The evolution of poller screws

Abstract

Compared to other techniques, poller screws with intramedullary nailing are technically simple, practical, and reproducible for the fixation of metaphyseal fractures. In addition, poller screws do not require special instruments or hardware and are minimally invasive. This review takes a historical perspective to evaluate poller screws holistically. A non-systematic search on PubMed was performed using 'Poller screw' or 'Blocking screw' to find early use of poller blocking screws. Relevant references from these primary studies were then followed up. In 1999, Krettek et al. first coined the term poller screws after the small metal bollards that block and direct traffic. Poller screws were introduced as an adjunct to aid the union of metaphyseal long bone fractures during intramedullary nailing. However, as more evidence was published, the true effectiveness of poller screws was not appreciated, leading to split opinions. Through our research, we have built upon our understanding of poller screws, and we present a novel classification of poller screws over the years while exploring our novel technique and what we believe to be the fourth generation of poller screws. Currently, there is a paucity of research focussing on poller screws. However, studying the original evidence regarding poller screws through the most recent articles has demonstrated a confusion of research in this field. Therefore, we suggest a more organised approach to classify the use of poller screws.

Keywords: intramedullary nails; poller screw.

Figure 1

Summary of poller screw generations: first generation: Poller screws inserted to create a ‘corridor’ inside the bone. Second generation: Poller screws are inserted to reduce and compress the fracture by allowing the IM nail to defect and consequentially providing long-term compression of the fracture. Second-generation poller screws were placed on one side of the fracture only, and the elasticity of the nail would commonly allow for the reduction to improve over time. Third generation: Placement of second-generation poller screws but both sides of the fracture including the reverse rule of thumb and principle of epicentricity. Fourth generation: Poller screws are placed on both sides of the fracture, like the third generation. In the fourth generation, two poller screws are placed in the anterior–posterior and medial–lateral planes to stabilise the coronal and sagittal planes. Four poller screws are used in total, and a ‘tunnel’ is formed to guide the IM nail through the medullary cavity tactically. White circles signify poller screws, and the red line signifies the IM nail.

Figure 2

Timeline of early development of poller screws. *Only mention of Tscherne was a letter to editor from Seligson (21).

Figure 3

Hannah et al. (5) method of positioning of poller screws.

Figure 4

Özmeriç & Alemdaroğlu (40) methods positioning of poller screws.

Figure 5

Muthusamy et al. (6) Reverse rule of thumb. This technique involves three steps: 1. Understand the direction of the deformity that will be corrected. 2. Envision manually correcting the deformity by holding the bone with both thumbs and the index finger on either side of the osteotomy line. Thumbs of both hands are placed on the convex side near the osteotomy line, and the index fingers are placed away from the osteotomy line on the concave aspect. 3. Poller screws should be placed on the opposite side of the nail where the thumbs and index fingers are on the bone. We have applied this principle to acute fractures as well. We present the reverse rule of thumb on a femoral non-union with a varus deformity. White arrows signify the force generated from the thumbs. Red arrows signify the force generated from the index fingers.

Figure 6

Epicentric poller screws.

Figure 7

Images demonstrating the biomechanical benefit of epicentric poller screws kept close to the fracture site. In addition, showcasing a reduction with and without poller screws.

Figure 8

C-arm radiographs of IM fixation of a proximal femoral non-union with fourth-generation poller screws.

Figure 9

Three year follow-up of AP and lateral radiographs for fourth-generation poller screws.