The Effect of Hamatum Curvature Angle on Carpal Tunnel Volumetry: A Mathematical Simulation Model.

In carpal tunnel volume measurements, the angle of the hamatum curvature is not considered a variable, and its effect on carpal tunnel volume has not been investigated. We hypothesize that a change in the anatomical angle of the hamatum curvature changes the carpal tunnel volume. To prove our hypothesis, we used a mathematical simulation model considering the carpal tunnel as a truncated cone. We reviewed the wrist CT scans of 91 adults (>18 years of age), including 51 men and 40 women. We measured the angle of the hamatum curvature in the CT scans. We measured cross-sectional areas at the outlet of the carpal tunnel at the level of the trapezium and hook of hamate (r1) and at the inlet at the level of the scaphoid and pisiform (r2) and the length (h) of the carpal tunnel. We attempted to calculate the effect of 2 degree by 2-degree changes in the angle of the hamatum curvature between the angles of 98° and 140° on the carpal tunnel volume. The mean angle of the hook of hamatum of the subjects was 122.55° ± 8.20° (range, 97.20° - 139.31°). No suitable cutoff point was found for the angle values. There was no difference between the gender groups according to the angle value. The data clearly show that there is a high correlation between carpal tunnel volume and the angle of hamatum curvature. The results of our study emphasize the importance of taking into account the anatomical features of the hamatum bone, especially the angle of curvature, which may play a predisposing role in idiopathic carpal tunnel syndrome.

Laser-Induced Microgrooves Improve the Mechanical Responses of Cemented Implant Systems.

The impact of a laser-induced microgroove (LIM) architecture on mechanical responses of two cemented implant systems was evaluated. One system consisted of two aluminum alloy rods bonded end-to-end by polymethylmethacrylate cement. The second system consisted of a custom-made, aluminum tibial tray (TT) cemented in an artificial canine tibia. Control specimens for each system were polished smooth at the cement interface. For LIM samples in the rod system, microgrooves were engraved (100 µm depth, 200 µm width, 500 µm spacing) on the apposing surface of one of the two rods. For TT system testing, LIM engraving (100 µm spacing) was confined to the underside and keel of the tray. Morphological analysis of processed implant surfaces revealed success in laser microgrooving procedures. For cemented rods tested under static tension, load to failure was greater for LIM samples (279.0 ± 14.9 N vs. 126.5 ± 4.5 N). Neither non-grooved nor grooved TT samples failed under cyclic compression testing (100,000 cycles at 1 Hz). Compared with control specimens, LIM TT constructs exhibited higher load to failure under static compression and higher strain at the bone interface under cyclic compression. Laser-induced microgrooving has the potential to improve the performance of cemented orthopedic implants.

Understanding the causes behind coracoid graft osteolysis in latarjet procedure (finite element analysis and comparison of three fixation methods).

BACKGROUND: Latarjet is one of the most common surgical procedure performed on patients with shoulder instability with osseous defects, some complications include coracoid bone graft osteolysis, osteoarthritis, graft detachment, and malpositioning were previously reported. Several studies investigated potential causes of graft osteolysis but still, it remains a crucial area of investigation. We aim to use finite element analysis to examine the potential correlations between three modes of fixation methods used in the Latarjet procedure (screw, wedge plate, and endobutton), and the coracoid graft osteolysis. HYPOTHESIS: Finite element analysis tested the hypothesis that there is a linear relationship between the compression stress on graft which was generated by fixation methods used in the latarjet and the coracoid graft osteolysis. MATERIAL AND METHODS: Boundary conditions and inhomogeneous material properties were carefully assigned within the material of the scapula and coracoid interface. For the screw and wedge plate fixations, an applied torque in the range of 1-1.5Nm was used to characterize the surgeon's insertion torque during the surgical operation, while a 100N compressive force was selected for the endobutton fixation. RESULTS: Relatively lesser stress magnitudes were observed with endobutton fixation method rather than screw and the wedge plate fixation. Statistical analyses revealed significant differences between the groups (p<0.05). DISCUSSION: Excessive compressive stresses within the coracoid graft regions may be responsible for osteolysis due to negative effects over biological factors such as blood flow. Our study emphasizes the importance of taking into account the fixation method while performing the Latarjet procedure. We concluded that the mode of fixation used within the Latarjet procedure has a correlation on the coracoid graft osteolysis. LEVEL OF EVIDENCE: I.