Abstract
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Compared to other techniques, poller screws with intramedullary nailing are technically simple, practical, and reproducible for the fixation of metaphyseal fractures.
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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.
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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.
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In 1999, Krettek et al. first coined the term poller screws after the small metal bollards that block and direct traffic.
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Poller screws were introduced as an adjunct to aid the union of metaphyseal long bone fractures during intramedullary nailing.
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However, as more evidence was published, the true effectiveness of poller screws was not appreciated, leading to split opinions.
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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.
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Currently, there is a paucity of research focussing on poller screws.
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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.
Introduction
Poller screws were named as a reference to ‘poller’, a term describing small metal bollards that block and direct traffic (1). Poller screws are a recently developed adjunct for intramedullary (IM) nailing of long bones and the term was first coined in 1999 by Krettek et al. (1). Proper positioning of poller screws aims to form a corridor for the IM nail to functionally reduce the width of the medullary cavity, neutralise shearing forces and increase compression forces to promote union of fractures (2, 3). The current literature describes poller screws as mainly used in acute fractures, non-unions or deformity correction of lower limb long bones, mainly tibia and femur (4, 5, 6, 7). During the 21st century, the development of poller screws has been dramatically accelerated. Here, we classified poller screw-based techniques in the existing literature into three generations; and in light of the recent advancements from our group, we propose a fourth generation of poller screws (Fig. 1) (1, 5, 7, 8). With such an exponential increase in published literature, confusion is inevitable. Therefore, appreciating the origin of our knowledge becomes all the more critical. In doing so, the direction of future research may become clearer. To our knowledge, this is the first historical review that delves into the history of poller screws to better understand its origins and explore how past research has contributed to our current understanding of poller screws. In addition, we explore our novel technique and the principle of fourth-generation poller screws through a case report.
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.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0183
Aims of this review
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To elucidate the origins of pollen screws and uncover early literature on the topic.
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To describe the most important published works on poller screws and how these have altered with time. Although our process was rigorous, it is possible that there is missing literature on the topic.
Search strategy and criteria
A non-systematic search of PubMed was performed to find early use of poller screws. Keywords such as ‘poller screw’ and ‘blocking screw’ were initially used to discover papers and reviews, mainly from the late 20th century. Referenced papers from these primary studies were duly followed up, including those not available on PubMed.
Twentieth century: early development of poller screws
Intramedullary fixation has been present since the 19th century (Fig. 2). In 1886, Bircher reported the use of ivory pegs for intramedullary fixation (9). In 1918, Hey Groves published a notorious article discussing the use of IM nailing with a metallic rod (10). Despite the adverse outcomes, he speculated on the foundations of what is considered one of the most widely accepted techniques in orthopaedic surgery. Gerhard Küntscher popularised the IM nail to fix femoral fractures in 1939 (11). The IM nail was widely accepted; however, as evidence accumulated, difficulties and limitations of this method became apparent as IM nails struggled to tackle metaphyseal fractures. Twenty years later, Modny and Bambara introduced locked IM nails to control length and rotation, especially in mid-diaphyseal fractures (12). Despite this, there were still concerns regarding the use of IM nails in metaphyseal fractures. IM nailing is the preferred surgical management of diaphyseal fractures of lower limb long bones. It can be used for metaphyseal fractures, but this is part of an extensive armoury of treatment methods. A study conducted during the late 1900s investigated whether proximal third tibial shaft fractures should be treated with IM nails with no mention of poller/blocking screws (13). Lang et al. reported unfavourable outcomes (6% never achieved union, 41% required further operations to achieve union (including additional procedures such as exchange nailing and bone graft) and 84% of their cohort had an angulation of 5° or more) (13). As a result, and therefore prior to poller screws, IM nailing was not recommended for metaphyseal long bone fractures, and surgeons considered alternatives such as plating or external fixation (13).
Timeline of early development of poller screws. *Only mention of Tscherne was a letter to editor from Seligson (21).
