Arlen D Hanssen

Mayo Clinic - Rochester, Рочестер, Minnesota, United States

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Publications (273)913.86 Total impact

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    ABSTRACT: Background: Periprosthetic infections are devastating for patients and more efficacious preventive strategies are needed. Surface-modified implants using antibacterial coatings represent an option to cope with this problem; however, manufacturing limitations and cytotoxicity have curbed clinical translation. Among metals with antibacterial properties, copper has shown superior in vitro antibacterial performance while maintaining an acceptable cytotoxicity profile. A thin film containing copper could prevent early biofilm formation to limit periprosthetic infections. This pilot study presents the in vitro antibacterial effect, cytotoxicity, and copper ion elution pattern of a thin film of titanium-copper oxide (TiCuO). Questions/purposes: (1) Do titanium alloy (Ti6Al4V) discs coated with a thin film of TiCuO reduce Staphylococcus epidermidis biofilm and planktonic cell density compared with uncoated discs? (2) Do Ti6Al4V discs coated with a thin film of TiCuO affect normal human osteoblast viability compared with untreated cells? (3) Is copper ion concentration generated by coated discs lower than previously published copper ion concentrations that cause 50% toxicity in similar human cell lines in vitro (TC50)? Methods: Ninety Ti6Al4V discs (12.5 mm diameter; 1.25 mm thick) were used in this study. Seventy-two Ti6Al4V discs were coated with a thin film of either titanium oxide (TiO) or TiCuO containing 20%, 40%, or 80% copper using high-power impulse magnetron sputtering (HiPIMS). Eighteen Ti6Al4V discs remained uncoated for control purposes. We tested antibacterial properties of S epidermidis grown on discs in wells containing growth medium. After 24 hours, planktonic bacteria as well as biofilms removed by sonication were quantitatively cultured. Annexin/Pi staining was used to quantify in vitro normal human osteoblast cell viability at 24 hours and Day 7, respectively. Copper elution was measured at Days 1, 2, 3, 7, 14, and 28 using an inductively coupled plasma mass spectrometer to analyze aliquots of culture medium. Copper ion concentration achieved at 24 hours was compared with previously published TC50 for gingival fibroblast, a phenotypically similar cell line with available data regarding copper ion exposure. Results: Discs coated with TiCuO 80% copper showed greater biofilm and planktonic cell density reduction when compared with other tested compositions (analysis of variance [ANOVA]; p < 0.001). Discs coated with TiCuO 80% copper showed mean biofilm and planktonic cell density of 4.0 log10 (SD = 0.4) and 5.7 log10 (SD = 0.2). Discs coated with TiCuO 80% showed a mean difference in biofilm and planktonic cell density of 2.5 log10 (95% confidence interval [CI], 1.9-3.1 log10; p < 0.001) and 1.2 (95% CI, 0.6-1.8; p < 0.001), respectively, when compared with uncoated discs. Normal human osteoblast viability did not differ among all groups at 24 hours (ANOVA; p = 0.2) and Day 7 (ANOVA; p = 0.7). Discs coated with TiCuO 80% copper showed a mean difference (95% CI) in relative cell viability (%) at 24 hours and Day 7 of 31.1 (95% CI, -19.4 to 81.7; p = 0.4) and -5.0 (95% CI, -7.8 to 17.9; p = 0.9), respectively, when compared with untreated cells. For all TiCuO-coated discs, copper ion elution peaked at 24 hours and slowly decreased in a curvilinear fashion to nearly undetectable levels by Day 28. Discs coated with TiCuO 80% copper showed mean copper ion concentration at 24 hours of 269.4 µmol/L (SD = 25.2 µmol/L) and this concentration was lower than previously published TC50 for similar human cell lines at 24 hours (344 µmol/L, SEM = 44 µmol/L). Conclusions: This pilot study demonstrates a proof of concept that a thin-film implant coating with TiCuO can provide a potent local antibacterial environment while remaining relatively nontoxic to a human osteoblast cell line. Further research in an animal model will be necessary to establish efficacy and safety of this technique and whether it might be useful in the design of implants. Clinical relevance: A thin film coating with TiCuO demonstrates high antibacterial activity and low cellular cytotoxicity to human osteoblasts in vitro. Taken together, these properties represent a potential strategy for preventing periprosthetic infection if further work in animal models can confirm these results in vivo.
