## 4 Discussion  
The incongruence between the femoral neck and the acetabular rim in the case of a FAI is provoked in maximal flexion, adduction and internal rotation by the FADIR test. The purpose of the present study was to analyze the impact of a CAM deformity on the gait cycle of patients with an OA of the hip. A gait analysis was performed in fifty-five patients before THA and were followed up three, six and 12 months postoperatively to determine if preoperative differences existed, and if these adjusted over the time. \begin{table}
\begin{tabular}{c c c c c} \hline
**Toe off** & \(-\)**cam** & **+cam** & **Difference \(-\)/+cam** & **95\% CI** \\ \hline Hip sag. preop. & \(2.2\pm 7.8\) & \(2.1\pm 10.2\) & \(0.1\) & \(-5.1;5.2\) \\ Hip sag. 12 M FU & \(-3.2\pm 9.1\) & \(-6.3\pm 8.0\) & \(3.1\) & \(-1.6;7.7\) \\ Difference preop. \(-\) 12 M & \(-5.4\pm 10.3\) & \(-8.4\pm 8.8\) & \(3.0\) & \(-2.2;8.2\) \\ Hip front. preop. & \(-0.7\pm 2.9\) & \(-1.1\pm 4.5\) & \(0.4\) & \(-1.8;2.5\) \\ Hip front. 12 M FU & \(-1.2\pm 4.1\) & \(-1.1\pm 2.8\) & \(0.1\) & \(-2.0;1.7\) \\ Difference preop. \(-\) 12 M & \(-0.5\pm 3.8\) & \(0.02\pm 4.5\) & \(0.51\) & \(-2.8;1.8\) \\ Hip trans. preop. & \(3.0\pm 17.4\) & \(2.1\pm 15.7\) & \(0.9\) & \(-8.2;9.9\) \\ Hip trans. 12 M FU & \(-4.0\pm 14.7\) & \(-8.2\pm 10.7\) & \(4.2\) & \(-2.8;11.0\) \\ Difference preop. \(-\) 12 M & \(-7.0\pm 18.5\) & \(-10.3\pm 18.0\) & \(3.3\) & \(-6.8;13.3\) \\ \hline \end{tabular}
\end{table} 
Table 3: Mean values and standard deviations at the toe off of the treated hip before and 12 months after surgery, as well as the difference between both time points depending on the presence of a cam deformity. No statistically significant differences were found. The mean differences between the hip angles in patients with and without a cam deformity ranged between 0.1-4.2\({}^{\circ}\). Figure 3: _Cont_. Due to the great volume of collected parameters, the focus was set to the hip position at heel strike and toe off. At the heel strike, the hip position was tendentially in all planes inferior in the +cam group (\(p>0.05\)), resulting in a flexion about \(30.5^{\circ}\), an internal rotation about \(10.8^{\circ}\) and a neutral position in frontal plane. At the last examination the hip angles adjusted to \(33.5^{\circ}\) flexion, \(0.5^{\circ}\) adduction and \(15.8\) internal rotation in presence of a CAM. The differences at the toe off between patients with or without an FAI type CAM were not significant for the hip position (\(p>0.05\)). Preoperatively, the hips showed a comparable position in sagittal and frontal planes with a tendentially inferior internal rotation in the presence of a CAM deformity (\(p>0.05\)). At the examination 12 months after THA, the angles in the frontal plane remained comparable, while the mean values in the sagittal plane tended towards an extension and external rotation in the +cam group (\(p>0.05\)). Overall, the results of the hip position while walking with a CAM deformity showed no statistical significance, and the differences were too small to determine relevant clinical consequence. However, the observed tendencies might hint at an impact of an FAI on gait pattern with limited flexion and internal rotation, the trigger movements for the bony conflict of this hip disease. Our results indicate that patients who suffer from an FAI may avoid provoking movements while walking. Comparable findings were presented in previous studies. [PERSON] et al. compared 20 asymptomatic patients with 20 patients suffering from FAI. Both groups showed comparable ranges of angles while walking. The authors estimated differences in testing these groups in impingement position and provoking maneuvers [22]. Further, [PERSON] et al. observed minimal impairments in gait pattern with an unclear impact on the patient's symptoms or the hip function. The authors performed a three-dimensional gait analysis with 15 symptomatic FAI patients before arthroscopic treatment compared to 15 symptoms-free patients [23].