The compressive, bending and torsional mechanical properties of osteotomized adult equine tibiae stabilized with an interlocking intramedullary nail (nail-tibia composite) were compared with those of intact tibiae to determine the clinical applicability of the the nail for repair of tibial fractures in adult horses. The mean yield load, failure load, and stiffness for the nail-tibia composites were significantly less (P < .05) than those for the intact tibiae in all loading configurations. The mean compressive yield load for the nail-tibia composites was greater than the compressive load calculated from previously reported in vivo data for walking and trotting, and was equal to the load calculated for recovery from anesthesia. The mean yield bending moment for the nail-tibia composites was greater than the bending moment previously calculated for standing, walking, and recovery from anesthesia. The mean torsional yield load for the nail-tibia composites was less than the torsional load determined for the walk from another in vivo study. The design of the interlocking nail evaluated in the present study should be modified to increase torsional and compressive yield strengths and torsional stiffness before reasonable success could be expected for the treatment of adult equine tibial fractures.
Dietary acidity is a likely contributor to the development of osteoporosis. Dietary acidosis in an ovine model has effects on trabecular bone that have been previously shown to mimic human osteoporosis. Effects on cortical bone using this model have not been investigated. The objective of this study was to examine the effects of dietary acidosis on cortical bone mineral density and material properties. Skeletally mature ovariectomized (OVX) sheep consumed either a normal diet (ND) or a metabolic acidosis diet (MA) for 6 or 12 months. Whole femoral and cortical bone beam BMD was determined using dual energy x-ray absorptiometry (DEXA). Beams were then subjected to three point flexure monotonically to failure to determine strength and modulus and then ashed to determine percent mineralization. Femoral BMD in adult OVX ND 6 mo sheep was significantly greater than those in the non-OVX ND group. The BMD in the MA groups was lower than the control non-OVX ND group. Cortical beams had significantly decreased modulus in all MA and OVX groups when compared with the non-OVX ND group and a tendency towards decreased strength in all groups with significance only in the OVX ND 6 mo sheep. Percent mineralization increased in MA and OVX groups when compared to the non-OVX ND group and was significantly increased in the OVX ND 6 mo and OVX MA 12 mo groups. A significant correlation was seen between BMD of the beam and breaking strength and modulus. Dietary acidity impacts cortical bone and results in reduced material properties that may contribute to failure.
The objective of this study was to determine the predictive value of tip-apex distance (TAD) and Parker's ratio for screw cutout after treatment of intertrochanteric hip fractures with a long cephalomedullary nail. A total of 97 patients with AO/OTA 31-A1-A3 intertrochanteric fractures and a minimum follow-up of 8 weeks were included. Increased Parker's ratio on the anteroposterior radiograph (OR = 1.386, p < .003) and lateral radiograph (OR = 1.138, p < .028) was significantly associated with screw cutout. In a multivariable regression analysis, only the Parker's anteroposterior ratio was significantly associated with risk of screw cutout (OR = 1.393, p = .004), but TAD (OR = 0.977, p = .764) and Parker's lateral ratio (OR 1.032, p = .710) were not independent predictors of cutout. The study concluded that Parker's anteroposterior ratio is the most helpful measurement in predicting screw cutout. (Journal of Surgical Orthopaedic Advances 28(2):115-120, 2019).
We studied the deformation of the extracellular matrices in articular cartilage using a new compression-preservation method in histology. A Hoffman clamp was used to compress the tissue, which remained throughout the paraffin procedure and was removed from the embedded tissue block just before microtoming. Then 14 cartilage-bone blocks from 2 canine humeri were compressed for various strain levels from 5% to 65%. The histological sections were studied using a polarized light microscope, which generated a pair of two-dimensional maps of the fibril orientation (angle) and fibril organization (retardance) for each section. Results were 3-fold. One there was little change in the angle and retardance profiles of the tissue for strain levels 0–15% and a significant change in these profiles for strain levels 15% and above. Two for higher compression, more fibrils became aligned parallel to the articular surface; and three at ∼30% strain, a second "transitional zone" was formed in the deep part of the tissue. We concluded that this novel compression procedure can be used effectively to study the altered architecture of the collagen matrix in compressed cartilage.YX and GL would like to dedicate this paper to a co-author of this study and our long-time collaborator in cartilage research, Nancy Burton-Wurster (1941–2006).
