Supracondylar femur osteotomies around the knee: patient selection, planning, operative techniques, stability of fixation, and bone healing.

BACKGROUND: Similar to the re-appreciation of high tibial osteotomy (HTO), supracondylar distal femur varus osteotomy (SCO) for lateral compartment osteoarthritis (OA) of the knee has gained renewed interest as new knowledge has become available on the influence of malalignment on the development, progression and symptoms of OA. Furthermore, the less than optimal results of knee replacements (TKR) in younger patients have also led to renewed interest in joint-preserving treatment options. PURPOSE: Varus SCO has not had the same success or widespread use as valgus HTO. The goal in SCO is similar to HTO, to shift the load from the diseased to the healthy compartment, in order to reduce pain, improve function and delay placement of a TKR. Valgus OA however occurs much less frequently than varus OA and varus SCO is considered a technically more demanding procedure. In the past the surgical techniques for SCO were mainly dependent on difficult-to-use implants making the procedure more complex. Complication rates related to the failure of fixation up to 16% have been reported. DISUSSION: The new biplane osteotomy technique fixated with a locking compression plate is very stable; bone healing potential is optimal using this technique and takes 6-8 weeks. Full weight bearing before full bone healing is possible without loss of correction. CONCLUSION: In this article, patient selection, planning, surgical techniques, stability of fixation, and bone healing are discussed. Varus supracondylar osteotomy is a viable treatment option for a well-defined patient group suffering from valgus malalignment and lateral compartment osteoarthritis, and in addition may be considered in ligamentous imbalance and lateral patellofemoral maltracking.

[Supracondylar femur osteotomies around the knee. Patient selection, planning, operative techniques, stability of fixation, and bone healing]. / Suprakondyläre Femurosteotomien in Kniegelenknähe. Patientenauswahl, Planung, Operationstechniken, Fixationsstabilität und Knochenheilung.

BACKGROUND: Similar to the reappreciation of high tibial osteotomy (HTO), supracondylar distal femur varus osteotomy (SCO) for lateral compartment osteoarthritis (OA) of the knee has gained renewed interest as new knowledge has become available on the influence of malalignment on the development, progression and symptoms of OA. Furthermore, the less than optimal results of total knee replacement (TKR) in younger patients have also led to renewed interest in joint-preserving treatment options. PURPOSE: Varus SCO has not had the same success or widespread use as valgus HTO. The goal in SCO is similar to HTO, to shift the load from the diseased to the healthy ompartment, in order to reduce pain, improve function and delay placement of a TKR. Valgus OA however occurs much less frequently than varus OA and varus SCO is considered a technically more demanding procedure. In the past the surgical techniques for SCO were mainly dependent on difficult-to-use implants making the procedure more complex. Complication rates related to the failure of fixation up to 16 % have been reported. DISUSSION: The new biplane osteotomy technique fixated with a locking compression plate is very stable; bone healing potential is optimal using this technique and takes 6-8 weeks. Full weight bearing before full bone healing is possible without loss of correction. CONCLUSION: In this article patient selection, planning, surgical techniques, stability of fixation and bone healing for SCO are discussed. In the past the surgical techniques for SCO were mainly dependent on difficult to use implants making the procedure more complex. Complication rates related to the failure of fixation of up to 16 % have been reported.

Axial and torsional stability of an improved single-plane and a new bi-plane osteotomy technique for supracondylar femur osteotomies.

PURPOSE: An important disadvantage of the standard medial closing-wedge distal femur osteotomy for lateral compartment osteoarthritis of the knee is the immediate effects on the extensor mechanism function. Therefore, a novel bi-plane osteotomy technique was developed. The stability and stiffness of this newly developed technique and a modification of the proximal screw configuration were tested in a composite femur model and compared to the standard single-plane technique. Research question was if the new bi-plane technique and/or modified screw configuration would improve the stability and stiffness of the construct. METHODS: In 12 femurs, motion at the osteotomy under axial and torsion loading was measured using a 3D motion analysis system. All were subsequently tested to failure. The data recorded were used to calculate stability and stiffness of the constructs. RESULTS: The stability and stiffness were highest in the bi-plane technique under axial loads, but were lower under torsional loading, compared to the single-plane technique. The screw configuration modification improved axial stability and stiffness, but had no influence on torsional stability. CONCLUSION: In replicate femurs, the new bi-plane technique improved axial stability, but in contrast to what was theorized, decreased torsional stability, compared to the single-plane technique. The addition of a bi-cortical screw proximally improved stability under axial loading, but not torsion. Further clinical testing will have to prove if early full weight bearing using the new bi-plane technique is possible.

