Patient-Specific Implants for Focal Cartilage Lesions in The Knee: Implant Survivorship Analysis up to Seven Years Post-Implantation.

In the quest for increased surgical precision and improved joint kinematics, Computer-Assisted Orthopedic Surgery (CAOS) shows promising results for both total and partial joint replacement. In the knee, computer-assisted joint design can now be applied to the treatment of younger patients suffering pain and restriction of activity due to focal defects in their femoral articular cartilage. By taking MRI scans of the affected knee and digitally segmenting these scans, we can identify and map focal defects in cartilage and bone. Metallic implants matched to the defect can be fabricated, and guide instrumentation to ensure proper implant alignment and depth of recession in the surrounding cartilage can be designed from segmented MRI scans. Beginning in 2012, a series of 682 patient-specific implants were designed based on MRI analysis of femoral cartilage focal defects, and implanted in 612 knees. A Kaplan-Meier analysis found a cumulative survivorship of 96% at 7-year follow-up from the first implantation. Fourteen (2.3%) of these implants required revision due to disease progression, incorrect implant positioning, and inadequate lesion coverage at the time of surgery. These survivorship data compare favorably with all other modes of treatment for femoral focal cartilage lesions and support the use of patient-specific implants designed from segmented MRI scans in these cases.

Capsular Sparing Total Hip Replacement Technique Applied with a Dual-mobility Cup to Reduce Dislocations.

Regardless of the surgical approach used, dislocation remains a complication following total hip replacement. In recent years, newer technologies, such as the use of large femoral heads, have reduced the rate of postoperative dislocation. The combination of such technology, together with a soft tissue repair technique, may reduce the dislocation rate even further. A single surgeon performed 513 primary total hip replacements on 505 patients using a posterior approach utilizing a technique designed to spare the capsule. There were 257 males and 248 females. Age ranged from 39 to 92 years. Surgeries were performed from January 2012 to December 2015. Implants used were cementless dual-mobility cups and cementless femoral stems. In all cases, the posterior capsule was incised and retracted, but not excised. Following implant placement, the capsule was repaired using a fiber reinforced suture. The superior border of the capsular incision, just above the piriformis, was sutured to the superior capsule or gluteus minimus muscle. The intent of this repair was to completely incarcerate the femoral head. Patients were followed at two weeks, six weeks, three months, one year, three years, and five years. Follow up was one to five years post-implantation. The dislocation rate was zero. The combination of a large dual-mobility femoral head, combined with a soft tissue repair that spares the deep capsule, has the potential to significantly reduce dislocation rates when using the posterior approach to the hip.

Which Clinical and Patient Factors Influence the National Economic Burden of Hospital Readmissions After Total Joint Arthroplasty?

