Cadaveric Bones Research Articles

In-vivo comparison of chemically polished vs. unpolished magnesium-based screws in ovine tibiae

Event Abstract Back to Event In-vivo comparison of chemically polished vs. unpolished magnesium-based screws in ovine tibiae Leopold Berger1, Johannes Eichler2, Martina Cihova3, Elisabeth Martinelli2, Claudia Kleinhans2, Jörg Löffler3 and Annelie-Martina Weinberg2 1 TU Wien, Institute for Building Construction and Technology, Austria 2 Medical University of Graz, Department of Orthopaedic and Orthopaedic Surgery, Austria 3 ETH Zurich, Laboratory of Metal Physics and Technology, Department of Materials, Switzerland Introduction: Magnesium (Mg) and its alloys possess ideal characteristics in mecha­nical properties and biological acceptance, and thus are of great promise for deployment as implant material, particularly in surgical stabi­lisation of bone fractures. The relatively fast degradation ability avoids second surgeries for removal of the implant [1]. Essential for their applicability is a sufficient load baring capacity for a clinically relevant time frame, which is directly linked to a reliable degradation rate and good bone ingrowth. , The purpose of this study was therefore to (1) analyse the general applicability of Mg-based screws for their use in cortical bone (2) study whether an improved degradation and therefore biomechanical performance can be achieved by chemical surface treatment. Methods: Screws (diameter: 3.5 mm, length: 16 mm) were dry-machined from the biodegradable Mg alloy ultrahigh-purity (XHP) ZX00 (Mg-0.3Zn-0.4Ca). The surface of 4 screws was chemically polished (mixture of ethanol and phosphoric acid), whereas the others remained untreated. Seven screws (4 chemically polished and 3 unpolished) were gamma-sterilized and inserted into two ovine right tibiae (experimental, N=2 animals), and six further screws were implanted in the cadaveric right tibiae (control, N=2) after sacrificing the animal six weeks after implantation. These control screws were placed exactly on contralateral positions. All animal studies were performed in accordance with the Austrian Ministry of Science and Research (accreditation number BMWFW-66.010/0190-WF/V/3b/2014). An axial pull-out test was performed on the screws of the in vivo groups, and the same method was also applied on the cadaveric control bones. Fig. 1: Pull-out test method performed on XHP-ZX00 screws in sheep tibiae. Results: The pull-out tests revealed lower strength of screws that stayed in the tibia for 6 weeks in comparison to the control group (Fig. 1). Chemically polished screws exhibited lower pull-out strength than untreated samples (sample size not sufficient for statistical comparison). [MC1] Analysis of bone cross section after pull-out tests revealed that the screws of both groups partly failed by shearing-off the thread flanks and partly by failure of the bone tissue. Fig. 2: Pull-out test of XHP ZX00 screws (chemically polished and untreated) inserted in ovine tibiae (diaphysis and distal epiphysis) for 6 weeks vs. ex vivo control group. Discussions and Conclusions: These first experiments show that screws made of XHP-Mg-alloy ZX00 revealed good bone integration. For all screws tested, after 6 weeks of implantation the pull-out test reveals lower load-bearing capacity in comparison to the non-degraded control. This loss in strength is associated with initial degradation of the screws and according to expectations. The lower pull-out strength of chemically polished screws may be due to volume loss resulting from the chemical surface treatment. Facing the importance of surface finish for medical implants, results emphasize the need of (1) careful adjustment of the polishing protocol and (2) thorough evaluation of its in vivo response. The interface strength still appears to be sufficient for clinical applications. Obtained data is subject of high volatility. Thus, further studies need to be performed to evaluate degradation, ingrowth and tissue reactions of Mg-screws in more detail. Laura Bassi BRIC, Austrian Promotion Agency

Characteristics of Wax Occlusion in the Surgical Repair of Superior Canal Dehiscence in Human Temporal Bone Specimens.