[Osteotomies of the knee joint in patients with monocompartmental arthritis]. / Osteotomien am Kniegelenk bei Monokompartmentarthrose.

The basic principles of biomechanics, patient selection, proper planning, safe intraoperative technique with stable osteosynthesis, and early functional rehabilitation are the key factors for successful osteotomies around the knee. An individual unloading of the involved compartment should be the goal of this procedure. Several different osteotomy techniques have been described in the past. On the tibia, the modern open-wedge osteotomies offer significant advantages compared with the classical closed-wedge osteotomies. At the femur, closed-wedge medial and lateral osteotomies for varus and valgus malalignment are still the standard. Except for a few studies with selected patients, the long-term results of osteotomies around the knee are worse compared with the outcomes of unicondylar joint replacements. With the use of new biomechanical concepts together with modern osteosynthesis, osteotomy results can improve significantly. Therefore, osteotomies around the knee remain the gold standard for middle-aged and active elderly patients with monocompartmental arthritis of the knee.

Osteotomies around the knee: patient selection, stability of fixation and bone healing in high tibial osteotomies.

New developments in osteotomy techniques and methods of fixation have caused a revival of interest of osteotomies around the knee. The current consensus on the indications, patient selection and the factors influencing the outcome after high tibial osteotomy is presented. This paper highlights recent research aimed at joint pressure redistribution, fixation stability and bone healing that has led to improved surgical techniques and a decrease of post-operative time to full weight-bearing.

The labile iron pool in hepatocytes: prooxidant-induced increase in free iron precedes oxidative cell injury.

The labile iron pool (LIP) represents the nonferritin-bound, redox-active iron that has been implicated in oxidative stress and cell injury. Here we examined whether alterations in LIP can be detected in cultured murine hepatocytes and whether increases in LIP are related to the oxidative damage inflicted by the redox cycling drug nitrofurantoin (NFT). Early changes in LIP were monitored with the metal-sensitive fluorescent probe calcein (CA), the fluorescence of which is quenched on binding to iron. Short-term exposure (<1 h) to NFT reduced the CA fluorescence signal by 30%, indicating that the amount of LIP-associated iron had increased. Prolonged exposure (2 h) to NFT caused oxidative cell injury. The addition of the cell-permeable ferrous iron chelator 2,2'-bipyridyl not only prevented the quenching of CA fluorescence but also partially protected from NFT toxicity. It is concluded that reductive stress-induced increase in LIP is an essential event that precedes oxidative cell damage in intact hepatocytes.

Fluorescently detectable magnetic resonance imaging agents.

This report describes the synthesis, characterization, and in vivo testing of several bifunctional contrast-enhancing agents for optical and magnetic resonance imaging (MRI) of experimental animals. These new agents integrate the advantages of both techniques since they can be visualized simultaneously by light and MRI microscopy. Employing this strategy allows the same biological structures of a specimen to be studied at dramatically different resolutions and depths. The complexes possess a metal chelator for binding a paramagnetic ion, gadolinium (Gd3+), and a covalently attached fluorescent dye. The first class of complexes are low-molecular weight species that are composed of the macrocyclic tetraamine 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) as the metal-chelating ligand coupled to tetramethylrhodamine. The second class of MRI-enhancing agents are composed of high-molecular weight polymers that are membrane impermeable and once injected into a cell or cells are trapped inside. These complexes possess multiple copies of both the metal-chelator-diethylenetriaminepentaacetic acid (DTPA) and the tetramethylrhodamine attached to a macromolecular framework of either poly(D-lysine) (pdl) or dextran. Images acquired of single cells after injection with these bifunctional agents enabled us to follow the relative motions and reorganizations of different cell layers during amphibian gastrulation and neurulation in Xenopus laevis embryos.

