15/11/2009
AO Technical Commission Approved

Tips and Tricks for Removing Problematic Implants: Screws

Introduction

Difficulties may be encountered in certain cases when removing conventional screws and metal plates and, in particular, locking screws securing plates and internal fixators.

Prevention

  • Use a new screwdriver with undamaged hex tip.
  • If a hexagon socket screw is damaged during assembly, it should be replaced before the next stage of the operation.
  • In case of locking screws, the correct tightening torque must be applied. Use the correct torque limiter.
  • If the locking screws are fixed angle, avoid wrong angulation.
  • Use of the available insertion guide and compliance with the instructions in the operating manual are strongly recommended.

Removing

  • From the outset, only use undamaged, not worn out screwdrivers. From the outset, only use undamaged screwdrivers to prevent stripping of the recess. Check the screwdriver yourself. If the screwdriver blade slips, the internal recess of the hexagon socket screw will be damaged. For this reason, only the best screwdriver is good enough for removal.
  • The hexagon socket must be free from any obstruction down to the base of the recess, so that the entire length of the screwdriver tip can be inserted.

If the hexagon socket has been enlarged (rounded corners) (Fig 1):

  • Use a tapered, left-hand thread extraction screw (Fig 2). Always use the extraction screw with the biggest possible diameter.
  • First, screw the tapered, left-hand thread extraction screw directly into the damaged hexagon socket.
  • If this fails to achieve the desired result, or if the extraction screw is not exactly the right size, the hexagon socket can be drilled out slightly oversize (see below) without cutting off the head. A left-hand thread extraction screw of the correct size can then be inserted into the now-cylindrical hole.
  • As it is turned in an anticlockwise direction, the extraction screw must cut into the hexagon socket. The diameter and length of the extraction screw must be such that the taper does not project as far as the base of the recess (Fig 3). The extractor pin can then no longer move forward.

If a screw is jammed or damaged to such an extent that it is no longer possible to remove it using an extraction screw:

  • The head of the screw must be drilled out in such a way that it is removed from the shaft (Fig 4). The same procedure applies if an instrumentregardless of whether it is a screwdriver or an extraction screwbreaks off inside the hexagon socket (Fig 5).
  • Drilling out without a suitable drill bit and tools is a major problem.
  • New instruments for drilling out are now available: Carbide drill bits should be used for drilling out. We now have 4.0 mm and 6.0 mm carbide drill bits (Fig 6). Due to production engineering constraints, these drill bits are short. If required, they can be extended with the aid of a screwdriver extension. This ensures that the drill bit is sufficiently long.
  • In addition, especially hardened HSS drill bits can be used. In every discussion about the best drill bits for each application, the carbide drill bit has proven to be by far the best and latest all-round drill bit. These carbide drill bits are disposable and are intended for single use. During sterilization they can cause a film of rust to develop.
  • The drill suction device is a very helpful instrument in cases of problematic screw removal (both locked and conventional) (see page 44, Drill Suction Device). It allows an efficient aspiration of the drill chips while at the same time cooling and lubricating the drill bit. The lubricating provides the drilling procedure. The drill sleeve provides guidance of the drill and protection of the surrounding soft tissue.

Screw shafts:

  • Can be left in place.
  • However, if they have to be removed, an attempt should be made to grasp the shafts of the screws (Fig 7). In addition to conventional pliers, eg, from the extraction kit, individual instruments can also be used. Powerful dentists pliers are suitable for this purpose.
  • If this fails to achieve the desired result, the screw shafts must be bored out using a hollow reamer. The inside diameter should be the same as the outside diameter of the screw. Next the hollow extraction bolt (left threaded) should be rotated in an anticlockwise direction. The shaft of the screw must be removed using a left-hand thread extractor pin (Fig 8).

Algorithm

It is very important to apply an orderly forward strategy and to keep to the algorithm. The instruments must be readily at hand.

  • Fully expose and clean the hexagon socket or Stardrive.
  • Right from the outset, use the best screwdriver.
  • If the socket head has been enlarged, immediately select the appropriate tapered left-hand thread extraction screw.
  • If this fails to achieve the desired result, or if the extractor screw or threaded rivet breaks off, immediately begin drilling out, using carbide drill bits and the drill suction device.

If these steps are followed, removing a locked or enlarged screw should not pose any problems from either a technical or time point of view.

Hazards and labeling

Due to varying countries’ legal and regulatory approval requirements, consult the appropriate local product labeling for approved intended use of the products described on this website. All devices on this website are approved by the AO Technical Commission. For logistical reasons, these devices may not be available in all countries worldwide at the date of publication. 


Legal restrictions

This work was produced by AO Foundation, Switzerland. All rights reserved by AO Foundation. This publication, including all parts thereof, is legally protected by copyright.

Any use, exploitation or commercialization outside the narrow limits set forth by copyright legislation and the restrictions on use laid out below, without the publisher‘s consent, is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, scanning or duplication of any kind, translation, preparation of microfilms, electronic data processing, and storage such as making this publication available on Intranet or Internet.

Some of the products, names, instruments, treatments, logos, designs, etc referred to in this publication are also protected by patents, trademarks or by other intellectual property protection laws (eg, “AO” and the AO logo are subject to trademark applications/registrations) even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name, instrument, etc without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain.

Restrictions on use: The rightful owner of an authorized copy of this work may use it for educational and research purposes only. Single images or illustrations may be copied for research or educational purposes only. The images or illustrations may not be altered in any way and need to carry the following statement of origin “Copyright by AO Foundation, Switzerland”.

Check www.aofoundation.org/disclaimer for more information.

 

If you have any comments or questions on the articles or the new devices, please do not hesitate to contact us


"approved by AO Technical Commission" and "approved by AO Foundation"

The brands and labels "approved by AO Technical Commission" and "approved by AO Foundation", particularly "AO" and the AO logo, are AO Foundation's intellectual property and subject to trademark applications and registrations, respectively. The use of these brands and labels is regulated by licensing agreements between AO Foundation and the producers of innovation products obliged to use such labels to declare the products as AO Technical Commission or AO Foundation approved solutions. Any unauthorized or inadequate use of these trademarks may be subject to legal action.

2020 IM covers

AO TC Innovations Magazine

Find all previous issues of the AO TC Innovations Magazine for download here.

Meet the Experts

Directly learn about AO Approved Solutions from the Experts themselves.

Innovation Awards

Innovation awards

Recognizing and fostering excellence in surgical innovation.

X
Cookies help us improve your website experience.
By using our website, you agree to our use of cookies.
Confirm