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2010;92:117-132. doi:10.2106/JBJS.J.00807 J Bone Joint Surg Am.B. Low, Jr., Ronald W.B. Wyatt, Maria C.S. Inacio and T. Ted Funahashi Elizabeth W. Paxton, Robert S. Namba, Gregory B. Maletis, Monti Khatod, Eric J. Yue, Mark Davies, Richard

in the United StatesLigament Reconstruction Procedures in a Community-Based Registry A Prospective Study of 80,000 Total Joint and 5000 Anterior Cruciate

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A Prospective Study of 80,000 Total Joint and5000 Anterior Cruciate Ligament Reconstruction

Procedures in a Community-Based Registryin the United States

By Elizabeth W. Paxton, MA, Robert S. Namba, MD, Gregory B. Maletis, MD, Monti Khatod, MD, Eric J. Yue, MD, Mark Davies, MD,Richard B. Low Jr., MHA, Ronald W.B. Wyatt, MD, Maria C.S. Inacio, MS, and T. Ted Funahashi, MD

Introduction

Health-care costs in the United States have increased sub-stantially over time. From 1980 to 2007, the percentage of

gross national product spent on health care has increased from8.8% to 16%1. Total joint replacement is one of the most costlydiagnosis-related groups, with >600,000 procedures performedeach year in the United States2,3. The demand for total jointreplacement is expected to increase in the United States as aresult of advances in medical technology, an increased preva-lence of obesity, and an increasing aging population2,4. By 2030,annual volumes are projected to increase by 673% for primarytotal knee arthroplasty and by 174% for primary total hip ar-throplasty4. The demand for revision total knee and total hiparthroplasty is also projected to increase by 601% and 137%,respectively. Total knee and total hip arthroplasty costs are alsoexpected to increase dramatically, with annual hospital chargesestimated to reach $40.8 billion for primary total knee ar-throplasty and $17.4 billion for primary total knee arthroplastyby 20155. Similar increases in cost are projected for revisiontotal knee and total hip arthroplasty. Wilson et al. estimatedthat by 2030, total knee arthroplasty and total hip arthroplastywill cost Medicare over $50 billion6.

In addition to increases in demand and cost, recentconcerns about metal-on-metal bearing surfaces7 and recentimplant recalls and advisories have emphasized the need tomonitor total joint outcomes nationwide. The identification ofprocedures and implants associated with higher revision ratescould prevent revision procedures, improving care and ad-dressing the increased cost and demand associated with thisprocedure. Joint registries provide one potential solution forreducing total joint replacement implant variation and revisionrates. The Swedish Hip Register8-11 has demonstrated the ef-fectiveness of national registries in changing clinical practice.Feedback from the registry on cement techniques resulted inchanges in practices and a reduction in revision rates. Sweden’s

revision burden (percent revision of total cases) is half that ofthe estimated revision rate in the United States. The Swedishregistry not only has reduced total hip arthroplasty revisionrates but also has reduced implant variation, with six implantsbeing used for 70% of total hip arthroplasty procedures8,9.

While other countries such as Sweden8, Australia12,Denmark13, Germany14, Canada15, and Norway16 have estab-lished national registries to track and monitor devices, theUnited States currently does not have a mechanism for post-market surveillance of orthopaedic devices. Within the UnitedStates, registries have been limited to institutional or regionalgeographical efforts such as the Mayo Clinic17 or the HealthEastregistry18. Recently, the American Academy of OrthopaedicSurgeons (AAOS), Agency for Healthcare Research and Quality(AHRQ), and United States Food and Drug Administration(FDA) have explored mechanisms for the development of anational United States total joint replacement registry. A na-tional United States total joint replacement registry could po-tentially reduce total joint replacement revision rates throughthe early identification of implant failures and by providingfeedback to surgeons on techniques and implants associatedwith higher revision rates.

The Total Joint Replacement RegistryRecognizing the benefits of implant registries for our 8 millionpatients in eight geographical regions, the surgeons in ourintegrated health-care delivery system developed a total jointreplacement registry. The total joint replacement registry wasdeveloped in 2001 and was modeled after the Swedish regis-try8,11, with a focus on a minimal dataset and revision surgery asthe end point. The goals of the total joint replacement registryinclude (1) monitoring revisions, reoperations, and compli-cations such as surgical site infection, pulmonary embolism,and deep-vein thrombosis, (2) immediately identifying andnotifying patients and surgeons during implant recalls or ad-

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a memberof their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

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COPYRIGHT � 2010 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED

J Bone Joint Surg Am. 2010;92 Suppl 2:117-32 d doi:10.2106/JBJS.J.00807

visories, (3) identifying patients at risk for revisions and com-plications, (4) assessing the clinical effectiveness of implantsand techniques, and (5) providing the framework for more in-depth clinical research studies19-25. The total joint replacementregistry has been implemented at fifty hospitals in the sixgeographical regions in which we own our own hospitals, with90% voluntary participation from >350 orthopaedic surgeons,80% of whom are fellowship-trained. As of March 2010, thetotal joint replacement registry had >100,000 total joint re-placement cases registered, with 17,000 cases added each year.

