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Fregly B.J.,University of Florida | Besier T.F.,University of Auckland | Lloyd D.G.,Griffith University | Delp S.L.,Stanford University | And 3 more authors.
Journal of Orthopaedic Research | Year: 2012

Impairment of the human neuromusculoskeletal system can lead to significant mobility limitations and decreased quality of life. Computational models that accurately represent the musculoskeletal systems of individual patients could be used to explore different treatment options and optimize clinical outcome. The most significant barrier to model-based treatment design is validation of model-based estimates of in vivo contact and muscle forces. This paper introduces an annual "Grand Challenge Competition to Predict In Vivo Knee Loads" based on a series of comprehensive publicly available in vivo data sets for evaluating musculoskeletal model predictions of contact and muscle forces in the knee. The data sets come from patients implanted with force-measuring tibial prostheses. Following a historical review of musculoskeletal modeling methods used for estimating knee muscle and contact forces, we describe the first two data sets used for the first two competitions and summarize four subsequent data sets to be used for future competitions. These data sets include tibial contact force, video motion, ground reaction, muscle EMG, muscle strength, static and dynamic imaging, and implant geometry data. Competition participants create musculoskeletal models to predict tibial contact forces without having access to the corresponding in vivo measurements. These blinded predictions provide an unbiased evaluation of the capabilities and limitations of musculoskeletal modeling methods. The paper concludes with a discussion of how these unique data sets can be used by the musculoskeletal modeling research community to improve the estimation of in vivo muscle and contact forces and ultimately to help make musculoskeletal models clinically useful. Copyright © 2011 Orthopaedic Research Society.

Falck-Ytter Y.,Case Western Reserve University | Francis C.W.,University of Rochester | Johanson N.A.,Drexel University | Curley C.,Case Western Reserve University | And 6 more authors.
Chest | Year: 2012

Background: VTE is a serious, but decreasing complication following major orthopedic surgery. This guideline focuses on optimal prophylaxis to reduce postoperative pulmonary embolism and DVT. Methods: The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement. Results: In patients undergoing major orthopedic surgery, we recommend the use of one of the following rather than no antithrombotic prophylaxis: low-molecular-weight heparin; fondaparinux; dabigatran, apixaban, rivaroxaban (total hip arthroplasty or total knee arthroplasty but not hip fracture surgery); low-dose unfractionated heparin; adjusted-dose vitamin K antagonist; aspirin (all Grade 1B); or an intermittent pneumatic compression device (IPCD) (Grade 1C) for a minimum of 10 to 14 days. We suggest the use of low-molecular-weight heparin in preference to the other agents we have recommended as alternatives(Grade 2C/2B), and in patients receiving pharmacologic prophylaxis, we suggest adding an IPCD during the hospital stay(Grade 2C). We suggest extending thromboprophylaxis for up to 35 days(Grade 2B). In patients at increased bleeding risk, we suggest an IPCD or no prophylaxis(Grade 2C). In patients who decline injections, we recommend using apixaban or dabigatran(all Grade 1B). We suggest against using inferior vena cava filter placement for primary prevention in patients with contraindications to both pharmacologic and mechanical thromboprophylaxis(Grade 2C). We recommend against Doppler(or duplex) ultrasonography screening before hospital discharge(Grade 1B). For patients with isolated low-erextremity injuries requiring leg immobilization, we suggest no thromboprophylaxis(Grade 2B). For patients undergoing knee arthroscopy without a history of VTE, we suggest no thromboprophylaxis (Grade 2B). Conclusions: Optimal strategies for thromboprophylaxis after major orthopedic surgery include pharmacologic and mechanical approaches. ©2012 American College of Chest Physicians.

Gortz S.,University of California at San Diego | De Young J.A.,Shiley Center for Orthopaedic Research and Education | Bugbee W.D.,Scripps Research Institute
Clinical Orthopaedics and Related Research | Year: 2010

