SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The basic principles of orthopedic repair are the same for small exotic mammals as for the canine or feline patient. This article assists the clinician in determining the most appropriate method of fixation and maximizes the probability of a favorable outcome.
Ultra high molecular weight polyethylene (UHMWPE) used in orthopedic prosthesis is often sterilized with gamma-rays and the subsequent oxidation was suggested to favor the in vivo wear. UHMWPE debries produced by wearing trigger an inflammatory response that can led to the implant failure. To explore direct effects of UHMWPE oxidation on immunocompetent cells and their possible role in the prosthesis failure, peripheral blood cells (PBCs) have been grown for 24 and 48 h onto plastic (Ct), UHMWPE (PE) and heat oxidized UHMWPE (PEOx) discs. PBCs necrosis and apoptosis were assessed in flow cytometry using propidium iodide staining. After 24 h, no statistically significant differences were observed in the amount of apoptotic and necrotic cells between Ct, PE and PEOx samples while, after 48 h, both necrotic and apoptotic cells were strongly increased in PEOx samples where also the granulocytes population appeared strongly reduced (6.3+/-1.1%) compared to PE (10.5+/-1.5%) and Ct (15.1+/-0.9%) samples. We conclude that surface oxidation may interfere with prosthetic failure and/or integration via granulocytes modulation.
Bone cement is subjected to multi-axial cyclic loading when used to fixate orthopedic prostheses for joint arthroplasty. In this study, tubular specimens of poly(methylmethacrylate) (PMMA) bone cement are subjected to internal pressure and cyclic axial loading to ascertain the influence of multi-axial loading on fatigue life. As expected, it was found that the probability of survival of specimens under multi-axial loading was very much reduced relative to specimens loaded uniaxially. Furthermore, the variability of the fatigue life was increased by multi-axial loading. In conclusion, the results point to the importance of characterizing the behavior of bone cements under the multi-axial fatigue experienced in vivo, and of the importance of accounting for the multi-axial stress state when predicting implant longevity.
Adult stem cells reside in adult tissues and serve as the source for their specialized cells. In response to specific factors and signals, adult stem cells can differentiate and give rise to functional tissue specialized cells. Adult mesenchymal stem cells (MSCs) have the potential to differentiate into various mesenchymal lineages such as muscle, bone, cartilage, fat, tendon and ligaments. Adult MSCs can be relatively easily isolated from different tissues such as bone marrow, fat and muscle. Adult MSCs are also easy to manipulate and expand in vitro. It is these properties of adult MSCs that have made them the focus of cell-mediated gene therapy for skeletal tissue regeneration. Adult MSCs engineered to express various factors not only deliver them in vivo, but also respond to these factors and differentiate into skeletal specialized cells. This allows them to actively participate in the tissue regeneration process. In this review, we examine the recent achievements and developments in stem-cell-based gene therapy approaches and their applications to bone, cartilage, tendon and ligament tissues that are the current focus of orthopedic medicine.
The effect of heavy continuous orthopedic forces was studied in three Saimiri Sciureus (squirrel) monkeys. Two additional monkeys served as controls. The maxillary sutures were investigated microscopically. In addition, the bone markers (tetracycline, Procion Red H-8 BS) served for quantitative evaluation under ultraviolet light. After two weeks slight remodeling activity could be observed. After one month a tremendous activity was found in the sutures. The width of the sutures was two to three times enlarged. The regular tissue pattern of the sutures had changed to a mixture of precollagen and collagen fibers running in all directions with plenty of active cells. In the ultraviolet light there is a take up of markers at the sutural margins. After three months of treatment though, the sutures showed a similar pattern. The three zones of the sutures began to form again; osteoblasts were attached to the sutural margins and reorganization was relatively complete.
The classical effects of lateral orthopedic stress on the midpalatal suture were confirmed in this study conducted on ten female Macaca mulatta monkeys in the mixed dentitional period. The suture was opened with consequent expansion of the maxillary arch, of the intranasal space, and of the palatal vault. There was marked buccal displacement of the upper posterior teeth together with a definite broadening of the entire midface. Modest relapse of maxillary expansion and of palatal depth occurred when retention was terminated after four months. Normal angulation of the upper first molars at the end of the experimental period is indicative of a predominantly translatory expansion of the arch or of a rapid restoration of normal tooth alignment and inclination. Subsidiary expansion of the mandibular arch and reclosure of the midpalatal suture also occurred. Of particular importance to this study was confirmation of changes in the bony configuration of the midface manifested by prominence of the canine eminence and the general pug-nosed appearance of treated animals althrough this could not be attributed to retrusion of the premaxilla.
