Does Computer-Assisted Femur First THR Improve Musculoskeletal Loading Conditions?

Abstract

We have developed a novel, computer-assisted operation method for minimal-invasive total hip replacement (THR) following the concept of “femur first/combined anteversion,” which incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position (CAS FF). The purpose of this study is to assess whether the hip joint reaction forces and patient's gait parameters are being improved by CAS FF in relation to conventional THR (CON). We enrolled 60 patients (28 CAS FF/32 CON) and invited them for gait analysis at three time points (preoperatively, postop six months, and postop 12 months). Data retrieved from gait analysis was processed using patient-specific musculoskeletal models. The target parameters were hip reaction force magnitude (hrf), symmetries, and orientation with respect to the cup. Hrf in the CAS FF group were closer to a young healthy normal. Phase-shift symmetry showed an increase in the CAS FF group. Hrf orientation in the CAS FF group was closer to optimum, though no edge or rim-loading occurred in the CON group as well. The CAS FF group showed an improved hrf orientation in an early stage and a trend to an improved long-term outcome.

Uncemented femoral stem orientation and position in total hip arthroplasty: A CT study

“…Ranawac and Maynard 34 introduced the concept of combined version and proposed a fixed value for the sum of the cup and stem version; later, Dorr et al 24 proposed an optimal zone for the combined anteversion that ranges from 25 deg to 50 deg. The option of using a femur first approach, 35‐37 where the cup is positioned relative to the stem to achieve a satisfactory combined version, should be considered. However, a satisfactory intraoperative measurement tool is needed for this purpose.…”

The impact of hip implant alignment on muscle and joint loading during dynamic activities

“…There are multiple THA surgical approaches that have been designed in order to optimize component placement and minimize the impact of surgical variability. Weber et al, (2015) used musculoskeletal modeling to investigate how hip JCFs during gait compared between a group of THA patients who had undergone a novel computer-assisted femur first/combined anteversion approach versus patients who had undergone traditional THA. They found similar baseline hip JCFs to those of our patients throughout the gait cycle and noted that hip JCFs from the computer-assisted femur first/combined anteversion approach were closer to young healthy individuals than those from the traditional THA group.…”

Gait six month and one-year after computer assisted Femur First THR vs. conventional THR. Results of a patient- and observer- blinded randomized controlled trial

“…The minimum clinically important improvement can be seen between preoperative and six month postoperative walking pattern for both groups, yet the persistence postoperative differences in walking pattern seem clinically irrelevant. When taking computations of the patient-specific biomechanics into account, significant differences between the forces acting in the hip joint can be seen, yet the scope of this work is the comparison of postoperative walking pattern in terms of kinematics [29]. We had to reject our specific hypothesis because: (i) CAS FF does not lead to an improved dimensionless walking speed compared to conventional THR, (ii) there was no significant difference between CAS FF and conventional THR in terms of active range of motion in magnitude and symmetry (iii) we realized a trend for an improved hip flexion angle for the CAS FF group compared to conventional THR which did not reach statistical significance.…”

“…Third, gait is not a critical motion. Impingement or dislocation is most likely to occur during critical motion such as a squat or sit to stand maneuvers [30,31,28,29]. It is however unethical to invite patients for experiments that might obviously result in failure of the implanted joint.…”