[Can meniscal suture repair in athletes prevent early development of osteoarthritis without compromising the preinjury sports activity level]

In a retrospective study we evaluated the outcome of arthroscopic assisted meniscal repair in athletes on different competitive sports levels. Examination included early osteoarthritic changes and full recovery in sports activities. Fifty athletes were followed up with an average of 6,5 years after meniscal refixation from 1984 through 1998. Twenty-three patients had isolated full-thickness meniscal tears, twenty-seven an associated rupture of the anterior cruciate ligament. Preoperative sports levels were evaluated with Tegners score. Reexamination included Lysholm score, IKDC score and Fairbanks score. With no persisting anterior knee instability 86 % of the professional athletes returned to former full sports activities on competitive levels. Noncompetitive athletes returned in all cases (100 %) to their former level. Fairbanks score increased by 0,1 observing minimal osteoarthitic signs. However, persisting anterior knee instability showed on reexamination poor results. Only one third of all athletes were able to return to former activity levels. Osteoarthritic changes were observed in all patients. Professional athletes had the most severe osteoarthritic changes with an increase of 0,8 in the Fairbanks score. The results demonstrate that complete recovery on sports activities is not possible without reconstruction of the anterior cruciate ligament. Isolated meniscal repair shows poor results in persisting anterior knee instability and does not prevent increasing osteoarthritic changes in athletes.

Bacteriochlorophyll-dependent expression of genes for pigment-binding proteins in Rhodobacter capsulatus involves the RegB/RegA two-component system

Expression of the puf and puc operons, which encode proteins of the photosynthetic apparatus of Rhodobacter capsulatus, is regulated by oxygen. A drop in the oxygen tension in the environment leads to an increase in the levels of puf and puc mRNAs. In strains lacking bacteriochlorophyll (Bchl) due to mutations in bch genes, the rise in puf and puc mRNA levels observed on reduction of oxygen tension is much less pronounced than in wild-type cells, indicating co-regulation of the syntheses of pigments and pigment-binding proteins. Here we show that Bchl synthesis also affects the expression of the bchC gene, which codes for a subunit of bacteriochlorophyll synthase, suggesting an autoregulatory mechanism for the Bchl biosynthetic pathway. Furthermore, our data provide evidence that the RegB/RegA two-component system, which is known to play a central role in oxygen-controlled expression of photosynthesis genes, is also involved in the Bchl-dependent regulation. Mutant strains which do not synthesize RegB or RegA show similar oxygen-dependent puf and puc expression in the presence and absence of Bchl. Our results support the view that the RegB/RegA system can directly or indirectly sense whether Bchl synthesis takes place or not.

Corrosion and permanent fracture resistance of coated and conventional orthodontic wires

The corrosion processes are presumed to have negative consequences on biocompatibility, aesthetic appearance and the frictional behavior between the bracket and the guiding arch during orthodontic treatment. A group of new guiding arches are the coated orthodontic wires. The present in-vitro study investigated the corrosion behavior and permanent fracture resistance of eight coated wires of different dimensions. Five superelastic nickel titanium (NiTi) wires (Titanol Low Force River Finish Gold and Gold 2: Forestadent Corp.; Titanol Superelastic tooth colored: Forestadent Corp.; Bioforce Sentalloy longuard: GAC Corp.; NiTi Imagination: GAC Corp.), two beta-titanium-wires (TMA Low Friction longuard: Ormco Corp.; TMA Low Friction longuard Purple: Ormco Corp.) and one steel wire (Stainless Steel Imagination: GAC Corp.) were selected. For comparison reasons three uncoated arch wires (Rematitan Lite Dimple: Dentaurum Corp.; Titanol Low Force River Finish: Forestadent Corp.; Bioforce Sentalloy: GAC Corp.) were included in the investigation. Surface modifications were made of teflon, polyethylene and by ion implantation. The corrosion processes have been carried out by the use of a specialized electrochemical cell. In a second experimental series the wires were exposed to mechanical stresses. Finally, all wires were examined in a scanning electron microscope. The results indicated that teflon coating prevented the corrosion of the wires. As expected, the beta-titanium wires did not corrode either. The other wires showed rupture potentials between 187 mV and 602 mV (NHE). After mechanical stress testing the wires could be subdivided into three groups. In the first group no differences could be recognized, the second group showed changes in their crystallographic structure and in the last group the teflon coating was peeled off from the surface of the wires.