Heavy, interupted orthopedic forces were employed for the cervical retraction of the maxillae in two Macaca mulatta monkeys. The nature, location and magnitude of resultant movements and remodelling were studied with the help of plaster casts, amalgam implants, lateral cephalometric tracings, and of gross and microscopic study of the skulls themselves. The principal effect of the retractive force was a marked downward and backward rotational movement of the maxillae which carried the maxillary teeth into posterior crossbite and a severe Class III molar relationship. Posterior movement of the tuberosity entirely closed the pterygomaxillary fissure so that the tuberosity impinged upon the pterygoid plates. Like the maxillae, the mandible, premaxilla, and nasal boned also moved downward and backward. These changes increased the vertical dimension of the face and diminished it horizontally leaving a flattened facial profile from the nasal opening to the maxillary incisors. Movement of facial elements posteriorly against an unhielding anterior cranial base imposed a number of other compensatory changes. These included generalized resorption at the craniofacial sutures and sliding of the sutures upon each other. They also involved mutual resorption of the maxillary tuberosity and of the pterygoid plates together with remodelling and lateral extension of the malar bones. Tolerance of the animals and of the localized tissues for these intensive forces suggests a significant role for this form of therapy. Clinical application, however, should be tempered by judicious concern for the vital structures of the pterygomaxillary fissure which could be impinged or strangulated by excessive retrusive force.
In this study 30 patients exhibiting mandibular prognathism were treated by the orthopedic chin-cup appliance for a three-year period. The patients began treatment at the age of six years and completed treatment at the age of nine years. As previously reported, chin-cup treatment resulted in a "clockwise" facial rotation with the mandible moving relatively posteriorly and inferiorly. Hyoid position measured in this study also tended to move slightly posteriorly but was primarily displaced in an inferior direction. The positional alteration exceeded in amount what might have been expected by growth alone. The inferior direction of change in hyoid and associated structures and the resultant lack of encroachment on the vital pharyngeal passageways suggests that stability and patency of the pharyngeal airway is a primary factor in hyoid positioning. The duration and "growth guidance" aspects of treatment allowed for functional as well as morphologic adaption to the altered hyoid position.
A detailed description of the fabrication and use of a maxillary orthopedic prosthesis for the newborn cleft palate patient, from impression through parental management of the appliance.
The present study was designed to investigate biomechanical and clinical changes in the craniofacial complex resulting from orthopedic maxillary protraction by means of finite element and cephalometric analyses, respectively. An analytical model developed from a young human dry skull was used for finite element analysis. Three principal stresses were determined in the complex and its sutures. For evaluating morphological changes of patients, lateral cephalograms taken before and after maxillary protraction therapy were analyzed. Tensile stresses were produced in the maxillary and zygomatic bones in an anterior direction with corresponding compressive stresses in a perpendicular direction. In the sutural systems, compressive stresses were induced by counter-clockwise rotation of the complex. Cephalometric investigation demonstrated that significant improvement of the maxillo-mandibular relationship was obtained by maxillary protraction, however, maxillary growth and repositioning were not as great when compared to mean growth in the control group.
This study was designed to investigate biomechanical responses of the sutures in the nasomaxillary complex to orthopedic headgear forces applied in various directions. A three-dimensional analytic model of the craniofacial complex was used for finite element analysis. A posteriorly-directed force of 1.0 Kgf was applied to the maxillary first molars in 30 degrees inferior, parallel, and 30 degrees, 52.4 degrees and 60 degrees superior directions to the functional occlusal plane. Mean principal and shear stresses were evaluated at the sphenozygomatic, temporozygomatic, sphenomaxillary, frontomaxillary and frontozygomatic sutures and lamina cribrosa. As the force direction passed closer to the center of resistance (CRe) of the complex (52.4 degrees superior direction). normal stresses approached a certain level of uniform compressive stress (-2.5 gf/mm2) with gradual decrease in shear stresses, whereas variation in these stresses produced by the forces applied in other horizontal and inferior directions was greater. It is shown that stresses in the nasomaxillary sutures are varied by the direction of headgear force. Directing the line of force closer the CRe may produce the most optimal sutural modification effective for controlling forward and downward maxillary growth.
Mandibular deficiency may be a factor in reduced oropharyngeal airway (OAW) dimensions and related impaired respiratory function. The purpose of this study was to evaluate the use of functional-orthopedic devices in increasing OAW dimensions in children with Class II skeletal patterns (ANB > 4) and clinically deficient mandibles. Comparisons were made between two groups, one comprising 26 treated patients and the other comprising 15 controls. Student's t-tests, paired t-tests, discriminant analyses, and Pearson's r-correlation coefficients were performed to evaluate group differences and to search for characteristics that might suggest which patients would be better candidates for significant increase in OAW dimensions. Compared with controls, OAW dimensions increased significantly in treated patients, especially those with sagittally smaller and more retrognathic maxillomandibular complexes and smaller OAW dimensions.
Apert's syndrome is a developmental malformation characterized by: craniosynostosis, a cone-shaped calvarium, midface hypoplasia, pharyngeal attenuation, ocular manifestations, and syndactyly of the hands and feet. The prodromal characteristic for the typical craniofacial appearance is early craniosynostosis of the coronal suture, the cranial base, and an agenesis of the sagittal suture. These craniofacial characteristics predispose the patient to maxillary transverse and sagittal hypoplasia with concomitant dental crowding, a maxillary pseudocleft palate, and a skeletal and dental anterior open bite. This is a case report of an Apert's syndrome patient with a discussion of the orthodontic and dentofacial orthopedic considerations that influenced the treatment plan.
