Rodrigo César Rosa

The effect of repetitive pilot-hole use on the insertion torque and pullout strength of vertebral system screws.

Study Design. In vitro biomechanical investigation of the screw-holding capacity. Objective. To evaluate the effect of repetitive screw-hole use on the insertional torque and retentive strength of vertebral system screws. Summary and Background Data. Placement and removal of vertebral system screws is sometimes necessary during the surgical procedures in order to assess the walls of the pilot hole. This procedure may compromise the holding capacity of the implant. Methods. Screws with outer diameter measuring 5, 6, and 7 mm were inserted into wood, polyurethane, polyethylene, and cancellous bone cylindrical blocks. The pilot holes were made with drills of a smaller, equal, or wider diameter than the inner screw diameter. Three experimental groups were established based on the number of insertions and reinsertions of the screws and subgroups were created according to the outer diameter of the screw and the diameter of the pilot hole used. Results. A reduction of screw-holding capacity was observed between the first and the following insertions regardless the anchorage material. The pattern of reduction of retentive strength was not similar to the pattern of torque reduction. The pullout strength was more pronounced between the first and the last insertions, while the torque decreased more proportionally from the first to the last insertions. Conclusion. Insertion and reinsertion of the screws of the vertebral fixation system used in the present study reduced the insertion torque and screw purchase.

Esteira com velocidade controlada para captação da marcha

Histological and electrophysiological methods for evaluation of peripheral nerve regeneration do not faithfully reproduce the functional index of limbs, even in controlled experimental conditions. Some methods of functional evaluation have been proposed, but their correlation to histological and electrophysiological data is not completely established, requiring more investigations with improvement of collection, management and processing of obtained data. In this study we developed a treadmill with controlled speed for recording footprint of rats submitted to different kinds of sciatic, fibular and tibial nerve lesions. The footprints were obtained on a walking track by means of a webcam connected to the treadmill and a computer with capacity to record the gait that will be submitted to functional evaluation. The developed treadmill allows the collection and filming of gaits and it has been tested in current experimental studies in rats with sciatic nerve lesion submitted to different kinds of treatment. The treadmill also enables researchers to record gait with constant, controlled and pre-established speed, with the possibility of direct visualization through the treadmill wall. In this manner, some variables that could damage the results of the research are resolved.

Osteotomia alta da tíbia com cunha de abertura medial: relevância biomecânica da cortical oposta

OBJETIVO: Avaliar o impacto da integridade da cortical lateral osteo-tomia alta de tibia (OAT) com cunha de abertura. METODOS: Modelos experimentais artificiais em poliuretano foram fixados com placa DCP® 4,5mm. Cunhas de abertura foram confeccionadas para simular a distracao da osteotomia alta da tibia. Realizadas falhas na cortical lateral para simular fraturas e fixadas com diferentes tipos de parafusos. Ensaios de torcao e compressao axial foram realizados. 04 diferentes grupos foram constituidos. RESULTADOS: As medidas de torcao registradas no grupo com cortical integra foram superiores aquelas obtidas no grupo com cortical rompida (p 0,05). As medidas de compressao obtidas no grupo com cortical integra foram superiores aos demais grupos (p 0,05). CONCLUSAO: A cortical lateral integra agrega estabilidade as osteotomias com cunha de abertura medial. Modelo com cortical integra evidenciou superioridade biomecânica em rigidez nos ensaios de torcao e compressao. Nos ensaios torcionais, os modelos com falha de continuidade cortical com parafusos de estabilizacao lateral de compressao ou de posicao apresentaram equivalencia aos modelos com cortical integra.

Is the History of Falls an Indicative of Greater Decline in Quadriceps Muscle Function and Postural Sway

To evaluate whether a history of falls is directly related to the quadriceps muscular function and body sway, 26 elderly women were divided on the basis of the presence or absence of a history of falls. Evaluation of muscular power and anteroposterior and mediolateral displacements of center of pressure during consecutive stand and sit 5 times were performed. Fallers exhibited higher mediolateral displacement than nonfallers. No differences were observed for quadriceps power and for sit-to-stand time between groups (P < .05). The fall history was not related to the quadriceps muscular function or to the anteroposterior displacement during sit to stand.