Two- or three-dimensional cast analysis in patients with cleft lip and palate?

AIM

The aim of the present study was to evaluate different two- and three-dimensional cast analyses for the assessment of maxillary dimensions in patients with complete unilateral cleft lip and palate, using a set of representative cast series.

PATIENTS AND METHOD

Consecutive casts were taken from ten patients at 1 week, and at 3, 6, and 12 months, respectively. First, cast surfaces were digitized two-dimensionally using a scanner. Subsequently, landmarks were identified on screen and the previously defined maxillary dimensions were determined automatically by computer. Additionally, three-dimensional measurements were carried out using a specialized coordinate measurement table. The differences between the respective measurements were analyzed for statistical significance.

RESULTS

The present study shows that the precision of the cast analysis is influenced above all by the quality of the casts and less by the precision of the measuring system employed. Moreover, misinterpretation of the results can be attributed to using an inappropriate reference system or to considering mean values only. When assessing linear and angular measurements located in approximately the same plane, no significant amount of additional information could be obtained by including the third dimension.

CONCLUSION

Thus, two-dimensional measurement procedures are appropriate in principle for quick, reliable cast analysis in patients with cleft lip and palate.

Skeletal and dental effects of maxillary protraction in patients with angle class III malocclusion. A meta-analysis

The aim of this study was a quantitative review of the published results concerning the treatment effects of maxillary protraction in patients with Angle Class III using the meta-analysis method. 85 articles published between 1966 and 1998 were reviewed under strict, pre-defined criteria. Of these, 12 studies presenting results of cephalometric measurements were selected for further analysis. The results of different cephalometric measurements were reviewed with Dstat 1.10 software in order to calculate a standardized treatment effect variable. The homogeneity of the variances of the different effect variables as well as a composite effect were calculated. For the latter, each individual effect variable was weighted by the reciprocal of its variance, with predefined study characteristics being used for categorical model calculations. Our results showed a significant composite effect of the therapy on the skeletal components (SNA: 1.4 degrees, composite effect = 1.11; SNB: -1.3 degrees, composite effect = -0.94; ANB: 2.6 degrees, composite effect = 1.73; lower anterior face height: 1.6 mm, composite effect = 0.85) as well as on the dental components of the face (inclination of upper incisors: 1.6 degrees, composite effect = 0.37; inclination of lower incisors: -3.7 degrees, composite effect = -0.87). However, several of the individual effect variables demonstrated a significant lack of homogeneity. Study characteristics which might possibly account for this variability were the patients' ages at the start of treatment and the combination of maxillary protraction with rapid maxillary expansion. In summary, maxillary protraction was shown to have a significant treatment effect. The meta-analysis method proved to be a valuable tool in judging the current status of a given clinical therapeutic concept.

Localization of cathepsin D in human odontoclasts. a light and electron microscopical immunocytochemical study

Odontoclasts are dentine and cementum resorbing cells whose relationship to bone resorbing osteoclasts is not clear. Like osteoclasts, they possess different cathepsins which are involved in mineralized tissue degradation during the tooth root resorption process in deciduous teeth. Whether cathepsin D, which in osteoclasts probably functions as an activator of other cathepsins, can be found in odontoclasts, has, however, not been investigated before. In order to determine its occurrence and localization, cathepsin D immunocytochemistry was applied to paraffin-embedded sections from 30 human deciduous tooth roots undergoing resorption. Using immunogold postembedding immunocytochemsitry on LR-Gold embedded specimens, the distribution of cathepsin D was investigated at the ultrastructural level. We identified tartrate-resistent acid phosphatase-positive mono- and multinuclear odontoclasts near and on the periodontal surfaces of tooth roots. Nearly all of these cells showed cytoplasmic granular cathepsin D immunoreactivity. At the electron microscopical level, gold labelling was seen on vacuoles and vesicles of the odontoclasts, which were identified as secondary lysosomes and phagosomes. Extracellularly it was seen along the ruffled border and in neighboured resorption areas of dentine and cementum. These findings indicate that cathepsin D is secreted into the resorbing area of human odontoclasts in order to participate in degradation of mineralized tooth matrix, but may also function as an activator of other proteases in lysosomal organelles.