    No preview · Article · Feb 2016 · Clinical Orthopaedics and Related Research
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    P. K. Sculco · M. P. Abdel · A. D. Hanssen · D. G. Lewallen
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    ABSTRACT: The treatment of bone loss in revision total knee arthroplasty has evolved over the past decade. While the management of small to moderate sized defects has demonstrated good results with a variety of traditional techniques (cement and screws, small metal augments, impaction bone grafting or modular stems), the treatment of severe defects continues to be problematic. The use of a structural allograft has declined in recent years due to an increased failure rate with long-term follow-up and with the introduction of highly porous metal augments that emphasise biological metaphyseal fixation. Recently published midterm results on the use of tantalum cones in patients with severe bone loss has reaffirmed the success of this treatment strategy.
    Preview · Article · Jan 2016 · Bone and Joint Journal
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    ABSTRACT: Quadriceps tendon rupture is an uncommon injury. To date, surgical results have been less than favorable. A novel repair technique that uses Marlex mesh (C R Bard, Murray Hill, New Jersey) has been developed. Use of this repair may allow earlier range of motion and functional restoration of extension. The authors sought to evaluate the technical feasibility, durability, and postoperative function of this repair. This study retrospectively analyzed 8 knees (7 patients) operated on with this technique from 1990 to 2011. Mean follow-up was 9 years. Average age at the time of injury was 69 years. Mean operative time was 130 minutes. No perioperative complications occurred, no patients had clinical evidence of failure, and no patients required subsequent reoperation. Mean flexion at final follow-up was 100°. Of the 8 knees, 7 knees had no extensor lag at final follow-up. Marlex mesh augmentation for quadriceps tendon ruptures has promising clinical results, despite significant comorbidities. The results showed that the technique was feasible, with low cost and reasonable operative time. The clinical results were durable, with no intraoperative complications, no re-ruptures, rare extension lag, and good range of motion. Therefore, synthetic mesh augmentation is a feasible option in acute quadriceps tendon ruptures. [Orthopedics].
    Preview · Article · Dec 2015 · Orthopedics
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    ABSTRACT: We evaluated a genus-/group-specific polymerase chain reaction (PCR) assay panel on 284 prosthetic knee synovial fluid samples collected from patients presenting to our institution with implant failure. Using the Musculoskeletal Infection Society diagnostic criteria, 88 and 196 were classified as having PJI and aseptic failure (AF), respectively. Sensitivities of the synovial fluid PCR panel and culture were 55.6% and 76.1% ( p -value ≤0.001), and specificities were 91.8% and 97.4% (p=0.016), respectively. Among the 70 subjects who had received antibiotics within the month preceding synovial fluid aspiration (48 of whom had PJI), PCR panel and synovial fluid culture sensitivities were 64.5% and 85.4%, respectively, p
    No preview · Article · Nov 2015 · Journal of clinical microbiology
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    ABSTRACT: Background: The purpose of this study was to calculate the cumulative risk of periprosthetic joint infection (PJI) after aseptic index knee revisions and to identify the surgical, perioperative, and medical comorbidity risk factors associated with deep infection. Methods: We retrospectively reviewed 1802 aseptic index revision total knee arthroplasties performed at our institution from 1970 to 2000. From this cohort, there were 60 reoperations performed for deep infection. Results: The cumulative risk of infection at 1, 5, 10, and 20 years after index revision was 1%, 2.4%, 3.3%, and 5.6%, respectively. Conclusions: Male gender, use of constrained implants, increased operative times, increased Charlson Comorbidity Index, and a history of liver disease were all significantly associated with PJI. The development of cardiovascular disease, endocrine disorders, and renal disease were also associated with PJI.