BACKGROUND: The Affordable Care Act of 2010 advanced the economic model of bundled payments for total joint arthroplasty (TJA), in which hospitals will be financially responsible for readmissions, typically at 90 days after surgery. However, little is known about the financial burden of readmissions and what patient, clinical, and hospital factors drive readmission costs. QUESTIONS/PURPOSES: (1) What is the incidence, payer mix, and demographics of THA and TKA readmissions in the United States? (2) What patient, clinical, and hospital factors are associated with the cost of 30- and 90-day readmissions after primary THA and TKA? (3) Are there any differences in the economic burden of THA and TKA readmissions between payers? (4) What types of THA and TKA readmissions are most costly to the US hospital system? METHODS: The recently developed Nationwide Readmissions Database from the Healthcare Cost and Utilization Project (2006 hospitals from 21 states) was used to identify 719,394 primary TJAs and 62,493 90-day readmissions in the first 9 months of 2013 based on International Classification of Diseases, 9th Revision, Clinical Modification codes. We classified the reasons for readmissions as either procedure- or medical-related. Cost-to-charge ratios supplied with the Nationwide Readmissions Database were used to compute the individual per-patient cost of 90-day readmissions as a continuous variable in separate general linear models for THA and TKA. Payer, patient, clinical, and hospital factors were treated as covariates. We estimated the national burden of readmissions by payer and by the reason for readmission. RESULTS: The national rates of 30- and 90-day readmissions after THA were 4% (95% confidence interval [CI], 4.2%-4.5%) and 8% (95% CI, 7.5%-8.1%), respectively. The national rates of 30- and 90-day readmissions after primary TKA were 4% (95% CI, 3.8%-4.0%) and 7% (95% CI, 6.8%-7.2%), respectively. The five most important variables responsible for the cost of 90-day THA readmissions (in rank order, based on the Type III F-statistic, p < 0.001) were length of stay (LOS), all patient-refined diagnosis-related group (APR DRG) severity, type of readmission (that is, medical- versus procedure-related), hospital ownership, and age. Likewise, the five most important variables responsible for the cost of 90-day TKA readmissions were LOS, APR DRG severity, gender, hospital procedure volume, and hospital ownership. After adjusting for covariates, mean 90-day readmission costs reimbursed by private insurance were, on average, USD 1324 and USD 1372 greater than Medicare (p < 0.001) for THA and TKA, respectively. In the 90 days after TJA, two-thirds of the total annual readmission costs were covered by Medicare. In 90 days after THA, more readmissions were still associated with procedure-related complications, including infections, dislocations, and periprosthetic fractures, which in aggregate account for 59% (95% CI, 59.1%-59.6%) of the total readmission costs to the US healthcare system. For TKA, 49% of the total readmission cost (95% CI, 48.8%-49.6%) in 90 days for the United States was associated with procedure issues, most notably including infections. CONCLUSIONS: Hospital readmissions up to 90 days after TJA represent a massive economic burden on the US healthcare system. Approximately half of the total annual economic burden for readmissions in the United States is medical and unrelated to the joint replacement procedure and half is related to procedural complications. CLINICAL RELEVANCE: This national study underscores LOS during readmission as a primary cost driver, suggesting that hospitals and doctors further optimize, to the extent possible, the clinical pathways for the hospitalization of readmitted patients. Because patients readmitted as a result of infection, dislocation, and periprosthetic fractures are the most costly types of readmissions, efforts to reduce the LOS for these types of readmissions will have the greatest impact on their economic burden. Additional clinical research is needed to determine the extent to which, if any, the LOS during readmissions can be reduced without sacrificing quality or access of care.

Has Health Care Reform Legislation Reduced the Economic Burden of Hospital Readmissions Following Primary Total Joint Arthroplasty?

BACKGROUND: The purpose of this study was to determine whether the cost of readmissions after primary total hip and knee arthroplasty (THA and TKA) has decreased since the introduction of health care reform legislation and what patient, clinical, and hospital factors drive such costs. METHODS: The 100% Medicare inpatient dataset was used to identify 1,654,602 primary THA and TKA procedures between 2010 and 2014. The per-patient cost of readmissions was evaluated in general linear models in which the year of surgery and patient, clinical, and hospital factors were treated as covariates in separate models for THA and TKA. RESULTS: The year-to-year risk of 90-day readmission was reduced by 2% and 4% (P < .001) for THA and TKA, respectively. By contrast, the cost of readmissions did not change significantly over time. The 5 most important variables associated with the cost of 90-day THA readmissions (in rank order) were the nature of the readmission (ie, due to medical or procedure-related reasons), the length of stay, hospital's teaching status, discharge disposition, and hospital's overall total joint arthroplasty volume. The top 5 factors associated with the cost of 90-day TKA readmissions were (in rank order) the length of stay, hospital's teaching status, discharge disposition, patient's gender, and age. CONCLUSION: Although readmission rates declined slightly, the results of this study do not support the hypothesis that readmission costs have decreased since the introduction of health care reform legislation. Instead, we found that clinical and hospital factors were among the most important cost drivers.

Which Hospital and Clinical Factors Drive 30- and 90-Day Readmission After TKA?

BACKGROUND: The purpose of this study was to analyze the hospital, clinical, and patient factors associated with inpatient readmission after total knee arthroplasty (TKA) in the Medicare population and to understand the primary reasons for readmission. METHODS: The Medicare 100% national hospital claims database was used to identify 952,593 older patients (65+) with a primary TKA in 3848 hospitals between 2010 and 2013. A multilevel logistic regression analysis with a clustered data structure was used to investigate the risk of all-cause 30- and 90-day readmission, incorporating hospital, clinical, and patient factors. RESULTS: At 30 days, readmission ranged from 0% to 22% (median, 4.9%), whereas at 90 days, readmission ranged from 0% to 32% (median, 8.6%). Geographic census region, hospital procedure volume, rural hospital location, and nonprofit ownership were the only significant hospital factors among those we studied. Evaluation of clinical factors showed use of a perioperative transfusion was associated with 13% greater risk; patients discharged to home had 25% lower risk; and surgeon volume and length of stay were also significant. These effect sizes were at least comparable to patient factors, such as age, gender, comorbidities, and socioeconomic status. The top 5 most frequently reported primary reasons for 30- or 90-day readmission in TKA were surgery and medical related: wound infection, deep infection, atrial fibrillation, cellulitis and abscess of leg, or pulmonary embolism. CONCLUSION: The results of this study support further optimization of anti-infection measures, both intraoperative and postoperative, to reduce the broad variation in hospital readmissions.

