Preoperative Planning of Periacetabular Osteotomy (PAO)

Pelvic osteotomies improve containment of the femoral head in cases of developmental dysplasia of the hip or in femoroacetabular impingement due to acetabular retroversion. In the evolution of osteotomies, the Ganz Periacetabular Osteotomy (PAO) is among the complex reorientation osteotomies and allows for complete mobilization of the acetabulum without compromising the integrity of the pelvic ring. For the complex reorientation osteotomies, preoperative planning of the required acetabular correction is an important step, due to the need to comprehend the three-dimensional (3D) relationship between acetabulum and femur. Traditionally, planning was performed using conventional radiographs in different projections, reducing the 3D problem to a two-dimensional one. Known disturbance variables, mainly tilt and rotation of the pelvis make assessment by these means approximate at the most. The advent of modern enhanced computation skills and new imaging techniques gave room for more sophisticated means of preoperative planning. Apart from analysis of acetabular geometry on conventional x-rays by sophisticated software applications, more accurate assessment of coverage and congruency and thus amount of correction necessary can be performed on multiplanar CT images. With further evolution of computer-assisted orthopaedic surgery, especially the ability to generate 3D models from the CT data, examiners were enabled to simulate the in vivo situation in a virtual in vitro setting. Based on this ability, different techniques have been described. They basically all employ virtual definition of an acetabular fragment. Subsequently reorientation can be simulated using either 3D calculation of standard parameters of femoroacetabular morphology, or joint contact pressures, or a combination of both. Other techniques employ patient specific implants, templates or cutting guides to achieve the goal of safe periacetabular osteotomies. This chapter will give an overview of the available techniques for planning of periacetabular osteotomy.

How Teresa and Maria Margaretha migrated to Nordstrand: Translation of Relics and Transformation of a German Island into a Catholic Dutch enclave in the 17th century

When on 26 May 1662 the founding first stone was laid for a new church on the island Nordstrand at the coast of Schleswig, relics of Teresa of Avila (1515-1582) and of the Dutch Carmelite abbess Maria Margaretha ab Angelis (1605-1658) were inserted. This church was built for Dutch dyke builders who were called to reconstruct the island after its destruction by flood in 1634; coming from a Catholic background and from the Dutch Republic which was at war with Spain at that time, the dyke builders and their families were guaranteed religious freedom in the Lutheran duchy of Holstein. In this paper, the reasons for the choice for the Spanish mystic Teresa of Avila and for the Dutch Carmelite abbess Maria Margaretha are discussed. The latter patroness was never beatified but had died in the smell of holiness; after her death several miracles were ascribed to her. It is understandable that migrants brought relics of their appreciated holy persons who would remind them of their homeland. The paper will first shortly introduce the two patronesses of the church. In the second part, the reasons for this choice will be discussed. Behind this translation of relics not only spiritual reasons played a role. The function of the translation of the saints was first to keep up geographical and political connections with the old country (both Spain and the Netherlands), secondly to perpetuate personal-familial relationships (esp. with Maria Margaretha), thirdly to strengthen the confessional identity in a non-Catholic environment. Fourthly the transfer brought a certain model of Christian life and reform to the new place of living, which in the second part of the 17th century became marked as “Jansenist”. The paper shows the transformation of the island into an enclave of Dutch Catholic culture.