Food resource richness increases seed disperser visitations and seed rain richness.

Within the context of global change, seed dispersal research often focuses on changes in disperser communities (i.e., seed dispersers, such as birds, in an area) resulting from habitat fragmentation. This approach may not be completely illustrative due to certain seed disperser communities being more robust to fragmentation. Additionally, this top-down approach overlooks how changing food resources on landscapes impacts resource tracking and, subsequently, seed dispersal. We hypothesized resource tracking may promote diffuse plant-animal dispersal mutualisms if resource richness is positively linked to disperser and seed rain richness. We predicted increasing food resource richness attracts more visits and species of avian dispersers, resulting in higher counts and greater species richness of seeds deposited at sites (i.e., seed rain). We tested this mechanism in two replicated field experiments using a model system with bird feeders positioned above seed traps. In the first experiment, we demonstrated resource presence skews seed rain. In the second experiment, we explored how species richness of food resources (0, 4, 8, or 12 species) affected the species richness and visitation of avian seed dispersers at feeders and in subsequent seed rain. Collectively, we observed a positive relationship between available food resources and seed rain, likely mediated by resource tracking behavior of avian dispersers. Our findings underscore a potential key mechanism that may facilitate ecological diversity, whereby accumulating species richness in the plant community attracts a more diverse seed disperser community and indirectly promotes more species in seed rain. Importantly, the resource tracking mechanism driving this potential positive feedback loop may also result in negative ecosystem effects if global change diminishes resource availability through homogenization processes, such as invasive species colonization. Future research should explore the bottom-up effects of global change on food resources and seed disperser behavior to complement the literature on changing disperser communities.

The Spatial Ecology of Nuisance Crocodiles: Movement Patterns of Relocated American Crocodiles (Crocodylus acutus) in Guanacaste, Costa Rica.

Anthropogenic alterations of the environment have increased, highlighting the need for human-wildlife coexistence and conflict mitigation. Spatial ecology, and the use of passive satellite movement technology in particular, has been used to identify patterns in human-wildlife conflict as a function of shared resources that present potential for dangerous situations. Here, we aim to remotely identify patterns indicative of human-crocodile conflict in Guanacaste, Costa Rica by exploring site fidelity and diverse modes of movement (i.e., land and water) across space between nuisance (relocated) and non-nuisance (wild) crocodiles. Advanced satellite remote sensing technology provided near-constant movement data on individuals at the regional scale. Telonics Iridium SeaTrkr-4370-4 transmitters were used with modified crocodilian fitting. Results indicate that relocated crocodiles exhibited large-scale movements relative to wild crocodiles. Nuisance relocated crocodiles either returned to the area of nuisance or potentially attempted to in short time frames. The results presented here highlight the need for alternative management strategies that facilitate relocation efficacy.

Development, Validation, and Implementation of a Guideline to Improve Clinical Event Debriefing at a Level-I Adult and Level-II Pediatric Trauma Center.

OBJECTIVE: Clinical event debriefing is recommended by the American Heart Association and the European Resuscitation Council, because debriefings improve team performance. The purpose here was to develop and validate tools needed to overcome barriers to debriefing in the emergency department. METHOD: This quality improvement project was conducted in 4 phases. Phase 1: Current evidence related to debriefing in the emergency department was reviewed and synthesized to inform an iterative process for drafting the debriefing guideline and instrument for documentation. Phase 2: Content Validity Index of the tools was evaluated by obtaining ratings of items' clarity and relevance from 5 national experts in 2 rounds of review. On the basis of experts' feedback, tools were revised, and a Facilitators' Guide was created. Phase 3: The validated debriefing tools were implemented. Phase 4: Debriefing facilitators completed a survey about their experience with using the new tools. RESULTS: The Content Validity Index of 71 debriefing tool items (guideline, instrument, Facilitators' Guide) was 0.93 and 0.96 for clarity and relevance, respectively. Of the 32 debriefings conducted during the first 8 weeks of implementation, 53% described patient safety concerns, and 97% described recommendations to improve performance. Most (94%) facilitators agreed that the guideline clarified debriefing requirements. CONCLUSION: The use of debriefing tools validated by computation of the Content Validity Index led to the identification of safety threats and recommendations to improve care processes. These tools can be used in ED settings to promote team learning and aid in identifying and resolving safety concerns.

