Idiopathic scoliosis, growth zones, magnetic therapy.

BACKGROUND: The study has been performed to investigate the influence of pulsed magnetic field on the bone growth plates to get new grounds of magneto therapy in AIS treatment. MATERIALS AND METHODS: Were used methods of "strong" and "weak" pulsed magnetic fields influence. RESULTS: Application of pulsed magnetic field causes an authentic inhibition of chondrocytes' active proliferation processes, decreases the index of labeled nuclei, indicating the suppression of DNA synthesis, takes place an increase in the unit weight of the more "mature" differentiated chondrocytes. The final result of these effects is the accelerated synostosis of bones' growth plates. CONCLUSION: Regardless of the reasons that cause growth infringements, the operating organ in the chain is the body's growth plate. Therefore, the appliance of magnetic fields in AIS treatment can be considered as a perspective one concerning growth plates' functional activity local management. To our point of view, the potential of magneto therapy methods in child's orthopedic treatment is significantly higher compared with modern practice.

Low-level laser on femoral growth plate in rats.

PURPOSE: To determine the influence of low-level laser therapy on femoral growth plate in rats. METHODS: Thirty male Wistar rats aged 40 days were divided into two groups, G1 and G2. In G1 the area of the distal growth plate of the right femur was irradiated at one point using GaAlAs laser 830 nm wavelength, output power of 40 mW, at an energy density of 10 J/cm(2). The irradiation was performed daily for a maximum of 21 days. The same procedure was done in G2, but the probe was turned off. Five animals in each group were euthanized on days 7, 14 and 21 and submitted to histomorphometric analysis. RESULTS: In both groups the growth plate was radiographically visible at all moments from both craniocaudal and mediolateral views. On the 21st day percentage of femoral longitudinal length was higher in G2 than G1 compared to basal value while hypertrophic zone chondrocyte numbers were higher in G1 than G2. Calcified cartilage zone was greater in G1 than in G2 at all evaluation moments. Angiogenesis was higher in G1 than in G2 at 14th and 21st days. CONCLUSION: The low-level laser therapy negatively influenced the distal femoral growth plate.

Low-level laser on femoral growth plate in rats / Laser terapêutico de baixa potência na placa de crescimento de ratos

PURPOSE: To determine the influence of low-level laser therapy on femoral growth plate in rats. METHODS: Thirty male Wistar rats aged 40 days were divided into two groups, G1 and G2. In G1 the area of the distal growth plate of the right femur was irradiated at one point using GaAlAs laser 830 nm wavelength, output power of 40 mW, at an energy density of 10 J/cm². The irradiation was performed daily for a maximum of 21 days. The same procedure was done in G2, but the probe was turned off. Five animals in each group were euthanized on days 7, 14 and 21 and submitted to histomorphometric analysis. RESULTS: In both groups the growth plate was radiographically visible at all moments from both craniocaudal and mediolateral views. On the 21st day percentage of femoral longitudinal length was higher in G2 than G1 compared to basal value while hypertrophic zone chondrocyte numbers were higher in G1 than G2. Calcified cartilage zone was greater in G1 than in G2 at all evaluation moments. Angiogenesis was higher in G1 than in G2 at 14th and 21st days. CONCLUSION: The low-level laser therapy negatively influenced the distal femoral growth plate.

OBJETIVO: Determinar a influência do Laser Terapêutico de Baixa Potência sobre a placa de crescimento de ratos. MÉTODOS: Trinta ratos Wistar machos com 40 dias de idade foram divididos em dois grupos, G1 e G2. O grupo G1 foi submetido à irradiação com laser GaAlAs 830 nm, potência de saída de 40 mW, e densidade de energia de 10 J/cm2. A irradiação foi aplicada diariamente por um período máximo de 21 dias. O mesmo procedimento foi realizado no grupo G2, com a probe desativada. Cinco animais em cada grupo foram sacrificados nos dias 7, 14 e 21 e submetidas à análise histomorfométrica. RESULTADOS: Em ambos os grupos, o disco fisário esteve radiograficamente visível em todos os momentos nas incidências craniocaudal e médio-lateral. No 21º dia a porcentagem de comprimento longitudinal do fêmur foi maior em G1 que em G2 em relação ao valor basal, e o número de condrócitos da zona hipertrófica foi maior em G1 que em G2. A zona de cartilagem calcificada estava maior em G1 em relação a G2 em todos os momentos de avaliação. A angiogênese foi maior em G1 que em G2 nos 14º e 21º dias. CONCLUSÃO: A terapia com laser terapêutico de baixa potência influenciou negativamente o disco fisário distal do fêmur de ratos.

