DTI assessment of the maturing growth plate of the knee in adolescents and young adults.

PURPOSE: To assess the growth plates of the knee in a healthy population of young adults and adolescents using DTI, and to correlate the findings with chronological age and skeletal maturation. METHODS: A prospective, cross-sectional study to assess the tibial and femoral growth plates with DTI in 155 healthy volunteers aged between 14.0 and 21 years old. Echo-planar DTI with 15 directions and b value of 0 and 600 s/mm2 was performed on a 3 T whole-body scanner. RESULTS: A relationship was observed between chronological age and most DTI metrics (fractional anisotropy, mean diffusivity, and radial diffusivity), tract length and volume. (No significant relationship could be seen for axonal diffusivity and tract length.) Subdivision according to skeletal maturation showed the greatest tract lengths and volumes seen in stage 4b and not 4a. The intra-observer agreement was significant (P = 0.01) for all the measured variables, but agreement varied (femur 0.53 - 0.98; tibia 0.58 - 0.98). Spearman's correlation showed a significant correlation for age (P = 0.05; P = 0.01) as well as for the fractional anisotropy value within all variables in both femur and tibia. Tract number and volume had a similar correlation with most variables, especially the DTI metrics, and would seem to be interchangeable. CONCLUSION: The current study indicates that DTI metrics could be a tool to assess the skeletal maturation process of the growth plate and its activity. Tractography seems promising to assess the activity of the growth plate in a younger population but must be used with caution in the more mature growth plate.

Automated localization of the medial clavicular epiphyseal cartilages using an object detection network: a step towards deep learning-based forensic age assessment.

BACKGROUND: Deep learning is a promising technique to improve radiological age assessment. However, expensive manual annotation by experts poses a bottleneck for creating large datasets to appropriately train deep neural networks. We propose an object detection approach to automatically annotate the medial clavicular epiphyseal cartilages in computed tomography (CT) scans. METHODS: The sternoclavicular joints were selected as structure-of-interest (SOI) in chest CT scans and served as an easy-to-identify proxy for the actual medial clavicular epiphyseal cartilages. CT slices containing the SOI were manually annotated with bounding boxes around the SOI. All slices in the training set were used to train the object detection network RetinaNet. Afterwards, the network was applied individually to all slices of the test scans for SOI detection. Bounding box and slice position of the detection with the highest classification score were used as the location estimate for the medial clavicular epiphyseal cartilages inside the CT scan. RESULTS: From 100 CT scans of 82 patients, 29,656 slices were used for training and 30,846 slices from 110 CT scans of 110 different patients for testing the object detection network. The location estimate from the deep learning approach for the SOI was in a correct slice in 97/110 (88%), misplaced by one slice in 5/110 (5%), and missing in 8/110 (7%) test scans. No estimate was misplaced by more than one slice. CONCLUSIONS: We demonstrated a robust automated approach for annotating the medial clavicular epiphyseal cartilages. This enables training and testing of deep neural networks for age assessment.

Assessment of Growth Plate Chondrocytes Proliferative Activity in Embryonic Endochondral Ossification via Ki-67 Immunofluorescence.

Cell proliferation is one of the key events that regulates organism development. In the limb, chondrocytes differentiate into a multi-layered cellular template called the growth plate. Chondrocyte proliferation is essential to provide the necessary cells that allow growth of a bone. Deregulated cell proliferation will lead to truncated bone elements. Immunofluorescence is a biological technique that uses specific antibodies to detect the subcellular localization of a proliferative marker within cellular or tissue context. In this chapter, we illustrate how to perform immunofluorescence to detect the localization of Ki-67 (a marker of actively growing/proliferating chondrocytes) in order to assess the growth fraction of the columnar chondrocytes in the growth plate in paraffin-embedded mouse tissue limb.

Application of 3D MAPs pipeline identifies the morphological sequence chondrocytes undergo and the regulatory role of GDF5 in this process.