Murine ventricular L-type Ca(2+) current is enhanced by zinterol via beta(1)-adrenoceptors, and is reduced in TG4 mice overexpressing the human beta(2)-adrenoceptor

1. The functional coupling of beta(2)-adrenoceptors (beta(2)-ARs) to murine L-type Ca(2+) current (I(Ca(L))) was investigated with two different approaches. The beta(2)-AR signalling cascade was activated either with the beta(2)-AR selective agonist zinterol (myocytes from wild-type mice), or by spontaneously active, unoccupied beta(2)-ARs (myocytes from TG4 mice with 435 fold overexpression of human beta(2)-ARs). Ca(2+) and Ba(2+) currents were recorded in the whole-cell and cell-attached configuration of the patch-clamp technique, respectively. 2. Zinterol (10 microM) significantly increased I(Ca(L)) amplitude of wild-type myocytes by 19+/-5%, and this effect was markedly enhanced after inactivation of Gi-proteins with pertussis-toxin (PTX; 76+/-13% increase). However, the effect of zinterol was entirely mediated by the beta(1)-AR subtype, since it was blocked by the beta(1)-AR selective antagonist CGP 20712A (300 nM). The beta(2)-AR selective antagonist ICI 118,551 (50 nM) did not affect the response of I(Ca(L)) to zinterol. 3. In myocytes with beta(2)-AR overexpression I(Ca(L)) was not stimulated by the activated signalling cascade. On the contrary, I(Ca(L)) was lower in TG4 myocytes and a significant reduction of single-channel activity was identified as a reason for the lower whole-cell I(Ca(L)). The beta(2)-AR inverse agonist ICI 118,551 did not further decrease I(Ca(L)). PTX-treatment increased current amplitude to values found in control myocytes. 4. In conclusion, there is no evidence for beta(2)-AR mediated increases of I(Ca(L)) in wild-type mouse ventricular myocytes. Inactivation of Gi-proteins does not unmask beta(2)-AR responses to zinterol, but augments beta(1)-AR mediated increases of I(Ca(L)). In the mouse model of beta(2)-AR overexpression I(Ca(L)) is reduced due to tonic activation of Gi-proteins.

Revision ACL reconstruction using autogenous patellar tendon graft

This retrospective study examined revision anterior cruciate ligament reconstruction using a bone-tendon-bone autograft of the patellar ligament. We followed up 44 patients (mean age 27.9 years) for an average of 41.2 months. Clinical examination with the Lachmann and pivot shift tests showed clearly improved stability; KT-1000 arthrometer measurements had a mean difference of 3.5 mm in side-to-side comparison. The evaluated knee scores were significantly improved (P<0.01); the median Lysholm score was 85 and the median Tegner activity score 5.0 at follow-up. In the IKDC ranking system 75.0% of knees were rated normal or nearly normal (grades A and B). According to a modified Fairbank scale, progression of radiographic signs of osteoarthritis was noted in 36.4%. There was a significant difference (P<0.05) in progression of radiographic signs of osteoarthritis between patients with major (grades III, IV) versus minor (grades I, II) lesions of the articular cartilage surface and between knees with versus without extensive synovitis due to previous synthetic graft reconstruction (P<0.05). Revision anterior cruciate ligament reconstruction using an autogenous patellar tendon graft shows good results with improved knee function compared to the prerevision status and is in line with various operative techniques described in the literature. Progression of osteoarthritis must be expected in patients with major lesions of the articular cartilage surface and knees with long-term extensive synovitis due to previous anterior cruciate ligament reconstruction using synthetic grafts.