Background Osteonecrosis is a complication of corticosteroid therapy with limited treatment options in young, active patients. These options include debridement, core decompression, osteotomy, allografting, and partial or total knee replacement. Few studies exist regarding the use of osteochondral allografts for treatment of steroidassociated osteonecrosis. Questions/purposes We asked if fresh osteochondral allografts would (1) heal to host bone in the presence of osteonecrosis, (2) provide a clinically meaningful decrease in pain and improvement in function, and (3) prevent or postpone the need for prosthetic arthroplasty. Patients and Methods Twenty-two patients (28 knees) who underwent osteochondral allografting for high-grade, corticosteroid-associated osteonecrosis were evaluated. Their average age was 24.3 years (range, 16-44 years). The mean graft surface area was 10.8 cm2 (range, 5.0- 19.0 cm2). Evaluation included a modified (for the knee) D'Aubigne' and Postel (18-point) score, International Knee Documentation Committee (IKDC), and Knee Society function scores. The minimum followup was 25 months (mean, 67 months; range, 25-235 months). Results Five knees failed. The graft survival rate was 89% (25 of 28). The mean D'Aubigne' and Postel score improved from 11.3 to 15.8; 19 of 25 (76%) had a score greater than 15. The mean IKDC pain score improved from 7.1 to 2.0, mean IKDC function score from 3.5 to 8.3, and mean Knee Society function score from 60.0 to 85.7. Conclusions Our data suggest osteochondral allografting is a reasonable salvage option for osteonecrosis of thefemoral condyles. TKA was avoided in 27 of the 28 of knees at last followup. Level of Evidence Level IV, case series. See Guidelines for Authors for a complete description of levels of evidence. © The Association of Bone and Joint Surgeons® 2010.

Colwell Jr. C.W.,Shiley Center for Orthopaedic Research and Education | Chen P.C.,Shiley Center for Orthopaedic Research and Education | D'Lima D.,Shiley Center for Orthopaedic Research and Education
Clinical Biomechanics | Year: 2011

Background: Many patellofemoral complications such as anterior knee pain, subluxation, fracture, wear, and aseptic loosening after total knee arthroplasty are attributed to malrotation of the femoral component. Rotating-platform mobile bearings can reduce malrotation between the tibial and femoral components and may also improve patellofemoral maltracking. Methods: A computer model (LifeMOD/KneeSIM) of a weight-bearing deep knee bend was validated using cadaver knees tested in an Oxford-type knee rig. Changes in knee kinematics and patellofemoral forces were measured after femoral component malrotation of ± 3°. The effect of a rotating-bearing on these kinematics and forces was determined. Findings: In a fixed-bearing arthroplasty femoral component internal malrotation increased tibiofemoral internal rotation by 3.4°, and external malrotation increased tibiofemoral external rotation by 4°. Femoral component malrotation affected patellofemoral lateral shift by up to 2.5 mm, and patellofemoral lateral shear by up to 19 N. When the malrotated femoral component was tested against a rotating-bearing the change in tibiofemoral rotation and patellofemoral lateral shift was less than 1° and 1 mm respectively. The rotating-bearing reduced peak lateral shear by 7 N and peak medial shear by 17 N. Increasing the conformity of the rotating-bearing reduced changes in tibiofemoral rotation due to femoral malrotation and increased the net rotation of the bearing (by approximately 5°) during flexion. Interpretation: Our results are consistent with one randomized clinical outcome study and emphasize the value of computational modeling for preclinical design evaluation. It is important to continue to improve existing methodologies for accurate femoral component alignment especially in rotation. © 2010 Elsevier Ltd.

Bunn A.,Shiley Center for Orthopaedic Research and Education | Colwell Jr. C.W.,Shiley Center for Orthopaedic Research and Education | D'Lima D.D.,Shiley Center for Orthopaedic Research and Education
Clinical Orthopaedics and Related Research | Year: 2012

Background: Factors affecting risk for impingement and dislocation can be related to the patient, implant design, or surgeon. While these have been studied independently, the impact of each factor relative to the others is not known. Questions/purposes: We determined the effect of three implant design factors, prosthetic placement, and patient anatomy on subject-specific ROM. Methods: We virtually implanted hip geometry obtained from 16 CT scans using computer models of hip components with differences in head size, neck diameter, and neck-shaft angle. A contact detection model computed ROM before prosthetic or bony impingement. We correlated anatomic measurements from pelvic radiographs with ROM. Results: When we implanted the components for best fit to the subject's anatomy or in the recommended orientation of 45° abduction and 20° anteversion, ROM was greater than 110° of flexion, 30° of extension, 45° of adduction-abduction, and 40° of external rotation. Changes in head size, neck diameter, and neck-shaft angle generated small gains (3.6°-6°) in ROM when analyzed individually, but collectively, we noted a more substantial increase (10°-17°). Radiographic measurements correlated only moderately with hip flexion and abduction. Conclusions: It is feasible to tailor implant placement to each patient to maximize bony coverage without compromising ROM. Once bony impingement becomes the restricting factor, further changes in implant design may not improve ROM. Radiographic measurements do not appear to have value in predicting ROM. © 2011 The Association of Bone and Joint Surgeons®.

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