Rodrigo Okubo

The osteogenic effects of swimming, jumping, and vibration on the protection of bone quality from disuse bone loss

We assessed and compared the effects of swimming, jumping, and vibration therapies on the prevention of bone loss because of unloading. Eighty Wistar rats were randomly divided into eight groups: S, permanent hind limb‐suspended rats; CON, control rats; S + Swim, unloading interrupted by swimming exercise; S + CSwim, suspension interrupted by regular weight‐bearing with the same duration as in the S + Swim protocol; S + Jump, unloading interrupted by jumping exercise; S + CJump, suspension interrupted for regular weight‐bearing as in the S + Jump group; S + Vibr, unloading interrupted by vibration; and S + CVibr, suspension with interruptions for regular weight‐bearing with the same protocol as that used for the S + Vibr rats. At the end of the experiment, the bone mineral density, bone strength, histomorphometric parameters, and serum levels of the bone markers were analyzed. The hind limb‐suspended rats exhibited bone quality loss. In contrast, the trained rats showed a significant increase in bone mass, bone strength, bone formation, and serum levels of bone markers compared with the respective controls. Although we did not find a significant difference among the three physical exercises, the osteogenic effect of vibration was slightly lower than that of swimming and jumping. Thus, all physical exercises were efficient in preventing bone loss because of unloading and preserving bone quality.

Effect of local anaesthetic infiltration with bupivacaine and ropivacaine on wound healing: a placebo‐controlled study

Infiltration of surgical wounds with long‐acting local anaesthetics (LA) is used to reduce postoperative incisional pain. We hypothesised that infiltration with LA interferes with wound healing in rats. Seventy‐two rats were allocated into nine groups. After intraperitoneal anaesthesia, the interscapular dorsal region was infiltrated with equivolumes of saline, 0·5% bupivacaine or ropivacaine, in a randomised double‐blind fashion. A standardised incision was performed in the infiltrated area and sutured closed. The rats were euthanised on the 3rd or 14th day after the operation and tissue from the incision site was subjected to histochemical analyses and mechanical testing (MT). Compared with the control group, bupivacaine displayed a significant increase in the macrophage number on day 3 (+63% versus +27% for ropivacaine). The transforming growth factor β‐1 expression had a significant increase in the LA (versus saline) groups, +63% in ropivacaine group and +115% in bupivacaine group on day 3 (P < 0·05). The collagen fibres as measured by dyed area were significantly higher in the bupivacaine group on day 3 (+56%, P < 0·01 versus +15% for ropivacaine). CD34 was reduced in bupivacaine group (−51%, P < 0·05 versus +3% for ropivacaine). On day 14, no statistical differences were observed in either LA group (versus saline) with respect to histopathologic or inflammatory mediators. MT on day 14 showed no differences between the LA and saline groups. The LA‐induced increases in histological markers did not extend beyond the third day, suggesting that wound infiltration with long‐acting LA does not impair the wound healing process in rats.

Biomechanical performance of flexible intramedullary nails with end caps tested in distal segmental defects of pediatric femur models.

Background: Unstable distal femoral fractures in children are challenging lesions with restricted surgical options for adequate stabilization. Elastic nails have become popular for treating femoral shaft fractures, yet they are still challenging for using in distal fractures. The aim of this study was to test whether end caps (CAP) inserted into the nail extremity improved the mechanical stabilization of a segmental defect at the distal femoral metaphyseal-diaphyseal junction created in an artificial pediatric bone model. Methods: Two 3.5-mm titanium elastic nails (TEN) were introduced intramedullary into pediatric femur models, and a 7.0-mm-thick segmental defect was created at the distal diaphyseal-metaphyseal junction. Nondestructive 4-point bending, axial-bending, and torsion tests were conducted. After this, the end caps were inserted into the external tips of the nails and then screwed into the bone cortex. The mechanical tests were repeated. Stiffness, displacement, and torque were analyzed using the Wilcoxon nonparametric test for paired samples. Results: In the combined axial-bending tests, the TEN+CAP combination was 8.75% stiffer than nails alone (P<0.01); in torsion tests, the TEN+CAP was 14% stiffer than nails alone (P<0.01). In contrast, the 4-point bending test did not show differences between the methods (P=0.91, stiffness; P=0.51, displacement). Thus, the end caps contributed to an increase in the construct stability for torsion and axial-bending forces but not for 4-point bending forces. Conclusions: These findings indicate that end caps fitted to elastic nails may contribute to the stabilization of fractures that our model mimics (small distal fragment, bone comminution, and distal bone fragment loss). Clinical Relevance: Type II [therapeutic study: lesser-quality randomized controlled trial (eg, <80% follow-up, no blinding, or improper randomization)].

