Clinical biomechanics
-
Clinical biomechanics · Oct 2009
The strength of polyaxial locking interfaces of distal radius plates.
Currently available polyaxial locking plates represent the consequent enhancement of fixed-angle, first-generation locking plates. In contrast to fixed-angle locking plates which are sufficiently investigated, the strength of the new polyaxial locking options has not yet been evaluated biomechanically. This study investigates the mechanical strength of single polyaxial interfaces of different volar radius plates. ⋯ The strength of the polyaxial locking interfaces differs remarkably between the examined implants. Depending on the implant an increase of the screw locking angle causes a reduction of ultimate or fatigue strength, but not in all cases a significant impact was observed.
-
Clinical biomechanics · Jul 2009
The effect of interspinous implant surgery on back surface shape and radiographic lumbar curvature.
Interspinous process implants, used to augment lumbar spine surgery, putatively induce a local segmental lumbar kyphosis yet few investigations outline the effect in vivo on thoracolumbar sagittal curvature. Changes in lumbar skeletal alignment and posture have traditionally relied upon radiographic and back surface spinal curvature measurements, respectively. ⋯ Rasterstereography is sensitive in assessing lumbar lordosis changes in healthy and lumbar surgical individuals over time. Surgery with DIAM for lumbar pathology may result in an initial mild flattening of lordosis. Serial investigations of spinal curvature after surgery with DIAM interspinous implant are warranted in order to better understand the time-course of spinal posture changes of such cases.
-
Clinical biomechanics · May 2009
Factors influencing interlocking screw failure in unreamed small diameter nails--a biomechanical study using a distal tibia fracture model.
Unreamed tibia nails with small diameters are increasingly used for fracture fixation. However, little is known about the fatigue strength of proximal and distal interlocking screws in those nails. To date, no data are available reporting on mechanical differences of solid compared to cannulated tibial nails. The aim of this study was to assess the fatigue strength of proximal and distal interlocking screws of solid and cannulated small diameter tibia nails. ⋯ Proximal and distal interlocking screw failure has to be considered in small diameter nails in case of delayed fracture healing. To support our results, further experimental studies and clinical series are necessary.
-
Clinical biomechanics · May 2009
Bulk compressive properties of the heel fat pad during walking: a pilot investigation in plantar heel pain.
Altered mechanical properties of the heel pad have been implicated in the development of plantar heel pain. However, the in vivo properties of the heel pad during gait remain largely unexplored in this cohort. The aim of the current study was to characterise the bulk compressive properties of the heel pad in individuals with and without plantar heel pain while walking. ⋯ Plantar heel pain is characterised by reduced energy dissipation ratio of the heel pad when measured in vivo and under physiologically relevant strain rates.
-
Clinical biomechanics · Feb 2009
Relative stability of conventional and locked plating fixation in a model of the osteoporotic femoral diaphysis.
This study investigated the stiffness and strength of bridge plating with uni-cortical and bi-cortical locking plate constructs relative to a conventional, non-locked construct in the osteoporotic femoral diaphysis. ⋯ Locked plating in the osteoporotic diaphysis can improve fixation strength under axial loading, but may reduce fixation strength in bending and torsion compared to conventional plating. Adding one bi-cortical locked screw to an otherwise uni-cortical construct is recommended to improve torsional strength.