Hospital, Patient, and Clinical Factors Influence 30- and 90-Day Readmission After Primary Total Hip Arthroplasty.

BACKGROUND: The purpose of this study was to analyze the hospital, clinical, and patient factors associated with inpatient readmission after total hip arthroplasty (THA) in the Medicare population and to understand the primary reasons for readmission. METHODS: The Medicare 100% national hospital claims database was used to identify 442,333 older patients (65+) with a primary THA in 3730 hospitals between 2010 and 2013. A multilevel logistic regression analysis with a clustered data structure was used to investigate the risk of all-cause 30- and 90-day readmission, incorporating hospital, clinical, and patient factors. RESULTS: At 30 days, 5.8% (median) of the patients were readmitted, whereas at 90 days, 10.5% (median) were readmitted. Geographic census region, hospital procedure volume, and nonprofit ownership were the only significant hospital factors among those we studied. Overall, clinical factors explained more of the variation in readmission rates than general hospital factors. Use of a perioperative transfusion was associated with 14% greater risk, patients discharged to home had 28% lower risk, and surgeon volume and length of stay were also significant risk factors. The top 5 most frequently reported primary reasons for 30-day readmission in THA were procedure related: dislocation (5.9%), deep infection (5.1%), wound infection (4.8%), periprosthetic fracture (4.4%), or hematoma (3.4%). CONCLUSION: These findings support further optimization of the delivery of care-both intraoperative and postoperative-to reduce the broad variation in hospital readmissions.

Prevalence and Costs of Rehabilitation and Physical Therapy After Primary TJA.

This study evaluated the trends in discharge patterns and the prevalence and cost of post-discharge PT. The 5% Medicare database (1997-2010) was used to identify 50,886 primary THA and 107,675 TKA patients. More than 50% of patients were discharged from hospital to an inpatient facility. There were an increase in discharges to skilled nursing units and a reduced rate to rehabilitation facilities. In contrast to hospital, surgeon reimbursement, and implant costs, the average annual PT cost per patient rose through the study period. Approximately 25% of PT costs were used on less common modalities. PT costs more than $648 million a year. With the increased pressure to control costs for primary TJA, these patterns may change unless PT effectiveness can be demonstrated.

No differences found in bearing related hip survivorship at 10-12 years follow-up between patients with ceramic on highly cross-linked polyethylene bearings compared to patients with ceramic on ceramic bearings.

At a minimum follow-up of ten years we compared clinical and radiographic findings and survivorship in a cohort of 412 patients (447 hips) who received alumina on alumina CoC bearings to findings from a cohort of 216 patients (228 hips) with alumina on highly cross-linked polyethylene (HXLPE) bearings. All patients were operated for osteoarthritis. With bearing-related complications as endpoint, analysis showed no significant difference in survivorship between cohorts (99.8% for the CoC vs. 99.4% for HXLPE). In addition, there were no significant differences in clinical and radiographic findings between cohorts. We concluded that alumina on HXLPE bearings are a reasonable lower cost alternative to ceramic on ceramic bearing couples.

Complications, mortality, and costs for outpatient and short-stay total knee arthroplasty patients in comparison to standard-stay patients.

The purpose of the present study is to determine the differences in cost, complications, and mortality between knee arthroplasty (TKA) patients who stay the standard 3-4 nights in a hospital compared to patients who undergo an outpatient procedure, a shortened stay or an extended stay. TKA patients were identified in the Medicare 5% sample (1997-2009) and separated into the following groups: outpatient, 1-2 days, 3-4 days, or 5+ days inpatient. At two years, costs associated with the outpatient and the 1-2 day stay groups were $8527 and $1967 lower than the 3-4 day stay group, respectively. Out to 2 years, the outpatient and 1-2 day stay groups reported less pain and stiffness, respectively, though the 1-2 day group also had a higher risk for revision.

