Biomechanical comparison of different fixation methods in tibiotalocalcaneal arthrodesis: a cadaver study.

BACKGROUND: Various fixation methods are available for tibiotalocalcaneal arthrodesis: nail, plate, or screws. An intramedullary bone stabilization system within a balloon catheter has not previously been used in tibiotalocalcaneal arthrodesis. The aim of this study was to compare the stability of these techniques. METHODS: Twenty-four lower legs from fresh-frozen human cadavers were used. Tibiotalocalcaneal arthrodesis was performed with a retrograde nail, a lateral locking plate, three cancellous screws, or an intramedullary bone stabilization system. The ankles were loaded cyclically in plantarflexion and dorsiflexion. RESULTS: For cyclic loading at 125 N, the mean range of motion was 1.7 mm for nail, 2.2 mm for plate, 6.0 mm for screws, and 9.0 mm for the bone stabilization system (P < .01). For cyclic loading at 250 N, the mean range of motion was 4.4 mm for nail, 7.5 mm for plate, 12.1 mm for screws, and 14.6 mm for the bone stabilization system (P < .01). The mean cycle of failure was 4191 for nail, 3553 for plate, 3725 for screws, and 2132 for the bone stabilization system (P = .10). CONCLUSIONS: The stability of the tibiotalocalcaneal arthrodesis differs depending on the fixation method, with nail or plate showing the greatest stability and the bone stabilization system the least. When three screws are used for tibiotalocalcaneal arthrodesis, the stability is intermediate. As the biomechanical stability of the bone stabilization system is low, it cannot be recommended for tibiotalocalcaneal arthrodesis.

Ultrastructural characterization of mitochondrial damage in experimental autoimmune neuritis.

Data are sparse about mitochondrial damage in GBS and in its most frequently employed animal model, experimental autoimmune neuritis (EAN). We here characterized changes in mitochondrial content and morphology at different time points during EAN by use of ultrastructural imaging and immunofluorescent labelling. Histological examination revealed that demyelinated axons and their adjacent Schwann cells showed reduced mitochondrial content and remaining mitochondria appeared swollen with greater diameter in Schwann cells and unmyelinated axons. Our findings indicate that in EAN, particularly mitochondria in Schwann cells are damaged. Further studies are warranted to address whether these changes are amenable to novel, mitoprotective treatments.

Biomechanical comparison of conventional versus modified technique in distal chevron osteotomies of the first metatarsal: A cadaver study.

BACKGROUND: Distal chevron osteotomy can be performed using a conventional or a modified technique. The aim of this biomechanical study was to compare the stability of the two techniques. METHODS: Eighteen first metatarsals from nine pairs of fresh frozen human cadaver feet were used. A distal chevron osteotomy was performed using the conventional technique in group 1 (n=9) and using the modified technique in group 2 (n=9). The head of the first metatarsals was loaded in two different configurations (cantilever and physiological), using a materials testing machine. RESULTS: In the cantilever configuration, the relative stiffness of the osteosynthesis in comparison with intact bone was 60% (±21%) in group 1 and 65% (±25%) in group 2 (p=0.61). In the physiological configuration, it was 47% (±29%) in group 1 and 47% (±21%) in group 2 (p=0.98). The failure strength in the cantilever configuration was 235N (±128N) in group 1 and 210N (±107N) in group 2 (p=0.47). CONCLUSIONS: The conventional and the modified technique for distal chevron osteotomy in the treatment of hallux valgus show a comparable biomechanical loading capacity in this cadaver study.

Glass -polyalkenoate cement: An alternative material for kyphoplasty in osteoporotic vertebral compression fractures - An ex vivo study.