Construction and testing of a computer-based intraoral laser scanner for determining tooth positions

An optical set-up for intraoral data acquisition based on the principle of laser triangulation was developed. The system consists of a pig-tailed laser with line generating optics, a stepping motor driven positioning stage, a commercial CCD (charge coupled device) camera system with frame grabber interface, a control personal computer and a mirror system compensating for the fact that there is no possibility of watching an object directly in the mouth under a certain angle except from a facial position during intraoral scanning. Due to the size of the prototype measurements were still restricted to plaster casts. In order to evaluate its accuracy, the measurements were compared with those taken with a commercial laser scanner and a coordinate measurement table. The accuracy of the prototype scanner was determined to be DeltaXYZ=0.04 mm using gauge blocks of given dimensions and proved to range between the commercial laser scanner and the coordinate measurement table (i.e., it was slightly better than that of the commercial scanner). Applications in orthodontics were demonstrated by scanning plaster casts and measuring distances on reconstructed surfaces. The measured distances showed a maximum deviation of about +/-0.2 mm compared with the data of the coordinate measurement table, which served as a reference. In addition, reconstruction of three-dimensional tooth movements was performed on the scan data. The translational and rotational parameters gained from the superimposition of scanned point clouds and describing tooth movement were also in good accordance with the reference. The achieved accuracy proved to be sufficient for further development which should include a reduction in size and the use of more precise device components.

[Testing a computer-assisted bending machine for manufacturing orthodontic treatment elements]

The use of suitable orthodontic devices producing desired defined force systems is of importance for successful orthodontic treatment. Bending loops can be difficult and time-consuming. Computerised fabrication would enable very precise reproduction of individual loops. A bending machine has now been developed within the framework of a computer-assisted treatment concept. In this study, a prototype machine was used to fabricate U-, T- and delta loops made of stainless steel, cobalt chromium and titanium molybdenum wire. The various geometric parameters of each loop were measured to determine how precisely they had been produced. Furthermore, the force system of each loop were experimentally investigated during simulated activation in an orthodontic measurement and simulation system. The results indicate that the geometric parameters had an average error of 2.8 degrees for angles and 0.9 mm for lengths. Owing to the fabrication errors, loops of the same type produced different force systems. Overall, the new bending machine can fabricate different types of loop, but the requirements of very precise fabrication are currently not met. This fact, together with further limitations in terms of configuration, means that the machine cannot be used routinely at present. However, the machine can nevertheless be considered a good basis for further development.

[Can meniscus refixation prevent early development of arthrosis in the knee joint? Long-term results]

This retrospective study presents the long-term results after meniscal repair with emphasis on early-development of osteoarthritis in the knee. From 1984 to 1996 meniscal repair using the inside-out technique was performed on 54 patients. 25 patients had an isolated tear of the meniscus and 29 additionally a tear of the anterior cruciate ligament (ACL, combined injury). 18 patients of those with a combined injury showed a stable knee during clinical follow-up. A separate evaluation of this group was carried out. The mean follow-up was 6.4 years. 22 patients were examined over a period of 2-5 years (mean 3.5) after surgery, 32 patients after 5 years (mean 8.9). The clinical evaluation was carried out using IKDC, Tegner activity scale, Lysholm, and Tapper and Hoover-Score as well as the Fairbank radiographic evaluation. According to the Fairbank's evaluation the results show that up to 5 years after meniscal repair only minimal radiographic changes were detectable. In only 21% of patients with an isolated meniscal lesion and in 13% of those with a stable knee after a combined injury beginning of osteorathritic changes were noted more than 5 years postoperatively. Early osteoarthritic changes were present within 5 years after surgery in non-stable knees (untreated rupture, suturing). Patients with meniscal repair mostly regain their original Tegner activity level and good to very good results in the clinical scores. However, the results clearly indicate that the success of meniscal repair depends on the stability of the knee. Thus, meniscal repair in stable knees is recommended to prevent early development of osteoarthritis.

