total hip arthroplasty

Gait biomechanics after total hip arthroplasty: using statistical parametric mapping to identify differences between various surgical approaches

Biomechanical studies have tried to assess the impact of the surgical approach on gait characteristics and recovery after total hip arthroplasty (THA). Some studies which used discrete analyses have shown that some surgical approaches provide better hip joint function after one year post-surgery, but several studies did not find any differences. The goal of this study was to compare hip biomechanics during gait using statistical parametric mapping (SPM) in patients who underwent THA with either a lateral (LAT), anterior (ANT), or posterior (POS) approach. Forty-five patients underwent unilateral THA with either a LAT, ANT, or approach, and were compared with 15 healthy controls (CTRL). All patients underwent biomechanical gait analysis approximately 9 months following surgery. Hip biomechanics were compared between groups throughout the entire gait cycle using a One-Way ANOVA SPM. Alpha was set to 0.05 and Bonferroni post hoc comparisons were completed. The POS group had a significantly lower hip flexion moment just prior to toe-off compared to the ANT and CTRL groups. The ANT group had significantly lower hip abduction moment for most of the stance phase compared to the LAT and CTRL groups. The POS group had a significantly lower hip abduction moment compared to the LAT and CTRL groups. These findings tend to contradict existing literature. Future studies should complete both pre- and post-operative assessments with a larger cohort in each group, as well as standardize the implants as much as possible to determine if observed differences are due to the approach and no other factors.
Listed In: Biomechanics, Orthopedic Research

Can We Develop a Biomechanical Functional Score to Quantify the Joint Mechanics of THA Patients?

THA is a reliable method to improve the quality of life in osteoarthritis patients. However, it is still unclear whether it would lead to improved functional mobility. The purpose was to develop a biomechanical functional score to quantify the joint mechanics of THA patients compared to healthy participants (CTRL). Twenty-four THA patients and 12 CTRL (age-, sex-, and BMI-matched) participants were recruited and underwent motion analysis for different ADLs tasks prior and nine months after THA. Three-dimensional joint kinematics and ground reaction forces were collected and five kinematic and six kinetic variables were included in the analysis. The normalized root-mean-square-deviation (nRMSD) was calculated between the THA and the CTRL groups for both pre- and post-op conditions: nRMSD= √((∑_(t=1)^n(x_(1,t)- y_(1,t))^2)/n)⁄(x_max-x_min). Kinematics and kinetics improvement scores (KMIS and KNIS) were calculated to estimate pre/post-op differences: KMIS=∑_(i=1)^n〖〖(KM〗_(pre/ctrl i)-〖KM〗_(post/ctrl i))〗; KNIS=∑_(i=1)^n〖〖(KN〗_(pre/ctrl i)- 〖KN〗_(post/ctrl i))〗. THA patients experienced post-op improvements, with kinetics variables closely resembling the CTRLs, especially on hip and knee power production. Total improvement scores showed that THA experienced greater improvements during a squat task and this can be a practical approach to evaluate the change in biomechanical function and highlight small improvements that may go unnoticed with traditional statistical analysis.
Listed In: Biomechanics, Orthopedic Research

Ground Reaction Force Symmetry during Sitting and Standing Tasks after a Dual Mobility or Conventional Cup Total Hip Arthroplasty

Dual-mobility (DM) bearing implants reduce the incidence of dislocation following total hip arthroplasty (THA) also it increases hip stability and range of motion (ROM). However, it is unclear whether the improved ROM will lead to better mechanical symmetry. Ground reaction forces (GRF) analysis would help to understand joint compensatory effects and symmetry in THA patients. The purpose was to compare GRF symmetry between the operated and non-operated limbs in THA patients, of either DM or conventional-cup (CC) implant, during standing and sitting tasks. Twenty-four patients and 10 control participants (5M/5F; 62±10 years; 26±4 kg/m2) were recruited and underwent motion analysis before and nine months after THA. Patients were randomly assigned to either a DM (8M/4F; 63±5 years; 28±3 kg/m2) or CC (9M/3F; 62±5 years; 28±5 kg/m2) cementless replacement. Participants performed five sit-to-stand and stand-to-sit trials, with a bench adjusted to their knee heights and each foot on an individual force plate, with motion capture and GRF data been collected. Control group demonstrated standing (0.4±1.6%) and sitting (1.2±1.6%) symmetry. During sit-to-stand, DM group reduced its SI from pre- (5.5±1.6%) to post-op (1.2±1.9%, p=0.09), while the CC group showed a significant improvement (from 8.7±2.1% to 1.5±1.4%, p=0.02). For stand-to-sit, DM group reduced its SI (from 3.3±2.2% to 0.5±1.7%) while the CC group again had a significant improvement (from 8.2±2.1% to 1.2±1.1%, p=0.02). Larger improvements in symmetry were noticed for both groups during trunk flexion when standing; and for CC group during trunk extension when sitting. After surgery, patients with either implant reached SI inside the margin of 1.5 standard deviation from the CTRL (p>0.05). Statistical significance on paired condition was only observed on CC group due to its high pre-op score; however, both surgical groups showed an improved symmetry after THA.
Listed In: Biomechanics, Orthopedic Research