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Background: Quantitative objective measures to determine fusion achievement further enable the comparison of new technologies, such as interbody cage surface enhancement. Our aims were to compare in vivo biomechanical responses of ovine L4/5 lumbar motion segments with two cages: 1) Polyetheretherketone or 2) Polyetheretherketone with a nanosurfaced titanium porous scaffold from Nanovis, Inc., Methods: Fourteen Merino sheep randomly received either 1) standard Polyetheretherketone cage or 2) Nanocoated Polyetheretherketone cage at L4/L5 with autologous bone graft. At baseline and one-year follow-up, dynamic spinal stiffness was quantified in vivo using a validated mechanical assessment at 2 Hz, 6 Hz, and 12 Hz. The dorsoventral secant stiffness (k y  = force/displacement, N/mm) and L4-L5 accelerations were determined at each frequency. A repeated measures analysis of variance with Bonferonni correction was used to evaluate within and between group differences among the biomechanical variables., Findings: Both implants increased spinal stiffness at 2 Hz (21 and 39%, respectively, p < .005), and at 6 Hz (12 and 27%, p < .0001). Significantly greater spinal stiffness was observed with Nanocoated Polyetheretherketone at one-year for both frequencies (p < .05). No significant differences were observed at 12 Hz within or between groups. L4-L5 dorsoventral accelerations were significantly decreased one year following cage placement only with Nanocoated Polyetheretherketone (p < .05) and greater reductions in acceleration were observed with Nanocoated Polyetheretherketone compared to standard Polyetheretherketone (p < .05)., Interpretation: Both cages increased spinal stiffness, yet, nanosurfaced cages resulted in greater spinal stiffness changes and decreases in L4-L5 accelerations. These findings may assist in clinical decision making and post-operative recovery strategies., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: The objective of this study was to determine the effect of an interspinous implant on lumbar spine stability and stiffness during dorsoventral loading., Methods: Twelve Merino lambs were mechanically tested in vivo. Oscillatory (2 Hz) loads were applied to L2 under load control while displacements were monitored. Tri-axial accelerometers further quantified adjacent L3-L4 accelerations. Dorsoventral lumbar spine stiffness and L3 and L4 dorsoventral and axial displacements were determined over six trials of 20 cycles of loading. Four conditions were examined: 1) initial intact, 2) following destabilization at L3-L4, 3) following the insertion of an InSwing(®) interspinous device at L3-L4, and 4) with the implant secured with a tension band. Comparisons were performed using a one-way ANOVA with repeated measures and post-hoc Bonferroni correction., Findings: Compared to the intact condition, destabilization significantly decreased lumbar stiffness by 4.5% (P=.001) which was only recovered by the interspinous device with tension band. The interspinous device caused a significant 9.75% (P=.001) increase in dorsoventral stiffness from destabilization that increased 14% with the tension band added (P=.001). The tension band was responsible for decreased displacements from the intact (P=.038), instability (P=.001), and interspinous device (P=.005) conditions. Dorsoventral L3-L4 motion significantly improved with the interspinous device (P=.01) and the addition of the tension band (P=.001). No significant differences in L3-L4 intersegmental stability were noted for axial motion in the sagittal plane., Interpretation: This ovine model provided objective in vivo biomechanical evidence of lumbar instability and its restoration by means of an interspinous implant during dorsoventral spinal loading., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background: Among the millions of people suffering from a hip fracture each year, 20% may sustain a contralateral hip fracture within 5 years with an associated mortality risk increase reaching 64% in the 5 following years. In this context, we performed a biomechanical study to assess the performance of a hip fracture preventing implant., Methods: The implant consists of two interlocking peek rods unified with surgical cement. Numerical and biomechanical tests were performed to simulate single stance load or lateral fall. Seven pairs of femurs were selected from elderly subjects suffering from osteoporosis or osteopenia, and tested ex-vivo after implantation of the device on one side., Findings: The best position for the implant was identified by numerical simulations. The loadings until failure showed that the insertion of the implant increased significantly (P<0.05) both fracture load (+18%) and energy to fracture (+32%) of the implanted femurs in comparison with the intraindividual controls. The instrumented femur resisted the implementation of the non-instrumented femur fracture load for 30 cycles and kept its performance at the end of the cyclic loading., Interpretation: Implantation of the fracture preventing device improved both fracture load and energy to fracture when compared with intraindividual controls. This is consistent with previous biomechanical side-impact testing on pairs of femur using the same methodology. Implant insertion seems to be relevant to support multiple falls and thus, to prevent a second hip fracture in elderly patients., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objective: To clarify the biomechanical indicators of single- and multi-level stenosis and to determine the biomechanical outcome of selective conservative decompression., Design: This study is a prospective clinical trial examining trunk function in spinal stenosis patients operated using a conservative procedure in an orthopaedic clinic., Background: Although several clinical studies have examined the instability and motion characteristics of operated lumbar spinal canal stenosis, few if any studies have prospectively examined the biomechanical outcome of lumbar spinal canal stenosis surgery., Methods: Comprehensive pre- and post-operative trunk dynamometer strength and motion analysis tests were performed on 36 patients operated for lumbar canal stenosis. Surgical treatment efficacy was evaluated within a three variable crossed factorial design considering stenosis classification, number of operative levels, and changes in several trunk biomechanical outcomes from pre- to post-operative assessment. Patients were evaluated after a minimum one-year follow-up., Results: Pre-operatively there were no differential effects associated with stenosis classification or number of operated levels. There was a significant post-operative increase in isometric trunk extension torque and flexion-extension power and a return to a more normal trunk extension-flexion torque ratio. Patients with mixed, single level stenosis demonstrated greater trunk extension power both pre- and post-operatively compared to other patients., Conclusions: Conservative surgical treatment of lumbar spinal stenosis produced a marked improvement in the functional mechanical status of the low back., Relevance: This study assists clinicians and researchers to understand trunk function following conservative surgical treatment of lumbar spinal stenosis.

A procedure for averaging trunk dynamometric positions, velocities, and torques is described which enables identification and parameterization of kinematic movement patterns. This technique is accurate and presents the data in a very compact way, which is ideal for storage and analysis. It can be applied to many types of movement analyses. Application of the technique to the analysis of flexion-extension movement patterns in two low back pain patients is described., (Copyright © 1993. Published by Elsevier Ltd.)