The activity of epiphyseal growth plates, which drives long bone elongation, depends on extensive changes in chondrocyte size and shape during differentiation. Here, we develop a pipeline called 3D Morphometric Analysis for Phenotypic significance (3D MAPs), which combines light-sheet microscopy, segmentation algorithms and 3D morphometric analysis to characterize morphogenetic cellular behaviors while maintaining the spatial context of the growth plate. Using 3D MAPs, we create a 3D image database of hundreds of thousands of chondrocytes. Analysis reveals broad repertoire of morphological changes, growth strategies and cell organizations during differentiation. Moreover, identifying a reduction in Smad 1/5/9 activity together with multiple abnormalities in cell growth, shape and organization provides an explanation for the shortening of Gdf5 KO tibias. Overall, our findings provide insight into the morphological sequence that chondrocytes undergo during differentiation and highlight the ability of 3D MAPs to uncover cellular mechanisms that may regulate this process.

Histochemical assessment on the cellular interplay of vascular endothelial cells and septoclasts during endochondral ossification in mice.

This study was aimed to verify the cellular interplay between vascular endothelial cells and surrounding cells in the chondro-osseous junction of murine tibiae. Many CD31-positive endothelial cells accompanied with Dolichos Biflorus Agglutinin lectin-positive septoclasts invaded into the hypertrophic zone of the tibial epiphyseal cartilage. MMP9 immunoreactive cytoplasmic processes of vascular endothelial cells extended into the transverse partitions of cartilage columns. In contrast, septoclasts included several large lysosomes which indicate the incorporation of extracellular matrices despite no immunopositivity for F4/80-a hallmark of macrophage/monocyte lineage. In addition, septoclasts were observed in c-fos-/- mice but not in Rankl-/- mice. Unlike c-fos-/- mice, Rankl-/- mice showed markedly expanded hypertrophic zone and the irregular shape of the chondro-osseous junction. Immunoreactivity of platelet-derived growth factor-bb, which involved in angiogenic roles in the bone, was detected in not only osteoclasts but also septoclasts at the chondro-osseous junction. Therefore, septoclasts appear to assist the synchronous vascular invasion of endothelial cells at the chondro-osseous junction. Vascular endothelial cells adjacent to the chondro-osseous junction possess endomucin but not EphB4, whereas those slightly distant from the chondro-osseous junction were intensely positive for both endomucin and EphB4, while being accompanied with ephrinB2-positive osteoblasts. Taken together, it is likely that vascular endothelial cells adjacent to the chondro-osseous junction would interplay with septoclasts for synchronous invasion into the epiphyseal cartilage, while those slightly distant from the chondro-osseous junction would cooperate with osteoblastic activities presumably by mediating EphB4/ephrinB2. MINI-ABSTRACT: Our original article demonstrated that vascular endothelial cells adjacent to the chondro-osseous junction would interplay with septoclasts for synchronous invasion into the epiphyseal cartilage, while those slightly distant from the chondro-osseous junction would cooperate with osteoblastic activities presumably by mediating EphB4/ephrinB2. (A figure that best represents your paper is Fig. 5c).

An Alternative to the Traditional Radiocapitellar Line for Pediatric Forearm Radiograph Assessment in Monteggia Fracture.

OBJECTIVE: To find a new reference for assessment of pediatric forearm radiographs besides the traditional RCL. METHODS: RCLs were drawn on the anteroposterior (AP) and lateral radiographs of 170 normal pediatric forearms. Three lines were drawn on each radiograph: the first was drawn along the longitudinal center of the radial neck (N-line); the second, along the radial shaft (S-line); and the third, through the midpoints of the proximal and distal radial physes (P-line). RESULTS: The P-line was least likely to miss the capitellum on both AP views and lateral views, and the P-line most frequently passed through the central third of the capitellum on both AP views and lateral views. CONCLUSIONS: Our proposed radiocapitellar P-line was found to be much more reliable in younger children than traditional RCLs.

Safety assessment of a novel C-type natriuretic peptide derivative and the mechanism of bone- and cartilage-specific toxicity.

