Interspinous devices

It depends what for. These are among the most misused devices in spine surgery: they have been fitted widely outside their indications, as if an implant between the spinous processes were enough to solve any stenosis or instability. Properly indicated they work; wrongly indicated they fail. Before agreeing, ask which of their two correct indications is yours.

The first is facet fusion: rigid clamp-type devices that, in moderate instability, can do the work of pedicle screws. The second is non-pedicle dynamic stabilisation: elastic devices secured with tension bands, such as DIAM or IntraSPINE, useful only in minor instability. Beyond that, no.

It depends on the device and, above all, on how severe the case is. The rigid clamp-type device can replace them in facet fusion, but only in moderate instability and always with bone graft: without graft there is no fusion, however many implants are fitted. In severe instability, or where there is advanced osteoporosis, it does not replace them: there you need the anchorage a screw gives, and fitting a clamp instead is a mistake. The elastic devices never replace screws.

The bad name comes from indiscriminate use, not from the device. An implant that fails where it should never have been placed does not prove that the whole family is useless; it proves the indication was wrong. Properly indicated they have their place, and it is exactly those two.