    No preview · Article · Nov 2015 · The Journal of arthroplasty
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    ABSTRACT: Background: Surgical site infection (SSI) is one of the most challenging and costly complications associated with total joint arthroplasty. Our primary aim in this case-controlled trial was to compare the risk of SSI within a year of surgery for patients undergoing primary total knee arthroplasty (TKA) or total hip arthroplasty (THA) and revision TKA or THA under general anesthesia versus neuraxial anesthesia. Our secondary aim was to determine which patient, anesthetic, and surgical variables influence the risk of SSI. We hypothesized that patients who undergo neuraxial anesthesia may have a lesser risk of SSI compared with those who had a general anesthetic. Methods: We conducted a retrospective, case-control study of patients undergoing primary or revision TKA and THA between January 1, 1998, and December 31, 2008, who subsequently were diagnosed with an SSI. The cases were matched 1:2 with controls based on type of joint replacement (TKA versus THA), type of procedure (primary, bilateral, revision), sex, date of surgery (within 1 year), ASA physical status (I and II versus III, IV, and V), and operative time (<3 vs >3 hours). Results: During the 11-year period, 202 SSIs were identified. Of the infections identified, 115 (57%) occurred within the first 30 days and 87 (43%) occurred between 31 and 365 days. From both univariate and multivariable analyses, no significant association was found between the use of central neuraxial anesthesia and the postoperative infection (univariate odds ratio [OR] = 0.92; 95% confidence interval [CI], 0.63-1.34; P = 0.651; multivariable OR = 1.10; 95% CI, 0.72-1.69; P = 0.664). The use of peripheral nerve block also was not found to influence the risk of postoperative infection (univariate OR = 1.41; 95% CI, 0.84-2.37; P = 0.193; multivariable OR = 1.35; 95% CI, 0.75-2.44; P = 0.312). The factors that were found to be associated with postoperative infection in multivariable analysis included current smoking (OR = 5.10; 95% CI, 2.30-11.33) and higher body mass index (BMI) (OR = 2.68; 95% CI, 1.42-5.06 for BMI ≥ 35 kg/m compared with those with BMI < 25 kg/m). Conclusions: Recent studies using large databases have concluded that the use of neuraxial compared with general anesthesia is associated with a decreased incidence of SSI in patients undergoing total joint arthroplasty. In this retrospective, case-controlled study, we found no difference in the incidence of SSI in patients undergoing total joint arthroplasty under general versus neuraxial anesthesia. We also concluded that the use of peripheral nerve blocks does not influence the incidence of SSI. Increasing BMI and current smoking were found to significantly increase the incidence of SSI in patients undergoing lower extremity total joint arthroplasty.
    No preview · Article · Oct 2015 · Anesthesia and analgesia
  • Umberto Cottino · Matthew P Abdel · Arlen D Hanssen
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    ABSTRACT: Chronic insufficiency of the knee extensor mechanism is a very challenging pathology to treat. An insufficient extensor mechanism negatively affects implant survival and patient outcomes. The causes of insufficiency can be several, and the surgeon has to be prepared to manage them intraoperatively and postoperatively. Various reconstructive techniques have been proposed, but traditional results in patients with a total knee arthroplasty are usually inferior to those patients with native knee joints. It is of primary importance to understand the anatomy, and tailor the correct treatment to the patient.
    No preview · Article · Sep 2015 · Current Reviews in Musculoskeletal Medicine
  • Keith A. Fehring · Arlen D. Hanssen · Matthew P. Abdel
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    ABSTRACT: Complications involving the extensor mechanism have a devastating effect on overall function following a primary or revision total knee arthroplasty. There are intraoperative, postoperative, and patient-related risk factors that can increase the occurrence of this complication. The results of previously described techniques utilizing direct repair, allograft reconstruction, and/or autograft reconstruction have been discouraging. The purpose of this article is to describe a technique utilizing a synthetic mesh for reconstruction of extensor mechanism disruptions after total knee arthroplasty.
