Evaluation of the reproducibility of preoperative three-dimensional computed tomography planning for posterolateral approach total hip arthroplasty

Accuracy of femoral component anteversion in robotic total hip arthroplasty

Aims

Femoral component anteversion is an important factor in the success of total hip arthroplasty (THA). This retrospective study aimed to investigate the accuracy of femoral component anteversion with the Mako THA system and software using the Exeter cemented femoral component, compared to the Accolade II cementless femoral component.

Methods

We reviewed the data of 30 hips from 24 patients who underwent THA using the posterior approach with Exeter femoral components, and 30 hips from 24 patients with Accolade II components. Both groups did not differ significantly in age, sex, BMI, bone quality, or disease. Two weeks postoperatively, CT images were obtained to measure acetabular and femoral component anteversion.

Results

The mean difference in femoral component anteversion between intraoperative and postoperative CT measurements (system accuracy of component anteversion) was 0.8° (SD 1.8°) in the Exeter group and 2.1° (SD 2.3°) in the Accolade II group, respectively (p = 0.020). The mean difference in anteversion between the plan and the postoperative CT measurements (clinical accuracy of femoral component anteversion) was 1.2° (SD 3.6°) in the Exeter group, and 4.2° (SD 3.9°) in the Accolade II group (p = 0.003). No significant differences were found in acetabular component inclination and anteversion; however, the clinical accuracy of combined anteversion was significantly better in the Exeter group (0.6° (SD 3.9°)) than the Accolade II group (3.6° (SD 4.1°)).

Conclusion

The Mako THA system and software helps surgeons control the femoral component anteversion to achieve the target angle of insertion. The Exeter femoral component, inserted using Mako THA system, showed greater precision for femoral component and combined component anteversion than the Accolade II component.

Rigid fixation of pelvic tracker essential for accurate cup placement in CT-based navigation total hip arthroplasty

Research is lacking on the effect of intraoperative pelvic tracker displacement relative to the pelvis on cup orientation accuracy in computed tomography (CT)-based navigation (CTN) or multivariable analysis to detect factors associated with CTN accuracy. Here, we asked: (1) how pelvic tracker displacement influences the CTN accuracy of cup orientation in total hip arthroplasty (THA)? and (2) what factors are associated with CTN accuracy on multivariable analysis? Regarding cup orientation in 446 THA procedures using CTN, we evaluated clinical error defined as the difference between postoperative measurement and preoperative planning and measurement error defined as the difference between postoperative and intraoperative measurements. Multivariable regression analyses detected the associated factors. Subjects with an intraoperative tracker displacement of < 2 mm were classified in the verified group. Mean absolute clinical and measurement errors were < 1.5° in the verified group, whereas the measurement error of 2.6° for cup inclination and 1.3° for anteversion was larger in the non-verified versus verified group. Tracker displacement and screw fixation were associated with larger clinical errors, while tracker displacement and surgeon inexperience were associated with larger measurement errors. Clinical and measurement accuracies were high for CTN cup placement with rigid pelvic tracker fixation.