Total Knee Arthroplasty After Anterior Cruciate Ligament Reconstruction: Not Just a Routine Primary Arthroplasty.

BACKGROUND: Despite the success of restoring joint stability and improving early functional outcomes after anterior cruciate ligament (ACL) reconstruction, the long-term risk of developing symptomatic osteoarthritis requiring total knee arthroplasty is higher than that in the uninjured population. The purpose of this study was to compare operative characteristics and early outcomes of patients undergoing total knee arthroplasty after ACL reconstruction with those of a matched cohort of control subjects with primary osteoarthritis and no history of ligament reconstruction. METHODS: All patients who had undergone total knee arthroplasty from 2005 to 2013 at our institution with a history of ACL reconstruction and a minimum 2-year follow-up were identified from a prospective research database. These patients were matched by demographic and surgeon variables to patients who had not undergone prior ACL reconstruction. Outcomes included Knee Society Scores (KSS), range of motion, operative variables, complications, and reoperations. RESULTS: A cohort of 122 patients was identified as the ACL study group and was compared with the matched control cohort. The mean age at the time of the surgical procedure was 58 years, and 55% of the patients were male. The mean follow-up was 3.3 years in the ACL group and 3.0 years in the control group. There was no significant difference in the latest KSS outcomes between groups postoperatively (p > 0.05). Although preoperative flexion was significantly lower (p = 0.01) in the ACL group (119°) than in the control group (123°), there was no difference between groups postoperatively. Fifty percent (61 of 122) of patients in the ACL group required implant removal at the time of total knee arthroplasty. The operative time was significantly longer (p < 0.001) in the ACL group (88 minutes) compared with the control group (73 minutes). There were a total of 11 reoperations in the ACL group, including 4 for periprosthetic infection, whereas there were only 2 reoperations in the control group. The risk of reoperation in the ACL group was more than 5 times higher than in the control group (relative risk, 5.5 [95% confidence interval, 1.2 to 24.3]; p = 0.01). CONCLUSIONS: The results of this retrospective matched cohort study suggest that prior ACL reconstruction results in longer operative time and increased risk of early reoperation after total knee arthroplasty. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

What Preoperative Radiographic Parameters Are Associated With Increased Medial Release in Total Knee Arthroplasty?

BACKGROUND: Preoperative varus deformity of the knee is a common malalignment in patients undergoing primary total knee arthroplasty (TKA). We are unaware of any studies that have correlated how various preoperative radiographic parameters can predict the amount of medial releases performed to achieve optimal coronal alignment and ligamentous balance. METHODS: A retrospective review was performed on 67 patients who required at least a medial tibial reduction osteotomy (MTRO) during primary TKA to achieve coronal balance. This patient population was matched 1:1 to another cohort of TKA patients by age, gender, and body mass index who did not require an MTRO. A radiographic evaluation was used to compare the 2 cohorts. RESULTS: Preoperatively, the MTRO cohort was noted to have significantly increased varus tibiofemoral (86.12° vs 93.43°), tibial articular surface (85.79° vs 87.54°), and medial tibial articular surface angles (75.22° vs 85.34°) compared to the control cohort. The MTRO cohort had 3.13 mm of medial tibial offset and 9.06 mm of lateral joint space opening and the control cohort had 0.09 mm and 4.07 mm, respectively. The medial tibial articular surface angle and lateral joint space widening were statistically associated with the MTRO cohort. The final tibiofemoral angle in the MTRO cohort was 92.43° and was 93.40° in the control cohort. CONCLUSION: The MTRO cohort was noted to have several preoperative radiographic parameters that were significantly different than the control cohort. However, the medial tibial articular surface angle and lateral joint space widening were the only radiographic parameters that were statistically associated with requiring an MTRO.

Elucidating the interplay between IgG-Fc valency and FcγR activation for the design of immune complex inhibitors.