    No preview · Article · Aug 2015 · Seminars in Arthroplasty
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    ABSTRACT: Numerous factors influence total hip arthroplasty (THA) stability including surgical approach and soft tissue tension, patient compliance, and component position. One long-held tenet regarding component position is that cup inclination and anteversion of 40° ± 10° and 15° ± 10°, respectively, represent a "safe zone" as defined by Lewinnek that minimizes dislocation after primary THA; however, it is clear that components positioned in this zone can and do dislocate. We sought to determine if these classic radiographic targets for cup inclination and anteversion accurately predicted a safe zone limiting dislocation in a contemporary THA practice. From a cohort of 9784 primary THAs performed between 2003 and 2012 at one institution, we retrospectively identified 206 THAs (2%) that subsequently dislocated. Radiographic parameters including inclination, anteversion, center of rotation, and limb length discrepancy were analyzed. Mean followup was 27 months (range, 0-133 months). The majority (58% [120 of 206]) of dislocated THAs had a socket within the Lewinnek safe zone. Mean cup inclination was 44° ± 8° with 84% within the safe zone for inclination. Mean anteversion was 15° ± 9° with 69% within the safe zone for anteversion. Sixty-five percent of dislocated THAs that were performed through a posterior approach had an acetabular component within the combined acetabular safe zones, whereas this was true for only 33% performed through an anterolateral approach. An acetabular component performed through a posterior approach was three times as likely to be within the combined acetabular safe zones (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.1-1.6) than after an anterolateral approach (OR, 0.4; 95% CI, 0.2-0.7; p < 0.0001). In contrast, acetabular components performed through a posterior approach (OR, 1.6; 95% CI, 1.2-1.9) had an increased risk of dislocation compared with those performed through an anterolateral approach (OR, 0.8; 95% CI, 0.7-0.9; p < 0.0001). The historical target values for cup inclination and anteversion may be useful but should not be considered a safe zone given that the majority of these contemporary THAs that dislocated were within those target values. Stability is likely multifactorial; the ideal cup position for some patients may lie outside the Lewinnek safe zone and more advanced analysis is required to identify the right target in that subgroup. Level III, therapeutic study.
    No preview · Article · Jul 2015 · Clinical Orthopaedics and Related Research
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    ABSTRACT: The purpose of this study was to calculate the risk of revision secondary to aseptic tibial loosening correlated with increased BMI in 5088 primary TKAs. The mean age was 69years, with a mean follow-up of 7years. Fifty-two (1.0%) revision TKAs were performed due to aseptic tibial loosening, with the 15-year risk being 2.7%. Patients with a BMI ≥35kg/m(2) were significantly more likely to undergo revision due to aseptic tibial failure (HR=1.9; P<0.05). Coronal alignment was equivalent between those who did and did not experience tibial loosening. Given that the risk of revision TKA due to aseptic tibial component failure is 2-fold greater in those with a BMI of ≥35kg/m(2), consideration should be given to additional fixation. Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence. Copyright © 2015. Published by Elsevier Inc.
    No preview · Article · Jul 2015 · The Journal of arthroplasty
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    B A McArthur · M P Abdel · M J Taunton · D R Osmon · A D Hanssen
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    ABSTRACT: The aim of our study was to describe the characteristics, treatment, and outcomes of patients with periprosthetic joint infection (PJI) and normal inflammatory markers after total knee arthroplasty (TKA) and total hip arthroplasty (THA). In total 538 TKAs and 414 THAs underwent surgical treatment for PJI and met the inclusion criteria. Pre-operative erythrocyte sedimentation rate (ESR) and C-reactive protein level (CRP) were reviewed to identify the seronegative cohort. An age- and gender-matched cohort was identified from the remaining patients for comparison. Overall, 4% of confirmed infections were seronegative (21 TKA and 17 THA). Of those who underwent pre-operative aspiration, cultures were positive in 76% of TKAs (n = 13) and 64% of THAs (n = 7). Cell count and differential were suggestive of infection in 85% of TKA (n = 11) and all THA aspirates (n = 5). The most common organism was coagulase-negative Staphylococcus. Seronegative infections were associated with a lower aspirate cell count and a lower incidence of Staphylococcus aureus infection. Two-stage revision was performed in 35 cases (95%). At a mean of five years (14 to 162 months) following revision, re-operation for infection occurred in two TKAs, and one THA. From our study we estimate around 4% of patients with PJI may present with normal ESR and CRP. When performed, pre-operative aspirate is useful in delivering a definitive diagnosis. When treated, similar outcomes can be obtained compared with patients with positive serology. Cite this article: Bone Joint J 2015;97-B:939-44. ©2015 The British Editorial Society of Bone & Joint Surgery.