Anterior Cruciate Ligament Reconstruction RegistryOn the basis of the success of the total joint replacement reg-istry, our surgeons also implemented an anterior cruciate lig-ament reconstruction registry in 2005, which tracks surgicalprocedures, techniques, graft types, fixation types, and im-plants. The goals of this registry include (1) identifying riskfactors that lead to degenerative joint disease, graft failure,meniscal failure, and failure to return to sports, (2) evaluatingoutcomes associated with different graft types and fixationtechniques, (3) describing the epidemiology of anterior cru-ciate ligament reconstruction procedures and patients, (4)monitoring complications, (5) assessing and comparing pro-cedure incidence rates, and (6) constructing a framework forfuture studies tracking anterior cruciate ligament reconstruc-tion outcomes. Similar to the total joint replacement registry,the anterior cruciate ligament reconstruction registry is im-plemented in six regions, with thirty-four sites and 208 dif-ferent surgeons participating. Although the anterior cruciateligament reconstruction uses a similar methodology, this reg-

istry is modular, with collection of patient-reported outcomesat specific centers. As of March 2010, 9200 cases were regis-tered, with 2500 new cases added each year.

The purposes of the present article are (1) to presenttotal joint replacement demographics, survival, and revisionrisk factors from a large community-based practice; (2) tohighlight the impact of the total joint replacement registry onclinical practice, patient safety, cost effectiveness, and researchwithin our integrated system; and (3) to present anteriorcruciate ligament reconstruction demographics, survival, andreoperation and complication rates from the same community-based practice.

Materials and MethodsData Source

The present study includes total joint replacement registrydata from April 2001 to March 2008 and anterior cruciate

ligament reconstruction data from February 2005 to June 2008.Registry data are collected prospectively through standardizeddocumentation at the point of care (i.e., during preoperative,intraoperative, and all postoperative encounters). The stan-dardized forms collect information on demographic character-istics, implant characteristics, surgical techniques, and outcomes(e.g., revisions, reoperations, infections, deep-vein thrombosis,and pulmonary embolism). Registry forms are supplementedwith existing administrative data from our electronic healthrecords and other independent databases (Fig. 1). Electronicscreening algorithms are applied to administrative databases todetect additional complications, reoperations, and revisions.Independent electronic health record operative modules and

Fig. 1

Total joint replacement registry database structure. SAS = SAS software (version 9.1.3; SAS Institute, Cary, North Carolina).

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TH E J O U R N A L O F B O N E & JO I N T SU R G E RY d J B J S . O R G

VO LU M E 92-A d S U P P L E M E N T 2 d 2010A PR O S P E C T I V E ST U D Y O F 80,000 TO TA L J O I N T A N D 5000 AN T E R I O R

CRU C I AT E LI G A M E N T RE C O N S T R U C T I O N PR O C E D U R E S

anesthesia databases are used to validate registry cases. All registryoutcomes are validated with use of a chart review methodologyfollowing CDC (Centers for Disease Control and Prevention) andAHRQ guidelines26-28.

Data ElementsPatient OutcomesThe main outcome of interest for the total joint replacementstudy was revision surgery, defined as removal or exchange of atleast one prosthetic component. Aseptic revision was defined asrevision for any reason, excluding infection. For the anteriorcruciate ligament reconstruction study, reoperation, revision ofligament reconstruction, meniscal injury, infection, deep-veinthrombosis, and pulmonary embolism were the main outcomevariables. Infections were defined according to the CDC guide-lines27, and deep-vein thrombosis and pulmonary embolismwere defined according to AHRQ guidelines26.

Patient CharacteristicsThe patient characteristics that were assessed in relation to totaljoint replacement survival included age (less than fifty-fiveyears of age versus fifty-five years of age or more), AmericanSociety of Anesthesiologists (ASA) score (<3 versus ‡3), body-mass index, diabetes status, primary diagnosis (osteoarthritisversus other), and sex. In the anterior cruciate ligament re-construction study, sex, age, and associated concurrent carti-lage and meniscal injuries were the main patient characteristicsevaluated in relation to study outcomes.

Hospital and Surgeon-Related VariablesThe main hospital and surgeon-related variables assessed in thetotal joint replacement study were annual hospital case volume,geographical region, and surgeon annual case volume. For totalknee arthroplasty, annual hospital volume was defined as small(fewer than fifty cases), medium (fifty to ninety-nine cases),and large (100 cases or more). For total hip arthroplasty, annualsurgeon volume was defined as small (fewer than ten cases),medium (ten to forty-nine cases), and large (fifty cases or more).These variables were not evaluated in the anterior cruciateligament reconstruction study.

Implant CharacteristicsThe total knee arthroplasty implant variables consisted of ce-ment fixation and platform design (mobile versus fixed bear-ing, cruciate retained versus posterior stabilized). Total hiparthroplasty implant characteristics included cement fixation,femoral head size (£28 mm, 32 mm, and ‡36 mm), and bearingsurfaces (conventional polyethylene, metal-on-metal surfaces,and highly cross-linked polyethylene). The anterior cruciateligament reconstruction study assessed the type of graft im-planted (autograft versus allograft, hamstring versus patellartendon autograft).

AnalysesDescriptive statistics such as means, standard deviations, andproportions were used to describe the study samples. Chi-

square, Fisher exact, and independent t tests were applied toevaluate group differences in demographic characteristics.Kaplan-Meier survival curves with revision as the end pointand log-rank tests were used to evaluate implant survival.Death and membership termination were used to censor datain the survival analyses. Multivariate Cox regression modelswere used to assess total joint replacement relative risk of re-vision. SAS (Version 9.1.3; SAS Institute, Cary, North Carolina)was used to analyze the data, with p < 0.05 as the statisticalthreshold.