Standing Frame and Electrical Stimulation Therapies Partially Preserve Bone Strength in a Rodent Model of Acute Spinal Cord Injury

ObjectiveThe aim of this study was to compare the effect of standing frame and electrical stimulation on bone quality in a rodent transection model of spinal cord injury (SCI). DesignSeven-week-old male Wistar rats were divided into four groups: sham, n = 10; SCI, n = 7; SCI + standing frame, n = 7; and SCI + electrical stimulation, n = 7. Complete SCI was generated by surgical transection of the cord at the T10 level. Therapies were initiated 3 days after the surgery, 3 days/wk, 20 mins/day, for 30 days. Animals were killed on day 33 postinjury. ResultsNo treatment preserved bone mineral density at any skeletal site tested (P = 0.08–0.99). Standing frame therapy preserved maximal load at the lumbar vertebral body (14% vs. 37% reduction, P = 0.01) and prevented SCI-induced loss of stiffness at both the femur (8% vs. 37% reduction, P = 0.03) and the tibia (35% vs. 56% reduction, P < 0.0001). Electrical stimulation therapy reduced SCI-induced loss of stiffness at the tibia only (40% vs. 56% reduction, P = 0.003). ConclusionsStanding frame and electrical stimulation may have potential as future therapeutic modalities to treat or prevent bone loss after SCI.

Análise biomecânica e histológica de músculos gastrocnêmios de ratas submetidas à lesão muscular e tratados com laserterapia de baixa intensidade

OBJETIVE: To evaluate, by means of biomechanical and histological analysis, the effect of low-level laser therapy on the gastrocnemius of rats subjected to muscle lesion by impact. METHODS: 45 female Wistar rats, weighing 250g, were divided into 3 groups (n=15/group): C (control), ML (animals submitted to muscle lesion) and ML-L (animals submitted to muscle lesion and laser therapy). The animals from groups ML and ML-L were subjected to an experimental muscle lesion by means of an impact of a 250g load, released from a height of 30 cm, directly on the gastrocnemius. The animals from group ML-L were submitted to a treatment with a 960 Nm laser, 2 J/cm2, for 3 days, twice a day. RESULTS: The mechanical tests were performed on the Universal Testing Machine. The average values of maximum force were: 35.70 (± 2.69) N in group C, 31.77 (± 2.59) N in group ML and 34.36 (± 3.63) N in group ML-L, with a statistically significant difference between groups C and ML (p 0.05). Histological analysis showed a presence of blood vessels in group ML-L and a hematoma in the healing stage. CONCLUSION: Treatment with low-level laser had a positive effect in the healing process of muscle injury.

Biomecânica de quatro técnicas de fixação da fratura em quatro partes da cabeça umeral

OBJECTIVE: To carry out a biomechanical study of four techniques for fixation of four-part humeral head fractures. METHODS: The fracture was reproduced in 40 plastic humeri, divided into groups of ten according to the fixation technique, each one employing different fixation resources, in different configurations. The humeral models were mounted on an aluminum scapula, with leather straps simulating the rotator cuff tendons, and submitted to bending and torsion tests in a universal testing machine, using relative stiffness as an evaluation parameter. Assemblies with intact humeri were analyzed for comparison. RESULTS: The biomechanical behavior of the fixation techniques varied within a wide range, where the assemblies including the DCP plate and the 4.5mm diameter screws were significantly more rigid than the assemblies with the Kirschner wires and the 3.5mm diameter screws. CONCLUSION: The four fixation techniques were able to bear loads compatible with the physiological demand, but those with higher relative stiffness should be preferred for clinical application. Laboratory investigation .

Development and mechanical testing of a short intramedullary nail for fixation of femoral rotational osteotomy in cerebral palsy patients

