Comparative Evaluation of Drill-Free and Self-Tapping Titanium Miniscrews for Semi-Rigid Internal Fixation in Maxillofacial Trauma

Development and validation of a specialized system for self-tapping medical bone screw testing

A specialized system for accurate self-tapping medical bone screw testing is developed, fully meeting the requirements of ASTM F543-A4 (YY/T 1505-2016). The onset of self-tap is identified automatically according to a change in the slope of the torque curve. Precise load control is applied to determine the self-tapping force accurately. A simple mechanical platform is embedded to ensure the automatic axial alignment of a tested screw with the pilot hole in a test block. In addition, comparative experiments are conducted on different self-tapping screws to verify the system's effectiveness. By the automatic identification and alignment method, both torque curves and axial force curves for each screw exhibit significant consistency. The self-tapping time point derived from the torque curve agrees well with the turning point of the axial displacement curve. The determined self-tapping forces' mean values and standard deviations are both small, which are proved to be effective and accurate in the insertion tests. This work contributes to improving the standard test method for accurate determination of the self-tapping performance of medical bone screws.

Inanimate surface contamination of SARS-CoV-2 during midfacial fracture repair in asymptomatic COVID-19 patients

Purposes

To evaluate inanimate surface contamination of SARS-CoV-2 during midfacial fracture repair (MFR) and to identify relevant aggregating factors.

Methods

Using a prospective non-randomised comparative study design, we enrolled a cohort of asymptomatic COVID-19 patients undergoing MFR. The predictor variables were osteofixation system (conventional titanium plates [CTiP] vs. ultrasound-assisted resorbable plates [USaRP]). The main outcomes were the presence of SARS-CoV-2 on four different surfaces. Other study variables were categorised into demographic, anatomical, and operative. Descriptive, bi- and multivariate statistics were computed.

Results

The sample consisted of 11 patients (27.3% females, 63.6% right side, 72.7% displaced fractures) with a mean age of 52.7 ± 20.1 years (range, 19–85). Viral spread was, on average, 1.9 ± 0.4 m. from the operative field, including most oral and orbital retractors’ tips (81.8% and 72.7%) and no virus was found at 3 m from the operative field, but no significant difference was found between 2 osteofixation types. On binary adjustments, significantly broader contamination was linked to centrolateral MFR (P = 0.034; 95% confidence interval [CI], 0.05 to 1.02), and displaced MFR > 45 min (P = 0.022; 95% CI, 0.1 to 1.03).

Conclusions

USaRP, albeit presumably heavily aerosol-producing, cause similar SARS-CoV-2 distribution to CTiP. Non-surgical operating room (OR) staff should stay ≥ 3 m from the operative field, if the patient is SARS-CoV-2-positive. Enoral and orbital instruments are a potential virus source, especially during displaced MFR > 45 min and/or centrolateral MFR, emphasising an importance of appropriate patient screening and OR organisation.