    Full-text · Article · Jul 2015 · Bone and Joint Journal
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    ABSTRACT: Fungal periprosthetic joint infections are rare, devastating complications of arthroplasty. There is conflicting evidence as to the efficacy of amphotericin B elution from cement spacers. The purpose of this study was to determine whether concentrations of amphotericin B released from bone cement over time would be efficacious in treating a periprosthetic infection. A continuous flow chamber was used to evaluate the in vitro release of amphotericin from cement beads containing 7.5% amphotericin. Following polymerization, 3.3% of the initially loaded amphotericin B was detected. The peak mean concentration eluted from the bone cement was 0.33 μg/mL at 8 hours. The AUC0-24 was 2.79 μg/mL/h; 0.20% of the amphotericin B was released. In conclusion, amphotericin B is released from bone cement at a clinically useful concentration. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · Jun 2015 · The Journal of Arthroplasty
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    ABSTRACT: The FilmArray® Blood Culture ID (BCID) panel (BioFire Diagnostics, Inc., Salt Lake City, UT) is a FDA-cleared multiplex PCR panel for pathogen identification from positive blood culture bottles.…. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    No preview · Article · May 2015 · Journal of clinical microbiology
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    ABSTRACT: Total knee arthroplasty (TKA) is highly successful, with an exponential increase expected in the near future [1, 2]. More importantly, a fivefold increase in the number of revision TKAs is expected by 2030 [1, 2]. In the latest studies, the top seven reasons for revision TKA include aseptic loosening (23.1 %), infection (18.4 %), polyethylene wear (18.1 %), instability (17.7 %), pain/stiffness (9.3 %), osteolysis (4.5 %), and malposition/misalignment (2.9 %) [1, 3]. With modern implants, constraint can be effectively managed [4]. However, one of the remaining challenges in revision TKA is the management of severe bone loss [4]. Traditionally, allografts have been widely utilized to manage bone loss, with a significant failure rate at only mid-term follow-up [4]. New techniques with restoration of the metaphysis have been developed to optimize the results of revision TKA [4-8]. In this editorial, it was our aim to present contemporary management solutions for severe bone loss encounter ...
    Full-text · Article · Mar 2015 · European Journal of Orthopaedic Surgery & Traumatology
  • Atul F Kamath · David G Lewallen · Arlen D Hanssen
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    ABSTRACT: Severe metaphyseal and meta-diaphyseal bone loss poses important challenges in revision total knee arthroplasty. The best strategy for addressing massive tibial bone loss has not been determined. The purpose of this study was to assess the intermediate-term clinical and radiographic results of porous tibial cone implantation. Sixty-six porous tantalum tibial cones (sixty-three patients) were reviewed at a mean follow-up time of seventy months (range, sixty to 106 months). According to the Anderson Orthopaedic Research Institute bone defect classification, twenty-four knees had a Type-3 defect, twenty-five knees had a Type-2B defect, and seventeen knees had a Type-2A defect. The mean age at the time of the index revision was sixty-seven years (range, forty-one to eighty-three years), and 57% of patients were female. The mean American Society of Anesthesiologists Physical Status was 2.4 (range, 2 to 3), and the mean body mass index was 33 kg/m(2) (range, 25 to 53 kg/m(2)). Fifteen patients (24%) were on immunosuppressant medications, and eight patients (13%) were current smokers. The patients underwent a mean number of 3.4 prior knee surgical procedures (range, one to twenty procedures), and 49% of patients (thirty-one patients) had a history of periprosthetic infection. The mean Knee Society Scores improved significantly from 55 points preoperatively (range, 4 to 97 points) to 80 points (range, 28 to 100 points) at the time of the latest follow-up (p < 0.0001). One patient had progressive radiolucencies about the tibial stem and cone on radiographs. One patient had complete radiolucencies about the tibial cone, concerning for fibrous ingrowth. Three other cones were revised: one for infection, one for aseptic loosening, and one for periprosthetic fracture. Revision-free survival of the tibial cone component was >95% at the time of the latest follow-up. Porous tantalum tibial cones offer a promising management option for severe tibial bone loss. At the intermediate-term follow-up (five to nine years), porous tantalum tibial cones had durable clinical results and radiographic fixation. The biologic ingrowth of these implants offers the potential for successful long-term structural support in complex knee reconstruction. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence. Copyright © 2015 by The Journal of Bone and Joint Surgery, Incorporated.