ASB20123, a C-type natriuretic peptide/ghrelin chimeric peptide, was designed as a novel peptide and demonstrated full agonistic activity for natriuretic-peptide receptor B and a significantly longer half-life in plasma compared with the native peptide. We researched the toxicological profile of ASB20123, the correlation between the morphological change of the epiphyseal plate and bone and cartilage toxicity, and biomarkers to detect the toxicity. ASB20123 was systemically administered to male and female rats at daily dose levels of 0.5, 1.5, and 5.0 mg/kg/day for 4 weeks. In this study, toxicity was observed as changes related to bone and cartilage tissues, and no other toxicological changes were observed in all animals. Next, ASB20123 was administered to 12-month-old rats with a little epiphyseal plate. The toxic changes related to bone and cartilage tissues were not observed in any animal with a closed epiphyseal plate, indicating that the toxic changes were triggered by the growth-accelerating effect on the bone and cartilage. Furthermore, we searched for the biomarker related to the bone and cartilage toxicity using rats treated with ASB20123 at doses of 0.005, 0.05, 0.5, and 5.0 mg/kg/day for 4 weeks. A close correlation between necrosis/fibrosis in the epiphysis and metaphysis and thickness of the epiphyseal plate in the femur was confirmed in this study. A decrease in the bone mineral density (BMD) of the femur also was associated with the appearance of bone toxicity. These results indicated that the toxicity of ASB20123 was limited to bone- and cartilage-specific changes, and these changes were triggered by an excessive growth accelerating effect. Furthermore, our data suggested that the thickness of the epiphyseal plate and BMD could be reliable biomarkers to predict bone toxicity.

MRI assessment of growth disturbances after ACL reconstruction in children with open growth plates-Prospective multicenter study of 100 patients.

INTRODUCTION: We were interested in the consequences of anterior cruciate ligament (ACL) reconstruction on the growth plates and the impact on growth in children with open growth plates. The primary objective was related to growth disturbances with the null hypothesis being that ACL reconstruction in open growth plates does not cause any. The secondary objective related to the presence of physis lesions on MRI, with the null hypothesis being that ACL reconstruction in open growth plates does not induce any. MATERIAL AND METHODS: In the context of a 2017 SFA symposium on ACL reconstruction with open growth plates, we conducted a prospective multicenter study with 2 years' follow-up. The study enrolled 100 patients; 71 were available for analysis. Four reconstruction techniques were used: semitendinosus-gracilis (STG), short graft (SG), quadriceps tendon (QT) and fascia lata (FL). MRI was used to look for growth disturbances as evidenced by deviation of the Harris lines or modification of the physis and diaphysis angles. Physis lesions were determined on MRI based on the presence of physeal bone bridges (PBB). RESULTS: No growth disturbances were found. However, PBBs were found in 14 patients (20%). At the femur, the relative risk (RR) was higher when a STG graft was used (RR=2.1) and the tunnel diameter was≥9mm (RR=1.7). Epiphyseal fixation had a higher risk than transphyseal fixation (RR=1.6 vs. 1.2). At the tibia, the RR was higher when a QT graft was used (RR=3.6), when screw fixation was performed (RR=3.7) or when the graft did not fill the tunnel sufficiently (RR=1.5). DISCUSSION: The absence of growth disturbances after 2 years' follow-up validates the possibility of ACL reconstruction with open growth plates, including with transphyseal techniques. The presence of small growth plate lesions such as bone bridges means that precautions should be taken with respect to tunnel trajectory, tunnel diameter, graft and tunnel diameter matching and graft fixation. LEVEL OF EVIDENCE: III, prospective cohort study.

Evaluating Intensity Modulated Proton Therapy Relative to Passive Scattering Proton Therapy for Increased Vertebral Column Sparing in Craniospinal Irradiation in Growing Pediatric Patients.