Superior canal dehiscence (SCD) repair using surgical bone wax may result in variable outcomes if large wax volumes are applied. SCD is a disorder characterized by a pathologic defect in the bony labyrinth of the superior semicircular canal (SSC), resulting in vestibular and/or auditory symptoms. Repair of SCD using bone wax can provide symptomatic relief, but surgical outcomes are variable. These observations may be associated with the inconsistency in the position and extension of intralabyrinthine bone wax during surgical repair. A pathological model of SCD was created using cadaveric human temporal bones and a microdrill. Defects in the arcuate eminence 0.5 to 3.5 mm in length were repaired by surgical occlusion with bone wax. The volume of wax used in the repair was quantified. The position of bone wax was evaluated by direct visualization and imaging (computed tomography [CT]). To visualize wax on CT, specimens were repaired using radiopaque wax. Exceedingly small volumes of bone wax (3.0-5.0 mm2) reliably occluded the canal lumen. Multiple wax applications resulted in extension into the common crus and ampulla. The length of this extension was related to the number of applications. Repair of SCD with bone wax occludes the bony defect completely in most patients. Wax can extend along the lumen of the superior canal beyond the limits of the dehiscence to reach the sensory neuroepithelium of the vestibular end organs. Limiting the number of wax applications is essential to avoid inadvertent injury to the delicate neurosensory systems.

2016

The purpose of this study was to evaluate and compare the intrusion characteristics of Simplex-HV to Simplex-P and Palacos-R in cadaveric proximal tibial bone. Eighteen fresh-frozen cadaver proximal tibiae were examined with standard arthroplasty tibial cuts. Each tibia was randomly assigned to receive one of the three bone cements for use with finger packing technique. Sagittal sections were prepared and analyzed using digital photography and stereoscopic micrographs to evaluate cement intrusion characteristics. The cement penetration depth was measured from the tibial bone cut surface, which did not include the cement thickness under the tibial base plate. Significant differences were detected in the bone cement penetration between the three cements. Penetration was increased using the Simplex-HV (average, 2.7 mm; range, 2.0-3.0 mm) compared with Simplex-P (average, 2.2 mm) and Palacos-R (average, 1.8 mm). These depths approximate to 3.7, 3.2, and 2.8 mm of total cement penetration, respectively. The data suggest that high-viscosity bone cement may provide good fixation of the tibial component of a total knee arthroplasty when using the finger packing technique.

Artificial atlanto-axial joints: On the “move”

The current management of atlantoaxial dislocation emphasizes on C1-2 reduction and fusion. The fusion of C1-2, however, hampers the neck movements significantly. The author has designed and developed artificial C1-2 joints that can mimic the natural joints to some extent. The concept and nuances of the design has been described. The joints have been fixed in dry cadaveric bones to demonstrate the possible movements.

Feasibility study of a novel intraosseous device in adult human cadavers

Background & objectives:Intraosseous (IO) access is an alternative to difficult intravenous (iv) access during emergency clinical situations. Existing IO solutions are expensive, require power supply and trained manpower; limiting their use in resource constrained settings. To address these limitations, a novel IO device has been developed. The objectives of this study were to evaluate functionality and safety of this device in adult human cadavers.Methods:The ability of the IO device to penetrate the proximal and/or distal tibia was evaluated in three adult cadavers. Subjective parameters of loss of resistance, stable needle hold, easy needle withdrawal and any damage to the device were evaluated during the study. The insertion time was the objective parameter measured. Four sets of radiographs per insertion confirmed the position of the needle and identified complications.Results:A single physician performed 12 IO access procedures using the same device. Penetration of proximal and/or distal tibia was achieved in all instances. It was successful in the first attempt in eight (66.7%) and during second attempt in the remaining. The mean time to insertion was 4.1 ± 3.1 sec. Appropriate insertion of needle in the intra-medullary space of bone was confirmed with radiological examination in 10 (83.3%) insertions. In two occasions after penetrating the cortical layer of bone, the device overshot the intra-medullary space, as detected by radiological examination. Device got bent during insertion in one instance. There was no evidence of needle breakage or bone fracture. The needle could be withdrawn effortlessly in all instances.Interpretation & conclusions:The novel IO device could successfully penetrate the adult cadaver bones in most cases. Further studies are needed to confirm these results on a large sample.

Coupling Effect of Water and Proteoglycans on the In Situ Toughness of Bone.