Application of bone remodeling theories in the simulation of orthodontic tooth movements

A numerical model that calculates bone apposition and resorption around a tooth root on the basis of bone remodeling theories was developed to simulate orthodontic tooth movements. The model was used to calculate different kinds of orthodontic tooth movements, that were then compared with the expected movements based on clinical experience. For simulation of the movements the root of a canine was modeled in an idealized way in the form of an elliptical paraboloid and was processed with a finite element program. The finite element model was loaded with defined force systems. Two model assumptions were used to calculate the bone remodeling process. The mechanical loads firstly in the periodontal ligament and secondly in the alveolar bone were taken to simulate the following tooth movements: 1. mesial tipping around the center of resistance (force system at the bracket: isolated torque MY = 5 Nmm), 2. rotation around the long axis of the tooth (MZ = 5 Nmm), 3. uncontrolled tipping around the root tip (FX = 1 N, MZ = 5 Nmm), 4. canine retraction (FX = 1 N, MY = -9.5 Nmm, MZ = 5 Nmm), 5. and 6. extrusion/intrusion (FZ = +/- 0.5 N, MX = +/- 2.5 Nmm). Comparison with clinical experience was performed by calculating the orthodontic tooth movements based on the assumption of a fixed position of the center of resistance. It could be demonstrated that the numerical model of orthodontic bone remodeling can be used to calculate orthodontic tooth movements. However, the results are strongly dependent on the model assumptions. The model simulating the bone remodeling on the basis of the loading of the periodontal ligament delivers results that are in very good accordance with the biomechanical assumptions of the position of the center of resistance. However, marked side effects occurred with the second model, especially in the simulations of uncontrolled tipping, translation and intrusion/extrusion. Clinically, these side effects cannot be observed.

In vivo and in vitro analysis of RegA response regulator mutants of Rhodobacter capsulatus

In the facultative photosynthetic bacterium Rhodobacter capsulatus, the transcription of genes encoding pigment binding proteins is tightly regulated in response to the oxygen partial pressure by the RegB/ RegA two component system. After a shift from high to low oxygen tension, the response regulator RegA enhances transcription of the puf and puc operon coding for the reaction center, light-harvesting complex I (LHI), and LHII proteins. Various regA mutant strains were analyzed in this study. In a RegA deficient strain, activation of puf and puc transcription is severely impaired which consequently leads to the synthesis of only a few photosynthetic complexes. Strains carrying a mutation in the helix-turn-helix domain of RegA or a mutation of the phosphorylation site, Asp63, show a phenotype like the RegA deficient mutant, although the RegA(D63K) mutant protein showed the same DNA binding behavior as the wild type protein. In contrast, the puf and puc mRNAs still reach about 50-70 % of the wild type level after reduction of oxygen tension in strains which synthesize the C-terminal RegA activator domain only or a hybrid protein composed of the RegA activator and the FixJ receiver domain, while both mutant proteins are impaired in DNA binding. Our data suggest that phosphorylation is not required for DNA binding but rather plays a role for efficient initiation of transcription.

Arthroscopic labrum refixation for post-traumatic anterior shoulder instability: suture anchor versus transglenoid fixation technique