Autoantibody immune complex (IC) activation of Fcγ receptors (FcγRs) is a common pathogenic hallmark of multiple autoimmune diseases. Given that the IC structural features that elicit FcγR activation are poorly understood and the FcγR system is highly complex, few therapeutics can directly block these processes without inadvertently activating the FcγR system. To address these issues, the structure activity relationships of an engineered panel of multivalent Fc constructs were evaluated using sensitive FcγR binding and signaling cellular assays. These studies identified an Fc valency with avid binding to FcγRs but without activation of immune cell effector functions. These observations directed the design of a potent trivalent immunoglobulin G-Fc molecule that broadly inhibited IC-driven processes in a variety of immune cells expressing FcγRs. The Fc trimer, Fc3Y, was highly efficacious in three different animal models of autoimmune diseases. This recombinant molecule may represent an effective therapeutic candidate for FcγR-mediated autoimmune diseases.

Metal Hypersensitivity and Total Knee Arthroplasty.

Metal hypersensitivity in patients with a total knee arthroplasty (TKA) is a controversial topic. The diagnosis is difficult, given the lack of robust clinical validation of the utility of cutaneous and in vitro testing. Metal hypersensitivity after TKA is quite rare and should be considered after eliminating other causes of pain and swelling, such as low-grade infection, instability, component loosening or malrotation, referred pain, and chronic regional pain syndrome. Anecdotal observations suggest that two clinical presentations of metal hypersensitivity may occur after TKA: dermatitis or a persistent painful synovitis of the knee. Patients may or may not have a history of intolerance to metal jewelry. Laboratory studies, including erythrocyte sedimentation rate, C-reactive protein level, and knee joint aspiration, are usually negative. Cutaneous and in vitro testing have been reported to be positive, but the sensitivity and specificity of such testing has not been defined. Some reports suggest that, if metal hypersensitivity is suspected and nonsurgical measures have failed, then revision to components fabricated of titanium alloy or zirconium coating can be successful in relieving symptoms. Revision should be considered as a last resort, however, and patients should be informed that no evidence-based medicine is available to guide the management of these conditions, particularly for decisions regarding revision. Given the limitations of current testing methods, the widespread screening of patients for metal allergies before TKA is not warranted.

Medial tibial "spackling" to lessen chronic medial tibial soft tissue irritation.

We describe a unique, utilitarian reconstructive treatment option known as tibial "spackling" for chronic, localized medial joint line pain corresponding with progressive radiographic peripheral medial tibial bone loss beneath a well-fixed revision total knee arthroplasty tibial baseplate. It is believed that this localized pain is due to chronic irritation of the medial capsule and collateral ligament from the prominent medial edge of the tibial component. In the setting of failed nonoperative treatment, our experience with utilizing bone cement to reconstruct the medial tibial bone defect and create a smooth medial tibial surface has been successful in eliminating chronic medial soft tissue irritation.

Controlled tetra-Fc sialylation of IVIg results in a drug candidate with consistent enhanced anti-inflammatory activity.

Despite the beneficial therapeutic effects of intravenous immunoglobulin (IVIg) in inflammatory diseases, consistent therapeutic efficacy and potency remain major limitations for patients and physicians using IVIg. These limitations have stimulated a desire to generate therapeutic alternatives that could leverage the broad mechanisms of action of IVIg while improving therapeutic consistency and potency. The identification of the important anti-inflammatory role of fragment crystallizable domain (Fc) sialylation has presented an opportunity to develop more potent Ig therapies. However, translating this concept to potent anti-inflammatory therapeutics has been hampered by the difficulty of generating suitable sialylated products for clinical use. Therefore, we set out to develop the first, to our knowledge, robust and scalable process for generating a well-qualified sialylated IVIg drug candidate with maximum Fc sialylation devoid of unwanted alterations to the IVIg mixture. Here, we describe a controlled enzymatic, scalable process to produce a tetra-Fc-sialylated (s4-IVIg) IVIg drug candidate and its qualification across a wide panel of analytic assays, including physicochemical, pharmacokinetic, biodistribution, and in vivo animal models of inflammation. Our in vivo characterization of this drug candidate revealed consistent, enhanced anti-inflammatory activity up to 10-fold higher than IVIg across different animal models. To our knowledge, this candidate represents the first s4-IVIg suitable for clinical use; it is also a valuable therapeutic alternative with more consistent and potent anti-inflammatory activity.

Arthroplasty in organ transplant patients.