Proteoglycans (PGs) are one type of noncollagenous proteins in the extracellular matrix of bone that primarily contain a core protein and glycosaminoglycans (GAGs). GAGs are highly polar and negatively charged, thus have a strong tendency to attract water molecules into the matrix. We hypothesized in this study that PGs in bone play a pivotal role in sustaining the toughness of the tissue only when water is present. To test the hypothesis, we used a novel nanoscratch test to measure the in situ toughness of human cadaveric bone treated with and without peptide-N-glycosidase F (PNGase F), an enzyme that specifically removes the N-linked oligosaccharides of GAGs from core proteins. Cortical bone specimens were prepared from the posterior aspect of mid-diaphyseal femurs of six (n = 6) male human donors between 51.5 ± 5.17 years old. Biochemical and histochemical assays were used to verify whether N-linked oligosaccharides were removed from bone matrix by PNGase F. By testing wet and dehydrated bone specimens, the coupling effect between water and PGs on the in situ toughness of bone was investigated. The two-way ANOVA analyses showed that removal of GAGs had significant effects on the in situ toughness of wet bone samples. In contrast, the removal of GAGs did not show significant effects on the toughness of dry bone. The results of this study, for the first time, suggest that GAGs play a pivotal role in the in situ toughness of bone only when water is present, and vice versa, water functions as a plasticizer in bone only when GAGs are present. © 2015 American Society for Bone and Mineral Research.

Construct damage and loosening around glenoid implants: A longitudinal micro-CT study of five cadaver specimens.

The evolution of failure of bone and cement leading to loosening of glenoid components following shoulder arthroplasty is not well understood. The purpose of this study was to identify and visualize potential mechanisms of mechanical failure within cadavers, cemented with two types of components, and subject to cyclic loading. Five glenoid cadaver bones were implanted with either a three-pegged polyethylene component, or prototype posteriorly augmented component which addresses posterior bone loss. Specimens were loaded by constant glenohumeral compression combined with cyclic anterior-posterior displacement of the humeral head relative to the glenoid. At six time points across 100,000 cycles, implant loosening micromotions were optically measured, and specimens were imaged by micro-computed tomography. Scans were 3D registered and inspected for crack initiation and progression, and micro-CT based time-lapse movies were created. Cement cracking initiated at stress concentrations and progressed with additional cyclic loading. Failure planes within trabecular bone and the bone-cement interface were identified in four of the five specimens. Implant subsidence increased to greater than 1.0 mm in two specimens. Cemented glenoid structural failure can occur within the cement, along planes of trabecular bone, or at the bone cement interface. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1053-1060, 2016.

A method to measure sound transmission via the malleus–incus complex

BackgroundThe malleus–incus complex (MIC) plays a crucial role in the hearing process as it transforms and transmits acoustically-induced motion of the tympanic membrane, through the stapes, into the inner-ear. However, the transfer function of the MIC under physiologically-relevant acoustic stimulation is still under debate, especially due to insufficient quantitative data of the vibrational behavior of the MIC. This study focuses on the investigation of the sound transformation through the MIC, based on measurements of three-dimensional motions of the malleus and incus with a full six degrees of freedom (6 DOF). MethodsThe motion of the MIC was measured in two cadaveric human temporal bones with intact middle-ear structures excited via a loudspeaker embedded in an artificial ear canal, in the frequency range of 0.5–5 kHz. Three-dimensional (3D) shapes of the middle-ear ossicles were obtained by sequent micro-CT imaging, and an intrinsic frame based on the middle-ear anatomy was defined. All data were registered into the intrinsic frame, and rigid body motions of the malleus and incus were calculated with full six degrees of freedom. Then, the transfer function of the MIC, defined as velocity of the incus lenticular process relative to velocity of the malleus umbo, was obtained and analyzed. ResultsBased on the transfer function of the MIC, the motion of the lenticularis relative to the umbo reduces with frequency, particularly in the 2–5 kHz range. Analysis of the individual motion components of the transfer function indicates a predominant medial-lateral component at frequencies below 1 kHz, with low but considerable anterior-posterior and superior-inferior components that become prominent in the 2–5 kHz range. ConclusionThe transfer function of the human MIC, based on motion of the umbo and lenticularis, has been visualized and analyzed. While the magnitude of the transfer function decreases with frequency, its spatio-temporal complexity increases significantly.

Parameters for novel incus replacement prostheses.

