Enkele aspecten uit de ontwikkeling van het verloskundig instrumentarium

Some aspects of the development of obstetrical instruments The improvement of obstetrical instruments is greatly influenced by mechanical-technical possibilities. Particularly instruments such as levers and forceps, which are exposed to relatively high forces, should be made of hard and tough metals. For that reason the introduction of Sheffield-steel was very important. It offered the possibility to develop a great variety of forceps, including cranioclasts. In addition, for simple obstetric forceps one should also take into account the weight and the mechanical properties of the instrument. The latter depend on the length of the instrument and the position of the centre of rotation. Favourable terms - the least possible compression of the skull during traction - imply that the length of the handles is short in comparison with the length of the blades. Data concerning these factors are derived from the collection of the medical faculty at Leiden, comprising 117 obstetrical forceps. Indeed, 62 instruments belong to the favourable weight classes of 501-750 grams. The ratio in length between handles and blades shows a value of 0,60-0,80 in 36 instruments. From a mechanical point of view the Audibert forceps is very unfavourable, whereas two small-sized variants of the Naegele forceps have extremely low ratios and low weights.