Source of FundingThe registries are funded through the health plans in each re-gion. There was no external funding for these studies.

ResultsTotal Knee ArthroplastyPatient Demographics

As of March 31, 2008, there were 39,286 primary (94.1%)and 2458 revision (5.9%) total knee arthroplasty cases

registered. Females accounted for 62.5% of the primary and53.5% of the revision total knee arthroplasty procedures. Pa-tients younger than sixty-five years of age accounted for 37.3%of primary and 38.4% of revision cases. Osteoarthritis was themost common diagnosis among patients undergoing primarytotal knee arthroplasty (96.6%) (see Appendix). The prevalenceof diabetes in this population was 20.2% among patients un-dergoing primary total knee arthroplasty and 25.5% amongthose undergoing revision total knee arthroplasty. Most sur-geons used the parapatellar approach (75%) and cement fixa-tion (84%) when performing primary total knee arthroplastyprocedures. Patients undergoing revision total knee arthro-plasty had higher ASA scores than those undergoing primarytotal knee arthroplasty (p < 0.001). Infection (26.2%) andaseptic loosening (24.3%) were the most common diagnosesamong patients undergoing revision total knee arthroplasty(see Appendix).

Kaplan-Meier Survival Curves for Total Knee ArthroplastyOf the 39,286 primary total knee arthroplasties in the registryduring this time period, 667 (1.7%) were revised, with 281revisions due to infection (0.7%). During the seven-year study,3213 patients (8.2%) left the health plan membership, and1217 (3.1%) died. Patients who died and those who left thehealth plan membership were considered to be lost to follow-up (N = 4430; 11.3%) and were censored in the survivalanalysis. The cumulative survival rate at 5.5 years was 97.1%(95% confidence interval, 96.8% to 97.4%). Infection ac-counted for 42.6% of the primary total knee arthroplasty re-visions. Instability was the reason for revision in 16.2% of thecases. The cumulative survival rate at 5.5 years was 97.1% (95%confidence interval, 96.8% to 97.4%). Kaplan-Meier survivalcurves and log-rank tests indicated lower total joint replace-ment survival function for the following variables: an age of lessthan fifty-five years (p < 0.001), an ASA score of ‡3 (p < 0.001),a higher body-mass index (p < 0.001), comorbid diabetes (p <

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0.001), diagnoses other than osteoarthritis (p < 0.001), malesex (p < 0.001), uncemented fixation (p < 0.0001), and mobile-bearing platforms (p < 0.001) (Fig. 2) (see Appendix).

Risk Factors for Total Knee Arthroplasty RevisionVariables that were included in the multivariate Cox regressionmodel included age, ASA score, sex, body-mass index, primarydiagnosis, diabetes, surgeon and hospital annual case volumes,geographical region, fixation technique, and type of platform(mobile bearing versus fixed, cruciate retaining versus poste-rior stabilized). After adjustment for all variables, the riskfactors for total knee arthroplasty revision included an age ofless than fifty-five years (relative risk = 2.56; 95% confidenceinterval, 1.97 to 3.33; p < 0.001), an ASA score of ‡3 (relativerisk = 1.29; 95% confidence interval, 1.04 to 1.60; p = 0.02),diabetes (relative risk = 1.28; 95% confidence interval, 1.01 to1.62; p = 0.04), implant fixation without cement (relative risk =1.92; 95% confidence interval, 1.23 to 3.3; p = 0.004), and amobile-bearing platform (relative risk = 1.52; 95% confidenceinterval, 1.13 to 2.05; p = 0.006) (Fig. 3).

Total Hip ArthoplastyDemographic CharacteristicsAs of March 31, 2008, there were 21,548 (88.5%) primary and2809 (11.5%) revision total hip arthroplasty cases registered.Females accounted for 56.1% of the primary and 55.4% of the

revision cases. Patients younger than sixty-five years of ageaccounted for 44.7% of primary and 38.5% of revision cases.The prevalence of diabetes was 8.7% among patients under-going primary total hip arthroplasty and 7.9% among thoseundergoing revision total hip arthroplasty. Osteoarthritis wasthe most common diagnosis among patients undergoing pri-mary total hip arthroplasty (89.7%), whereas aseptic loosening(28.3%) and instability (31.1%) were the most common di-agnoses among those undergoing revision total hip arthro-plasty (see Appendix). Patients undergoing revision total hiparthroplasty had higher ASA scores than those undergoingprimary total hip arthroplasty (p < 0.001); 38.6% of thoseundergoing a revision procedure had an ASA score ‡3, com-pared with 31.9% of those undergoing a primary procedure.

ImplantsMetal-on-highly cross-linked polyethylene accounted for themajority (52%) of the primary total hip arthroplasty bearingsurfaces. Metal-on-metal and ceramic-on-ceramic accountedfor 8.4% and 1.9% of the primary bearing surfaces, respec-tively. The use of femoral head sizes of ‡36 mm increased overthe years, from 4.8% in 2002 to 54.4% in 2008. Metal femoralheads were used in the majority of cases for both primary(73.9%) and revision (69.6%) procedures. For primary proce-dures, cementless fixation (76.2%) was used most commonly,with hybrid fixation being used for an additional 15.9%.

