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Review
. 2020 Jan 29;5(1):26-36.
doi: 10.1302/2058-5241.5.180066. eCollection 2020 Jan.

Surgical performance when inserting non-locking screws: a systematic review

James W A Fletcher  1   2 , Lisa Wenzel  2   3 , Verena Neumann  2 , R Geoff Richards  2 , Boyko Gueorguiev  2 , Harinderjit S Gill  4 , Ezio Preatoni  1 , Michael R Whitehouse  5   6
Affiliations
Review

Surgical performance when inserting non-locking screws: a systematic review

James W A Fletcher et al. EFORT Open Rev. .

Abstract

Billions of screws are inserted by surgeons each year, making them the most commonly inserted implant. When using non-locking screws, insertion technique is decided by the surgeon, including how much to tighten each screw. The aims of this study were to assess, through a systematic review, the screw tightness and rate of material stripping produced by surgeons and the effect of different variables related to screw insertion.Twelve studies were included, with 260 surgeons inserting a total of 2793 screws; an average of 11 screws each, although only 1510 screws have been inserted by 145 surgeons where tightness was measured - average tightness was 78±10% for cortical (n = 1079) and 80±6% for cancellous screw insertions (n = 431).An average of 26% of all inserted screws irreparably damaged and stripped screw holes, reducing the construct pullout strength. Furthermore, awareness of bone stripping is very poor, meaning that screws must be considerably overtightened before a surgeon will typically detect it.Variation between individual surgeons' ability to optimally insert screws was seen, with some surgeons stripping more than 90% of samples and others hardly any. Contradictory findings were seen for the relationship between the tightness achieved and bone density.The optimum tightness for screws remains unknown, thus subjectively chosen screw tightness, which varies greatly, remains without an established target to generate the best possible construct for any given situation. Work is needed to establish these targets, and to develop methods to accurately and repeatably achieve them. Cite this article: EFORT Open Rev 2020;5:26-36. DOI: 10.1302/2058-5241.5.180066.

Keywords: bone screws; fracture fixation; internal fixation; screw insertion; screw tightness; stripping torque; surgical technique.

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Conflict of interest statement

ICMJE Conflict of interest statement: JWAF reports a Research Fellowship with the Royal College of Surgeons of England for the submitted work. LW reports she is the Chair of the ‘Junges Forum O und U’ - the political board of young trauma and orthopaedic surgeons in Germany; research funding from Forschungsförderungsfond der Paracelsus Medizinischen Privatuniversität, PMU Rise Projekt, Kategori: Newcomerprojekt (research funding of the Paracelsus Medical Private University, Rise project in the category ‘newcomer project’), all outside the submitted work. RGR reports support for travel to meetings for the study or other purposes from AO Research Institute Davos for the submitted work. HSG reports a grant covering first author from the Royal College of Surgeons for the submitted work. The author reports consultancy to Zimmer Biomet and an educational grant from Smith & Nephew; and membership of the BJJ Editorial Board, with expenses for attending meetings reimbursed outside the submitted work. EP reports they are a co-investigator in the fellowship application of the corresponding author from David Telling Charitable Trust and Royal College of Surgeons for the submitted work. MRW reports grant salary costs from the National Institute for Health Research Bristol Biomedical Research Centre, University Hospitals Bristol NHS Foundation Trust and University of Bristol, National Joint Registry Lot 2 contract, Stryker (Triathlon); royalties for being editor of an orthopaedic textbook from Taylor & Francis; undertaking teaching on basic sciences for orthopaedic trainees preparing for the FRCS for which the author’s institution receives market-rate payment from Heraeus; undertaking teaching on total hip replacement for orthopaedic consultants and trainees for which the author’s institution receives market rate payment from DePuy, all outside the submitted work. The other authors declare no conflict of interest relevant to this work.

Figures

Fig. 1
Fig. 1
PRISMA flow chart.
Fig. 2
Fig. 2
Tightness achieved for each part within each study, where measured. From top to bottom, grouped alphabetically within the following sections: cortical screws in artificial bone (dark blue), cortical screws in human bone (dark orange), cancellous screws in artificial bone (light blue), cancellous screws in human bone (light orange). All bubbles scaled with size representing number of screws used, e.g. Acker et al 2016 – first-year = 40 screws. The different components of each study, where relevant, are explained as follows: Acker et al and Wilkofsky et al – different years of experience of surgeons; Aziz et al: A – cortical screws in fresh frozen human bone, B – cortical screws in embalmed human bone, C – cortical screws in dried human bone, D – cortical screws in normal density artificial bone, E – cortical screws in osteoporotic density artificial bone, F – cancellous screws in fresh frozen human bone, G – cancellous screws in embalmed human bone, H – cancellous screws in dried human bone; Tsuji et al artificial bone: densities for each part (cortical and cancellous screws respectively) – 0.08 g/ cm3 (A and I), 0.16 g/cm3 (B and J), 0.24 g/cm3 (C and K), 0.32 g/ cm3 (D and L), 0.40 g/ cm3 (E and M), 0.48 g/ cm3 (F and N), 0.64 g/cm3 (G and O), 0.80 g/cm3 (H, cortical only); Tsuji et al, human bone: P – cortical screws, Q – cancellous screws; Cordey et al, 1a – 4.5 mm cortical screws in human femur, 1b – 4.5 mm cortical screws in human tibia; Mears et al, A – 90° past contact of the screw head on the plate; B – 180° past contact of the screw head on the plate; C – two-fingers tight; D – 1.4 Nm; Stoesz et al, high density (0.32 g/cm3), medium density (0.16 g/cm3), low density (0.08 g/cm3). #Ratio estimated based on provided data, though not explicitly stated by authors.
Fig. 3
Fig. 3
Number of surgeons and the number of screws each inserted within each part of each study (12 studies reviewed in this manuscript, 48 experiments in total), with the latter displayed logarithmically. Blue markers indicate in vitro studies, red marker for the sole in vivo study. High/low surgeon and screw number quadrants created based on more or less than 30 surgeons and more or less than 10 screws inserted by each.
See this image and copyright information in PMC

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