    No preview · Article · Feb 2015 · The Journal of Bone and Joint Surgery
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    ABSTRACT: Porous tantalum monoblock cups have been proposed to improve survivorship of cementless primary THA. However, there are few direct comparative trials to established implants such as porous-coated titanium cups. 113 patients were randomized into two groups according to the cup: a porous tantalum monoblock cup (TM) or a porous-coated titanium monoblock cup (control). At a mean of 12 years after THA, no implants migrated in both groups. Two TM patients (4%) and 13 control patients (33%) presented with radiolucency around the cup (P<0.001). In the control group, 1 cup (2%) was revised for aseptic loosening. At 12 years post-implantation, porous tantalum monoblock cups demonstrated 100% survivorship, and significantly less radiolucency as compared to porous-coated titanium monoblock cups. Copyright © 2015 Elsevier Inc. All rights reserved.
    No preview · Article · Jan 2015 · The Journal of Arthroplasty
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    ABSTRACT: Postoperative periprosthetic femur fractures are an increasing concern after primary total hip arthroplasty (THA). Identifying and understanding predisposing factors are important to mitigating future risk. Femoral stem design may be one such factor. The goals of our study were to compare the (1) frequency of periprosthetic femur fracture and implant survivorship; (2) time to fracture in those patients who experienced periprosthetic femur fracture; and (3) predictive risk factors for periprosthetic femur fracture between a unique stem design with an exaggerated proximal taper angle and other contemporary cementless, proximally fixed, tapered stems. We reviewed all hips in which a femoral hip component with a uniquely exaggerated proximal taper angle (ProxiLock) was implanted during primary THA at a single academic institution. That group of patients was compared with a cohort of patients who underwent primary THA during the same time interval (1995-2008) in which any other cementless, proximally fixed, tapered stem design was used. The two groups differed somewhat in terms of sex, age, and body mass index, although these differences were of unclear clinical significance. During the study, 3964 primary THAs were performed using six different designs of cementless, proximally fixed, tapered femoral hip prostheses. There were 736 stems in the ProxiLock (PL) patient group and 3228 stems in the non-ProxiLock (non-PL) group. In general, the stem highlighted in this study became the routine cementless stem used for primary THA for three arthroplasty surgeons without specific patient or radiographic indications. Periprosthetic fractures were identified within each group. The incidence, timing, type, and treatment required for each fracture were analyzed. The Kaplan-Meier method was used to determine study patient survival free of any postoperative fracture. Radiographs and the electronic medical record of each patient who sustained a fracture were reviewed. Followup was comparable between groups at all time points. The Kaplan-Meier estimate for fracture-free patient survival was worse in the PL group at all time points with survival of 98.4% (range, 97.4%-99.3%), 97.1% (range, 95.9%-98.3%), 95.4% (range, 93.8%-97.0%), and 92.6% (range, 89.6%-95.3%) at 30 days, 1 year, 5 years, and 10 years, respectively, for the PL patient group compared with 99.8% (range, 99.7%-99.9%), 99.6% (range, 99.3%-99.8%), 99.3% (range, 99.0%-99.6%), and 98.4% (range, 97.5%-99.1%) in the non-PL patient group (p < 0.001). Patients in the PL group had increased cumulative probability of both early and late fractures with cumulative probabilities of fracture of 2.5% (range, 1.3%-3.6%) at 90 days and 7.4% (range, 4.7%-10.4%) at 10 years compared with probabilities of 0.3% (range, 0.1%-0.5%) at 90 days and 1.6% (range, 0.8%-2.5%) at 10 years in the non-PL group (p < 0.001). Patients in the PL group had an increased risk of postoperative periprosthetic femur fracture (hazard ratio [HR], 5.6; 95% confidence interval [CI], 3.4-9.1; p < 0.001); fracture requiring reoperation (HR, 