Fig. 2

Kaplan-Meier curve showing implant survival after total knee arthroplasty (TKA), according to fixation technique, with

revision for aseptic causes as the end point. CI = confidence interval.

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Kaplan-Meier Survival Curves for Total Hip ArthroplastyOf the 21,550 primary total hip arthroplasties in the registryduring this seven-year study, 409 (1.9%) were revised, withseventy-eight implants (0.4%) being revised because of infec-tion. The most common reasons for revision after primarytotal hip arthroplasty cases were instability (49.1%) and in-fection (19.6%). Within the study period, 1923 (8.9%) patientsleft the health plan membership, and 876 (4.1%) died. Patientswho died and those who left the health plan membership wereconsidered to be lost to follow-up (N = 2799; 12.9%) and werecensored. The cumulative survival rate at 5.5 years was 97.3%(95% confidence interval, 96.8% to 98.2%).

Kaplan-Meier survival curves and log-rank tests indi-cated differences in survival function according to region (p =0.02), annual surgeon volume (p = 0.02), insert type (p <0.001), femoral head size (p < 0.001), and bearing surface (p <0.01) (Figs. 4 and 5). No differences in survival function wereobserved by fixation type (p = 0.0758) (Fig. 6).

Risk Factors for Total Hip Arthroplasty RevisionVariables included in the multivariate Cox regression modelsincluded age, ASA score, sex, body-mass index, primary di-agnosis, diabetes, surgeon and hospital annual case volumes,geographical regions, femoral head size, implant fixation, andbearing surface. After adjustment for all variables, the followingrisks factors for total hip arthroplasty revision were identified:female sex (relative risk = 1.29; 95% confidence interval, = 1.02to 1.62; p = 0.03), geographical region (relative risk = 1.33; 95%confidence interval = 1.04 to 1.70; p = 0.02), a surgeon annual

volume of fewer than thirty cases (relative risk = 1.28; 95%confidence interval = 1.02 to 1.61; p = 0.03), conventionalpolyethylene insert (relative risk = 1.78; 95% confidence in-terval = 1.32 to 2.39; p < 0.001), and a femoral head size of£28 mm (relative risk = 1.58; 95% confidence interval = 1.06 to2.35; p = 0.03). Hybrid implant fixation was found to be aprotective variable for total hip arthroplasty revision (relativerisk = 0.71; 95% confidence interval = 0.52 to 0.97; p = 0.03)(Fig. 7).

Anterior Cruciate Ligament ReconstructionDemographic CharacteristicsAs of June 2008, 4025 primary (95.2%) and 205 revision(4.8%) cases were registered. Males (mean age [and standarddeviation], 30 ± 10 years) accounted for the majority (65.1%)of the primary cases, and females (mean age, 28 ± 12 years)represented 34.9%. When we examined epidemiology trendsfrom 2001 to 2005, we observed that the incidence of anteriorcruciate ligament reconstruction increased for males who werefourteen to seventeen, twenty-six to twenty-nine, and fortyto forty-nine years old and increased for females who werefourteen to twenty-one years old, with the most dramatic in-crease for females who were fourteen to seventeen years old29.Our anterior cruciate ligament reconstruction registry dem-onstrated that fourteen to seventeen-year-old girls accountedfor the highest percentage of females undergoing anteriorcruciate ligament reconstruction (N = 419; 30.6%), whereasmales had a more even distribution between age groups (seeAppendix).

Fig. 3

Relative risk plot showing the risk factors (and 95% confidence intervals) for aseptic revision after total knee

arthroplasty (TKA). NS = not significant.

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Fig. 4

Fig. 5

Fig. 4 Kaplan-Meier curve showing implant survival after total hip arthroplasty (THA), according to femoral head size, with revision for aseptic causes as the

end point. CI = confidence interval. Fig. 5 Kaplan-Meier curve showing implant survival after total hip arthroplasty (THA), according to insert type, with

revision for aseptic causes as the end point. CI = confidence interval.

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Fig. 6

Fig. 7

Fig. 6 Kaplan-Meier curve showing implant survival after total hip arthroplasty (THA), according to fixation technique, with revision for aseptic causes as the

end point. CI = confidence interval. Fig. 7 Relative risk plot showing the risk factors (and 95% confidence intervals) for aseptic revision after total hip

arthroplasty (THA). NS = Not significant.

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The majority (62.3%) of patients undergoing primaryanterior cruciate ligament reconstruction had a meniscal in-jury, with 41.5% having an injury of the medial meniscus only,33.6% having lateral meniscal injury only, and 25% having aninjury of both menisci (see Appendix). Additionally, chondralinjuries were found in 20.8% of the cases. Among patients witha meniscal injury who had a primary procedure, 33.1% had ameniscal repair (including 39% of those with a medial meniscalinjury and 25% of those with a lateral meniscal injury), 51.7%had a partial meniscectomy, and 13.7% had the meniscus left insitu. Among patients who had a revision procedure, 29.8% hada meniscal repair, 61.5% had a partial meniscectomy, and 7.7%had the meniscus left in situ. The most common meniscalfixation was a third-generation all-inside suture-based repairsystem. Males (mean age, 31 ± 10 years) accounted for 55.4%of the revision cases, and females (mean age, 28 ± 12 years)accounted for 44.6%.