Adjacent vertebral body fracture is described as a risk after vertebroplasty and kyphoplasty. It may be true that this phenomenon is caused precisely because of the frequently used polymethylmethacrylate cement (PMMA), which shows a higher level of stiffness than bone material and may ultimately lead to shifting stress levels within the entire spine. The goal of the present study was to evaluate and compare the pressure distribution in the endplate of human vertebrae after kyphoplasty with PMMA and aluminum-free glass-polyalkenoate cement (gpc). For the present study, 8 fresh frozen human cadaveric vertebral bodies from the thoracolumbar junction were used. All vertebrae were augmented transpedicularly on one side with gpc and on the other side with PMMA. A loading of 600 N, 800 N and 1000 N was applied. In the data processing an individual region of interest (roi) was generated for each vertebra. The following parameters were determined for each roi: maximum force [N], maximum pressure [kPa], mean pressure [kPa], roi area [cm2]. We found significantly higher mean pressure values in the areas of the vertebrae augmented with PMMA, compared to the ones after augmentation with gpc (p = 0.012) when applying 1000 N. In the groups with lower forces there were no statistical relevant differences. The pressure distribution shows an advantage for gpc. A material, which does not create load concentration onto the cranial and caudal vertebral surface, could have major advantages concerning the risk of adjacent vertebral fractures. Thus the results of the 1000 N loading protocol suggest gpc being a possible alternative to ordinary PMMA cement, regarding its influence on stiffness in kyphoplasty. These and other general aspects like incorporation should be addressed and elaborated more detailed in further studies.

Distal radius: anatomical morphometric gender characteristics. Do anatomical pre-shaped plates pay attention on it?

INTRODUCTION: The purpose of the study was to investigate differences in the osseous structure anatomy of male and female distal radii. METHODS: Morphometric data were obtained of 49 distal human cadaveric radii. An imprint of the distal edge was attained using silicone mass and the palmar cortical angle (PCA) of the lateral and intermediate column, here declared as medial, according to the concept of Rikli and Rigazzoni. The lateral and medial length and five widths were digitally measured by three observers. In order to compare the measurements an unpaired t test was used. To prove the reliability of the measurements an intraclass correlation analyses was done. RESULTS: Overall mean medial PCA was 148.25° (SD ± 6.83) and mean lateral PCA 156.07° (SD ± 7.00). In male specimens, the mean medial PCA was 147.38° (SD ± 6.01) and mean lateral PCA was 153.6° (SD ± 6.20) whereas in female specimens, the mean medial PCA was 149.41° (SD ± 7.79) and the mean lateral PCA 159.37° (SD ± 6.78), with statistical significance for the female lateral PCA. No gender significant difference for the medial PCA and no significant side difference for the PCA's could be found. The ICC of the observers was r = 0.936 and 0.976 for the medial and for lateral PCA 0.957-0.984. The palmar cortical length of the distal radius was significantly longer in male specimens. For all widths, larger values for male radii were measured, being statistically significant in all cases. CONCLUSION: Male dimensions concerning the wide were significantly larger when compared with females. Regarding the PCA at the medial and lateral column, we found significant difference for lateral PCA concerning the gender. Overall, study results demonstrated an angle of 148.25° ± 6.83 for the medial PCA and 156.07° ± 7.00 for the lateral PCA.

Anatomic relations between the lateral collateral ligament and the radial head: implications for arthroscopic resection of the synovial fold of the elbow.

PURPOSE: The purpose of this study was to determine the anatomic relationship between the radial head and the lateral collateral ligament (LCL) and when the LCL would be at risk of iatrogenic injury during arthroscopic resection of the synovial fold. METHODS: Thirty-four formalin-fixed upper extremities were dissected. A projection of the LCL onto the radial head was marked with a needle. The percentage of the posterior border of the radial head overlaid by the LCL was digitally measured. A portion of the projection of the LCL was statistically correlated with the overall diameter of the radial head. RESULTS: The overall diameter of the radial head was 21.2 mm ± 2.3. The proportionate projection of the medial border of the LCL onto the radial head was 5.3 ± 1.6 mm on average. The lateral 25 % of the radial head was overlaid by the LCL with a maximum value of 40 % on average. The inter- and intraobserver reliability showed very good accordance with the digital measurements (r > 0.8). CONCLUSION: Care must be taken when performing a resection in the lateral 40 % of the radial head, whereas resection in the medial 60 % of the radial head appears to be safe. The LCL is an important stabiliser of the elbow joint, a lesion of which by undeliberate arthroscopic dissection may lead to joint instability. Iatrogenic injury to the LCL presumably can be prevented when respecting the given data. LEVEL OF EVIDENCE: Experimental study.

Anatomical fit of seven different palmar distal radius plates.