Análise biomecânica de variáveis relacionadas à resistência ao arrancamento dos parafusos do sistema de fixação vertebral

OBJECTIVE: To observe the relevance of the pilot hole in the different manners of preparation: dull-tipped probe, cutting-tip probe, and burr, for the purpose of evaluating the level of pullout strength of screws with different diameters. METHODS: Screws of 5, 6, and 7 mm were inserted in the bovine bone test samples. The pilot hole was made with the dull-tipped probe, the cutting-tip probe, and burr. The perforation diameter was smaller, equal, and larger than the inner diameter of the screw. Mechanical pullout assays were performed in the three diameters for each manner of preparation of the pilot hole after inserting the implant. The mechanical assays were performed in an Emic®, Software Tesc 3.13 universal machine with load cell of 2000 N, load application speed of 2 mm/min, pre-load of 5 N, and accommodation time of 10 seconds. The property evaluated in the mechanical assays was the maximum pullout strength. RESULTS: In the group with 5 mm and 6 mm screws, and increase was observed in the pullout strength when the pilot hole diameter was smaller than the inner diameter of the screw in all manners of preparation (dull-tipped probe, cutting-tip probe, and burr). No statistical difference was seen in the seven millimeter screw group for all perforation diameters and manners of preparing the pilot hole. CONCLUSION: The pilot hole diameter has an influence upon the pullout strength of the screws in the vertebral fixation system. The making of a pilot hole with diameter larger than the inner diameter of the screw reduces the pullout strength of the implant, irrespective of the manner of preparation of the pilot hole.

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.

Second hand tobacco smoke adversely affects the bone of immature rats

OBJECTIVES: To evaluate the influence of secondhand cigarette smoke exposure on longitudinal growth of the tibia of growing rats and some parameters of bone quality. METHODS: Forty female rats were randomly divided into four groups: control: rats were sham exposed; 30 days: rats were exposed to tobacco smoke for 30 days; 45 days: rats were exposed to tobacco smoke for 45 days; and 60 days: rats were exposed to tobacco smoke for 60 days. Blood samples were collected to evaluate the levels of cotinine and alkaline phosphatase. Both tibias were dissected and weighed; the lengths were measured, and the bones were then stored in a freezer for analysis of bone mineral content and mechanical resistance (maximal load and stiffness). RESULTS: Exposure of rats to tobacco smoke significantly compromised bone health, suggesting that the harmful effects may be time dependent. Harmful effects on bone growth were detected and were more pronounced at 60-day follow-ups with a 41.8% reduction in alkaline phosphatase levels (p<0.01) and a decrease of 11.25% in tibia length (p<0.001). Furthermore, a 41.5% decrease in bone mineral density was observed (p<0.001), leading to a 42.8% reduction in maximum strength (p<0.001) and a 56.7% reduction in stiffness (p<0.001). CONCLUSION: Second hand cigarette smoke exposure in rats affected bones that were weaker, deforming them and making them osteopenic. Additionally, the long bone was shorter, suggesting interference with growth. Such events seem to be related to time of exposure.

Anomalous bilateral contribution of extensor pollicis longus and muscle fusion of the first compartment of the wrist

Knowledge of the anatomical variations of the muscles of the first dorsal compartments of the wrist is clinically relevant to De Quervains tenosynovitis and to reconstructive surgeries. In the literature, there are many reports of the presence of multiple insertion tendons in the first dorsal compartment of the wrist, but few reports describe occurrences of fusion and muscle contributions. This case report describes an anomalous bilateral contribution of the extensor pollicis longus. This anomalous contribution was found through a slender auxiliary tendon that crossed laterally under the extensor retinaculum, entered the first dorsal compartment of the wrist and merged with the tendon of the extensor pollicis brevis muscle. In the same cadaver in which this contribution was present, there was atypical muscle fusion of the abductor pollicis longus muscle and extensor pollicis brevis muscle. In conclusion, anomalous bilateral contribution of the extensor pollicis longus muscle and atypical muscle fusion, concomitant with a variant insertion pattern, are the highlight of this case report. Furthermore, it is concluded that additional tendons may be effectively used in reconstructive surgeries, but that there is a need for knowledge of the possible numerical and positional variations of these tendons, with a view to making more effective surgical plans.

