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Henderson C.E.,University of Iowa | Kuhl L.L.,University of Iowa | Fitzpatrick D.C.,Legacy Research and Technology Center | Marsh J.L.,University of Iowa
Journal of Orthopaedic Trauma | Year: 2011

Objectives: Fractures of the distal femur are severe injuries that present many clinical challenges. Nonunion, delayed union, implant failure, and the need for secondary procedures can reflect complications of healing. This article reviews the literature on distal femur fractures treated with locking plates to determine the reported rate of healing difficulties. Data Sources: The PubMed database and the Orthopaedic Trauma Association and American Academy of Orthopedic Surgeons abstract archives were searched for studies including the key words distal femur fracture, supracondylar femur fracture, or locking plate from the year 2000 to the present. Study Selection: Reports were included when distal femur fractures were treated with locking plates and when the number of healed fractures was identified in the study. The reported healing rates and the rate of healing complications were determined from the studies. The time to implant failure was recorded. Those articles that included periprosthetic fractures were separated from those only including acute distal femur fractures. Data Synthesis: Fifteen full-length publications and three abstracts were included. The rate of complications related to healing ranged from 0% to 32% in these studies. Implant failures occurred late with 75% of the failures occurring after 3 months and 50% occurring after 6 months. Conclusions: Complications of healing including nonunion, delayed union, and implant failure are not infrequent and represent ongoing problems with distal femur fracture treatment. Further clinical research combined with innovation in surgical techniques and implant design will be necessary to improve the results of the last decade. Copyright © 2011 by Lippincott Williams & Wilkins. Source

Girard M.J.A.,Devers Eye Institute | Girard M.J.A.,Tulane University | Girard M.J.A.,Imperial College London | Francis Suh J.-K.,Tulane University | And 6 more authors.
Investigative Ophthalmology and Visual Science | Year: 2011

Purpose. To characterize scleral biomechanics in both eyes of eight monkeys in which chronic intraocular pressure (IOP) elevation was induced in one eye. Methods. Each posterior sclera was mounted on a pressurization apparatus, IOP was elevated from 5 to 45 mm Hg while the 3D displacements of the scleral surface were measured by speckle interferometry. Finite element (FE) models of each scleral shell were constructed that incorporated stretch-induced stiffening and multidirectionality of the collagen fibers. FE model predictions were then iteratively matched to experimental displacements to extract unique sets of scleral biomechanical properties. Results. For all eyes, the posterior sclera exhibited inhomogeneous, anisotropic, nonlinear biomechanical behavior. Biomechanical changes caused by chronic IOP elevation were complex and specific to each subject. Specifically: (1) Glaucomatous eyes in which the contralateral normal eyes displayed large modulus or thickness were less prone to biomechanical changes; (2) glaucomatous scleral modulus associated with an IOP of 10 mm Hg decreased (when compared with that of the contralateral normal) after minimal chronic IOP elevation; (3) glaucomatous scleral modulus associated with IOPs of 30 and 45 mm Hg increased (when compared with that of the contralateral normal) after moderate IOP elevation; and (4) FE-based estimates of collagen fiber orientation demonstrated no change in the glaucomatous eyes. Conclusions. Significant stiffening of the sclera follows exposure to moderate IOP elevations in most eyes. Scleral hypercompliance may precede stiffening or be a unique response to minimal chronic IOP elevation in some eyes. These biomechanical changes are likely to be the result of scleral extracellular matrix remodeling. © 2011 The Association for Research in Vision and Ophthalmology, Inc. Source

Bahney C.S.,Oregon Health And Science University | Lujan T.J.,Legacy Research and Technology Center | Hsu C.W.,Rice University | Bottlang M.,Legacy Research and Technology Center | And 2 more authors.
European Cells and Materials | Year: 2011

