Optimal design and biomechanical analysis of sandwich composite metal locking screws for far cortical locking constructs

Engagement and Stress Concentration Evaluation of a Novel Two-Part Compression Screw: A Preliminary Finite Element Analysis

Background/Objectives: This novel compression screw design offers potential benefits due to its two-part structure and can be used for various bone types, much like a conventional single-piece compression screw. However, full engagement may not always occur after final compression in clinical practice. This study aimed to verify the hypothesized optimal mechanical strength when the two parts are nearly fully combined and to determine a recommended engagement range based on stress distribution and concentration using finite element analysis. Methods: Ten models representing different combinations of the two screw parts (ranging from 10% to 100% of the engagement length, at 10% intervals) were simulated to determine the acceptable engagement percentage. Pull-out and bending load simulations were performed using finite element models. Extreme clinical loading conditions were simulated, including 1000 N pull-out forces and a 1 Nm bending moment at the screw head. Results: Finite element analysis revealed two stress concentration points. The pull-out load simulation showed that combinations with 100% engagement merged the two stress concentrations into one without force superposition, while combinations with less than 30% engagement should be avoided. In the bending load simulation, higher stress was observed for combinations with less than 90% engagement. A lower level of engagement increases the bending moment, which might be the major factor affecting the von Mises stress. Conclusions: Surgeons should be instructed on how to use the screw correctly and select the most appropriate screw size or length for the two parts to achieve an effective combination. Excessive bending or pull-out forces, or improper use with poor combinations, may cause the middle interval to strip or the screw to break or pull out. An engagement of more than 90% is recommended, while less than 30% is considered dangerous. This study provides biomechanical insights into this novel two-part screw design and its important clinical implications.

Clinical outcome after open-wedge high tibial osteotomy: comparison of double-triangle locking compression plate (DT-LCP) and T-shaped locking compression plate (T-LCP)

BACKGROUND

The objective of this study was to compare the clinical outcomes of two internal fixation methods for high tibial osteotomy (HTO): double-triangle locking compression plate (DT-LCP) and T-shaped locking compression plate (T-LCP).

METHODS

202 adult patients in our hospital between January 2018 and December 2021 were included and followed up for at least one year: group 1(DT-LCP, 98 patients) and group 2 (T-LCP, 104 patients). Detailed information on demographics, preoperative and postoperative follow-up, surgical procedures, and complications were collected. The information of the International Knee Documentation Committee Knee Evaluation Form (IKDC), Knee Injury and Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were collected before surgery and at the last follow-up.

RESULTS

A total of 202 patients were included in the per-protocol analysis. No significant difference was found in terms of demographic data between groups, except for age and BMI. Clinically relevant improvements in knee pain were reached up to last follow-up after the operation in both groups. The mean pain scores (KOOS, WOMAC) at the final follow-up were significantly higher among group 1 compared to group 2 (P = 0.040 and P = 0.023). Furthermore, the DT-LCP internal fixation exerted more excellent effects on other symptoms, function and quality of life than T-LCP internal fixation.

CONCLUSIONS

Our study demonstrated that DT-LCP provided better clinical performance due to its implant irritant pain, compared with T-LCP. Thus, DT-LCP is a feasible alternative for the fixation of OW-HTO.