Influência do macheamento do orifício piloto nos parafusos cervicais anteriores

OBJECTIVE: Experimentally analyze the influence of the pilot hole tapping on the mechanical properties and the bone-implant interface of anterior cervical screw. METHODS: Eight shorn Santa Ines sheep were used in the study. In cervical segments C2-C7 of the column 2.5mm pilot holes were made on both sides of the vertebra. On the right side of the vertebra tapping was done before the insertion of the cortical screw of 3.5mm, and on the left side the implant was placed without tapping the pilot hole. Mechanical assays were performed to assess the strength of pullout as well as a histomorphometric study of bone-implant interface during the acute phase and eight weeks after implant placement. The insertion torque was measured during implant placement. RESULTS: The insertion torque and pullout strength were higher for implants placed without tapping the pilot hole. The bone-implant interface showed greater area of bone contact and greater bone area within the implant thread on the screws implanted without prior tapping. No differences were observed in the bone outside the thread pitch of the implant. CONCLUSIONS: Tapping the pilot hole reduces insertion torque and pullout strength of the implant in both acute and chronic phases, and reduces the area of bone-implant contact and the bone area within the thread pitch.ResUMO Objetivo: Analisar experimentalmente a influencia do macheamento do orificio piloto nas propriedades mecânicas e na interface osso-implante do parafuso cervical anterior. Metodos: Oito carneiros da raca Santa Ines deslanados foram utilizados no estudo. Nos segmentos vertebrais cervicais de C2-C7 foram realizados orificios piloto de 2,5mm, de ambos os lados da vertebra. No lado direto da vertebra foi realizado o macheamento previamente a insercao do parafuso cortical de 3,5mm, e no lado esquerdo o implante foi colocado sem o macheamento do orificio piloto. Foram realizados ensaios mecânicos para avaliar a forca de arrancamento dos implantes e estudo histomorfometrico da interface osso-implante na fase aguda e oito semanas apos a colocacao dos implantes. O torque de insercao foi mensurado durante a colocacao dos implantes. Resultados: O torque de insercao e a resistencia ao arrancamento dos implantes foram maiores nos implantes colocados sem o macheamento do orificio piloto. A interface osso-implante apresentou maior area de contato osseo e maior area ossea no interior da rosca do implante nos parafusos implantados sem o macheamento previo. Nao foi observado diferenca na area ossea fora do passo de rosca do implante. Conclusoes: O macheamento do orificio piloto reduz o torque de insercao e a resistencia ao arrancamento do implante na fase aguda e cronica, e reduz a area de contato osso-implante e area de osso no interior do passo de rosca. Descritores: Fixacao de fratura; Coluna vertebral; Parafusos osseos; Histologia; Macheamento.

Influencia del taladramiento del agujero piloto en tornillos cervicales anteriores

OBJECTIVE: Experimentally analyze the influence of the pilot hole tapping on the mechanical properties and the bone-implant interface of anterior cervical screw. METHODS: Eight shorn Santa Ines sheep were used in the study. In cervical segments C2-C7 of the column 2.5mm pilot holes were made on both sides of the vertebra. On the right side of the vertebra tapping was done before the insertion of the cortical screw of 3.5mm, and on the left side the implant was placed without tapping the pilot hole. Mechanical assays were performed to assess the strength of pullout as well as a histomorphometric study of bone-implant interface during the acute phase and eight weeks after implant placement. The insertion torque was measured during implant placement. RESULTS: The insertion torque and pullout strength were higher for implants placed without tapping the pilot hole. The bone-implant interface showed greater area of bone contact and greater bone area within the implant thread on the screws implanted without prior tapping. No differences were observed in the bone outside the thread pitch of the implant. CONCLUSIONS: Tapping the pilot hole reduces insertion torque and pullout strength of the implant in both acute and chronic phases, and reduces the area of bone-implant contact and the bone area within the thread pitch.ResUMO Objetivo: Analisar experimentalmente a influencia do macheamento do orificio piloto nas propriedades mecânicas e na interface osso-implante do parafuso cervical anterior. Metodos: Oito carneiros da raca Santa Ines deslanados foram utilizados no estudo. Nos segmentos vertebrais cervicais de C2-C7 foram realizados orificios piloto de 2,5mm, de ambos os lados da vertebra. No lado direto da vertebra foi realizado o macheamento previamente a insercao do parafuso cortical de 3,5mm, e no lado esquerdo o implante foi colocado sem o macheamento do orificio piloto. Foram realizados ensaios mecânicos para avaliar a forca de arrancamento dos implantes e estudo histomorfometrico da interface osso-implante na fase aguda e oito semanas apos a colocacao dos implantes. O torque de insercao foi mensurado durante a colocacao dos implantes. Resultados: O torque de insercao e a resistencia ao arrancamento dos implantes foram maiores nos implantes colocados sem o macheamento do orificio piloto. A interface osso-implante apresentou maior area de contato osseo e maior area ossea no interior da rosca do implante nos parafusos implantados sem o macheamento previo. Nao foi observado diferenca na area ossea fora do passo de rosca do implante. Conclusoes: O macheamento do orificio piloto reduz o torque de insercao e a resistencia ao arrancamento do implante na fase aguda e cronica, e reduz a area de contato osso-implante e area de osso no interior do passo de rosca. Descritores: Fixacao de fratura; Coluna vertebral; Parafusos osseos; Histologia; Macheamento.