8.4; 95% CI, 4.4-15.9); p < 0.001); and fracture requiring stem revision (HR, 9.1; 95% CI, 4.5-18.5; p < 0.001). Age older than 60 years was also a risk factor for fracture (HR, 3.7; 95% CI, 2.1-6.4), but sex, body mass index, and preoperative diagnosis were not predictive. Hips implanted with an uncemented femoral stem, which has a uniquely exaggerated proximal taper angle, had an increased risk of both early and late postoperative periprosthetic femur fracture. The majority of patients with a fracture underwent reoperation or stem revision. The unique proximal geometry, lack of axial support from the smooth cylindrical distal stem as well as resorption of the hydroxyapatite coating and poor ongrowth with subsequent subsidence may contribute to increased risk of fracture. Although this particular stem has recently been discontinued by the manufacturer, these findings are important in regard to followup care for patients with this stem implanted as well as for future cementless stem design in general. Level III, therapeutic study.
    Full-text · Article · Dec 2014 · Clinical Orthopaedics and Related Research
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    ABSTRACT: There is increasing interest in using administrative claims data for surveillance of surgical site infections in THAs and TKAs, but the performance of claims-based models for case-mix adjustment has not been well studied. Performance of claims-based models can be improved with the addition of clinical risk factors for surgical site infections. We assessed (1) discrimination and calibration of claims-based risk-adjustment models for surgical site infections; and (2) the incremental value of adding clinical risk factors to claims-based risk-adjustment models for surgical site infections. Our study included all THAs and TKAs performed at a large tertiary care hospital from January 1, 2002 to December 31, 2009 (total n = 20,171 procedures). Revision procedures for infections were excluded. Comorbidity data were ascertained through administrative records and classified by the Charlson comorbidity index. Clinical details were obtained from the institutional joint registry and patients' electronic health records. Cox proportional hazards regression models were used to estimate the 1-year risk of surgical site infections with a robust sandwich covariance estimator to account for within-subject correlation of individuals with multiple surgeries. The performance of claims-based risk models with and without the inclusion of four clinical risk factors (morbid obesity, prior nonarthroplasties on the same joint, American Society of Anesthesiologists score, operative time) was assessed using measures of discrimination (C statistic, Somers' D xy rank correlation, and the Nagelkerke R(2) index). Furthermore, calibrations of claims-based risk models with and without clinical factors were assessed graphically by plotting the smoothed trends between model predictions and empirical rates from Kaplan-Meier. Discrimination of the claims-based risk models was moderate for the THA (C statistic = 0.662, D xy = 0.325, R(2) = 0.028) and TKA (C statistic = 0.621, D xy = 0.241, R(2) = 0.017) cohorts. Inclusion of four clinical risk factors improved discrimination in both cohorts with significant improvement in the C statistic in the THA cohort (C statistic = 0.043; 95% CI, 0.012-0.074) and in the TKA cohort (C statistic = 0.027; 95% CI, 0.007-0.047). Visual inspection suggested that calibration of the claims-based risk models was adequate and comparable to that of models which included the four additional clinical factors. Claims-based risk-adjustment models for surgical site infections in THA and TKA appear to be adequately calibrated but lack predictive discrimination, particularly with TKAs. The addition of clinical risk factors improves the discriminative ability of the models to a moderate degree; however, addition of clinical factors did not change calibrations, as the models showed reasonable degrees of calibration. When used in the clinical setting, the predictive performance of claims-based risk-adjustment models may be improved further with inclusion of additional clinical data elements.
