Planeamento pré-cirúrgico da técnica de avanço da tuberosidade tibial: estudo comparativo de distintos métodos
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2019-02-15
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A técnica de Avanço da Tuberosidade Tibial (TTA) assenta no princípio da neutralização da força de cisalhamento tibiofemoral através da obtenção de um ângulo do ligamento patelar (ALP) de 90º, durante a extensão fisiológica completa do membro, por meio do avanço da tuberosidade tibial (TT), de modo a eliminar a subluxação cranial da tíbia (Montavon et al., 2002). Para o alcance desta meta geométrica é necessário um planeamento pré-cirúrgico criterioso, que deve aliar um método de determinação do declive da meseta tibial a uma técnica de mensuração do avanço, aplicados numa radiografia mediolateral do joelho (Cadmus et al., 2014). Atualmente, há estudos que suscitam dúvidas sobre a consistência das metodologias de planeamento pré-cirúrgicas convencionais usadas para a TTA (Hoffman, et al., 2006; Cadmus et al., 2014) o que levou alguns cirurgiões a abraçar uma alternativa redutora que se baseia na associação entre o peso corporal do cão e a caixa espaçadora a utilizar, explícita no formato de tabela (Palmer, 2011). Ora, este método é questionável do ponto de vista científico da TTA, no entanto, nunca foi testado a nível clínico. Este estudo teve como objetivo inicial comparar dois métodos de planeamento baseados no peso corporal do animal, com a metodologia de planeamento de referência. Foram analisados 21 cães sujeitos a TTA, intervencionados por dois cirurgiões, que utilizaram, cada um, as respetivas tabelas “peso - caixa espaçadora” como métodos de planeamento pré-cirúrgico. O autor aplicou, depois, o método de planeamento de referência – método da tangente comum – para calcular o avanço da TT necessário para os mesmos cães, segundo os pressupostos da técnica. Para além disso, foi aferido o ALP radiográfico pós-cirúrgico, de modo a avaliar os métodos de planeamento usados pelos cirurgiões. Por último, o autor mediu alguns parâmetros anatómicos da tíbia dos cães em estudo e investigou a sua relação com o avanço da TT. Encontraram-se diferenças estatisticamente significativas entre o método de referência e os métodos baseados nos pesos (p < 0,05). Da mesma forma, ambos os grupos intervencionados apresentaram um ALP médio pós-cirúrgico aquém do objetivo para a neutralização da força de cisalhamento tibiofemoral, no entanto, o método Vezzoni adaptado foi o que mais se aproximou do ambicionado ALP de 90°. Por fim, foi demonstrado que, para este grupo amostral, 80% do avanço da TT, estimado pelo método de referência, pode ser explicado por parâmetros anatómicos inerentes à tíbia proximal do cão. Conclui-se, então, que os métodos de planeamento baseados no peso apresentam algumas limitações na estimativa do avanço da TT, pelo que o autor não recomenda o seu uso em substituição dos métodos convencionais. Com este estudo o autor propõe um modelo matemático, composto por um par de medidas anatómicas, que é capaz de predizer a amplitude de avanço da TT de forma satisfatória (R2 ajustado = 0,80), sendo uma alternativa viável às tabelas “peso - caixa” para o planeamento précirúrgico da TTA.