PURPOSE: At present, proton craniospinal irradiation (CSI) for growing children is delivered to the whole vertebral body (WVB) to avoid asymmetric growth. We aimed to demonstrate the feasibility and potential clinical benefit of delivering vertebral body sparing (VBS) versus WVB CSI with passively scattered (PS) and intensity modulated proton therapy (IMPT) in growing children treated for medulloblastoma. METHODS AND MATERIALS: Five plans were generated for medulloblastoma patients, who had been previously treated with CSI PS proton radiation therapy: (1) single posteroanterior (PA) PS field covering the WVB (PS-PA-WVB); (2) single PA PS field that included only the thecal sac in the target volume (PS-PA-VBS); (3) single PA IMPT field covering the WVB (IMPT-PA-WVB); (4) single PA IMPT field, target volume including thecal sac only (IMPT-PA-VBS); and (5) 2 posterior-oblique (-35°, +35°) IMPT fields, with the target volume including the thecal sac only (IMPT2F-VBS). For all cases, 23.4 Gy (relative biologic effectiveness [RBE]) was prescribed to 95% of the spinal canal. The dose, linear energy transfer, and variable-RBE-weighted dose distributions were calculated for all plans using the tool for particle simulation, version 2, Monte Carlo system. RESULTS: IMPT VBS techniques efficiently spared the anterior vertebral bodies (AVBs), even when accounting for potential higher variable RBE predicted by linear energy transfer distributions. Assuming an RBE of 1.1, the V10 Gy(RBE) decreased from 100% for the WVB techniques to 59.5% to 76.8% for the cervical, 29.9% to 34.6% for the thoracic, and 20.6% to 25.1% for the lumbar AVBs, and the V20 Gy(RBE) decreased from 99.0% to 17.8% to 20.0% for the cervical, 7.2% to 7.6% for the thoracic, and 4.0% to 4.6% for the lumbar AVBs when IMPT VBS techniques were applied. The corresponding percentages for the PS VBS technique were higher. CONCLUSIONS: Advanced proton techniques can sufficiently reduce the dose to the vertebral body and allow for vertebral column growth for children with central nervous system tumors requiring CSI. This was true even when considering variable RBE values. A clinical trial is planned for VBS to the thoracic and lumbosacral spine in growing children.

Validation of the ultrasonographic assessment of the femoral trochlea epiphyseal cartilage in foals at osteochondrosis predilected sites with magnetic resonance imaging and histology.

BACKGROUND: Noninvasive imaging tools are needed to screen foal femoropatellar joints to detect subclinical osteochondrosis lesions due to focal failure of endochondral ossification to enhance early management to optimise intrinsic healing events. Recently investigations employing 3T susceptibility-weighted magnetic resonance imaging (3T SWI MRI) and CT have demonstrated their capacity for early osteochondrosis diagnosis, but these technologies are not practical for field screening. We postulate that ultrasonography is a valuable field tool for the detection of subclinical osteochondrosis lesions. OBJECTIVES: The goals were to 1) describe the ultrasonographic features of the femoral trochlea of healthy and osteochondrosis-predisposed neonatal foals, 2) validate the capacity of ultrasound to assess cartilage canal vascular archictecture and the ossification front and 3) evaluate field feasibility in a pilot study. STUDY DESIGN: Experimental study. METHODS: Ultrasonographic evaluation of osteochondrosis predisposed (n = 10) and control (n = 6) femoral trochleas was performed ex vivo and compared with site-matched histological sections and 3T SWI MRI. The articular and epiphyseal cartilage thickness, ossification front indentation and cartilage canal vascular archictecture were assessed at each ROI. Femoral trochleae of foals (n = 3) aged ≈ 1, 3 and 6 months were also evaluated with ultrasonography in field. RESULTS: Ultrasonographic measurements strongly correlated with the histological measurements. There was no difference in the cartilage thickness or ossification front indentation between control and osteochondrosis-predisposed specimens. The cartilage canal vascular archictecture on ultrasonograms corresponded with the vessel pattern observed on site matched histology and 3T SWI MRI. MAIN LIMITATIONS: The number of specimens for study was limited and no early osteochondrosis lesions were present within the predilected group, but a field study is now underway. CONCLUSION: Ultrasonographic examination of the femoral trochlea permitted accurate evaluation of cartilage thickness, cartilage canal vascular archictecture and ossification front indentation in young foals and is a promising, practical tool for screening subclinical osteochondrosis and monitoring and managing lesions at important clinical sites.

