Failure analysis of a locking compression plate with asymmetric holes and polyaxial screws

Zhang, Ning-Ze; Liu, Bolun; Luan, Yichao; Zhang, Min; Cheng, Cheng‐Kung

doi:10.1016/j.jmbbm.2022.105645

Cited by 2 publications

(1 citation statement)

References 44 publications

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“…On the other hand, Hanshen et al indicated improved functional and radiological outcomes in patients treated with Zimmer non-contact bridging polyaxial plate (NCB) [ 22 ]. Zhang et al hypothesized on the basis of the finite element surgical model, that inserting the proximal polyaxial screws at -10° in the transverse plane may reduce Zimmer NCB implant failure [ 23 ]. It is worth mentioning that, in particular, in the Zimmer NCB, the locking cap placed over the screw head provides the friction fit, creating fixed angle construct [ 5 ].…”

Section: Discussionmentioning

confidence: 99%

Effect of screw angulation and multiple insertions on load-to-failure of polyaxial locking system

Glowacki,

Bartkowiak,

Paczos

et al. 2023

PLoS ONE

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Purpose Polyaxial locking plates rely on the alignment between the thread-to-thread connections of the screw head and the plate hole. These implants have provided substantial support for surgeons. In particular, extended screw positioning have proven to be beneficial in the fixation of challenging fractures. This study aimed to investigate the mechanical properties of ChM 5.0 ChLP polyaxial screws inserted in off-axis trajectories, including multiple insertions and to correlate these parameters with the screw head and the plate hole thread-to-thread engagement. Methods Polyaxial locking screws were inserted into the plates at various angles (0°,10°,15°, -15° off-axis). Multiple time inserted screws were placed firstly at 15°, then 0° and finally -15° off-axis in the same plate hole. A microCT scan of the plate-hole and screw-head interface was conducted before destructive tests. Representative screws from each group were also examined by Scanning Electron Microscope. Results The standard insertion at 0° sustained the greatest maximum bending strength without relocation in the screw hole. Screws inserted at 10° and 15° (one time) showed a significant reduction in load-to-failure of up to 36% and 55%, (p = 0.001) (p = 0.001) respectively. Screws inserted at -15° after a maximum of three multiple insertions with angle shift, showed a total reduction in force of up to 70% (p = 0.001). A microCT analysis of thread engagement showed significant correlations. However, the results obtained for multiple insertions were highly variable. Conclusions ChM 5.0 ChLP polyaxial locking system has valuable properties that foster fracture fixation, providing various surgical options. Nevertheless, the freedom of off-axis placement and multiple insertions of the screws comes at the price of reduced force. When possible surgeons should minimize the angles of insertions.

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Section: Discussionmentioning

confidence: 99%