[Effect of the impulse magnetic field on the growth bone plates in experimental animals].

The influence of impulse magnetic field (1.5 T) on growth bone plates of the rabbit has been studied. It has been found that this field produces the inhibitory action on the functional activity of growth bone plates.

Protective effect of pentoxifylline on growth plate in neonatal rats following long-term phototherapy.

We demonstrated previously that receiving long-term phototherapy was associated with early impairment of growth plate structure in neonatal rats, and oxidative stress may be the main risk factor for growth plate injury. The purpose of this study was to examine the histomorphometric effects of pentoxifylline treatment on the growth plate. Sixty weanling Sprague-Dawley rats were randomly separated into three equal groups. Group A, the control group, did not receive phototherapy and pentoxifylline. Groups B and C were exposed to phototherapy for 7 d. In addition to phototherapy, group C was also given pentoxifylline during the study period. Compared with zonal lengths on d 7 after initiation of phototherapy, group B had significantly lower values than group A for all zonal lengths (p < 0.001). Zonal lengths of growth plate were increased significantly with pentoxifylline treatment in group C for 7 d compared with group B (p < 0.001). After phototherapy, group B had significantly higher values than groups A and C for plasma malondialdehyde levels (p < 0.001). The pentoxifylline was found here to have some potential to reduce the effects of phototherapy on growth plate in neonatal rats at a relatively low dose.

Electrical stimulation of the growth plate: a potential approach to an epiphysiodesis.

Epiphysiodesis is an operative procedure that induces bony bridges to form across a growth plate of a bone to stop longitudinal growth. This is a very common orthopedic procedure to correct disproportional long-bone growth discrepancies; however, present techniques require an operation and anesthesia. Our study was designed to develop a minimally invasive method of epiphysiodesis by using electrical stimulation with DC current. In a rabbit model, a thin titanium electrode was inserted into a single location of the distal femoral growth plate in three groups: one without current (control), one group with a constant 10 microA (low current, LC), and one group with a 50 microA (high current, HC). The current was delivered for 2 weeks. The nontreated femur served as a control for each animal. Femur lengths were measured and comparisons were made between operated (left) and nonoperated (right) femurs. Digitized histomorphometric and volumetric analyses were performed on each growth plate, and detailed assessments were made of any morphological changes. Using length measurements, the difference in femur length was significantly larger in the HC group and not in the LC or control groups, showing bone growth inhibition at the higher current. In the HC group, bony bridges and disorganized growth plates were observed. This study shows that delivery of an electrical current of 50 microA for as little as 2 weeks can markedly affect bone growth as evidenced by changes in epiphyseal plate volume and architectural organization, and the study supports the use of this minimally invasive approach as a potential method of achieving an epiphysiodesis.

Combinations of radioprotectants spare radiation-induced damage to the physis.

Radiotherapy used in the treatment of bone and soft tissue sarcomas in pediatric patients often results in undesirable growth plate damage. Radioprotectants may hold promise in the selective protection of growth plate tissue in this setting. In an animal model, the hypothesis tested was that pentoxifylline, selenium, or misoprostol, used in combination with amifostine, would significantly reduce longitudinal growth loss during one radiation dose exposure to a greater extent than the protection provided by only amifostine without increased morbidity or mortality or adverse effects on bone mineral density. Amifostine alone and in combination with each of the other radioprotectants resulted in limb discrepancy reduction to levels significantly less than radiated controls. The tibial length discrepancy in the selenium and amifostine group was 12.1 +/- 0.8%, less than the 15.5 +/- 2.6% tibial length discrepancy in the animals treated with amifostine alone, and less than the mean 18.8% tibial length discrepancy in the radiated limbs without radioprotection. There were no adverse effects on bone density in any group, but the selenium and amifostine group showed some increased mortality. Combinations of amifostine with these radioprotectants show efficacy in growth plate radioprotection and therefore warrant additional study in a clinically relevant fractionated model.

