(MPE) bearing and healthy participants (Control) to provide a reference for ... either a DM or a MPE cementless total hip replacement using the Medacta system ( ...
Gait Asymmetry in Patients with a Dual Mobility Total Hip Arthroplasty: a Randomized Clinical Trial Danilo S. Catelli, MSc, Sarah Reynolds, MSc, Mario Lamontagne, PhD, Paul E. Beaule, M.D.. University of Ottawa, Ottawa, ON, Canada. Disclosures: D.S. Catelli: None. S. Reynolds: None. M. Lamontagne: 5; Medacta International. P.E. Beaule: 5; Medacta International. Introduction: Dual mobility (DM) bearings have been shown to reduce the incidence of dislocation and as such are being increasingly used for the treatment of hip instability in both the primary and revision situation. [1-3]. One of the key reasons for the use of DM bearings is their capacity to increase hip range of motion (ROM) while minimizing the risk of impingement [4]. However it is unclear whether the improved hip ROM will lead to better patients’ functional mobility. Analysis of asymmetry in joint angle during gait has been shown to be useful in highlighting potential imbalances between limbs of a patient [5] using the symmetry angle (SA), which avoids artificial inflation of results and provides a standardized scale (±100%) to interpret results [6]. The aim of this study was to compare sagittal hip angle patterns in the operated and non-operated limbs during level gait, in patients having undergone either DM bearing or a standard metal on polyethylene (MPE) bearing and healthy participants (Control) to provide a reference for symmetry values. Methods: A total of 26 patients and 12 control participants were recruited from the Orthopaedic Clinic of the Ottawa Hospital (Table 1). The patients who volunteered for the study were randomly assigned to either a DM or a MPE cementless total hip replacement using the Medacta system (Medacta International, CH). They also agreed to undergo to motion analysis before and nine months after THA. All surgeries were performed by the same surgeon using the direct anterior approach. The healthy participants were matched by age and BMI. Table 1. Summary of demographics of the recruited participants Group Pre-op (n) Post-op (n) Age (yrs) BMI (kg/m2) Sex ratio (F/M) DM
13
13
63.0 ± 5.1 28.1 ± 2.8
4/10
MPE
10
12
61.6 ± 4.6 28.2 ± 5.1
3/9
Control NA
12
61.0 ± 7.1 25.3 ± 3.8
6/6
Participants were outfitted with 45 reflective markers and performed a minimum of five trials of walking along a 4-meter walkway at a self-selected pace. Three-dimensional joint kinematics of the lower limbs was captured at 200 Hz using a ten-camera motion analysis system (Vicon MX, Oxford Metrics, UK). Kinematic data were processed in Nexus 1.8 (Vicon, Oxford Metrics, UK), by running a modified Plug-InGait model, and then exported in a custom MATLAB script (MatLab 2014a, The Mathworks, USA) to calculate groups’ averages and extract relevant kinematic variables. All trials were time-normalized
based on consecutive foot strikes, and individual averages for each participant were calculated across the five trials. Three discrete variables were measured and used in the asymmetry calculations: peak hip flexion during double support phase (ϴFlexDS), peak hip extension (ϴExt) and peak hip flexion during swing phase (ϴFlexS). The method of Zifchock et al. (2008) [6] was used to calculate the SA values for all variables: SA = (45º - arctan(Xoperated/Xnon-operated))/90º * 100%. An SA value of 0% indicates perfect symmetry, 100% indicates that the two values are equal and opposite in magnitude, while negative percentages represents a higher magnitude for the non-operated limb. Therefore, if (45º - arctan(Xoperated/Xnonoperated)) > 90º, the following equation should be substituted by: SA = (45º - arctan(Xoperated/Xnonoperated) - 180º)/90º * 100%. For the control group, the dominant and non-dominant legs were considered instead. A paired t-student test comparing pre- and post-op conditions for hip kinematic parameters and SA; and also a one-way ANOVA comparing post-ops and control were conducted for both, hip kinematic parameters and SA, with a confidence level of 95%. Results: Sagittal hip angles means are presented for each group in the pre- and post-op, as well as the control (Fig. 1).
Fig. 1. Sagittal hip angles-time normalized (foot strike to foot strike) during double support (DS), single support (SS) and swing (S) phases. The light gray shadow around the Control group indicates a ±1.5 standard deviation around that group mean. The selected discrete variables (ϴFlexDS, ϴExt, ϴFlexS) are the points where the DM and MPE groups are more than 1.5 standard deviation far away from the Control group. These measures show that the operated groups still exhibited reduced ROM compared to the controls. However, a paired comparison between the pre and post conditions showed a statistical improvement for ϴFlexDS, ϴExt, ϴFlexS in the MPE group (p-value: 0.03, 0.04, 0.04; respectively), while the DMs did not achieve a statistically significant difference (p-value: 0.18, 0.12, 0.13). Also, the analysis of variance among post-operated and control groups showed a difference for peak hip extension (p