Prostheses replacing the incus in its normal position and equipped with two joints might transfer sound as effectively as the intact ossicular chain and allow adjustment to quasi-static pressure changes. A prerequisite for prostheses development is the access to dimensions and distances of the ossicular chain which are necessary to conceptualize shape and size. Fifteen cadaveric human temporal bone specimens were investigated by means of micro-CT followed by 3D analysis. Each specimen was scanned three times: after removal of incus, after additional removal of the malleus head, and after approaching the umbo to the promontory. Artificial umbo medialization as a surrogate for quasi-static pressure changes leads to relevant variations in the distance between the upper part of the malleus and the stapes. Prostheses replacing the incus in its normal position should be equipped with a sliding ball joint or similar construction to allow adjustment to quasi-static pressure changes.

Propriétés biomécaniques d’un clou élastique en titane sur modèle cadavérique claviculaire

BackgroundThe goal of this study was to examine biomechanical properties of titanium elastic nail fixation method that was applied to cadaveric clavicles with different thicknesses and lengths. MethodsTo test stiffness and failure load of clavicle with titanium elastic nail fixation, 12 pairs of clavicles were obtained. A short oblique fracture line (AO/OTA classification: 15-B1.2) was created at midpoint of the cadaveric bones. They were divided into four groups according to the nails with different thickness and length/diameter ratios. The fixated bones were situated on a jig that allows 3-point bending to measure stiffness and load failure. ResultsThe stiffness was measured to be mean 3.49±1.49N/mm in group 1. The stiffness for group 2 was mean 10.41±2.18N/mm, and for groups 3 and 4, the stiffness was mean 11.89±2.99N/mm and mean 24.44±4.86N/mm, respectively. When analyzed with statistics, group 1 had significant differences from groups 2 (P<0.006), 3 (P<0.001), and 4 (P<0.000), and group 4 also had statistical significances from the rest of the groups (P<0.000). ConclusionsFor 2.5mm titanium elastic nail, it is necessary to make fixation with a titanium elastic nail that is longer than 3 diameter lengths, and a length that is longer than and equal to 3 diameter length titanium elastic nail was required for 3.5mm titanium elastic nail to provide appropriate stiffness for firm fixation. Also, variances in both thickness and length have shown a similar effect. Study designCadaveric study.

Biomechanical properties of titanium elastic nail applied to a cadaveric clavicle model

BackgroundThe goal of this study was to examine biomechanical properties of titanium elastic nail fixation method that was applied to cadaveric clavicles with different thicknesses and lengths. MethodsTo test stiffness and failure load of clavicle with titanium elastic nail fixation, 12 pairs of clavicles were obtained. A short oblique fracture line (AO/OTA classification: 15-B1.2) was created at midpoint of the cadaveric bones. They were divided into four groups according to the nails with different thickness and length/diameter ratios. The fixated bones were situated on a jig that allows 3-point bending to measure stiffness and load failure. ResultsThe stiffness was measured to be mean 3.49±1.49N/mm in group 1. The stiffness for group 2 was mean 10.41±2.18N/mm, and for groups 3 and 4, the stiffness was mean 11.89±2.99N/mm and mean 24.44±4.86N/mm, respectively. When analyzed with statistics, group 1 had significant differences from groups 2 (P<0.006), 3 (P<0.001), and 4 (P<0.000), and group 4 also had statistical significances from rest of the groups (P<0.000). ConclusionsFor 2.5mm titanium elastic nail, it is necessary to make fixation with a titanium elastic nail that is longer than 3 diameter lengths, and length that is longer than and equal to 3 diameter length titanium elastic nail was required for 3.5mm titanium elastic nail to provide appropriate stiffness for firm fixation. Also, variances in both thickness and length have shown a similar effect. Study designCadaveric study.

Comparison of Three Fixation Methods for Femoral Neck Fracture in Young Adults: Experimental and Numerical Investigations.