Graft Types for Anterior Cruciate Ligament ReconstructionAutografts were used in 61.2% of the primary procedures,whereas allografts were used in 83.3% of the revision proce-dures. Of the primary procedures, 35.4% involved bone-patellar tendon-bone grafts, 25.2% involved hamstrings grafts,and 36.4% involved allografts (see Appendix). Patellar tendonautografts were used slightly more frequently in males (37.2%)as compared with females (31.8%). Of the procedures involv-ing allograft, 29.5% involved tibialis anterior tendon graft,23.5% involved Achilles tendon graft, 19.3% involved bone-

patellar tendon-bone graft, and 19.0% involved tibialis poste-rior tendon graft.

Complication Rates for Anterior CruciateLigament ReconstructionThe overall rate of surgical site infection for the 4230 patientsundergoing anterior cruciate ligament reconstruction was 0.7%(N = 29), with six deep infections (0.14%) and twenty-threesuperficial infections (0.54%). Within ninety days postopera-tively, there were five cases of deep-vein thrombosis (0.1%) andfive cases of pulmonary embolism (0.1%) (Fig. 8).

Revision and Reoperation Rates for Anterior CruciateLigament ReconstructionOf the 4230 patients in the registry who were managed withprimary or revision anterior cruciate ligament reconstruction,12% left the health-plan membership and were considered lostto follow-up. Of the 4025 patients in the registry who weremanaged with primary anterior cruciate ligament reconstruc-tion, 178 (4.4%) had a reoperation and twenty-four (0.6%) hadrevision ligament surgery. The three most common reasons forreoperation on the index (ipsilateral) knee were meniscal orcartilage injury (34.3%), stiffness (18.9%), and infection (14%)(see Appendix). Operations on the contralateral knee were dueto anterior cruciate ligament reconstruction or other ligamentsurgery in 65.7% of cases and for meniscal injuries in 28.6% ofthe cases (see Appendix). For females, 90.0% of the contra-lateral procedures were performed for reconstruction of the

Fig. 8

Graph showing anterior cruciate ligament reconstruction registry validated outcomes, including the rates of revision,

reoperation, deep infection, superficial infection, deep-vein thrombosis (DVT), and pulmonary embolism (PE).

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anterior cruciate ligament or other ligaments and 10.0% wereperformed because of meniscal injuries. For males, 56% of thecontralateral procedures were performed for reconstructionof the anterior cruciate ligament and 36.0% were performedbecause of meniscal injuries. The cumulative survival rate foranterior cruciate ligament reconstruction at four years was90.7% (95% confidence interval, 86.9% to 93.4%). Kaplan-Meier survival curves and log-rank tests indicated differencesin survival function following procedures performed with al-lograft, bone-patellar tendon-bone autograft, and hamstringsautograft (p = 0.0055) (Fig. 9).

Time to SurgeryThe anterior cruciate ligament reconstruction registry identifieda difference in the rate of medial meniscal injury in associationwith increased time to surgery. Longer time from injury to sur-gery (six to twelve months and more than twelve months) wasassociated with an increased rate of medial meniscal injury whencompared with surgery within three months after the injury(odds ratio = 1.97 [p < 0.001] and 2.42 [p < 0.001], respectively).

DiscussionTotal Joint Registry

In the present study, we provide total joint replacement re-vision rates from a large community-based practice in the

United States. Cumulative total joint survival rates for totalknee arthroplasty and total hip arthroplasty at 5.5 years were

97.1% (95% confidence interval, 96.8% to 97.4%) and 97.3%(95% confidence interval, 96.8% to 98.2%), respectively.These rates are similar to those reported by other nationalregistries at five to six years of follow-up8,16. Total joint re-placement survival rates in our patients with an age of sixty-five years or more are similar to those reported in United StatesMedicare studies30-32.

Geographical region, female sex, lower annual surgeoncase volume (fewer than thirty cases), a conventional insert,and a femoral head size of £28 mm were found to be im-portant independent risk factors for aseptic revision followingtotal hip arthroplasty. Similar to the findings reported inother studies, the uncemented technique was associated witha higher relative risk of revision than hybrid fixation. Geo-graphical variation in the incidence of surgical procedureshas been described in the United States population31. TheSwedish total hip registry demonstrated variation in outcomeamong the various counties reporting8, mirroring our findings.Similar findings with regard to surgeon volume were reportedby Katz et al.32,33. Investigators from the Mayo Clinic recentlyreported a lower risk of hip instability following total hiparthroplasty performed with use of larger femoral headsize34. This clinical finding was unique and underscores theneed for a large sample size to detect a previously intuitive yetunproved finding. Our large registry once again takes thisclinical finding further, showing that larger femoral head sizereduces the risk of revision surgery.

Fig. 9

Kaplan-Meier curve showing survival after anterior cruciate ligament reconstruction according to graft type. CI = confidence

interval, PT BTB = bone-patellar tendon-bone, Quad H/S = quadriceps-hamstrings.

