The use of 'blocking' screws for the 'closed' reduction of difficult proximal and distal femoral fractures

The evolution of poller screws

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.

Biomechanical comparison of distal femoral fracture fixation: Polyaxial vs. uniaxial locking screws with different blocking screw configurations in retrograde femoral nailing

INTRODUCTION

Clinical studies have indicated reduced reliance on blocking screws with the introduction of polyaxial locking nails, yet the biomechanical superiority of polyaxial locking over blocking screws remains unverified, specifically for distal dia-metaphyseal femur fractures.

HYPOTHESIS

We hypothesized that the combination of multiaxial locking using three screws and parallel locking reinforced by two blocking screws would result in superior outcomes compared to utilizing only parallel locking with two screws and one blocking screw.

MATERIALS AND METHODS

Third-generation custom-made femur models representing AO/OTA 32 A1.2 dia-metaphyseal comminuted oblique fractures were divided into four groups (n=10/group). Group A employed distal fixation with three 4.5-mm polyaxial screws. Group B used two parallel locking screws and two blocking screws, Group C used two parallel locking screws and one blocking screw, and Group D used only two parallel screws. Specimens underwent axial and torsional load testing to assess fatigue strength, ultimate strength, axial stiffness (N/mm), torsional stiffness (N/mm/deg), axial load to failure (N), torsional load to failure (N/mm), coronal and sagittal angulations, and fracture site collapse.

RESULTS

Group C exhibited statistically superior torsional stiffness compared to Groups B and D (p=0.039 and p=0.034, respectively). Axial load to failure was highest in Group B and lowest in Group D (p=0.032). Group C demonstrated the highest torsional strength, while Group B exhibited the lowest (p=0.006). Coronal displacement was greatest in Group B, while Group A showed the highest resistance (p=0.009). Group A demonstrated the greatest resistance to fracture site collapse, with the weakest specimens observed in Groups B and C (p=0.01).

DISCUSSION

The performance of a single laterally positioned blocking screw is comparable to using two blocking screws. Medial positioning of a second blocking screw is unnecessary for stability enhancement. Multiaxial locking prevents fracture site collapse and coronal plane angulation more effectively than other methods. Multiaxial locking and/or parallel screws with a single laterally positioned blocking screw provide superior stiffness and stability for treating unstable dia-metaphyseal distal femoral fractures.

LEVEL OF EVIDENCE

N/A.

Imaging Evaluation of Insertion Point Accuracy in Retrograde Intramedullary Femoral Nailing

Objective

When compared with visual retrograde intramedullary nail placement in the femur, fluoroscopic retrograde intramedullary nail placement in the femur improved the accuracy of insertion.

Methods

Ninety-six patients treated with retrograde intramedullary nailing of the femur for femoral fracture were included in this retrospective case-control study, including 48 patients treated with nailing under direct vision and 48 patients treated with nailing under fluoroscopy. Influencing factors potentially associated with the deviation of the needle insertion point on the coronal and sagittal planes (including the needle insertion method, use of limited open reduction, side, intramedullary nail diameter, mechanism of injury, and fracture classification) were analyzed univariately; then, the variables with a p value < 0.20 on univariate analysis were included in the linear regression equation to assess the independent factors associated with needle insertion point deviation.

Results

On the coronal plane, the insertion point deviation in the visual nail placement group (1.11 ± 4.08 mm) was not significantly different (p = 0.13) from that in the fluoroscopic nail placement group (−0.44 ± 3.48 mm); on the sagittal plane, the insertion point deviation in the visual nail placement group (4.91 ± 4.67 mm) was significantly greater than that in the fluoroscopic nail placement group (2.08 ± 2.97 mm) (p < 0.01). Visual nail placement was a risk factor for insertion point deviation on the sagittal plane compared with fluoroscopic nail placement (β = −0.84, p < 0.01).

Conclusion

Compared with visual nail placement, fluoroscopic nail placement improves the accuracy of insertion on the sagittal plane, with no difference between the two methods on the coronal plane. These findings indicate that surgeons should exercise more caution when placing nails under direct vision.