Biological activity can be added to synthetic scaffolds by incorporating functional peptide sequences that provide enzyme-mediated degradation sites, facilitate cellular adhesion or stimulate signaling pathways. Poly(ethylene glycol) diacrylate is a popular synthetic base for tissue engineering scaffolds because it creates a hydrophilic environment that can be chemically manipulated to add this biological functionality. Furthermore, the acrylate groups allow for encapsulation of cells using photopolymerization under physiological conditions. One complication with the addition of these peptides is that aromatic amino acids absorb light at 285nm and compete with the ultraviolet (UV)-sensitive photoinitiators such as IrgacureTM 2959 (I2959), the most commonly used initiator for cytocompatible photoencapsulation of cells into synthetic scaffolds. In this study we define non-toxic conditions for photoencapsulation of human mesenchymal stem cells (hMSC) in PEGDA scaffolds using a visible light photoinitiator system composed of eosin Y, triethanolamine and 1-vinyl-2-pyrrolidinone. This visible light photoinitiator produced hydrogel scaffolds with an increased viability of encapsulated hMSCs and a more tightly crosslinked network in one-third the time of UV polymerization with I2959. Source

Bottlang M.,Legacy Research and Technology Center | Feist F.,Legacy Research and Technology Center
Journal of Orthopaedic Trauma | Year: 2011

The development of far cortical locking (FCL) was motivated by a conundrum: locked plating constructs provide inherently rigid stabilization, yet they should facilitate biologic fixation and secondary bone healing that relies on flexible fixation to stimulate callus formation. Recent studies have confirmed that the high stiffness of standard locked plating constructs can suppress interfragmentary motion to a level that is insufficient to reliably promote secondary fracture healing by callus formation. Furthermore, rigid locking screws cause an uneven stress distribution that may lead to stress fracture at the end screw and stress shielding under the plate. This review summarizes four key features of FCL constructs that have been shown to enhance fixation and healing of fractures: flexible fixation, load distribution, progressive stiffening, and parallel interfragmentary motion. Specifically, flexible fixation provided by FCL reduces the stiffness of a locked plating construct by 80% to 88% to actively promote callus proliferation similar to an external fixator. Load is evenly distributed between FCL screws to mitigate stress risers at the end screw. Progressive stiffening occurs by near cortex support of FCL screws and provides additional support under elevated loading. Finally, parallel interfragmentary motion by the S-shaped flexion of FCL screws promotes symmetric callus formation. In combination, these features of FCL constructs have been shown to induce more callus and to yield significantly stronger and more consistent healing compared with standard locked plating constructs. As such, FCL constructs function as true internal fixators by replicating the biomechanical behavior and biologic healing response of external fixators. Copyright © 2011 by Lippincott Williams & Wilkins. Source

Henderson C.E.,University of Iowa | Lujan T.J.,Legacy Research and Technology Center | Kuhl L.L.,University of Iowa | Bottlang M.,Legacy Research and Technology Center | And 2 more authors.
Clinical Orthopaedics and Related Research | Year: 2011

Background: Several mechanical studies suggest locking plate constructs may inhibit callus necessary for healing of distal femur fractures. However, the rate of nonunion and factors associated with nonunion are not well established. Questions/purposes: We (1) determined the healing rate of distal femur fractures treated with locking plates, (2) assessed the effect of patient injury and treatment variables on fracture healing, and (3) compared callus formation in fractures that healed with those that did not heal. Patients and Methods: We retrospectively reviewed 82 patients treated with 86 distal femur fractures using lateral locking plates. We reviewed all charts and radiographs to determine patient and treatment variables and then determined the effects of these variables on healing. We quantitatively measured callus at 6, 12, and 24 weeks. The minimum time for telephone interviews and SF-36v2™ scores was 1 year (mean, 4.2 years; range, 1-7.2 years). Results: Fourteen fractures (20%) failed to unite. Demographics and comorbidities were similar in patients who achieved healing compared with those who had nonunions. There were more empty holes in the plate adjacent to fractures that healed; comminuted fractures failed to heal more frequently than less comminuted fractures. Less callus formed in fractures with nonunions and in patients treated with stainless steel plates compared with titanium plates. Complications occurred in 28 of 70 fractures (40%), 19 of which had additional surgery. Conclusions: We found a high rate of nonunion in distal femur fractures treated with locking plates. Nonunion presented late without hardware failure and with limited callus formation suggesting callus inhibition rather than hardware failure is the primary problem. Mechanical factors may play a role in the high rate of nonunion. Level of Evidence: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence. © 2011 The Association of Bone and Joint Surgeons®. Source

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