Intraoperative joint-line determination during revision TKA is difficult and no method exists to plan the position preoperatively. Two questions need to be answered: to which extent does the joint line differ from its anatomic position after revision TKA if it has only been determined intraoperatively, and can the joint line be calculated preoperatively based on the transepicondylar width. Of 22 consecutive patients with complete preoperative (before and after primary TKA) and postoperative (after revision TKA) radiograph documentation, the joint-line position was measured on plane radiographs using the medial epicondyle as a reference. On another set of 45 consecutive patients with no knee disorders other than meniscal lesions, the transepicondylar axis width (TEAW) and the perpendicular distance from the medial and lateral epicondyles to the joint line were measured twice by two independent observers on plane AP radiographs of the knee. Significant joint-line alterations were observed after primary and revision TKA, implicating that a method for preoperative planning is needed. Because a linear correlation between the TEAW and the perpendicular distance from the epicondyles to the joint-line tangent was found, the ratio is useful to calculate the true joint-line position from the TEAW before revision TKA.

In response to the Lisbon earthquake of 1 November 1755, and the subsequent seismic activity in Europe, Kant wrote several articles on earthquakes and volcanic phenomena. Full translations of the most important parts of these articles are presented, and summaries for the remainder. Kant developed a carefully worked out theory to account for seismic activity, based on his reading of the scientific literature, the reports received in K6nigsberg of the Lisbon earthquake and associated events, and his general theory of the origin of the Earth's crust, as presented in his Allgemeine Naturgeschichte of 1755. Following L6mery, Kant supposed that volcanic action was due to the subterranean combination of sulphur and iron, and he rejected the suggestion that earthquakes might be due to the gravitational pull of heavenly bodies. Kant's theory was naturalistic, but his account was not wholly divorced from physicotheological considerations.

A translation of Kant's early paper, 'Die Frage, ob die Erde veralte, physikalisch erwogen' ('The question, whether the Earth is ageing, considered physically') is presented, and the main features of his position on this question in 1754 are summarized. In that year, Kant believed that the Earth was ageing, and that it was about 6000 years old. The paper allows us to understand the approximate outline of Kant's general 'theory of the Earth', and the relation of this theory to the cosmogony that he propounded in 1755. His ideas on the processes of erosion, and the formation of rivers, deltas and sandbanks, are noteworthy, and provide a contribution to the eighteenth-century literature on the denudation dilemma. Kant's general theory of erosion and deposition was, it seems, based to a significant extent on his knowledge of the geographical features of the K6nigsberg district. The general teleological position underpinning his philosophy may be discerned in this early paper, and he may be thought of as having been trying to orientate himself in space and time, so to speak, before undertaking his major reconstructions in philosophy.

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