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0183
IM nailing of metaphyseal fractures has inherent limitations such as long lever arm, metaphyseal enlargement and epiphyseal–metaphyseal fixation difficulties, leading to a troublesome control of the angulation of the smaller bone fragment (14, 15, 16). These inherent problems are due to a mismatch between the nail's diameter and the intramedullary canal's diameter (1). There is no discrepancy at the isthmus level, but outside the isthmic area, the discrepancy is significant. The fracture tends to displace in the direction of stronger muscle pull, and the IM nail will not be able to compensate for this pull due to the difference in diameter in the metaphysis. Common problems associated with IM nailing metaphyseal fractures include malalignment, malunion and pain (14, 15, 16).
During the late 20th century, orthopaedic surgeons did not want to abandon IM nails. IM nails offer many biomechanical and biological advantages, and surgeons proposed adjuncts to supplement the IM nailing technique. These adjuncts included unicortical plate, percutaneous reduction using a point reduction clamp and modifications to the IM nail design (Herzog’s curve) (17, 18, 19). In 1983, Donald and Seligson proposed ‘blocking screws’ as an alternative to these adjuncts to improve fracture reduction; however, this was not clear, and they seemed to be referring to a locking screw across the intramedullary nail (20). Dr Tscherne later introduced the idea of screws placed on either side of the IM nail to further guide the IM nail (21). In 1999, Krettek et al. further elaborated on ‘blocking screws’ and introduced ‘poller screws’ to clinical practice. These are adjacent percutaneous screws placed to guide the IM nail within the medullary canal, thus reducing the metaphyseal fracture without approaching the fracture site (1).
In that study, 31 poller screws were utilised on 21 fractures in 20 patients: 13 patients with a single poller, 6x patients with two poller screws and 2 patients with three poller screws (1). The majority of poller screws were 3.5 mm cortical; however, 4.5 mm cortical or 6.5 mm cancellous screws were also used (1). Fractures with a single poller screw had the blocking screw placed on the concave side of the deformity, as the guide wire and IM nail gravitated towards the concave side of the fracture (1). Krettek et al. reported no complications related to poller screws (1). In comparison to Lang et al., Krettek et al. reported more favourable outcomes (all fractures were united with an average healing time of 5.4 months, and no patients underwent further surgeries) (1, 13). However, one patient developed a rotational malalignment greater than 15° (1). Nevertheless, 56% of their cohort was rated excellent or good on Karlström-Olerud score (KO score), and the KO score was not affected by pre-existing or concomitant injuries (1). Krettek et al. combatted the aforementioned limitations of IM nails in metaphyseal fractures by using poller screws to functionally decrease the width of the medullary cavity and physically block the IM nail to aid in reducing the fracture, resist the muscular displacement in the mobile distal fragment and improve the stiffness of the bone–implant construct (1). Prior to Krettek et al. 1999, the idea of poller screws had been previously described in his previous studies (22). Even though the study was pertaining to poller screws in tibial fractures, the same technique has been utilised for the femur by the same surgeon (23).
Early 21st century: evolution of poller screws (first generation to fourth generation)
First generation
The use of poller screws has evolved over the past 20 years. First-generation poller screws were inserted to create a corridor inside the cortex as described by Krettek et al. (1). In a cadaveric study of a metaphyseal tibia fracture model stabilised with unreamed nails, Krettek et al. reported that the addition of two anteroposterior blocking screws decreased the deformation of the bone–implant construct by 57% in the distal fragment and 25% in the proximal fragment compared to a construct with no blocking screws (24). Furthermore, poller screws can improve fixation. When inserting IM nails, the reamer is typically set to 1–2 mm greater than the final diameter of the IM nail. Regardless of the diameter of the nail, there will always be space between the IM nail and cortex. Poller screws effectively reduce the width of the intramedullary canal, aiding the mechanical stiffness of the bone–implant construct and further resisting biomechanical muscular forces (1). Following this, in a study by Ricci et al., 12 consecutive proximal tibia fractures were treated with IM nailing with a poller screw adjunct (25). Poller screws were inserted prior to reaming (25). All poller screw patients had an angular deformity of fewer than 5° (25). However, only one patient who did not have a poller screw had a valgus deformity from 6° to 10° (25). These results compared favourably to other modifications of IM nailing at that time (26, 27). These studies contributed to the acceptance of the use of poller screws as adjuncts in metaphyseal fractures of the tibia (1, 25). Overall, first-generation poller screws were used as a reduction tool guiding IM nails and facilitating more accurate fracture reduction.
