## 3 Results
### Results--Operating Times  
Figure 5 shows the arithmetic means of incision-suture times over the complete observation period and the respective median times, with interquartile range. For operations without navigation, the overall mean time is 80 min, with a standard deviation of 45.6 min. By contrast, operations performed with the aid of a navigation device are a mean of 4.5 min shorter, hence, lasting 75.5 min, with a standard deviation of 40.6 min. The median operating times are additionally calculated. The median time is 69 min for navigated operations and 72 min for non-navigated surgery. Table 6 lists the number of operations according to each rank of physician (JNR: Junior Doctor, SP: Specialist, CON: Consultant, HD: Head of Department), the mean operating time in terms of the incision-suture times, the median duration of operations, and the standard deviation. Figure 4: Frequency distribution incision–suture time (IST), both absolute and as a percentage. Figure 5: Mean durations over 5 years, with standard deviation (SD) and interquartile range (IQR). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Without Navigation**} & \multicolumn{4}{c}{**With Navigation**} \\ \hline  & \multirow{2}{*}{**Number**} & \multicolumn{2}{c}{**Mean**} & \multirow{2}{*}{\ \begin{tabular}{c} **Median** \\ **(Min)** \\ \end{tabular}  } & \multirow{2}{*}{**SD**} & \multirow{2}{*}{**Number**} & \multirow{2}{*}{ \begin{tabular}{c} **Mean** \\ **(Min)** \\ \end{tabular}  } & \multirow{2}{*}{**Median**} & \multirow{2}{*}{**SD**} \\  & & & & & & & **Time (Min)** \\ \hline
**Junior Doctors** & **136** & **92.96** & **87.00** & **40.81** & **34** & **121.21** & **110.00** & **49.20** \\ \hline JNR1 & 8 & 84.25 & 87 & 18.58 & 3 & 89.33 & 94 & 9.87 \\ \hline JNR2 & 4 & 80.75 & 102 & 45.19 & & & & \\ \hline JNR3 & 8 & 78.75 & 72 & 31.52 & 6 & 162.17 & 141 & 69.36 \\ \hline JNR4 & 2 & 76.00 & 76 & 46.67 & & & & \\ \hline JNR5 & 19 & 101.05 & 96 & 37.20 & 1 & 110.00 & 100 & \\ \hline JNR6 & 4 & 84.25 & 91.5 & 37.99 & 1 & 57.00 & 57 & \\ \hline JNR7 & 3 & 94.67 & 90 & 8.08 & & & & \\ \hline JNR8 & 1 & 67.00 & 67 & & & & & \\ \hline JNR9 & 5 & 86.40 & 76 & 49.23 & & & & \\ \hline JNR10 & 6 & 118.67 & 111 & 61.05 & & & & \\ \hline JNR11 & 7 & 78.86 & 78 & 44.08 & 2 & 88.50 & 88.5 & 38.89 \\ \hline JNR12 & 4 & 82.50 & 104 & 33.04 & 2 & 100.50 & 100.5 & 4.95 \\ \hline JNR13 & 3 & 99.33 & 80 & 38.80 & & & & \\ \hline JNR14 & 5 & 72.80 & 61 & 35.44 & 1 & 206.00 & 206 & \\ \hline JNR15 & 9 & 95.00 & 87.5 & 38.88 & & & & \\ \hline JNR16 & 1 & 46.00 & 46 & & & & \\ \hline JNR17 & 13 & 102.92 & 116 & 46.65 & 14 & 129.64 & 117.5 & 34.49 \\ \hline JNR18 & 15 & 98.00 & 93.5 & 43.04 & 2 & 83.00 & 83 & 11.31 \\ \hline JNR19 & 4 & 144.00 & 125 & 62.42 & & & & \\ \hline JNR20 & 2 & 117.00 & 117 & 38.18 & 1 & 38.00 & 38 & \\ \hline JNR21 & 8 & 70.38 & 58 & 33.33 & 1 & 110.00 & 110 & \\ \hline JNR22 & 5 & 97.20 & 97 & 44.72 & & & & \\ \hline
**Specialists** & **179** & **99.05** & **93.00** & **50.52** & **33** & **113.12** & **114.00** & **42.40** \\ \hline SP1 & 26 & 101.46 & 107 & 46.54 & 5 & 132.60 & 168 & 60.64 \\ \hline SP2 & 34 & 114.32 & 105 & 56.49 & 7 & 127.71 & 122 & 36.07 \\ \hline SP3 & 28 & 111.86 & 113 & 60.05 & 14 & 106.07 & 112 & 34.10 \\ \hline SP4 & 18 & 65.78 & 77 & 21.96 & & & \\ \hline SP5 & 18 & 123.11 & 131 & 43.53 & 1 & 175.00 & 161.5 & \\ \hline SP6 & 39 & **77.44** & **74** & 43.43 & 2 & 59.50 & 59.5 & 38.89 \\ \hline SP7 & 16 & 103.31 & 101.5 & 39.87 & 4 & 99.25 & 102 & 36.34 \\ \hline
**Consultants** & **363** & **76.01** & **67.00** & **42.52** & **79** & 75.37 & **72.00** & **34.70** \\ \hline CON1 & 11 & 84.55 & 77 & 28.57 & 1 & 40.00 & 40 & \\ \hline CON2 & 34 & 68.76 & 59.5 & 36.40 & 2 & 75.00 & 75 & 22.63 \\ \hline CON3 & 28 & 103.61 & 103 & 45.19 & 1 & 81.00 Figure 6 shows the mean durations that are characterized by high standard deviation. For this reason, the median values (Figure 7) are used for the interpretations.