Assessment of pharmacokinetics for microvessel proliferation by DCE-MRI for early detection of physeal bone bridge formation in an animal model.

OBJECTIVES: Bone bridge formation occurs after physeal lesions and can lead to growth arrest if not reversed. Previous investigations on the underlying mechanisms of this formation used histological methods. Therefore, this study aimed to apply a minimally invasive method using dynamic contrast-enhanced MRI (DCE-MRI). MATERIALS AND METHODS: Changes in functional parameters related to the microvessel system were assessed in a longitudinal study of a cohort of an animal model applying a reference region model. The development of morphology of the injured physis was investigated with 3D high-resolution MRI. To acquire complementary information for MRI-related findings qRT-PCR and immunohistochemical data were acquired for a second cohort of the animal model. RESULTS: The evaluation of the pharmacokinetic parameters showed a first rise of the transfer coefficient 7 days post-lesion and a maximum 42 days after operation. The analysis of the complementary data showed a connection of the first rise to microvessel proliferation while the maximum value was linked to bone remodeling. CONCLUSION: The pharmacokinetic analysis of DCE-MRI provides information on a proliferation of microvessels during the healing process as a sign for bone bridge formation. Thereby, DCE-MRI could identify details, which up to now required analyses of highly invasive methods.

Assessment of skeletal age on the basis of DXA-derived hand scans in elite youth soccer.

Physical performance is highly dependent on maturity. Therefore, consideration of maturity is recommended in the talent identification process. To date, skeletal age (SA) is assessed using X-ray scans. However, X-rays are associated with a 10-fold higher radiation compared to dual-energy X-ray absorptiometry (DXA). The aim of the study was to validate SA assessments in male soccer players with the DXA technique. Paired X-ray and DXA scans of the left hand of 63 Swiss U-15 national soccer players were performed. SA assessments were performed twice by two blinded raters using Tanner and Whitehouse' reference technique. Intrarater and interrater reliability as well as agreement between both techniques were tested. Intrarater and interrater reliabilities were excellent. Bland-Altman plots showed that SA assessments between X-ray and DXA differed by -0.2 years and 95% limits of agreement were ±0.6 years. Therefore, DXA offered a replicable method for assessing SA and maturity in youth soccer players.

Assessment of femoral physeal activity after transitory hemiepiphysiodesis using screws and nonabsorbable filament.

BACKGROUND: Different techniques for gradual correction of angular deformities of lower limbs exist. Long-term behavior of the growth plate after hemiepiphysiodesis is not yet well understood. We assessed the restoration of normal physeal activity in New Zealand rabbits, after transitory hemiepiphysiodesis, using screws and nonabsorbable filament. METHODS: We performed a lateral distal femoral epiphysiodesis using nonabsorbable filament and screws, in the right knees of 14 New Zealand male rabbits, aged 11 weeks. Two groups were created: in group 1, the suture was cut after 1 month, and in group 2 it was left uncut. Simple plain radiographs were taken at the beginning and at 4, 8, and 12 weeks of follow-up to evaluate lower limb deformity rate and femoral length. The left knee of each rabbit served as controls. Angular deformity and femoral length were compared between the groups. RESULTS: Eleven rabbits completed the protocol. The control group had no modification in lower limb mechanical axis. On the fourth week, all operated limbs had a significant valgus tibiofemoral angle variation (mean 24 degrees, P<0.05). When the filament was cut, there was complete restoration of the mechanical axis. When the filament was kept, tibiofemoral angle increased its valgus deformity until the eighth week (mean 32 degrees) without changes thereafter. The final femoral length was shorter in group 2 compared with the other 2 groups (P<0.05), whereas group 1 was slightly longer than the control group (P>0.05). CONCLUSIONS: Lateral distal femoral hemiepiphysiodesis with nonabsorbable filament resulted in a valgus deformity on the femur. Once the filament is cut, the femur can restore its normal alignment, while maintaining longitudinal growth. Keeping the physeal tether increases the valgus achieved during the first 8 weeks, and remained stable throughout the study, shortening the bone. CLINICAL RELEVANCE: This is an effective alternative for the correction of angular limb deformities that maintains physeal function and may be useful for orthopedic surgeons. It could also represent an adequate model for the study of rebound effect.