Second generation
Spiral fractures and highly oblique fractures are predisposed to natural rotational propensity leading to excessive shearing forces (7, 28). Second-generation poller screws are placed on one side of the fracture only and are used to further stabilise spiral fractures, prevent rotational impulsivity and reduce the shearing forces while promoting healing. As with all fractures, precise reduction and maintenance of reduction are thought to reduce pain and optimise fracture healing in a functional position (7). A biomechanical model devised by Stedtfeld et al. demonstrated the effect of second-generation poller screws (29). Stedtfeld et al. demonstrated that fracture reduction could be achieved with one poller screw on the concave aspect of the short fragment to form a third point of Charnley’s 3-point fixation (1, 29, 30). The screw supplies the third point, with the other two being the diaphysis of the long bone and either the anchorage point at the tip of the nail or the entry point (30). In situations where the nail has insufficient anchorage or entry point of the nail is too large, Stedfeld et al. recommended a second poller screw on the convex aspect of the long fragment away from the fracture (29). This will help overcome the muscular and ligamentous displacement forces that cause the displacement (29).
In 2010, a case report introduced the use of a Steinman pin while applying the Stedtfeld principle of poller screws (31). Shahulhaemeed et al. inserted a Steinman pin into the small fragment on the concave side 1 cm away from the fracture line and 6–7 mm from the centre of the medullary canal, describing a placement according to second-generation poller screw principles. Kocher clamp was used to hold the Steinman pin in place to prevent it from spinning during reaming. Once the IM nail is secured through distal and proximal locking, the Steinman pin is removed and replaced with a 5 mm interlocking poller screw. The advantages of using a Steinman pin include easy removal if the location of the pin is not satisfactory, along with minimal damage to the reamer and nail due to the smooth nature of the Steinman pin. 3.9 mm Steinman pins are ideal for 5 mm locking poller screws, and since the poller screw is inserted at the latter stages of the procedure, the risks of breaking or bending screws are reduced. However, second-generation poller screws rely on the elastic nature of IM nails to deflect around the poller screws to allow for long-term compression. Given the Steinman pin is removed and replaced with a poller screw after the insertion of the IM nail, the elastic energy created by the pin and nail construct will be dissolved and theoretically will no longer lead to long-term compression of the fracture to allow for the reduction to improve over time.
A series of retrospective cohort studies by Seyhan et al. investigated the effectiveness of second-generation poller screws (32, 33, 34). One case series used a single poller screw to tackle troublesome tibial metaphyseal and diaphyseal fractures with inadequate reduction with the IM nail only (34). There was no significant difference in the reduction on the radiograph taken immediately after the procedure and 1 year after. Based upon their 95% union, the authors suggested the use of poller screws when adequate reduction could not be achieved with IM nails only (34). A follow-up study from the same authors assessed the effect of second-generation poller screws in the femur (33) where there was a 100% union rate with a mean time to union of 12.6 weeks (8–32 weeks range) (33). Accordingly, the authors recommended that poller screws are placed 1–3 cm away from the fracture site to balance further comminution of bone with reducing shearing forces of fragments under biomechanical stress (33). Based upon the principle of Mohr’s circle, the maximum shear stress will act 45° from the principal stresses, and hence why the vast majority of fracture extensions are under 45° from the fracture site (35). Poller screws as an adjunct to IM nails can help combat the excessive shear stresses seen when using IM nails alone to tackle long bone metaphyseal fractures. Seyhan et al. demonstrated highly favourable results, enabling more frequent and confident use of IM nailing in distal fractures in the lower limb (33, 34).