Excellent fixation achieved with cementless posteriorly stabilized total knee arthroplasty.

Cementless posteriorly stabilized (PS) total knee arthroplasty has not been widely accepted primarily because of prior unpredictable results and concern about micromotion at the tibial fixation interface caused by the cam/post interaction. A prospective consecutive series of 114 cementless, tricompartmental periapatite-coated single-radius PS implants in 110 patients with a mean age 62 years was performed to determine if initial stability and biologic fixation could be achieved. At a mean follow-up of 36 months, all implants demonstrated radiographic evidence of stable biologic fixation with no evidence of loosening, osteolysis, stress shielding, or progressive radiolucent lines. Based on these early results, cementless, periapatite-coated single-radius PS total knee arthroplasty offers marked promise.

Review: biomechanical issues in total hip replacement.

During total hip arthroplasty, the biomechanics of the joint may be altered by removal of bone and by a change in the center of rotation of the joint. Joint pathologies existing at the time of reconstruction may also affect post-operative joint motion. In order to achieve optimized biomechanics of the replaced joint, it is important to understand the muscle actions that are involved in joint movement and the forces that are imposed on the construct by patient activity. To ensure survivorship of the replacement, intraoperative and long-term stability of the components making up the joint within host bone must be achieved. The patients receiving total hip replacements in the twenty first century tend to be younger, heavier, more active and longer lived than the patients who first received hip implants. Thus, biomechanical decisions are becoming even more important for long-term survivorship of the reconstruction.

Risk of subsequent revision after primary and revision total joint arthroplasty.

BACKGROUND: Revision is technically more demanding than primary total joint arthroplasty (TJA) and requires more extensive use of resources. Understanding the relative risk of rerevision and risk factors can help identify patients at high risk who may require closer postsurgical care. OBJECTIVES/PURPOSES: We therefore evaluated the risk of subsequent revision after primary and revision TJA in the elderly (65 years or older) patient population and identified corresponding patient risk factors. PATIENTS AND METHODS: Using the 5% Medicare claims data set (1997-2006), we identified a total of 35,746 patients undergoing primary THA and 72,913 undergoing primary TKA; of these, 1205 who had THAs and 1599 who had TKAs underwent initial revision surgery. The rerevision rate after primary and revision TJAs was analyzed by the Kaplan-Meier method. The relative risk of revision surgery for primary and revision TJAs was compared using hazard ratio analysis. RESULTS: The 5-year survival probabilities were 95.9%, 97.2%, 81.0%, and 87.4% for primary THA and TKA and revision THA and TKA, respectively. Patients with revision arthroplasty were five to six times more likely to undergo rerevision (adjusted relative risk, 4.89 for THA; 5.71 for TKA) compared with patients with primary arthroplasty. Age and comorbidities were associated with initial revision after primary THA and TKA. CONCLUSIONS: Patients should undergo stringent preoperative screening for preexisting health conditions and careful patient management and followup postoperatively so as to minimize the risk of an initial revision, which otherwise could lead to a significantly greater likelihood of subsequent rerevisions.

Early- and late-term dislocation risk after primary hip arthroplasty in the Medicare population.

From 1998 to 2007 Medicare 5% national sample dataset, 39 271 primary total hip arthroplasty (THA) patients were identified. Dislocations within 2 years (early) and after 2 years (late) of primary THA were identified. Cox regression was used to evaluate patient, hospital, and procedure characteristics for risk of dislocation, and 1540 (3.92%) and 451 (1.15%) patients were diagnosed with early and late dislocations, respectively. Dislocation rate at 6 months' follow-up decreased steadily between 1998 and 2007 from 4.21% to 2.14%. Early and late dislocation risks were lower by 35% (P < .001) and 43% (P = .01), respectively, for patients operated during 2004 and 2007 compared with 1998 and 2003. Higher Charlson index scores (i.e., more comorbid conditions) and surgeon volume were significant risk factors (P < or = .04). Decrease in dislocation risks after primary THA seems to coincide with increasing use of larger diameter femoral heads. An awareness of risk factors for dislocation can help surgeons identify high-risk patients so as to prescribe appropriate intervention strategies.

