Eugene, OR, United States
Eugene, OR, United States

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Denard P.J.,Oregon Health And Science University | Doornink J.,Legacy Biomechanics Laboratory | Phelan D.,Legacy Biomechanics Laboratory | Madey S.M.,Legacy Biomechanics Laboratory | And 2 more authors.
Clinical Biomechanics | Year: 2011

Background: Elevation of a locking plate over the bone surface not only supports biological fixation, but also decreases the torsional strength of the fixation construct. Biplanar fixation by means of a staggered screw hole arrangement may combat this decreased torsional strength caused by plate elevation. This biomechanical study evaluated the effect of biplanar fixation on the torsional strength of locking plate fixation in the femoral diaphysis. Methods: Custom titanium plates were manufactured with either a linear or staggered hole pattern to evaluate planar and biplanar fixation, respectively. Fixation strength under torsional loading was evaluated in surrogates of the femoral diaphysis representative of osteoporotic and non-osteoporotic bone. Furthermore, fixation strength was determined for plate fixation with unicortical or bicortical locking screws. Five specimens per configuration were loaded to failure in torsion to determine their strength, stiffness, and failure mode. Findings: In osteoporotic bone, biplanar fixation was 32% stronger (P = 0.01) than planar fixation when unicortical screws were used and 9% stronger (P = 0.02) when bicortical screws were used. In non-osteoporotic bone, biplanar fixation was 55% stronger (P < 0.001) than planar fixation when unicortical screws were used and 42% (P < 0.001) stronger when bicortical screws were used. Interpretation: A biplanar screw configuration improves the torsional strength of diaphyseal plate fixation relative to a planar configuration in both osteoporotic and normal bone. With biplanar fixation, unicortical screws provide the same fixation strength as bicortical screws in non-osteoporotic bone. © 2010 Elsevier Ltd.

Bottlang M.,Legacy Research and Technology Center | Helzel I.,Legacy Research and Technology Center | Long W.,Legacy Research and Technology Center | Fitzpatrick D.,Slocum Center for Orthopaedics | Madey S.,Legacy Research and Technology Center
Journal of Trauma - Injury, Infection and Critical Care | Year: 2010

Background: This study evaluated intramedullary fixation of rib fractures with Kirschner wires and novel ribs splints. We hypothesized that rib splints can provide equivalent fixation strength while avoiding complications associated with Kirschner wires, namely wire migration and cutout. Methods: The durability, strength, and failure modes of rib fracture fixation with Kirschner wires and rib splints were evaluated in 22 paired human ribs. First, intact ribs were loaded to failure to determine their strength. After fracture fixation with Kirschner wires and rib splints, fixation constructs were dynamically loaded to 360,000 cycles at five times the respiratory load to determine their durability. Finally, constructs were loaded to failure to determine residual strength and failure modes. Results: All constructs sustained dynamic loading without failure. Dynamic loading caused three times more subsidence in Kirschner wire constructs (1.2 mm ± 1.4 mm) than in rib splint constructs (0.4 mm ± 0.2 mm, p = 0.09). After dynamic loading, rib splint constructs remained 48% stronger than Kirschner wire constructs (p = 0.001). Five of 11 Kirschner wire constructs failed catastrophically by cutting through the medial cortex, leading to complete loss of stability and wire migration through the lateral cortex. The remaining six constructs failed by wire bending. Rib splint constructs failed by development of fracture lines along the superior and interior cortices. No splint construct failed catastrophically, and all splint constructs retained functional reduction and fixation. Conclusions: Because of their superior strength and absence of catastrophic failure mode, rib splints can serve as an attractive alternative to Kirschner wires for intramedullary stabilization of rib fractures, especially in the case of posterior rib fractures where access for plating is limited. © 2010 Lippincott Williams & Wilkins.

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®.

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