Other reduction adjuncts have been used, such as percutaneous clamping, cerclage cables and temporary or permanent single cortex plating (32, 34). Seyhan et al. found that poller screw use in subtrochanteric femoral fractures resulted in a significantly shorter time to full weight-bearing, along with a higher Harries hip score after 1 year of follow-up when compared to cerclage cables and percutaneous reduction clamps, while there was no significant difference between the patient characteristics between the cohorts (32). However, it was noted that there was no statistically significant difference in time to union despite the poller screw cohort achieving union 6 weeks faster than the clamp reduction cohort (32). At that point in time, poller screws were beginning to gain traction as it was becoming clear that poller screws combatted the weaknesses of IM nails when tackling metaphyseal long bone fractures while still exhibiting IM nail’s biomechanical benefits.
In a biomechanical study, Chan et al. compared three metaphyseal tibia fracture constructs fixed with IM nails: group one with IM nails with two locking bolts distally, group two with two locking bolts and a medial poller screw, and group three with three locking bolts distally (36). Although there was no permanent deformation in any groups, it was found that the addition of a medial blocking screw did not result in a statistically significant difference in stability compared to locking bolt-only constructs (36). However, the biomechanical model does not consider the progressive healing of the fracture, which will inevitably contribute to fracture stability further (36). During this period, we began to understand second-generation poller screws further. We now know that the elastic energy of IM nails built under the tension of poller screws contributes to long-term compression and improvement in fracture reduction over time (3). Accordingly, a 10 mm IM tibial nail will not be able to harness the full benefit of poller screws. The deflection of the IM nail as it passes the poller screw is essential in generating further stability (3).
In a retrospective cohort study, Van Dyke et al. investigated the effects of poller screws on infraisthmal femoral fractures managed with retrograde IM nailing (37). Although poller screw constructs showed a trend towards more favourable time to union and union rates, neither was significant (37). Similar results were found by Hamahashi et al. (38). However, as noted by Van Dyke et al., their study was not sufficiently powered, and Hamahashi et al. only had ten patients, which would not be sufficient either (37, 38). However, a similar cohort study by Song in 2019 found that the union rate in the poller screw cohort was significantly higher than in the non-poller construct (39). Despite the time to union being more favourable in the poller construct, it was still not statistically significant (39). Due to the novelty of poller screws, current existing reports in the literature are predominantly retrospective with small cohorts and are in many cases underpowered, hence unable to conclude causation (37, 38, 39). Well-designed randomised controlled trials (RCT) comparing poller screw construct to non-poller screw construct are required to provide a more reliable understanding of the poller screw’s effectiveness.
As more evidence accumulated, there was increased confusion regarding the positioning of poller screws. Many studies have recommended the placement of poller screws on the concave aspect of the short fragment (1). Another study anecdotally mentioned positioning the poller screw ‘where you don’t want the nail to go’, a common notion regarding poller screws (5). Hannah et al. described a simple and reproducible method for ensuring correct placement of poller screws to maximise the biomechanical advantages (5) (Fig. 3). Poller screws are rarely required in both fragments as only the short fragment, considered to be a mobile fragment, requires the additional stabilisation provided by a poller screw (5).
Hannah et al. (5) method of positioning of poller screws.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0183
A retrospective analysis compared those without poller screws to poller screws, using the Hannah et al. method of screw placement, to assess the effect of poller screws on fracture stability (8). There was significantly increased stability in the poller screw cohort compared to the control (8). This was evidenced by the significantly decreased excess callus formation around the fracture, suggesting second-generation poller screws provide a more optimal environment for bone healing (reduced shearing and increased compression forces) (8). Second-generation poller screws utilise the elastic properties of IM nails to generate long-term compression and reduction in shearing forces to provide the optimal environment for fracture union.