Femoral neck fractures in young patients are usually caused by a high-energy trauma, which results in a perpendicular fracture. Although efforts are focused on preserving the femoral head in young patients, vertical femoral neck fracture is a problematic orthopedic injury due to the domination of shear forces. Due to controversy regarding which fixation method is the best choice, the purpose of this study was to find the most stable fixation method for this kind of fracture. This study includes experimental testing on cadaveric bone samples and finite element analysis (FEA) for three fracture fixation techniques, namely cannulated screws (CSs), dynamic hip screw with derotational screw (DHS + DS), and proximal femoral locking plate (PFLP). Experimental results of bone-implant stiffness, average femoral head displacement, failure load, failure energy, and relative position of the fractured fragments indicate that DHS + DS offers the strongest structure for stabilizing a vertical femoral neck fracture. Experimental data and FEA results both indicate that under static loading, the DHS + DS method of fixation produces the lowest femoral head displacement and interfragmentary movement, followed by PFLP and then CSs. The results of this research suggest that, based on the clinical assumption that a restricted weight-bearing regimen is recommended in the postoperative rehabilitation protocol, the DHS + DS method of fixation is a better choice compared to CSs and PFLP for a vertical femoral neck fracture fixation in young adults.

A technique for developing CAD geometry of long bones using clinical CT data

Computed tomography scans are a valuable tool for developing computational models of bones. The objective of this study is to present a method to generate CAD representations of long bones from clinically based CT scans. A secondary aim is to apply the method to six long bones from a sample of three individuals. Periosteal and endosteal bone surfaces were segmented and used to calculate the characteristic cortical thickness, Tc, at 1 mm increments along the bone axis. In the epiphyses where the value of Tc fell below the scanner threshold, the endosteal bone layer was replaced using literature values projected inward from the periosteal surface. On average, 74.7 ± 7.4% of the bone geometry was above the scanner cut-off and was therefore derived from the CT scan data. The thickness measurement was also compared to experimental measurements of cadaveric bone and was found to predict Tc with an error of 3.1%. This method presents a possible solution for the characterization of characteristic thickness along the length of the bone and may also aid in the development of orthopedic implant design and subject specific finite element models.

Heat accumulation during sequential cortical bone drilling.

Significant research exists regarding heat production during single-hole bone drilling. No published data exist regarding repetitive sequential drilling. This study elucidates the phenomenon of heat accumulation for sequential drilling with both Kirschner wires (K wires) and standard two-flute twist drills. It was hypothesized that cumulative heat would result in a higher temperature with each subsequent drill pass. Nine holes in a 3 × 3 array were drilled sequentially on moistened cadaveric tibia bone kept at body temperature (about 37 °C). Four thermocouples were placed at the center of four adjacent holes and 2 mm below the surface. A battery-driven hand drill guided by a servo-controlled motion system was used. Six samples were drilled with each tool (2.0 mm K wire and 2.0 and 2.5 mm standard drills). K wire drilling increased temperature from 5 °C at the first hole to 20 °C at holes 6 through 9. A similar trend was found in standard drills with less significant increments. The maximum temperatures of both tools increased from <0.5 °C to nearly 13 °C. The difference between drill sizes was found to be insignificant (P > 0.05). In conclusion, heat accumulated during sequential drilling, with size difference being insignificant. K wire produced more heat than its twist-drill counterparts. This study has demonstrated the heat accumulation phenomenon and its significant effect on temperature. Maximizing the drilling field and reducing the number of drill passes may decrease bone injury.

A rabbit humerus model of plating and nailing osteosynthesis with and without Staphylococcus aureus osteomyelitis.

The local mechanical environment at a fracture is known to influence biological factors such as callus formation, immune cell recruitment and susceptibility to infection. Infection models incorporating a fracture are therefore required to evaluate prevention and treatment of infection after osteosynthesis. The aim of this study was to create humane, standardised and repeatable preclinical models of implant-related bone infection after osteosynthesis in the rabbit humerus. Custom-designed interlocked intramedullary nails and commercially available locking plates were subjected to biomechanical evaluation in cadaveric rabbit humeri; a 10-week in vivo healing study; a dose response study with Staphylococcus aureus over 4 weeks; and finally, a long-term infection of 10 weeks in the plate model.Outcome measures included biomechanical testing, radiography, histology, haematology and quantitative bacteriology. Both implants offered similar biomechanical stability in cadaveric bones, and when applied in the in vivo study, resulted in complete radiographic and histological healing and osteotomy closure within 10-weeks. As expected in the infection study, higher bacterial doses led to an increasing infection rate. In both infected groups, there was a complete lack of osteotomy closure at 4 weeks. C-reactive protein (CRP), lymphocyte: granulocyte ratio and weight loss were increased in infected animals receiving IM nails in comparison with non-inoculated equivalents, although this was less evident in the plate group. In the 10-week infection group, healing does not occur in the plated rabbits. We have successfully developed a rabbit model that is suitable for further studies, particularly those looking into preventative strategies for post-traumatic implant-related osteomyelitis.