Antioxidant and cytoprotective properties of D-tagatose in cultured murine hepatocytes.

D-Tagatose is a zero-energy producing ketohexose that is a powerful cytoprotective agent against chemically induced cell injury. To further explore the underlying mechanisms of cytoprotection, we investigated the effects of D-tagatose on both the generation of superoxide anion radicals and the consequences of oxidative stress driven by prooxidant compounds in intact cells. Primary cultures of hepatocytes derived from male C57BL/6 mice were exposed to the redox cycling drug nitrofurantoin (NFT). Lethal cell injury induced by 300 microM NFT was completely prevented by high concentrations (20 mM) of D-tagatose, whereas equimolar concentrations of glucose, mannitol, or xylose were ineffective. The extent of NFT-induced intracellular superoxide anion radical formation was not altered by D-tagatose, indicating that the ketohexose did not inhibit the reductive bioactivation of NFT. However, the NFT-induced decline of the intracellular GSH content was largely prevented by D-tagatose. The sugar also afforded complete protection against NFT toxicity in hepatocytes that had been chemically depleted of GSH. Furthermore, the ketohexose fully protected from increases in both membrane lipid peroxidation and protein carbonyl formation. In addition, D-tagatose completely prevented oxidative cell injury inflicted by toxic iron overload with ferric nitrilotriacetate (100 microM). In contrast, D-tagatose did not protect against lethal cell injury induced by tert-butyl hydroperoxide, a prooxidant which acts by hydroxyl radical-independent mechanisms and which is partitioned in the lipid bilayer. These results indicate that D-tagatose, which is a weak iron chelator, can antagonize the iron-dependent toxic consequences of intracellular oxidative stress in hepatocytes. The antioxidant properties of D-tagatose may result from sequestering the redox-active iron, thereby protecting more critical targets from the damaging potential of hydroxyl radical.

Sequence specificity of the non-natural pyrido[2,3-d]pyrimidine nucleoside in triple helix formation.

The non-natural pyrido[2,3-d]pyrimidine nucleoside F, which pairs preferentially with guanine (G) and adenine (A) within double-helical DNA, recognizes with high selectivity AT base pairs within triple-helical complexes. These observations suggest that F may exist in different tautomeric forms within double-helical and triple-helical complexes. Analysis of the base stacking properties of this extended ring system using two oligodeoxyribonucleotides containing terminal thymines and/or pyrido[2,3-d]pyrimidines bound to adjacent sites showed a decrease in free energy of binding in a triple-helical complex in the order (5'-3') TT > FT > TF > FF.

[Differential diagnosis and therapy of multi-fragment humeral head fracture--an analysis of three clinical studies]. / Differentialdiagnostik und -therapie der mehrfragmentären Humeruskopffraktur--eine Analyse aus drei klinischen Studien.

Out of the total number of patients of three Centers for Orthopaedic and Trauma Surgery, 93 comminuted humeral head fractures were clinically and radiologically controlled by means of a retrospective analysis. The classification of the fractures was made according to C.S. Neer, the clinical evaluation according to the Constant-Score. The analysis of the results in relation to the respective therapeutic methods revealed fundamental differences between the various types of fractures depending on the number of fragments. The prognosis of the three-part fractures appears essentially determined by the biomechanical conditions. This means that the therapeutic method has to be applied according to the restitution of the respective position of the fragments. Open reduction and internal fixation (mean Constant-Score 83 resp 91 points) or conservative treatment (78 points) seem to be primarily indicated in these cases. The prognosis of the four-part fractures, on the contrary, is largely determined by the problems of vascular supply of the head fragment, with a high risk of a humeral head necrosis. For this reason a primary prosthetic replacement (mean Constant-Score in case of primary implantation 75 points, compared with 54 points in case of conservative treatment and 52 points for open reduction and internal fixation), should be recommended for this type of fracture. For therapeutic and prognostic reasons, fractures at the proximal end of the humerus require an exact classification on the radiological basis of at least a so-called "trauma series". However, for a more accurate visualisation especially of the region of the lesser tuberosity (which is difficult to assess by means of conventional radiology), and consequently for the precise determination of the number of fracture-parts and their respective positions, we consider a CT Scan to be compulsory.