The number of solid organ transplants performed in the United States continues to increase annually as does survival after transplant. These unique patients are increasingly likely to present to arthroplasty surgeons for elective hip or knee replacement secondary to a vascular necrosis from chronic immunosuppression, or even age-related development of osteoarthritis. Transplant recipients have a well-documented increased risk of complications but also excellent pain relief and dramatic improvement in quality of life. A multidisciplinary approach with the assistance of the medical transplant services for risk stratification and perioperative medical optimization is necessary. Prior solid organ transplant is not a contraindication to surgery; however, it is the responsibility of the surgeon to educate patients about the relative risks and benefits of prior to surgery.

Neuregulin 1 expression is a predictive biomarker for response to AV-203, an ERBB3 inhibitory antibody, in human tumor models.

PURPOSE: ERBB3 is overexpressed in a broad spectrum of human cancers, and its aberrant activation is associated with tumor pathogenesis and therapeutic resistance to various anticancer agents. Neuregulin 1 (NRG1) is the predominant ligand for ERBB3 and can promote the heterodimerization of ERBB3 with other ERBB family members, resulting in activation of multiple intracellular signaling pathways. AV-203 is a humanized IgG1/κ ERBB3 inhibitory antibody that completed a first-in-human phase I clinical trial in patients with advanced solid tumors. The purpose of this preclinical study was to identify potential biomarker(s) that may predict response to AV-203 treatment in the clinic. EXPERIMENTAL DESIGN: We conducted in vivo efficacy studies using a broad panel of xenograft models representing a wide variety of human cancers. To identify biomarkers that can predict response to AV-203, the relationship between tumor growth inhibition (TGI) by AV-203 and the expression levels of ERBB3 and NRG1 were evaluated in these tumor models. RESULTS: A significant correlation was observed between the levels of NRG1 expression and TGI by AV-203. In contrast, TGI was not correlated with ERBB3 expression. The correlation between the levels of NRG1 expression in tumors and their response to ERBB3 inhibition by AV-203 was further validated using patient-derived tumor explant models. CONCLUSIONS: NRG1 is a promising biomarker that can predict response to ERBB3 inhibition by AV-203 in preclinical human cancer models. NRG1 warrants further clinical evaluation and validation as a potential predictive biomarker of response to AV-203.

Anatomic findings and complications after surgical treatment of chronic, partial distal biceps tendon tears: a case cohort comparison study.

PURPOSE: To describe pertinent anatomic findings during repair of chronic, partial distal biceps tendon tears and to compare the complications of surgery with a similar cohort of acute, complete tears. METHODS: Group 1 included 14 patients (15 elbows) with partial tears managed operatively an average of 10 months from onset of injury or symptoms. Group 2 included a matched cohort of 16 patients (17 elbows) treated for complete, acute tears an average of 19 days from injury. A retrospective review of all 30 patients focused on demographic data, intraoperative findings, and postoperative complications. A single, anterior incision was used in all cases with multiple suture anchors or a bicortical toggling button for fixation of the repair. RESULTS: We evaluated 27 men and 3 women with an average age of 55 years (group 1) and 48 years (group 2). Intratendinous ganglion formation at the site of rupture of the degenerative tendon was observed in 5 cases of partial tears and none of the complete tears. Partial tears involved the lateral aspect or short head of the biceps tendon insertion in all cases. Postoperative complications included lateral antebrachial cutaneous nerve neuritis in 8 group 1 patients and 6 group 2 patients and transient posterior interosseus nerve palsy in 3 group 1 patients. CONCLUSIONS: Partial distal biceps tendon ruptures showed a consistent pattern of pathology involving disruption of the lateral side of the tendon insertion involving the small head of the biceps. Degenerative intratendinous ganglion formation was present in one third of cases. Repair of chronic, partial distal biceps tendon injuries may have a higher incidence of posterior interosseous and lateral antebrachial cutaneous nerve palsies. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic III.

Risk versus reward: total joint arthroplasty outcomes after various solid organ transplantations.

Clinical outcomes were retrospectively reviewed for 76 primary total hip (THA) and total knee arthroplasties (TKA) performed after kidney, liver, cardiac, and lung transplantation with follow-up of 30.2 and 41.2 months, respectively. For the THA and TKA cohorts, there were a high rate of medical complications (29% and 33%), increased hospital length of stay (4.2 and 3.7 days), and more reoperations (7.2% and 9.1%). Only 1 (1.8%) periprosthetic infection was documented for THAs but 3 (14.2%) TKAs required two-stage revisions for infection. All transplant cohorts demonstrated significant increases (P < 0.05) in HHS and KSS scores with majority of patients reporting overall good or excellent outcomes (82%-100%). These results suggest that various organ transplant patients may accept higher surgical risks for rewarding outcomes.

