Poller or blocking screw

Poller or Blocking Screw

1. POLLER OR BLOCKING
SCREW
Dr.Avik Sarkar
KB Bhabha Municipal General Hospital

2. Terminology
The concept of Poller
screw was first
popularized by Krettek
et al in 1999. They
called the screws “poller
screws” because the
screws guided the nail
like the “poller”
(retractable bollard)
traffic control devices
guide traffic in Europe.

3. Uses
•They are used as blocking screws
in stabilising tibial and femoral fractures treated with
small diameter intramedullary nails [1]
•The medial and lateral blocking screws can increase the
primary stability of distal and proximal metaphyseal
fractures after nailing [2]
•Manage malunited fractures during revision [3]
1. Krettek C, Stepha C, Schandelmaier P, Richter M, Pape HC, Miclau T. The use of Poller screws as blocking screws in stabilising
tibial fractures treated with small diameter intramedullary nails. J Bone Joint Surg Br. 1999;81:963–8.
2. Krettek C, Miclau T, Schandekmaier P, Stephan C, Mohlmann U, Tscherne H. The mechanical effect of blocking screws (‘Poller
screws’) in stabilising tibia fractures with short proximal or distal fragments after the insertion of small diameter
intramedullary nails. J Orthop Trauma. 1999;13:550–3.
3. L Dodd, M Jackson, and R Varma. Poller Blocking Screws and Intramedullary Nailing in Tibial Malunion. Ann R Coll Surg Engl.
2007 Nov; 89(8): 816–818.

4. •The nails are typically smaller than the
intramedullary canal at proximal tibia in
metaphyseal fractures at this level causing the
segment to drift, because the nail may not
have dominant purchase on the proximal
segment. By using Blocking screws the
effective canal of the proximal metaphyseal
fragment can be narrowed to an appropriate
corridor for the nail to pass.
•By placing a blocking screw from medial to
lateral and having the nail pass anteriorly to
this screw forces the nail anteriorly in the canal
and can also prevent a sagittal plane
deformity.

5. One rule of thumb is to apply the
screws on the concave side of a
deformity [4]
4. Stedtfeld HW, Mittlmeier T, Landgraf P, Ewart A. The logic and clinical applications of blocking screws. J Bone Joint Surg
Am 2004;86:17-25.

6. Medio-lateral placement of
screws
Antero-posterior
placement of screws

7. Alternatives of Poller Screws
Schanz Screw
K-Wire
Steinman Pin

8. Preparation
•Screw placement must be as close to the
fracture as possible.
•Monocortical insertion is used in the proximal
fragment and Bicortical Insertion in the distal
fragment.
•A T-handle can be used for easier
manipulation.

9. Forces Acting

10. Technique for accurate Poller
Screw placement [5]
•Draw a line down the long axis of the displaced, flared segment of bone.
•Draw a second line along the plane of the fracture, ensuring to bisect
the first line.
•Identify your acute angles
5. A novel technique for accurate Poller (blocking) screw placement. Andrew Hannah

, Tariq Aboelmagd, Grace Yip, Peter Hull. Injury, Int. J. Care Injured
45 (2014) 1011–1014

11. •Place your screw in the acute angle of the metaphyseal or flared segment.
•Insert your guide wire under fluoroscopy guidance,
ensuring the tip passes the correct side to ensure reduction.
•Insert your nail, which should be deflected on engaging the screw
providing reduction and compression at the fracture site
•If reduction could be improved further by the addition of a
further screw, this should be placed in the acute angle nearer
to the isthmus.

12. The use of transmedullary blocking screws in combination
with an intramedullary nail is an important additional option
that can be used to improve reduction and fixation of long-
bone fractures at the metaphyseal-diaphyseal junction,
where there is a strong tendency for axial displacement.
The blocking screw around the nail relieves axial strain in
the fixation construct, while the interlocking screws through
the nail control length and rotation.
The transmedullary support screw provides a point of
support on the side of the nail for the short fragment in an
intramedullary three-point construct. Hence these screws
are also called transmedullary support screws.