[Angle-stable fixation of intramedullary nails using the Angular Stable Locking System® (ASLS)].

OBJECTIVE

Greater stability in intramedullary osteosynthesis using angle-stable fixation with intramedullary nails and proximal locking screws. A novel screw-and-sleeve system (ASLS®, Synthes GmbH, Oberdorf, Switzerland) is applied using normal cannulated nails. Decisions can be made intraoperatively.

INDICATIONS

This technology widens the range of indications for intramedullary nailing: The smaller and less stable the fragment requiring fixation, the greater the indication for angular stable fixation of the proximal and/or distal fragment. Femoral, tibial and humeral fractures, intramedullary osteosynthesis in osteoporotic bone and ante- and retrograde nailing. Particularly in the case of retrograde nailing, sustained prevention of nail toggling is achieved.

CONTRAINDICATIONS

None.

SURGICAL TECHNIQUE

Drill with the first drill bit, which has the same core diameter as the screw shaft. Drill the cortex to the external diameter of the sleeve. Place the sleeve on the tip of the screw. The screw-sleeve combination is then advanced through the larger near hole until the sleeve-covered screw tip sits in the locking hole of the intramedullary fixation nail. Advance the screw. As the screw diameter becomes larger, the sleeve expands resulting in an angular stable locking effect. The screw is then advanced until the head of the screw sits on the exposed surface of the cortex. The hole is filled with the expanded part of the screw shaft beneath the screw head. The necessary 1-3 turns are cut by the self-tapping flute on the screw.

POSTOPERATIVE MANAGEMENT

According to experience to date, this form of angle-stable fixation enables earlier and/or greater partial mobilization or earlier full mobilization. In all other respects, the guidelines for aftercare in intramedullary nailing apply.

RESULTS

A multi-center pilot study has shown the technique to be reproducible and simple. There have been no complications using this technique to date. Biomechanical laboratory studies have demonstrated that stability with respect to axial and torsional loading is statically and dynamically higher than with conventional nailing. Device failure occurs later. Further applications as well as results of a prospective randomised study currently under way will show how great the clinical advantages ultimately prove to be.