SUMMARY

The aim of this retrospective study was to compare recurrence rates following transglenoid labrum refixation or fixation using the suture anchor (FASTak, Arthrex, Naples, FL) technique. Additionally, parameters that apparently influence the rate of redislocation were investigated. There were 163 patients with post-traumatic anterior shoulder instability treated with an arthroscopic labrum refixation; 108 patients (66.3%) were stabilized with the transglenoid suture technique (group I) and 55 patients (33. 7%) with the suture anchor (FASTak) technique (group II). The average follow-up was 4.5 years (range, 2.0 to 7.9 years) in group I and 3.2 years (range, 2.0 to 5.0 years) in group II. The Rowe score increased from a preoperative average of 35.0 points in group I and 35.4 points in group II to a postoperative average of 68.3 points in group I and 84.6 points in group II (P <.01). There was recurrence in 35 patients (32.4%) in group I and 9 patients (16.4%) in group II (P <.05). All incidents of redislocation occurred during the first 21 postoperative months; 58.4% of the patients (n = 63) in group I and 16.4% of the patients in group II (n = 9) had to reduce their sporting activity (P <.001). Independent of the type of surgery, there was a significant correlation of the postoperative rate of redislocation and age (P <.001), number of preoperative dislocations (P <.01), and degree of labrum lesion (P <.001). No correlation with the rate of redislocation was shown for gender, handedness, dislocation-operation interval, degree of Hill-Sachs lesion, or number of transglenoid sutures or anchors. Concerning post-traumatic anterior shoulder instability, the arthroscopic labrum reconstruction with the suture anchor (FASTak) technique was superior to the transglenoid technique but has not yet achieved the level of success obtained by open surgery. With fewer than 5 preoperative redislocations after a first traumatic shoulder dislocation, the arthroscopic treatment is recommended. In cases of more frequent preoperative dislocations, open surgery in combination with a capsular shift should be performed.

Screening by anti-endomysium antibody for celiac disease in diabetic children and adolescents in Austria

BACKGROUND

Unrecognized celiac disease (CD) may be found in a substantial proportion of patients with type I diabetes mellitus.

METHODS

A cohort of 403 Austrian children and adolescents with type I diabetes mellitus (210 males and 193 females; age range, 1-22 years) was screened for celiac disease using the IgA anti-endomysium antibody test (EMA) and the immunoglobulin (Ig)G anti-gliadin (AGA-IgG) and IgA anti-gliadin (AGA-IgA) antibody test.

RESULTS

Twelve patients' sera (2.98%) yielded positive EMA results and two patients' sera (0.49%) with IgA deficiency had high AGA-IgG values. All but one of these patients underwent intestinal biopsy. Six (1.49%) had clear histologic evidence of CD (flat mucosa), whereas three (0.74%) showed minor histologic changes (increase in intraepithelial lymphocytes) and four (0.99%), including the EMA-negative patients with IgA deficiency, had a normal mucosa. When the cases with silent and potential CD were combined, the overall prevalence in the current cohort was 2.98%. There was no difference in the hemoglobin (Hb)A1c level between antibody-positive and -negative patients, and subsequent gluten-free diet did not change this metabolic parameter.

CONCLUSION

The prevalence of clinically unrecognized CD, found by EMA screening, is much higher in Austrian children with diabetes than in a comparable population without diabetes. The prevalence of CD in diabetic children in Austria is distinctly lower, however, than in several other countries.

Correction of the DNA sequence of the regB gene of Rhodobacter capsulatus with implications for the membrane topology of the sensor kinase regB

We corrected the previously published sequence for the regB gene, which encodes a histidine sensor kinase in Rhodobacter capsulatus. The deduced RegB amino acid sequence has an additional putative transmembrane domain at the N terminus. Analysis of RegB-PhoA and RegB-LacZ fusion proteins supports a topology model for RegB with six membrane-spanning domains.

Depression in Parkinson's disease: brainstem midline alteration on transcranial sonography and magnetic resonance imaging

Recent studies using transcranial sonography (TCS) have provided evidence of alterations in the mesencephalic midline structures in patients with unipolar depression and depression in Parkinson's disease (PD), suggesting an involvement of the basal limbic system in primary and secondary mood disorders. This study tested the hypothesis of brainstem midline abnormality in depression and investigated 31 PD patients by magnetic resonance imaging (MRI) and TCS. Signal intensity of the pontine and mesencephalic brainstem midline was rated on T2-weighted images and measured by relaxometry. In addition, two blinded investigators assessed the echogenicity of the brainstem midline by TCS. The severity of motor symptoms and depression were graded independently using standard research scales. Rating of signal intensity and T2 relaxometry of the pontomesencephalic midline structures revealed significant difference between depressed and nondepressed PD patients (P < 0.05). This corresponded to a significant reduction in mesencephalic midline echogenicity of depressed PD patients on TCS images. No correlation was found between raphe signal intensity, T2 relaxation times, or TCS echogenicity and the severity of motor symptoms or depression. This study is the first to show changes in signal intensity and T2 relaxation time of the pontomesencephalic midline structures on MRI in depressed PD patients confirming previous TCS findings. As these midline structures comprise fiber tracts and nuclei of the basal limbic system, the findings may support the hypothesis of an alteration in the basal limbic system in mood disorders.