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Similar to the findings regarding total hip arthroplasty,variations in geographical regions were associated with a higherrelative risk of revision following total knee arthroplasty, con-sistent with early findings of the Swedish registry8. Findings alsoidentified younger age, a higher ASA score, diabetes, uncementedfixation, and a mobile-bearing design as independent risk factorsfor aseptic revision following total knee arthroplasty. The findingsthat younger age and uncemented implant fixation were riskfactors for total knee arthroplasty revision support findings thathave been reported previously35,36. In contrast to previous smaller,single-center studies that demonstrated good intermediate tolong-term survival of mobile-bearing designs37,38, our multicenterstudy suggests that mobile-bearing designs may contribute to anincreased risk of revision. This may be related to the complexityof the design or early detection of a potential problem identifiedby the larger sample size of the registry. Other risk factors for totalknee arthroplasty revision included higher ASA scores and dia-betic status. Consideration should be given for counseling pa-tients in these high-risk groups prior to performing total kneearthroplasty.

Similar to other total joint replacement registries, ourfindings suggest that feedback to surgeons can positively in-fluence clinical practice. The Swedish national hip registry has

influenced cement techniques and reduced the variation inimplants to decrease their revision rates. The Mayo Clinic hasalso identified improvements in care associated with registryfeedback. The HealthEast registry has demonstrated findingssimilar to our study in terms of unicompartmental knee ar-throplasty and uncemented techniques, resulting in reductionin these practices. These findings suggest that a nationalregistry could potentially improve the quality of care for or-thopaedic patients and reduce United States national revisionrates.

Changes in PracticeFeedback to surgeons on total joint surgical techniques andimplant performance, along with other published studies, hasresulted in changes in orthopaedic practice. For example, theregistry identified significant differences in revision rates betweenunicompartmental and total knee replacements (Fig. 10) andfeedback from the registry and the findings of other studies re-sulted in a reduction in unicompartmental knee arthroplastyvolume (Fig. 11). The finding of higher revision rates in associ-ation with smaller femoral head sizes, along with the findingsof other published studies, was another example of feedback toparticipating surgeons that resulted in a reduction in the use of

Fig. 10

Kaplan-Meier curve showing implant survival after total knee arthroplasty (TKA) and unicompartmental knee arthroplasty

(UKA), with aseptic revision as the end point. CI = confidence interval. (Reproduced, with modification, from: Paxton EW,

Inacio M, Slipchenko T, Fithian DC. The Kaiser Permanente National Total Joint Replacement Registry. Permanente J.

2008;12:15. Reprinted with permission.)

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small femoral head sizes (Figs. 4 and 12). The registry alsoidentified higher revision rates for cementless total knee ar-throplasty fixation, leading to a reduction of cementless totalknee arthroplasty (Figs. 2 and 13)28. Specific surgeon profilesare also confidentially provided to participating surgeons forpractice assessment and comparison of their own personalrevision and complication rates with medical center and re-gional benchmarks.

Patient SafetyThe registries also play a critical role in patient safety. Patientsaffected by implant recalls and advisories are identified andnotified immediately. During the study period, the orthopaedicimplant registries were used to track and monitor eight recallsand advisories (Table I). More recently, the total joint re-placement registry has been used to identify and monitorpatients with the ASR Hip Resurfacing System and the ASR XL

Fig. 11

Graph showing the annual percentage of knee arthroplasties that were unicompartmental.

Fig. 12

Graph showing annual percentage of total hip arthroplasties (THA) involving 28-mm femoral head

implants.

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Acetabular System (DePuy, Warsaw, Indiana). Another benefitof the registries is the potential for early identification of de-fective devices. Although a randomized controlled trial designmay provide a higher level of scientific evidence, randomized

controlled trials can take a long time to recruit an adequatesample size for the required power to detect rare adverse events.Problems with implants may be identified early in a registry as aresult of large sample sizes.

Fig. 13

Graph showing the volume of total knee arthroplasty (TKA) without cement.

TABLE I Implant Advisories and Recalls During Study Period

Issue Date Description Manufacturer Alert Type FDA Class* Implant Type Registry

07/21/2008 Durom Cup Zimmer Recall Class 2: lessserious risk

Knee cup Total jointreplacement

11/28/2007 Trident AcetabularPSL Cup and TridentHemispherical Cup

StrykerHowmedicaOsteonics

Recall Class 2: lessserious risk

Hip cup Total jointreplacement

11/23/2007 TC Plus, VKS, RT PlusKnee Components

Smith & Nephew Recall Kneecomponent

Total jointreplacement

08/30/2007 Trident AcetabularPSL Cup

Stryker HowmedicaOsteonics

Recall Class 2: lessserious risk


08/23/2007 Calaxo BioabsorbableScrews

Smith & Nephew Recall Class 2: lessserious risk

Screw Anterior cruciateligamentreconstruction

07/12/2007 BHR Acetabularand Dysplasia Cup

Smith & Nephew Recall Class 1: highrisk


10/12/2006 Allograft MusculoskeletalTransplantFoundation

Recall Class 3: minimalrisk

Ligamentallografts

Anterior cruciateligamentreconstruction

06/10/2005 Polyethylene Inserts DePuy Recall Class 2: lessserious risk

Patellarcomponent

Total jointreplacement

*FDA = United States Food and Drug Administration.

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In addition to the key role in implant device monitoring,the registries are also important for identifying patient riskfactors associated with revisions, infections23, and venousthromboembolic events. This information is used by oursurgeons and patients for evaluating treatment options andsetting expectations regarding surgical outcomes. Prognosticstatistical models have been used to develop web-based re-vision risk calculators for use by our surgeons in clinicaldecision-making.