BackgroundRotational osteotomy is frequently indicated to correct excessive femoral anteversion in cerebral palsy patients. Angled blade plate is the standard fixation device used when performed in the proximal femur, but extensile exposure is required for plate accommodation. The authors developed a short locked intramedullary nail to be applied percutaneously in the fixation of femoral rotational osteotomies in children with cerebral palsy and evaluated its mechanical properties.MethodsThe study was divided into three stages. In the first part, a prototype was designed and made based on radiographic measurements of the femoral medullary canal of ten-year-old patients. In the second, synthetic femoral models based on rapid-prototyping of 3D reconstructed images of patients with cerebral palsy were obtained and were employed to adjust the nail prototype to the morphological changes observed in this disease. In the third, rotational osteotomies were simulated using synthetic femoral models stabilized by the nail and by the AO-ASIF fixed-angle blade plate. Mechanical testing was done comparing both devices in bending-compression and torsion.ResultsThe authors observed proper adaptation of the nail to normal and morphologically altered femoral models, and during the simulated osteotomies. Stiffness in bending-compression was significantly higher in the group fixed by the plate (388.97 ± 57.25 N/mm) than in that fixed by the nail (268.26 ± 38.51 N/mm) as torsional relative stiffness was significantly higher in the group fixed by the plate (1.07 ± 0.36 Nm/°) than by the nail (0.35 ± 0.13 Nm/°).ConclusionsAlthough the device presented adequate design and dimension to fit into the pediatric femur, mechanical tests indicated that the nail was less stable than the blade plate in bending-compression and torsion. This may be a beneficial property, and it can be attributed to the more flexible fixation found in intramedullary devices.

Efeito de regimes de treinamento físico de alto impacto nas propriedades mecânicas de ossos: estudo experimental em ratas wistar

INTRODUCAO: A realizacao de atividade fisica garante beneficios ao tecido osseo uma vez que o estresse provocado pelo carregamento promove adaptacoes positivas em suas propriedades mecânicas, sendo sua utilizacao uma estrategia nao farmacologica para fortalecimento osseo. OBJETIVO: investigar o efeito de protocolos de treinamento de alto impacto com frequencias semanais e periodos diferentes nas propriedades mecânicas de ossos de ratas Wistar. METODOS: Foram utilizadas 54 ratas Wistar, idade media de 10 semanas, divididas em seis grupos (n = 9): GCI (grupo controle, quatro semanas, sedentario), GTI3 (treinou tres vezes por semana durante quatro semanas), GTI5 (treinou cinco vezes por semana, quatro semanas), GCII (grupo controle, oito semanas, sedentario), GTII3 (treinou tres vezes por semana, oito semanas) e GTII5 (treinou cinco vezes por semana, oito semanas). O protocolo de alto impacto consistiu de 10 saltos verticais por sessao. RESULTADOS: Os ossos dos animais que receberam treinamento de alto impacto com frequencia semanal elevada por um periodo maior de tempo mostraram valores superiores de suas propriedades mecânicas forca maxima e rigidez relativa quando comparados aos demais grupos. CONCLUSAO: Os resultados indicam que a realizacao de um protocolo de treinamento de alto impacto na forma de saltos verticais possui efeitos positivos sobre o tecido osseo mesmo com frequencia semanal reduzida, embora a realizacao de uma frequencia semanal maior por um periodo mais elevado garanta melhores resultados.

INFLUENCE of HIGH-IMPACT EXERCISE on BONE IN OSTEOPENIC OVARIECTOMIZED RATS

PC-P40 PREDICTION OF PROXIMAL FEMUR STRENGTH BY A QUANTITATIVE COMPUTED TOMOGRAPHY-BASED FINITE ELEMENT METHOD—CREATION OF PREDICTED STRENGTH DATA OF THE PROXIMAL FEMUR ACCORDING TO AGE RANGE IN A NORMAL POPULATION AND ANALYSIS OF RISK FACTORS FOR HIP FRACTURE Masako Kaneko, Isao Ohnishi, Masahiko Bessho, Satoru Ohashi, Kenji Tobita, Kozo Nakamura University of Tokyo, Department of Orthopaedic Surgery, Bunkyo-ku, Tokyo, JP, Kaken Hospital, Orthopaedics Surgery, Ichikawa-shi, Chiba-ken, JP

Influência do preparo do orifício piloto na ancoragem dos parafusos pediculares

Objective We evaluated the influence of the diameter and the preparation of the pilot hole on the resistance to the pulling out and the strength when inserting pedicle screws with conical internal diameter. Methods Mechanical experiments were performed with pedicle conical screws of 4.2 mm and 5.2 mm diameter. They were inserted in the vertebral pedicles of swine. The hole was manufactured with a drill and probes with different diameters. Results While testing the 4.2 mm screw, the perforation of holes with measure equal or inferior to the lesser internal diameter of the screw increased the torque and the resistance to pull-out strength. Perforations with different instruments have presented similar results. Perforations with probes allowed the holes manufactured with dimensions superior to the lesser internal diameter of the screw to show similar resistance to that of the perforations with dimensions equal to the lesser internal diameter of the implant, made with probes and drills. Conclusion For 4.2 mm screws, the diameter and the preparation of the hole influence the torque and the resistance. For 5.2 mm screws, there is only influence on the insertion torque. There is no correlation between pulling out strength and insertion torque. Level of Evidence II, Therapeutic Studies - Investigating the Results of Treatment.