Impact of perioperative allogeneic and autologous blood transfusion on acute wound infection following total knee and total hip arthroplasty.

BACKGROUND: Patients undergoing total hip or knee arthroplasty frequently receive blood transfusions. The relationship between transfusion and the risk of infection following total joint arthroplasty is unclear. In this study, we sought to examine the impact of allogeneic and autologous transfusion on the risk of acute infection following total hip and total knee arthroplasty. METHODS: We performed a retrospective study of consecutive primary total knee arthroplasties and total hip arthroplasties. Patients who had a reoperation for suspected infection within three months after the arthroplasty were identified. Differences in risk factors were assessed across transfusion groups: no transfusion, autologous only, and allogeneic exposure (allogeneic with or without additional autologous transfusion). Backward-stepwise logistic regression analysis was used to compare reoperations (as outcomes) between cases with and those without allogeneic exposure. Prespecified covariates were body mass index, diabetes, an American Society of Anesthesiologists (ASA) score of >2, preoperative hematocrit, and total number of units transfused perioperatively. RESULTS: We identified 3352 patients treated with a total hip or knee arthroplasty (1730 total knee arthroplasties and 1622 total hip arthroplasties) for inclusion in the study. Transfusion was given in 1746 cases: 836 of them had allogeneic exposure, and 910 had autologous-only transfusion. There were thirty-two reoperations (0.95%) for suspected infection. Between-group risk-factor differences were observed. The mean age and the rates of diabetes, immunosuppression, ASA scores of >2, and bilateral surgery were highest in the allogeneic group, as were estimated blood loss, surgery duration, and total number of units transfused (p < 0.001). In the unadjusted analyses, the rate of reoperations for suspected infection was higher in the cases with allogeneic exposure (1.67%) than in those without allogeneic exposure (0.72%) (p = 0.013). Autologous-only transfusion was not associated with a higher reoperation rate. However, multivariable logistic regression demonstrated that the total number of units transfused (p = 0.011) and an ASA score of >2 (p = 0.008)-but not allogeneic exposure-were significantly predictive of a reoperation. CONCLUSIONS: Perioperative allogeneic transfusion was associated with a higher rate of reoperations for suspected acute infection. However, patients with allogeneic exposure had increased infection risk factors. After adjustment for the total number of units transfused and an ASA score of >2, allogeneic exposure was not significantly predictive of a reoperation for infection.

Economic evaluation of access to musculoskeletal care: the case of waiting for total knee arthroplasty.

BACKGROUND: The projected demand for total knee arthroplasty is staggering. At its root, the solution involves increasing supply or decreasing demand. Other developed nations have used rationing and wait times to distribute this service. However, economic impact and cost-effectiveness of waiting for TKA is unknown. METHODS: A Markov decision model was constructed for a cost-utility analysis of three treatment strategies for end-stage knee osteoarthritis: 1) TKA without delay, 2) a waiting period with no non-operative treatment and 3) a non-operative treatment bridge during that waiting period in a cohort of 60 year-old patients. Outcome probabilities and effectiveness were derived from the literature. Costs were estimated from the societal perspective with national average Medicare reimbursement. Effectiveness was expressed in quality-adjusted life years (QALYs) gained. Principal outcome measures were average incremental costs, effectiveness, and quality-adjusted life years; and net health benefits. RESULTS: In the base case, a 2-year wait-time both with and without a non-operative treatment bridge resulted in a lower number of average QALYs gained (11.57 (no bridge) and 11.95 (bridge) vs. 12.14 (no delay). The average cost was $1,660 higher for TKA without delay than wait-time with no bridge, but $1,810 less than wait-time with non-operative bridge. The incremental cost-effectiveness ratio comparing wait-time with no bridge to TKA without delay was $2,901/QALY. When comparing TKA without delay to waiting with non-operative bridge, TKA without delay produced greater utility at a lower cost to society. CONCLUSIONS: TKA without delay is the preferred cost-effective treatment strategy when compared to a waiting for TKA without non-operative bridge. TKA without delay is cost saving when a non-operative bridge is used during the waiting period. As it is unlikely that patients waiting for TKA would not receive non-operative treatment, TKA without delay may be an overall cost-saving health care delivery strategy. Policies aimed at increasing the supply of TKA should be considered as savings exist that could indirectly fund those strategies.

