[en] INTRODUCTION FP instability is a complex problem, of multifactorial origin, in which several predisposing factors come into play. Since its initial description in the early 90s of the last century, the reconstruction of the medial patellofemoral ligament (LPFM) has become very popular in the treatment of femoro-patellar instability (FP), due to the recognized role of this ligament as the main medial stabilizer of the patella. and facilitator of the kinetics of said joint. SCIENTIFIC JUSTIFICATION Although the reconstruction of the LPFM is considered as one of the basic aspects in the treatment of FP instability, the great variety of techniques described to carry it out, have aroused great controversy in the scientific community and the interest for the development of this thesis. The project is structured as a compendium of 5 publications, which analyze three different aspects -anatomic, clinical and biomechanical -of a specific type of LPFM reconstruction that has been called quasianatomic. The hypotheses assumed that: 1- That the behavior of the quasianatomic technique would be good in terms of stability and complications 2- That its results would be comparable with those of the anatomical technique (considered the gold standard) 3- That the biomechanical behavior of the neoligament it would seem to the original LPFM 4- That a finite element model could be used to study the behavior of the reconstruction in multiple clinical situations 5- That the gracilis tendon is the best graft to replace the LPFM and that the reconstruction produces contact pressures on the surface articular of the FP similar to the originals. Regarding the designs, they are: 1-Observational, retrospective, clinical and radiological in 36 consecutive patients (Clinical and radiological outcomes after a quasi-anatomical reconstruction of medial patellofemoral ligament with gracilis tendon autograft. KSSTA2017). 2- Prospective, comparative, multicenter, not randomized in two homogeneous series (Isolated reconstruction of medial patellofemoral ligament with an elastic femoral fixation leads to excellent clinical results. KSSTA. 2020) 3- Anatomical, cadaveric, in ten frozen knees (The anatomy and isometry of a quasi-anatomical reconstruction of the medial patellofemoral ligament. KSSTA. 2017) 4 and 5-Experimental, one to develop and validate a parametric model of finite elements of the FP joint (Parametricfinite element model of medial patellofemoral ligament reconstruction model development and clinical validation. J Exp Orthop. 2019) and, another, to analyze both variations of graft length in the different types of LPFM reconstruction such as contact pressures in the FP (Evaluation of Patellar Contact Pressure Changes after Static versus Dynamic Medial Patellofemoral Ligament Reconstructions Using a Finite Element Model. J Clin Med. 2019) RESULTS 1- The Quasianatomic technique gave good clinical and radiological results. No reluxations and few complications. 2- When compared with the standard anatomical technique, no significant differences were seen. 3- The biomechanical behavior of the quasianatomic reconstructive technique was of the isometric type, similar to that of the original ligament. 4 and 5. The finite element parametric model was reliable and reproducible for the study of FP instability. The contact pressures generated in the FP by the quasianatomic RLPFM are better than those of the anatomical technique and more similar to those of the original LPFM. CONCLUSIONS The quasianatomic reconstruction technique with gracilis and elastic fixation in the hiatus of the adductor magnus, provides clinical, radiological and anatomical results similar to those of the standard anatomical technique and biomechanically more similar to that of the original LPFM.

[es] INTRODUCCIÓNLa inestabilidad FP es un problema complejo, de origen multifactorial, en el que varios factores predisponentes entran en juego. Desde su descripción inicial a principios de los años 90 del siglo pasado,la reconstrucción del ligamento patelofemoral medial (LPFM) ha adquirido una gran popularidaden el tratamiento de la inestabilidad femoro-patelar (FP),debido alareconocida funciónde este ligamentocomo principal estabilizador medialde la rótula y facilitador de la cinéticade dicha articulación. JUSTIFICACIÓN CIENTÍFICAAunquela reconstrucción del LPFMes consideradacomo unode los aspectos básicos en el tratamientola inestabilidad FP,la gran variedad de técnicas descritas para realizarlo,han suscitado una gran controversia en la comunidad científica y el interés para el desarrollode esta tesis.HIPÓTESIS Y OBJETIVOS El proyecto estáestructuradocomo un compendio de 5 publicaciones,que analizantres diferentes aspectos -anatómico, clínico ybiomecánico -de un tipo específico de reconstrucción del LPFM que se ha denominadocuasianatómica.Las hipótesis suponían que:1-Que el comportamiento de la técnica cuasianatómica sería bueno en términos de estabilidad y complicaciones2-Que sus resultados serían comparables con los de la técnica anatómica (considerada el patrón oro)3-Que el comportamiento biomecánico del neoligamento se parecería al del LPFM original4-Que un modelo de elementos finitos podría servir para estudiar el comportamiento de la reconstrucción en multiples situaciones clínicas5-Que el tendón gracilis es el mejor injerto para sustituir al LPFM y que la reconstrucción produce presiones de contactoen la superficie articular de laFP similares a las originalesRespecto a los diseños son:1-Observacional,retrospectivo, clínico y radiológico en36 pacientesconsecutivos(Clinicaland radiological outcomes after a quasi-anatomical reconstruction of medial patellofemoral ligament with gracilis tendon autograft. KSSTA2017). 2-Prospectivo, comparativo,multicéntrico,no aleatorizado en dos series homogéneas (Isolated reconstruction of medial patellofemoral ligament with an elastic femoral fixation leads to excellent clinical results. KSSTA. 2020)3-Anatómico, cadavérico,en diez rodillas congeladas(The anatomy and isometry of a quasi-anatomical reconstruction of the medial patellofemoral ligament. KSSTA. 2017) 4 y 5-Experimentales,uno para desarrollar y validar un modelo paramétrico de elementos finitos de la articulación FP (Parametricfinite element model of medial patellofemoral ligament reconstruction model development and clinical validation. J Exp Orthop. 2019) y,otro,para analizar tanto variaciones de longitud del injerto en los diferentes tipos de reconstrucción del LPFM comola presiones de contacto en la FP (Evaluation of Patellar Contact Pressure Changes after Static versus Dynamic Medial Patellofemoral Ligament Reconstructions Using a Finite Element Model. J Clin Med. 2019) RESULTADOS1-La técnica cuasianatómica dio buenresultado clínico y radiológico. No reluxaciones y pocas complicaciones.2-Alcompararlacon la técnica anatómicaestándarno se vieron diferencias significativas.3-Elcomportamiento biomecánicode la técnica reconstructiva cuasianatómica fue del tipo isométrico, similar al del ligamento original.4 y 5. El modelo paramétrico de elementos finitos resulto fiable y reproducible para el estudio de la inestabilidad FP. Las presiones de contacto generadas en la FP por la RLPFM cuasianatómicason mejores que las de la técnica anatómicay mas parecidas a las del LPFM original.CONCLUSIONESLa técnica de reconstrucción cuasianatómicacon gracilis y fijación elástica en el hiato del adductor magno,aporta unos resultados clínicos, radiológicos y anatómicossemejantes a los de latécnica anatómicaestándar y biomecánicamentemásparecidos al delLPFM original.