## 3 Results  
When measuring the resistance of the Spinelock screw, the CLIPS method returned the highest median and inter-quartile range (2.302 (0.576)), followed by the WRAP (2.199 (0.184)), PROBE (1.899 (0.198)) and CAPSULE (1.502 (0.096)) methods. During the resistance  
Figure 3: Illustration of the coupling methods applied to measure the voltage across the pedicle screw with the use of (**a**) multimeter probes, (**b**) alligator clips, (**c**) wrapped wires and (**d**) encapsulated wires within a thermo-retractable sleeve. measurement of the Spinecall screw, CLIPS (2.302 (0.691)) also presented the highest electrical resistance and CAPSULE (1.150 (0.327)) the lowest. However, for this screw, the second and third highest resistances were recorded with PROBE (1.702 (0.202)) and WRAP (1.606 (0.222)), respectively. The measured voltage, current, calculated electrical resistance and resistivity for each coupling method and pedicle screw are presented in Table 1.  
Statistically significant differences were found between measuring methods on the Spinelock (\(\chi^{2}(3)=145.570\), \(p<0.001\)) and Spinecall (\(\chi^{2}(3)=141.367\), \(p<0.001\)) screws, both in terms of resistance and resistivity. The results from the sequential Mann-Whitney tests comparing the different coupling methods for each pedicle screw are depicted in Table 2. Since the statistical results from the electrical resistance and resistivity were the same, a single table is presented. Statistically significant differences were found between all coupling methods (\(p<0.001\)) but not between CLIPS and WRAP (\(p=0.882\)) on the Spinelock screw. In both screws, the larger effect sizes were observed when comparing the CAPSULE with any other method. In the Spinelock screw, this occurs when comparing CAPSULE with WRAP (\(r=0.863\)), CLIPS (\(r=0.863\)) and PROBE (\(r=0.827\)), while the larger effect sizes occurred between CAPSULE and CLIPS (\(r=0.855\)), PROBE (\(r=0.833\)) and WRAP (\(r=0.800\)) for the Spinecall screw. When comparing the resistivity of each pedicle screw, measured with the same method (i.e., Spinelock CLIPS vs. Spinecall CLIPS), differences are found between screws, as depicted in Table 3. The only exception is found when comparing the resistivity obtained \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Spinelock Screw**} & \multicolumn{4}{c}{**Spinecall Screw**} \\ \cline{2-9}
**Method** & **Voltage (\(\mu\)V)** & **Current (mA)** & **Resistance (\(\mu\)\(\Omega\)m)** & **Resistivity (\(\mu\)V)** & **Voltage (\(\mu\)\(\Omega\)m)** & **Current (mA)** & **Resistance (\(\mu\)\(\Omega\)m)** & **Resistivity (\(\mu\)\(\Omega\)m)** \\ \hline PROBE & 19.0 & 10.00 & 1.899 & 3.020 & 17.0 & 9.99 & 1.702 & 3.341 \\  & (2.0) & (0.01) & (0.198) & (0.315) & (2.0) & (0.01) & (0.202) & (0.397) \\ CLIPS & 23.0 & 10.01 & 2.302 & 3.662 & 23.0 & 9.99 & 2.302 & 4.521 \\  & (6.0) & (0.02) & (0.576) & (0.917) & (7.0) & (0.12) & (0.691) & (1.356) \\ WRAP & 21.0 & 9.99 & 2.199 & 3.497 & 16.0 & 10.03 & 1.606 & 3.154 \\  & (2.0) & (0.04) & (0.184) & (0.291) & (2.3) & (0.20) & (0.222) & (0.437) \\ CAPSULE & 15.0 & 10.00 & 1.502 & 2.388 & 11.5 & 10.00 & 1.150 & 2.258 \\  & (1.0) & (0.02) & (0.096) & (0.152) & (3.3) & (0.02) & (0.327) & (0.642) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Values of voltage and current measured with each coupling method and the corresponding calculated electrical resistance and resistivity, presented as median (interquartile range).