Cost EffectivenessThe registries provide an important role in evaluating newtechnology and marketing claims. New, more advanced im-plant technologies are frequently introduced into the mar-ketplace at higher costs, despite the lack of evidence ofsuperior performance. The registries have been used to evaluatenew technologies such as high-flex and sex-specific knee im-plants with use of the collective experience of community-basedsurgeons. The registries also have been used to assess the com-parative effectiveness of implants, with the focus on selecting thebest implants for our patients in value-based contracting. An-other area that demonstrates cost effectiveness is the estab-lishment of virtual visits, with use of the registries to identifypatients who are due for follow-up. The registries automaticallygenerate a list of patients who are due for follow-up and e-mailthe list to providers for postoperative follow-up. Providers canthen follow up with patients by phone or e-mail, reducing theneed for clinical visits.

ResearchFinally, the registries provide a foundation for more in-depthresearch projects. Initial publications have focused on (1) earlyfailures and postoperative complications20,23,24, (2) epidemiol-ogy of total joint replacements and anterior cruciate ligamentreconstruction procedures21,29, (3) health care utilization afterdischarge19, and (4) antibiotic-loaded cement in knee replace-ments and postoperative infections23. As the registry grows andmatures, the opportunities for research will also increase.

Anterior Cruciate Ligament Reconstruction RegistryOur anterior cruciate ligament reconstruction registry providesthe first reported revision and reoperation rates from a largecommunity practice within the United States with >200 par-ticipating surgeons. The primary anterior cruciate ligamentreconstructions that were included in our registry during thefour-year study period were associated with a revision rate of0.6% and a reoperation rate of 4.4%. This compares similarlyto the 6.6% reoperation rate reported by Lyman et al. in astatewide study that evaluated reoperation rates within oneyear following procedures coded for anterior cruciate ligamentreconstruction in the state of New York39. The advantage of ourregistry is that it provides further details, including reasons forreoperation, laterality, the incidence and treatment of associ-ated injuries, and graft and fixation types, while also providingcomparative graft survival rates for patellar tendon autografts,hamstrings autografts, and allografts. Early results suggest

differential survival rates between the three graft types, and weare currently investigating this finding.

Our study revealed that the three most common reasonsfor reoperations on the index knee following primary anteriorcruciate ligament reconstruction were for meniscal injury(34.3%), stiffness (18.9%), and infections (14.0%). Reopera-tion on the index knee was three times more likely than re-operation on the contralateral knee. For the contralateral knee,the most common procedures were ligament reconstruction(65.7%) and meniscal surgery (28.6%).

Of interest is our finding that contralateral reoperationsin our female population were more likely to be for ligamentinjuries, whereas meniscal injuries were more common formales. Another common cause for reoperations was stiffness,and our plans are to investigate variances across medical cen-ters to see if factors such as postoperative rehabilitation pro-tocols have an impact on this reoperation rate. Removal offixation hardware was the fourth-most-common reason for re-operation, and as we gather additional data, we aim to determinewhether specific implant designs or materials lead to lower re-operation rates.

The finding that females between the ages of fourteenand seventeen years had the highest incidence and an increasedannual rate of anterior cruciate ligament reconstruction haveled us to focus on this group for injury prevention such aspreseason intervention with an online educational video tar-geted at athletes in this high-risk group. Our findings also havesuggested that longer time from injury to surgery (six to twelvemonths and more than twelve months) was associated with anincreased rate of medial meniscal injury. These findings com-pare similarly with those from the Norwegian registry40. Thesefindings emphasize the need to improve on the surveillanceof anterior cruciate ligament injuries with appropriate inter-ventions to prevent further injury, particularly in our youngathletes.

The overall rates of deep-vein thrombosis and pulmo-nary embolism following anterior cruciate ligament recon-struction in this study were low. Therefore, we have not madespecific recommendations regarding prophylaxis against deep-vein thrombosis and pulmonary embolism at this time.

Strengths and WeaknessesThe strengths of this study are the large community-basedsample with contemporary implants. A large prospective co-hort study such as this is valuable for identifying rare outcomeswith a large sample size. The findings of associations betweenvariables and these outcomes are many times unique to thistype of population-based design; however, it cannot replacerandomized controlled trials for identifying causation of var-iable to outcome. For many clinical questions, randomizedcontrolled trials are not feasible, are unethical, or are prohib-itive in cost. A registry allows for the collection of clinicallyrelevant outcomes and reflects real clinical practice. The bar-riers to receiving health care are limited in an integrated healthmaintenance organization. Our integrated system allows forthe capture of patient, surgeon, implant, hospital variables, and

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outcomes that occur in any inpatient and outpatient setting,allowing longitudinal follow-up data collection. Our systemalso has low attrition rates, with <12% of patients lost to follow-up over a seven-year period. These features offer a distinct ad-vantage over similar United States registries.

