient. Final evaluation consisted of a physical examination, radiographic evaluation, and determination of three outcome measurements. Results: Twenty-nine (22%) of the 131 patients requested surgery during the follow-up period. There were twenty Bankart repairs and nine rotator cuff repairs. Forty-three patients (33%) had at least one recurrent dislocation. Thirty-nine of these patients were in the group of ninety patients under the age of forty years. Thirty-seven of these thirty-nine patients either participated in contact or collision sports or used the arm at or above chest level in their occupation. Eighteen (49%) of these thirty-seven patients had surgery. Only two of the more sedentary patients had redislocation, and none had surgery. Four (10%) of the forty-one patients over the age of forty had a redislocation, but none required a Bankart repair. However, eight (20%) of the forty-one patients required a rotator cuff repair. Eighty-eight (67%) of the 131 patients never had a redislocation. Their outcome scores were high and equivalent to those of the cohort of patients who had had a successful Bankart repair of an unstable shoulder. Patients who had redislocation but chose to cope with the instability rather than have surgery had lower outcome scores. Twenty-two (51%) of the forty-three patients who had recurrent instability had only one redislocation during the entire follow-up period, whereas some patients had as many as twelve complete redislocations. Conclusions: Younger patients involved in contact or collision sports or who require overhead occupational use of the arm are more likely to have a redislocation of the shoulder than are their less active peers or older persons. However, even in the highest-risk groups, only approximately half of patients with shoulder redislocation requested surgery within the follow-up period. Early surgery based on the presumption of future dislocations, unhappiness, and disability cannot be justified. Level of Evidence: Prognostic Level I. See Instructions to Authors for a complete description of levels of evidence.

Dislocation rates after total hip arthroplasty in a community setting have not been well documented. We used a community based joint registry to evaluate hip dislocations that occurred within 1 year after total hip arthroplasty. We evaluated patient, implant, and technical factors associated with dislocation, including primary versus revision surgery, femoral head size (28 mm versus ≥ 32 mm), operative time, surgeon volume, surgical approach, age, gender, diagnosis, American Society of Anesthesiologists (ASA) classification, and body mass index (BMI). There were 1693 primary total hip arthroplasties and 277 revision procedures performed from 2001-2003. The overall dislocation rate was 1.7% for primary total hip arthroplasties and 5.1% for revision procedures. Patients with ASA scores of 3 or 4 had a 2.3-fold dislocation increase compared with patients with scores of 1 or 2. Patients with rheumatoid arthritis had an increased risk of dislocation. The dislocation rates for primary total hip arthroplasty were 2% for 28 mm heads and 0.7% for heads ≥ 32 mm. The surgeon's patient volume, surgical approach, operative time, and body mass index had no effect on dislocation. Level of Evidence: Prognostic study, level III. See Guidelines for Authors for a complete description of levels of evidence.

Background: Variation in readmission rates, length of stay, and operative time associated with rotator cuff surgery should be understood if cost-control strategies are to be considered. We hypothesized that there would be variation in resource utilization as measured in terms of these factors and that surgeon and hospital practice patterns, rather than patient characteristics, would explain this variation. Methods: We conducted a retrospective analysis of the effects of surgeon, hospital, and patient-related factors on the readmission rates, length of stay, and operative time associated with 1077 rotator cuff repairs performed by thirty-two surgeons in eleven group-model health maintenance organization hospitals, two satellite centers, and one contract facility in southern California. Results: The initial unadjusted analysis of covariance showed moderate-to-strong associations between surgeon and hospital variation and the rate of hospital readmission within thirty days (p = 0.0919 and p = 0.0209, respectively), extended length of stay (p = 0.0016 and p = 0.0016, respectively), and operative time (p < 0.0001 and p < 0.0001, respectively). The hospital effect was no longer significant when patient-related factors (i.e., sociodemographic characteristics and comorbidities) and the surgeon effect were taken into account. The surgeon effect was still significant (except with regard to the readmission rate) after adjustment for patient and hospital-related factors, explaining 23% of the variation in length of stay and 69% of the variation in operative time. There was a significantly increased risk of an extended stay (p = 0.0010) and readmission (p = 0.0260) following procedures performed at hospitals with an orthopaedic residency program. Increased operative time was significantly associated with decreased surgeon volume (p < 0.0001) and the absence of an orthopaedic residency program (p < 0.0001). Conclusions: Variation in length of stay and operative tim associated with rotator cuff surgery is largely explained by surgeon practice patterns. Our results suggest that surgeons have the ability to affect these two factors, which are often identified as drivers of cost. Level of Evidence: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