The Tibial Tuberosity Advancement (TTA) technique relies on the principle of tibiofemoral shear force neutralization by obtaining a 90º patellar tendon angle (PTA) during the complete physiological extension of the limb by advancing the tibial tuberosity (TT) in order to eliminate cranial subluxation of the tibia (Montavon et al., 2002). In order to reach this geometric goal, careful presurgical planning is necessary, which should ally a method to determine the slope of the tibial plateau to a technique to measure the advancement, applied in a mediolateral x-ray of the knee (Cadmus et al., 2014). Currently, there are studies that raise doubts about the consistency of the conventional presurgical planning methodologies used for TTA (Hoffman et al., 2006; Cadmus et al., 2014), which has led some surgeons to embrace a reductive alternative based on the association between the dog's body weight and the cage to be used, explicit in a table format (Palmer, 2011). However, this method is questionable from the scientific point of view of TTA, nevertheless, it has never been tested at a clinical level. The objective of this study was to compare two methods based on the body weight of the animal with the reference planning methodology. Twenty-one dogs were submitted to TTA by two surgeons, the surgeons used their respective "body weight - cage" tables as presurgical planning methods. In a different way, the author applied the reference planning methodology – the common tangent method – to calculate the advance of the TT necessary for the same dogs, according to the assumptions of the technique. In addition, in the postsurgical period, the final radiographic PTA was measured in order to evaluate the planning methods used by the surgeons. In the final part of the study, the author measured some anatomical parameters of the tibia of the dogs under study and evaluated if these parameters were implicated with the progression of the TT. Statistically significant differences were found between the reference method and weight-based methods (p < 0.05). In the same way, both groups attained a mean postsurgical PTA higher than 90º, however, the adapted Vezzoni method was the one that came closer to a PTA of 90°. Finally, the author showed that, for this sample group, 80% of the TT advance, estimated by the reference method, can be explained by anatomical parameters inherent to the proximal tibia of the dog. In conclusion, weight-based planning methods presented some limitations estimating TT advancement, so the author does not recommend its use as a substitute for conventional methods. With this study the author created a mathematical model, composed of a pair of anatomical measures, that can satisfactorily predict the TT advance amplitude (adjusted R2 = 0.80), being a viable alternative to the "body weight - cage" method for presurgical TTA planning.
The Tibial Tuberosity Advancement (TTA) technique relies on the principle of tibiofemoral shear force neutralization by obtaining a 90º patellar tendon angle (PTA) during the complete physiological extension of the limb by advancing the tibial tuberosity (TT) in order to eliminate cranial subluxation of the tibia (Montavon et al., 2002). In order to reach this geometric goal, careful presurgical planning is necessary, which should ally a method to determine the slope of the tibial plateau to a technique to measure the advancement, applied in a mediolateral x-ray of the knee (Cadmus et al., 2014). Currently, there are studies that raise doubts about the consistency of the conventional presurgical planning methodologies used for TTA (Hoffman et al., 2006; Cadmus et al., 2014), which has led some surgeons to embrace a reductive alternative based on the association between the dog's body weight and the cage to be used, explicit in a table format (Palmer, 2011). However, this method is questionable from the scientific point of view of TTA, nevertheless, it has never been tested at a clinical level. The objective of this study was to compare two methods based on the body weight of the animal with the reference planning methodology. Twenty-one dogs were submitted to TTA by two surgeons, the surgeons used their respective "body weight - cage" tables as presurgical planning methods. In a different way, the author applied the reference planning methodology – the common tangent method – to calculate the advance of the TT necessary for the same dogs, according to the assumptions of the technique. In addition, in the postsurgical period, the final radiographic PTA was measured in order to evaluate the planning methods used by the surgeons. In the final part of the study, the author measured some anatomical parameters of the tibia of the dogs under study and evaluated if these parameters were implicated with the progression of the TT. Statistically significant differences were found between the reference method and weight-based methods (p < 0.05). In the same way, both groups attained a mean postsurgical PTA higher than 90º, however, the adapted Vezzoni method was the one that came closer to a PTA of 90°. Finally, the author showed that, for this sample group, 80% of the TT advance, estimated by the reference method, can be explained by anatomical parameters inherent to the proximal tibia of the dog. In conclusion, weight-based planning methods presented some limitations estimating TT advancement, so the author does not recommend its use as a substitute for conventional methods. With this study the author created a mathematical model, composed of a pair of anatomical measures, that can satisfactorily predict the TT advance amplitude (adjusted R2 = 0.80), being a viable alternative to the "body weight - cage" method for presurgical TTA planning.
Descrição
Dissertação de Mestrado em Medicina Veterinária apresentada à Universidade de Trás-os-Montes e Alto Douro
Palavras-chave
TTA , ALP , TT , planeamento pré-cirúrgico