Determination of the centre of resistance in an upper human canine and idealized tooth model

The purpose of this investigation was to analyse the influence of geometric and material parameters of a human canine on initial tooth mobility, and the stress and strain profiles in the periodontal ligament. While the material parameters of tooth and bony structures are known within an uncertain limit of approximately a factor of 10, values reported for the elasticity parameters of the periodontal ligament differ significantly. In the course of this study, bilinear behaviour was assumed for the mechanical property of the periodontium. The finite element model of an elliptical paraboloid was created as an approximation to the geometry of a human canine to reduce calculation time and to determine influences of the geometry on numerical results. The results were compared with those obtained for a realistic human canine model. The root length of both models was 19.5 mm. By calculating pure rotational and pure tipping movements, the centre of resistance (CR) was determined for both models. They were located on the long axis of the tooth approximately 7.2 mm below the alveolar crest for the idealized model and 8.2 mm for the canine model. Thus, the centre of resistance of a human canine seems to be located around two-fifths of the root length from the alveolar margin. Using these results, uncontrolled tipping (1 N of mesializing force and 5 Nmm of derotating momentum), as well as pure translation (additionally about 10 Nmm of uprighting momentum) were calculated. Comparing the idealized and the realistic models, the uncontrolled tipping was described by the parabolic-shaped model within an accuracy limit of 10 per cent as compared with the canine model, whereas the results for bodily movement differed significantly showing that it is very difficult to achieve a pure translation with the realistic canine model.

[3-D model analysis of the maxilla of infants with lip-jaw-palate clefts]

For the investigation of three-dimensional morphological changes in the maxilla of children with cleft lip and palate, the use of two-dimensional test analysis is inadequate. Since no standardised three-dimensional method has so far been available, a three-dimensional digital, computer-aided procedure was developed to visualize and metrically analyse the growth of the edentulous maxilla of infants with cleft lip and palate. Chronologically consecutive casts of the maxillas (obtained at the ages of one week, and three, six and twelve months) of five children with complete unilateral CLP were measured optically with the instrument Micromeasure 70. Following digitation, the casts were reconstructed in the computer, aligned and superimposed using the Orthosurf program. The distances between the surfaces were then measured; in addition, the surfaces were segmented perpendicular to the alveolar crest at reference points C1, C1', C2, C2' and I. The volumes of the resulting segments were determined and compare with one another. Specially designed software automated the following steps: 1. identification of reference points; 2. alignment of the cloud of points in a system of coordinates, and 3. identification of the alveolar crest. Our initial results show that (1) the new method enables visualization of the extent and direction of morphological changes of the mucosal surface, and (2) reproducible quantification of these changes via the determination of changes in the volume of defined alveolar segments. The three-dimensional analysis presented here permits a comprehensive three-dimensional measurement of the models of the edentulous maxilla of infants with cleft lip and palate.

X-ray diagnosis of impacted upper canines in panoramic radiographs and computed tomographs

Ten orthodontists were asked to diagnose the number of impacted upper canines and the number of resorbed lateral and/or central incisor roots in 30 panoramic radiographs (P1) from 30 patients. In order to objectify these diagnoses, transversal CT images of all 30 patients were examined in addition. Addition of the recordings in the 30 patients revealed that the 10 orthodontists had diagnosed 350 impacted/displaced canines. On comparison of the P1 and CT results, the latter revealed that, in fact, 390 canines were impacted or displaced, not just 350. Addition of the recordings further showed that, based on P1, the investigators had diagnosed 73 resorptions in the 1,200 incisors examined. However, the CT showed 160 resorptions; this corresponds to a sensitivity value of 45.6%. The CT showed 1,040 incisors with no resorptions, whereas the investigators diagnosed only 925 teeth as not resorbed in the P1. The specificity was thus 88.9%. These results show that, due to their low reliability, panoramic radiographs are not an appropriate means of diagnosing resorptions in front teeth in connection with impacted canines.