Enzyme thermoinactivation in anhydrous organic solvents.

Three unrelated enzymes (ribonuclease, chymotrypsin, and lysozyme) display markedly enhanced thermostability in anhydrous organic solvents compared to that in aqueous solution. At 110-145 degrees C in nonaqueous media all three enzymes inactivate due to heat-induced protein aggregation, as determined by gel filtration chromatography. Using bovine pancreatic ribonuclease A as a model, it has been established that enzymes are much more thermostable in hydrophobic solvents (shown to be essentially inert with respect to their interaction with the protein) than in hydrophilic ones (shown to strip water from the enzyme). The heat-induced aggregates of ribonuclease were characterized as both physically associated and chemically crosslinked protein agglomerates, with the latter being in part due to transamidation and intermolecular disulfide interchange reactions. The thermal denaturation of ribonuclease in neat organic solvents has been examined by means of differential scanning calorimetry. In hydrophobic solvents, the enzyme exhibits greatly enhanced thermal denaturation temperatures (T(m) values as high as 124 degrees C) compared to aqueous solution. The thermostability of ribonuclease towards heat-induced denaturation and aggregation decreases as the water content of the protein powder increases. The experimental data obtained suggest that enzymes are extremely thermostable in anhydrous organic solvents due to their conformational rigidity in the dehydrated state and their resistance to nearly all the covalent reactions causing irreversible thermoinactivation of enzymes in aqueous solution.

[Functional results of Neer II type hemi-arthroplasty joint replacement of multi-fragment humerus head fractures]. / Funktionelle Resultate nach hemiarthroplastischem Gelenksersatz Typ Neer II von mehrfragmentären Humeruskopffrakturen.

Among the fractures of the proximal humerus--a typical kind of injury affecting elderly people, as well as gainfully employed patients, the comminuted and dislocated humeral head fractures have a specific position because of therapeutical reasons. By means of a retrospective analysis, a review is given of the results of 26 comminuted humeral head fractures type IV-VI according to Neer, treated with a Neer prosthesis type II at the surgical clinic of the Kantonsspital Lucerne between 1983 and 1989. Our interest is mainly concentrated on the functional results and on their correlation with biomechanical and perioperative factors. We use the fracture-classification and functional evaluation as described by Neer. For the results classified as "failures" (13 cases) the functional deficits of the glenohumeral joint mobility are essential. The scores reveal no significant correlation to the age of the patients, to the time interval between trauma and operation, as well to the duration of the postoperative physiotherapy. On the other hand the scores of patients with preoperative manipulation of the fractured joint (i.e. osteosynthesis, reduction attempts, physiotherapy) were significantly worse than those with primary prosthetic replacement. Furthermore, because of the insufficient restitution of the lever arm conditions, the implantation of the small-head component (15 mm) leads to significantly less favorable functional scores, with a corresponding radiological hyperpression in the cranial articular space. Our analysis leads to the following conclusions: 1. Under the condition of a conclusive preoperative diagnosis a primary prosthetic procedure is recommended depending on the type of fracture.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoperoxidase localization of fibronectin during odontoblast differentiation. An ultrastructural study.

Immunoperoxidase labeling of fibronectin in one-day-old mouse first lower molars allowed to visualize a striking redistribution of this glycoprotein during terminal cytodifferentiation of odontoblasts. The modifications involved both extracellular and cell surface localizations. The possible roles of these modifications in terminal differentiation of odontoblasts are discussed.

Direct visualization of an IgM directed against a membrane antigen involved in both cell-matrix interactions and microfilament organization.

Dental mesenchymal cells were cultured in the presence of a monoclonal antibody. MC16A16, consisting of IgM and directed against a hydrophobic 165 kDa protein. Since the epitope recognized by MC16A16 was found to be at the outer cell surface, a direct visualization of IgM antibodies was used to localize the 165 kDa antigen by transmission electron microscopy. The present results demonstrate that the 165 kDa antigen is a membrane protein.

Lipid detection by malachite green-aldehyde in the dental basement membrane in the rat incisor.