However, a short letter from Ozmeric and Alemdaroglu suggested an alternative to Hannah et al., where they initially determined the direction they want the flared segment to move, before drawing and placing the poller screw on the same side as the direction of movement (opposite to the direction of displacement) (40) (Fig. 4). To our knowledge, both principles are utilised during the pre-operative planning for poller screws (5, 40).
Özmeriç & Alemdaroğlu (40) methods positioning of poller screws.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0183
Screws placed away from the desired location will not function as a poller screws and may cause damage to the reamers and the nail (31). There is also a risk of screw bending, breakage, and difficulty in removal (31). In order to identify the exact locations to place poller screws, a careful analysis of the preoperative and intra-operative imaging with traction is essential.
Third generation
Correct placement of second-generation poller screws altered the shearing and compressive forces across the fracture site. Third-generation poller screws can be considered as second-generation poller screws but applied to both sides of the fracture site. Here, we discuss the operative technique and biomechanical principles that led to the development of third-generation poller screws.
Reverse rule of thumb
With the growing recognition and confusion regarding the correct placement of poller screws, surgeons devised an alternative way to think about the positioning of poller screws. A principle proposed by Muthusamy et al., the ‘reverse rule of thumb’ has been used for limb lengthening and deformity correction surgery (6) (Fig. 5). This was one of the first studies to describe the equidistant placement of poller screws on both the proximal and distal aspects of the fracture site. Although this was devised for limb lengthening and deformity correction, we believe this principle can be applied to acute fractures and non-unions as well.
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.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0183
If the IM nail is not centred in the medullary canal, then a poller screw utilising the reverse rule of thumb can be inserted to centre the IM nail (6). If both ends of the IM nail are not adequately centred, then two poller screws are applied using the reverse rule of thumb technique: one screw for each end of the bone fragment. Muthusamy et al. suggested that the use of two poller screws on one bone fragment can increase stabilisation of the bone-fixation construct. One screw is inserted close to the osteotomy/fracture site, and the second screw away from the osteotomy/fracture site of the bone (6). Not all screw positions need to be used and are instead utilised only as needed, depending on whether one or both ends of each bone fragment are deformed. This principle typically results in the insertion of four poller screws: that is, two screws on either side and equidistant from the fracture site. The study found that despite the accurate placement of poller screws, distal femoral osteotomies less than 10 cm away from the knee joint were still challenging. The authors suggested a posterior poller screw will improve the final alignment. This study alluded to the principle of fourth-generation poller screws.
Epicentricity
Conventionally, poller screws are placed in the shorter and more mobile fragment on the concave aspect of the fracture to achieve the reduction of the fracture (29). In this retrospective cohort study, poller screws were placed as close as possible to the fracture site whilst avoiding further comminution around the fracture. Smaller IM nails were used (8 mm) as the smaller diameter allowed the IM nail to deflect around the screw to stabilise the reduction for healing (7). Furthermore, the elastic property of the IM nail generates long-term compression of the fracture and allows the reduction to improve over time (second-generation poller screws). However, in epicentric poller screws, at least two poller screws are placed (7). The additional poller screws are placed equidistant from the fracture line to the first screws, but on the opposing side of the IM nail (7). The epicentricity principle describes a novel technique of inserting two poller screws equidistant across the fracture site to minimise shearing forces and generate inter-fragmentary compression (Fig. 6). Peat et al. retrospectively compared three groups of patients; group one: IM nail alone, group two: IM nail and one conventional poller screw or group three: IM nail and two poller screws placed epicentrically across the fracture site (7). There was a statistically significant difference (P = 0.05) in fracture union between the three groups, with 75/88 fractures healing in group one compared to 44/46 in group two and 20/20 in group three, demonstrating an improvement of fracture union from IM nailing-only to third-generation poller screws. Although poller screws are also correlated with shorter operation to discharge times, it is recognised that the placement of a blocking screw will increase the surgical procedure time and the amount of the radiation exposure for the patient (7, 41).