Simulation of orthodontic tooth movements. A comparison of numerical models

Orthodontic tooth movements are based on the ability of bone to react to mechanical stresses with the apposition and resorption of alveolar bone. Currently, the underlying biophysical, biochemical, and cellular processes are the subject of numerous studies. At present, however, an analytical description of orthodontic tooth movements including all components of the processes involved seems to be impossible. It was the aim of the present study to develop a mechanics-based phenomenological model capable of describing the alveolar bone remodeling. Thus, 2 different models were developed. The first is based on the assumption that deformations of the periodontal ligament (PDL) are the key stimulus to starting orthodontic tooth movement. The second supposes that deformations of the alveolar bone are the basis of orthodontic bone remodeling. Both models were integrated into a finite element package calculating stresses, strains and deformations of tooth and tooth supporting structures and from this simulating the movement of the tooth and its alveolus through the bone. Clinically induced canine retractions in 5 patients as well as force systems were exactly measured and the tooth movements were simulated using both models. The results show that the first model allows reliable simulation of orthodontic tooth movements, whereas the second is to be rejected.

[Arthroscopic labral reconstruction for anterior shoulder instability. Failure analysis in 187 patients]

Comparing open with arthroscopic labral reconstruction for anterior shoulder instability we found a higher recurrence rate after arthroscopic capsulolabral repair. The aim of this study was, to analyse the reasons for recurrent instability after arthroscopic labral repair.

MATERIALS AND METHODS

Between 1989 and 1995 we performed a arthroscopic labral reconstruction on 187 patients with anterior shoulder instability. 118 patients (63%) were treated with a transglenoid suture technique and 69 patient (37%) with a suture anchor technique. The average age at the time of the operation was 26.4 +/- 6.3 years (14-52 years). There were 41 women (21.9%) and 146 men (78.1%).

RESULTS

The minimum follow-up was 18 months. The average follow-up was 3.7 +/- 1.1 years. The average Rowe Score increased from 34.7 points (0-75) preoperatively to 75.3 points (15-100) postoperatively. There were 47 (25.1%) excellent. 76 (40.6%) good, 21 (11.3%) fair, and 43 (23.0%) poor results. 105 patients (56.1%) regained their preoperative level of activity. 50 patients (26.7%) had recurrent subluxations or dislocations postoperatively. All failures occurred within two years (0.5-21 months) after the operation. Failure rates were associated with the patients age (p < 0.001), the level of activity (p < 0.05), the number of the preoperative dislocations (p < 0.01), the degree of the labral lesion (p < 0.001), and the operation method (p < 0.05). No correlation was found for the parameters sex, handiness, time between luxation and operation, size of Hill-Sachs-lesion and numbers of used sutures or anchors.

CONCLUSION

We prefer the arthroscopic suture anchor technique if there are less than 5 preoperative dislocation and a type 1 or 2 labral lesion. If there are more than 5 preoperative dislocations and a degenerative labrum defect we favor the open Bankart repair technique.

Investigation of the imaging properties of an X-ray film scanner

In this note, the imaging properties of a CCD x-ray film scanner were investigated. The relationship between optical density and the logarithm of output pixel value provides information on the linearity of the system. The resolution properties of the scanner can be characterized by the presampling modulation transfer function which was calculated from a set of line spread functions with various alignments relative to the sampling grid. Our results show that the scanner is linear up to 2.0 optical density units, which leads to restrictions in digitizing x-ray films with higher optical density. The measured MTF shows the good spatial resolution of the CCD scanner which is demonstrated on an example.