Tooth mineralization stages as a diagnostic tool for assessment of skeletal maturity.

INTRODUCTION: The objective of this study was to determine whether dental calcification can be used as a first-level diagnostic tool for assessment of skeletal maturity. METHODS: A total of 150 healthy subjects (79 boys, 71 girls; mean age, 12.19 ± 2.03 years; range, 8-16 years) were enrolled in the study. Dental maturity was assessed through the calcification stages from panoramic radiographs of the mandibular canine, the first and second premolars, and the second molar. Determination of skeletal maturity was according to the modified middle phalanx of third finger (MP3) stages method on digital radiographs. RESULTS: Diagnostic ability was evaluated according to the dental maturation stages for each tooth for identification of the MP3 stages and the growth phases (prepubertal, pubertal, postpubertal) using positive likelihood ratios. Dental maturation stage E of the first premolars and the combination of canine stage F, first premolar stage E, second premolar stage E, and second molar stage D (FEED) gave the highest values for identification of the prepubertal growth phase, and stage H of the second molar had the highest value for identification of the postpubertal growth phase. CONCLUSIONS: Dental maturation assessment is only useful for diagnosis of the prepubertal and postpubertal growth phases.

Multipurpose contrast enhancement on epiphyseal plates and ossification centers for bone age assessment.

BACKGROUND: The high variations of background luminance, low contrast and excessively enhanced contrast of hand bone radiograph often impede the bone age assessment rating system in evaluating the degree of epiphyseal plates and ossification centers development. The Global Histogram equalization (GHE) has been the most frequently adopted image contrast enhancement technique but the performance is not satisfying. A brightness and detail preserving histogram equalization method with good contrast enhancement effect has been a goal of much recent research in histogram equalization. Nevertheless, producing a well-balanced histogram equalized radiograph in terms of its brightness preservation, detail preservation and contrast enhancement is deemed to be a daunting task. METHOD: In this paper, we propose a novel framework of histogram equalization with the aim of taking several desirable properties into account, namely the Multipurpose Beta Optimized Bi-Histogram Equalization (MBOBHE). This method performs the histogram optimization separately in both sub-histograms after the segmentation of histogram using an optimized separating point determined based on the regularization function constituted by three components. The result is then assessed by the qualitative and quantitative analysis to evaluate the essential aspects of histogram equalized image using a total of 160 hand radiographs that are implemented in testing and analyses which are acquired from hand bone online database. RESULT: From the qualitative analysis, we found that basic bi-histogram equalizations are not capable of displaying the small features in image due to incorrect selection of separating point by focusing on only certain metric without considering the contrast enhancement and detail preservation. From the quantitative analysis, we found that MBOBHE correlates well with human visual perception, and this improvement shortens the evaluation time taken by inspector in assessing the bone age. CONCLUSIONS: The proposed MBOBHE outperforms other existing methods regarding comprehensive performance of histogram equalization. All the features which are pertinent to bone age assessment are more protruding relative to other methods; this has shorten the required evaluation time in manual bone age assessment using TW method. While the accuracy remains unaffected or slightly better than using unprocessed original image. The holistic properties in terms of brightness preservation, detail preservation and contrast enhancement are simultaneous taken into consideration and thus the visual effect is contributive to manual inspection.

Growth disturbance after lengthening of the lower limb and quantitative assessment of physeal closure in skeletally immature patients with achondroplasia.