Outcomes of primary total joint arthroplasty after lung transplantation.

Lung transplantation is increasingly common with improving survival rates. Post-transplant patients can be expected to seek total hip (THA) and knee arthroplasty (TKA) to improve their quality of life. Outcomes of 20 primary total joint arthroplasties (15 THA, 5 TKA) in 14 patients with lung transplantation were reviewed. Clinical follow-up time averaged 27.5 and 42.8 months for THA and TKA respectively. Arthroplasty indications included osteonecrosis, osteoarthritis, and fracture. All patients subjectively reported good or excellent outcomes with a final average Harris Hip Score of 88.7, Knee Society objective and functional score of 92.0. There were 4 minor and 1 major acute perioperative complications. 1 late TKA infection was successfully treated with two-stage revision. The mortality rate was 28.5% (4/14 patients) at an average 20.6 months following but unrelated to arthroplasty. Overall, total joint arthroplasty can be safely performed and provide good functional outcomes in lung transplant recipients.

Fixation versus replacement of radial head in terrible triad: is there a difference in elbow stability and prognosis?

BACKGROUND: Surgical treatment for terrible triad injuries of the elbow (defined as elbow dislocations with concomitant fractures of the radial head and coronoid) remains a challenging clinical problem. Specifically, the question of whether to repair or replace the radial head remains controversial. QUESTIONS/PURPOSES: We compared patients with terrible triad injuries of the elbow whose radial head fracture was treated with either internal fixation and internal fixation (ORIF) or radial head arthroplasty in terms of (1) clinical outcome measures (DASH and Broberg-Morrey scores, ROM), (2) elbow stability and radiographic signs of arthrosis, and (3) complications and reoperation rates. METHODS: Retrospective review identified 39 patients with terrible triad injuries and minimum 18-month complete clinical and radiographic followup (mean, 24 months; range, 18-53 months). Patients were managed with a standard algorithm consisting of (1) repair (n = 9) or replacement (n = 30) of the radial head, (2) repair of the lateral ulnar collateral ligament, and (3) repair of the coronoid fracture. During the study period, the radial head generally was internally fixed when there were fewer than four articular fragments; otherwise, it was replaced. Evaluation included the DASH score, the Broberg-Morrey index, measurements of elbow stability and motion, and radiographic assessment for signs of arthrosis; chart review was performed for complications and reoperations. Complete followup was available on 87% (39 of 45 patients). RESULTS: There were no differences between groups in terms of ROM or elbow scores. All patients who underwent radial head arthroplasty at the index procedure had a stable elbow at final followup whereas three of nine patients who underwent ORIF were unstable (p = 0.009). However, 11 patients who underwent arthroplasty demonstrated radiographic signs of arthrosis compared to none in the ORIF group (p = 0.04). Eleven patients (28%) underwent reoperation (seven arthroplasty, four ORIF) for various reasons. With the numbers available, there was no difference in reoperation rate between groups (p = 0.45). CONCLUSIONS: For terrible triad injuries, radial head arthroplasty afforded the ability to obtain elbow stability with comparable overall outcomes when compared to ORIF. As these injuries commonly occur in younger patients, longer-term studies will be required to ascertain whether the apparent benefits of radial head arthroplasty are offset by late complications of arthroplasty, such as loosening. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

Unicompartmental knee arthroplasty and total knee arthroplasty among Medicare beneficiaries, 2000 to 2009.