INTRODUCTION: The purpose of this study was to compare the anatomical fit of different, precontoured palmar distal radius plates. METHODS: The anatomical fit of seven different types of palmar distal radius plates [Königsee variable fixed-angle radius plate 7/3-hole, Königsee variable fixed-angle radius plate 5/3-hole (Allendorf, Germany), Medartis 2.5 Adaptive TriLock, Medartis 2.5 TriLock, Medartis 2.5 TriLock extraarticular, (Basel, Switzerland), Synthes VA-LCP distal two-column-radius, Synthes LCP extraarticular (Bettlach, Switzerland)] were investigated in 25 embalmed human cadaveric radii. An imprint of the space between the well-positioned plate and the distal radius was attained using a silicone mass and the maximum height of the silicone imprint was digitally measured. The mean maximum imprint height was compared between the seven plates using an analysis of variance with repeated measures and Bonferroni correction for multiple comparisons. RESULTS: The mean maximum distance between the plates and the radial cortex was <2 mm for all plates. The greatest difference was found with the Medartis Adaptive (1.99 ± 0.45 mm) and the least difference with the Synthes two-column (1.56 ± 0.76 mm), this difference being statistically significant (p = 0.005). CONCLUSION: Although there was no complete congruency between the plates and the radial cortex, all distal palmar radius plates investigated in this study presented a reasonable anatomical shape. The Synthes VA-LCP distal two-column-radius plate palmar showed the best anatomical fit. A low profile and optimized anatomical precontouring minimizes irritation of the surrounding soft tissues and should be considered with plate design and implant choice.

Matrilin-1 is essential for zebrafish development by facilitating collagen II secretion.

Matrilin-1 is the prototypical member of the matrilin protein family and is highly expressed in cartilage. However, gene targeting of matrilin-1 in mouse did not lead to pronounced phenotypes. Here we used the zebrafish as an alternative model to study matrilin function in vivo. Matrilin-1 displays a multiphasic expression during zebrafish development. In an early phase, with peak expression at about 15 h post-fertilization, matrilin-1 is present throughout the zebrafish embryo with exception of the notochord. Later, when the skeleton develops, matrilin-1 is expressed mainly in cartilage. Morpholino knockdown of matrilin-1 results both in overall growth defects and in disturbances in the formation of the craniofacial cartilage, most prominently loss of collagen II deposition. In fish with mild phenotypes, certain cartilage extracellular matrix components were present, but the tissue did not show features characteristic for cartilage. The cells showed endoplasmic reticulum aberrations but no activation of XBP-1, a marker for endoplasmic reticulum stress. In severe phenotypes nearly all chondrocytes died. During the early expression phase the matrilin-1 knockdown had no effects on cell morphology, but increased cell death was observed. In addition, the broad deposition of collagen II was largely abolished. Interestingly, the early phenotype could be rescued by the co-injection of mRNA coding for the von Willebrand factor C domain of collagen IIα1a, indicating that the functional loss of this domain occurs as a consequence of matrilin-1 deficiency. The results show that matrilin-1 is indispensible for zebrafish cartilage formation and plays a role in the early collagen II-dependent developmental events.

Micromechanical function of myofibrils isolated from skeletal and cardiac muscles of the zebrafish.

The zebrafish is a potentially important and cost-effective model for studies of development, motility, regeneration, and inherited human diseases. The object of our work was to show whether myofibrils isolated from zebrafish striated muscle represent a valid subcellular contractile model. These organelles, which determine contractile function in muscle, were used in a fast kinetic mechanical technique based on an atomic force probe and video microscopy. Mechanical variables measured included rate constants of force development (k(ACT)) after Ca(2+) activation and of force decay (τ(REL)(-1)) during relaxation upon Ca(2+) removal, isometric force at maximal (F(max)) or partial Ca(2+) activations, and force response to an external stretch applied to the relaxed myofibril (F(pass)). Myotomal myofibrils from larvae developed greater active and passive forces, and contracted and relaxed faster than skeletal myofibrils from adult zebrafish, indicating developmental changes in the contractile organelles of the myotomal muscles. Compared with murine cardiac myofibrils, measurements of adult zebrafish ventricular myofibrils show that k(ACT), F(max), Ca(2+) sensitivity of the force, and F(pass) were comparable and τ(REL)(-1) was smaller. These results suggest that cardiac myofibrils from zebrafish, like those from mice, are suitable contractile models to study cardiac function at the sarcomeric level. The results prove the practicability and usefulness of mechanical and kinetic investigations on myofibrils isolated from larval and adult zebrafish muscles. This novel approach for investigating myotomal and myocardial function in zebrafish at the subcellular level, combined with the powerful genetic manipulations that are possible in the zebrafish, will allow the investigation of the functional primary consequences of human disease-related mutations in sarcomeric proteins in the zebrafish model.