Search

Background: Subtalar joint arthrodesis is a common operative treatment for symptomatic subtalar arthrosis. Because excessive relative motion between the talus and calcaneus can delay or prohibit fusion, fixation should be optimized, particularly in patients at risk for subtalar arthrodesis nonunion. Tapered, fully-threaded, variable pitch screws are gaining popularity for this application, but the mechanical properties of joints fixed with these screws have not been characterized completely. We quantified the torsion resistance of 2-screw and 3-screw subtalar joint fixation using this type of screw., Methods: Ten pairs of cadaveric subtalar joints were prepared for arthrodesis and fixed using Acutrak 2-7.5 screws. One specimen from each pair was fixed with two diverging posterior screws, and the contralateral joint was fixed using two posterior screws and a third screw directed through the anterior calcaneus into the talar neck. Internal and external torsional loads were applied and joint rotation and torsional stiffness were measured at two torque levels., Findings: Internal rotation was significantly less in specimens fixed with three screws. No difference was detectable between 2-screw and 3-screw fixation in external rotation or torsional stiffness in either rotation direction. Both 2-screw and 3-screw fixation exhibited torsion resistance surpassing that reported previously for subtalar joints fixed with two diverging conventional lag screws., Interpretation: Performance of the tapered, fully threaded, variable pitch screws exceeded that of conventional lag screws regardless of whether two or three screws were used. Additional resistance to internal rotation afforded by a third screw placed anteriorly may offer some advantage in patients at risk for nonunion., (Copyright © 2017. Published by Elsevier Ltd.)

Background: Oblique osteotomies of the first metatarsal are common surgical treatments for moderate to severe hallux valgus deformity. Osteotomy fixation integrity is important to minimize interfragment motion and maintain correction during healing, and our clinical observations suggest that patient age and bone quality affect fixation stability and ultimately the clinical outcome. Accordingly, this study correlated these patient factors with key mechanical measures of osteotomy angulation resistance in a cadaver hallux valgus correction model., Methods: Standard Ludloff osteotomies were created in 31 fresh-frozen first metatarsals and fixed with two cannulated, dual-pitch headless screws. Each specimen underwent 1000 plantar-to-dorsal bending loads while monitoring bending stiffness and distal fragment dorsal angulation. Donor age and bone mineral density were then correlated with each mechanical measure at selected cycling increments., Findings: We found significant positive correlation between bone mineral density and osteotomy fixation stiffness for all evaluated load cycles. Moderate negative correlation between bone density and angulation was identified, significant for load cycle 500. There was a weak, nonsignificant negative correlation between donor age and osteotomy bending stiffness, with r ranging from -0.134 to -0.243 between the first and 1000th loads. Little correlation was demonstrable between age and angulation., Interpretation: Because low bone density correlates with decreased osteotomy site stiffness and increased angulation under load, patient compliance and protected weight bearing in the early postoperative phase are particularly important if bone mineral density is exceptionally low. Correspondingly, patients with especially high bone mineral density may be considered candidates for earlier weight bearing and active physical therapy., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Introduction: Arthrodesis is a well-established treatment option for end-stage osteoarthritis of the ankle. Osteoarthritis of the ankle can alter plantar pressure distribution. However, surprisingly little is known about the effect of ankle arthrodesis to alter plantar pressure distribution. The purpose of this study was to determine plantar pressure distribution in a selected group of patients with unilateral arthrodesis of the ankle joint., Methods: 20 patients with an average age of 60 years who underwent isolated unilateral ankle arthrodesis using a 3-crossed screw technique by a single surgeon were included. After a mean of 25 months (range 12-75 months) post surgery plantar pressure distribution was determined in five regions of the foot. The outcome was evaluated clinically, using the American Orthopaedic Foot and Ankle Society hindfoot score, as well as radiographically. The contralateral normal foot was used as a control., Findings: Comparing the foot that underwent tibiotalar arthrodesis to the contralateral normal foot, differences were found in the peak pressure and maximum force in the toe region and the lateral midfoot region. In addition, a decrease in the contact time in the forefoot region and a decrease of the contact area in the toe region of the operated foot were identified. The other regions did not show a significant difference. The mean American Orthopaedic Foot and Ankle Society score of the operated leg was 79 (range 46-92) at the last follow up, and the mean fixation angle of the arthrodesis on lateral weight bearing radiographs was 90° (range 86°-100°)., Interpretation: Our results indicate that arthrodesis of the ankle joint can provide high levels of function with minimal changes in the plantar pressure distribution., (Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.)

Background: The optimal osteotomy type and fixation method for hallux valgus correction have not been defined. This study examined the mechanical properties of corrective opening-wedge and Ludloff oblique osteotomies under conditions approximating postoperative weight-bearing., Methods: Twenty-nine pairs of fresh-frozen metatarsals were divided into three groups. In Group 1, headless screws were compared with standard cortical screws for Ludloff osteotomy fixation. In Groups 2 and 3, Ludloff osteotomies fixed with headless screws were compared with opening-wedge osteotomies fixed with non-locking and locking plates, respectively. Constructs underwent dorsally-directed cantilever loading for 1000 cycles., Findings: No significant differences in angulation or stiffness were demonstrable in Group 1. In Group 2, Ludloff/headless screw construct stiffness exceeded non-locking plate construct stiffness. The mean angulation on the 1000th load cycle was greater for plates than for Ludloff/headless screws. In Group 3, locking plate construct stiffness and angulation did not differ from Ludloff/headless screws in early cyclic loading, but fixation failure of the locking plate constructs was common., Interpretation: The results indicate that screw type for Ludloff fixation may be left to surgeon preference and that opening-wedge plates exhibit mechanical properties inferior to that of the Ludloff osteotomy under the tested conditions. Lateral cortex continuity and bone density remain important factors in the performance of opening-wedge osteotomies.