Forty consecutively referred children, 20 boys and 20 girls, with a Class II division I malocclusion and protrusive maxilla were treated with orthopedic cervical headgear with a 10 mm expanded inner bow and a long outer bow bent 15 degrees upwards. The mean age of the children at the beginning of treatment was 9.3 years (SD 1.3, range 6.6 to 12.4 years), and the average treatment time was 1.8 years (SD 0.6, range 0.8 to 3.1 years). In all patients Class II molar relationships were successfully corrected to Class I molar relationships. This was accompanied by a marked widening of both maxillary and mandibular dental arches. The cephalometric analysis suggested that the observed improvement of the occlusion was due to an inhibition of forward growth of the maxilla and anterior downward rotation of the palate.
The purpose of this study was to analyze the stress distribution patterns within the craniofacial complex during rapid maxillary expansion. Therefore, a finite element model of a young human skull was generated using data from computerized tomographic scans of a dried skull. The model was then strained to a state of maxillary expansion simulating the clinical situation. The three-dimensional pattern of displacement and stress distribution was then analyzed. Maximum lateral displacement was 5.313 mm at the region of upper central incisors. The inferior parts of the pterygoid plates were also markedly displaced laterally. But there was minimum displacement of the pterygoid plates approximating the cranial base. Maximum forward displacement was 1.077 mm and was seen at the region of the anteroinferior border of the nasal septum. In the vertical plane, the midline structures experienced a downward displacement. Even the ANS and point A moved downward. The findings of this study provide some additional explanation of the concept of correlation between the areas of increased cellular activity and the areas of dissipation of heavy orthopedic forces. Therefore, the reason for the occurrence of sensation of pressure at various craniofacial regions, reported by the patients undergoing maxillary expansion could be correlated to areas of high concentration of stresses as seen in this study. Additionally, the expansive forces are not restricted to the intermaxillary suture alone but are also distributed to the sphenoid and zygomatic bones and other associated structures.
Class-II, division-1 malocclusion appears to be associated with a narrow maxilla. A Class-II malocclusion may be corrected to a Class-I relationship in children using a cervical headgear provided that the narrow maxilla is expanded. This expansion is possible using headgear by dental cast analysis, but this has not been confirmed by cephalometry. We studied the effects of orthopedic cervical headgear on dental and skeletal facial widths in 40 children aged 9.1 (7.2-11.5) who had Class-II, division-I malocclusions. The headgear consisted of a long outer bow bent 15 degrees upward and a large inner bow expanded by 10 mm. Posteroanterior cephalographs and dental casts were taken before and after treatment. The results were compared with the control values presented in the literature. The malocclusion was treated to a Class-I relationship in all children. The average treatment time was 1.6 (0.3-3.1) years. The maxilla was widened significantly (P < .0001). The upper first molar width (um-um) and maxillary width (mx-mx) increased 3.2 and 1.6 mm/y, respectively. Maxillary widening was also observed in the nasal structure as indicated by an increase in lateronasal width (lap-lap) by 1.0 mm/y (P < .005). With maxillary widening, the mandibular dental arch widened spontaneously. The lower first molar width (lm-lm) increased 0.8 mm/y, which was more than the increase in the controls (P < .0001). However, the antegonial width (ag-ag) remained unaffected. By using a widened inner bow in headgear therapy with Class-II malocclusions, a widening of maxilla and nasal cavity may be obtained.
Multipurpose titanium miniplates were placed on the lateral nasal wall of the maxilla as anchorage for face mask protraction in an 11-year-old girl presenting with severe maxillary hypoplasia and hypodontia. Applying orthopedic forces directly to the maxilla resulted in an eight mm maxillary advancement. Intraosseous titanium screws were also placed on the palatal bone, near the alveolar crests, to provide anchorage for the expansion appliance. The maxilla was expanded from the median palatal suture, and seven mm of expansion was achieved across the buccal segments. No other tooth support was used for the expansion or the protraction of the maxilla.
Adverse effects of the transfusion of homologous blood on tumor recurrence and resistance to bacterial infection have been reported previously, but the findings are inconclusive. A retrospective review of patients undergoing orthopedic surgery was conducted, and the rate of the postoperative infectious complications was compared among those receiving homologous blood, autologous blood, both types, or no transfusion support. An overall postoperative infection rate of 6.1 percent was observed: 6.9 percent among persons receiving homologous blood, 5.0 percent among those receiving autologous blood, 11.9 percent among those receiving both homologous and autologous blood, and 4.9 percent among those not receiving transfusions (p = 0.37). Among patients receiving homologous blood, a subset of 15 patients received homologous whole blood and had an infection rate of 20 percent. Significant predictors of postoperative infection included increasing age, spinal surgery, high admission hematocrit, and greater time in surgery. Of factors relating to transfusion, only the use of homologous whole blood was a significant predictor of postoperative infection, which suggests a detrimental effect of homologous plasma. It can be concluded that, in this group of patients undergoing relatively nontraumatic surgery, several variables that are not related to transfusion, as well as the use of homologous whole blood, were significant predictors of postoperative infection.