This study evaluated the effect of limb lengthening on longitudinal growth in patients with achondroplasia. Growth of the lower extremity was assessed retrospectively by serial radiographs in 35 skeletally immature patients with achondroplasia who underwent bilateral limb lengthening (Group 1), and in 12 skeletally immature patients with achondroplasia who did not (Group 2). In Group 1, 23 patients underwent only tibial lengthening (Group 1a) and 12 patients underwent tibial and femoral lengthening sequentially (Group 1b). The mean lengthening in the tibia was 9.2 cm (59.5%) in Group 1a, and 9.0 cm (58.2%) in the tibia and 10.2 cm (54.3%) in the femur in Group 1b. The mean follow-up was 9.3 years (8.6 to 10.3). The final mean total length of lower extremity in Group 1a was 526.6 mm (501.3 to 552.9) at the time of skeletal maturity and 610.1 mm (577.6 to 638.6) in Group 1b, compared with 457.0 mm (411.7 to 502.3) in Group 2. However, the mean actual length, representing the length solely grown from the physis without the length of distraction, showed that there was a significant disturbance of growth after limb lengthening. In Group 1a, a mean decrease of 22.4 mm (21.3 to 23.1) (4.9%) was observed in the actual limb length when compared with Group 2, and a greater mean decrease of 38.9 mm (37.2 to 40.8) (8.5%) was observed in Group 1b when compared with Group 2 at skeletal maturity. In Group 1, the mean actual limb length was 16.5 mm (15.8 to 17.2) (3.6%) shorter in Group 1b when compared with Group 1a at the time of skeletal maturity. Premature physeal closure was seen mostly in the proximal tibia and the distal femur with relative preservation of proximal femur and distal tibia. We suggest that significant disturbance of growth can occur after extensive limb lengthening in patients with achondroplasia, and therefore, this should be included in pre-operative counselling of these patients and their parents.

Age assessment by magnetic resonance imaging of the knee: a preliminary study.

The authors developed an original magnetic resonance imaging (MRI) staging system for epiphyseal fusion of growth plate maturation of the knee and evaluated its reliability and validity for age assessment of living individuals. A total of 290 MRI scans of the knee were reviewed retrospectively in patients aged from 10 to 30 years old (138 males, 152 females). Five original MRI stages were defined to assess the degree of maturation of the distal femoral and proximal tibial epiphyses. Intra-observer variability was excellent and inter-observer variability was good, demonstrating the reliability and the validity of this original MRI staging system. In both sexes, the changes of growth plates (proximal tibial or distal femoral) were associated with age (p<0.001). Our results agreed with classic data on skeletal maturation of the knee, with globally earlier maturation in females than in males, and also earlier maturation of the proximal tibial epiphysis than of the distal femoral epiphysis. MRI of the knee is an efficient non-invasive method of age assessment, without the disadvantage of X-ray exposure. Further studies with larger groups are needed to support our results.

Assessment of epiphyseal plate allograft viability and function after ex vivo storage in University of Wisconsin Solution.

BACKGROUND: Compromised epiphyseal plate function can result in limb deformities. Microvascular transplantation of an epiphyseal plate allograft is a potentially effective approach to reestablish longitudinal limb growth. For this procedure to become clinically useful, the technique for temporary ex vivo storage of allografts must be reliable. The goal of this study was to determine a time frame for which proximal tibial epiphyseal plate allografts could be stored in University of Wisconsin Preservation Solution (UWPS) and remain functional in vivo after microvascular transplantation. METHODS: Proximal tibial epiphyseal plate allografts from skeletally immature female New Zealand White rabbits (10 to 12 wk of age) were used. Allografts (isolated on the popliteal arteriovenous pedicle) were stored ex vivo in cold UWPS for periods of up to 21 days. Chondrocyte viability, phenotype, and extracellular matrix composition of growth plate cartilage was assessed. Microvascular transplantations of nonstored or prestored (3 d) allografts were performed and analysis of bromodeoxyuridine and calcein incorporation was done to determine chondrocyte proliferation and new bone growth, respectively. RESULTS: In vitro analysis showed that, compared with control tissue, epiphyseal plate chondrocyte viability (P>0.05), organization, and collagen extracellular matrix was preserved up to 4 days in cold UWPS. Microvascular transplantation of nonstored epiphyseal plate allografts was successful. Despite care being taken to ensure vascular patency during the microvascular procedure, transplantation of prestored allografts failed due to absent flow in the larger vessels and in the allograft based upon the visualization of organized thrombus within the vascular pedicle, and absent flow within the composite graft itself. However, growth plate viability and function was detected in a peripheral region of a single allograft where partial blood flow had been maintained during the transplantation period. CONCLUSIONS: Ex vivo storage in cold UWPS for 3 days maintains growth plate chondrocyte viability and function in vivo. However, future studies must be directed toward investigating the direct effect of ex vivo storage on the integrity and function of the vascular pedicles.