Developing rat incisors were treated with malachite green-aldehyde fixative solution (MGA), which retains and stains lipids. We observed positive staining occurring as dots in the basement membrane. Most of these dots (2-3.5 nm in diameter) were grouped in the lamina densa but some were also present in the lamina lucida and the lamina fibroreticularis. These data provide evidence for the existence of lipids in the dental basement membrane and suggest that they are distributed together with the various groups of proteins so far detected.

Effects of glycosaminoglycans on in vitro mouse dental cells.

Trypsin-dissociated dental papillae and enamel organs removed from the first lower molars of day-18 and day-19 mouse embryos were cultivated for 2 to 4 days on Millipore filters in DMEM supplemented with 15 per cent fetal calf serum and chondroitin sulphate and hyaluronic acid, individually or together. Three concentrations of glycosaminoglycans (GAGs) were also added to the media (01, 0.2, 0.4 mg/ml). Control cultures were made in the absence of GAGs, and additional experiments performed in which the presence of GAGs was associated with serum-free medium. Elongated and polarized odontoblasts showing synthetic activity were only observed in the presence of serum containing medium supplemented with 0.1 or 0.2 mg/ml of the GAGs. [3H]-thymidine autoradiography demonstrated that these cells were already post-mitotic at the onset of the culture. Polarized ameloblasts were never observed. These data provide evidence that GAGs are able to maintain the polarized state of cultured odontoblasts.

Ultrastructural duality of extracellular fibrillar components of the odontoblast layer in the mouse molar.

The application of detergent solutions to dissociated molar dental papillae of mice permitted precise observation of the extracellular fibrillar material in the odontoblast layer and the predentine. Two types of fibrils were identified: cross-banded fibrils of variable diameter (25-200 nm) and aperiodic microfibrils of regular diameter (12.5 nm) and undetermined length. If the collagenic nature of the cross-banded fibrils is evident, the composition of the aperiodic microfibrils is probably different.

Cell-matrix interactions: influence of noncollagenous proteins from dentin on cultured dental cells.

Matrix-mediated epitheliomesenchymal interactions control dental cytodifferentiations. Experiments were performed in order to study the effects of noncollagenous proteins extracted from dentin on cultured enamel organs and dental papillae. Seven noncollagenous protein fractions were prepared from rabbit incisor dentin and used as substrates to coat Millipore filters. Embryonic mouse tooth germs were dissociated and the isolated tissues were cultured for 4 days on these different substrates as well as on noncoated Millipore filters. When compared to control cultures, only two protein fractions affected the behaviour of epithelial cells. A slight elongation of the cell body and a preferential localization of the nuclei at the basal pole of the cells in contact with the filter was observed with protein fractions 5 and 6. When dental papillae were cultured on Millipore filters coated either with protein fraction 2 or fraction 6, the mesenchymal cells in contact with the filter elongated, polarized and demonstrated a high metabolic activity. Such modifications in the cell organization, implying changes in the cytoskeleton organization and, or, activity, never occurred spontaneously or in the presence of isolated collagens (I-V), laminin or fibronectin.

Epithelial-mesenchymal interactions: effects of a dental biomatrix on odontoblasts.

The functional differentiation of odontoblasts requires specific interactions between these cells and the extracellular matrix. To further analyze these phenomena we studied the effects of a "dental papillae biomatrix" on isolated dental papillae cultured in vitro. The dental papillae biomatrix was extracted from EDTA-dissociated day-18 mouse dental papillae by homogenization, NaCl and enzymatic treatments, and deposited on Millipore filters. This biomatrix was studied by means of transmission electron microscopy and indirect immunofluorescence: it contained collagen fibrils, type IV collagen, fibronectin and laminin; cellular residues were also observed. The dental papillae were isolated by trypsin treatment of homologous tooth germs and cultured on uncoated (control) and coated filters. As shown by histological and cytological data, odontoblast-like cells never differentiated in control cultures. In presence of biomatrix and serum, polarized functional cells were observed. The functional state of these cells was enhanced by the addition of ascorbic acid to the culture media. Study of the incorporation of 3H-proline in cultured dental papillae and in macromolecules secreted into the culture media corroborated the morphological findings.