The spike on the top is supposed to be to provide improved sensitivity for a vertically polarised signal but frankly I doubt it would make much difference whether it was present or not. The metal screw that attaches it makes an electrical connection and I would suspect the wire inside is possibly a helical coil to effectively make it electrically longer, so replacing it with a rod would be a waste of time.
Note that when DSO came along the industry started telling people that these aerials are not 'digital' so replacement would be needed. Rubbish! An aerial picks up a signal irrespective of what version it is be it analogue TV, digital TV, AM or FM radio or DAB provided it is within the frequency band for which the aerial is designed to work. You should have a Status 530 which IME are much better on digital than they were on analogue for technical reasons. If it has purple writing on the dome then the amplifier is inside the aerial and the connection box is just a power supply; if the writing is orange or red then the amplifier is in the box, not the aerial. If the latter you may achieve some benefit but changing the amp to one of the newer models such as Status VP3 or one from Fringe Electronics at Mansfield but try it before your spend your money - you might be surprised.