Our study has several limitations. The registry is a largeprospective cohort, whereas some of the outcome data arecollected retrospectively from administrative databases. Ascoding accuracy is important in outcome analysis, our registrydata are validated with chart reviews, improving the overallaccuracy of the data captured. Another study limitation is theshort to intermediate-term length of follow-up. Althoughtotal joint replacements can survive for many years, evaluationof early failures can provide important information abouttechnical failures. In addition to short-to-intermediate-termfollow-up, the registries are also limited by a focus on revision,reoperations, and complications as the key end points. Al-though we have implemented the patient-reported outcomesat specific centers, participation rates are <50%. Web-basedsurveys and virtual visits are in the process of implementationto increase response rates prior to reporting these patient-reported outcomes.

Future Areas of FocusFuture directions for the registries program include interactivepatient web sites with patient-reported outcomes, automatedpost-market surveillance with real-time signal detection ofadverse events, expansion of our revision risk calculator to assessother complications and outcomes (i.e., deep-vein thrombosis,pulmonary embolism, hospital readmissions, and postopera-tive medical complications), and radiographic assessment. Weare also in the process of automating the virtual visits processwith automated orders for radiographs and a web-basedquestionnaire.

The Need for a National United States RegistryWhile other countries have established national registries totrack orthopaedic implant volume, utilization, and revisionrates8,12-14,16,41, national United States studies have relied on hos-pital discharge (e.g., National Hospital Discharge Survey, Na-tionwide Inpatient Sample)2,4,5 and CMS (Centers for Medicareand Medicaid Services) data30,31,42 to provide estimates of ortho-paedic procedure volumes, complications, and revision rates.Although these studies provide important estimates of com-plications and revisions, they are limited by the reliance onICD-9-CM (International Classification of Diseases, NinthRevision, Clinical Modification) coding developed for billingpurposes. Inherent problems associated with ICD-9-CM codesinclude hospital variation in coding practices, inaccuratecoding, problems with sensitivity and specificity, and inadequateclinical and implant data. Medicare data are further limited by theexclusion of patients under the age of sixty-five years, who are athighest risk for revision surgery36,43, and lack of laterality to dis-tinguish joints and associated outcomes. These limitations em-phasize the importance of a national United States registry withstandardized coding and terminology, detailed implant informa-

tion, and laterality necessary to fully assess United States utiliza-tion rates, complications, and revision rates.

The development of a United States national registryis critical for assessing revision rates and implant utilization,for tracking implanted devices during recalls and advisories, forconducting post-market surveillance of new technologies, forearly identification of defective devices, and for assessing thecomparative effectiveness of devices. Ideally, a United Statesregistry could provide feedback on techniques and devicessimilar to the Swedish registry and could reduce national revi-sion rates. A national registry may be feasible through changesin policies and regulations or through collaborative efforts ofthe AAOS, surgeons, manufacturers, payers, and hospitals.The FDA and AHRQ have launched efforts in support of na-tional networks and multicenter grants that may provide sup-port for initial efforts in this direction. A national registrycould also be developed through collaboration with distrib-uted networks of established institutional and regional regis-tries. Regardless of how it is accomplished, the need for anational registry for specific orthopaedic procedures has beenwell substantiated.

Conclusions

Cumulative survival rates of total joint replacement and an-terior cruciate ligament procedures from a large community-

based practice are similar to rates reported by other regional andnational registries.

Registries provide an alternative solution for comparativeresearch when randomized controlled trials are impractical, areunethical, or require long-term follow-up with large sample sizesto detect rare complications.

Registries provide real-world results that may be moregeneralizable than randomized controlled trials and can posi-tively impact clinical practices, safety, cost effectiveness, andresearch.

There is a need for a national United States registry tomonitor device performance. Medicare data seem to provide apotential solution to the national need for a United States reg-istry, but our results indicate that a large portion of the patientsat highest risk for revision would not be accounted for with useof Medicare as the primary data source.

Although our registries provide a model for a UnitedStates national registry, the reliance of the registries on ourintegrated system may not be transferable to other health-care systems.

A network of established institutional and regional reg-istries may provide a method for the development of a UnitedStates national registry.

AppendixFigures showing additional survival curves by the distri-bution of diagnoses, procedures, and ages are available with

the electronic version of this article on our web site at jbjs.org (goto the article citation and click on ‘‘Supporting Data’’). n

NOTE: The authors would like to acknowledge Don Fithian, MD, our orthopaedic surgeons, and theregistry staff for their important contributions.

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Elizabeth W. Paxton, MARichard B. Low Jr., MHAMaria C.S. Inacio, MSSurgical Outcomes & Analysis Unit of Clinical Analysis,Southern California Permanente Medical Group, San Diego,3033 Bunker Hill Street, San Diego, CA 92109

Robert S. Namba, MDT. Ted Funahashi, MDDepartment of Orthopaedics,Southern California Permanente Medical Group,Orange County, 6670 Alton Parkway,Irvine, CA 92618

Gregory B. Maletis, MDMonti Khatod, MDDepartment of Orthopaedics,

Southern California Permanente Medical Group,Baldwin Park, 1011 Baldwin Park Boulevard,Baldwin Park, CA 91706

Eric J. Yue, MDDepartment of Orthopaedics, Permanente Medical Group,Sacramento, 2025 Morse Avenue, Sacramento, CA 95825

Mark Davies, MDDepartment of Orthopaedics,Permanente Medical Group, San Jose,260 International Circle,San Jose, CA 95119

Ronald W.B. Wyatt, MDDepartment of Orthopaedics, Permanente Medical Group,Walnut Creek, 1426 South Main Street, Walnut Creek, CA 94596

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