BACKGROUND: Unicompartmental knee arthroplasty is a less-invasive alternative to total knee arthroplasty for patients with arthritis affecting only the medial or lateral compartment. However, little is known about recent trends in the use of these procedures and the associated outcomes among older patients. METHODS: With use of a nationally representative 5% sample of Medicare beneficiaries who were sixty-five years of age or older and who had undergone either unilateral unicompartmental knee arthroplasty or unilateral total knee arthroplasty from 2000 to 2009, we assessed trends in the use of unicompartmental and total knee arthroplasty, associated durations of hospital stay, and postoperative outcomes. The outcome measures were the rates of implant revision or removal within five years and the rates of periprosthetic infection, thromboembolic events, myocardial infarction, and all-cause mortality within one year. We conducted Kaplan-Meier analyses to assess the cumulative incidence of unadjusted outcomes and used Cox proportional-hazards regression to understand the relative risks of the outcomes for each procedure. RESULTS: A total of 68,603 patients underwent unilateral total knee arthroplasty (n = 65,505) or unilateral unicompartmental knee arthroplasty (n = 3098) from 2000 to 2009. The mean age was seventy-five years; 34% of the patients were men, and 92% were white. The procedure rate was twenty-one times higher for total knee arthroplasty (597 per 100,000 person-years) than unicompartmental knee arthroplasty (twenty-nine per 100,000 person-years). The use of total knee arthroplasty increased 1.7-fold, and the use of unicompartmental knee arthroplasty increased 6.2-fold. The mean length of stay (and standard deviation [SD]) was 3.9 ± 2.1 days for total knee arthroplasty and 2.4 ± 1.7 days for unicompartmental knee arthroplasty. The five-year revision rate was 3.7% for total knee arthroplasty and 8.0% for unicompartmental knee arthroplasty. After multivariable adjustment, the risk of revision remained 2.4 times higher for unicompartmental knee arthroplasty than for total knee arthroplasty (95% confidence interval [CI] = 2.03 to 2.83). After multivariable adjustment, patients who underwent unicompartmental knee arthroplasty had no significant differential one-year risk of infection (adjusted hazard ratio [HR] = 0.74; 95% CI = 0.55 to 1.01), thromboembolic events (adjusted HR =0.86; 95% CI = 0.57 to 1.29), or mortality (adjusted HR = 0.75; 95% CI = 0.50 to 1.11). CONCLUSIONS: Although unicompartmental knee arthroplasty accounted for only 4.5% of the unilateral knee replacements among Medicare beneficiaries, the use of this procedure has increased dramatically. Compared with those who had total knee arthroplasty, patients who underwent unicompartmental knee arthroplasty had higher revision rates but shorter durations of stay and tended to have lower rates of perioperative complications. These findings need to be confirmed by studies that incorporate detailed clinical information.

Simultaneous vs staged bilateral total knee arthroplasty among Medicare beneficiaries, 2000-2009.

Simultaneous bilateral total knee arthroplasty (TKA) reportedly has higher postoperative complication rates than staged procedures, but little is known about recent trends and outcomes among Medicare patients. In a 5% national sample of Medicare beneficiaries older than 65 years, we identified 83,441 patients who underwent elective TKA between 2000 and 2009 and compared patients undergoing simultaneous bilateral TKA (n=4519) to staged TKA (n=3788). Use of simultaneous TKA did not change over time (3 in 10,000), but use of staged TKA increased three-fold from 1.4 to 4.4 in 10,000 person-years. We assessed length of stay; 5-year risk of revision; periprocedural (i.e., 90-day) risk of infection; hospitalization for venous thromboembolism (VTE) and myocardial infarction (MI); and death using Kaplan-Meier methods. Simultaneous TKA had higher 90-day risk of death (0.7% vs. 0.3%, P=0.02), VTE (0.9% vs. 0.5%, P=0.07), and MI (0.5% vs. 0.2%, P=0.02). Infection and revision rates were similar between the two groups.

Radiographic outcomes of ring external fixation for malunion and nonunion.

Ring external fixators such as the Ilizarov external fixator (IEF) and Taylor Spatial Frame (TSF) have revolutionized management of limb deformity. This study examines radiographic outcomes for treatment of malunions and nonunions with secondary emphasis on comparing radiographic union rates of TSF and IEF. A retrospective chart and radiograph review was performed. Fifty-four patients were included. Most injuries were in the tibia (96%). Fifty patients (93%) achieved radiographic union, two patients required further fixation, and two patients elected to undergo amputation. The preoperative coronal deformity improved from a mean of 12° (range, 0°-41°) to within 3° anatomic. Sagittal deformity improved from a mean of 11° (range, 0°-49°) to within 5° anatomic with some patients intentionally left in recurvatum to accommodate plantarflexion contractures. Limb length discrepancies were corrected to within 1 cm. Twenty-five patients experienced complications (mostly superficial pin tract infections). No statistically significant differences in the radiographic outcomes of TSF compared to IEF were identified.