Cadaveric bone marrow mesenchymal stem cells: first experience treating a patient with large severe burns.

BackgroundIn January 2005, Rasulov et al. originally published “First experience in the use of bone marrow mesenchymal stem cells (MSCs) for the treatment of a patient with deep skin burns”. Here, we present the first ever treated patient with cadaveric bone marrow mesenchymal stem cells (CMSCs) in the history of Medicine.MethodsA young man, who severely burned 60 % of his total body surface with 30 % of full-thickness burns while working with a grass trimmer that exploded, was involved in the study. MSCs were obtained from the bone marrow of a cadaver donor in a routine procurement procedure of CUCAIBA, the Province of Buenos Aires, Argentina, Ministry of Health, Transplantation Agency, cultured, expanded, and applied on the burned surfaces using a fibrin spray after early escharotomy.ResultsSo far, our preliminary experience and our early results have been very impressive showing an outstanding safety data as well as some impressive good results in the use of CMSCs.ConclusionsBased on all this, we think that improvements in the use of stem cells for burns might be possible in the near future and a lot of time as well as many lives could be saved by many other research teams all over the world. CMSCs will probably be a real scientific opportunity in Regenerative Medicine as well as in Transplantation.

Pediatric Semicircular Canal Dehiscence: Radiographic and Histologic Prevalence, With Clinical Correlation.

To determine the prevalence of radiographic and histologic superior semicircular canal dehiscence (SSCD) and posterior semicircular canal dehiscence (PSCD) and associated changes in temporal bone thickness in children aged 0 to 7 years. Retrospective chart review and histopathologic review of cadaveric bone specimens. Two tertiary referral centers. Children younger than 7 years who underwent high-resolution computed tomography scan including the temporal bones between 1998 and 2013 and temporal bones harvested from children younger than 7 years. Two hundred twenty-eight computed tomography studies and 58 temporal bone specimens were reviewed. Available patient demographics were tabulated. Prevalence of SSCD and PSCD and bone thickness over semicircular canals, with comparison across age groups. Clinical data were extracted for patients with radiographic dehiscence. Prevalence by ear of SSCD was 11.9%, 4.9%, 2.8%, and 0% and of PSCD was 16.7%, 2.4%, 1.4%, and 0% in children aged less than 6 months, 6 to 11 months, 12 to 35 months, and 3 to 7 years, respectively. SSCD was statistically more common before 1 year of age and PSCD before 6 months of age. Bone thickness overlying both the SSC and the PSC increased with age. Radiographic PSC bone was significantly thicker than SSC bone in patients older than 12 months. No dehiscences were found in the histologic specimens. Radiographic dehiscence of the canals is common in the first 6 months of life, with thin bone seen histologically. Prevalence decreases with increasing age as the bone overlying the canals increases in thickness.

The effects of distal interlocking screws on torsional stability in three-part intertrochanteric hip fractures

ObjectiveMany surgeons currently use long cephomedullary nails for the treatment of intertrochanteric fractures. The optimal indications for deploying distal interlocks are still debatable. This study examined the torsional biomechanical properties of 3-part intertrochanteric femur fractures in a cadaveric bone model using two different distal fixation strategies, an unlocked long cephalomedullary nail versus a dynamically locked nail. Our hypothesis is that a long cephalomedullary nail does not require distal locking fixation when used for treatment of a 3-part intertrochanteric fracture.MethodsFive matched pairs of cadaveric femora were randomly assigned to one of two distal fixation treatment groups; a single distal interlock screw placed in the dynamic orientation or no distal fixation. A 3-part intertrochanteric fracture was produced. Specimens were potted and mounted in a double gimbal fixture facilitating unconstrained motion in the sagittal and coronal planes. Specimens were cyclically loaded dynamically in both internal and external rotation. Range of motion, internal and external rotation stiffness, torsion stiffness, torsion yield and ultimate torsion magnitude were calculated.ResultsThe samples instrumented with a distal locking screw reported statistically greater external rotational stiffness than the unlocked samples in nondestructive testing. The results of the destructive data demonstrated no statistical difference between the locked and unlocked group with regard to yield torque (p = 0.282), peak torque (p = 0.340), stiffness (p = 0.220), displacement at yield torque (p = 0.0605), and displacement at peak torque (p = 0.280).ConclusionDistal locking of a long cephalomedullary nail increases the stiffness of the nail-femur construct in a 3-part biomechanical fracture model. However, our testing illustrates that an unlocked construct will tolerate at least equal stress before catastrophic failure in a torsional loading model.