Evaluación de la resistencia de un prototipo de placa de compresión dinámica (PCD)fabricada de polimetilmetacrilato (PMMA) probada en fémur canino osteotomizado / Assessment of the resistance of a polymethylmethacrylate (PMMA) Dynamic Compression plate (DCP) prototype tested on osteotomized canine femurs

Las fracturas de huesos largos encontradas más frecuentemente en animales pequeños son las del fémur. Por su posición anatómica, son difíciles de inmobilizar, entonces, la utilización de fijaciones internas es de gran utilidad. Las placas de compresión dinámica (PCD) proveen gran estabilidad, son durables y al producir compresión interfragmentaria, minimizan el movimiento fragmentario y promueven la cicatrización primaria del hueso. Sus ventajas están asociadas a la reconstrucción anatómica, movilidad temprana y capacidad de carga del miembro. El polimetilmetacrilato (PMMA) es una resina acrílica utilizada en prótesis dentales. Pero, estudios muestran otros usos, tratamientos de tumores óseos, prótesis en deformaciones craneales, vertebroplastias percutáneas y prótesis testiculares en animales, entre otros. El objetivo de este estudio fue fabricar PCD-PMMA y comprobar su resistencia a las distintas fuerzas que están presentes en una fractura. Se fabricaron 48 PCD de 3,5 milímetros de cuatro orificios a partir de un molde de alginato. Se obtuvieron seis fémures de cadáveres caninos de 10 a 20 kg de peso, a los cuales se les realizó una osteotomía que simulaba una fractura oblicua. Posteriormente, se posicionaron las placas en los huesos osteotomizados para someterlas a las distintas fuerzas que participan en una fractura. Las PCD-PMMA resistieron 2,83 newton/metro a la fuerza de torsión y 0,21 kilonewton a las fuerzas de compresión y flexión. La resistencia de la PCD-PMMA obtenida fue en promedio de 20 kg, a cada una de las fuerzas. Se pudo concluir que es posible fabricar una PCD-PMMA de 3,5 mm de cuatro orificios, cuya resistencia es de 20 kg de peso a las tres fuerzas aplicadas. Entonces, pueden ser utilizadas para la estabilización de fracturas de huesos largos que sean sometidos a una presión inferior a 20 kg de fuerza.

Femur fractures are the most frequent long bone fractures in small animals. Due to the femur’s anatomical position, it is difficult to immobilize, and therefore internal fixations are veryuseful. Dynamic compression plates (DCP) provide high stability, are durable, minimize fragment movement and promote primary healing of the bone. Advantages of this treatmentinclude anatomical reconstruction, early mobility and carrying capacity of the affected limb. Polymethylmethacrylate (PMMA) is an acrylic resin that has proved very useful in bone tumor treatment, cranial deformation prosthesis, percutaneous vertebroplasty and testicular prosthesis in animals. The purpose of this study was to manufacture DCP-PMMA and testits resistance to the different forces present in a fracture. Forty-eight (48) 3.5MM x 4-hole DCP were made from an alginate mold. Six (6) femurs were obtained from canine cadavers weighing from 10 to 20 kg, which underwent osteotomy simulating an oblique fracture. The plates were subsequently positioned in the osteotomized bones to submit them to the various forces involved in a fracture. The DCP-PMMA resisted a torque force of 2.83 newton/metres and a compression and flexion force of 0.21 kilonewton. The obtained resistance of the DCP-PMMA was an average of 20 kg per force. The results of this study show that it is possible to make a DCP-PMMA 3.5 mm x 4-hole, the resistance of which is of 20 kg against the three applied forces, and that it can be used to stabilize long bone fractures subjected to a pressure of less than 20 kg.