    No preview · Article · Dec 2014 · Clinical Orthopaedics and Related Research
  • M P Abdel · L Pulido · E P Severson · A D Hanssen
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    ABSTRACT: Instability in flexion after total knee replacement (TKR) typically occurs as a result of mismatched flexion and extension gaps. The goals of this study were to identify factors leading to instability in flexion, the degree of correction, determined radiologically, required at revision surgery, and the subsequent clinical outcomes. Between 2000 and 2010, 60 TKRs in 60 patients underwent revision for instability in flexion associated with well-fixed components. There were 33 women (55%) and 27 men (45%); their mean age was 65 years (43 to 82). Radiological measurements and the Knee Society score (KSS) were used to assess outcome after revision surgery. The mean follow-up was 3.6 years (2 to 9.8). Decreased condylar offset (p < 0.001), distalisation of the joint line (p < 0.001) and increased posterior tibial slope (p < 0.001) contributed to instability in flexion and required correction at revision to regain stability. The combined mean correction of posterior condylar offset and joint line resection was 9.5 mm, and a mean of 5° of posterior tibial slope was removed. At the most recent follow-up, there was a significant improvement in the mean KSS for the knee and function (both p < 0.001), no patient reported instability and no patient underwent further surgery for instability. The following step-wise approach is recommended: reduction of tibial slope, correction of malalignment, and improvement of condylar offset. Additional joint line elevation is needed if the above steps do not equalise the flexion and extension gaps. Cite this article: Bone Joint J 2014;96-B:1644-8. ©2014 The British Editorial Society of Bone & Joint Surgery.
    No preview · Article · Dec 2014 · Bone and Joint Journal
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    ABSTRACT: Background. The National Healthcare Safety Network surgical site infections risk models for hip (HPRO) and knee (KPRO) replacement are intended for case-mix adjustment when reporting surgical site infection rates across institutions, but they are not validated in external data sets. Objective. To evaluate the validity of HPRO and KPRO risk models and improvement in risk prediction with inclusion of information on morbid obesity and diabetes mellitus. Design. Retrospective cohort study. Patients. A single-center cohort of 21,941 hip and knee replacement procedures performed between 2002 and 2009. Methods. Discriminative ability was assessed using the concordance statistic (C statistic). Calibration was assessed using the Hosmer-Lemeshow goodness-of-fit tests. Results. The discrimination of HPRO was good, with a C statistic of 0.695 for surgical site infections and 0.749 for prosthetic joint infections. The discrimination of KPRO was worse than that of HPRO, with a C statistic of 0.592 for surgical site infections and 0.675 for prosthetic joint infections. Adding morbid obesity and diabetes mellitus to the HPRO and KPRO risk models modestly improved discrimination. There was no significant evidence of miscalibration based on the Hosmer-Lemeshow tests, but calibration of HPRO models appeared to be better than that of the KPRO models. Conclusions. HPRO performed better than the KPRO in predicting surgical site infections after hip and knee replacements. Both fared well in predicting prosthetic joint infections.
    No preview · Article · Nov 2014 · Infection Control and Hospital Epidemiology

Publication Stats

10k Citations
913.86 Total Impact Points


  • 1988-2015
    • Mayo Clinic - Rochester
      • • Division of Orthopaedic Surgery
      • • Department of Orthopedics
      Рочестер, Minnesota, United States
  • 2014
    • Mayo Foundation for Medical Education and Research
      • Department of Orthopaedic Surgery
      Рочестер, Michigan, United States
    • Hospital for Special Surgery
      New York, New York, United States
  • 2012
    • Case Western Reserve University School of Medicine
      Cleveland, Ohio, United States
  • 2009
    • UConn Health Center
      Farmington, Connecticut, United States
  • 2008
    • Sinai Hospital
      Baltimore, Maryland, United States
    • Rose Hulman Institute of Technology
      • Department of Mechanical Engineering
      Indiana, United States
  • 2004
    • Rothman Institute
      Philadelphia, Pennsylvania, United States
  • 2001
    • Roger Williams University
      Бристоль, Rhode Island, United States
  • 1996
    • University of Pennsylvania
      Philadelphia, Pennsylvania, United States