Sequential histomorphometric analysis of the growth plate following irradiation with and without radioprotection.

BACKGROUND: The availability of radioprotectant drugs that selectively protect normal cells but not tumor cells has rekindled interest in the effects of irradiation on the growth plate. The purpose of the present study was to quantitatively examine the sequential histomorphometric effects of irradiation and pretreatment with a free radical scavenger radioprotectant, amifostine, on the growth plate over time. METHODS: Sixty four-week-old male Sprague-Dawley rats were randomized into five groups of twelve animals that were to be killed at 0.5, one, two, three, or four weeks after irradiation. One-half of the animals also received amifostine (100 mg/kg) prior to irradiation. In all animals, the right knee was treated with a single 17.5-Gy dose of radiation. End points were assessed with quantitative histomorphometric analysis of the growth plate, BrdU labeling for evidence of proliferation, evaluation of chondroclast cellularity, and determination of growth rates by means of oxytetracycline labeling. RESULTS: The mean lengths of the femur, tibia, and hind limb continued to increase at each time-interval following treatment, but by one week the mean limb length was 4% less on the irradiated side than on the control side, and this difference remained significant for four weeks (p < 0.05). The proximal tibial growth rate decreased during the first week to 18% of the control level. Nevertheless, growth continued even at the earliest time-periods, began to return toward normal at two weeks, and ultimately returned to at least 80% of normal by four weeks after irradiation. The area fraction of matrix in the hypertrophic zone increased initially and returned to control levels at three and four weeks. The administration of the radioprotectant resulted in significant increases in growth, growth rate, growth plate height, hypertrophic zonal height, and chondroclast profiles compared with the values for limbs in which irradiation had not been preceded by treatment with amifostine. CONCLUSIONS: We found an initially profound but transient direct inhibitory effect of irradiation on growth plate chondrocytes. Recovery of growth plate function after irradiation corresponded temporally with the appearance of newly formed islands of proliferating chondrocytes. Accumulation of matrix led to a transient increase in overall growth plate height, which was most pronounced in the hypertrophic zone. This was due, in part, to the sensitivity of chondroclasts to irradiation. The radioprotectant amifostine reduced these effects on growth rate, growth plate height, matrix accumulation, and limb length.

Role of pentoxifylline in preventing radiation damage to epiphyseal growth plate chondrocytes.

Radiation therapy plays an important role as part of multimodality treatment for a number of childhood malignancies. The damaging effects of radiation on bone formation in children have been well documented. Recent work suggests that the postirradiation increase in cytosolic calcium is probably responsible for the deleterious effects of radiation on growth plate chondrocytes because it causes a specific suppression of the mitogen PTHrP. Using an in vitro model of avian growth plate chondrocytes, this study demonstrates that pentoxifylline is effective in increasing basal PTHrP mRNA levels and partially preventing the radiation-induced decrease in PTHrP mRNA. This effect of pentoxifylline is probably due to its ability to lower basal levels of cytosolic calcium and the radiation-induced increase in cytosolic calcium in chondrocytes. Pentoxifylline also prevented the radiation-induced decreases in [3H]thymidine uptake and BCL2 and PTHrP receptor mRNA levels in chondrocytes. The effects of pentoxifylline appear to be specific for the PTHrP signaling pathway because it did not alter basal TGFB mRNA levels or TGFB mRNA expression in irradiated chondrocytes. The results of the current study suggest that by decreasing basal cytosolic calcium levels and curtailing the radiation-induced increase in cytosolic calcium levels in chondrocytes, pentoxifylline is able to sustain PTHrP signaling in chondrocytes and maintains the proliferative signal that is necessary to prevent chondrocytes from undergoing apoptosis.