The biomechanical principles of epicentricity are based upon moments. As coronal poller screws are equidistant from the fracture site, the range of circular motion from both fragments will align under muscular and biomechanical stress. However, if the poller screws are no longer equidistant from the fracture site, the fragment with the greater distance from the poller screw will exhibit a larger range of circular motion under stress. While to an extent motion between the two fragments can benefit fracture union (42), it is widely regarded that shearing forces across a fracture site are unfavourable as they disrupt the periosteal vascularisation and impair fracture healing (43). The unequal nature of the circular motion between the two fragments will generate higher shearing forces and reduce compression. In order to further reduce these shearing forces, epicentric poller screws should be kept as close as possible to the fracture site without causing further comminution. This will further reduce shearing and convert these forces into compression under biomechanical stress (Fig. 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.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0183
Fourth generation
We present our novel technique at our institution through this case report. Our group, led by XXBLINDEDXX, has further advanced the use of poller screws by applying the principle of epicentricity with sagittal and coronal alignment using four poller screws. Additional coronal and sagittal stability while applying the principle of epicentricity will further reduce the shearing forces, improve compressional forces, and promote healing. To our knowledge, this idea of fourth-generation poller screws has yet to be described within the current literature, and we present to you our understanding and technique regarding the use of poller screws in long bone fractures.
Surgical technique of fourth-generation poller screws, including our current understanding and tips for the successful insertion of fourth-generation poller screws
Pre-operative planning is essential to determine the deforming forces acting on the fractures and to locate the optimal placement of poller screws. Patients were positioned supine on a radiolucent operating table with a pneumatic tourniquet placed around the thigh. Surgical approaches were used at the discretion of the operating surgeon. The decision to use and the positioning of poller screws were down to the operating consultant surgeon. In general, senior surgeons at our institution advise using poller screws in spiral/highly oblique fractures with two core fragments at the fracture site to allow for reduction and compression and a satisfactory intramedullary canal to accommodate an IM nail with poller screws. Conventional placement of poller screws in keeping with previously published principles was used in the shorter, displaced mobile fragment to achieve reduction (29). One poller screw was placed anterior–posterior (for coronal control), and another was placed medial–lateral (for sagittal control), and those poller screws were placed as close to the fracture line as possible without causing further comminution.
We advise keeping poller screws as close to the fracture site as possible to reduce fracture movement and improve the fracture's stability while avoiding comminution and further bone breakage. The corresponding poller screws were placed equidistant, applying the principles of epicentricity, and on the opposing aspect of the nail in the other fracture segment (3, 7). A total of four poller screws are used in fourth-generation poller screws (two in the coronal plane and two in the sagittal plane). Once poller screws are positioned correctly, a curved olive tip guidewire will govern the direction of the reamer to create a passage for the IM nail. Typically, we recommend using 9 mm for femoral nails with 5 mm interlocking poller screws and 8 mm tibial nails with 4 mm interlocking poller screws. Using thinner nails will allow for deformation of the IM nail as it deflects past the poller screws and will generate reduction and compression forces due to its resistance to bending (Young’s modulus of elasticity). We use the working distance and position of the fracture to decide whether the placement of poller screws or insertion of the IM nail/reamer comes first. The working distance is defined as the distance of the IM nail to the fracture site. For shorter working distances, we insert the reamer first to act as a jig for placing the shorter fragment poller screws in metaphyseal fractures. This applies for both antegrade and retrograde nailing as the broader aspect of the IM nail will be less elastic and less likely to deflect; hence the position of the poller screws in the short fragment will become all the more critical. This method guarantees that the largest reamer will fit through the passage created by the positioning of poller screws in the shorter fragment. However, we percutaneously insert the poller screws first for diaphyseal fractures as the middle third of the nail will be able to deflect past the poller screws. All patients underwent reamed nailing, with the nails locked proximally and distally following satisfactory insertion.