Biomechanical comparison of 2 proximally coated femoral stems: effects of stem length and surface finish.

Proximally hydroxyapatite-coated stems have performed well clinically but produced moderate proximal stress shielding and midstem cancellous condensation. Stem modification (stem shortening and distal tip polishing) has resulted in greater incidence of thigh pain. We performed a retrospective finite element analysis of the effects of stem length and surface finish to determine if midstem fixation could be avoided and the results could relate to the clinical outcomes. The modified short stem not only produced moderately less proximal bone resorption but also exhibited greater instability with 40% to 94% greater bone-implant relative motion at the stem tip. Bone formation potential at the transition between the coated and uncoated regions of both stems was observed based on changes in strain energy density. These findings are consistent with previous radiographic and clinical comparisons of short- and long-stem designs. Increased pain incidence for short-stem patients may be related to decreased implant instability and increased interface relative motion.

Role of surgical position on interface stress and initial bone remodeling stimulus around hip resurfacing arthroplasty.

Valgus alignment of femoral resurfacing components has been advocated to reduce proximal femur loading and thus minimize the risk for femoral neck fractures. However, such reduction in loading may exacerbate undesirable stress shielding. This study examined the effect of extreme implant orientations (+/-15 degrees ) and stem canal overreaming on initial bone remodeling stimulus using finite element models. The changes in implant-cement interface stresses due to implant alignment were also evaluated. The valgus model showed increased initial bone resorption stimulus, which extended distally and peripherally around the femoral neck. The peak implant-cement interface shear stress for the varus model was 10.9 MPa, exceeding the interface shear strength. Overreaming of the stem canal eliminated distal tip loading, but proximal stress shielding was still unavoidable. These data show bone loading and interface fixation trends emanating from valgus and varus implant positions that will be of interest to practicing physicians.

How do alternative bearing surfaces influence wear behavior?

Metal, ceramic, and polyethylene liners represent contemporary bearing choices for total joint replacement. Each has limitations in terms of design, sensitivity to manufacturing, and surgical placement. With polyethylene, larger femoral heads represent a design restriction and a potential wear issue. One side benefit is that polyethylene does not click, squeak, or create stripe wear. The attraction of hard-on-hard bearings (metal-on-metal, ceramic-on-ceramic) is that their typically ultra-low wear alleviates concerns with large femoral head designs. However, hard-on-hard bearings produce stripe wear due to the effects of the rigid liner edge. Slight subluxation (microseparation) during swing phase of gait can result in stripe wear on the ball and liner rim. In addition, high levels of implant wear with vertically placed cups can be anticipated. Currently, only alumina-on-alumina bearings can claim virtually no biologic risk. Thus, the role of laboratory studies is to isolate relevant aspects of performance by cup design and to predict the risk-benefit ratios in patients requiring total hip replacement.

Bearings of the future for total hip arthroplasty.

In the last decade or so, newer hip bearings such as ceramic-on-ceramic, metal-on-metal, and metal-on-highly cross-linked polyethylene were introduced into clinical practice in attempts to reduce the debris load released to the tissues after total hip arthroplasty. Present clinical evidence suggests that these newer bearings reduce both abrasive wear and the incidence of osteolysis at up to 10 years clinical follow-up. As further efforts to reduce abrasive wear may meet decreasing returns, we suggest that other bearing issues remain unresolved. These include mechanical failure, impingement or joint laxity, bearing noise, and stress shielding of supporting structures. We present a brief review of the current status of bearing technology and summarize potential areas for further research.

Ceramic-on-ceramic total hip arthroplasty: update.

This prospective, randomized, multicenter study of alumina ceramic-on-alumina ceramic bearing couples includes 452 patients (475 hips). Their average age was 53 years with approximately two thirds men and 82% with osteoarthritis. At an average 8-year follow-up, clinical results were excellent and cortical erosions significantly less than in the conventional polyethylene-on-metal bearing group. Nine hips have undergone revision of one or both components for any reason. Of the 380 ceramic liners, 2 (0.5%) have fractured requiring reoperation, and 3 (0.8%) ceramic patients reported a transient squeaking sound, one of which had a head and liner change due to groin pain secondary to psoas tendinitis at 5 years. With no revisions for aseptic loosening and minimal cortical erosions, alumina-ceramic bearing couples are performing in a manner superior to the polyethylene-on-metal bearing in this young, active patient population.