Femoral fixation strength following soft-tissue posterolateral corner reconstruction using fibular-based technique: Biomechanical analysis of four techniques in normal and low-density synthetic bone

BackgroundOptimal femoral fixation of soft-tissue grafts has been described for anterior cruciate ligament reconstruction. Posterolateral corner reconstruction differs from ACL reconstruction in two ways: (a) soft-tissue fixation into the femur requires two tails and (b) the line of force is different. Our purpose was to determine the optimal femoral fixation of soft-tissue grafts during posterolateral corner reconstructions. We hypothesized that interference screw fixation is the strongest technique in normal-density lateral femoral condyle, whereas, cortically-based fixation techniques are stronger methods in low-density lateral femoral condyle. MethodsWe evaluated elongation during cyclic loading, yield load, peak load-to-failure, and stiffness of four soft-tissue graft femoral fixation methods during posterolateral corner reconstruction. Our model included bovine flexor tendons and contoured synthetic bones. Grafts were secured to the lateral epicondyle in normal- or low-density bone models using spiked washer, button, interference screw, or button and interference screw. Five specimens for each were tested in each bone density. Analysis of variance using Tukey–Kramer adjustment for multiple hypothesis testing was used. Six cadaver bones whose density was analyzed using computerized tomography scan quantitation were tested using interference screw fixation. ResultsNo method produced significantly stronger yield load or peak load-to-failure in normal-density bone. In low-density bone, cortically-based methods produced significantly higher yield load or peak load-to-failure. Yield load or peak load-to-failure was significantly higher in normal-density bone when using spiked washer or interference screw fixation. ConclusionNo femoral fixation method tested produced superior yield load or peak load-to-failure. Spiked washer and interference screw fixation are inferior fixation methods in low-density bone. Clinical relevanceFor fibular-based posterolateral corner reconstructions, all fixation methods tested are acceptable in high-density bone, while cortical fixation methods should be considered in low-density bone.

A scoping review of biomechanical testing for proximal humerus fracture implants.

BackgroundFixation failure is a relatively common sequela of surgical management of proximal humerus fractures (PHF). The purpose of this study is to understand the current state of the literature with regard to the biomechanical testing of proximal humerus fracture implants.MethodsA scoping review of the proximal humerus fracture literature was performed, and studies testing the mechanical properties of a PHF treatment were included in this review. Descriptive statistics were used to summarize the characteristics and methods of the included studies.Results1,051 proximal humerus fracture studies were reviewed; 67 studies met our inclusion criteria. The most common specimen used was cadaver bone (87 %), followed by sawbones (7 %) and animal bones (4 %). A two-part fracture pattern was tested most frequently (68 %), followed by three-part (23 %), and four-part (8 %). Implants tested included locking plates (52 %), intramedullary devices (25 %), and non-locking plates (25 %). Hemi-arthroplasty was tested in 5 studies (7 %), with no studies using reverse total shoulder arthroplasty (RTSA) implants. Torque was the most common mode of force applied (51 %), followed by axial loading (45 %), and cantilever bending (34 %). Substantial testing diversity was observed across all studies.ConclusionsThe biomechanical literature was found to be both diverse and heterogeneous. More complex fracture patterns and RTSA implants have not been adequately tested. These gaps in the current literature will need to be addressed to ensure that future biomechanical research is clinically relevant and capable of improving the outcomes of challenging proximal humerus fracture patterns.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-015-0627-x) contains supplementary material, which is available to authorized users.