Case report: proximal femoral non-union
A 59-year-old gentleman presented to the clinic with an unstable, painful non-union of the right proximal femur with rotational malalignment; previously treated with a femoral plate (Fig. 8). Clinical examination confirmed 20° of excessive external rotation and was confirmed with a CT scan. Furthermore, radiographs and CT scans confirmed that one of the distal screws was broken. Antegrade/retrograde femoral nailing was performed with the patient supine on a radiolucent operation table. A 2 cm incision was made through an existing scar from previous surgery to remove the existing nail and insert the new 9 mm nail, and smaller 1 cm incisions were made for the percutaneous insertion of four poller screws. Existing metalwork from the previous surgery was removed, including the broken distal screw. Microbiology samples were taken as per our protocol. Four poller screws were inserted epicentrically and close to the non-union under C-arm radiography; two poller screws were inserted anterior–posterior and two poller screws medial–lateral. A bent olive tip guidewire was inserted through the passage created by poller screws, followed by an 8.5 mm, a 9.0 mm and a 9.5 mm reamer consecutively. A 9 mm femoral nail was used for its elastic nature to provide long-term compression of the non-union. Thinner IM nails deflect past the poller screw and will generate more compression than thicker rigid IM nails due to the deflection. The IM nail was locked proximally and distally when the final position was confirmed on C-arm radiography (Fig. 8). The rotational profile of the non-union was corrected and confirmed with radiography. Standard wound closure was performed.
C-arm radiographs of IM fixation of a proximal femoral non-union with fourth-generation poller screws.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0183
Although full weight-bearing was advised immediately post surgery, the patient was initially hesitant to be fully weight-bearing as he was worried the metalwork would break. Although this will likely hinder the recovery process, the patient recovered swiftly as he was cycling after 12 weeks, running uphill after 1 year and skiing after 2 years. Initially, the patient was walking with a minimal limp with one crutch; however, 8 months later, the patient was fully weight-bearing. Despite fully weight-bearing and running up hills, we were not convinced the radiographs showed complete union after 1 year (Fig. 9). Nevertheless, it was most definitely moving in the right direction with minimal callus formation. Three years post operation, radiographs confirmed union; although, it is likely union was achieved between the last two appointments.
Three year follow-up of AP and lateral radiographs for fourth-generation poller screws.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0183
Strengths and limitations
We used a wide range of historical studies from the twentieth century onwards. However, as many of the studies were not available on online databases and were only available as hard copy, we had to reference-search to find older papers. Although our process was rigorous, it is possible that there is missing literature on the topic.
Conclusion
Poller screws promote a stable mechanical environment for the healing of acute fractures, non-unions and deformity and corrective osteotomies if used correctly. Krettek et al. in 1999 first coined the term poller screws and popularised them; this became the foundation of our current understanding (1, 22, 23, 24). As more research has been published, however, the philosophies regarding poller screws are less clear and there are now disagreements on the effectiveness, positioning and use of poller screws. In the midst of this, it is difficult to conclude the true gold standard regarding poller screws. In this review, we summarised the various generations of poller screws, and classifying the use of poller screws will help surgeons to have a more in-depth understanding of poller screws. With such an exponential increase in published literature, confusion such as this is inevitable. Appreciating the origin of our knowledge, not just in terms of its operative technique as outlined in this review but also the biomechanics behind poller screws, is critical. Through following the research on poller screws over the years, we have accumulated knowledge regarding this topic, and we present how we came to the idea of our novel technique and what we believe to be the fourth generation of poller screws.
Key messages
This is the first study, to our knowledge, to give a comprehensive review of the historic literature regarding poller screws.
We found that although evidence of poller screws has existed in the literature for decades, our understanding of it has been heavily influenced by Krettek et al.’s initial paper (1) in 1999.
When challenging old data on poller screws, it is important to appreciate the historical context surrounding them.
ICMJE Conflict of Interest Statement
The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding Statement
This work did not receive any specific grant from any funding agency in the public, commercial, or not-for-profit sector.
Author contribution statement
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by AZ, EJ, JZ, VL and SM. The first draft of the manuscript was written by AZ and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
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