The conventional wisdom that a mobile-bearing design may offer a benefit compared with a fixed-bearing design in total knee arthroplasty has not been supported by evidence. We reviewed the published literature and annual registry reports of all national and regional registries to determine the differences in clinical outcomes between mobile and fixed-bearing designs. We found only single-center reports and studies with small sample sizes in the published literature. These studies did not demonstrate any advantages of mobile bearings over fixed bearings. Moreover, major national joint registries reported higher failure rates associated with mobile-bearing total knee replacement compared with fixed-bearing total knee replacement. Similar findings from a U.S. national study in a community setting suggest that mobile-bearing knees have an increased risk of revision. After harmonization of methodologies, international collaborations of registries may provide the best insight into the performance of mobile-bearing total knee arthroplasty in real-world settings. Mobile-bearing total knee arthroplasty implants were developed to decrease wear and improve function. The original mobile-bearing implant, the Low Contact Stress (LCS) manufactured by DePuy (Warsaw, Indiana), was available in both meniscal-bearing and rotating-platform designs. Higher rates of complications—namely, dislocations of the bearings—were observed with the meniscal-bearing design, resulting in the rotating-platform version being most commonly used. The main feature of this rotating-platform implant is allowance of unrestricted rotational motion around a central pivot. Not only does this maximize congruity, it has the potential to minimize tibial malrotation. Following expiration of the original patent, multiple implant manufacturing companies developed their own version of mobile-bearing knees. In addition to rotation around a pivot post, some designs offer anterior-posterior translation in addition to rotation. Reduction of polyethylene wear by permitting maximal congruity between the femoral component and the articulating polyethylene surface is the central concept of mobile-bearing knees. Maximizing surface contact minimizes polyethylene stress, thereby reducing wear. To accommodate for rotational and translational forces during knee kinematics, the undersurface of the polyethylene is allowed to rotate, or glide, over a smooth tibial baseplate. A number of randomized controlled trials comparing mobile and fixed primary total knee replacements have been conducted. In addition, several institutional and single-surgeon cases series have been published. Joint arthroplasty registry reports and publications have investigated tibial component mobility. This review details the latest clinical research and registry findings on mobile versus fixed-bearing knees. Refereed/Peer-reviewed

OBJECTIVE Poor results after anterior cruciate ligament (ACL) reconstruction are often due to inaccurate graft placement. Numerous strategies have been advocated to improve accuracy and consistency of tunnel positioning, including computer-assisted navigation. Less expensive alternatives, such as intraoperative fluoroscopy and isometry, have also been advocated for confirming guide pin placement before reaming the femoral tunnel. It is unknown how often these techniques cause surgeons to change the location of their femoral tunnel at the time of surgery. We undertook this study to determine how often this approach results in repositioning of the guide pin before final graft placement. We hypothesized that a lower level of surgeon experience would lead to a higher frequency of repositioning compared to a higher level of experience. DESIGN Prospective, case series. SETTING Institutional. PATIENTS Intraoperative data were gathered prospectively from 413 consecutive, primary ACL reconstructions performed by the sports medicine group at our institution. Of the 413 procedures enrolled in this study, 407 were available for analysis. Six procedures were excluded because the tension isometer was unavailable during the procedure. INTERVENTIONS Isometry and fluoroscopy were used in all cases to aid in the accurate placement of the femoral tunnel. Femoral pin change based on the results of isometry or fluoroscopy was recorded. The percentage of cases involving a change in the femoral pin resulting from the use of these techniques was calculated. This percentage was also calculated separately for cases performed by a staff surgeon (fellowship-trained sports medicine staff) as well as less experienced surgeons (current sports medicine fellows). MAIN OUTCOME MEASURES The main outcome measurement was whether the femoral pin was changed. RESULTS Of the 407 procedures available for review, 62 (15%) of them involved a change in femoral pin position secondary to information provided by intraoperative isometry or fluoroscopy. In the procedures performed by more experienced surgeons, the pin was changed in 40 (16%) of 253 cases; in those performed by less experienced surgeons, it was changed in 22 (14%) of 154 cases. CONCLUSIONS The intraoperative use of isometry and fluoroscopy during ACL reconstruction led to changes in the femoral tunnel placement 15% of the time. The influence of these instruments on intraoperative decision making does not seem to diminish with surgical experience.

Orthopaedic registries are valuable for monitoring patient outcomes in real-world settings. Registries are useful for identifying procedure incidence and device utilization, evaluating outcomes, determining patients at risk for complications and reoperations, identifying devices in recall situations, assessing comparative effectiveness of procedures and devices, and providing data for research studies. In the present report, we describe how orthopaedic registries can be used to conduct research and how they compare with randomized controlled trials (RCTs) in regard to methodology. Using an example, a comparison of the performance of mobile and fixed bearings in total knee arthroplasty, we evaluate the differences between, and the similarities of, RCTs and registry cohort studies with regard to how they are conducted and how their findings are reported. Orthopaedic registry studies differ from RCTs in many ways and offer certain advantages. The strengths and limitations of registry cohort studies and RCTs must be understood to properly evaluate the literature.